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The Doctor Click is a rhythm controller manufactured by the American company Garfield Electronics. [ 1 ] It was released in 1982. [ 2 ]
In the pre- MIDI era, the Doctor Click enabled various different synthesizers and drum machines to communicate with each other.
It features two independent channels. [ 3 ]
There are also footswitch inputs for Play, Reset and Enter. [ 1 ]
The unit features modulation control for VCO , VCF and VCA sections of synthesizers.
The unit is constructed in a metal case, uses microswitches and a screen for reading the tempo. [ 4 ]
You can step program the device by selecting Timebase 12 and use the Step button to enter the step count for each note.
This article relating to musical instruments is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Garfield_Electronics_Doctor_Click |
The Garfield Thomas Water Tunnel is one of the U.S. Navy 's principal experimental hydrodynamic research facilities and is operated by the Penn State Applied Research Laboratory . [ 2 ] The facility was completed and entered operation in 1949. [ 2 ] The facility is named after Lieutenant W. Garfield Thomas Jr. , a Penn State journalism graduate who was killed in World War II . For a long time, the Garfield Thomas Water Tunnel was the largest circulating water tunnel in the world. [ 1 ] It has been declared a historic mechanical engineering landmark by the American Society of Mechanical Engineers . [ 3 ]
Today, in addition to many of its Navy projects, the facility tunnel-based research has expanded into pumps for the Space Shuttle , advanced propulsors for ships, heating and cooling systems, artificial heart valves , vacuum cleaner fans, and other pump and propulsor related products. [ 4 ] [ 5 ]
After the end of World War II , the US military started investing heavily in higher education nationwide. At the same time, Harvard terminated its Underwater Sound Laboratory (USL), which invented the first acoustical homing torpedo ( FIDO ); [ 1 ] consequently Penn State hired Eric Walker , USL's assistant director to head its electrical engineering department, and the Navy transferred USL's torpedo division to Penn State - where it became the Ordnance Research Laboratory (ORL). [ 6 ] The ORL eventually became the Applied Research Laboratory.
The Garfield Thomas Water Tunnel was built at Penn State in cooperation with ORL by the ARL for further torpedo research. Construction completed on October 7, 1949, and began operating six months later. [ 1 ] Since then, the facility has expanded into viscosity, sound, wave, and wind research.
In 1992, the facility underwent a complete overhaul. [ 4 ]
The facility consists of a number of closed circuit, closed jet and open jet facilities. [ 7 ]
The facility operates four water tunnels. [ 8 ]
The Garfield Thomas Water Tunnel is the facility's largest water tunnel. [ 7 ] The 100 feet long, [ 5 ] 32 feet high, [ 5 ] 100,000 [ 1 ] gallons tunnel is a closed-circuit, closed-jet. The system is powered by 1,491 kW (2,000-hp) pump, with a 4-blade adjustable pitch impeller and can produce a maximum water velocity of 18.29 m/s (40.91 mph). The system is capable of producing pressures between 413.7 and 20.7 kPa.
The tunnel is equipped with an array of instruments including: Propeller dynamometers, Five-hole pressure probe, Pitot probes , lasers, pressure sensors, hydrophones , planar motion mechanism (PMM), force balances, accelerometers , and acoustics arrays . [ 7 ]
The facility operates two additional smaller water tunnels with diameters of 12 inches and 6 inches. Both are closed-circuit, closed-jet. The 12-incher is a 150 horsepower (111.8 kW) system capable of producing maximum water velocity of 24.38 m/s (54.53 mph). The 6-incher is a 25 hp (18.64 kW) system that can deliver a max velocity of 21.34 m/s (47.74 mph).
Both tunnels are equipped with lasers, pressure sensors, pressure transducers , and hydrophones
The facility also has a 1.5 inch closed-circuit, closed-jet cavitation tunnel capable of producing a maximum velocity of 83.8 m/s (187 mph). The stainless steel, 75 hp (55.9 kW) tunnel supports pressures as high as 41.4 kPa and temperatures of 16 °C to 176 °C.
In addition to the water tunnels, the facility operates an array of wind tunnels, glycerin tunnels, and anechoic chamber for used in many physics problems. [ 9 ] The Boundary Layer Research Facility (BLRF) operates a 12-inch turbulent pipe flow of glycerine . [ 8 ] Additionally, the facility operates a 20 hp (14.91 kW), open-jet, 1,750 rpm Axial-Flow Fan with a 36.58 m/s (81.83 mph) maximum velocity used for basic engineering research in turbomachinery blading. Another 2.75 meter diameter, 100 hp (74.6 kW) closed-circuit used specifically for research in viscous sublayer and in modeling of turbulent flow of fluids next to a wall at large scale. | https://en.wikipedia.org/wiki/Garfield_Thomas_Water_Tunnel |
Garmin BaseCamp is a map viewing / GIS software package offered free for download by Garmin , primarily intended for use with their GPS navigation devices . BaseCamp serves as a replacement to the now unsupported Garmin MapSource. [ 3 ] [ 4 ] [ 5 ]
The Mac version has not been updated for ARM CPUs, and when launched on M1/M2 CPUs will run on Rosetta 2.
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Garmin_BaseCamp |
The Garmin Fenix (styled fēnix ; pronounced as phoenix ) is a series of multisport GPS watches produced by Garmin . First introduced in 2012, [ 1 ] the Garmin Fenix is aimed at outdoor enthusiasts, adventurers, and athletes.
The Fenix watches offer tracking for a variety of outdoor and indoor activities, allowing users to monitor their performance and progress. Featuring Global Positioning System (GPS) navigation and, starting with the Fenix 5 Plus model, routable topographical maps , [ 2 ] users can track routes, waypoints , and geographical data. The watches also record metrics such as time, distance, speed, pace, elevation, and heart rate .
The Fenix series is noted for its battery life, ruggedness, and durability, designed for use in outdoor activities. [ 3 ]
a. ^ The Garmin Fenix 7 and the second-generation Garmin Epix, while essentially sharing the same core features, diverge notably in their display technology and battery performance. While the Fenix series retains its energy-efficient transflective memory-in-pixel (MiP) display, the Epix Gen 2 features an AMOLED color display, at the expense of higher battery consumption. [ 31 ] | https://en.wikipedia.org/wiki/Garmin_Fenix |
The Garmin Forerunner series is a selection of sports watches produced by Garmin . Most models use the Global Positioning System (GPS) , and are targeted at road runners and triathletes . Forerunner series watches are designed to measure distance, speed, heart rate (optional), time, altitude, steps, and pace. [ 2 ]
The Forerunner series consists of models 101, 201, 301, 205, 305, 50, 405, 60, 405CX, 310XT, 110, 210, 410, 610, 910XT, 70, 10, 220, 620, 15, 920XT, 225, 25, 230, 235, 630, 735XT, 35, 935, 30, 645, 645 Music, 45, 45S, 245, 245 Music, 945, 745, 55, 945 LTE, 255, 255 Music, 955, 955 Solar, 265, 965, 158, 165 (listed in chronological order by release date). All models of the Forerunner series except the 101 include a way to upload training data to a personal computer and training software.
Garmin registered the name "Forerunner" with the United States Patent and Trademark Office in August 2001 but released the first watches—the 101, 201, and 301—in 2003. [ 3 ]
In 2006, the 205 and 305 launched. These models are smaller than the first generation and feature a more sensitive SiRFstarIII GPS receiver chip.
In late 2007, the Forerunner 50 was introduced. As opposed to GPS, this model paired with a foot pod to measure displacement. The Forerunner 50 came with a USB stick that allowed training data to be transferred wirelessly to one's pc. [ 4 ] This feature has since become a staple of Garmin's more full-featured sport watches.
The Forerunner 405 was introduced in 2008 and is significantly smaller than its predecessors, only slightly outsizing a typical wristwatch. The 405 also featured improved satellite discovery and connection.
In 2009, Garmin produced three new models: the Forerunner 60 (an evolution of the Forerunner 50), the Forerunner 405CX (405 chassis), and the Forerunner 310XT (an evolution of the 305 chassis). [ 5 ] New features in these models included additional battery life and vibration alerts on the 310XT and advanced calorie consumption modelling on all watches. The new calorie consumption modelling in these devices was the result of Garmin's first collaboration with Finnish physiological analytics firm First beat. [ 6 ] [ 7 ] The 310XT was also the first watch of the Forerunner series to be waterproof, thus allowing its use for swimming and on all legs of a Triathlon, also thanks to extended battery life. In 2010 a firmware update added vastly improved open-water swimming metrics. [ 8 ]
In 2010, the Forerunner 110, 210 and 410 were introduced. The releases included the addition of a touch-sensitive bezel on the 410, presumably, although heavily debated, allowing for easier scrolling and selection of functions. It was touted as providing "unmatched reliability in sweaty, rainy conditions." [ 9 ]
The Forerunner 610 was released in the spring of 2011. It features a touch-sensitive screen as well as vibration alerts. [ 10 ]
In 2012 the Forerunner 910XT was introduced, which is a development of the 310XT. This version was originally supposed to be released in Q4 of 2011, but the November date had slipped and it was eventually released in Q1 of 2012. New features introduced in this model are the inclusion of the Sifter iv chipset, a barometric altimeter, and improved swimming metrics using an accelerometer in the watch. This allowed it to automatically count pool lengths and to recognize swimming styles. [ 11 ]
A further addition to the series was the Forerunner 10, a simple watch offering just GPS tracking of activities and run metrics like distance, pace and calories burned.
At the end of 2013 the Forerunner 220 and 620 were introduced, with colour screens, Bluetooth Low Energy (BLE; allowing connections to some smartphones), and, for the 620 only, a touchscreen, Wi-Fi (allowing automatic activity download) and enhanced "running dynamics" given by an updated Heart rate monitor. These watches also abandon syncing via the ANT+ protocol in favour of wired (USB) and Wi-Fi (620 only) data transfers. They are also fully waterproof, but do not include any kind of swimming mode. [ 12 ] [ 13 ]
In 2014, the Forerunner 15 and 920XT were introduced. The 15 is a development of the 10, adding activity tracking, increased battery life, footpad and heart rate monitor capability. The 920XT is the successor of the 910XT, featuring all the capabilities of it (except ANT+ scale and fitness equipment capability) and adding features found in the 620 such as a colour screen, Wi-Fi data transfers and running dynamics. Additionally, battery life over the 910XT was improved, daily activity tracking, GLONASS support and a swim drill mode added, and the 920XT is the first Garmin watch extensible with custom apps built using the Garmin Connect IQ software development kit. [ 14 ] [ 15 ]
Announced in May 2015, the Forerunner 225 is the first Garmin watch with an integrated optical heart rate monitor. [ 16 ]
Announced in May 2016, the Forerunner 735XT is a triathlon-ready Garmin watch with an integrated optical heart rate monitor. [ 17 ]
In April 2017, Garmin announced the Forerunner 935, billing it as a watch for running and triathlons with features similar to the Fenix 5. The watch boasts 24/7 wrist-based heart rate monitoring and new advanced training features. [ 18 ]
On March 12, 2018, Garmin released the Forerunner 645 and 645 Music marketed as a high-end running watch. The watch adds Garmin Pay, an NFC-enabled touchless pay system and the 645 Music is Garmin's first watch with onboard music storage (4 GB). [ 19 ]
The Forerunner 45/45S, released on April 30, 2019, is an entry-level running watch. The 45S has a smaller bezel (39mm) than the 45 (42mm) - there are no other differences. It has a 3rd generation optical heart rate monitor which features stress detection and Body Battery energy, along with earlier-generation OHR metrics. Bluetooth-connected features include audio prompts, Live Track, and smart notifications. The activity profiles include outdoor running, treadmill, walk, bike, and cardio, with the ability to configure more through Garmin Connect. The Forerunner 45 has built-in incident detection and assistance, which notifies a predetermined contact if it detects a crash or fall and provides a live tracking link for the watch's location. [ 20 ]
The Forerunner 245/245 Music, released on April 30, 2019, are mid-range running watches. The 245 has all of the same capabilities as the 245 Music, though the 245 Music allows you to store and play up to 500 songs directly on the watch or play music through music streaming services, such as Spotify or Deezer , through wireless Bluetooth earphones. The 245 has Garmin Elevate with a 3rd generation optical heart rate monitor which features Pulse Ox, stress detection, Body Battery energy, along with earlier-generation OHR metrics. Also new for the Forerunner is a detailed Activity summary screen, improved Race Predictor and Training Status. [ 21 ]
The Forerunner 945, released on April 30, 2019, is a triathlon-focused feature-rich watch. The 945 allows you to store and play up to 1000 songs directly on the watch or play music through music streaming services, such as Spotify or Deezer, through wireless Bluetooth earphones. The 945 has all of the capabilities of its 935 predecessor and all of the features of the Forerunner 245. Other new features of the 945 are heat and altitude acclimation, training load balance, mapping with Trendline popularity routing, respiration rate, Around me mode, Climber future elevation plot, cartography support and topographical maps, XERO location, and for the golfer, the 945 is preloaded with 41,000 courses. [ 22 ]
The Forerunner 955, released April 30, 2022, is a superset of the Forerunner 945 and includes a touch screen. To extend battery life, the Forerunner 955 Solar has a solar charging ring in the display. Charging for both 955 models is through the proprietary Garmin charging port and a USB-A connector. [ 23 ]
In March 2023, Garmin announced the Forerunner 265/265S and Forerunner 965. Both models are very similar to their predecessors, but feature AMOLED displays for the first time. [ 24 ]
Garmin has released the Garmin Forerunner 158 which is only available in China. [ 25 ]
The Forerunner can be used to record historical data by completing a workout and then uploading the data to a computer to create a log of previous exercise activities for analysis.
Additionally, the Forerunner can be used to navigate during a workout. Users can "mark" their current location and then edit this entry's name and coordinates, which enables navigation to those new coordinates. The watch uses the hh.mm.mm (hours, minutes, and minute decimals) coordinate format. The 310XT can display additional formats; it also has a screen to display current coordinates in real-time.
The user can download a previously-travelled course/route to the Forerunner using Garmin's Communicator software together with the ANT+ technology, and then follow this course/route to "race" against this historical course/route. Until recently this download was possible via the tethered USB connection on the older 205 & 305 models. However, the current version of the software has eliminated this option, requiring the user to acquire a newer model with a wireless connection in order to use this feature.
The user can also make new courses or routes, which can be downloaded to the watch and then followed. This is a convenient way to go on a cross-country bike ride while navigating with the Forerunner. Note: navigating with a course is better than navigating with a route, because a Garmin course can store more points than a Garmin route.
Additionally, a user can create downloadable points of interest ( POIs ) by creating a custom map with Google Maps . POIs can be transferred to the 205 or 305 but not to the 405 or 310XT.
Forerunner 45S
Forerunner 245 Music
Forerunner 255 Music
Forerunner 955 Solar
More details: List of Garmin products
Key: Current Model | https://en.wikipedia.org/wiki/Garmin_Forerunner |
The Garmin G1000 is an electronic flight instrument system (EFIS) typically composed of two display units, one serving as a primary flight display , and one as a multi-function display . Manufactured by Garmin Aviation , it serves as a replacement for most conventional flight instruments and avionics . Introduced in June 2004, the system has since become one of the most popular integrated glass cockpit solutions for general aviation and business aircraft. [ 1 ]
An aircraft with a basic Garmin G1000 installation contains two LCDs (one acting as the primary flight display and the other as the multi-function display) as well as an integrated communications panel that fits between the two. These displays are designated as a GDU, Garmin Display Unit.
Beyond that, additional features are found on newer and larger G1000 installations, such as in business jets. This includes:
Depending on the airplane manufacturer and whether or not a GFC 700 autopilot is installed, the G1000 system will consist of either two GDU 1040 displays (no autopilot), a GDU 1040 PFD/GDU 1043 MFD (GFC 700 autopilot installed), or a GDU 1045 PFD/GDU 1045 MFD (GFC 700 autopilot installed with VNAV ).
The GDU 1040 is the standard base bezel with no autopilot/flight director mode selection keys below the heading bug. The GDU 1043 has autopilot/flight director keys for all GFC 700 modes except VNAV. The GDU 1045 is essentially identical to the GDU 1043 except for the addition of an autopilot/flight director mode for VNAV. Depending on how the units are installed, an MFD failure may, or may not, affect autopilot or flight director use. If a GDU 1040 is used as a PFD in an airplane equipped with a GFC 700 autopilot, a failure of the MFD (which houses the autopilot mode selection keys) will leave the autopilot engaged, but the modes cannot be changed because no autopilot keys are present on the PFD. But, if an MFD failure occurs in an airplane with the GFC 700 autopilot and either a GDU 1043 or a GDU 1045 bezel installed as a PFD, the pilot will have full use of the autopilot through the keys on the PFD.
Both the PFD and MFD each have two slots for SD memory cards . The top slot is used to update the Jeppesen aviation database (also known as NavData) every 28 days, and to load software and configuration to the system. The aviation database must be current to use GPS for navigation during IFR instrument approaches. The bottom slot houses the World terrain and Jeppesen obstacle databases. While terrain information rarely changes or needs to be updated, obstacle databases can be updated every 56 days through a subscription service. The top card can be removed from the G1000 system following an update, but the bottom card must stay in both the PFD and MFD to ensure accurate terrain awareness and TAWS-B information.
The primary flight display (PFD) shows the basic flight instruments, such as the attitude indicator , airspeed indicator , altimeter , heading indicator , and course deviation indicator. A small map called the "inset map" can be enabled in the corner. The buttons on the PFD are used to set the squawk code on the transponder . The PFD can also be used for entering and activating flight plans. The PFD also has a "reversionary mode" which is capable of displaying all information shown on the MFD (for example, engine gauges and navigational information). This capability is provided in case of an MFD failure.
The multi-function display (MFD) typically shows a moving map on the right side, and engine instrumentation on the left. Most of the other screens in the G1000 system are accessed by turning the knob on the lower right corner of the unit. Screens available from the MFD other than the map include the setup menus, information about nearest airports and NAVAIDs , Mode S traffic reports, terrain awareness, XM radio , flight plan programming, and GPS RAIM prediction.
The G1000 system consists of several integrated components which sample and exchange data or display information to the pilot.
The GDU display unit acts as the primary source of flight information for the pilot. Each display can interchangeably serve as a primary flight display (PFD) or multi-function display (MFD). The wiring harness within the aircraft specifies which role each display is in by default. All of the displays within an aircraft are interconnected using a high-speed Ethernet data bus. A G1000 installation may have two GDUs (one PFD and one MFD) or three (one PFD for each pilot and an MFD). There are several different GDU models in service, which have different screen sizes (from 10 inches to 15 inches) and different bezel controls.
In normal operation, the display in front of the pilot is the PFD and will provide aircraft attitude, airspeed, altitude, vertical speed, heading, rate-of-turn, slip-and-skid, navigation, transponder, inset map view (containing map, traffic, and terrain information), and systems annunciation data. The second display, typically positioned to the right of the PFD, operates in MFD mode and provides engine instrumentation and a moving map display. The moving map can be replaced or overlaid by various other types of data, such as satellite weather, checklists, system information, waypoint information, weather sensor data, and traffic awareness information.
Both displays provide redundant information regarding communications and navigation radio frequency settings even though each display is usually only paired with one GIA Integrated Avionics Unit. In the event of a single display failure, the remaining display will adopt a combined "reversionary mode" and automatically become a PFD combined with engine instrumentation data and other functions of the MFD. A red button labeled "reversionary mode" or "display backup," located on the GMA audio panel, is also available to the pilot to select this mode manually if desired.
The GMA panel provides buttons for selecting what audio sources are heard by each member of the cockpit. It also includes a button for forcing the integrated cockpit into its fail-safe reversionary mode.
The GMC and GCU controllers are panel-mounted modules which provide a more intuitive interface for the pilot than that provided by the GDU. The GMC controls the G1000's autopilot, while the GCU is used to enter navigational data and control the GDU's
The GIA unit is a combined communications and navigation radio, and also serves as the primary data aggregator for the G1000 system. It provides a two-way VHF communications transceiver, a VHF navigation receiver with glideslope, a GPS receiver, and a variety of supporting processors. Each unit is paired with a GDU display, which acts as a controlling unit. The GIA 63W, found on many newer G1000 installations, is an updated version of the older GIA 63 which includes Wide Area Augmentation System support.
The GDC computer replaces the internal components of the pitot-static system in traditional aircraft instrumentation. It measures airspeed, altitude, vertical speed, and outside air temperature. This data is then provided to all the displays and integrated avionics units.
The GRS system uses solid-state sensors to measure aircraft attitude, rate of turn, and slip and skid. This data is then provided to all the integrated avionics units and GDU display units. Unlike many competing systems, the AHRS can be rebooted and recalibrated in flight during turns of up to 20 degrees.
The GMU magnetometer measures aircraft heading and is a digital version of a traditional compass. It does so through aligning itself with the magnetic flux lines of the earth.
Either the GTX 32 or GTX 33 transponder can be used in the G1000 system, although the GTX 33 is far more common. The GTX 32 provides standard mode-C replies to ATC interrogations while the GTX 33 provides mode-S bidirectional communications with ATC and therefore can indicate traffic in the area as well as announce itself spontaneously via "squittering" without prior interrogation.
The GEA unit measures a large variety of engine and airframe parameters, including engine RPM, manifold pressure, oil temperature, cylinder head temperature, exhaust gas temperature, and fuel level in each tank. This data is then provided to the integrated avionics units.
The GSD is a data aggregator system included on complex G1000 systems, such as that found on the Embraer Phenom 100 . It serves as a point of connection which allows external systems to communicate with the G1000.
As a condition of certification, all aircraft utilizing the G1000 integrated cockpit must have a redundant airspeed indicator, altimeter, attitude indicator, and magnetic compass. In the event of a failure of the G1000 instrumentation, these backup instruments become primary.
In addition, a secondary power source is required to power the G1000 instrumentation for a limited time in the event of a failure of the aircraft's alternator and primary battery.
The Garmin G1000 is generally certified on new general aviation aircraft, including Beechcraft , Cessna , Diamond , Cirrus , Mooney , Piper , Quest (the Quest Kodiak ), [ 2 ] and Tiger . In late 2005, Garmin first announced in the G1000 in the Columbia Aircraft Model 400, [ 3 ] later sold to Cessna. Garmin announced its first G1000 retrofit program for the Beechcraft C90 King Air in 2007. That same year the Garmin G1000 became a jet platform, as the avionics system for the Cessna Citation Mustang very light jet . [1] Versions of the G1000 are also used in the Embraer Phenom 100 and Embraer Phenom 300 , and PiperJet , as well as the Bell SLS helicopter . [ 4 ]
The G1000 competes with the Avidyne Entegra and Chelton FlightLogic EFIS glass cockpits . However, there are significant differences with regard to the features, degree of integration, intuitive aspects of the design, and overall product utility. Note that the Chelton system is not typically found in airplanes that include the less expensive G1000 or Avidyne systems.
In 2009 Garmin introduced the Garmin G500 as a retrofit glass cockpit. [ 5 ] The G500 has the majority of the capabilities of the G1000, other than integration with the aircraft engine system.
As it has GPS , communication , and radio navigation components built directly into the system, it both consolidates components into a centralized location and, for the same reason, becomes potentially more costly to repair or replace. The system has the potential to reduce downtime as key components, such as the AHRS, ADC and PFD, are modular and easily replaced. The system's design also prevents the failure of a single component from "cascading" through other components.
The G1000 is compatible with the latest enhanced vision system (EVS) technology. Enhanced vision systems use thermal and infrared cameras to see real-time images and help turn obscurants such as bad weather, night time, fog, dust and brownouts into better images that can see 8-10 times farther than the naked eye.
There are some safety concerns with all glass cockpits, such as the failure of the primary flight displays (PFD). The Garmin G1000 system offers a reversionary mode that will present all of the primary flight instrumentation on the remaining display. In addition, there are multiple GPS units, and electronic redundancy incorporated extensively throughout the design of the system.
Flying any glass cockpit aircraft requires transition training to familiarize the pilot with the aircraft's systems. Transition training is most effective when a pilot prepares ahead of time. [ 6 ] Most general aviation manufacturers using the G1000 system have FAA Industry Training Standards (FITS) training programs for pilots transitioning into their airplanes. FAA FITS compliant training is recommended for any pilot transitioning to the G1000 or any other glass cockpit prior to operating the aircraft in instrument meteorological conditions (IMC) or if operating a glass cockpit aircraft for the first time. Glass cockpit aircraft may not be suitable for primary training. [ 7 ]
One of the most effective resources for preparing for G1000 transition training include the Garmin simulator software. In addition, some flight schools now have G1000 flight training devices (FTDs) that provide realistic simulation.
All of the most current Garmin G1000 pilot's guides are available from Garmin as free downloads in PDF format. [ 8 ]
Related development | https://en.wikipedia.org/wiki/Garmin_G1000 |
The Garmin G3000 (also G3000H and G2000/G5000) is an avionics interface system designed by Garmin Aviation for light turbine aircraft. [ 1 ] The integrated touchscreen system contains multiple glass cockpit displays for operating a synthetic vision system and a three-dimensional rendering of terrain. [ 2 ]
On 30 October 2019, Garmin announced that the Piper M600 and Cirrus Vision Jet would become the first general aviation aircraft certified with the company's Emergency Autoland system, designed to automatically land the aircraft in an emergency. The Autoland system was introduced on 18 May 2020 as part of "Autonomí", Garmin's suite of automated, safety-enhancing tools. [ 3 ] [ 4 ] [ 5 ]
In June 2021, it won the Collier Trophy for "the greatest achievement in aeronautics or astronautics in America" for 2020. [ 6 ]
Related development | https://en.wikipedia.org/wiki/Garmin_G3000 |
iQue ( / aɪ ˈ k j uː / eye- KYOO ; like "IQ") was a line of personal digital assistants (PDA) with integrated Global Positioning System (GPS) receivers sold by Garmin . It was introduced in 2003 and discontinued in mid-2008.
The Garmin iQue 3600 was among the first devices to integrate GPS technology into a PDA . The line included devices running Palm OS and Windows Mobile operating systems. As of June 2008, all iQue products have been discontinued by Garmin and are no longer being supported or repaired by the company.
Integration of address book and date book with GPS location provides convenient ways for turn-by-turn voice guided navigation.
All devices include the Que software, including map display, auto-routing, search for points of interest and addresses in the map database, etc.
All devices have Wide Area Augmentation System (WAAS) and European Geostationary Navigation Overlay Service (EGNOS) abilities.
Popular accessories include external GPS antennas, vehicle mounts, power adaptors and external speakers.
The Que software provides integration (with address and datebook), navigation and mapping. | https://en.wikipedia.org/wiki/Garmin_iQue |
In mathematical physics , the Garnier integrable system , also known as the classical Gaudin model is a classical mechanical system discovered by René Garnier in 1919 by taking the ' Painlevé simplification' or 'autonomous limit' of the Schlesinger equations . [ 1 ] [ 2 ] It is a classical analogue to the quantum Gaudin model due to Michel Gaudin [ 3 ] (similarly, the Schlesinger equations are a classical analogue to the Knizhnik–Zamolodchikov equations ). The classical Gaudin models are integrable .
They are also a specific case of Hitchin integrable systems , when the algebraic curve that the theory is defined on is the Riemann sphere and the system is tamely ramified .
The Schlesinger equations are a system of differential equations for n + 2 {\displaystyle n+2} matrix-valued functions A i : C n + 2 → M a t ( m , C ) {\displaystyle A_{i}:\mathbb {C} ^{n+2}\rightarrow \mathrm {Mat} (m,\mathbb {C} )} , given by ∂ A i ∂ λ j = [ A i , A j ] λ i − λ j j ≠ i {\displaystyle {\frac {\partial A_{i}}{\partial \lambda _{j}}}={\frac {[A_{i},A_{j}]}{\lambda _{i}-\lambda _{j}}}\qquad \qquad j\neq i} ∑ j ∂ A i ∂ λ j = 0. {\displaystyle \sum _{j}{\frac {\partial A_{i}}{\partial \lambda _{j}}}=0.}
The 'autonomous limit' is given by replacing the λ i {\displaystyle \lambda _{i}} dependence in the denominator by constants α i {\displaystyle \alpha _{i}} with α n + 1 = 0 , α n + 2 = 1 {\displaystyle \alpha _{n+1}=0,\alpha _{n+2}=1} : ∂ A i ∂ λ j = [ A i , A j ] α i − α j j ≠ i {\displaystyle {\frac {\partial A_{i}}{\partial \lambda _{j}}}={\frac {[A_{i},A_{j}]}{\alpha _{i}-\alpha _{j}}}\qquad \qquad j\neq i} ∑ j ∂ A i ∂ λ j = 0. {\displaystyle \sum _{j}{\frac {\partial A_{i}}{\partial \lambda _{j}}}=0.} This is the Garnier system in the form originally derived by Garnier.
There is a formulation of the Garnier system as a classical mechanical system, the classical Gaudin model, which quantizes to the quantum Gaudin model and whose equations of motion are equivalent to the Garnier system. This section describes this formulation. [ 4 ]
As for any classical system, the Gaudin model is specified by a Poisson manifold M {\displaystyle M} referred to as the phase space , and a smooth function on the manifold called the Hamiltonian .
Let g {\displaystyle {\mathfrak {g}}} be a quadratic Lie algebra , that is, a Lie algebra with a non- degenerate invariant bilinear form κ {\displaystyle \kappa } . If g {\displaystyle {\mathfrak {g}}} is complex and simple , this can be taken to be the Killing form .
The dual , denoted g ∗ {\displaystyle {\mathfrak {g}}^{*}} , can be made into a linear Poisson structure by the Kirillov–Kostant bracket .
The phase space M {\displaystyle M} of the classical Gaudin model is then the Cartesian product of N {\displaystyle N} copies of g ∗ {\displaystyle {\mathfrak {g}}^{*}} for N {\displaystyle N} a positive integer.
Associated to each of these copies is a point in C {\displaystyle \mathbb {C} } , denoted λ 1 , ⋯ , λ N {\displaystyle \lambda _{1},\cdots ,\lambda _{N}} , and referred to as sites .
Fixing a basis of the Lie algebra { I a } {\displaystyle \{I^{a}\}} with structure constants f c a b {\displaystyle f_{c}^{ab}} , there are functions X ( r ) a {\displaystyle X_{(r)}^{a}} with r = 1 , ⋯ , N {\displaystyle r=1,\cdots ,N} on the phase space satisfying the Poisson bracket { X ( r ) a , X ( s ) b } = δ r s f c a b X ( r ) c . {\displaystyle \{X_{(r)}^{a},X_{(s)}^{b}\}=\delta _{rs}f_{c}^{ab}X_{(r)}^{c}.}
These in turn are used to define g {\displaystyle {\mathfrak {g}}} -valued functions X ( r ) = κ a b I a ⊗ X ( r ) b {\displaystyle X^{(r)}=\kappa _{ab}I^{a}\otimes X_{(r)}^{b}} with implicit summation .
Next, these are used to define the Lax matrix which is also a g {\displaystyle {\mathfrak {g}}} valued function on the phase space which in addition depends meromorphically on a spectral parameter λ {\displaystyle \lambda } , L ( λ ) = ∑ r = 1 N X ( r ) λ − λ r + Ω , {\displaystyle {\mathcal {L}}(\lambda )=\sum _{r=1}^{N}{\frac {X^{(r)}}{\lambda -\lambda _{r}}}+\Omega ,} and Ω {\displaystyle \Omega } is a constant element in g {\displaystyle {\mathfrak {g}}} , in the sense that it Poisson commutes (has vanishing Poisson bracket) with all functions.
The (quadratic) Hamiltonian is H ( λ ) = 1 2 κ ( L ( λ ) , L ( λ ) ) {\displaystyle {\mathcal {H}}(\lambda )={\frac {1}{2}}\kappa ({\mathcal {L}}(\lambda ),{\mathcal {L}}(\lambda ))} which is indeed a function on the phase space, which is additionally dependent on a spectral parameter λ {\displaystyle \lambda } . This can be written as H ( λ ) = Δ ∞ + ∑ r = 1 N ( Δ r ( λ − λ r ) 2 + H r λ − λ r ) , {\displaystyle {\mathcal {H}}(\lambda )=\Delta _{\infty }+\sum _{r=1}^{N}\left({\frac {\Delta _{r}}{(\lambda -\lambda _{r})^{2}}}+{\frac {{\mathcal {H}}_{r}}{\lambda -\lambda _{r}}}\right),} with Δ r = 1 2 κ ( X ( r ) , X ( r ) ) , Δ ∞ = 1 2 κ ( Ω , Ω ) {\displaystyle \Delta _{r}={\frac {1}{2}}\kappa (X^{(r)},X^{(r)}),\Delta _{\infty }={\frac {1}{2}}\kappa (\Omega ,\Omega )} and H r = ∑ s ≠ r κ ( X ( r ) , X ( s ) ) λ r − λ s + κ ( X ( r ) , Ω ) . {\displaystyle {\mathcal {H}}_{r}=\sum _{s\neq r}{\frac {\kappa (X^{(r)},X^{(s)})}{\lambda _{r}-\lambda _{s}}}+\kappa (X^{(r)},\Omega ).}
From the Poisson bracket relation { H ( λ ) , H ( μ ) } = 0 , ∀ λ , μ ∈ C , {\displaystyle \{{\mathcal {H}}(\lambda ),{\mathcal {H}}(\mu )\}=0,\forall \lambda ,\mu \in \mathbb {C} ,} by varying λ {\displaystyle \lambda } and μ {\displaystyle \mu } it must be true that the H r {\displaystyle {\mathcal {H}}_{r}} 's, the Δ r {\displaystyle \Delta _{r}} 's and Δ ∞ {\displaystyle \Delta _{\infty }} are all in involution. It can be shown that the Δ r {\displaystyle \Delta _{r}} 's and Δ ∞ {\displaystyle \Delta _{\infty }} Poisson commute with all functions on the phase space, but the H r {\displaystyle {\mathcal {H}}_{r}} 's do not in general. These are the conserved charges in involution for the purposes of Arnol'd Liouville integrability .
One can show { H r , L ( λ ) } = [ X ( r ) λ − λ r , L ( λ ) ] , {\displaystyle \{{\mathcal {H}}_{r},{\mathcal {L}}(\lambda )\}=\left[{\frac {X^{(r)}}{\lambda -\lambda _{r}}},{\mathcal {L}}(\lambda )\right],} so the Lax matrix satisfies the Lax equation when time evolution is given by any of the Hamiltonians H r {\displaystyle {\mathcal {H}}_{r}} , as well as any linear combination of them.
The quadratic Casimir gives corresponds to a quadratic Weyl invariant polynomial for the Lie algebra g {\displaystyle {\mathfrak {g}}} , but in fact many more commuting conserved charges can be generated using g {\displaystyle {\mathfrak {g}}} -invariant polynomials. These invariant polynomials can be found using the Harish-Chandra isomorphism in the case g {\displaystyle {\mathfrak {g}}} is complex, simple and finite.
Certain integrable classical field theories can be formulated as classical affine Gaudin models, where g {\displaystyle {\mathfrak {g}}} is an affine Lie algebra . Such classical field theories include the principal chiral model , coset sigma models and affine Toda field theory . [ 5 ] As such, affine Gaudin models can be seen as a 'master theory' for integrable systems, but is most naturally formulated in the Hamiltonian formalism, unlike other master theories like four-dimensional Chern–Simons theory or anti-self-dual Yang–Mills .
A great deal is known about the integrable structure of quantum Gaudin models . In particular, Feigin , Frenkel and Reshetikhin studied them using the theory of vertex operator algebras , showing the relation of Gaudin models to topics in mathematics including the Knizhnik–Zamolodchikov equations and the geometric Langlands correspondence . [ 6 ] | https://en.wikipedia.org/wiki/Garnier_integrable_system |
The Garrod Lecture and Medal is an award presented by the British Society for Antimicrobial Chemotherapy . It was established in 1982 and named for L. P. Garrod . The medal is made of silver by the Birmingham Mint . The recipient of the award is considered by the society as having international authority in the field of antimicrobial chemotherapy . They are invited to deliver an accompanying lecture and receive honorary membership of the Society. [ 1 ] [ 2 ] | https://en.wikipedia.org/wiki/Garrod_Lecture_and_Medal |
The Garshelis effect causes springs made of magnetostrictive material to have their magnetization changed due to the compression of the spring. [ 1 ] It is a correlation between magnetization and torsional stress. If the magnetization is due to direct current, it is the inverse of the Wiedemann effect .
It is named after Ivan Garshelis, who investigated the effect. [ 2 ]
This electromagnetism -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Garshelis_effect |
In mathematics , a Garside element is an element of an algebraic structure such as a monoid that has several desirable properties.
Formally, if M is a monoid, then an element Δ of M is said to be a Garside element if the set of all right divisors of Δ,
is the same set as the set of all left divisors of Δ,
and this set generates M .
A Garside element is in general not unique: any power of a Garside element is again a Garside element.
A Garside monoid is a monoid with the following properties:
A Garside monoid satisfies the Ore condition for multiplicative sets and hence embeds in its group of fractions: such a group is a Garside group . A Garside group is biautomatic and hence has soluble word problem and conjugacy problem . Examples of such groups include braid groups and, more generally, Artin groups of finite Coxeter type . [ 1 ]
The name was coined by Patrick Dehornoy and Luis Paris [ 1 ] to mark the work on the conjugacy problem for braid groups of Frank Arnold Garside (1915–1988), a teacher at Magdalen College School, Oxford who served as Lord Mayor of Oxford in 1984–1985. [ 2 ]
This abstract algebra -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Garside_element |
Dr John Garton , of the firm of Garton Brothers of Newton-le-Willows in the United Kingdom was the Originator of Scientific Farm Plant Breeding. He is credited as the first scientist to show that the common grain crops and many other plants are self-fertilizing. He also invented the process of multiple cross-fertilization of crop plants.
In 1898 the business became known as Gartons Limited and, under the inspired commercial leadership of George Peddie Miln , was to become the British Empire's largest plant breeding and seed company .
A public company from the start, its shares were traded on the London Stock Exchange from 1947.
John Garton and his two brothers, Robert and Thomas, were in business with their father, Peter, in Golborne and Newton-le-Willows in Lancashire , England, as corn and agricultural merchants.
As a young man, John Garton (1863–1922), [ 1 ] was the first to understand that whilst some agricultural plants were self-pollinating, others were cross-pollinating. He began experimenting with the artificial cross pollination firstly of cereal plants, then herbage species and root crops.
He attracted the friendship and encouragement of a young Scottish seedsman, George Peddie Miln (1861–1928) [ 2 ] who had trained in Dundee and was seed manager of Dicksons Limited of Chester .
Knowing he had developed a far reaching new technique in plant breeding John Garton began to carry out many thousands of controlled crosses on fields at the family farm in Newton-le-Willows. He and his colleagues tried in 1889 to interest the UK government's new Board of Agriculture in the invention they called Scientific Farm Plant Breeding . But this was to no avail.
Robert [ 3 ] and John Garton made a commercial start as R. & J. Garton. [ 4 ] They launched their first variety, 'Abundance' oat, in 1892.
Generous publicity followed in the press, together with the publication of articles by botanists in the Journal of the Royal Agricultural Society of England , and in the Transactions of the Royal Highland and Agricultural Society of Scotland in 1894 and 1898. [ 5 ] Professor Robert Wallace (1853–1939) of the University of Edinburgh said 'Under the system originated by Mr John Garton an infinite number of new and distinct breeds of oats, barleys, wheats, clovers and grasses have been produced'. [ 6 ]
In 1898 a public company was launched, Gartons Limited. It was based in Warrington . Many of the 600 or so subscribers for £50,000 cumulative preference shares of 6% rising to 10% were farmers.
George Peddie Miln joined the company as managing director, together with Robert Garton, Thomas R. Garton, Thomas Baxter and Arthur Smith as directors. [ 7 ] Robert and John Garton agreed to continue to work for the company for five years for £500 and to receive the entire ordinary share capital of the new company of £50,000. [ clarification needed ]
It rapidly became the United Kingdom's best known plant breeding and seed company, and also exported seeds widely. [ 8 ]
In 1900 an endowment was made to found the Garton Lectureship in Indian and Colonial Agriculture at the University of Edinburgh. [ 9 ] The Garton Lectureship still exists as a biennial award to promising young lecturers in the School of Agriculture but is without emoluments and is no longer tied to colonial agriculture. [ 10 ]
Noel Kingsbury writes: [ 11 ]
From the late nineteenth century on, seed companies began to play an increasingly important, if not dominant, role in breeding non-cereal crops and a major role in producing varieties for market gardening and for private growers. The production of new cereals was a somewhat different matter – the fact that they were so vitally important for national food supplies and involved large-scale and long-term work made it more likely that they would be the concern of government.
There were exceptions though, one being the family firm of Gartons of Warrington, Lancashire, in the north of England. Their production of cereals – oats in particular – was appreciated as internationally important during the latter quarter of the nineteenth century and the early years of the twentieth; (The American wheat breeder) Mark Carleton visited them in 1898 and was reportedly astonished at their work, Garton varieties were widely exported throughout the British Empire (then by far and away the world's largest political unit) and the United States.
"That private companies could be so effective in breeding cereal grains indicated that there was no link of necessity between their improvement and the publicly funded research that was to so dominate this sector over so much of the next century."
In 1903 Professor Willet M. Hays (1859–1927) of the Agricultural Experiment Station in Minnesota , USA said 'No one has done more brilliant work in Agricultural Plant Breeding than Messrs. Garton, and this is from now on to be recognised.' [ 12 ]
The introduction to their 1899 Spring Catalogue [ 13 ] reads:
Our original idea for the dissemination of the seed of these new breeds as the stocks became sufficiently large for the purpose, was through some public body as in the form of an annual free seed distribution upon similar lines to the free seed distributions carried out by the Governments of the United States, Canada, and several of the British Colonies.
On three successive occasions we approached Her Majesty's Government with this object in view, the first occasion being on the formation of the Board of Agriculture, in 1889, when we offered to hand over the whole of the valuable results, providing that body would undertake their dissemination and the continuance of the work, either in the form of an annual free seed distribution or at current market price.
Upon the last occasion our offer was accompanied by letters and reports from all the leading Agricultural Professors, Botanists, and Scientists in the Kingdom, setting forth the national benefit which would accrue from the dissemination of the results in the form we had suggested. The final reply of Her Majesty's Government, however, was that whilst fully recognising the value of the work, owing to there being no precedent upon which to act in such a matter, they were unable to avail themselves of the offer. This was much to be regretted for had our ideas been carried into effect the British farmer would have been placed in immediate possession of important results, which in the hands of a Public Company would not reach him for many years.
Our efforts in this direction not having been successful, and as we were not in a position to undertake the work of distribution ourselves, we have placed it in the lands [ verification needed ] of a Public Company, and we trust that the continued efforts made by us on behalf of the British farmer will be fully appreciated by him, through his support of the Company responsible for the distribution of the seed of our new breeds of agricultural plants
R. & J. Garton''
The firm's first historic introduction was 'Abundance' oat , the world's first agricultural plant variety bred from a controlled cross, introduced to commerce in 1892. [ 14 ]
Among the other 170 crop varieties [ 15 ] that Gartons bred and introduced to commerce were:
On 23 March 1922 the Senatus Academicus of the University of Edinburgh offered to confer the honorary doctorate of LL.D on John Garton shortly before his death, which he duly accepted. [ 22 ] [ 23 ] [ 24 ] At its meeting on 6 July 1922 the Senatus Academicus learned that John Garton had died. [ 25 ]
The programme and report of the Graduation Ceremony held on 21 July 1922 reads
The Senatus Academicus recently conferred the Honorary Degree of Doctor of Laws upon the late John Garton, who duly accepted it. The Degree would have been formally conferred on the present occasion but for his lamented death. Mr Garton invented the process of multiple cross fertilisation of crop plants and has been the means in a great measure of revolutionising field culture by producing hundreds of new and improved varieties which have greatly increased the yields of all the common crops of the farm. The achievement proved to be of immense national importance during the War.
Mr Garton first showed that the common grain crops and many other crop plants are self-fertilising. Up till that time they were generally believed to be fertilised by wind or insects.
Mr Garton’s results got in crossing different species of grasses helped to develop the modern conception of species.
Twenty-two tears ago Mr Garton provided the means to establish the Garton Lectures on Colonial and Indian Agriculture, and subsequently he permanently endowed them as an integral part of the work of the Chair of Agriculture.
The plant breeding grounds were initially at Newton-le-Willows but moved to Acton Grange, two and a half miles south west of Warrington before settling in about 1930 at Little Leigh near Northwich in Cheshire . A seed development farm was located in Essex , and root crop trials were located on farms in the north of England and in Scotland. Traditionally groups of farmers were invited in mid-summer to inspect the plant breeding grounds and be entertained by the company.
Initially the Seed Warehouse for cleaning and distributing seed was in Newton-le-Willows but moved to Friars Green in Warrington in 1899 by which time the offices were at Thynne Street, Warrington. [ 26 ] A purpose-built seven story Seed Warehouse and separate Head Office were built at Arpley, Warrington in 1910. [ 27 ] There was an L. M. S. railway siding into the Seed Warehouse. On 25 April 1912 the Seed Warehouse burned down [ 28 ] but quickly rebuilt largely by the same builders. Seed cleaning machinery, some unique to the company, ensured the purity of the product. As time went by fewer seeds were 'picked' or cleaned by hand by upwards of one hundred staff as machinery became more sophisticated. Across the top of roof of the warehouse was the company's name which had to be disguised during wartime.
From the beginning Gartons Limited tested its seeds for purity and germination at its own seed testing laboratories in Warrington. The 1920 Seeds Act , for the first time, made testing and declaring for purity and germination a legal requirement for all seed companies. The Official Seed Testing Station was created in 1917, firstly in Victoria Street in Westminster , London and then in 1921 within the newly formed National Institute of Agricultural Botany in Cambridge . Larger seed companies including Gartons Limited were licensed to carry out their own purity and germination testing.
Gartons Limited was the United Kingdom's only major agricultural plant breeding company. But this caused them difficulties as early as in their Spring 1900 seed catalogue where a paragraph of the introduction reads:
It has come to our knowledge that nearly all the New Breeds introduced by us up to the present time have been renamed by various dealers and are being offered by them under different names. Although the honesty of this conduct is more than questionable, we are resigned for the present to regard it as a novel form of flattery, but we strongly recommend all those who wish to secure our Seeds to order them direct from us, as they cannot be procured from any other genuine source.
After the Great War (1914–1918) the United Kingdom government funded cereal breeding at the Plant Breeding Institute at Cambridge which had been founded in 1912, and funded the setting up of plant breeding stations in Edinburgh (1921), Aberystwyth (1919) and in Glasnevin, Northern Ireland in competition with Gartons Limited.
The 1960 Report of the Committee on Transactions in Seeds set up by Parliament entitled Plant Breeders' Rights [ 29 ] stated that whilst two thirds of breeding work was by then carried out by government organisations, one third was in the hands of private breeders. And yet the only non-government funded agricultural crop plant breeding, research and testing establishment visited by the committee was to Gartons Limited. [ 30 ] The United Kingdom's Plant Varieties and Seeds Act 1964 allowed plant breeders to fully protect and be rewarded for their introductions. The last variety bred by Gartons, 'Apex' wheat, was the first British bred wheat to be awarded plant breeders rights in 1967 under this legislation. [ 31 ] [ 32 ]
The eldest of the three Garton brothers, Robert Garton, was the first chairman of Gartons Limited. He died in February 1950, aged 91, [ 33 ] a widower with no children. He was succeeded by the youngest brother, Thomas R. Garton, who died in May 1956. His son, John, was chairman from August 1963 until September 1965. Dr John Garton, the middle of the three brothers, was never, a director.
Nine members of the Miln family were involved with the business over a period of seventy five years.
Born at Linlathen, Broughty Ferry in 1861, George Peddie Miln trained in a Dundee seed warehouse, the traditional Scottish training for a young man with ambition in the seed trade. He moved to Chester and ran one of its old established seed merchants before joining Gartons Limited as its first managing director in 1898. He was a member of Her Majesty's Board of Agriculture Seeds Advisory Council during the first World War. Both the Seeds Act 1920 and the formation of the National Institute of Agricultural Botany came about with his considerable encouragement during his three-year presidency of the Seed Trade Association of the United Kingdom. Of his eleven children, five trained in the seed trade. He was a Justice of the Peace in the City of Chester , a Fellow of the Linnean Society and a member of the Council of the Royal Agricultural Society of England. He died aged 68 following an unsuccessful operation.
When George P. Miln died in 1928 he was succeeded as managing director by his eldest son, Thomas Edward Miln (1890–1963) [ 34 ] who for over twenty five years was chairman of the Retail Committee of the Seed Trade Association of the United Kingdom which proudly kept its independence from government control during World War II. A plant breeder as well as a businessman he is credited with the introduction of the sugar beet crop to UK agriculture.
When Gartons Limited became a public quoted company on the London Stock Exchange in 1947 T. E. Miln entered into a further ten year employment contract as managing director, even though he was already 59, such was his reputation. Both his sons, Wallace and George, joined him in the business.
T. E. Miln was succeeded in 1961 by his elder son, Wallace Miln (1919–1994) also a skilled plant breeder and seed analyst. [ 35 ] Wallace Miln was one of the three founders of the British Association of Plant Breeders at the time of the introduction of the United Kingdom's Plant Varieties and Seeds Act 1964. He was twice President of the Seed Trade Association of United Kingdom. He left Gartons Limited in 1973 to join his elder son, Barnaby Miln , who had trained at Gartons and later with Northrup-King in Minneapolis before setting up his own seed business at Bodenham in Herefordshire.
From 1947 Gartons Limited's shares were quoted on the London Stock Exchange. The company's profits for the previous seven years had averaged £48,940. [ 36 ] In 1949 the profit of £75,340 was the highest ever recorded [ 37 ] by the company.
In 1965 Peter Darlington [ 38 ] became chairman of Gartons Limited. In a dramatic change of direction in 1967 Gartons Limited ceased retailing seeds directly to farmers. Instead a new brand was created, Gartons GROplan, and marketing became wholesale through agricultural merchants throughout the United Kingdom.
In 1970 Charles Hoskins became Production Director. Charles Hoskins had previously been with Twyford Seeds and spent twelve years as General Manager of Conder Seeds having under the directorship of his brother Peter Hoskins been responsible for the inception of this profitable and successful business.
Decline following Acquisition of Gartons Groplan By Agricultural Holdings (Hurst Gunson)
Gartons GROplan was sold to Agricultural Holdings Company Limited (Hurst Gunson) in 1971, [ 39 ] but Gartons Limited continued as a plant breeding company. Peter Darlington immediately resigned from Gartons Groplan to concentrate on his responsibilities with Gartons Limited and Peter Darlington Partners. Wallace Miln and Charles Hoskins both left Gartons Groplan following the take over by Agricultural Holdings Limited (Hurst Gunson). As already stated Wallace Miln joined his son Barnaby at JB Seeds and Charles Hoskins joined Sinclair McGill, the highly respected Boston based Plant Breeders and Seed Specialists, in 1974 and was appointed Production Director at Sinclair McGill (East) in 1978
Bob Beeton was another senior employee to leave following the take over by Agricultural Holdings Limited (Hurst Gunson.) Bob Beeton had been Sales Manager at Garton Groplan and in 1974 joined Elsoms Spalding, the Spalding-based Plant Breeders and Seed Specialists, as Area Sales Manager for East Anglia. Elsoms Spalding remains a family company to this day. Elsoms Spalding still enjoys a justifiable excellent reputation.
Gartons plc, as it became known, ceased trading in 1983. [ 40 ] The seed warehouse at Bridge Foot, Warrington, which had dominated the town centre skyline since 1910, was demolished in October 1986. [ 41 ] A hotel was built on the site.
These Explanatory Notes come from the Gartons Seed Catalogue for Spring 1900:
To those who are not acquainted with the botanical construction of plants it may be well to explain that plants possess generative organs, which correspond to those of the male and female in the animal kingdom. In the animal kingdom, progeny is derived from the mating of different animals of the same breed; in the vegetable kingdom the rule is that the seed is produced through the agency of the generative organs growing together on the same plant. Prior to the commencement of the work initiated by us and carried on during the past 20 years, which has led to the production of our New and Improved Breeds of agricultural plants, it was a recognised belief that many farm plants in the production of their seed were more or less cross-fertilised. The results of our experiments however have proved that such was not the case but that constant in-and-in breeding was the rule.
Where such in-and-in breeding takes place the results are governed by the same natural laws as the in-and-in breeding of animals. In the production of New Breeds of animals the rule followed is to mate two animals of distinct breeds. The progeny, when fixity of type has been secured, constitutes a New Breed.
Under our system of plant breeding we carry the mating of varieties or breeds far beyond what is practised in the animal kingdom. In the first instance we mate varieties and also what were formerly regarded as distinct species of the same genera, and after fixation, the progeny by these combinations are further mated together.
A further extension of our system which is in itself unique and instructive, is the mating of uncultivated indigenous plants of the same Natural Order as the cultivated varieties. From such combinations most valuable results have been obtained.
For example in Southern Asia there exists a species of wheat botanically known as Triticum spelta. In some districts it is looked upon as an indigenous weed infesting the cultivated crops of wheat.
Under no climatic conditions does the grain of this species shed its seed when ripe, and even in threshing it is not possible to separate the grains, as the spikelets break off at the bases of the glumes, the grains remaining firmly enclosed between the chaff scales.
By mating the varieties of this species with cultivated varieties, new breeds have been produced which will under no conditions shed their seed when ripe, but which thresh out a perfectly clean sample with a much heavier yield per acre than common wheat.
In China there is an indigenous species of oat botanically known as Avena nuda or naked oat. The peculiar feature of this species is that the grains (which are very small) grow without any husk, being protected only by the chaff. The habit of the plant is likewise quite unique, four or five grains being suspended upon a thread-like filament about half an inch long. The mating of this species with cultivated varieties has produced new breeds giving yields 50 to 100 per cent. heavier than the original cultivated parents, with a corresponding decrease in the thickness of the skin.
The wild or land oat, Avena fatua, of Great Britain has likewise been used with marked success in the production of new breeds in conjunction with the cultivated varieties. In the wild oat there is hardiness of constitution, vigour, strength of straw, and remarkable fertility. All these qualities have been retained in the new breeds produced.
Another part of our system is the improvement of existing varieties of agricultural plants. The method is similar to that adopted by the breeder of stock for the improvement of his animals, when fresh blood of the same breed is introduced from some other herd.
By crossing two distinct plants of the same variety the resulting progeny is more vigorous and robust in constitution, whilst the habit and individual character of the variety is maintained.
A year later, these Explanatory Notes come from the Gartons Seed Catalogue for Spring 1901:
FOR over 20 years the work of cross-fertilising crop plants, with the object of producing New and Improved Breeds, has been carried on at Newton-le-Willows in Lancashire. It has there for the first time been demonstrated to Scientific Botanists as well as to Agriculturists that all the corn crops (cereals) and nearly all the other common crops of the farm are self fertilising. In other words, each individual plant provides the pollen which is required in the process of producing seed, to fertilise the female organs of its own flowers. This natural process results in a perfect system of in-breeding which has been going on for an indefinite period, making it possible to grow the different varieties of crops of the same kind in close proximity to each other, and even as mixed crops without any danger of crosses being produced.
If crossing could have occurred in nature it would have been quite impossible to maintain the purity of any variety of crop plant for more than a year or two. As in the Animal Kingdom, the in-breeding of plants tends to the decrease of constitutional vigour, consequently when cross-fertilisation is practised the size and vigour of the selected progeny are increased in a remarkable degree.
Although the natural laws which govern the Animal and the Vegetable Kingdoms bear a very strong resemblance to each other, further points can be realised and greater progress can be made in a limited time with plants than with animals under a system of cross breeding.
Not only have varieties of a given species, but what were formerly regarded as distinct species belonging to the same genus, been successfully mated.
The tendency to sterility in their progeny is overcome by introducing pollen from one or other '01' the original plants, it being the male organs of reproduction that are liable to be absent or defective in the progeny of two extremely divergent parent plants. Many varieties as well as species can thus be blended in the formation of a new breed, but as it is necessary to secure fixity of type in every cross bred plant before it is again used for crossing, the labour and care involved are very considerable.
Attempts at the production of first crosses are not new, as these have been practised for many years by experimenters in the same field, who however stopped short of the point at which the Garton System achieved its greatest results, viz. by compound or multiple crossing. This further stage of the work of cross fertilisation leads to a thorough dislocation of the usual course of the law of inheritance by which "like produces like." In the wilderness of uncertainty and confusion which follows and in which the great majority of the progeny are found to be abortive or inferior, a few choice specimens appear which are grown for a number of years until fixity of type has been secured. These superior and selected specimens are adopted as suitable for cultivation, and a number of them are described in this Catalogue and offered to the public as much superior to the old varieties from which they were derived by the Garton System of Plant Breeding. In making the selections the large quantity and superior quality of the grain, together with great standing power in the straw have been the chief characteristics aimed at, and if these desiderata have been secured in a few of the new breeds to the detriment of the habit of "tillering," the difficulty is readily overcome by providing a liberal seeding.
Some of the most striking and valuable results have been achieved by introducing as progenitors, certain weeds belonging to the same natural order of plants as the cultivated parents. For example, an inferior variety of "spelt" wheat Triticum spelta from Southern Asia, has been employed with excellent results to introduce strength of gluten to the grain, and large yielding and standing power to the crop with immunity from shedding its seed during harvest.
A wild naked Oat, Avena nuda, indigenous to China has been used to produce new breeds which yield in some instances 100 per cent. more than their cultivated parents. Four or five grains are suspended in each spikelet by a thread like filament about half-an-inch long. This peculiar habit of the plant 'has been extended in the progeny and an' accompanying illustration shows a spikelet with no fewer than 14 grains in it.
The hardiness of constitution, standing power of straw, and remarkable fertility of the wild or land oat, Avena fatua, of Great Britain have been successfully introduced, but not without many difficulties, into some of the new breeds.
Some progress has also been made with the improvement of existing varieties of Agricultural plants by introducing pollen from plants of the same variety to increase the vigour of the plant without materially altering its general characteristics.
Source: [ 42 ]
Barley Varieties:
Barley varieties bred and introduced to UK agriculture include Standwell in 1898, Invincible (1899), Zero (1900), Brewer's Favourite (1901), The Maltster (1903), Eclipse (1904), Ideal (1906), 1917 (1918), Admiral Beatty (1920), Triumphant (1927).
Oat Varieties:
Oat varieties bred and introduced to UK agriculture include Abundance in 1892, Pioneer (1899), Tartar King (1899), Waverley (1900), Goldfinder (1901), Storm King (1902), Excelsior (1903), Colossal (1904), Rival (1906), Unversed (1907), Bountiful (1908), The Yielder (1909), The Record (1911), The Leader (1913), Supreme (1915), The Hero (1916), The Captain (1919), Sir Douglas Haig (1920), Marvellous (1921), Superb (1923), Earl Haig (1925), Cropwell (1926), Plentiful (1927), Black Prince (1929), Progress (1930), Unique (1931), Onward (1935), Jubilee (1936), Royal Scot (1940), Spitfire (1945), Early Grey (1946), Forward (1953), Angus (1959).
Wheat Varieties:
Wheat varieties bred and introduced to UK agriculture include White Monarch in 1899, White Pearl (1900), Red King (1900), New Era (1903), Reliance (1909), Victor (1910), Benefactor (1914), Early Cone (1918), The Hawk (1918), Marshal Foch (1919), Rector (1923), Benefactress (1925), Renown (1926), Wilhelmina Regenerated (1928), Gartons No 60 (1932), Gartons Q3 (1933), Redman (1934), Little Tich (1935), Wilma (1936), Warden (1938), Meteor (1941), Pilot (1945), Welcome (1950), Masterpiece (1951), Alpha (1952), Victor II (1953), Ritchie (1957), Apex (1965).
Swede Varieties:
Swede varieties bred and introduced to UK agriculture include Zero in 1900, Lord Derby (1900), Perfection (1900), Monarch (1900), Model (1900), Green Tankard (1901), Keepwell (1902), Cropwell (1903), Superlative (1905), Victory (1907), Incomparable (1907), Warrington (1914), Acme (1914), Magnificent (1917), Viking (1918), Feedwell (1922), White Fleshed (1933), Parkside (1951), Townhead (1951).
Turnip Varieties:
Turnip varieties bred and introduced to UK agriculture include Mammoth Purpletop in 1900, Greentop Scotch Yellow (1900), Hardy Green Globe (1900), Pioneer (1903), Purpletop Long Keeping (1912), Deep Golden Yellow Long Keeping (1912), The Bruce (1917), The Grampian (1920), The Wallace (1935).
Sugar Beet Varieties:
Sugar Beet varieties bred and introduced to UK agriculture include Gartons in 1909, Gartons C (1941) and Gartons Number 632 (1962).
Kale and Kail Varieties:
Kale varieties bred and introduced to UK agriculture include Thousand Headed in 1902, Marrow Stem Kail (1912), Gartons Hybrid (1937) and Hungry Gap (1941).
Kohl Rabi Varieties:
Kohl Rabi varieties bred and introduced to UK agriculture include Large Green in 1902 and Improved Short Top in 1904.
Mangel Varieties:
Mangel varieties bred and introduced to UK agriculture include Large Yellow Intermediate in 1900, Mammoth Long Red (1900), Golden Tankard (1900), Large Yellow Globe (1900), Select Golden Globe (1900), Sugar (1905), Red Intermediate (1905), Devon Yellow Intermediate (1907), Golden Gatepost (1909), Large Red Globe (1910), Large Golden Globe (1910), Nonsuch (1917), Sunrise (1919), White Knight (1922), New Combination (1924), Lemon Globe (1927), Gartons Number 432 (1928), Gartons Number 47 (1931), White Chief (1935), Gartons Number 601 (1960).
Rape Varieties:
Rape varieties bred and introduced to UK agriculture include Broadleaved in 1906, Early Giant (1947) and Late Dwarf (1947).
Herbage Grass Varieties:
Herbage grass varieties bred and introduced to UK agriculture include Hatchmere Perennial Ryegrass in 1899, Ellesmere Perennialized Italian Ryegrass (1907), Pickmere Perennial Ryegrass (1932), Delamere Cocksfoot (1936), Oakmere Timothy (1940), Flaxmere (1952), Gartons Tall Fescue (1955), Marbury Meadow Fescue (1957), Barmere Timothy (1958).
Clover Varieties:
Clover varieties bred and introduced to UK agriculture include Giant Cowgrass in 1898, Perennial Cowgrass (1898), Perennialized Broad Red Clover (1898), Gartons White Clover (1898) and Broad Red Clover (1907).
Field Cabbage Varieties:
Field Cabbage varieties bred and introduced to UK agriculture include Early Ox Heart in 1900, Extra Early Express (1900), Early Drumhead (1900), Selected Drumhead Savoy (1902), Selected Ormskirk Savoy (1902), Gartons Cattle Drumhead (1904), Giant Purple Flat Poll (1917), Utility (1924), Intermediate Drumhead (1924), Gartons Primo (1939).
Field Carrot Varieties:
Field Carrot varieties bred and introduced to UK agriculture include Scarlet Intermediate in 1900, Mid Season Scarlet (1911), Mammoth White (1924), Intermediate Stump Rooted (1935), Red Cored Early Market (1935), Short Stump Rooted (1938), Giant White (1939).
Lupin , Parsnip , Potato , Sprouting Broccoli , Winter Beans and Winter Rye Varieties:
Other crop varieties bred and introduced to UK agriculture include Gartons Lupin in 1922, Gartons Field Parsnips (1902), Gartons Number 12 Potato (1912), Gartons Purple Sprouting Broccoli (1903), Gartons Giant Winter Bean (1922), GS Giant Winter Bean (1950), P/L 14 Giant Winter Bean (1954), Gartons Giant Large Grained Winter Rye (1922). | https://en.wikipedia.org/wiki/Gartons_Limited |
Gary M. Hieftje is an analytical chemist , Distinguished Professor, and the Robert & Marjorie Mann Chair of Chemistry at Indiana University in Bloomington, Indiana . Gary M. Hieftje received his A.B. degree at Hope College in Holland, Michigan in 1964, and his PhD from University of Illinois at Urbana–Champaign in 1969. In 1969, he started his career in teaching and research at Indiana University. Hieftje was named a Distinguished Professor in 1985, and entered emeritus status in 2018. [ 1 ] As of 2018, Dr. Hieftje has been involved in over 600 publications. [ 2 ]
Research in the Hieftje Group mainly focuses on studying and improving the mechanisms and methods of atomic emission and absorption , fluorescence , and mass spectrometry . He also works to develop new methods of analysis for atoms , molecules , and biomolecules . His group even developed an online computer program to control their experiments. Some areas of interest to his research are: finding new applications of lasers, linear response theory , near-infrared correlation methods of analysis, time-resolved luminescence , and fiber-optic sensors . [ 3 ]
Professor Hieftje has authored many books. Perhaps, the most well-known is “Chemical Separations and Measurements - The Theory and Practice of Analytical Chemistry” with colleagues Dennis G. Peters and John M. Hayes published by Saunders in Philadelphia in 1974. | https://en.wikipedia.org/wiki/Gary_M._Hieftje |
Gary J. Patti is an American biochemist known for his research in metabolism and for using mass spectrometry to characterize biological processes. He is the Michael and Tana Powell Professor at Washington University in St. Louis . [ 1 ] He is co-founder and Chief Scientific Officer of Panome Bio [ 2 ] and an Associate Editor for Clinical & Translational Metabolism. [ 3 ] | https://en.wikipedia.org/wiki/Gary_Patti |
Gas-diffusion electrocrystallization ( GDEx ) is an electrochemical process consisting on the reactive precipitation of metal ions in solution (or dispersion) with intermediaries produced by the electrochemical reduction of gases (such as oxygen ), at gas diffusion electrodes . [ 1 ] [ 2 ] [ 3 ] It can serve for the recovery of metals or metalloids into solid precipitates [ 4 ] or for the synthesis of libraries of nanoparticles . [ 1 ]
The gas-diffusion electrocrystallization process was invented in 2014 by Xochitl Dominguez Benetton at the Flemish Institute for Technological Research, in Belgium. The patent for the process granted in Europe was filed in 2015 and its expiration is anticipated in 2036. [ 5 ]
Gas-diffusion electrocrystallization is a process electrochemically driven at porous gas-diffusion electrodes, in which a triple phase boundary is established between a liquid solution , an oxidizing gas , and an electrically conducting electrode . The liquid solution containing dissolved metal ions (e.g., CuCl 2 , ZnCl 2 ) flows through an electrochemical cell equipped with a gas diffusion electrode, making contact with its electrically conducting part (typically a porous layer). The oxidizing gas (e.g., pure O 2 , O 2 in air, CO 2 , etc.) percolates through a hydrophobic layer on the gas diffusion electrode, acting as a cathode. After the gas diffuses to the electrically conducting layer acting as an electrocatalyst (e.g., hydrophilic activated carbon), the gas is electrochemically reduced . For instance, by imposing specific cathodic polarization conditions (e.g., −0.145 VSHE O 2 is reduced, to H 2 O 2 in a 2 electron (2 e – ) transfer process and H 2 O in a 4 electron (4 e – ) transfer process. OH – are also produced in the process. As this happens, abrupt local pH and local electrolyte redox potential changes arise within the cathode porosity. As the hydroxyl ions spread to the bulk electrolyte, systematic pH increases become consistently manifest in the electrolyte bulk. In due course, low amounts of H 2 O 2 are generated. In steady state, a reaction front is fully developed throughout the hydrodynamic boundary layer . This creates local saturation conditions at the electrochemical interface, where metal ions precipitate in metastable or stable phases depending on the operational variables. When oxygen is the oxidizing gas, the mechanism for gas-diffusion electrocrystallization has been explained as an oxidation-assisted alkaline precipitation using gas-diffusion electrodes. [ 6 ]
In 2020, the gas-diffusion electrocrystallization process was presented as a great EU-funded innovation by the Innovation Radar of the European Commission , for its application on the secondary recovery of platinum group metals. [ 7 ] | https://en.wikipedia.org/wiki/Gas-diffusion_electrocrystallization |
The gas-generator cycle , also called open cycle , is one of the most commonly used power cycles in bipropellant liquid rocket engines.
Propellant is burned in a gas generator (or "preburner") and the resulting hot gas is used to power the propellant pumps before being exhausted overboard and lost. Because of this loss, this type of engine is termed open cycle .
The gas generator cycle exhaust products pass over the turbine first. Then they are expelled overboard. They can be expelled directly from the turbine, or are sometimes expelled into the nozzle (downstream from the throat) for a small gain in efficiency.
The main combustion chamber does not use these products. This explains the name of the open cycle. The major disadvantage is that this propellant contributes little to no thrust because they are not injected into the combustion chamber. The major advantage of the cycle is reduced engineering complexity compared to the staged combustion (closed) cycle . | https://en.wikipedia.org/wiki/Gas-generator_cycle |
Gas-pak is a method used in the production of an anaerobic environment. It is used to culture bacteria which die or fail to grow in the presence of oxygen ( anaerobes ).
These are commercially available, disposable sachets containing a dry powder or pellets, which, when mixed with water and kept in an appropriately sized airtight jar, produce an atmosphere free of elemental oxygen gas (O 2 ). They are used to produce an anaerobic culture in microbiology . [ 2 ] [ 3 ] [ 4 ] It is a much simpler technique than the McIntosh and Filde's anaerobic jar where one needs to pump gases in and out.
The addition of a Dicot Catalyst may be required to initiate the reaction.
These chemicals react with water to produce hydrogen and carbon dioxide along with sodium citrate (C 3 H 5 O(COONa) 3 ) and water as byproducts [1] . Again, hydrogen and oxygen reacting on a catalyst like Palladiumised alumina (supplied separately) combine to form water.
The medium , the gas-pak sachet (opened and with water added) and an indicator are placed in an air-tight gas jar which is incubated at the desired temperature . The indicator tells whether the environment was indeed oxygen free or not.
The chemical indicator generally used for this purpose is "chemical methylene blue solution" that since synthesis has never been exposed to elemental oxygen. It is colored deep blue on oxidation in presence of atmospheric oxygen in the jar, but will become colorless when oxygen is gone, and anaerobic conditions are achieved. | https://en.wikipedia.org/wiki/Gas-pak |
When oil is produced to surface temperature and pressure it is usual for some natural gas to come out of solution. The gas/oil ratio (GOR) is the ratio of the volume of gas ("scf") that comes out of solution to the volume of oil — at standard conditions.
In reservoir simulation gas/oil ratio is usually abbreviated R s {\displaystyle R_{s}} .
A point to check is whether the volume of oil is measured before or after the gas comes out of solution, since the remaining oil volume will decrease when the gas comes out.
In fact, gas dissolution and oil volume shrinkage will happen at many stages during the path of the hydrocarbon stream from reservoir through the wellbore and processing plant to export. For light oils and rich gas condensates the ultimate GOR of export streams is strongly influenced by the efficiency with which the processing plant strips liquids from the gas phase. Reported GORs may be calculated from export volumes, which may not be at standard conditions.
The GOR is a dimensionless ratio (volume per volume) in metric units, but in field units, it is usually quoted in cubic feet of gas (at standard conditions: 0°C, 100 kPa) per barrel of oil or condensate, scf/bbl.
In the states of Texas and Pennsylvania, the statutory definition of a gas well is one where the GOR is greater than 100,000 ft 3 /bbl or 100 Kcf/bbl.
The state of New Mexico also designates a gas well as having over 100 MCFG per barrel. [ 1 ]
The Oklahoma Geological Survey in 2015 published a map that displays gas wells with greater than 20 MCFG per barrel of oil. [ 2 ] They go on to display oil wells with GOR of less than 5 MCFG/BBL and oil and gas wells between these limits.
The EPA's 2016 Information Collection Request for Oil and Gas Facilities (EPA ICR No. 2548.01, OMB Control No. 2060-NEW) divided well types into five categories:
1. Heavy Oil (GOR ≤ 300 scf/bbl)
2. Light Oil (GOR 300 < GOR ≤ 100,000 scf/bbl)
3. Wet Gas (100,000 < GOR ≤1,000,000 scf/bbl)
4. Dry Gas (GOR > 1,000,000 scf/bbl)
5. Coal Bed Methane. | https://en.wikipedia.org/wiki/Gas/oil_ratio |
Gas Safe Register is the official gas registration body for the United Kingdom , Isle of Man and Guernsey , appointed by the relevant Health and Safety Authority for each area. By law all gas engineers must be on the Gas Safe Register. [ 1 ]
Gas Safe Register replaced CORGI as the gas registration body in Great Britain and Isle of Man on 1 April 2009 and Northern Ireland and Guernsey on 1 April 2010. [ 2 ] [ 3 ]
The purpose of the Gas Safe Register is to protect the public from unsafe gas work. It does this in two main ways, operation of the Register itself e.g. ensuring that the list of competent and qualified engineers is accurate and up-to-date, inspecting the work of Gas Safe registered engineers and investigating reports of illegal gas work. The second area is to conduct public awareness campaigns to raise awareness of gas safety issues. [ 4 ] [ 5 ]
A 2006 review by the Health and Safety Executive identified ‘a case for change’ to the CORGI scheme that had been registering gas installers since 1991. In a competitive tender , Capita was appointed to overhaul the scheme and operate it for 10 years from April 2009 to March 2019, and this was renewed in 2018 to cover the five year period from April 2019 to March 2024. [ 6 ]
Before applying to register engineers will need relevant qualifications and evidence of competence. Once an engineer has gained the relevant qualifications and the required evidence, this information will be passed to Gas Safe Register. At present, Gas Safe Register only accepts the ACS , NVQ or SVQ qualifications. [ 7 ] Every Gas Safe registered business renews their registration on an annual basis, and updates their qualifications every 5 years.
The scheme is administered by Capita Group on behalf of the Health and Safety Executive . [ 5 ] in the United Kingdom Mainland and for the Health and Safety Executive Northern Ireland. The contract differs in Northern Ireland in relation to the main contract for mainland of the United Kingdom.
Gas Safe Register deals with all aspects of the downstream gas industry covered by the following regulations: [ 8 ]
The regulations cover both piped natural gas and liquefied petroleum gas (LPG).
In 2011 Gas Safe Register launched a consumer awareness initiative called Gas Safety Week, with the aim of focusing the public's attention on gas safety issues and helping raise awareness of the dangers of carbon monoxide (CO) poisoning. Since 2011, the campaign has grown significantly and has become an industry-wide initiative supported by the large energy providers, retailers, charities and Gas Safe registered engineers. [ 9 ] | https://en.wikipedia.org/wiki/Gas_Safe_Register |
The Gas Safety (Installation and Use) Regulations 1998 ( ISBN 0 11 079655 1 ) is a United Kingdom statutory instrument regulating various activities relating to the safety of installations and appliances using natural gas and liquefied petroleum gas (LPG).
Note that there is no reference in the UK law or in HSE to "landlord's gas safety certificate" - only to having a "record" of an "annual gas safety check". However the following is generally required by *UK law.
The regulations cover various aspects of the supply and use of gas, and qualifications and duties of people involved with doing so. Provisions of the regulations with which the public is most familiar are:
The latter requires those carrying out gas work to be " competent " and also that if they are doing gas work as an employee or self-employed person they should be "a member of a class of persons approved for the time being by the Health and Safety Executive". The "class of persons" currently means those registered with Gas Safe Register .
This article relating to law in the United Kingdom , or its constituent jurisdictions, is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gas_Safety_(Installation_and_Use)_Regulations_1998 |
Gas blending is the process of mixing gases for a specific purpose where the composition of the resulting mixture is defined, and therefore, controlled.
A wide range of applications include scientific and industrial processes, food production and storage and breathing gases.
Gas mixtures are usually specified in terms of molar gas fraction (which is closely approximated by volumetric gas fraction for many permanent gases ): by percentage, parts per thousand or parts per million. Volumetric gas fraction converts trivially to partial pressure ratio, following Dalton's law of partial pressures . Partial pressure blending at constant temperature is computationally simple, and pressure measurement is relatively inexpensive, but maintaining constant temperature during pressure changes requires significant delays for temperature equalization. Blending by mass fraction is unaffected by temperature variation during the process, but requires accurate measurement of mass or weight, and calculation of constituent masses from the specified molar ratio. Both partial pressure and mass fraction blending are used in practice.
Shielding gases are inert or semi-inert gases used in gas metal arc welding and gas tungsten arc welding to protect the weld area from oxygen and water vapour, which can reduce the quality of the weld or make the welding more difficult.
Gas metal arc welding (GMAW), or metal inert gas (MIG) welding, is a process that uses a continuous wire feed as a consumable electrode and an inert or semi-inert gas mixture to protect the weld from contamination. [ 1 ] Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a nonconsumable tungsten electrode, an inert or semi-inert gas mixture, and a separate filler material. [ 2 ]
Modified atmosphere packaging preserves fresh produce to improve delivered quality of the product and extend its life. The gas composition used to pack food products depends on the product. A high oxygen content helps to retain the red colour of meat, while low oxygen reduces mould growth in bread and vegetables. [ 3 ]
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration . The essential component for any breathing gas is a partial pressure of oxygen of between roughly 0.16 and 1.60 bar at the ambient pressure . The oxygen is usually the only metabolically active component unless the gas is an anaesthetic mixture. Some of the oxygen in the breathing gas is consumed by the metabolic processes, and the inert components are unchanged, and serve mainly to dilute the oxygen to an appropriate concentration, and are therefore also known as diluent gases.
Gas blending for scuba diving is the filling of diving cylinders with non-air breathing gases such as nitrox , trimix and heliox . Use of these gases is generally intended to improve overall safety of the planned dive, by reducing the risk of decompression sickness and/or nitrogen narcosis , and may improve ease of breathing .
Gas blending for surface supplied and saturation diving may include the filling of bulk storage cylinders and bailout cylinders with breathing gases, but it also involves the mixing of breathing gases at lower pressure which are supplied directly to the diver or to the hyperbaric life-support system . Part of the operation of the life-support system is the replenishment of oxygen used by the occupants, and removal of the carbon dioxide waste product by the gas conditioning unit. This entails monitoring of the composition of the chamber gas and periodic addition of oxygen to the chamber gas at the internal pressure of the chamber.
The gas mixing unit is part of the life support equipment of a saturation system, along with other components which may include bulk gas storage, compressors, helium recovery unit, bell and diver hot water supply, gas conditioning unit and emergency power supply [ 4 ]
The anesthetic machine is used to blend breathing gas for patients under anesthesia during surgery. The gas mixing and delivery system lets the anesthetist control oxygen fraction, nitrous oxide concentration and the concentration of volatile anesthetic agents. [ 5 ] The machine is usually supplied with oxygen (O 2 ) and nitrous oxide (N 2 O) from low pressure lines and high pressure reserve cylinders, and the metered gas is mixed at ambient pressure, after which additional anesthetic agents may be added by a vaporizer, and the gas may be humidified. Air is used as a diluent to decrease oxygen concentration. In special cases other gases may also be added to the mixture. These may include carbon dioxide (CO 2 ), used to stimulate respiration, and helium (He) to reduce resistance to flow or to enhance heat transfer. [ 6 ]
Gas mixing systems may be mechanical, using conventional rotameter banks, or electronic, using proportional solenoids or pulsed injectors, and control may be manual or automatic. [ 5 ]
Providing reactive gaseous materials for chemical production processes in the required ratio
Protective gas mixtures may be used to exclude air or other gases from the surface of sensitive materials during processing.
Examples include melting of reactive metals such as magnesium, and heat treatment of steels.
Calibration gases :
Calibration gas mixtures are generally produced in batches by gravimetric or volumetric methods.
The gravimetric method uses sensitive and accurately calibrated scales to weigh the amounts of gases added into the cylinder. Precise measurement is required as inaccuracy or impurities can result in incorrect calibration. The container for calibration gas must be as close to perfectly clean as practicable. The cylinders may be cleaned by purging with high purity nitrogen, the vacuumed. For particularly critical mixtures the cylinder may be heated while being vacuumed to facilitate removal of any impurities adhering to the walls. [ 7 ]
After filling, the gas mixture must be thoroughly mixed to ensure that all components are evenly distributed throughout the container to prevent possible variations on composition within the container. This is commonly done by rolling the container horizontally for 2 to 4 hours. [ 7 ]
Several methods are available for gas blending. These may be distinguished as batch methods and continuous processes.
Batch gas blending requires the appropriate amounts of the constituent gases to be measured and mixed together until the mixture is homogeneous. The amounts are based on the mole (or molar) fractions, but measured either by volume or by mass. Volume measurement may be done indirectly by partial pressure, as the gases are often sequentially decanted into the same container for mixing, and therefore occupy the same volume. Weight measurement is generally used as a proxy for mass measurement as acceleration can usually be considered constant.
The mole fraction is also called the amount fraction, and is the number of molecules of a constituent divided by the total number of all molecules in the mixture. For example, a 50% oxygen, 50% helium mixture will contain approximately the same number of molecules of oxygen and helium. As both oxygen and helium approximate ideal gases at pressures below 200 bar, each will occupy the same volume at the same pressure and temperature, so they can be measured by volume at the same pressure, then mixed, or by partial pressure when decanted into the same container.
The mass fraction can be calculated from the molar fraction by multiplying the molar fraction by the molecular mass for each constituent, to find a constituent mass, and comparing it to the summed masses of all the constituents. The actual mass of each constituent needed for a mixture is calculated by multiplying the mass fraction by the desired mass of the mixture.
Also known as volumetric blending. This must be done at constant temperature for best accuracy, though it is possible to compensate for temperature changes in proportion to the accuracy of the temperature measured before and after each gas is added to the mixture.
Partial pressure blending is commonly used for breathing gases for diving. The accuracy required for this application can be achieved by using a pressure gauge which reads accurately to 0.5 bar, and allowing the temperature to equilibrate after each gas is added.
Also known as gravimetric blending. This is relatively unaffected by temperature, and accuracy depends on the accuracy of mass measurement of the constituents.
Mass fraction blending is used where great accuracy of the mixture is critical, such as in calibration gases. The method is not suited to moving platforms where the accelerations can cause inaccurate measurement, and therefore is unsuitable for mixing diving gases on vessels.
Continuous gas blending is used for some surface supplied diving applications, and for many chemical processes using reactive gas mixtures, particularly where there may be a need to alter the mixture during the operation or process.
These processes start with a mixture of gases, usually air, and reduce the concentration of one or more of the constituents. These processes can be used for the production of Nitrox for scuba diving and deoxygenated air for blanketing purposes.
Gas mixtures must generally be analysed either in process or after blending for quality control. This is particularly important for breathing gas mixtures where errors can affect the health and safety of the end user.
Oxygen content is relatively simple to monitor using electro-galvanic cells and these are routinely used in the underwater diving industry for this purpose, though other methods may be more accurate and reliable. | https://en.wikipedia.org/wiki/Gas_blending |
A gas cabinet is a metallic enclosure which is used to provide local exhaust ventilation system for virtually all of the gases used or generated in the semiconductor, solar, MEMS, NANO, solar PV, manufacturing and other advanced technologies. [ 1 ]
The primary purpose of gas cabinets is to contain potential leaks in piping and fittings at the cylinder connection. The cabinet must be exhausted by a specifically designed fan and exhaust system. The cabinet exhaust system draws leaking hazardous gasses out of the cabinet. In the case of a flammable gas the cabinet will contain the flame for a period of time. [ 2 ] One can use a newly reconditioned cabinet as well as non-reconditioned used gas cabinets depending on their requirements. [ 3 ]
There are a variety of gas cabinets available in the market in different gas cylinder configurations, such as 1, 2 and 3 bottle designs. They can be either new, used, or reconditioned. A gas cylinder cabinet can have many features depending on the specific gas. These features include gas sensor, sprinkler head, excess flow sensor, automatic operation with automatic purging and excess pressure sensor. [ citation needed ]
They should meet the Uniform Fire Code Specifications and the National Fire Protection Association. They need to adhere to the Compressed Gas Association and Semiconductor Equipment & Materials Institute codes. It is also important to know whether the cabinet is OSHA compliant. OSHA offers additional safety precautions involving the use of gas cabinets. In the absence of finite specifications or unknowns the user or designer should seek the assistance of an impartial consultant. [ 4 ]
Reconditioned gas cabinets can be more useful than non-reconditioned used gas cabinets because of the thorough process used in professionally reconditioning and testing to ensure all systems meet manufacturer’s specifications. Different types of gas cabinets can be used, depending on the gas type in the cylinder. Automatic gas cabinets with multiple sensors are useful and fulfill many other requirements.
A gas cabinet can also be manufactured specifically for a company's needs and at lower cost. It is required that a gas cabinet is used for fire safety for gas cylinders. The requirements vary by state. Many states have no advanced regulations for hazardous industrial gasses since there is little or no use of such gasses in that state. [ 5 ]
The gas cabinets are categorized into four popular types based on the type of gas. [ 6 ] The categories are:
These gas cabinets are used for inert, non-reactive and non-toxic gases. There are automatic gas cabinets also available and thus these cabinets are less useful when compared to automatic cabinets.
These cabinets are available for corrosive, toxic and reactive gases. They provide safe and clean delivery of ultra-high purity gases. Such systems are designed to monitor a huge number of facility inputs and process sensors as per requirements.
These gas cabinets are useful when uninterrupted gas flow is required. Auto changeover gas cabinets can be defined by mass or pressure inputs. There is software also available for multiple cylinder scales on each joint or bank. Purge down and purge up processes can also be performed without any interruption of connected cylinders. [ citation needed ]
The port and valve specifications for gas cabinets and distribution systems are an important part of the selection process.
Gas cabinets may be distinguished by the types of valves used to control flow.
Manual valves. Valves are manually adjusted or deployed via a control knob, lever, or other manual device.
Solenoid valves. Valves are opened and closed via a solenoid magnet deployed by an electrical signal.
Air pilot valves. Valves are deployed via a pneumatic signal.
Ports are openings in the manifold or distribution system where the inlet and outlet connections are produced. Each opening is either an inlet (supply) port or an outlet port. The number of each corresponds to the requirements of the application.
The quantity of supply ports specifies the number of independent fluid supplies that could be interfaced with the manifold or manifold system.
The number of outlet ports establishes the number of outlets in the system. This is frequently specified as number of ports or valves that are or can be attached to the manifold. For example, an 8-point manifold has 8 ports or valves.
Ports are sized based roughly on tube or pipe size with some important choices. For industrial gases it is possible to purchase manifolds made of Stainless steel pipe or copper and brass although both these materials are giving way to Stainless steel tubing. (Note differences between Tubing and Pipe). Connection choices might be NPT, VCO, Flare or other
types.
For gas service that is "Clean For Oxygen Service (CFOS)" or for Ultra Pure service, manifolds and change over assemblies are typically made from 1/4" OD, 316 L, Electropolished tubing (the ID is Electropolished). The fittings used for ports and other connections are exclusively the "VCR" fitting. Training is needed to properly handle and install VCR connections using a variety of non-resuseable crushable metal gasket materials. Metal gaskets are essential in order to achieve high helium leak ratings.
The specifications for a gas cabinet detail everything from gas flow rates to the physical size of the system. [ citation needed ]
Pressure describes the amount of force exerted on a system by the contained and pressurized gas. Most compressed gases will not exceed 2,000 to 2,640 pounds per square inch gage (psig), but some can reach pressures of 6,000 psig. The system's weakest point determines the pressure limit, so any parts weakened by heat, corrosion, or stress may potentially lower the maximum pressure of the system or cause the vessel to rupture. Many times this is at the point of welds. [ citation needed ]
Flow rate details the maximum rate of flow of the gas through the operation, typically measured in standard cubic feet per minute (scfm).
Temperature range is the full mandated range of safe ambient or fluid operating temperatures, given in degrees Fahrenheit or degrees Celsius.
Size dimensions specify the physical size of the gas cabinet, distribution system, or its components.
Cabinet size - Indicates the physical size of the gas cabinet or the body of the distribution system.
Port/tube size - Indicates the physical size of the tubing or exhaust port connections in the system, typically given in inches based on a sizing standard such as National Pipe Thread (NPT). Sizing is important, as an undersized tube line will result in high pressure drops, while an oversized line will be unnecessarily expensive to install.
The materials used to construct the gas cabinet are an important part of proper system selection. The materials used for the casing and outer parts must have adequate structural strength, while the materials for the gas handling components must be compatible with the media, temperature requirements, and pressure ratings to prevent leakage, rupture, or contamination.
A light and fairly corrosion resistant metal which is most often anodized for increased corrosion and wear resistance. Aluminum is never used for tubing or fittings in modern industrial gas control & distribution systems since 316L stainless steel (optimum choice) is so available. Aluminum is not an ideal choice for purity. Aluminum in any form is never used for ultra pure industrial gas systems.
A soft, ductile metal with low hardness and excellent corrosion resistance. Copper is used commonly in tubes and pipes for its inertness and resistance to corrosion. Copper can be used for low air, oxygen and other inert non-critical gases such as medical CFOS systems. For ultra pure gasses 316L Stainless steel remains the optimum choice for many reasons.
Any of numerous thermoplastic or thermosetting polymers of high molecular weight. Different grades (such as nylon, acetal, and polycarbonate) have varying properties, but most have strong chemical and corrosion resistance.
General purpose industrial metal with high physical strength and hardness. Steel is typically coated or finished to increase its corrosion resistance properties. Steel is used in the petroleum and petro-chemical industries.
316L Stainless steel became industry standard for fittings, piping and controls in gas cabinets and distribution systems in the early 1980s. The material is further improved by electropolishing to render wetted surfaces extremely impervious to the most reactive gasses creating a non-shedding surface. A large industry has grown around supplying these ultra-specialized components and materials. | https://en.wikipedia.org/wiki/Gas_cabinet |
Gas carbon , or retort carbon , is a form of carbon that is obtained when the destructive distillation of coal is done or when coal gas or petroleum products are heated at high temperatures in a closed container. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] It appears as a compact, amorphous, gray , crystalline solid left by chemical vapour deposition on the walls of a container or retort . It is a good conductor of heat and electricity, similar to graphite . Unlike graphite, it does not leave marks on paper. [ 6 ]
Applications have included battery plates, [ 4 ] and in arc lamps . [ 4 ] It was also used in early microphones . [ 7 ]
Houston in 1883 described its use in arc lighting: [ 5 ]
For the manufacture of the carbon electrode, the gas carbon is finely pulverized, washed, and mixed with lamp-black or other pure, finely divided carbon, and made into a paste with syrup, tar, or other carbonizable liquid. It is then forced through an opening in a strong cylinder by hydraulic pressure, and baked at a red heat for several hours, while surrounded by sand or similar material to exclude the air. The carbons are then allowed to cool, and are removed, and again soaked and burned, in order to increase their density and electrical conducting power.
while Atkinson noted in 1898: [ 8 ]
For [electric arc carbon] especially, large pieces are in demand, and command a better price... It is, generally speaking, too valuable for use as fuel.
It has a specific gravity of around 2.35 to 2.4. [ 4 ] [ 8 ]
This industry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gas_carbon |
A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centrifugal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of uranium-235 ( 235 U) from uranium-238 ( 238 U). The gas centrifuge was developed to replace the gaseous diffusion method of 235 U extraction. High degrees of separation of these isotopes relies on using many individual centrifuges arranged in series that achieve successively higher concentrations. This process yields higher concentrations of 235 U while using significantly less energy compared to the gaseous diffusion process.
Suggested in 1919, the centrifugal process was first successfully performed in 1934. American scientist Jesse Beams and his team at the University of Virginia developed the process by separating two chlorine isotopes through a vacuum ultracentrifuge . It was one of the initial isotopic separation means pursued during the Manhattan Project , more particularly by Harold Urey and Karl P. Cohen , but research was discontinued in 1944 as it was felt that the method would not produce results by the end of the war, and that other means of uranium enrichment ( gaseous diffusion and electromagnetic separation ) had a better chance of success in the short term. This method was successfully used in the Soviet nuclear program , making the Soviet Union the most effective supplier of enriched uranium. Franz Simon , Rudolf Peierls , Klaus Fuchs and Nicholas Kurti made important contributions to the centrifugal process.
Paul Dirac made important theoretical contributions to the centrifugal process during World War II ; [ 1 ] [ 2 ] Dirac developed the fundamental theory of separation processes that underlies the design and analysis of modern uranium enrichment plants. [ 3 ] In the long term, especially with the development of the Zippe-type centrifuge , the gas centrifuge has become a very economical mode of separation, using considerably less energy than other methods and having numerous other advantages.
Research in the physical performance of centrifuges was carried out by the Pakistani scientist Abdul Qadeer Khan in the 1970s–80s, using vacuum methods for advancing the role of centrifuges in the development of nuclear fuel for Pakistan's atomic bomb . [ 4 ] Many of the theorists working with Khan were unsure that either gaseous and enriched uranium would be feasible on time. [ 5 ] One scientist recalled: "No one in the world has used the [gas] centrifuge method to produce military-grade uranium.... This was not going to work. He was simply wasting time." [ 5 ] In spite of skepticism, the program was quickly proven to be feasible. Enrichment via centrifuge has been used in experimental physics, and the method was smuggled to at least three different countries by the end of the 20th century. [ 4 ] [ 5 ]
The centrifuge relies on the force resulting from centrifugal acceleration to separate molecules according to their mass and can be applied to most fluids. [ 6 ] The dense (heavier) molecules move towards the wall, and the lighter ones remain close to the center. The centrifuge consists of a rigid body rotor rotating at full period at high speed. [ 7 ] Concentric gas tubes located on the axis of the rotor are used to introduce feed gas into the rotor and extract the heavier and lighter separated streams. [ 7 ] For 235 U production, the heavier stream is the waste stream and the lighter stream is the product stream. Modern Zippe-type centrifuges are tall cylinders spinning on a vertical axis. A vertical temperature gradient can be applied to create a convective circulation rising in the center and descending at the periphery of the centrifuge. Such a countercurrent flow can also be stimulated mechanically by the scoops that take out the enriched and depleted fractions. Diffusion between these opposing flows increases the separation by the principle of countercurrent multiplication .
In practice, since there are limits to how tall a single centrifuge can be made, several such centrifuges are connected in series. Each centrifuge receives one input line and produces two output lines, corresponding to light and heavy fractions . The input of each centrifuge is the product stream of the previous centrifuge. This produces an almost pure light fraction from the product stream of the last centrifuge and an almost pure heavy fraction from the waste stream of the first centrifuge.
The gas centrifugation process uses a unique design that allows gas to constantly flow in and out of the centrifuge. Unlike most centrifuges which rely on batch processing , the gas centrifuge uses continuous processing, allowing cascading in which multiple identical processes occur in succession. The gas centrifuge consists of a cylindrical rotor, a casing, an electric motor, and three lines for material to travel. The gas centrifuge is designed with a casing that completely encloses the centrifuge. [ 4 ] The cylindrical rotor is located inside the casing, which is evacuated of all air to produce a near frictionless rotation when operating. The motor spins the rotor, creating the centrifugal force on the components as they enter the cylindrical rotor. This force acts to separate the molecules of the gas, with heavier molecules moving towards the wall of the rotor and the lighter molecules towards the central axis. There are two output lines, one for the fraction enriched in the desired isotope (in uranium separation, this is 235 U), and one depleted of that isotope. The output lines take these separations to other centrifuges to continue the centrifugation process. [ 8 ] The process begins when the rotor is balanced in three stages. [ 9 ] Most of the technical details on gas centrifuges are difficult to obtain because they are shrouded in "nuclear secrecy". [ 9 ]
The early gas centrifuges used in the UK used an alloy body wrapped in epoxy-impregnated glass fibre. Dynamic balancing of the assembly was accomplished by adding small traces of epoxy at the locations indicated by the balancing test unit. The motor was usually a pancake type located at the bottom of the cylinder. The early units were typically around 2 metres long, but subsequent developments gradually increased the length. The present generation are over 4 metres in length. The bearings are gas-based devices, as mechanical bearings would not survive at the normal operating speeds of these centrifuges.
A section of centrifuges would be fed with variable-frequency alternating current from an electronic (bulk) inverter, which would slowly ramp them up to the required speed, generally in excess of 50,000 rpm. One precaution was to quickly get past frequencies at which the cylinder was known to suffer resonance problems. The inverter is a high-frequency unit capable of operating at frequencies around 1 kilohertz. The whole process is normally silent; if a noise is heard coming from a centrifuge, it is a warning of failure (which normally occurs very quickly). The design of the cascade normally allows for the failure of at least one centrifuge unit without compromising the operation of the cascade. The units are normally very reliable, with early models having operated continuously for over 30 years.
Later models have steadily increased the rotation speed of the centrifuges, as it is the velocity of the centrifuge wall that has the most effect on the separation efficiency. A feature of the cascade system of centrifuges is that it is possible to increase plant throughput incrementally, by adding cascade "blocks" to the existing installation at suitable locations, rather than having to install a completely new line of centrifuges.
The simplest gas centrifuge is the concurrent centrifuge, where separative effect is produced by the centrifugal effects of the rotor's rotation. In these centrifuges, the heavy fraction is collected at the periphery of the rotor and the light fraction from nearer the axis of rotation. [ 10 ]
Inducing a countercurrent flow uses countercurrent multiplication to enhance the separative effect. A vertical circulating current is set up, with the gas flowing axially along the rotor walls in one direction and a return flow closer to the center of the rotor. The centrifugal separation continues as before (heavier molecules preferentially moving outwards), which means that the heavier molecules are collected by the wall flow, and the lighter fraction collects at the other end. In a centrifuge with downward wall flow, the heavier molecules collect at the bottom. The outlet scoops are then placed at the ends of the rotor cavity, with the feed mixture injected along the axis of the cavity (ideally, the injection point is at the point where the mixture in the rotor is equal to the feed [ 11 ] ).
This countercurrent flow can be induced mechanically or thermally, or a combination. In mechanically induced countercurrent flow, the arrangement of the (stationary) scoops and internal rotor structures are used to generate the flow. [ 12 ] A scoop interacts with the gas by slowing it, which tends to draw it into the centre of the rotor. The scoops at each end induce opposing currents, so one scoop is protected from the flow by a "baffle": a perforated disc within the rotor which rotates along with the gas—at this end of the rotor, the flow will be outwards, towards the rotor wall. Thus, in a centrifuge with a baffled top scoop, the wall flow is downwards, and heavier molecules are collected at the bottom. Thermally induced convection currents can be created by heating the bottom of the centrifuge and/or cooling the top end.
The separative work unit (SWU) is a measure of the amount of work done by the centrifuge and has units of mass (typically kilogram separative work unit ). The work W S W U {\displaystyle W_{\mathrm {SWU} }} necessary to separate a mass F {\displaystyle F} of feed of assay x f {\displaystyle x_{f}} into a mass P {\displaystyle P} of product assay x p {\displaystyle x_{p}} , and tails of mass T {\displaystyle T} and assay x t {\displaystyle x_{t}} is expressed in terms of the number of separative work units needed, given by the expression
The separation of uranium requires the material in a gaseous form; uranium hexafluoride (UF 6 ) is used for uranium enrichment . Upon entering the centrifuge cylinder, the UF 6 gas is rotated at a high speed. The rotation creates a strong centrifugal force that draws more of the heavier gas molecules (containing the 238 U) toward the wall of the cylinder, while the lighter gas molecules (containing the 235 U) tend to collect closer to the center. The stream that is slightly enriched in 235 U is withdrawn and fed into the next higher stage, while the slightly depleted stream is recycled back into the next lower stage.
For some uses in nuclear technology, the content of zinc-64 ( 64 Zn) in zinc metal has to be lowered in order to prevent formation of radioisotopes by its neutron activation . Diethyl zinc is used as the gaseous feed medium for the centrifuge cascade. An example of a resulting material is depleted zinc oxide , used as a corrosion inhibitor . | https://en.wikipedia.org/wiki/Gas_centrifuge |
Gas chromatography ( GC ) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition . Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture. [ 1 ] In preparative chromatography , GC can be used to prepare pure compounds from a mixture. [ 2 ] [ 3 ]
Gas chromatography is also sometimes known as vapor-phase chromatography ( VPC ), or gas–liquid partition chromatography ( GLPC ). These alternative names, as well as their respective abbreviations, are frequently used in scientific literature. [ 2 ]
Gas chromatography is the process of separating compounds in a mixture by injecting a gaseous or liquid sample into a mobile phase, typically called the carrier gas, and passing the gas through a stationary phase. The mobile phase is usually an inert gas or an unreactive gas such as helium , argon , nitrogen or hydrogen . [ 1 ] The stationary phase can be solid or liquid, although most GC systems today use a polymeric liquid stationary phase. [ 4 ] The stationary phase is contained inside of a separation column. Today, most GC columns are fused silica capillaries with an inner diameter of 100–320 micrometres (0.0039–0.0126 in) and a length of 5–60 metres (16–197 ft). The GC column is located inside an oven where the temperature of the gas can be controlled and the effluent coming off the column is monitored by a suitable detector. [ 1 ]
A gas chromatograph is made of a narrow tube, known as the column , through which the vaporized sample passes, carried along by a continuous flow of inert or nonreactive gas. Components of the sample pass through the column at different rates, depending on their chemical and physical properties and the resulting interactions with the column lining or filling, called the stationary phase . The column is typically enclosed within a temperature controlled oven. As the chemicals exit the end of the column, they are detected and identified electronically. [ 1 ]
Chromatography dates to 1903 in the work of the Russian scientist, Mikhail Semenovich Tswett , [ 5 ] who separated plant pigments via liquid column chromatography.
The invention of gas chromatography is generally attributed to Anthony T. James and Archer J.P. Martin . [ 6 ] [ 7 ] Their gas chromatograph used partition chromatography as the separating principle, rather than adsorption chromatography . The popularity of gas chromatography quickly rose after the development of the flame ionization detector. [ 8 ] Martin and another one of their colleagues, Richard Synge , with whom he shared the 1952 Nobel Prize in Chemistry , had noted in an earlier paper [ 9 ] that chromatography might also be used to separate gases. Synge pursued other work while Martin continued his work with James.
German physical chemist Erika Cremer in 1947 together with Austrian graduate student Fritz Prior developed what could be considered the first gas chromatograph that consisted of a carrier gas, a column packed with silica gel, and a thermal conductivity detector. They exhibited the chromatograph at ACHEMA in Frankfurt, but nobody was interested in it. [ 10 ] N.C. Turner with the Burrell Corporation introduced in 1943 a massive instrument that used a charcoal column and mercury vapors. Stig Claesson of Uppsala University published in 1946 his work on a charcoal column that also used mercury. [ 10 ] Gerhard Hesse, while a professor at the University of Marburg /Lahn decided to test the prevailing opinion among German chemists that molecules could not be separated in a moving gas stream. He set up a simple glass column filled with starch and successfully separated bromine and iodine using nitrogen as the carrier gas. He then built a system that flowed an inert gas through a glass condenser packed with silica gel and collected the eluted fractions. [ 10 ] Courtenay S.G Phillips of Oxford University investigated separation in a charcoal column using a thermal conductivity detector. He consulted with Claesson and decided to use displacement as his separating principle. After learning about the results of James and Martin, he switched to partition chromatography. [ 10 ]
Early gas chromatography used packed columns, made of block 1–5 m long, 1–5 mm diameter, and filled with particles. The resolution of packed columns was improved by the invention of capillary column, in which the stationary phase is coated on the inner wall of the capillary. [ 6 ]
The autosampler provides the means to introduce a sample automatically into the inlets. Manual insertion of the sample is possible but is no longer common. Automatic insertion provides better reproducibility and time-optimization.
Different kinds of autosamplers exist. Autosamplers can be classified in relation to sample capacity (auto-injectors vs. autosamplers, where auto-injectors can work a small number of samples), to robotic technologies (XYZ robot [ 11 ] vs. rotating robot – the most common), or to analysis:
The column inlet (or injector) provides the means to introduce a sample into a continuous flow of carrier gas. The inlet is a piece of hardware attached to the column head.
Common inlet types are:
The choice of carrier gas (mobile phase) is important. Hydrogen has a range of flow rates that are comparable to helium in efficiency. However, helium may be more efficient and provide the best separation if flow rates are optimized. Helium is non-flammable and works with a greater number of detectors and older instruments. Therefore, helium is the most common carrier gas used. However, the price of helium has gone up considerably over recent years, causing an increasing number of chromatographers to switch to hydrogen gas. Historical use, rather than rational consideration, may contribute to the continued preferential use of helium.
Commonly used detectors are the flame ionization detector (FID) and the thermal conductivity detector (TCD). While TCDs are beneficial in that they are non-destructive, its low detection limit for most analytes inhibits widespread use. [ 1 ] FIDs are sensitive primarily to hydrocarbons, and are more sensitive to them than TCD. [ 4 ] FIDs cannot detect water or carbon dioxide which make them ideal for environmental organic analyte analysis. [ 1 ] FID is two to three times more sensitive to analyte detection than TCD. [ 1 ]
The TCD relies on the thermal conductivity of matter passing around a thin wire of tungsten-rhenium with a current traveling through it. [ 4 ] In this set up helium or nitrogen serve as the carrier gas because of their relatively high thermal conductivity which keep the filament cool and maintain uniform resistivity and electrical efficiency of the filament. [ 4 ] [ 13 ] When analyte molecules elute from the column, mixed with carrier gas, the thermal conductivity decreases while there is an increase in filament temperature and resistivity resulting in fluctuations in voltage ultimately causing a detector response. [ 4 ] [ 13 ] Detector sensitivity is proportional to filament current while it is inversely proportional to the immediate environmental temperature of that detector as well as flow rate of the carrier gas. [ 4 ]
In a flame ionization detector (FID), electrodes are placed adjacent to a flame fueled by hydrogen / air near the exit of the column, and when carbon containing compounds exit the column they are pyrolyzed by the flame. [ 4 ] [ 13 ] This detector works only for organic / hydrocarbon containing compounds due to the ability of the carbons to form cations and electrons upon pyrolysis which generates a current between the electrodes. [ 4 ] [ 13 ] The increase in current is translated and appears as a peak in a chromatogram. FIDs have low detection limits (a few picograms per second) but they are unable to generate ions from carbonyl containing carbons. [ 4 ] FID compatible carrier gasses include helium, hydrogen, nitrogen, and argon. [ 4 ] [ 13 ]
In FID, sometimes the stream is modified before entering the detector. A methanizer converts carbon monoxide and carbon dioxide into methane so that it can be detected. A different technology is the polyarc, by Activated Research Inc, that converts all compounds to methane.
Alkali flame detector (AFD) or alkali flame ionization detector (AFID) has high sensitivity to nitrogen and phosphorus, similar to NPD. However, the alkaline metal ions are supplied with the hydrogen gas, rather than a bead above the flame. For this reason AFD does not suffer the "fatigue" of the NPD, but provides a constant sensitivity over long period of time. In addition, when alkali ions are not added to the flame, AFD operates like a standard FID. A catalytic combustion detector (CCD) measures combustible hydrocarbons and hydrogen. Discharge ionization detector (DID) uses a high-voltage electric discharge to produce ions.
Flame photometric detector (FPD) uses a photomultiplier tube to detect spectral lines of the compounds as they are burned in a flame. Compounds eluting off the column are carried into a hydrogen fueled flame which excites specific elements in the molecules, and the excited elements (P,S, Halogens, Some Metals) emit light of specific characteristic wavelengths. [ 13 ] The emitted light is filtered and detected by a photomultiplier tube. [ 4 ] [ 13 ] In particular, phosphorus emission is around 510–536 nm and sulfur emission is at 394 nm. [ 4 ] [ 13 ] With an atomic emission detector (AED), a sample eluting from a column enters a chamber which is energized by microwaves that induce a plasma. [ 13 ] The plasma causes the analyte sample to decompose and certain elements generate an atomic emission spectra. [ 13 ] The atomic emission spectra is diffracted by a diffraction grating and detected by a series of photomultiplier tubes or photo diodes. [ 13 ]
Electron capture detector (ECD) uses a radioactive beta particle (electron) source to measure the degree of electron capture. ECD are used for the detection of molecules containing electronegative / withdrawing elements and functional groups like halogens, carbonyl, nitriles, nitro groups, and organometalics. [ 4 ] [ 13 ] In this type of detector either nitrogen or 5% methane in argon is used as the mobile phase carrier gas. [ 4 ] [ 13 ] The carrier gas passes between two electrodes placed at the end of the column, and adjacent to the cathode (negative electrode) resides a radioactive foil such as 63Ni. [ 4 ] [ 13 ] The radioactive foil emits a beta particle (electron) which collides with and ionizes the carrier gas to generate more ions resulting in a current. [ 4 ] [ 13 ] When analyte molecules with electronegative / withdrawing elements or functional groups electrons are captured which results in a decrease in current generating a detector response. [ 4 ] [ 13 ]
Nitrogen–phosphorus detector (NPD), a form of thermionic detector where nitrogen and phosphorus alter the work function on a specially coated bead and a resulting current is measured.
Dry electrolytic conductivity detector (DELCD) uses an air phase and high temperature (v. Coulsen) to measure chlorinated compounds.
Mass spectrometer (MS), also called GC-MS ; highly effective and sensitive, even in a small quantity of sample. This detector can be used to identify the analytes in chromatograms by their mass spectrum. [ 14 ] Some GC-MS are connected to an NMR spectrometer which acts as a backup detector. This combination is known as GC-MS-NMR . [ citation needed ] Some GC-MS-NMR are connected to an infrared spectrophotometer which acts as a backup detector. This combination is known as GC-MS-NMR-IR. It must, however, be stressed this is very rare as most analyses needed can be concluded via purely GC-MS. [ citation needed ]
Vacuum ultraviolet (VUV) represents the most recent development in gas chromatography detectors. Most chemical species absorb and have unique gas phase absorption cross sections in the approximately 120–240 nm VUV wavelength range monitored. Where absorption cross sections are known for analytes, the VUV detector is capable of absolute determination (without calibration) of the number of molecules present in the flow cell in the absence of chemical interferences. [ 15 ]
Olfactometric detector , also called GC-O, uses a human assessor to analyse the odour activity of compounds. With an odour port or a sniffing port, the quality of the odour, the intensity of the odour and the duration of the odour activity of a compound can be assessed.
Other detectors include the Hall electrolytic conductivity detector (ElCD), helium ionization detector (HID), infrared detector (IRD), photo-ionization detector (PID), pulsed discharge ionization detector (PDD), and thermionic ionization detector (TID). [ 16 ]
The method is the collection of conditions in which the GC operates for a given analysis. Method development is the process of determining what conditions are adequate and/or ideal for the analysis required.
Conditions which can be varied to accommodate a required analysis include inlet temperature, detector temperature, column temperature and temperature program, carrier gas and carrier gas flow rates, the column's stationary phase, diameter and length, inlet type and flow rates, sample size and injection technique. Depending on the detector(s) (see below) installed on the GC, there may be a number of detector conditions that can also be varied. Some GCs also include valves which can change the route of sample and carrier flow. The timing of the opening and closing of these valves can be important to method development.
Typical carrier gases include helium , nitrogen , argon , and hydrogen . [ 4 ] [ 1 ] Which gas to use is usually determined by the detector being used, for example, a DID requires helium as the carrier gas. [ 1 ] When analyzing gas samples the carrier is also selected based on the sample's matrix, for example, when analyzing a mixture in argon, an argon carrier is preferred because the argon in the sample does not show up on the chromatogram. Safety and availability can also influence carrier selection.
The purity of the carrier gas is also frequently determined by the detector, though the level of sensitivity needed can also play a significant role. Typically, purities of 99.995% or higher are used. The most common purity grades required by modern instruments for the majority of sensitivities are 5.0 grades, or 99.999% pure meaning that there is a total of 10 ppm of impurities in the carrier gas that could affect the results. The highest purity grades in common use are 6.0 grades, but the need for detection at very low levels in some forensic and environmental applications has driven the need for carrier gases at 7.0 grade purity and these are now commercially available. Trade names for typical purities include "Zero Grade", "Ultra-High Purity (UHP) Grade", "4.5 Grade" and "5.0 Grade".
The carrier gas linear velocity affects the analysis in the same way that temperature does (see above). The higher the linear velocity the faster the analysis, but the lower the separation between analytes. Selecting the linear velocity is therefore the same compromise between the level of separation and length of analysis as selecting the column temperature. The linear velocity will be implemented by means of the carrier gas flow rate, with regards to the inner diameter of the column.
With GCs made before the 1990s, carrier flow rate was controlled indirectly by controlling the carrier inlet pressure, or "column head pressure". The actual flow rate was measured at the outlet of the column or the detector with an electronic flow meter, or a bubble flow meter, and could be an involved, time consuming, and frustrating process. It was not possible to vary the pressure setting during the run, and thus the flow was essentially constant during the analysis. The relation between flow rate and inlet pressure is calculated with Poiseuille's equation for compressible fluids .
Many modern GCs, however, electronically measure the flow rate, and electronically control the carrier gas pressure to set the flow rate. Consequently, carrier pressures and flow rates can be adjusted during the run, creating pressure/flow programs similar to temperature programs.
The polarity of the solute is crucial for the choice of stationary compound, which in an optimal case would have a similar polarity as the solute. Common stationary phases in open tubular columns are cyanopropylphenyl dimethyl polysiloxane, carbowax polyethyleneglycol, biscyanopropyl cyanopropylphenyl polysiloxane and diphenyl dimethyl polysiloxane. For packed columns more options are available. [ 4 ]
The choice of inlet type and injection technique depends on if the sample is in liquid, gas, adsorbed, or solid form, and on whether a solvent matrix is present that has to be vaporized. Dissolved samples can be introduced directly onto the column via a COC injector, if the conditions are well known; if a solvent matrix has to be vaporized and partially removed, a S/SL injector is used (most common injection technique); gaseous samples (e.g., air cylinders) are usually injected using a gas switching valve system; adsorbed samples (e.g., on adsorbent tubes) are introduced using either an external (on-line or off-line) desorption apparatus such as a purge-and-trap system, or are desorbed in the injector (SPME applications).
The real chromatographic analysis starts with the introduction of the sample onto the column. The development of capillary gas chromatography resulted in many practical problems with the injection technique. The technique of on-column injection, often used with packed columns, is usually not possible with capillary columns. In the injection system in the capillary gas chromatograph the amount injected should not overload the column and
the width of the injected plug should be small compared to the spreading due to the chromatographic process. Failure to comply with this latter requirement will reduce the separation capability of the column. As a general rule, the volume injected, V inj , and the volume of the detector cell, V det , should be about 1/10 of the volume occupied by the portion of sample containing the molecules of interest (analytes) when they exit the column.
Some general requirements which a good injection technique should fulfill are that it should be possible to obtain the column's optimum separation efficiency, it should allow accurate and reproducible injections of small amounts of representative samples, it should induce no change in sample composition, it should not exhibit discrimination based on differences in boiling point, polarity, concentration or thermal/catalytic stability, and it should be applicable for trace analysis as well as for undiluted samples.
However, there are a number of problems inherent in the use of syringes for injection. Even the best syringes claim an accuracy of only 3%, and in unskilled hands, errors are much larger. The needle may cut small pieces of rubber from the septum as it injects sample through it. These can block the needle and prevent the syringe filling the next time it is used. It may not be obvious that this has happened. A fraction of the sample may get trapped in the rubber, to be released during subsequent injections. This can give rise to ghost peaks in the chromatogram. There may be selective loss of the more volatile components of the sample by evaporation from the tip of the needle. [ 17 ]
The choice of column depends on the sample and the active measured. The main chemical attribute regarded when choosing a column is the polarity of the mixture, but functional groups can play a large part in column selection. The polarity of the sample must closely match the polarity of the column stationary phase to increase resolution and separation while reducing run time. The separation and run time also depends on the film thickness (of the stationary phase), the column diameter and the column length.
The column(s) in a GC are contained in an oven, the temperature of which is precisely controlled electronically. (When discussing the "temperature of the column," an analyst is technically referring to the temperature of the column oven. The distinction, however, is not important and will not subsequently be made in this article.)
The rate at which a sample passes through the column is directly proportional to the temperature of the column. The higher the column temperature, the faster the sample moves through the column. However, the faster a sample moves through the column, the less it interacts with the stationary phase, and the less the analytes are separated.
In general, the column temperature is selected to compromise between the length of the analysis and the level of separation.
A method which holds the column at the same temperature for the entire analysis is called "isothermal". Most methods, however, increase the column temperature during the analysis, the initial temperature, rate of temperature increase (the temperature "ramp"), and final temperature are called the temperature program.
A temperature program allows analytes that elute early in the analysis to separate adequately, while shortening the time it takes for late-eluting analytes to pass through the column.
Generally, chromatographic data is presented as a graph of detector response (y-axis) against retention time (x-axis), which is called a chromatogram. This provides a spectrum of peaks for a sample representing the analytes present in a sample eluting from the column at different times. Retention time can be used to identify analytes if the method conditions are constant. Also, the pattern of peaks will be constant for a sample under constant conditions and can identify complex mixtures of analytes. However, in most modern applications, the GC is connected to a mass spectrometer or similar detector that is capable of identifying the analytes represented by the peaks.
The area under a peak is proportional to the amount of analyte present in the chromatogram. By calculating the area of the peak using the mathematical function of integration , the concentration of an analyte in the original sample can be determined. Concentration can be calculated using a calibration curve created by finding the response for a series of concentrations of analyte, or by determining the relative response factor of an analyte. The relative response factor is the expected ratio of an analyte to an internal standard (or external standard ) and is calculated by finding the response of a known amount of analyte and a constant amount of internal standard (a chemical added to the sample at a constant concentration, with a distinct retention time to the analyte).
In most modern GC-MS systems, computer software is used to draw and integrate peaks, and match MS spectra to library spectra.
In general, substances that vaporize below 300 °C (and therefore are stable up to that temperature) can be measured quantitatively. The samples are also required to be salt -free; they should not contain ions . Very minute amounts of a substance can be measured, but it is often required that the sample must be measured in comparison to a sample containing the pure, suspected substance known as a reference standard .
Various temperature programs can be used to make the readings more meaningful; for example to differentiate between substances that behave similarly during the GC process.
Professionals working with GC analyze the content of a chemical product, for example in assuring the quality of products in the chemical industry; or measuring chemicals in soil, air or water, such as soil gases . [ 18 ] GC is very accurate if used properly and can measure picomoles of a substance in a 1 ml liquid sample, or parts-per-billion concentrations in gaseous samples.
In practical courses at colleges, students sometimes get acquainted to the GC by studying the contents of lavender oil or measuring the ethylene that is secreted by Nicotiana benthamiana plants after artificially injuring their leaves. These GC analyse hydrocarbons (C2-C40+). In a typical experiment, a packed column is used to separate the light gases, which are then detected with a TCD . The hydrocarbons are separated using a capillary column and detected with a FID . A complication with light gas analyses that include H 2 is that He, which is the most common and most sensitive inert carrier (sensitivity is proportional to molecular mass) has an almost identical thermal conductivity to hydrogen (it is the difference in thermal conductivity between two separate filaments in a Wheatstone Bridge type arrangement that shows when a component has been eluted). For this reason, dual TCD instruments used with a separate channel for hydrogen that uses nitrogen as a carrier are common. Argon is often used when analysing gas phase chemistry reactions such as F-T synthesis so that a single carrier gas can be used rather than two separate ones. The sensitivity is reduced, but this is a trade off for simplicity in the gas supply.
Gas chromatography is used extensively in forensic science . Disciplines as diverse as solid drug dose (pre-consumption form) identification and quantification, arson investigation, paint chip analysis, and toxicology cases, employ GC to identify and quantify various biological specimens and crime-scene evidence.
Media related to Gas chromatography at Wikimedia Commons | https://en.wikipedia.org/wiki/Gas_chromatography |
Gas chromatography–mass spectrometry ( GC–MS ) is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. [ 1 ] Applications of GC–MS include drug detection, fire investigation, environmental analysis, explosives investigation, food and flavor analysis, and identification of unknown samples, including that of material samples obtained from planet Mars during probe missions as early as the 1970s. GC–MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification. Like liquid chromatography–mass spectrometry , it allows analysis and detection even of tiny amounts of a substance. [ 2 ]
GC–MS has been regarded as a " gold standard " for forensic substance identification because it is used to perform a 100% specific test, which positively identifies the presence of a particular substance. A nonspecific test merely indicates that any of several in a category of substances is present. Although a nonspecific test could statistically suggest the identity of the substance, this could lead to false positive identification. However, the high temperatures (300°C) used in the GC–MS injection port (and oven) can result in thermal degradation of injected molecules, [ 3 ] thus resulting in the measurement of degradation products instead of the actual molecule(s) of interest.
The first on-line coupling of gas chromatography to a mass spectrometer was reported in the late 1950s. [ 4 ] [ 5 ] An interest in coupling the methods had been suggested as early as December 1954, [ 6 ] but conventional recording techniques had too poor temporal resolution. Fortunately, time-of-flight mass spectrometry developed around the same time allowed to measure spectra thousands times a second. [ 7 ]
The development of affordable and miniaturized computers has helped in the simplification of the use of this instrument, as well as allowed great improvements in the amount of time it takes to analyze a sample. In 1964, Electronic Associates, Inc. (EAI) , a leading U.S. supplier of analog computers, began development of a computer controlled quadrupole mass spectrometer under the direction of Robert E. Finnigan . [ 8 ] By 1966 Finnigan and collaborator Mike Uthe's EAI division had sold over 500 quadrupole residual gas-analyzer instruments. [ 8 ] In 1967, Finnigan left EAI to form the Finnigan Instrument Corporation along with Roger Sant, T. Z. Chou, Michael Story, Lloyd Friedman, and William Fies. [ 9 ] In early 1968, they delivered the first prototype quadrupole GC/MS instruments to Stanford and Purdue University. [ 8 ] When Finnigan Instrument Corporation was acquired by Thermo Instrument Systems (later Thermo Fisher Scientific ) in 1990, it was considered "the world's leading manufacturer of mass spectrometers". [ 10 ]
The GC–MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer . The gas chromatograph utilizes a capillary column whose properties regarding molecule separation depend on the column's dimensions (length, diameter, film thickness) as well as the phase properties (e.g. 5% phenyl polysiloxane). The difference in the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote separation of the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off) from the column at different times (called the retention time), and this allows the mass spectrometer downstream to capture, ionize, accelerate, deflect, and detect the ionized molecules separately. The mass spectrometer does this by breaking each molecule into ionized fragments and detecting these fragments using their mass-to-charge ratio.
These two components, used together, allow a much finer degree of substance identification than either unit used separately. It is not possible to make an accurate identification of a particular molecule by gas chromatography or mass spectrometry alone. The mass spectrometry process normally requires a very pure sample while gas chromatography using a traditional detector (e.g. Flame ionization detector ) cannot differentiate between multiple molecules that happen to take the same amount of time to travel through the column ( i.e. have the same retention time), which results in two or more molecules that co-elute. Sometimes two different molecules can also have a similar pattern of ionized fragments in a mass spectrometer (mass spectrum). Combining the two processes reduces the possibility of error, as it is extremely unlikely that two different molecules will behave in the same way in both a gas chromatograph and a mass spectrometer. Therefore, when an identifying mass spectrum appears at a characteristic retention time in a GC–MS analysis, it typically increases certainty that the analyte of interest is in the sample.
For the analysis of volatile compounds, a purge and trap (P&T) concentrator system may be used to introduce samples. The target analytes are extracted by mixing the sample with water and purge with inert gas (e.g. Nitrogen gas ) into an airtight chamber, this is known as purging or sparging . The volatile compounds move into the headspace above the water and are drawn along a pressure gradient (caused by the introduction of the purge gas) out of the chamber. The volatile compounds are drawn along a heated line onto a 'trap'. The trap is a column of adsorbent material at ambient temperature that holds the compounds by returning them to the liquid phase. The trap is then heated and the sample compounds are introduced to the GC–MS column via a volatiles interface, which is a split inlet system. P&T GC–MS is particularly suited to volatile organic compounds (VOCs) and BTEX compounds (aromatic compounds associated with petroleum). [ 11 ]
A faster alternative is the "purge-closed loop" system. In this system the inert gas is bubbled through the water until the concentrations of organic compounds in the vapor phase are at equilibrium with concentrations in the aqueous phase. The gas phase is then analysed directly. [ 12 ]
The most common type of mass spectrometer (MS) associated with a gas chromatograph (GC) is the quadrupole mass spectrometer, sometimes referred to by the Hewlett-Packard (now Agilent ) trade name "Mass Selective Detector" (MSD). Another relatively common detector is the ion trap mass spectrometer. Additionally one may find a magnetic sector mass spectrometer, however these particular instruments are expensive and bulky and not typically found in high-throughput service laboratories. Other detectors may be encountered such as time of flight (TOF), tandem quadrupoles (MS-MS) (see below), or in the case of an ion trap MS n where n indicates the number mass spectrometry stages.
When a second phase of mass fragmentation is added, for example using a second quadrupole in a quadrupole instrument, it is called tandem MS (MS/MS). MS/MS can sometimes be used to quantitate low levels of target compounds in the presence of a high sample matrix background.
The first quadrupole (Q1) is connected with a collision cell (Q2) and another quadrupole (Q3). Both quadrupoles can be used in scanning or static mode, depending on the type of MS/MS analysis being performed. Types of analysis include product ion scan, precursor ion scan, selected reaction monitoring (SRM) (sometimes referred to as multiple reaction monitoring (MRM)) and neutral loss scan. For example: When Q1 is in static mode (looking at one mass only as in SIM), and Q3 is in scanning mode, one obtains a so-called product ion spectrum (also called "daughter spectrum"). From this spectrum, one can select a prominent product ion which can be the product ion for the chosen precursor ion. The pair is called a "transition" and forms the basis for SRM. SRM is highly specific and virtually eliminates matrix background.
After the molecules travel the length of the column, pass through the transfer line and enter into the mass spectrometer they are ionized by various methods with typically only one method being used at any given time. Once the sample is fragmented it will then be detected, usually by an electron multiplier , which essentially turns the ionized mass fragment into an electrical signal that is then detected.
The ionization technique chosen is independent of using full scan or SIM.
By far the most common and perhaps standard form of ionization is electron ionization (EI). The molecules enter into the MS (the source is a quadrupole or the ion trap itself in an ion trap MS) where they are bombarded with free electrons emitted from a filament, not unlike the filament one would find in a standard light bulb. The electrons bombard the molecules, causing the molecule to fragment in a characteristic and reproducible way. This "hard ionization" technique results in the creation of more fragments of low mass-to-charge ratio (m/z) and few, if any, molecules approaching the molecular mass unit. Hard ionization is considered by mass spectrometrists as the employ of molecular electron bombardment, whereas "soft ionization" is charge by molecular collision with an introduced gas. The molecular fragmentation pattern is dependent upon the electron energy applied to the system, typically 70 eV (electronvolts). The use of 70 eV facilitates comparison of generated spectra with library spectra using manufacturer-supplied software or software developed by the National Institute of Standards (NIST-USA). Spectral library searches employ matching algorithms such as Probability Based Matching [ 13 ] and dot-product [ 14 ] matching that are used with methods of analysis written by many method standardization agencies. Sources of libraries include NIST, [ 15 ] Wiley, [ 16 ] the AAFS, [ 17 ] and instrument manufacturers.
The "hard ionization" process of electron ionization can be softened by the cooling of the molecules before their ionization, resulting in mass spectra that are richer in information. [ 18 ] [ 19 ] In this method named cold electron ionization (cold-EI) the molecules exit the GC column, mixed with added helium make up gas and expand into vacuum through a specially designed supersonic nozzle, forming a supersonic molecular beam (SMB). Collisions with the make up gas at the expanding supersonic jet reduce the internal vibrational (and rotational) energy of the analyte molecules, hence reducing the degree of fragmentation caused by the electrons during the ionization process. [ 18 ] [ 19 ] Cold-EI mass spectra are characterized by an abundant molecular ion while the usual fragmentation pattern is retained, thus making cold-EI mass spectra compatible with library search identification techniques. The enhanced molecular ions increase the identification probabilities of both known and unknown compounds, amplify isomer mass spectral effects and enable the use of isotope abundance analysis for the elucidation of elemental formulas. [ 20 ]
In chemical ionization (CI) a reagent gas, typically methane or ammonia is introduced into the mass spectrometer. Depending on the technique (positive CI or negative CI) chosen, this reagent gas will interact with the electrons and analyte and cause a 'soft' ionization of the molecule of interest. A softer ionization fragments the molecule to a lower degree than the hard ionization of EI. One of the main benefits of using chemical ionization is that a mass fragment closely corresponding to the molecular weight of the analyte of interest is produced. [ 21 ]
In positive chemical ionization (PCI) the reagent gas interacts with the target molecule, most often with a proton exchange. This produces the species in relatively high amounts.
In negative chemical ionization (NCI) the reagent gas decreases the impact of the free electrons on the target analyte. This decreased energy typically leaves the fragment in great supply.
A mass spectrometer is typically utilized in one of two ways: full scan or selective ion monitoring (SIM). The typical GC–MS instrument is capable of performing both functions either individually or concomitantly, depending on the setup of the particular instrument.
The primary goal of instrument analysis is to quantify an amount of substance. This is done by comparing the relative concentrations among the atomic masses in the generated spectrum. Two kinds of analysis are possible, comparative and original. Comparative analysis essentially compares the given spectrum to a spectrum library to see if its characteristics are present for some sample in the library. This is best performed by a computer because there are a myriad of visual distortions that can take place due to variations in scale. Computers can also simultaneously correlate more data (such as the retention times identified by GC), to more accurately relate certain data. Deep learning was shown to lead to promising results in the identification of VOCs from raw GC–MS data. [ 22 ]
Another method of analysis measures the peaks in relation to one another. In this method, the tallest peak is assigned 100% of the value, and the other peaks being assigned proportionate values. All values above 3% are assigned. The total mass of the unknown compound is normally indicated by the parent peak. The value of this parent peak can be used to fit with a chemical formula containing the various elements which are believed to be in the compound. The isotope pattern in the spectrum, which is unique for elements that have many natural isotopes, can also be used to identify the various elements present. Once a chemical formula has been matched to the spectrum, the molecular structure and bonding can be identified, and must be consistent with the characteristics recorded by GC–MS. Typically, this identification is done automatically by programs which come with the instrument, given a list of the elements which could be present in the sample.
A "full spectrum" analysis considers all the "peaks" within a spectrum. Conversely, selective ion monitoring (SIM) only monitors selected ions associated with a specific substance. This is done on the assumption that at a given retention time, a set of ions is characteristic of a certain compound. This is a fast and efficient analysis, especially if the analyst has previous information about a sample or is only looking for a few specific substances. When the amount of information collected about the ions in a given gas chromatographic peak decreases, the sensitivity of the analysis increases. So, SIM analysis allows for a smaller quantity of a compound to be detected and measured, but the degree of certainty about the identity of that compound is reduced.
When collecting data in the full scan mode, a target range of mass fragments is determined and put into the instrument's method. An example of a typical broad range of mass fragments to monitor would be m/z 50 to m/z 400. The determination of what range to use is largely dictated by what one anticipates being in the sample while being cognizant of the solvent and other possible interferences. A MS should not be set to look for mass fragments too low or else one may detect air (found as m/z 28 due to nitrogen), carbon dioxide ( m/z 44) or other possible interference. Additionally if one is to use a large scan range then sensitivity of the instrument is decreased due to performing fewer scans per second since each scan will have to detect a wide range of mass fragments.
Full scan is useful in determining unknown compounds in a sample. It provides more information than SIM when it comes to confirming or resolving compounds in a sample. During instrument method development it may be common to first analyze test solutions in full scan mode to determine the retention time and the mass fragment fingerprint before moving to a SIM instrument method.
In selective ion monitoring (SIM) certain ion fragments are entered into the instrument method and only those mass fragments are detected by the mass spectrometer. The advantages of SIM are that the detection limit is lower since the instrument is only looking at a small number of fragments (e.g. three fragments) during each scan. More scans can take place each second. Since only a few mass fragments of interest are being monitored, matrix interferences are typically lower. To additionally confirm the likelihood of a potentially positive result, it is relatively important to be sure that the ion ratios of the various mass fragments are comparable to a known reference standard.
GC–MS is becoming the tool of choice for tracking organic pollutants in the environment. The cost of GC–MS equipment has decreased significantly, and the reliability has increased at the same time, which has contributed to its increased adoption in environmental studies .
GC–MS can analyze the particles from a human body in order to help link a criminal to a crime . The analysis of fire debris using GC–MS is well established, and there is even an established American Society for Testing and Materials (ASTM) standard for fire debris analysis. GCMS/MS is especially useful here as samples often contain very complex matrices, and results used in court need to be highly accurate.
GC–MS is increasingly used for detection of illegal narcotics, and may eventually supplant drug-sniffing dogs. [1] A simple and selective GC–MS method for detecting marijuana usage was recently developed by the Robert Koch Institute in Germany. It involves identifying an acid metabolite of tetrahydrocannabinol (THC), the active ingredient in marijuana, in urine samples by employing derivatization in the sample preparation. [ 23 ] GC–MS is also commonly used in forensic toxicology to find drugs and/or poisons in biological specimens of suspects, victims, or the deceased. In drug screening, GC–MS methods frequently utilize liquid-liquid extraction as a part of sample preparation, in which target compounds are extracted from blood plasma. [ 24 ]
GC–MS is the main tool used in sports anti-doping laboratories to test athletes' urine samples for prohibited performance-enhancing drugs, for example anabolic steroids . [ 25 ]
A post–September 11 development, explosive detection systems have become a part of all US airports . These systems run on a host of technologies, many of them based on GC–MS. There are only three manufacturers certified by the FAA to provide these systems, [ citation needed ] one of which is Thermo Detection (formerly Thermedics), which produces the EGIS , a GC–MS-based line of explosives detectors. The other two manufacturers are Barringer Technologies, now owned by Smith's Detection Systems, and Ion Track Instruments, part of General Electric Infrastructure Security Systems.
As part of the post-September 11 drive towards increased capability in homeland security and public health preparedness, traditional GC–MS units with transmission quadrupole mass spectrometers, as well as those with cylindrical ion trap (CIT-MS) and toroidal ion trap (T-ITMS) mass spectrometers have been modified for field portability and near real-time detection of chemical warfare agents (CWA) such as sarin, soman, and VX. [ 26 ] These complex and large GC–MS systems have been modified and configured with resistively heated low thermal mass (LTM) gas chromatographs that reduce analysis time to less than ten percent of the time required in traditional laboratory systems. [ 27 ] Additionally, the systems are smaller, and more mobile, including units that are mounted in mobile analytical laboratories (MAL), such as those used by the United States Marine Corps Chemical and Biological Incident Response Force MAL and other similar laboratories, and systems that are hand-carried by two-person teams or individuals, much ado to the smaller mass detectors. [ 28 ] Depending on the system, the analytes can be introduced via liquid injection, desorbed from sorbent tubes through a thermal desorption process, or with solid-phase micro extraction (SPME).
GC–MS is used for the analysis of unknown organic compound mixtures. One critical use of this technology is the use of GC–MS to determine the composition of bio-oils processed from raw biomass. [ 29 ] GC–MS is also utilized in the identification of continuous phase component in a smart material, magnetorheological (MR) fluid . [ 30 ]
Foods and beverages contain numerous aromatic compounds , some naturally present in the raw materials and some forming during processing. GC–MS is extensively used for the analysis of these compounds which include esters , fatty acids , alcohols , aldehydes , terpenes etc. It is also used to detect and measure contaminants from spoilage or adulteration which may be harmful and which is often controlled by governmental agencies, for example pesticides .
Several GC–MS systems have left earth. Two were brought to Mars by the Viking program . [ 31 ] Venera 11 and 12 and Pioneer Venus analysed the atmosphere of Venus with GC–MS. [ 32 ] The Huygens probe of the Cassini–Huygens mission landed one GC–MS on Saturn 's largest moon, Titan . [ 33 ] The MSL Curiosity rover's Sample analysis at Mars (SAM) instrument contains both a gas chromatograph and quadrupole mass spectrometer that can be used in tandem as a GC–MS. [ 34 ] The material in the comet 67P/Churyumov–Gerasimenko was analysed by the Rosetta mission with a chiral GC–MS in 2014. [ 35 ]
Dozens of congenital metabolic diseases also known as inborn errors of metabolism (IEM) are now detectable by newborn screening tests, especially the testing using gas chromatography–mass spectrometry. GC–MS can determine compounds in urine even in minor concentration. These compounds are normally not present but appear in individuals suffering with metabolic disorders. This is increasingly becoming a common way to diagnose IEM for earlier diagnosis and institution of treatment eventually leading to a better outcome. It is now possible to test a newborn for over 100 genetic metabolic disorders by a urine test at birth based on GC–MS. [ citation needed ]
In combination with isotopic labeling of metabolic compounds, the GC–MS is used for determining metabolic activity . Most applications are based on the use of 13 C as the labeling and the measurement of 13 C- 12 C ratios with an isotope ratio mass spectrometer (IRMS); an MS with a detector designed to measure a few select ions and return values as ratios. | https://en.wikipedia.org/wiki/Gas_chromatography–mass_spectrometry |
Gas chromatography–vacuum ultraviolet spectroscopy (GC-VUV) is a universal detection technique for gas chromatography . [ 1 ] VUV detection provides both qualitative and quantitative spectral information for most gas phase compounds.
GC-VUV spectral data is three-dimensional (time, absorbance, wavelength) and specific to chemical structure. Nearly all compounds absorb in the vacuum ultraviolet region of the electromagnetic spectrum with the exception of carrier gases hydrogen , helium , and argon . The high energy, short wavelength VUV photons probe electronic transitions in almost all chemical bonds including ground state to excited state . The result is spectral "fingerprints" that are specific to individual compound structure and can be readily identified by the VUV library.
Unique VUV spectra enable closely related compounds such as structural isomers to be clearly differentiated. VUV detectors complement mass spectrometry , which struggles with characterizing constitutional isomers and compounds with low mass quantitation ions. VUV spectra can also be used to deconvolve analyte co-elution, resulting in an accurate quantitative representation of individual analyte contribution to the original response. [ 2 ] This characteristically lends itself to significantly reducing GC runtimes through flow rate-enhanced chromatographic compression.
VUV spectroscopy follows the simple linear relationship between absorbance and concentration described by the Beer-Lambert Law , resulting in more accurate retention time-based identification. VUV absorbance spectra also exhibit feature similarity within compound classes, meaning VUV detectors can rapidly compound class characterization in complex samples through compound spectral shape and retention index information. Advances in technology reduces the typical group analysis data processing time from 15 to 30 minutes to <1 minute per sample. [ 3 ]
The first benchtop detector was introduced in 2014 with detection capabilities between 120 and 240 nm. This portion of the ultraviolet spectrum had historically been restricted to bright source synchrotron facilities due to significant background absorption challenges inherent to working within the wavelength range. Further detector platform development has extended the wavelength detection range out from 120 to 430 nm. [ 4 ]
VUV detectors are compatible with most gas chromatography (GC) manufacturers. The detectors can be connected through a heated transfer line inserted through a punch-out in the GC oven casing. A makeup flow of carrier gas is introduced at the end of the transfer line. Analytes arrive in the flow cell and are exposed to VUV light from a deuterium lamp . Specially coated reflective optics paired with a back-thinned charge-coupled device (CCD) enable the collection of high-quality VUV absorption data. Figure 1 shows a schematic of the analyte path from GC to VUV detector.
Gas phase species absorb and display unique spectra between 120 – 240 nm where high energy σ→σ*, n→σ*, π→π*, n → π* electronic transitions can be excited and probed. VUV spectra reflect the absorbance cross section of compounds and are specific to their electronic structure and functional group arrangement. The ability of VUV detectors to produce spectra for most compounds results in universal and highly selective compound identification. VUV spectroscopy data is highly characteristic while also providing quantitative information. Many commonly used GC detectors such as the electron capture detector (ECD), flame ionization detector (FID), and thermal conductivity detector (TCD) produce quantitative but not qualitative detail. Gas chromatography–mass spectrometry (GC-MS) generates qualitative and quantitative data but has difficulty characterizing labile and low mass compounds, as well as differentiating between isomers. GC-VUV complements MS by overcoming its limitations and providing a secondary method of confirmation. It also offers a single-instrument alternative to the use of multiple detectors for qualitative and quantitative analysis.
Naphthols , xylenes , and cis- and trans- fatty acids are compounds that are prohibitively difficult to distinguish according to their electron ionization mass spectral profiles. [ 5 ] Xylenes present the additional challenge of natural co-elution that makes separating their isoforms problematic. Figure 2 shows the distinct VUV spectra of m-, p-, and o-xylene. These compounds can be differentiated despite their only difference being the position of two methyl groups around a benzene ring. The spectral differences of these isomers enable their co-elution to be resolved through spectral deconvolution.
Fatty acid screening and profiling is an application that commonly requires the use of multiple detectors to achieve quantitative and qualitative results. [ 6 ] FID is a quantitative detector that is suitable for routine screening when guided by retention index information. GC-MS has traditionally been used for qualitative compound profiling, but falls short where isobaric analytes are prevalent. It especially struggles with differentiating cis and trans fatty acid isomers. Electron impact ionization can also cause double bond migration and lead to ambiguous fatty acid structural data.
Determining cis and trans fatty acid distribution in oils and fats is important in assessing their potential health impacts. VUV spectra of trans-containing fatty acid methyl ester (FAME) isomers typically found in butter and vegetable oils are shown in Figure 3. These trans-containing isomers separate chromatographically from cis-containing isomers and have the tendency to co-elute with each other and, in some cases, with select C20:1 isomers. GC-VUV is not only able to differentiate the C18:3 FAME variants, but is also capable of telling cis isomers apart from trans isomers. Degrees of unsaturation such as C20:1 vs. C18:3 can additionally be distinguished. Previous work has demonstrated how distinct VUV spectra enable straightforward deconvolution and accurate quantitation of cis and trans FAME isomers. [ 7 ] [ 8 ]
Unique VUV absorbance spectra not only enable unambiguous compound identification, and allows GC run times to be deliberately shortened. VUV detectors operate at ambient pressure and are thus not flow rate limited. GC run times can be reduced by increasing the GC column flow and oven temperature program rates.
Flow rate-enhanced chromatographic compression utilizes VUV spectral deconvolution to resolve any co-elution that may result from shortening GC runtimes. VUV absorption is additive, meaning that overlapping peaks give a spectrum that corresponds to the sum absorbance of each compound. The individual contribution of each analyte can be determined if the VUV spectra for co-eluting compounds are stored in the VUV library. [ 9 ] The ability to differentiate coeluting analyte spectra and use them to deconvolve the overlapping signals is demonstrated in Figure 4. The individual spectra of terpenes limonene and p-Cymene are shown in Panel A along with the summed absorbance of the selected retention time window (blue region in Panel B) and the fit with VUV library spectra. The R 2 >0.999 fit result confirms their identities, and enables the deconvolution of these and other terpenes analyzed by GC-VUV as featured in Panel B.
Testing for the presence of residual solvents in Active Pharmaceutical Ingredients (APIs) is critical for patient safety and commonly follows United States Pharmacopeia (USP) Method <467> guidelines, or more broadly, International Council for Harmonization (ICH) Guideline Q3C(R6). The gas chromatography (GC) runtime suggested by USP Method 467 is approximately 60 min. A generic method for residual solvent analysis by GC-MS describes conditions that include a runtime of approximately 30 minutes. [ 10 ] A GC-VUV and static headspace method was developed using a chromatographic compression strategy that resulted in a GC runtime of 8 minutes. The GC-VUV method uses a flow rate of 4 mL/min and an oven ramp of 35 °C (held for 1 min), followed by an increase to 245 °C at a rate of 30 °C/min.
Figure 5 compares the results when the general conditions of the GC-MS method were followed against the GC-VUV method run with Class 2 residual solvents. Tetralin eluted at approximately 35 minutes using the GC-MS method conditions, whereas the analyte had a retention time of less than 7 minutes when the GC-VUV method was applied. The co-elution of m- and p-xylene occurred in both GC-MS and GC-VUV method runs. VUV software matched the analyte absorbance of both isomers with VUV library spectra (Figure 2) to deconvolve the overlapping signals as displayed in Figure 6. Goodness of fit information ensures that the correct compound assignment takes place during the post-run data analysis.
The flow rate-enhanced chromatographic compression strategy has been applied to a diverse set of applications since the development of the GC-VUV method for residual solvents analysis. The fast GC-VUV approach reduced GC runtimes for terpene analysis from 30 minutes to 9 minutes (the deconvolution of monoterpene isomers is shown in Figure 4). It has also been demonstrated that GC runtimes as short as 14 minutes can be used for PIONA compound analysis of gasoline samples. Typical GC separation times range between 1 – 2 hours using alternative methods.
GC-VUV can be used for bulk compositional analysis because compounds share spectral shape characteristics within a class. Proprietary software applies fitting procedures to quickly determine the relative contribution of each compound category present in a sample. Retention index information is used to limit the amount of VUV library searching and fitting performed for each analyte, enabling the automated data processing routine to be completed quickly. Compound class or specific compound concentrations can be reported as either mass or volume percent.
GC-VUV bulk compound characterization was first applied to the analysis of paraffin , isoparaffin , olefin , naphthene , and aromatic (PIONA) hydrocarbons in gasoline streams. It is suitable for use with finished gasoline, reformate, reformer feed, FCC, light naphtha, and heavy naphtha samples. A typical chromatographic analysis is displayed in Figure 7. The inset shows how the analyte spectral response is fit with VUV library spectra for the selected time slice. A report detailing the carbon number breakdown within each PIONA compound class, as well as the relative mass or volume percent of classes, is shown. A table with mass % and carbon number data from a gasoline sample can be seen in Figure 8. Compound class characterization utilizes a method known as time interval deconvolution (TID), which has recently been applied to the analysis of terpenes. | https://en.wikipedia.org/wiki/Gas_chromatography–vacuum_ultraviolet_spectroscopy |
Gas cluster ion beams ( GCIB ) is a technology for nano-scale modification of surfaces. It can smooth a wide variety of surface material types to within an angstrom of roughness without subsurface damage. It is also used to chemically alter surfaces through infusion or deposition.
Using GCIB a surface is bombarded by a beam of high-energy, nanoscale cluster ions . The clusters are formed when a high pressure gas (approximately 10 atmospheres pressure) expands into a vacuum (1e-5 atmospheres). The gas expands adiabatically and cools then condenses into clusters. The clusters are nano-sized bits of crystalline matter with unique properties that are intermediate between the realms of atomic physics and those of solid state physics. The expansion takes place inside of a nozzle that shapes the gas flow and facilitates the formation of a narrow jet of clusters moving along the axis of symmetry of the nozzle. The jet of clusters passes through differential pumping apertures into a region of high vacuum (1e-8 atmospheres) where the clusters are ionized by collisions with energetic electrons . The ionized clusters are accelerated electrostatically to high velocities, and they are focused into a tight beam.
The GCIB beam is then used to treat a surface — typically the treated substrate is mechanically scanned in the beam to allow uniform irradiation of the surface. Argon is a commonly used gas in GCIB treatments because it is chemically inert and inexpensive. Argon forms clusters readily, the atoms in the cluster are bound together with Van der Waals forces . Typical parameters for a high-energy, Argon GCIB are acceleration voltage 30 kV, average cluster size 10,400 atoms, average cluster charge +3.2, average cluster energy 64 keV , average cluster velocity 6.5 km/s , with a total electric current of 200 μA or more. [ 1 ] [ 2 ] When an Argon cluster with these parameters strikes a surface, a shallow crater is formed with a diameter of approximately 20 nm and a depth of 10 nm. When imaged using atomic force microscope (AFM) the craters have an appearance much like craters on planetary bodies. [ 3 ] [ 4 ] [ 5 ] A typical GCIB surface treatment allows every point on the surface to be struck by many cluster ions, resulting in smoothing of surface irregularities.
Lower energy GCIB treatments can be used to further smooth the surface. Reducing the energy decreases the size and depth of the impact craters and, analogous to mechanical polishing where the grit size is reduced during polishing, subsequent treatments with lower energies are used to reach an atomic level smoothness. Low energy clusters can be used to harden and densify the surface. Advantages of GCIB surface polishing over conventional polishing include the ability to easily smooth non-planer surfaces, very thin substrates and thin-films. GCIB assisted thin-film deposition produces denser and more uniform films. Almost any gas can be used for GCIB, and there are many more uses for chemically reactive clusters such as for doping semiconductors (using B 2 H 6 gas), cleaning and etching (using NF 3 gas), oxidizing (using O 2 gas), reducing oxide (using H 2 gas), nitriding (using N 2 gas), and for depositing chemical layers. GCIB can be applied to any substrate material but the smoothing properties will depend on the homogeneity of the surface.
In industry, GCIB has been used for the manufacture of semiconductor devices , [ 6 ] optical thin films , [ 7 ] trimming SAW and FBAR filter devices, [ 8 ] fixed disk memory systems and for other uses. GCIB smoothing of high voltage electrodes has been shown to reduce field electron emission and GCIB treated RF cavities are being studied for use in future high energy particle accelerators . [ 9 ]
Small argon cluster GCIB sources are increasingly used for analytical depth-profiling by secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). Argon clusters greatly reduce the damage introduced to the specimen during depth-profiling, making it practical to do so for many organic and polymeric materials for the first time. This has greatly extended the range of materials to which XPS (for example) can be applied. [ 10 ] [ 11 ] Gas cluster sputter rates of different polymers differ a great deal, [ 12 ] and X-ray damage (of the type that accumulates during XPS analysis) can change these sputter rates markedly. [ 13 ] While generally less damaging than monotomic sputtering, gas cluster ion sputtering can nevertheless introduce damage that is very noticeable in some materials. [ 14 ]
A related technique, with a limited range of applications, using high-velocity carbon Fullerenes to treat surfaces, has been studied. [ citation needed ]
Accelerated neutral atoms beams (ANAB) is a recent variation on GCIB. [ 15 ] With ANAB, the high velocity clusters are heated and evaporated by collisions with thermal energy gas molecules and the charged cluster remnants are deflected out of the beam leaving an intense focused beam of individual fast neutral monomers/atoms. The monomers are evaporated from the clusters with low thermal energies and they retain the center of mass velocity of the cluster and hence do not move out of the beam before colliding with the surface. When used to treat a surface, an ANAB beam has nearly the same total energy and velocity of the original GCIB beam but the smoothing effect on the surface is much different as the dispersed impacts of the individual fast atoms is more gentle than that of the clusters. With ANAB there is even less subsurface damage than with GCIB. The lack of electrical charge eliminates space-charge defocusing of the beam and static charge buildup on surfaces which is very useful for applications such as semiconductor device manufacturing. [ 16 ] | https://en.wikipedia.org/wiki/Gas_cluster_ion_beam |
The characterization gas collecting tube describes an oblong gas-tight container with one valve at either end. Usually such a container has a gauged volume , has a cylindrical shape and is made of glass . Gas collecting tubes are used for science-related purposes; for taking samples of gases. | https://en.wikipedia.org/wiki/Gas_collecting_tube |
The gas combustion retort process (also referred as gas-combustion retorting process ) was an above-ground retorting technology for shale oil extraction . It was a predecessor of the Paraho and Petrosix processes, and modern directly heated oil shale retorting technologies in general. [ 1 ]
The gas combustion retort process was developed by the United States Bureau of Mines at the end of the 1940s. The first gas combustion retort, designed by Cameron Engineers , went into operation in 1949 and it was located in the United States Bureau of Mines' Oil Shale Experiment Station at Anvil Point in Rifle, Colorado . The Bureau of Mines tested this process in three retorts with capacity of 6, 10, and 25 ton of oil shale per day accordingly. [ 1 ] The consortium of Mobil , Humble Oil , Continental Oil , Pan American Oil, Phillips Petroleum Company , and Sinclair Oil evaluated and improved this technology between 1964 and 1968. [ 1 ]
The gas combustion retort process is classified as an internal combustion technology. For the oil shale pyrolysis it uses a vertical vessel retort. [ 2 ]
Crushed raw oil shale is fed into the top of the retort, and it moves downward by gravity. When moving downward, oil shale is heated by the rising recycled gases, which cause decomposition of the rock. Recycled gases enter the retort from the bottom. Gases are heated on the lower part of retort by descended spent shale . On their way up, gases move through the combustion zone, where air and dilution gases are injected causing combustion of gases and carbonaceous residue of spent shale ( char ). The heat from combustion brings the temperature in the retorting zone above of the burning zone to the necessary level for retorting. The incoming raw oil shale cool oil vapors and gases, which then leave the top of the retort as a mist. [ 1 ] [ 2 ] [ 3 ] [ 4 ]
The main advantage of this process was that it does not require cooling water, which made it suitable for using in the semi-arid regions. [ 1 ] [ 4 ] | https://en.wikipedia.org/wiki/Gas_combustion_retort_process |
The molar gas constant (also known as the gas constant , universal gas constant , or ideal gas constant ) is denoted by the symbol R or R . It is the molar equivalent to the Boltzmann constant , expressed in units of energy per temperature increment per amount of substance , rather than energy per temperature increment per particle . The constant is also a combination of the constants from Boyle's law , Charles's law , Avogadro's law , and Gay-Lussac's law . It is a physical constant that is featured in many fundamental equations in the physical sciences, such as the ideal gas law , the Arrhenius equation , and the Nernst equation .
The gas constant is the constant of proportionality that relates the energy scale in physics to the temperature scale and the scale used for amount of substance . Thus, the value of the gas constant ultimately derives from historical decisions and accidents in the setting of units of energy, temperature and amount of substance. The Boltzmann constant and the Avogadro constant were similarly determined, which separately relate energy to temperature and particle count to amount of substance.
The gas constant R is defined as the Avogadro constant N A multiplied by the Boltzmann constant k (or k B ):
Since the 2019 revision of the SI , both N A and k are defined with exact numerical values when expressed in SI units. [ 2 ] As a consequence, the SI value of the molar gas constant is exact.
Some have suggested that it might be appropriate to name the symbol R the Regnault constant in honour of the French chemist Henri Victor Regnault , whose accurate experimental data were used to calculate the early value of the constant. However, the origin of the letter R to represent the constant is elusive. The universal gas constant was apparently introduced independently by August Friedrich Horstmann (1873) [ 3 ] [ 4 ] and Dmitri Mendeleev who reported it first on 12 September 1874. [ 5 ] Using his extensive measurements of the properties of gases, [ 6 ] [ 7 ] Mendeleev also calculated it with high precision, within 0.3% of its modern value. [ 8 ]
The gas constant occurs in the ideal gas law: P V = n R T = m R specific T , {\displaystyle PV=nRT=mR_{\text{specific}}T,} where P is the absolute pressure , V is the volume of gas, n is the amount of substance , m is the mass , and T is the thermodynamic temperature . R specific is the mass-specific gas constant. The gas constant is expressed in the same unit as molar heat .
From the ideal gas law PV = nRT we get
where P is pressure, V is volume, n is number of moles of a given substance, and T is temperature .
As pressure is defined as force per area of measurement, the gas equation can also be written as
Area and volume are (length) 2 and (length) 3 respectively. Therefore:
Since force × length = work,
The physical significance of R is work per mole per kelvin. It may be expressed in any set of units representing work or energy (such as joules ), units representing temperature on an absolute scale (such as kelvin or rankine ), and any system of units designating a mole or a similar pure number that allows an equation of macroscopic mass and fundamental particle numbers in a system, such as an ideal gas (see Avogadro constant ).
Instead of a mole the constant can be expressed by considering the normal cubic metre .
Otherwise, we can also say that
Therefore, we can write R as
And so, in terms of SI base units ,
The Boltzmann constant k B (alternatively k ) may be used in place of the molar gas constant by working in pure particle count, N , rather than amount of substance, n , since
where N A is the Avogadro constant .
For example, the ideal gas law in terms of the Boltzmann constant is
where N is the number of particles (molecules in this case), or to generalize to an inhomogeneous system the local form holds:
where n = N / V is the number density .
Finally, by defining the kinetic energy associated to the temperature,
the equation becomes simply
which is the form usually encountered in statistical mechanics and other branches of theoretical physics.
As of 2006, the most precise measurement of R had been obtained by measuring the speed of sound c a ( P , T ) in argon at the temperature T of the triple point of water at different pressures P , and extrapolating to the zero-pressure limit c a (0, T ). The value of R is then obtained from the relation
where
However, following the 2019 revision of the SI , R now has an exact value defined in terms of other exactly defined physical constants.
The specific gas constant of a gas or a mixture of gases ( R specific ) is given by the molar gas constant divided by the molar mass ( M ) of the gas or mixture:
Just as the molar gas constant can be related to the Boltzmann constant, so can the specific gas constant by dividing the Boltzmann constant by the molecular mass of the gas:
Another important relationship comes from thermodynamics. Mayer's relation relates the specific gas constant to the specific heat capacities for a calorically perfect gas and a thermally perfect gas:
where c p is the specific heat capacity for a constant pressure, and c V is the specific heat capacity for a constant volume. [ 10 ]
It is common, especially in engineering applications, to represent the specific gas constant by the symbol R . In such cases, the universal gas constant is usually given a different symbol such as R to distinguish it. In any case, the context and/or unit of the gas constant should make it clear as to whether the universal or specific gas constant is being referred to. [ 11 ]
In case of air, using the perfect gas law and the standard sea-level conditions (SSL) (air density ρ 0 = 1.225 kg/m 3 , temperature T 0 = 288.15 K and pressure p 0 = 101 325 Pa ), we have that R air = P 0 /( ρ 0 T 0 ) = 287.052 874 247 J·kg −1 ·K −1 . Then the molar mass of air is computed by M 0 = R / R air = 28.964 917 g/mol . [ 12 ]
The U.S. Standard Atmosphere , 1976 (USSA1976) defines the gas constant R ∗ as [ 13 ] [ 14 ]
Note the use of the kilomole, with the resulting factor of 1000 in the constant. The USSA1976 acknowledges that this value is not consistent with the cited values for the Avogadro constant and the Boltzmann constant. [ 14 ] This disparity is not a significant departure from accuracy, and USSA1976 uses this value of R ∗ for all the calculations of the standard atmosphere. When using the ISO value of R , the calculated pressure increases by only 0.62 pascal at 11 kilometres (the equivalent of a difference of only 17.4 centimetres or 6.8 inches) and 0.292 Pa at 20 km (the equivalent of a difference of only 33.8 cm or 13.2 in).
Also note that this was well before the 2019 SI redefinition, through which the constant was given an exact value. | https://en.wikipedia.org/wiki/Gas_constant |
A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure . Gas storage cylinders may also be called bottles . Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid , or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened or dished bottom end or foot ring, with the cylinder valve screwed into the internal neck thread at the top for connecting to the filling or receiving apparatus. [ 1 ]
Gas cylinders may be grouped by several characteristics, such as construction method, material, pressure group, class of contents, transportability, and re-usability. [ 2 ]
The size of a pressurised gas container that may be classed as a gas cylinder is typically 0.5 litres to 150 litres. Smaller containers may be termed gas cartridges, and larger may be termed gas tubes, tanks, or other specific type of pressure vessel. A gas cylinder is used to store gas or liquefied gas at pressures above normal atmospheric pressure. [ 2 ] In South Africa, a gas storage cylinder implies a refillable transportable container with a water capacity volume of up to 150 litres. Refillable transportable cylindrical containers from 150 to 3,000 litres water capacity are referred to as tubes. [ 1 ]
In the United States, " bottled gas " typically refers to liquefied petroleum gas . "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tanks . Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used. The term propane tank is also used for cylinders for propane. [ citation needed ]
The United Kingdom and other parts of Europe more commonly refer to "bottled gas" when discussing any usage, whether industrial, medical, or liquefied petroleum. In contrast, what is called liquefied petroleum gas in the United States is known generically in the United Kingdom as "LPG" and it may be ordered by using one of several trade names , or specifically as butane or propane , depending on the required heat output. [ citation needed ]
The term cylinder in this context is sometimes confused with tank , the latter being an open-top or vented container that stores liquids under gravity, though the term scuba tank is commonly used to refer to a compressed gas cylinder used for breathing gas supply to an underwater breathing apparatus .
Since fibre-composite materials have been used to reinforce pressure vessels, various types of cylinder distinguished by the construction method and materials used have been defined: [ 7 ] [ 8 ]
Assemblies comprising a group of cylinders mounted together for combined use or transport:
All-metal cylinders are the most rugged and usually the most economical option, but are relatively heavy. Steel is generally the most resistant to rough handling and most economical, and is often lighter than aluminium for the same working pressure, capacity, and form factor due to its higher specific strength. The inspection interval of industrial steel cylinders has increased from 5 or 6 years to 10 years. Diving cylinders that are used in water must be inspected more often; intervals tend to range between 1 and 5 years. Steel cylinders are typically withdrawn from service after 70 years, or may continue to be used indefinitely providing they pass periodic inspection and testing. [ citation needed ] When they were found to have inherent structural problems, certain steel and aluminium alloys were withdrawn from service, or discontinued from new production, while existing cylinders may require different inspection or testing, but remain in service provided they pass these tests. [ citation needed ]
For very high pressures, composites have a greater mass advantage. Due to the very high tensile strength of carbon fiber reinforced polymer , these vessels can be very light, but are more expensive to manufacture. [ 12 ] Filament wound composite cylinders are used in fire fighting breathing apparatus, high altitude climbing, and oxygen first aid equipment because of their low weight, but are rarely used for diving, due to their high positive buoyancy . They are occasionally used when portability for accessing the dive site is critical, such as in cave diving where the water surface is far from the cave entrance. [ 13 ] [ 14 ] Composite cylinders certified to ISO-11119-2 or ISO-11119-3 may only be used for underwater applications if they are manufactured in accordance with the requirements for underwater use and are marked "UW". [ 15 ]
Cylinders reinforced with or made from a fibre reinforced material usually must be inspected more frequently than metal cylinders, e.g. , every 5 instead of 10 years, and must be inspected more thoroughly than metal cylinders as they are more susceptible to impact damage. They may also have a limited service life. [ citation needed ] Fibre composite cylinders were originally specified for a limited life span of 15, 20 or 30 years, but this has been extended when they proved to be suitable for longer service. [ citation needed ]
The Type 1 pressure vessel is a seamless cylinder normally made of cold-extruded aluminum or forged steel . [ 16 ] The pressure vessel comprises a cylindrical section of even wall thickness, with a thicker base at one end, and domed shoulder with a central neck to attach a cylinder valve or manifold at the other end.
Occasionally other materials may be used. Inconel has been used for non-magnetic and highly corrosion resistant oxygen compatible spherical high-pressure gas containers for the US Navy's Mk-15 and Mk-16 mixed gas rebreathers, and a few other military rebreathers.
Most aluminum cylinders are flat bottomed, allowing them to stand upright on a level surface, but some were manufactured with domed bottoms.
Aluminum cylinders are usually manufactured by cold extrusion of aluminum billets in a process which first presses the walls and base, then trims the top edge of the cylinder walls, followed by press forming the shoulder and neck. The final structural process is machining the neck outer surface, boring and cutting the neck threads and O-ring groove. The cylinder is then heat-treated, tested and stamped with the required permanent markings. [ 17 ]
Steel cylinders are often used because they are harder and more resistant to external surface impact and abrasion damage, and can tolerate higher temperatures without affecting material properties. They also may have a lower mass than aluminium cylinders with the same gas capacity , due to considerably higher specific strength . Steel cylinders are more susceptible than aluminium to external corrosion, particularly in seawater, and may be galvanized or coated with corrosion barrier paints to resist corrosion damage. It is not difficult to monitor external corrosion, and repair the paint when damaged, and steel cylinders which are well maintained have a long service life, often longer than aluminium cylinders, as they are not susceptible to fatigue damage when filled within their safe working pressure limits.
Steel cylinders are manufactured with domed (convex) and dished (concave) bottoms. The dished profile allows them to stand upright on a horizontal surface, and is the standard shape for industrial cylinders. The cylinders used for emergency gas supply on diving bells are often this shape, and commonly have a water capacity of about 50 litres ("J"). Domed bottoms give a larger volume for the same cylinder mass, and are the standard for scuba cylinders up to 18 litres water capacity, though some concave bottomed cylinders have been marketed for scuba. Domed end industrial cylinders may be fitted with a press-fitted foot ring to allow upright standing. [ 18 ] [ 19 ]
Steel alloys used for gas cylinder manufacture are authorised by the manufacturing standard. For example, the US standard DOT 3AA requires the use of open-hearth, basic oxygen, or electric steel of uniform quality. Approved alloys include 4130X, NE-8630, 9115, 9125, Carbon-boron and Intermediate manganese, with specified constituents, including manganese and carbon, and molybdenum, chromium, boron, nickel or zirconium. [ 20 ]
Steel cylinders may be manufactured from steel plate discs stamped from annealed plate or coil, which are lubricated and cold drawn to a cylindrical cup form, by a hydraulic press, this is annealed and drawn again in two or three stages, until the final diameter and wall thickness is reached. They generally have a domed base if intended for the scuba market, so they cannot stand up by themselves.For industrial use a dished base allows the cylinder to stand on the end on a flat surface. After forming the base and side walls, the top of the cylinder is trimmed to length, heated and hot spun to form the shoulder and close the neck. This process thickens the material of the shoulder. The cylinder is heat-treated by quenching and tempering to provide the best strength and toughness. The cylinders are machined to provide the neck thread and o-ring seat (if applicable), then chemically cleaned or shot-blasted inside and out to remove mill-scale. After inspection and hydrostatic testing they are stamped with the required permanent markings, followed by external coating with a corrosion barrier paint or hot dip galvanising and final inspection. [ 21 ] [ 4 ]
A related method is to start with seamless steel tube of a suitable diameter and wall thickness, manufactured by a process such as the Mannesmann process , and to close both ends by the hot spinning process. This method is particularly suited to high pressure gas storage tubes , which usually have a threaded neck opening at both ends, so that both ends are processed alike. When a neck opening is only required at one end, the base is spun first and dressed inside for a uniform smooth surface, then the process of closing the shoulder and forming the neck is the same as for the pressed plate method. [ 4 ]
An alternative production method is backward extrusion of a heated steel billet, similar to the cold extrusion process for aluminium cylinders, followed by hot drawing and bottom forming to reduce wall thickness, and trimming of the top edge in preparation for shoulder and neck formation by hot spinning. The other processes are much the same for all production methods. [ 22 ] [ 4 ]
The neck of the cylinder is the part of the end which is shaped as a narrow concentric cylinder, and internally threaded to fit a cylinder valve. There are several standards for neck threads, which include parallel threads where the seal is by an O-ring gasket, and taper threads which seal along the contact surface by deformation of the contact surfaces, and on thread tape or sealing compound . [ 3 ]
Type 2 is hoop wrapped with fibre reinforced resin over the cylindrical part of the cylinder, where circumferential load is highest. The fibres share the circumferential load with the metal core, and achieve a significant weight saving due to efficient stress distribution and high specific strength and stiffness of the composite. The core is a seamless metal cylinder, manufactured in any of the ways suitable for a type 1 cylinder, but with thinner walls, as they only carry about half the load, mainly the axial load. Hoop winding is at an angle to the length axis of close to 90°, so the fibres carry negligible axial load. [ 4 ]
Type 3 is wrapped over the entire cylinder except for the neck, and the metal liner is mainly to make the cylinder gas tight, so very little load is carried by the liner. Winding angles are optimised to carry all the loads (axial and circumferential) from the pressurised gas in the cylinder. Only the neck metal is exposed on the outside. This construction can save in the order of 30% of the mass compared with type 2, as the fibre composite has a higher specific strength than the metal of the type 2 liner that it replaces. [ 4 ]
Type 4 is wrapped in the same way as type 3, but the liner is non-metallic. A metal neck boss is fitted to the shoulder of the plastic liner before winding, and this carries the neck threads for the cylinder valve. The outside of the neck of the insert is not covered by the fibre wrapping, and may have axial ridges to engage with a wrench or clamp for torsional support when fitting or removing the cylinder valve. There is a mass reduction compared with type 3 due to the lower density of the plastic liner. [ 4 ]
A welded gas cylinder comprises two or more shell components joined by welding. The most commonly used material is steel, but stainless steel, aluminium and other alloys can be used when they are better suited to the application. Steel is strong, resistant to physical damage, easy to weld, relatively low cost, and usually adequate for corrosion resistance, and provides an economical product.
The components of the shell are usually domed ends, and often a rolled cylindrical centre section. The ends are usually domed by cold pressing from a circular blank, and may be drawn in two or more stages to get the final shape, which is generally semi-elliptical in section. The end blank is typically punched from sheet, drawn to the required section, edges trimmed to size and necked for overlap where appropriate, and hole(s) for the neck and other fittings punched. The neck boss is inserted from the concave side and welded in place before shell assembly. [ 23 ]
Smaller cylinders are typically assembled from a top and bottom dome, with an equatorial weld seam. Larger cylinders with a longer cylindrical body comprise dished ends circumferentially welded to a rolled central cylindrical section with a single longitudinal welded seam. Welding is typically automated gas metal arc welding . [ 23 ]
Typical accessories which are welded to the outside of the cylinder include a foot ring, a valve guard with lifting handles, and a neck boss threaded for the valve. Occasionally other through-shell and external fittings are also welded on. [ 23 ]
After welding, the assembly may be heat treated for stress-relief and to improve mechanical characteristics, cleaned by shotblasting , and coated with a protective and decorative coating. Testing and inspection for quality control will take place at various stages of production. [ 23 ]
The transportation of high-pressure cylinders is regulated by many governments throughout the world. Various levels of testing are generally required by the governing authority for the country in which it is to be transported while filled. In the United States, this authority is the United States Department of Transportation (DOT). Similarly in the UK, the European transport regulations (ADR) are implemented by the Department for Transport (DfT). For Canada, this authority is Transport Canada (TC). Cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriters Laboratories (UL). Each manufacturer of high-pressure cylinders is required to have an independent quality agent that will inspect the product for quality and safety.
Within the UK the " competent authority " — the Department for Transport (DfT) — implements the regulations and appointment of authorised cylinder testers is conducted by United Kingdom Accreditation Service (UKAS), who make recommendations to the Vehicle Certification Agency (VCA) for approval of individual bodies.
There are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test , burst test, ultimate tensile strength , Charpy impact test and pressure cycling.
During the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the serial number, date of manufacture, the manufacture's registered code and sometimes the test pressure. Other information may also be stamped, depending on the regulation requirements.
High-pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years. [ 24 ] In the United States, hydrostatic or ultrasonic testing is required either every five years or every ten years, depending on cylinder and its service.
Cylinder neck thread can be to any one of several standards. Both taper thread sealed with thread tape and parallel thread sealed with an O-ring have been found satisfactory for high pressure service, but each has advantages and disadvantages for specific use cases, and if there are no regulatory requirements, the type may be chosen to suit the application. [ 3 ]
A tapered thread provides simple assembly, but requires high torque for establishing a reliable seal, which causes high radial forces in the neck, and has a limited number of times it can be used before it is excessively deformed. This can be extended a bit by always returning the same fitting to the same cylinder, and avoiding over-tightening. [ 3 ]
In Australia, Europe and North America, tapered neck threads are generally preferred for inert, flammable, corrosive and toxic gases, but when aluminium cylinders are used for oxygen service to United States Department of Transportation (DOT) or Transport Canada (TC) specifications in North America, the cylinders must have parallel thread. DOT and TC allow UN pressure vessels to have tapered or parallel threaded openings. In the US, 49 CFR Part 171.11 applies, and in Canada, CSA B340-18 and CSA B341-18. In Europe and other parts of the world, tapered thread is preferred for cylinder inlets for oxidising gases. [ 3 ]
Scuba cylinders typically have a much shorter interval between internal inspections, so the use of tapered thread is less satisfactory due to the limited number of times a tapered thread valve can be re-used before it wears out, [ 3 ] so parallel thread is generally used for this application. [ 1 ]
Parallel thread can be tightened sufficiently to form a good seal with the O-ring without lubrication, which is an advantage when the lubricant may react with the O-ring or the contents. Repeated secure installations are possible with different combinations of valve and cylinder provided they have compatible thread and correct O-ring seals. Parallel thread is more likely to give the technician warning of residual internal pressure by leaking or extruding the O-ring before catastrophic failure when the O-ring seal is broken during removal of the valve. The O-ring size must be correct for the combination of cylinder and valve, and the material must be compatible with the contents and any lubricant used. [ 3 ]
Gas cylinders usually have an angle stop valve at one end, and the cylinder is usually oriented so the valve is on top. During storage, transportation, and handling when the gas is not in use, a cap may be screwed over the protruding valve to protect it from damage or breaking off in case the cylinder were to fall over. Instead of a cap, cylinders sometimes have a protective collar or neck ring around the valve assembly which has an opening for access to fit a regulator or other fitting to the valve outlet, and access to operate the valve. Installation of valves for high pressure aluminum alloy cylinders is described in the guidelines: CGA V-11, Guideline for the Installation of Valves into High Pressure Aluminum Alloy Cylinders and ISO 13341, Transportable gas cylinders—Fitting of valves to gas cylinders. [ 3 ]
The valves on industrial, medical and diving cylinders usually have threads or connection geometries of different handedness, sizes and types that depend on the category of gas, making it more difficult to mistakenly misuse a gas. For example, a hydrogen cylinder valve outlet does not fit an oxygen regulator and supply line, which could result in catastrophe. Some fittings use a right-hand thread, while others use a left-hand thread ; left-hand thread fittings are usually identifiable by notches or grooves cut into them, and are usually used for flammable gases.
In the United States, valve connections are sometimes referred to as CGA connections , since the Compressed Gas Association (CGA) publishes guidelines on what connections to use for what gasses. For example, an argon cylinder may have a "CGA 580" connection on the valve. High purity gases sometimes use CGA-DISS (" Diameter Index Safety System ") connections.
Medical gases may use the Pin Index Safety System to prevent incorrect connection of gases to services.
In the European Union, DIN connections are more common than in the United States.
In the UK, the British Standards Institution sets the standards. Included among the standards is the use left-hand threaded valves for flammable gas cylinders (most commonly brass, BS4, valves for non-corrosive cylinder contents or stainless steel, BS15, valves for corrosive contents). Non flammable gas cylinders are fitted with right-hand threaded valves (most commonly brass, BS3, valves for non-corrosive components or stainless steel, BS14, valves for corrosive contents). [ 25 ]
When the gas in the cylinder is to be used at low pressure, the cap is taken off and a pressure-regulating assembly is attached to the stop valve. This attachment typically has a pressure regulator with upstream (inlet) and downstream (outlet) pressure gauges and a further downstream needle valve and outlet connection. For gases that remain gaseous under ambient storage conditions, the upstream pressure gauge can be used to estimate how much gas is left in the cylinder according to pressure. For gases that are liquid under storage, e.g., propane, the outlet pressure is dependent on the vapor pressure of the gas, and does not fall until the cylinder is nearly exhausted, although it will vary according to the temperature of the cylinder contents. The regulator is adjusted to control the downstream pressure, which will limit the maximum flow of gas out of the cylinder at the pressure shown by the downstream gauge. For some purposes, such as shielding gas for arc welding, the regulator will also have a flowmeter on the downstream side.
The regulator outlet connection is attached to whatever needs the gas supply.
Because the contents are under pressure and are sometimes hazardous materials , handling bottled gases is regulated. Regulations may include chaining bottles to prevent falling and damaging the valve, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards. If a compressed gas cylinder falls over, causing the valve block to be sheared off, the rapid release of high-pressure gas may cause the cylinder to be violently accelerated, potentially causing property damage, injury, or death. To prevent this, cylinders are normally secured to a fixed object or transport cart with a strap or chain. They can also be stored in a safety cabinet .
In a fire, the pressure in a gas cylinder rises in direct proportion to its temperature . If the internal pressure exceeds the mechanical limitations of the cylinder and there are no means to safely vent the pressurized gas to the atmosphere, the vessel will fail mechanically. If the vessel contents are flammable, this event may result in a "fireball". [ 26 ] Oxidisers such as oxygen and fluorine will produce a similar effect by accelerating combustion in the area affected. If the cylinder's contents are liquid, but become a gas at ambient conditions, this is commonly referred to as a boiling liquid expanding vapour explosion (BLEVE). [ 27 ]
Medical gas cylinders in the UK and some other countries have a fusible plug of Wood's metal in the valve block between the valve seat and the cylinder. [ citation needed ] This plug melts at a comparatively low temperature (70 °C) and allows the contents of the cylinder to escape to the surroundings before the cylinder is significantly weakened by the heat, lessening the risk of explosion.
More common pressure relief devices are a simple burst disc installed in the base of the valve between the cylinder and the valve seat. A burst disc is a small metal gasket engineered to rupture at a pre-determined pressure. Some burst discs are backed with a low-melting-point metal, so that the valve must be exposed to excessive heat before the burst disc can rupture. [ citation needed ]
The Compressed Gas Association publishes a number of booklets and pamphlets on safe handling and use of bottled gases.
There is a wide range of standards relating to the manufacture, use and testing of pressurised gas cylinders and related components. Some examples are listed here.
Gas cylinders are often color-coded , but the codes are not standard across different jurisdictions, and sometimes are not regulated. Cylinder color can not safely be used for positive product identification; cylinders have labels to identify the gas they contain.
The Indian Standard for Gas Cylinder Color Code applies to the identification of the contents of gas cylinders intended for medical use. Each cylinder shall be painted externally in the colours corresponding to its gaseous contents. [ 35 ]
The below are example cylinder sizes and do not constitute an industry standard. [ citation needed ] [ clarification needed ]
(US DOT specs define material, making, and maximum pressure in psi. They are comparable to Transport Canada specs, which shows pressure in bars . A 3E-1800 in DOT nomenclature would be a TC 3EM 124 in Canada. [ 36 ] )
For larger volume, high pressure gas storage units, known as tubes , are available. They generally have a larger diameter and length than high pressure cylinders, and usually have a tapped neck at both ends. They may be mounted alone or in groups on trailers, permanent bases, or intermodal transport frames . Due to their length, they are mounted horizontally on mobile structures. In general usage they are often manifolded together and managed as a unit. [ 37 ] [ 38 ]
Groups of similar size cylinders may be mounted together and connected to a common manifold system to provide larger storage capacity than a single standard cylinder. This is commonly called a cylinder bank or a gas storage bank. The manifold may be arranged to allow simultaneous flow from all the cylinders, or, for a cascade filling system , where gas is tapped off cylinders according to the lowest positive pressure difference between storage and destination cylinder, being a more efficient use of pressurised gas. [ 39 ]
A gas cylinder quad, also known as a gas cylinder bundle, is a group of high pressure cylinders mounted on a transport and storage frame. There are commonly 16 cylinders, each of about 50 litres capacity mounted upright in four rows of four, on a square base with a square plan frame with lifting points on top and may have fork-lift slots in the base. The cylinders are usually interconnected by a manifold for use as a unit, but many variations in layout and structure are possible. [ 9 ] | https://en.wikipedia.org/wiki/Gas_cylinder |
A gas emissions crater or GEC is a crater that is left by an explosion that is believed to be caused by an overheated buildup of gas stuck below a layer of permafrost . [ 1 ] The gas is methane (also known as "natural gas") and is generally believed by experts to have sept up from large underground reserves toward the Earth's surface "through some kind of geological fault ," [ 1 ] getting trapped when they reach the bottom of the permafrost. [ 1 ] [ 2 ] [ 3 ] First known to have occurred in 2013, they are occurring solely in Siberia , where there are large stores of natural gas below a melting surface layer of permafrost. [ 1 ] They are believed to be a byproduct of global climate change , since the warming of Siberia's climate weakens the permafrost enough to allow a sub-surface methane buildup to cause an outburst. [ 1 ] [ 4 ] The release of this previously trapped methane into the atmosphere is also likely to increase the speed of global climate change. [ 1 ]
Gas emission craters were first spotted in 2013; [ 5 ] later satellite analysis has indicated that it was formed sometime between October 9 and November 1, 2013. Most famously, the discovery of the Yamal crater [ ru ] in 2014 quickly drew the attention of world media. [ 6 ] As of 2020, there were 17 known gas emissions craters, all of which are in the circumpolar regions of Western Siberia , on either the Yamal Peninsula or the neighboring Gydan Peninsula , which both sit atop large underground methane reserves. [ 4 ] They are variously located on land as well as at the bottom of rivers and lakes. Soon after their discovery, the term "gas emissions crater" was proposed and subsequently accepted by the scientific community.
Initially, with the sudden global fame of the Yamal crater [ ru ] , various hypotheses of its origin were put forward, including military tests, meteorite impact, UFOs, or the collapse of an underground gas facility. [ 7 ] [ 8 ] Later, in September 2018, a group of researchers from Moscow State University published an article in the journal Scientific Reports that claimed that the Yamal crater was the first cryovolcano discovered on Earth. [ 9 ]
Subsequently, however, in the course of scientific research, the scientific community has come to the general conclusion that the crater was formed as a result of the so-called gas release – an underground explosion of methane hydrates which ejects into the air all the rock and soil above it (along with releasing the methane itself). [ 10 ] [ 1 ] [ 2 ] [ 3 ] More specifically, their formation most likely occurs under the influence of fluid-dynamic processes in permafrost , which lead to the appearance of zones of accumulation of free natural gas near the surface. In this case, when the reservoir pressure of the accumulated gas fluids exceeds the pressure of the overlying strata, an avalanche-like outburst of gas-saturated rocks may occur. While thawing can promote methane release it has also been suggested that surface ice-melt water can migrate downward propelled by osmotic pressure associated to the concentration difference with a cryopeg, a lens of high-salinity water below, working as a mechanism for the accumulation of overpressure driving explosions. [ 11 ] [ 12 ]
This chemical reaction article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gas_emission_crater |
A gas engine is an internal combustion engine that runs on a fuel gas (a gaseous fuel), such as coal gas , producer gas , biogas , landfill gas , natural gas or hydrogen . In the United Kingdom and British English -speaking countries, the term is unambiguous. In the United States , due to the widespread use of "gas" as an abbreviation for gasoline (petrol), such an engine is sometimes called by a clarifying term, such as gaseous-fueled engine or natural gas engine .
Generally in modern usage, the term gas engine refers to a heavy-duty industrial engine capable of running continuously at full load for periods approaching a high fraction of 8,760 hours per year, unlike a gasoline automobile engine, which is lightweight, high-revving and typically runs for no more than 4,000 hours in its entire life. Typical power ranges from 10 kW (13 hp) to 4 MW (5,364 hp). [ 1 ]
There were many experiments with gas engines in the 19th century, but the first practical gas-fuelled internal combustion engine was built by the Belgian engineer Étienne Lenoir in 1860. [ 2 ] However, the Lenoir engine suffered from a low power output and high fuel consumption.
Lenoir's work was further researched and improved by a German engineer Nicolaus August Otto , who was later to invent the first four-stroke engine to efficiently burn fuel directly in a piston chamber. In August 1864 Otto met Eugen Langen who, being technically trained, glimpsed the potential of Otto's development, and one month after the meeting, founded the first engine factory in the world, NA Otto & Cie, in Cologne. In 1867 Otto patented his improved design and it was awarded the Grand Prize at the 1867 Paris World Exhibition. This atmospheric engine worked by drawing a mixture of gas and air into a vertical cylinder. When the piston has risen about eight inches, the gas and air mixture is ignited by a small pilot flame burning outside, which forces the piston (which is connected to a toothed rack) upwards, creating a partial vacuum beneath it. No work is done on the upward stroke. The work is done when the piston and toothed rack descend under the effects of atmospheric pressure and their own weight, turning the main shaft and flywheels as they fall. Its advantage over the existing steam engine was its ability to be started and stopped on demand, making it ideal for intermittent work such as barge loading or unloading. [ 3 ]
The atmospheric gas engine was in turn replaced by Otto's four-stroke engine . The changeover to four-stroke engines was remarkably rapid, with the last atmospheric engines being made in 1877. Liquid-fuelled engines soon followed using diesel (around 1898) or gasoline (around 1900).
The best-known builder of gas engines in the United Kingdom was Crossley of Manchester, who in 1869 acquired the United Kingdom and world (except German) rights to the patents of Otto and Langen for the new gas-fuelled atmospheric engine. In 1876 they acquired the rights to the more efficient Otto four-stroke cycle engine.
There were several other firms based in the Manchester area as well. Tangye Ltd. , of Smethwick, near Birmingham, sold its first gas engine, a 1 nominal horsepower two-cycle type, in 1881, and in 1890 the firm commenced manufacture of the four-cycle gas engine. [ 4 ]
The Anson Engine Museum in Poynton , near Stockport , England , has a collection of engines that includes several working gas engines, including the largest running Crossley atmospheric engine ever made.
Manufacturers of gas engines include Hyundai Heavy Industries , Rolls-Royce with the Bergen-Engines AS , Kawasaki Heavy Industries , Liebherr , MTU Friedrichshafen , INNIO Jenbacher , Caterpillar Inc. , Perkins Engines , MWM , Cummins , Wärtsilä , INNIO Waukesha , Guascor Energy , Deutz , MTU, MAN, Scania AB , Fairbanks-Morse , Doosan, Eaton (successor to another former large market share holder, Cooper Industries ), and Yanmar . Output ranges from about 10 kW (13 hp) micro combined heat and power (CHP) to 18 MW (24,000 hp). [ 5 ] Generally speaking, the modern high-speed gas engine is very competitive with gas turbines up to about 50 MW (67,000 hp) depending on circumstances, and the best ones are much more fuel efficient than the gas turbines. Rolls-Royce with the Bergen Engines, Caterpillar and many other manufacturers base their products on a diesel engine block and crankshaft. INNIO Jenbacher and Waukesha are the only two companies whose engines are designed and dedicated to gas alone.
Typical applications are base load or high-hour generation schemes, including combined heat and power (for typical performance figures see [ 6 ] ), landfill gas, mines gas, well -head gas and biogas , where the waste heat from the engine may be used to warm the digesters. For typical biogas engine installation parameters see. [ 7 ] For parameters of a large gas engine CHP system, as fitted in a factory, see. [ 8 ] Gas engines are rarely used for standby applications, which remain largely the province of diesel engines. One exception to this is the small (<150 kW) emergency generator often installed by farms, museums, small businesses, and residences. Connected to either natural gas from the public utility or propane from on-site storage tanks, these generators can be arranged for automatic starting upon power failure.
Liquefied natural gas (LNG) engines are expanding into the marine market, as the lean-burn gas engine can meet the new emission requirements without any extra fuel treatment or exhaust cleaning systems. Use of engines running on compressed natural gas (CNG) is also growing in the bus sector. Users in the United Kingdom include Reading Buses . Use of gas buses is supported by the Gas Bus Alliance [ 9 ] and manufacturers include Scania AB . [ 10 ]
Since natural gas , chiefly methane , has long been an economical and readily available fuel, many industrial engines are either designed or modified to use gas, as distinguished from gasoline . Their operation produces less complex-hydrocarbon pollution, and the engines have fewer internal problems. One example is the liquefied petroleum gas , chiefly propane . engine used in vast numbers of forklift trucks. Common United States usage of "gas" to mean "gasoline" requires the explicit identification of a natural gas engine. There is also such a thing as "natural gasoline", [ 11 ] but this term, which refers to a subset of natural gas liquids , is very rarely observed outside the refining industry.
A gas engine differs from a petrol engine in the way the fuel and air are mixed. A petrol engine uses a carburetor or fuel injection . but a gas engine often uses a simple venturi system to introduce gas into the air flow. Early gas engines used a three-valve system, with separate inlet valves for air and gas.
The weak point of a gas engine compared to a diesel engine is the exhaust valves, since the gas engine exhaust gases are much hotter for a given output, and this limits the power output. Thus, a diesel engine from a given manufacturer will usually have a higher maximum output than the same engine block size in the gas engine version. The diesel engine will generally have three different ratings — standby, prime, and continuous, a.k.a. 1-hour rating, 12-hour rating and continuous rating in the United Kingdom, whereas the gas engine will generally only have a continuous rating, which will be less than the diesel continuous rating.
Various ignition systems have been used, including hot-tube ignitors and spark ignition . Some modern gas engines are essentially dual-fuel engines . The main source of energy is the gas-air mixture but it is ignited by the injection of a small volume of diesel fuel .
Gas engines that run on natural gas typically have a thermal efficiency between 35-45% ( LHV basis)., [ 12 ] As of year 2018, the best engines can achieve a thermal efficiency up to 50% (LHV basis). [ 13 ] These gas engines are usually medium-speed engines Bergen Engines Fuel energy arises at the output shaft, the remainder appears as waste heat. [ 8 ] Large engines are more efficient than small engines. Gas engines running on biogas typically have a slightly lower efficiency (~1-2%) and syngas reduces the efficiency further still. GE Jenbacher's recent J624 engine is the world's first high efficiency methane-fueled 24-cylinder gas engine. [ 14 ]
When considering engine efficiency one should consider whether this is based on the lower heating value (LHV) or higher heating value (HHV) of the gas. Engine manufacturers will typically quote efficiencies based on the lower heating value of the gas, i.e. the efficiency after energy has been taken to evaporate the intrinsic moisture within the gas itself. Gas distribution networks will typically charge based upon the higher heating value of the gas. i.e. , total energy content. A quoted engine efficiency based on LHV might be say 44% whereas the same engine might have an efficiency of 39.6% based on HHV on natural gas.
It is also important to ensure that efficiency comparisons are on a like-for-like basis. For example, some manufactures have mechanically driven pumps whereas other use electrically driven pumps to drive engine cooling water, and the electrical usage can sometimes be ignored giving a falsely high apparent efficiency compared to the direct drive engines.
Engine reject heat can be used for building heating or heating a process. In an engine, roughly half the waste heat arises (from the engine jacket, oil cooler and after-cooler circuits) as hot water, which can be at up to 110 °C. The remainder arises as high-temperature heat which can generate pressurised hot water or steam by the use of an exhaust gas heat exchanger .
Two most common engine types are an air-cooled engine or water cooled engine. Water cooled nowadays use antifreeze in the internal combustion engine
Some engines (air or water) have an added oil cooler.
Cooling is required to remove excessive heat, as overheating can cause engine failure, usually from wear, cracking or warping.
The formula shows the gas flow requirement of a gas engine in norm conditions at full load.
Q = P η ⋅ 1 L H V g a s {\displaystyle Q={\frac {P}{\eta }}\cdot {\frac {1}{LHV_{gas}}}}
where: | https://en.wikipedia.org/wiki/Gas_engine |
A gas evolution reaction is a chemical reaction in which one of the end products is a gas such as oxygen or carbon dioxide . [ 1 ] [ 2 ] Gas evolution reactions may be carried out in a fume chamber when the gases produced are poisonous when inhaled or explosive. [ 3 ] | https://en.wikipedia.org/wiki/Gas_evolution_reaction |
Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane , or a biological membrane that forms the boundary between an organism and its extracellular environment.
Gases are constantly consumed and produced by cellular and metabolic reactions in most living things, so an efficient system for gas exchange between, ultimately, the interior of the cell(s) and the external environment is required. Small, particularly unicellular organisms, such as bacteria and protozoa , have a high surface-area to volume ratio . In these creatures the gas exchange membrane is typically the cell membrane . Some small multicellular organisms, such as flatworms , are also able to perform sufficient gas exchange across the skin or cuticle that surrounds their bodies. However, in most larger organisms, which have small surface-area to volume ratios, specialised structures with convoluted surfaces such as gills , pulmonary alveoli and spongy mesophylls provide the large area needed for effective gas exchange. These convoluted surfaces may sometimes be internalised into the body of the organism. This is the case with the alveoli, which form the inner surface of the mammalian lung , the spongy mesophyll, which is found inside the leaves of some kinds of plant , or the gills of those molluscs that have them, which are found in the mantle cavity.
In aerobic organisms , gas exchange is particularly important for respiration , which involves the uptake of oxygen ( O 2 ) and release of carbon dioxide ( CO 2 ). Conversely, in oxygenic photosynthetic organisms such as most land plants , uptake of carbon dioxide and release of both oxygen and water vapour are the main gas-exchange processes occurring during the day. Other gas-exchange processes are important in less familiar organisms: e.g. carbon dioxide, methane and hydrogen are exchanged across the cell membrane of methanogenic archaea . In nitrogen fixation by diazotrophic bacteria, and denitrification by heterotrophic bacteria (such as Paracoccus denitrificans and various pseudomonads ), [ 1 ] nitrogen gas is exchanged with the environment, being taken up by the former and released into it by the latter, while giant tube worms rely on bacteria to oxidize hydrogen sulfide extracted from their deep sea environment, [ 2 ] using dissolved oxygen in the water as an electron acceptor.
Diffusion only takes place with a concentration gradient . Gases will flow from a high concentration to a low concentration.
A high oxygen concentration in the alveoli and low oxygen concentration in the capillaries causes oxygen to move into the capillaries.
A high carbon dioxide concentration in the capillaries and low carbon dioxide concentration in the alveoli causes carbon dioxide to move into the alveoli.
The exchange of gases occurs as a result of diffusion down a concentration gradient. Gas molecules move from a region in which they are at high concentration to one in which they are at low concentration. Diffusion is a passive process , meaning that no energy is required to power the transport, and it follows Fick's law : [ citation needed ]
In relation to a typical biological system, where two compartments ('inside' and 'outside'), are separated by a membrane barrier, and where a gas is allowed to spontaneously diffuse down its concentration gradient: [ citation needed ]
Gases must first dissolve in a liquid in order to diffuse across a membrane , so all biological gas exchange systems require a moist environment. [ 3 ] In general, the higher the concentration gradient across the gas-exchanging surface, the faster the rate of diffusion across it. Conversely, the thinner the gas-exchanging surface (for the same concentration difference), the faster the gases will diffuse across it. [ 4 ]
In the equation above, J is the flux expressed per unit area, so increasing the area will make no difference to its value. However, an increase in the available surface area, will increase the amount of gas that can diffuse in a given time. [ 4 ] This is because the amount of gas diffusing per unit time (d q /d t ) is the product of J and the area of the gas-exchanging surface, A :
Single-celled organisms such as bacteria and amoebae do not have specialised gas exchange surfaces, because they can take advantage of the high surface area they have relative to their volume. The amount of gas an organism produces (or requires) in a given time will be in rough proportion to the volume of its cytoplasm . The volume of a unicellular organism is very small; thus, it produces (and requires) a relatively small amount of gas in a given time. In comparison to this small volume, the surface area of its cell membrane is very large, and adequate for its gas-exchange needs without further modification. However, as an organism increases in size, its surface area and volume do not scale in the same way. Consider an imaginary organism that is a cube of side-length, L . Its volume increases with the cube ( L 3 ) of its length, but its external surface area increases only with the square ( L 2 ) of its length. This means the external surface rapidly becomes inadequate for the rapidly increasing gas-exchange needs of a larger volume of cytoplasm. Additionally, the thickness of the surface that gases must cross (d x in Fick's law) can also be larger in larger organisms: in the case of a single-celled organism, a typical cell membrane is only 10 nm thick; [ 5 ] but in larger organisms such as roundworms (Nematoda) the equivalent exchange surface - the cuticle - is substantially thicker at 0.5 μm. [ 6 ]
In multicellular organisms therefore, specialised respiratory organs such as gills or lungs are often used to provide the additional surface area for the required rate of gas exchange with the external environment. However the distances between the gas exchanger and the deeper tissues are often too great for diffusion to meet gaseous requirements of these tissues. The gas exchangers are therefore frequently coupled to gas-distributing circulatory systems , which transport the gases evenly to all the body tissues regardless of their distance from the gas exchanger. [ 7 ]
Some multicellular organisms such as flatworms (Platyhelminthes) are relatively large but very thin, allowing their outer body surface to act as a gas exchange surface without the need for a specialised gas exchange organ. Flatworms therefore lack gills or lungs, and also lack a circulatory system. Other multicellular organisms such as sponges (Porifera) have an inherently high surface area, because they are very porous and/or branched. Sponges do not require a circulatory system or specialised gas exchange organs, because their feeding strategy involves one-way pumping of water through their porous bodies using flagellated collar cells . Each cell of the sponge's body is therefore exposed to a constant flow of fresh oxygenated water. They can therefore rely on diffusion across their cell membranes to carry out the gas exchange needed for respiration. [ 8 ]
In organisms that have circulatory systems associated with their specialized gas-exchange surfaces, a great variety of systems are used for the interaction between the two.
In a countercurrent flow system, air (or, more usually, the water containing dissolved air) is drawn in the opposite direction to the flow of blood in the gas exchanger. A countercurrent system such as this maintains a steep concentration gradient along the length of the gas-exchange surface (see lower diagram in Fig. 2). This is the situation seen in the gills of fish and many other aquatic creatures . [ 9 ] The gas-containing environmental water is drawn unidirectionally across the gas-exchange surface, with the blood-flow in the gill capillaries beneath flowing in the opposite direction. [ 9 ] [ 10 ] [ 11 ] Although this theoretically allows almost complete transfer of a respiratory gas from one side of the exchanger to the other, in fish less than 80% of the oxygen in the water flowing over the gills is generally transferred to the blood. [ 9 ]
Alternative arrangements are cross current systems found in birds. [ 12 ] [ 13 ] and dead-end air-filled sac systems found in the lungs of mammals. [ 14 ] [ 15 ] In a cocurrent flow system, the blood and gas (or the fluid containing the gas) move in the same direction through the gas exchanger. This means the magnitude of the gradient is variable along the length of the gas-exchange surface, and the exchange will eventually stop when an equilibrium has been reached (see upper diagram in Fig. 2). [ 9 ] Cocurrent flow gas exchange systems are not known to be used in nature.
The gas exchanger in mammals is internalized to form lungs, as it is in most of the larger land animals. [ citation needed ] Gas exchange occurs in microscopic dead-end air-filled sacs called alveoli , where a very thin membrane (called the blood-air barrier ) separates the blood in the alveolar capillaries (in the walls of the alveoli) from the alveolar air in the sacs.
The membrane across which gas exchange takes place in the alveoli (i.e. the blood-air barrier) is extremely thin (in humans, on average, 2.2 μm thick). [ 14 ] It consists of the alveolar epithelial cells , their basement membranes and the endothelial cells of the pulmonary capillaries (Fig. 4). [ 14 ] [ 16 ] The large surface area of the membrane comes from the folding of the membrane into about 300 million alveoli, with diameters of approximately 75–300 μm each. This provides an extremely large surface area (approximately 145 m 2 ) across which gas exchange can occur. [ 14 ]
Air is brought to the alveoli in small doses (called the tidal volume ), by breathing in ( inhalation ) and out ( exhalation ) through the respiratory airways , a set of relatively narrow and moderately long tubes which start at the nose or mouth and end in the alveoli of the lungs in the chest. Air moves in and out through the same set of tubes, in which the flow is in one direction during inhalation, and in the opposite direction during exhalation.
During each inhalation, at rest, approximately 500 ml of fresh air flows in through the nose. It is warmed and moistened as it flows through the nose and pharynx . By the time it reaches the trachea the inhaled air's temperature is 37 °C and it is saturated with water vapor. On arrival in the alveoli it is diluted and thoroughly mixed with the approximately 2.5–3.0 liters of air that remained in the alveoli after the last exhalation. This relatively large volume of air that is semi-permanently present in the alveoli throughout the breathing cycle is known as the functional residual capacity (FRC). [ 15 ]
At the beginning of inhalation the airways are filled with unchanged alveolar air, left over from the last exhalation. This is the dead space volume, which is usually about 150 ml. [ 17 ] It is the first air to re-enter the alveoli during inhalation. Only after the dead space air has returned to the alveoli does the remainder of the tidal volume (500 ml - 150 ml = 350 ml) enter the alveoli. [ 15 ] The entry of such a small volume of fresh air with each inhalation, ensures that the composition of the FRC hardly changes during the breathing cycle (Fig. 5). [ 15 ] The alveolar partial pressure of oxygen remains very close to 13–14 kPa (100 mmHg), and the partial pressure of carbon dioxide varies minimally around 5.3 kPa (40 mmHg) throughout the breathing cycle (of inhalation and exhalation). [ 15 ] The corresponding partial pressures of oxygen and carbon dioxide in the ambient (dry) air at sea level are 21 kPa (160 mmHg) and 0.04 kPa (0.3 mmHg) respectively. [ 15 ]
This alveolar air, which constitutes the FRC, completely surrounds the blood in the alveolar capillaries (Fig. 6). Gas exchange in mammals occurs between this alveolar air (which differs significantly from fresh air) and the blood in the alveolar capillaries. The gases on either side of the gas exchange membrane equilibrate by simple diffusion. This ensures that the partial pressures of oxygen and carbon dioxide in the blood leaving the alveolar capillaries, and ultimately circulates throughout the body, are the same as those in the FRC. [ 15 ]
The marked difference between the composition of the alveolar air and that of the ambient air can be maintained because the functional residual capacity is contained in dead-end sacs connected to the outside air by long, narrow, tubes (the airways: nose , pharynx , larynx , trachea , bronchi and their branches and sub-branches down to the bronchioles ). This anatomy, and the fact that the lungs are not emptied and re-inflated with each breath, provides mammals with a "portable atmosphere", whose composition differs significantly from the present-day ambient air . [ 18 ]
The composition of the air in the FRC is carefully monitored, by measuring the partial pressures of oxygen and carbon dioxide in the arterial blood. If either gas pressure deviates from normal, reflexes are elicited that change the rate and depth of breathing in such a way that normality is restored within seconds or minutes. [ 15 ]
All the blood returning from the body tissues to the right side of the heart flows through the alveolar capillaries before being pumped around the body again. On its passage through the lungs the blood comes into close contact with the alveolar air, separated from it by a very thin diffusion membrane which is only, on average, about 2 μm thick. [ 14 ] The gas pressures in the blood will therefore rapidly equilibrate with those in the alveoli , ensuring that the arterial blood that circulates to all the tissues throughout the body has an oxygen tension of 13−14 kPa (100 mmHg), and a carbon dioxide tension of 5.3 kPa (40 mmHg). These arterial partial pressures of oxygen and carbon dioxide are homeostatically controlled . A rise in the arterial P C O 2 {\displaystyle P_{{\mathrm {CO} }_{2}}} , and, to a lesser extent, a fall in the arterial P O 2 {\displaystyle P_{{\mathrm {O} }_{2}}} , will reflexly cause deeper and faster breathing until the blood gas tensions return to normal. The converse happens when the carbon dioxide tension falls, or, again to a lesser extent, the oxygen tension rises: the rate and depth of breathing are reduced until blood gas normality is restored.
Since the blood arriving in the alveolar capillaries has a P O 2 {\displaystyle P_{{\mathrm {O} }_{2}}} of, on average, 6 kPa (45 mmHg), while the pressure in the alveolar air is 13 kPa (100 mmHg), there will be a net diffusion of oxygen into the capillary blood, changing the composition of the 3 liters of alveolar air slightly. Similarly, since the blood arriving in the alveolar capillaries has a P C O 2 {\displaystyle P_{{\mathrm {CO} }_{2}}} of also about 6 kPa (45 mmHg), whereas that of the alveolar air is 5.3 kPa (40 mmHg), there is a net movement of carbon dioxide out of the capillaries into the alveoli. The changes brought about by these net flows of individual gases into and out of the functional residual capacity necessitate the replacement of about 15% of the alveolar air with ambient air every 5 seconds or so. This is very tightly controlled by the continuous monitoring of the arterial blood gas tensions (which accurately reflect partial pressures of the respiratory gases in the alveolar air) by the aortic bodies , the carotid bodies , and the blood gas and pH sensor on the anterior surface of the medulla oblongata in the brain. There are also oxygen and carbon dioxide sensors in the lungs, but they primarily determine the diameters of the bronchioles and pulmonary capillaries , and are therefore responsible for directing the flow of air and blood to different parts of the lungs.
It is only as a result of accurately maintaining the composition of the 3 liters alveolar air that with each breath some carbon dioxide is discharged into the atmosphere and some oxygen is taken up from the outside air. If more carbon dioxide than usual has been lost by a short period of hyperventilation , respiration will be slowed down or halted until the alveolar P C O 2 {\displaystyle P_{{\mathrm {CO} }_{2}}} has returned to 5.3 kPa (40 mmHg). It is therefore strictly speaking untrue that the primary function of the respiratory system is to rid the body of carbon dioxide "waste". In fact the total concentration of carbon dioxide in arterial blood is about 26 mM (or 58 ml per 100 ml), [ 19 ] compared to the concentration of oxygen in saturated arterial blood of about 9 mM (or 20 ml per 100 ml blood). [ 15 ] This large concentration of carbon dioxide plays a pivotal role in the determination and maintenance of the pH of the extracellular fluids . The carbon dioxide that is breathed out with each breath could probably be more correctly be seen as a byproduct of the body's extracellular fluid carbon dioxide and pH homeostats
If these homeostats are compromised, then a respiratory acidosis , or a respiratory alkalosis will occur. In the long run these can be compensated by renal adjustments to the H + and HCO 3 − concentrations in the plasma; but since this takes time, the hyperventilation syndrome can, for instance, occur when agitation or anxiety cause a person to breathe fast and deeply [ 20 ] thus blowing off too much CO 2 from the blood into the outside air, precipitating a set of distressing symptoms which result from an excessively high pH of the extracellular fluids. [ 21 ]
Oxygen has a very low solubility in water, and is therefore carried in the blood loosely combined with hemoglobin . The oxygen is held on the hemoglobin by four ferrous iron -containing heme groups per hemoglobin molecule. When all the heme groups carry one O 2 molecule each the blood is said to be "saturated" with oxygen, and no further increase in the partial pressure of oxygen will meaningfully increase the oxygen concentration of the blood. Most of the carbon dioxide in the blood is carried as HCO 3 − ions in the plasma. However the conversion of dissolved CO 2 into HCO 3 − (through the addition of water) is too slow for the rate at which the blood circulates through the tissues on the one hand, and alveolar capillaries on the other. The reaction is therefore catalyzed by carbonic anhydrase , an enzyme inside the red blood cells . [ 22 ] The reaction can go in either direction depending on the prevailing partial pressure of carbon dioxide. A small amount of carbon dioxide is carried on the protein portion of the hemoglobin molecules as carbamino groups. The total concentration of carbon dioxide (in the form of bicarbonate ions, dissolved CO 2 , and carbamino groups) in arterial blood (i.e. after it has equilibrated with the alveolar air) is about 26 mM (or 58 ml/100 ml), [ 19 ] compared to the concentration of oxygen in saturated arterial blood of about 9 mM (or 20 ml/100 ml blood). [ 15 ]
The dissolved oxygen content in fresh water is approximately 8–10 milliliters per liter compared to that of air which is 210 milliliters per liter. [ 23 ] Water is 800 times more dense than air [ 24 ] and 100 times more viscous. [ 23 ] Therefore, oxygen has a diffusion rate in air 10,000 times greater than in water. [ 23 ] The use of sac-like lungs to remove oxygen from water would therefore not be efficient enough to sustain life. [ 23 ] Rather than using lungs, gaseous exchange takes place across the surface of highly vascularized gills . Gills are specialised organs containing filaments , which further divide into lamellae . The lamellae contain capillaries that provide a large surface area and short diffusion distances, as their walls are extremely thin. [ 25 ] Gill rakers are found within the exchange system in order to filter out food, and keep the gills clean.
Gills use a countercurrent flow system that increases the efficiency of oxygen-uptake (and waste gas loss). [ 9 ] [ 10 ] [ 11 ] Oxygenated water is drawn in through the mouth and passes over the gills in one direction while blood flows through the lamellae in the opposite direction. This countercurrent maintains steep concentration gradients along the entire length of each capillary (see the diagram in the "Interaction with circulatory systems" section above). Oxygen is able to continually diffuse down its gradient into the blood, and the carbon dioxide down its gradient into the water. [ 10 ] The deoxygenated water will eventually pass out through the operculum (gill cover). Although countercurrent exchange systems theoretically allow an almost complete transfer of a respiratory gas from one side of the exchanger to the other, in fish less than 80% of the oxygen in the water flowing over the gills is generally transferred to the blood. [ 9 ]
Amphibians have three main organs involved in gas exchange: the lungs, the skin, and the gills, which can be used singly or in a variety of different combinations. The relative importance of these structures differs according to the age, the environment and species of the amphibian. The skin of amphibians and their larvae are highly vascularised, leading to relatively efficient gas exchange when the skin is moist. The larvae of amphibians, such as the pre-metamorphosis tadpole stage of frogs , also have external gills . The gills are absorbed into the body during metamorphosis , after which the lungs will then take over. The lungs are usually simpler than in the other land vertebrates , with few internal septa and larger alveoli; however, toads, which spend more time on land, have a larger alveolar surface with more developed lungs. To increase the rate of gas exchange by diffusion, amphibians maintain the concentration gradient across the respiratory surface using a process called buccal pumping . [ 26 ] The lower floor of the mouth is moved in a "pumping" manner, which can be observed by the naked eye.
All reptiles breathe using lungs. In squamates (the lizards and snakes ) ventilation is driven by the axial musculature , but this musculature is also used during movement, so some squamates rely on buccal pumping to maintain gas exchange efficiency. [ 27 ]
Due to the rigidity of turtle and tortoise shells, significant expansion and contraction of the chest is difficult. Turtles and tortoises depend on muscle layers attached to their shells, which wrap around their lungs to fill and empty them. [ 28 ] Some aquatic turtles can also pump water into a highly vascularised mouth or cloaca to achieve gas-exchange. [ 29 ] [ 30 ]
Crocodiles have a structure similar to the mammalian diaphragm - the diaphragmaticus - but this muscle helps create a unidirectional flow of air through the lungs rather than a tidal flow: this is more similar to the air-flow seen in birds than that seen in mammals. [ 31 ] During inhalation, the diaphragmaticus pulls the liver back, inflating the lungs into the space this creates. [ 32 ] [ 33 ] Air flows into the lungs from the bronchus during inhalation, but during exhalation, air flows out of the lungs into the bronchus by a different route: this one-way movement of gas is achieved by aerodynamic valves in the airways. [ 34 ] [ 35 ]
Birds have lungs but no diaphragm . They rely mostly on air sacs for ventilation . These air sacs do not play a direct role in gas exchange, but help to move air unidirectionally across the gas exchange surfaces in the lungs. During inhalation, fresh air is taken from the trachea down into the posterior air sacs and into the parabronchi which lead from the posterior air sacs into the lung. The air that enters the lungs joins the air which is already in the lungs, and is drawn forward across the gas exchanger into anterior air sacs. During exhalation, the posterior air sacs force air into the same parabronchi of the lungs, flowing in the same direction as during inhalation, allowing continuous gas exchange irrespective of the breathing cycle. Air exiting the lungs during exhalation joins the air being expelled from the anterior air sacs (both consisting of "spent air" that has passed through the gas exchanger) entering the trachea to be exhaled (Fig. 10). [ 13 ] Selective bronchoconstriction at the various bronchial branch points ensures that the air does not ebb and flow through the bronchi during inhalation and exhalation, as it does in mammals, but follows the paths described above.
The unidirectional airflow through the parabronchi exchanges respiratory gases with a crosscurrent blood flow (Fig. 9). [ 12 ] [ 13 ] The partial pressure of O 2 ( P O 2 {\displaystyle P_{{\mathrm {O} }_{2}}} ) in the parabronchioles declines along their length as O 2 diffuses into the blood. The capillaries leaving the exchanger near the entrance of airflow take up more O 2 than capillaries leaving near the exit end of the parabronchi. When the contents of all capillaries mix, the final P O 2 {\displaystyle P_{{\mathrm {O} }_{2}}} of the mixed pulmonary venous blood is higher than that of the exhaled air, but lower than that of the inhaled air. [ 12 ] [ 13 ]
Gas exchange in plants is dominated by the roles of carbon dioxide, oxygen and water vapor . CO 2 is the only carbon source for autotrophic growth by photosynthesis , and when a plant is actively photosynthesising in the light, it will be taking up carbon dioxide, and losing water vapor and oxygen. At night, plants respire , and gas exchange partly reverses: water vapor is still lost (but to a smaller extent), but oxygen is now taken up and carbon dioxide released. [ 36 ]
Plant gas exchange occurs mostly through the leaves. Gas exchange between a leaf and the atmosphere occurs simultaneously through two pathways: 1) epidermal cells and cuticular waxes (usually referred as ' cuticle ') which are always present at each leaf surface, and 2) stomata , which typically control the majority of the exchange. [ 37 ] Gases enter into the photosynthetic tissue of the leaf through dissolution onto the moist surface of the palisade and spongy mesophyll cells. The spongy mesophyll cells are loosely packed, allowing for an increased surface area, and consequently an increased rate of gas-exchange. Uptake of carbon dioxide necessarily results in some loss of water vapor, [ 38 ] because both molecules enter and leave by the same stomata, so plants experience a gas exchange dilemma: gaining enough CO 2 without losing too much water. Therefore, water loss from other parts of the leaf is minimised by the waxy cuticle on the leaf's epidermis . The size of a stoma is regulated by the opening and closing of its two guard cells : the turgidity of these cells determines the state of the stomatal opening, and this itself is regulated by water stress. Plants showing crassulacean acid metabolism are drought-tolerant xerophytes and perform almost all their gas-exchange at night, because it is only during the night that these plants open their stomata. By opening the stomata only at night, the water vapor loss associated with carbon dioxide uptake is minimised. However, this comes at the cost of slow growth: the plant has to store the carbon dioxide in the form of malic acid for use during the day, and it cannot store unlimited amounts. [ 39 ]
Gas exchange measurements are important tools in plant science: this typically involves sealing the plant (or part of a plant) in a chamber and measuring changes in the concentration of carbon dioxide and water vapour with an infrared gas analyzer . If the environmental conditions ( humidity , CO 2 concentration, light and temperature ) are fully controlled, the measurements of CO 2 uptake and water release reveal important information about the CO 2 assimilation and transpiration rates. The intercellular CO 2 concentration reveals important information about the photosynthetic condition of the plants. [ 40 ] [ 41 ] Simpler methods can be used in specific circumstances: hydrogencarbonate indicator can be used to monitor the consumption of CO 2 in a solution containing a single plant leaf at different levels of light intensity, [ 42 ] and oxygen generation by the pondweed Elodea can be measured by simply collecting the gas in a submerged test-tube containing a small piece of the plant.
The mechanism of gas exchange in invertebrates depends their size, feeding strategy, and habitat (aquatic or terrestrial).
The sponges (Porifera) are sessile creatures, meaning they are unable to move on their own and normally remain attached to their substrate . They obtain nutrients through the flow of water across their cells, and they exchange gases by simple diffusion across their cell membranes. Pores called ostia draw water into the sponge and the water is subsequently circulated through the sponge by cells called choanocytes which have hair-like structures that move the water through the sponge. [ 43 ]
The cnidarians include corals , sea anemones , jellyfish and hydras . These animals are always found in aquatic environments, ranging from fresh water to salt water. They do not have any dedicated respiratory organs ; instead, every cell in their body can absorb oxygen from the surrounding water, and release waste gases to it. One key disadvantage of this feature is that cnidarians can die in environments where water is stagnant , as they deplete the water of its oxygen supply. [ 44 ] Corals often form symbiosis with other organisms, particularly photosynthetic dinoflagellates . In this symbiosis , the coral provides shelter and the other organism provides nutrients to the coral, including oxygen. [ citation needed ]
The roundworms (Nematoda), flatworms (Platyhelminthes), and many other small invertebrate animals living in aquatic or otherwise wet habitats do not have a dedicated gas-exchange surface or circulatory system. They instead rely on diffusion of CO 2 and O 2 directly across their cuticle. [ 45 ] [ 46 ] The cuticle is the semi-permeable outermost layer of their bodies. [ citation needed ]
Other aquatic invertebrates such as most molluscs (Mollusca) and larger crustaceans (Crustacea) such as lobsters , have gills analogous to those of fish, which operate in a similar way.
Unlike the invertebrates groups mentioned so far, insects are usually terrestrial, and exchange gases across a moist surface in direct contact with the atmosphere, rather than in contact with surrounding water. The insect's exoskeleton is impermeable to gases, including water vapor, so they have a more specialised gas exchange system, requiring gases to be directly transported to the tissues via a complex network of tubes. This respiratory system is separated from their circulatory system. Gases enter and leave the body through openings called spiracles , located laterally along the thorax and abdomen . Similar to plants, insects are able to control the opening and closing of these spiracles, but instead of relying on turgor pressure , they rely on muscle contractions . [ 47 ] These contractions result in an insect's abdomen being pumped in and out. The spiracles are connected to tubes called tracheae , which branch repeatedly and ramify into the insect's body. These branches terminate in specialised tracheole cells which provides a thin, moist surface for efficient gas exchange, directly with cells. [ 48 ]
The other main group of terrestrial arthropod , the arachnids ( spiders , scorpion , mites , and their relatives) typically perform gas exchange with a book lung . [ 49 ] | https://en.wikipedia.org/wiki/Gas_exchange |
A gas explosion is the ignition of a mixture of air and flammable gas, typically from a gas leak . [ 1 ] In household accidents, the principal explosive gases are those used for heating or cooking purposes such as natural gas , methane , propane , butane . In industrial explosions, many other gases, like hydrogen , as well as evaporated (gaseous) gasoline or ethanol play an important role. Industrial gas explosions can be prevented with the use of intrinsic safety barriers to prevent ignition, or use of alternative energy.
Whether a mixture of air and gas is combustible depends on the air-to-fuel ratio . For each fuel, ignition occurs only within a certain range of concentration, known as the upper and lower flammability limits . For example, for methane and gasoline vapor, this range is 5-15% and 1.4-7.6% gas to air, respectively. An explosion can only occur when fuel concentration is within these limits [ citation needed ] | https://en.wikipedia.org/wiki/Gas_explosion |
A gas flare , alternatively known as a flare stack , flare boom , ground flare , or flare pit , is a gas combustion device used in places such as petroleum refineries , chemical plants and natural gas processing plants, oil or gas extraction sites having oil wells , gas wells , offshore oil and gas rigs and landfills .
In industrial plants, flare stacks are primarily used for burning off flammable gas released by safety valves during unplanned overpressuring of plant equipment. [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] During plant or partial plant startups and shutdowns, they are also often used for the planned combustion of gases over relatively short periods.
At oil and gas extraction sites, gas flares are similarly used for a variety of startup, maintenance, testing, safety, and emergency purposes. [ 6 ] In a practice known as production flaring , they may also be used to dispose of large amounts of unwanted associated petroleum gas , possibly throughout the life of an oil well. [ 7 ]
When industrial plant equipment items are overpressured, the pressure relief valve is an essential safety device that automatically releases gases and sometimes liquids. Those pressure relief valves are required by industrial design codes and standards as well as by law.
The released gases and liquids are routed through large piping systems called flare headers to a vertical elevated flare. The released gases are burned as they exit the flare stacks. The size and brightness of the resulting flame depends upon the flammable material's flow rate in joules per hour (or btu per hour). [ 4 ]
Most industrial plant flares have a vapor–liquid separator (also known as a knockout drum) upstream of the flare to remove any large amounts of liquid that may accompany the relieved gases.
Steam is very often injected into the flame to reduce the formation of black smoke. When too much steam is added, a condition known as "oversteaming" can occur resulting in reduced combustion efficiency and higher emissions. [ 8 ] To keep the flare system functional, a small amount of gas is continuously burned, like a pilot light , so that the system is always ready for its primary purpose as an overpressure safety system.
The adjacent flow diagram depicts the typical components of an overall industrial flare stack system: [ 1 ] [ 2 ] [ 3 ]
The schematic shows a pipe flare tip. The flare tip can have several configurations:
The height of a flare stack, or the reach of a flare boom, is determined by the thermal radiation that is permissible or tolerable for equipment or personnel to be exposed to. [ 11 ] For continuous exposure of personnel wearing appropriate industrial clothing a maximum radiation level of 1.58 kW/m 2 (500 Btu/hr.ft²) is recommended. Higher radiation levels are permissible but for reduced exposure times:
Ground flares are designed to hide the flame from sight and to reduce thermal radiation and noise. [ 10 ] They comprise a steel box or cylinder lined with refractory material. They are open at the top and have openings around the base to allow combustion air to enter. They may have an array of multiple flare tips to provide turndown capability and to spread the flame across the cross-section of the flare. They are generally used onshore in environmentally sensitive areas and have been used offshore on floating production storage and offloading installations (FPSOs). [ 10 ]
When crude oil is extracted and produced from oil wells , raw natural gas associated with the oil is brought to the surface as well. Especially in areas of the world lacking pipelines and other gas transportation infrastructure, vast amounts of such associated gas are commonly flared as waste or unusable gas. The flaring of associated gas may occur at the top of a vertical flare stack, or it may occur in a ground-level flare in an earthen pit. Preferably, associated gas is reinjected into the reservoir, which saves it for future use while maintaining higher well pressure and crude oil producibility. [ 12 ]
Advances in satellite monitoring, along with voluntary reporting, have revealed that about 150 × 10 9 cubic meters (5.3 × 10 12 cubic feet) of associated gas have been flared globally each year since at least the mid-1990s until 2020. [ 13 ] In 2011, that was equivalent to about 25 percent of the annual natural gas consumption in the United States or about 30 per cent of the annual gas consumption in the European Union . [ 7 ] At market, this quantity of gas—at a nominal value of $5.62 per 1000 cubic feet—would be worth US$29.8 billion. [ 14 ] Additionally, the waste is a significant source of carbon dioxide (CO 2 ) and other greenhouse gas emissions .
An important source of anthropogenic methane comes from the treatment and storage of organic waste material including waste water , animal waste and landfill. [ 15 ] Gas flares are used in any process that results in the generation and collection of biogas . As a result, gas flares are a standard component of an installation for controlling the production of biogas. [ 16 ] They are installed on landfill sites , waste water treatment plant and anaerobic digestion plant that use agriculturally or domestically produced organic waste to produce methane for use as a fuel or for heating.
Gas flares on biogas collection systems are used if the gas production rates are not sufficient to warrant use in any industrial process. However, on a plant where the gas production rate is sufficient for direct use in an industrial process that could be classified as part of the circular economy , and that may include the generation of electricity , the production of natural gas quality biogas for vehicle fuel [ 17 ] or for heating in buildings, drying refuse-derived fuel or leachate treatment, gas flares are used as a back-up system during down-time for maintenance or breakdown of generation equipment. In this latter case, generation of biogas cannot normally be interrupted, and a gas flare is employed to maintain the internal pressure on the biological process. [ 18 ]
There are two types of gas flare used for controlling biogas, open or enclosed. Open flares burn at a lower temperature, less than 1000 °C and are generally cheaper than enclosed flares that burn at a higher combustion temperature and are usually supplied to conform to a specific residence time of 0.3s within the chimney to ensure complete destruction of any toxic molecules contained within the biogas. [ citation needed ] Flare specification usually demands that enclosed flares must operate at >1000 °C and <1200 °C; this in order to ensure a 98% destruction efficiency and avoid the formation of NOx . [ 19 ]
The natural gas that is not combusted by a flare is vented into the atmosphere as methane. Methane 's estimated global warming potential is 28-36 times greater than that of CO 2 over the course of a century, and 84-87 times greater over two decades. [ 20 ] Natural gas flaring produces CO2 and many other compounds, depending on the chemical composition of the natural gas and on how well the natural gas burns in the flare. Therefore, to the extent that gas flares convert methane to CO 2 before it is released into the atmosphere, they reduce the amount of global warming that would otherwise occur. [ 21 ] [ 22 ]
Flaring emissions contributed to 270 Mt ( megatonnes ) of CO 2 in 2017 and reducing flaring emissions is thought to be an important component in curbing global warming. [ 23 ] An increasing number of governments and industries have pledged to eliminate or reduce flaring. [ 23 ] The Global Methane Pledge signed at COP26 , in which 111 nations committed to reducing methane emissions by at least 30 percent from 2020 levels by 2030, is also playing a role in raising the global focus on methane.
Additional noxious fumes emitted by flaring may include, aromatic hydrocarbons ( benzene , toluene , xylenes ) and benzo(a)pyrene , which are known to be carcinogenic. A 2013 study found that gas flares contributed over 40% of the black carbon deposited in the Arctic. [ 24 ] [ 25 ]
Flaring can affect wildlife by attracting birds and insects to the flame. Approximately 7,500 migrating songbirds were attracted to and killed by the flare at the liquefied natural gas terminal in Saint John, New Brunswick, Canada on September 13, 2013. [ 26 ] Similar incidents have occurred at flares on offshore oil and gas installations. [ 27 ] Moths are known to be attracted to lights. A brochure published by the Secretariat of the Convention on Biological Diversity describing the Global Taxonomy Initiative describes a situation where "a taxonomist working in a tropical forest noticed that a gas flare at an oil refinery was attracting and killing hundreds of these [hawk or sphinx] moths. Over the course of the months and years that the refinery was running a vast number of moths must have been killed, suggesting that plants could not be pollinated over a large area of forest". [ 28 ]
Flares release several different chemicals including: benzene , particulates , nitrogen oxides , heavy metals , black carbon , and carbon monoxide . Several of these pollutants correlate with preterm birth and reduced newborn birth weight . According to one study from 2020, pregnant women living near flaring natural gas and oil wells have reportedly experienced a 50% greater premature birth rate. [ 29 ] Flares may emit methane and other volatile organic compounds as well as sulfur dioxide and other sulfur compounds, which are known to exacerbate asthma and other respiratory disease . [ 30 ]
A 2021 study found that a 1% increase in flared natural gas increases the respiratory-related hospitalization rate by 0.73%. [ 31 ] | https://en.wikipedia.org/wiki/Gas_flare |
A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical.
The term often refers to a device that uses a rocket propellant to generate large quantities of gas. The gas is typically used to drive a turbine rather than to provide thrust as in a rocket engine . Gas generators of this type are used to power turbopumps in rocket engines, in a gas-generator cycle .
It is also used by some auxiliary power units to power electric generators and hydraulic pumps .
Another common use of the term is in the industrial gases industry, where gas generators are used to produce gaseous chemicals for sale. For example, the chemical oxygen generator , which delivers breathable oxygen at a controlled rate over a prolonged period. During World War II , portable gas generators that converted coke to producer gas were used to power vehicles as a way of alleviating petrol shortages.
Other types include the gas generator in an automobile airbag , which is designed to rapidly produce a specific quantity of inert gas.
The V-2 rocket used hydrogen peroxide decomposed by a liquid sodium permanganate catalyst solution as a gas generator. This was used to drive a turbopump to pressurize the main LOX - ethanol propellants. [ 1 ] In the Saturn V F-1 [ 2 ] [ 3 ] and Space Shuttle main engine , [ 4 ] some of the main propellant was burned to drive the turbopump (see gas-generator cycle and staged combustion cycle ). The gas generator in these designs uses a highly fuel-rich mix to keep flame temperatures relatively low.
The Space Shuttle auxiliary power unit [ 5 ] and the F-16 emergency power unit (EPU) [ 6 ] [ 7 ] use hydrazine as a fuel. The gas drives a turbine which drives hydraulic pumps . In the F-16 EPU it also drives an electric generator .
Gas generators have also been used to power torpedoes . For example, the US Navy Mark 16 torpedo was powered by hydrogen peroxide . [ 8 ]
A concentrated solution of hydrogen peroxide is known as high-test peroxide and decomposes to produce oxygen and water (steam).
Hydrazine decomposes to mixtures of nitrogen, hydrogen and ammonia. The reaction is strongly exothermic and produces high volume of hot gas from small volume of liquid.
Many solid chemical rocket propellant compositions can be used as gas generators. [ 9 ]
Many automobile airbags use sodium azide for inflation (as of 2003 [update] ). [ 10 ] A small pyrotechnic charge triggers its decomposition, producing nitrogen gas, which inflates the airbag in around 30 milliseconds. A typical airbag in the US might contain 130 grams of sodium azide. [ 11 ]
Similar gas generators are used for fire suppression. [ 12 ]
Sodium azide decomposes exothermically to sodium and nitrogen.
The resulting sodium is hazardous, so other materials are added, e.g. potassium nitrate and silica, to convert it to a silicate glass.
A chemical oxygen generator delivers breathable oxygen at a controlled rate over a prolonged period.
Sodium, potassium, and lithium chlorates and perchlorates are used.
A device that converts coke or other carbonaceous material into producer gas may be used as a source of fuel gas for industrial use. Portable gas generators of this type were used during World War II to power vehicles as a way of alleviating petrol shortages. [ 13 ] | https://en.wikipedia.org/wiki/Gas_generator |
A gas giant is a giant planet composed mainly of hydrogen and helium . [ 1 ] Jupiter and Saturn are the gas giants of the Solar System . The term "gas giant" was originally synonymous with " giant planet ". However, in the 1990s, it became known that Uranus and Neptune are a distinct class of giant planets composed mainly of heavier volatile substances (referred to as " ices "). For this reason, Uranus and Neptune are often classified in the separate category of ice giants . [ 2 ]
Jupiter and Saturn consist mostly of hydrogen and helium, with heavier elements making up between 3 and 13 percent of their mass. [ 3 ] They are thought to have an outer layer of compressed molecular hydrogen surrounding a layer of liquid metallic hydrogen , with a molten rocky core inside. The outermost portion of their hydrogen atmosphere contains many layers of visible clouds that are mostly composed of water and ammonia . The layer of metallic hydrogen located in the mid-interior makes up the bulk of every gas giant and is referred to as "metallic" because the very high atmospheric pressure turns hydrogen into an electrical conductor. The gas giants' cores are thought to consist of heavier elements at such high temperatures (20,000 K [19,700 °C ; 35,500 °F ]) and pressures that their properties are not yet completely understood. The placement of the solar system's gas giants can be explained by the grand tack hypothesis . [ 3 ]
The defining differences between a very low-mass brown dwarf (which can have a mass as low as roughly 13 times that of Jupiter [ 4 ] ) and a gas giant are debated. [ 5 ] One school of thought is based on formation, the other, on the physics of the interior. [ 5 ] Part of the debate concerns whether brown dwarfs must by definition have experienced nuclear fusion at some point in their history.
The term gas giant was coined in 1952 by the science fiction writer James Blish [ 6 ] and was originally used to refer to all giant planets . It is, arguably, something of a misnomer because throughout most of the volume of all giant planets, the pressure is so high that matter is not in gaseous form. [ 7 ] Other than solids in the core and the upper layers of the atmosphere, all matter is above the critical point , where there is no distinction between liquids and gases. [ 8 ] The term has nevertheless caught on, because planetary scientists typically use "rock", "gas", and "ice" as shorthands for classes of elements and compounds commonly found as planetary constituents, irrespective of what phase the matter may appear in. In the outer Solar System, hydrogen and helium are referred to as "gases"; water, methane, and ammonia as "ices"; and silicates and metals as "rocks". In this terminology, since Uranus and Neptune are primarily composed of ices, not gas, they are more commonly called ice giants and distinct from the gas giants.
Theoretically, gas giants can be divided into five distinct classes according to their modeled physical atmospheric properties, and hence their appearance: ammonia clouds (I), water clouds (II), cloudless (III), alkali-metal clouds (IV), and silicate clouds (V). Jupiter and Saturn are both class I. Hot Jupiters are class IV or V.
A cold hydrogen-rich gas giant more massive than Jupiter but less than about 500 M E ( 1.6 M J ) will only be slightly larger in volume than Jupiter. [ 9 ] For masses above 500 M E , gravity will cause the planet to shrink (see degenerate matter ). [ 9 ]
Kelvin–Helmholtz heating can cause a gas giant to radiate more energy than it receives from its host star. [ 10 ] [ 11 ]
Although the words "gas" and "giant" are often combined, hydrogen planets need not be as large as the familiar gas giants from the Solar System. However, smaller gas planets and planets closer to their star will lose atmospheric mass more quickly via hydrodynamic escape than larger planets and planets farther out. [ 12 ] [ 13 ]
A gas dwarf could be defined as a planet with a rocky core that has accumulated a thick envelope of hydrogen, helium and other volatiles, having as result a total radius between 1.7 and 3.9 Earth-radii. [ 14 ] [ 15 ]
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d , which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope. [ 16 ]
A low-mass gas planet can still have a radius resembling that of a gas giant if it has the right temperature. [ 17 ]
Heat that is funneled upward by local storms is a major driver of the weather on gas giants. [ 18 ] Much, if not all, of the deep heat escaping the interior flows up through towering thunderstorms. [ 18 ] These disturbances develop into small eddies that eventually form storms such as the Great Red Spot on Jupiter. [ 18 ] On Earth and Jupiter, lightning and the hydrologic cycle are intimately linked together to create intense thunderstorms. [ 18 ] During a terrestrial thunderstorm, condensation releases heat that pushes rising air upward. [ 18 ] This "moist convection" engine can segregate electrical charges into different parts of a cloud; the reuniting of those charges is lightning. [ 18 ] Therefore, we can use lightning to signal to us where convection is happening. [ 18 ] Although Jupiter has no ocean or wet ground, moist convection seems to function similarly compared to Earth. [ 18 ]
The Great Red Spot (GRS) is a high-pressure system located in Jupiter's southern hemisphere. [ 19 ] The GRS is a powerful anticyclone, swirling at about 430 to 680 kilometers per hour counterclockwise around the center. [ 19 ] The Spot has become known for its ferocity, even feeding on smaller Jovian storms. [ 19 ] Tholins are brown organic compounds found within the surface of various planets that are formed by exposure to UV irradiation. The tholins that exist on Jupiter's surface get sucked up into the atmosphere by storms and circulation; it is hypothesized that those tholins that become ejected from the regolith get stuck in Jupiter's GRS, causing it to be red.
Condensation of helium creates liquid helium rain on gas giants. On Saturn, this helium condensation occurs at certain pressures and temperatures when helium does not mix in with the liquid metallic hydrogen present on the planet. [ 20 ] Regions on Saturn where helium is insoluble allow the denser helium to form droplets and act as a source of energy, both through the release of latent heat and by descending deeper into the center of the planet. [ 21 ] This phase separation leads to helium droplets that fall as rain through the liquid metallic hydrogen until they reach a warmer region where they dissolve in the hydrogen. [ 20 ] Since Jupiter and Saturn have different total masses, the thermodynamic conditions in the planetary interior could be such that this condensation process is more prevalent in Saturn than in Jupiter. [ 21 ] Helium condensation could be responsible for Saturn's excess luminosity as well as the helium depletion in the atmosphere of both Jupiter and Saturn. [ 21 ]
Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of". | https://en.wikipedia.org/wiki/Gas_giant |
A gas heater is a space heater used to heat a room or outdoor area by burning natural gas , liquefied petroleum gas , propane , or butane .
Indoor household gas heaters can be broadly categorized in one of two ways: flued or non-flued, or vented and unvented .
The first gas heater made use of the same principles as the Bunsen burner . Beginning in 1881, the burner's flame was used to heat a structure made of asbestos , a design patented by Alice H.Parker, a England engineer .
The gas heater is able to warm up a whole room by first allowing the flame to heat the air locally, then it disperses throughout the air by convection . Today the same principle applies with outdoor patio heaters or "mushroom heaters" which act as giant Bunsen burners.
Modern gas heaters have been further developed to include units that utilize radiant heat technology, rather than the principles of the Bunsen burner. This form of technology does not spread via convection, but rather, is absorbed by people and objects in its path. This form of heating is useful for outdoor heating , where it is more economical than using a standard air heating system.
Flued heaters are permanently installed wherever they are placed. The flue , if properly installed with the correct overall height, size, and orientation should extract all of the heater emissions. A correctly operating flued gas heater is typically safe for use.
Non-flued heaters – also known as unvented heaters , vent-free heaters, or flueless fires, may be either permanently installed or portable, and sometimes incorporate a catalytic converter . [ 1 ] Non-flued heaters can be risky if appropriate safety procedures are not followed. There must be adequate ventilation, they must be kept clean, and they should always be switched off before sleeping. If operating correctly, the main emissions of a non-flued gas heater are water vapour , carbon dioxide , and nitrogen dioxide .
Home gas heating controls cycle using a mechanical or electronic thermostat . Gas flow is actuated with a valve. Ignition is by an electric filament or pilot light . Flames heat a radiator in the air duct but outside the flue, convection or a fan may distribute the heat. | https://en.wikipedia.org/wiki/Gas_heater |
Gas hydrate stability zone , abbreviated GHSZ , also referred to as methane hydrate stability zone ( MHSZ ) or hydrate stability zone ( HSZ ), refers to a zone and depth of the marine environment at which methane clathrates naturally exist in the Earth's crust .
Gas hydrate stability primarily depends upon temperature and pressure , however other variables such as gas composition and ionic impurities in water influence stability boundaries. [ 1 ] The existence and depth of a hydrate deposit is often indicated by the presence of a bottom-simulating reflector (BSR). A BSR is a seismic reflection indicating the lower limit of hydrate stability in sediments due to the different densities of hydrate saturated sediments, normal sediments and those containing free gas. [ 2 ]
The upper and lower limits of the HSZ, as well as its thickness, depend upon the local conditions in which the hydrate occurs. The conditions for hydrate stability generally restrict natural deposits to polar regions and deep oceanic regions. In polar regions, due to low temperatures, the upper limit of the hydrate stability zone occurs at a depth of approximately 150 meters . 1 [ citation needed ] The maximal depth of the hydrate stability zone is limited by the geothermal gradient . Along continental margins the average thickness of the HSZ is about 500 m. [ 3 ] The upper limit in oceanic sediments occurs when bottom water temperatures are at or near 0 °C , and at a water depth of approximately 300 meters. 1 [ citation needed ] The lower limit of the HSZ is bounded by the geothermal gradient. As depth below seafloor increases, the temperature eventually becomes too high for hydrates to exist. In areas of high geothermal heat flow, the lower limit of the HSZ may become shallower, therefore decreasing the thickness of the HSZ. Conversely, the thickest hydrate layers and widest HSZ are observed in areas of low geothermal heat flow. Generally, the maximum depth of HSZ extension is 2000 meters below the Earth's surface. 1,3 [ citation needed ] Using the location of a BSR, as well as the pressure-temperature regimen necessary for hydrate stability, the HSZ may be used to determine geothermal gradients. 2 [ citation needed ]
If processes such as sedimentation or subduction transport hydrates below the lower limit of the HSZ, the hydrate becomes unstable and disassociates, releasing gas. This free gas may become trapped beneath the overlying hydrate layer, forming gas pockets, or reservoirs. The pressure from the presence of gas reservoirs impacts the stability of the hydrate layer. If this pressure is substantially changed, the stability of the methane layer above will be altered and may result in significant destabilization and disassociation of the hydrate deposit. [ 4 ] Landslides of rock or sediment above the hydrate stability zone may also impact the hydrate stability. A sudden decrease in pressure can release gasses or destabilize portions of the hydrate deposit. [ 5 ] Changing atmospheric and oceanic temperatures may impact the presence and depth of the hydrate stability zone, however, is still uncertain to what extent. In oceanic sediments, increasing pressure due to a rise in sea level may offset some of the impact of increasing temperature upon the hydrate stability equilibrium. 1 [ citation needed ] | https://en.wikipedia.org/wiki/Gas_hydrate_stability_zone |
In quantum mechanics , the results of the quantum particle in a box can be used to look at the equilibrium situation for a quantum ideal gas in a box which is a box containing a large number of molecules which do not interact with each other except for instantaneous thermalizing collisions. This simple model can be used to describe the classical ideal gas as well as the various quantum ideal gases such as the ideal massive Fermi gas , the ideal massive Bose gas as well as black body radiation ( photon gas ) which may be treated as a massless Bose gas, in which thermalization is usually assumed to be facilitated by the interaction of the photons with an equilibrated mass.
Using the results from either Maxwell–Boltzmann statistics , Bose–Einstein statistics or Fermi–Dirac statistics , and considering the limit of a very large box, the Thomas–Fermi approximation (named after Enrico Fermi and Llewellyn Thomas ) is used to express the degeneracy of the energy states as a differential, and summations over states as integrals. This enables thermodynamic properties of the gas to be calculated with the use of the partition function or the grand partition function . These results will be applied to both massive and massless particles. More complete calculations will be left to separate articles, but some simple examples will be given in this article.
For both massive and massless particles in a box , the states of a particle are
enumerated by a set of quantum numbers [ n x , n y , n z ] . The magnitude of the momentum is given by
where h is the Planck constant and L is the length of a side of the box. Each possible state of a particle can be thought of as a point on a 3-dimensional grid of positive integers. The distance from the origin to any point will be
Suppose each set of quantum numbers specify f states where f is the number of internal degrees of freedom of the particle that can be altered by collision. For example, a spin 1 ⁄ 2 particle would have f = 2 , one for each spin state. For large values of n , the number of states with magnitude of momentum less than or equal to p from the above equation is approximately
which is just f times the volume of a sphere of radius n divided by eight since only the octant with positive n i is considered. Using a continuum approximation , the number of states with magnitude of momentum between p and p + dp is therefore
where V = L 3 is the volume of the box. Notice that in using this continuum approximation, also known as Thomas−Fermi approximation , the ability to characterize the low-energy states is lost, including the ground state where n i = 1 . For most cases this will not be a problem, but when considering Bose–Einstein condensation , in which a large portion of the gas is in or near the ground state , the ability to deal with low energy states becomes important.
Without using any approximation, the number of particles with energy ε i is given by
where g i {\displaystyle g_{i}} is the degeneracy of state i and Φ ( ε i ) = { e β ( ε i − μ ) , for particles obeying Maxwell-Boltzmann statistics e β ( ε i − μ ) − 1 , for particles obeying Bose-Einstein statistics e β ( ε i − μ ) + 1 , for particles obeying Fermi-Dirac statistics {\displaystyle \Phi (\varepsilon _{i})={\begin{cases}e^{\beta (\varepsilon _{i}-\mu )},&{\text{for particles obeying Maxwell-Boltzmann statistics}}\\e^{\beta (\varepsilon _{i}-\mu )}-1,&{\text{for particles obeying Bose-Einstein statistics}}\\e^{\beta (\varepsilon _{i}-\mu )}+1,&{\text{for particles obeying Fermi-Dirac statistics}}\\\end{cases}}} with β = 1/ k B T , the Boltzmann constant k B , temperature T , and chemical potential μ . (See Maxwell–Boltzmann statistics , Bose–Einstein statistics , and Fermi–Dirac statistics .)
Using the Thomas−Fermi approximation, the number of particles dN E with energy between E and E + dE is:
where d g E {\displaystyle dg_{E}} is the number of states with energy between E and E + dE .
Using the results derived from the previous sections of this article, some distributions for the gas in a box can now be determined. For a system of particles, the distribution P A {\displaystyle P_{A}} for a variable A {\displaystyle A} is defined through the expression P A d A {\displaystyle P_{A}dA} which is the fraction of particles that have values for A {\displaystyle A} between A {\displaystyle A} and A + d A {\displaystyle A+dA}
where
It follows that:
For a momentum distribution P p {\displaystyle P_{p}} , the fraction of particles with magnitude of momentum between p {\displaystyle p} and p + d p {\displaystyle p+dp} is:
and for an energy distribution P E {\displaystyle P_{E}} , the fraction of particles with energy between E {\displaystyle E} and E + d E {\displaystyle E+dE} is:
For a particle in a box (and for a free particle as well), the relationship between energy E {\displaystyle E} and momentum p {\displaystyle p} is different for massive and massless particles. For massive particles,
while for massless particles,
where m {\displaystyle m} is the mass of the particle and c {\displaystyle c} is the speed of light.
Using these relationships,
The following sections give an example of results for some specific cases.
For this case:
Integrating the energy distribution function and solving for N gives
Substituting into the original energy distribution function gives
which are the same results obtained classically for the Maxwell–Boltzmann distribution . Further results can be found in the classical section of the article on the ideal gas .
For this case:
where z = e β μ . {\displaystyle z=e^{\beta \mu }.}
Integrating the energy distribution function and solving for N gives the particle number
where Li s ( z ) is the polylogarithm function. The polylogarithm term must always be positive and real, which means its value will go from 0 to ζ (3/2) as z goes from 0 to 1. As the temperature drops towards zero, Λ will become larger and larger, until finally Λ will reach a critical value Λ c where z = 1 and
where ζ ( z ) {\displaystyle \zeta (z)} denotes the Riemann zeta function . The temperature at which Λ = Λ c is the critical temperature. For temperatures below this critical temperature, the above equation for the particle number has no solution. The critical temperature is the temperature at which a Bose–Einstein condensate begins to form. The problem is, as mentioned above, that the ground state has been ignored in the continuum approximation. It turns out, however, that the above equation for particle number expresses the number of bosons in excited states rather well, and thus:
where the added term is the number of particles in the ground state. The ground state energy has been ignored. This equation will hold down to zero temperature. Further results can be found in the article on the ideal Bose gas .
For the case of massless particles, the massless energy distribution function must be used. It is convenient to convert this function to a frequency distribution function:
where Λ is the thermal wavelength for massless particles. The spectral energy density (energy per unit volume per unit frequency) is then
Other thermodynamic parameters may be derived analogously to the case for massive particles. For example, integrating the frequency distribution function and solving for N gives the number of particles:
The most common massless Bose gas is a photon gas in a black body . Taking the "box" to be a black body cavity, the photons are continually being absorbed and re-emitted by the walls. When this is the case, the number of photons is not conserved. In the derivation of Bose–Einstein statistics , when the restraint on the number of particles is removed, this is effectively the same as setting the chemical potential ( μ ) to zero. Furthermore, since photons have two spin states, the value of f is 2. The spectral energy density is then
which is just the spectral energy density for Planck's law of black body radiation . Note that the Wien distribution is recovered if this procedure is carried out for massless Maxwell–Boltzmann particles, which approximates a Planck's distribution for high temperatures or low densities.
In certain situations, the reactions involving photons will result in the conservation of the number of photons (e.g. light-emitting diodes , "white" cavities). In these cases, the photon distribution function will involve a non-zero chemical potential. (Hermann 2005)
Another massless Bose gas is given by the Debye model for heat capacity . This model considers a gas of phonons in a box and differs from the development for photons in that the speed of the phonons is less than light speed, and there is a maximum allowed wavelength for each axis of the box. This means that the integration over phase space cannot be carried out to infinity, and instead of results being expressed in polylogarithms, they are expressed in the related Debye functions .
For this case:
Integrating the energy distribution function gives
where again, Li s ( z ) is the polylogarithm function and Λ is the thermal de Broglie wavelength . Further results can be found in the article on the ideal Fermi gas . Applications of the Fermi gas are found in the free electron model , the theory of white dwarfs and in degenerate matter in general. | https://en.wikipedia.org/wiki/Gas_in_a_box |
The results of the quantum harmonic oscillator can be used to look at the equilibrium situation for a quantum ideal gas in a harmonic trap , which is a harmonic potential containing a large number of particles that do not interact with each other except for instantaneous thermalizing collisions. This situation is of great practical importance since many experimental studies of Bose gases are conducted in such harmonic traps.
Using the results from either Maxwell–Boltzmann statistics , Bose–Einstein statistics or Fermi–Dirac statistics we use the Thomas–Fermi approximation (gas in a box) and go to the limit of a very large trap, and express the degeneracy of the energy states ( g i {\displaystyle g_{i}} ) as a differential, and summations over states as integrals. We will then be in a position to calculate the thermodynamic properties of the gas using the partition function or the grand partition function . Only the case of massive particles will be considered, although the results can be extended to massless particles as well, much as was done in the case of the ideal gas in a box . More complete calculations will be left to separate articles, but some simple examples will be given in this article.
For massive particles in a harmonic well, the states of the particle are enumerated by a set of quantum numbers [ n x , n y , n z ] {\displaystyle [n_{x},n_{y},n_{z}]} . The energy of a particular state is given by:
Suppose each set of quantum numbers specify f {\displaystyle f} states where f {\displaystyle f} is the number of internal degrees of freedom of the particle that can be altered by collision. For example, a spin-1/2 particle would have f = 2 {\displaystyle f=2} , one for each spin state. We can think of each possible state of a particle as a point on a 3-dimensional grid of positive integers. The Thomas–Fermi approximation assumes that the quantum numbers are so large that they may be considered to be a continuum. For large values of n {\displaystyle n} , we can estimate the number of states with energy less than or equal to E {\displaystyle E} from the above equation as:
which is just f {\displaystyle f} times the volume of the tetrahedron formed by the plane described by the energy equation and the bounding planes of the positive octant. The number of states with energy between E {\displaystyle E} and E + d E {\displaystyle E+dE} is therefore:
Notice that in using this continuum approximation, we have lost the ability to characterize the low-energy states, including the ground state where n i = 0 {\displaystyle n_{i}=0} . For most cases this will not be a problem, but when considering Bose–Einstein
condensation, in which a large portion of the gas is in or near the ground state, we will need to recover the ability to deal with low energy states.
Without using the continuum approximation, the number of particles with energy ϵ i {\displaystyle \epsilon _{i}} is given by:
where
with β = 1 / k T {\displaystyle \beta =1/kT} , with k {\displaystyle k} being the Boltzmann constant , T {\displaystyle T} being temperature , and μ {\displaystyle \mu } being the chemical potential . Using the continuum approximation, the number of particles d N {\displaystyle dN} with energy between E {\displaystyle E} and E + d E {\displaystyle E+dE} is now written:
We are now in a position to determine some distribution functions for the "gas in a harmonic trap." The distribution function for any variable A {\displaystyle A} is P A d A {\displaystyle P_{A}dA} and is equal to the fraction of particles which have values for A {\displaystyle A} between A {\displaystyle A} and A + d A {\displaystyle A+dA} :
It follows that:
Using these relationships we obtain the energy distribution function:
The following sections give an example of results for some specific cases.
For this case:
Integrating the energy distribution function and solving for N {\displaystyle N} gives:
Substituting into the original energy distribution function gives:
For this case:
where z {\displaystyle z} is defined as:
Integrating the energy distribution function and solving for N {\displaystyle N} gives:
where L i s ( z ) {\displaystyle \mathrm {Li} _{s}(z)} is the polylogarithm function. The polylogarithm term must always be positive and real, which means its value will go from 0 to ζ ( 3 ) {\displaystyle \zeta (3)} as z {\displaystyle z} goes from 0 to 1. As the temperature goes to zero, β {\displaystyle \beta } will become larger and larger, until finally β {\displaystyle \beta } will reach a critical value β c {\displaystyle \beta _{\text{c}}} , where z = 1 {\displaystyle z=1} and
The temperature at which β = β c {\displaystyle \beta =\beta _{c}} is the critical temperature at which a Bose–Einstein condensate begins to form. The problem is, as mentioned above, the ground state has been ignored in the continuum approximation. It turns out that the above expression expresses the number of bosons in excited states rather well, and so we may write:
where the added term is the number of particles in the ground state. (The ground state energy has been ignored.) This equation will hold down to zero temperature. Further results can be found in the article on the ideal Bose gas .
For this case:
Integrating the energy distribution function gives:
where again, L i s ( z ) {\displaystyle \mathrm {Li} _{s}(z)} is the polylogarithm function. Further results can be found in the article on the ideal Fermi gas . | https://en.wikipedia.org/wiki/Gas_in_a_harmonic_trap |
Gas in scattering media absorption spectroscopy ( GASMAS ) is an optical technique for sensing and analysis of gas located within porous and highly scattering solids, e.g. powders, ceramics, wood, fruit, translucent packages, pharmaceutical tablets, foams, human paranasal sinuses etc. It was introduced in 2001 by Prof. Sune Svanberg and co-workers at Lund University (Sweden). [ 1 ] The technique is related to conventional high-resolution laser spectroscopy for sensing and spectroscopy of gas (e.g. tunable diode laser absorption spectroscopy , TDLAS), but the fact that the gas here is "hidden" inside solid materials give rise to important differences.
Free gases exhibit very sharp spectral features, and different gas species have their own unique spectral fingerprints. At atmospheric pressure, absorption linewidths are typically on the order of 0.1 cm −1 (i.e. ~3 GHz in optical frequency or 0.006 nm in wavelength), while solid media have dull spectral behavior with absorption features thousand times wider. By looking for the sharp absorption imprints in light emerging from porous samples, it is thus possible to detect gases confined in solids – even though the solid often attenuates light much stronger than the gas itself.
The basic principle of GASMAS is shown in figure 1. Laser light is sent into a sample with gas cavities, which could either be small pores (left) or larger gas-filled chambers. The heterogeneous nature of the porous material often give rise to strong light scattering, and pathlengths are often surprisingly long (10 or 100 times the sample dimension are not uncommon). In addition, light will experience absorption related to the solid material. When travelling through the material, light will travel partly through the pores, and will thus experience the spectrally sharp gas absorption. Light leaving the material will carry this information, and can be collected by a detector either in a transmission mode (left) or in a reflection mode (right).
In order to detect the spectrally sharp fingerprints related to the gas, GASMAS has so far relied on high-resolution tunable diode laser absorption spectroscopy (TDLAS). In principle, this means that a nearly monochromatic (narrow-bandwidth) laser is scanned across an absorption line of the gas, and a detector records the transmission profile. In order to increase sensitivity, modulation techniques are often employed.
The strength of the gas absorption will depend, as given by the Beer-Lambert law , both on the gas concentration and the path-length that the light has travelled through the gas. In conventional TDLAS, the path-length is known and the concentration is readily calculated from the transmittance. In GASMAS, extensive scattering renders the pathlength unknown and the determination of gas concentration is aggravated. In many applications, however, the gas concentration is known and other parameters are in focus. Furthermore, as discussed in 2.2, there are complementing techniques that can provide information on the optical pathlength, thus allowing evaluation also of gas concentrations.
It is well known that optical interference often is a major problem in laser-based gas spectroscopy. [ 2 ] [ 3 ] In conventional laser-based gas spectrometers, the optical interference originates from e.g. etalon-type interference effects in (or between) optical components and multi-pass gas cells. Throughout the years, great efforts have been devoted to handle this problem. Proper optical design is important to minimize interference from the beginning (e.g. by tilting optical components, avoiding transmissive optics and using anti-reflection coating), but interference patterns can not be completely avoided and are often difficult to separate from gas absorption. Since gas spectroscopy often involves measurement of small absorption fractions (down to 10 −7 ), appropriate handling of interference is crucial. Utilised countermeasures include customized optical design, [ 4 ] tailored laser modulation, [ 5 ] mechanical dithering, [ 6 ] [ 7 ] [ 8 ] [ 9 ] signal post-processing, [ 10 ] sample modulation, [ 8 ] [ 11 ] [ 12 ] and baseline recording and interference subtraction. [ 13 ]
In the case of GASMAS, optical interference is particularly cumbersome. [ 14 ] This is related to the severe speckle-type interference that originates from the interaction between laser light and highly scattering solid materials. [ 9 ] Since this highly non-uniform interference is generated in same place as the utility signal, it cannot be removed by design. The optical properties of the porous material under study determines the interference pattern, and the level of interference is not seldom much stronger than actual gas absorption signals. Random mechanical dithering (e.g. laser beam dithering and/or sample rotation ) has been found effective in GASMAS. [ 9 ] [ 15 ] However, this approach converts stable interference into a random noise that must be averaged away, thus requiring longer acquisition times. Baseline recording and interference subtraction may be applicable in some GASMAS applications, as may other of the methods described above.
See [ 16 ] [ 17 ]
See [ 18 ]
See [ 19 ]
See [ 9 ] [ 15 ] [ 18 ]
Much of the food that we consume today is put in a wide variety of packages to ensure food quality and provide a possibility for transportation and distribution. Many of these packages are air or gas tight, making it difficult to study the gas composition without perforation. In many cases it is of great value to study the composition of gases without destroying the package.
The perhaps best example is studies of the amount of oxygen in food packages. Oxygen is naturally present in most food and food packages as it is a major component in air. However, oxygen is also one of the great causes or needs for aging of biological substances, due to its source for increase of chemical and microbiological activity. Today, methods like [Modified atmosphere] (MAP) and [Controlled atmosphere] packaging (CAP) are implemented to reduce and control the oxygen content in food packages to prolong [shelf life] and ensure safe food. To assure the effectiveness of these methods it is important to regularly measure the concentration of oxygen (and other gases) inside these packages. GASMAS provides the possibility of doing this non-intrusively, without destroying any food or packages. The two main advantages of measuring the gas-composition in packages without perforation is that no food is wasted in the controlling process and that the same package can be controlled repeatedly during an extended time period to monitor any time-dependence of the gas composition. The studies can be used to guarantee the tightness of packages but also to study food deterioration processes.
Much food itself contains free gas distributed in pores within. Examples are fruit, bread, flour, beans, cheese, etc. Also this gas can be of great value to study to monitor quality and maturity level (see e.g. [ 20 ] and [ 21 ] ).
See [ 22 ] [ 23 ] [ 24 ] | https://en.wikipedia.org/wiki/Gas_in_scattering_media_absorption_spectroscopy |
Gas kinetics is a science in the branch of fluid dynamics , concerned with the study of motion of gases and its effects on physical systems . Based on the principles of fluid mechanics and thermodynamics , gas dynamics arises from the studies of gas flows in transonic and supersonic flights . To distinguish itself from other sciences in fluid dynamics, the studies in gas dynamics are often defined with gases flowing around or within physical objects at speeds comparable to or exceeding the speed of sound and causing a significant change in temperature and pressure . [ 1 ] Some examples of these studies include but are not limited to: choked flows in nozzles and valves , shock waves around jets , aerodynamic heating on atmospheric reentry vehicles and flows of gas fuel within a jet engine . At the molecular level , gas dynamics is a study of the kinetic theory of gases , often leading to the study of gas diffusion , statistical mechanics , chemical thermodynamics and non-equilibrium thermodynamics . [ 2 ] Gas dynamics is synonymous with aerodynamics when the gas field is air and the subject of study is flight . It is highly relevant in the design of aircraft and spacecraft and their respective propulsion systems .
Progress in gas dynamics coincides with the developments of transonic and supersonic flights. As aircraft began to travel faster, the density of air began to change, considerably increasing the air resistance as the air speed approached the speed of sound . The phenomenon was later identified in wind tunnel experiments as an effect caused by the formation of shock waves around the aircraft. Major advances were made to describe the behavior during and after World War II , and the new understandings on compressible and high speed flows became theories of gas dynamics.
As the construct that gases are small particles in Brownian motion became widely accepted and numerous quantitative studies verifying that the macroscopic properties of gases, such as temperature, pressure and density , are the results of collisions of moving particles, [ 3 ] the study of kinetic theory of gases became increasingly an integrated part of gas dynamics. Modern books and classes on gas dynamics often began with an introduction to kinetic theory. [ 2 ] [ 4 ] The advent of the molecular modeling in computer simulation further made kinetic theory a highly relevant subject in today's research on gas dynamics. [ 5 ] [ 6 ]
Gas dynamics is the overview of the average value in the distance between two molecules of gas that has collided with out ignoring the structure in which the molecules are contained. The field requires a great amount of knowledge and practical use in the ideas of the kinetic theory of gases, and it links the kinetic theory of gases with the solid state physics through the study of how gas reacts with surfaces. [ 7 ]
Fluids are substances that do not permanently change under an enormous amount of stress. A solid tends to deform in order to remain at equilibrium under a great deal of stress. Fluids are defined as both liquids and gases because the molecules inside the fluid are much weaker than those molecules contained in a solid. When referring to the density of a fluid in terms of a liquid, there is a small percentage of change to the liquid’s density as pressure is increased. If the fluid is referred to as a gas, the density will change greatly depending on the amount of pressure applied due to the equation of state for gases (p=ρRT). In the study of the flow of liquids, the term used while referring to the little change in density is called incompressible flow. In the study of the flow of gases, the rapid increase due to an increase of pressure is called compressible flow. [ 8 ]
Real gases are characterized by their compressibility (z) in the equation PV = zn 0 RT . When the pressure P is set as a function of the volume V where the series is determined by set temperatures T , P , and V began to take hyperbolic relationships that are exhibited by ideal gases as the temperatures start to get very high. A critical point is reached when the slope of the graph is equal to zero and makes the state of the fluid change between a liquid and a vapor. The properties of ideal gases contain viscosity, thermal conductivity , and diffusion. [ 4 ]
The viscosity of gases is the result in the transfer of each molecule of gas as they pass each other from layer to layer. As gases tend to pass one another, the velocity, in the form of momentum, of the faster moving molecule speeds up the slower moving molecule. As the slower moving molecule passes the faster moving molecule, the momentum of the slower moving particle slows down the faster moving particle. The molecules continue to enact until frictional drag causes both molecules to equalize their velocities. [ 4 ]
The thermal conductivity of a gas can be found through analysis of a gas’ viscosity except the molecules are stationary while only the temperatures of the gases are changing. Thermal conductivity is stated as the amount of heat transported across a specific area in a specific time. The thermal conductivity always flows opposite of the direction of the temperature gradient. [ 4 ]
Diffusion of gases is configured with a uniform concentration of gases and while the gases are stationary. Diffusion is the change of concentration between the two gases due to a weaker concentration gradient between the two gases. Diffusion is the transportation of mass over a period of time. [ 4 ]
The shock wave may be described as a compression front in a supersonic flow field, and the flow process across the front results in an abrupt change in fluid properties. The thickness of the shock wave is comparable to the mean free path of the gas molecules in the flow field. [ 1 ] In other words, shock is a thin region where large gradients in temperature, pressure and velocity occur, and where the transport phenomena of momentum and energy are important. The normal shock wave is a compression front normal to the flow direction. However, in a wide variety of physical situations, a compression wave inclined at an angle to the flow occurs. Such a wave is called an oblique shock. Indeed, all naturally occurring shocks in external flows are oblique. [ 9 ]
A stationary normal shock wave is classified as going in the normal direction of the flow direction. For example, when a piston moves at a constant rate inside a tube, sound waves that travel down the tube are produced. As the piston continues to move, the wave begins to come together and compresses the gas inside the tube. The various calculations that come alongside of normal shock waves can vary due to the size of the tubes in which they are contained. Abnormalities such as converging-diverging nozzles and tubes with changing areas can affect such calculations as volume, pressure, and Mach number. [ 10 ]
Unlike stationary normal shockwaves, moving normal shockwaves are more commonly available in physical situations. For example, a blunt object entering into the atmosphere faces a shock that comes through the medium of a non-moving gas. The fundamental problem that comes through moving normal shockwaves is the moment of a normal shockwave through motionless gas. The viewpoint of the moving shockwaves characterizes it as a moving or non-moving shock wave. The example of an object entering into the atmosphere depicts an object traveling in the opposite direction of the shockwave resulting in a moving shockwave, but if the object was launching into space, riding on top of the shockwave, it would appear to be a stationary shockwave. The relations and comparisons along with speed and shock ratios of moving and stationary shockwaves can be calculated through extensive formulas. [ 11 ]
Frictional forces play a role in determining the flow properties of compressible flow in ducts. In calculations, friction is either taken as inclusive or exclusive. If friction is inclusive, then the analysis of compressible flow becomes more complex as if friction is not inclusive. If the friction is exclusive to the analysis, then certain restrictions will be put into place. When friction is included on compressible flow, the friction limits the areas in which the results from analysis in be applied. As mentioned before, the shape of the duct, such as varying sizes or nozzles, effect the different calculations in between friction and compressible flow. [ 12 ]
Important concepts
Flows of interest
Experimental techniques
Visualisation methods
Computational techniques | https://en.wikipedia.org/wiki/Gas_kinetics |
The laws describing the behaviour of gases under fixed pressure , volume , amount of gas, and absolute temperature conditions are called gas laws . The basic gas laws were discovered by the end of the 18th century when scientists found out that relationships between pressure, volume and temperature of a sample of gas could be obtained which would hold to approximation for all gases. The combination of several empirical gas laws led to the development of the ideal gas law .
The ideal gas law was later found to be consistent with atomic and kinetic theory .
In 1643, the Italian physicist and mathematician, Evangelista Torricelli , who for a few months had acted as Galileo Galilei's secretary, conducted a celebrated experiment in Florence. [ 1 ] He demonstrated that a column of mercury in an inverted tube can be supported by the pressure of air outside of the tube, with the creation of a small section of vacuum above the mercury. [ 2 ] This experiment essentially paved the way towards the invention of the barometer, as well as drawing the attention of Robert Boyle , then a "skeptical" scientist working in England. Boyle was inspired by Torricelli's experiment to investigate how the elasticity of air responds to varying pressure, and he did this through a series of experiments with a setup reminiscent of that used by Torricelli. [ 3 ] Boyle published his results in 1662.
Later on, in 1676, the French physicist Edme Mariotte , independently arrived at the same conclusions of Boyle, while also noting some dependency of air volume on temperature. [ 4 ] However it took another century and a half for the development of thermometry and recognition of the absolute zero temperature scale, which eventually allowed the discovery of temperature-dependent gas laws.
In 1662, Robert Boyle systematically studied the relationship between the volume and pressure of a fixed amount of gas at a constant temperature. He observed that the volume of a given mass of a gas is inversely proportional to its pressure at a constant temperature.
Boyle's law, published in 1662, states that, at a constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system is always constant. It can be verified experimentally using a pressure gauge and a variable volume container. It can also be derived from the kinetic theory of gases : if a container, with a fixed number of molecules inside, is reduced in volume, more molecules will strike a given area of the sides of the container per unit time, causing a greater pressure.
Boyle's law states that:
The concept can be represented with these formulae:
P 1 V 1 = P 2 V 2 {\displaystyle P_{1}V_{1}=P_{2}V_{2}} where P is the pressure, V is the volume of a gas, and k 1 is the constant in this equation (and is not the same as the proportionality constants in the other equations).
Charles' law, or the law of volumes, was founded in 1787 by Jacques Charles . It states that, for a given mass of an ideal gas at constant pressure, the volume is directly proportional to its absolute temperature , assuming in a closed system.
The statement of Charles' law is as follows:
the volume (V) of a given mass of a gas, at constant pressure (P), is directly proportional to its temperature (T).
Charles' law states that:
Therefore,
where "V" is the volume of a gas, "T" is the absolute temperature and k 2 is a proportionality constant (which is not the same as the proportionality constants in the other equations in this article).
Gay-Lussac's law, Amontons' law or the pressure law was founded by Joseph Louis Gay-Lussac in 1808.
Gay-Lussac's law states that:
Therefore,
P 1 T 1 = P 2 T 2 {\displaystyle {P_{1} \over T_{1}}={P_{2} \over T_{2}}} ,
Avogadro's law , Avogadro's hypothesis , Avogadro's principle or Avogadro-Ampère's hypothesis is an experimental gas law which was hypothesized by Amedeo Avogadro in 1811. It related the volume of a gas to the amount of substance of gas present. [ 5 ]
Avogadro's law states that:
This statement gives rise to the molar volume of a gas, which at STP (273.15 K, 1 atm) is about 22.4 L. The relation is given by:
The combined gas law or general gas equation is obtained by combining Boyle's law, Charles's law, and Gay-Lussac's law. It shows the relationship between the pressure, volume, and temperature for a fixed mass of gas:
This can also be written as:
With the addition of Avogadro's law , the combined gas law develops into the ideal gas law :
An equivalent formulation of this law is:
These equations are exact only for an ideal gas , which neglects various intermolecular effects (see real gas ). However, the ideal gas law is a good approximation for most gases under moderate pressure and temperature.
This law has the following important consequences: | https://en.wikipedia.org/wiki/Gas_laws |
A gas leak refers to a leak of natural gas or another gaseous product from a pipeline or other containment into any area where the gas should not be present. Gas leaks can be hazardous to health as well as the environment. Even a small leak into a building or other confined space may gradually build up an explosive or lethal gas concentration. [ 1 ] Natural gas leaks and the escape of refrigerant gas into the atmosphere are especially harmful, because of their global warming potential and ozone depletion potential . [ 2 ]
Leaks of gases associated with industrial operations and equipment are also generally known as fugitive emissions . Natural gas leaks from fossil fuel extraction and use are known as fugitive gas emissions . Such unintended leaks should not be confused with similar intentional types of gas release, such as:
Gas leaks should also not be confused with "gas seepage" from the earth or oceans - either natural or due to human activity.
Pure natural gas is colorless and odorless and is composed primarily of methane . Unpleasant scents in the form of traces of mercaptans are usually added, to assist in identifying leaks. This odor may be perceived as rotting eggs or a faintly unpleasant skunk smell. Persons detecting the odor must evacuate the area and abstain from using open flames or operating electrical equipment, to reduce the risk of fire and explosion.
As a result of the Pipeline Safety Improvement Act [ 3 ] of 2002 passed in the United States, federal safety standards require companies providing natural gas to conduct safety inspections for gas leaks in homes and other buildings receiving natural gas. The gas company is required to inspect gas meters and inside gas piping from the point of entry into the building to the outlet side of the gas meter for gas leaks. This may require entry into private homes by the natural gas companies to check for hazardous conditions.
Gas leaks can damage or kill plants. [ 4 ] [ 5 ] In addition to leaks from natural gas pipes, methane and other gases migrating from landfill garbage disposal sites can also cause chlorosis and necrosis in grass, weeds, or trees. [ 6 ] In some cases, leaking gas may migrate as far as 100 feet (30 m) from the source of the leak to an affected tree. [ 7 ]
Methane is an asphyxiant gas which can reduce the normal oxygen concentration in breathing air. Small animals and birds are also more sensitive to toxic gas like carbon monoxide that are sometimes present with natural gas. The expression "canary in a coal mine" derives from the historical practice of using a canary as an animal sentinel to detect dangerously high concentrations of naturally occurring coal gas . [ 8 ]
Methane, the primary constituent of natural gas, is up to 120 times as potent a greenhouse gas as carbon dioxide . Thus, the release of unburned natural gas produces much stronger effects than the carbon dioxide that would have been released if the gas had been burned as intended. [ 9 ]
In the United States, most state and federal agencies have adopted the Gas Piping and Technology Committee (GPTC) standards for grading natural gas leaks.
A Grade 1 leak is a leak that represents an existing or probable hazard to persons or property, and requires immediate repair or continuous action until the conditions are no longer hazardous.
Examples of a Grade 1 leak are:
A Grade 2 leak is a leak that is recognized as being non-hazardous at the time of detection, but justifies scheduled repair based on probable future hazard.
Examples of a Grade 2 Leak are:
A Grade 3 leak is non-hazardous at the time of detection and can be reasonably expected to remain non-hazardous.
Examples of a Grade 3 Leak are:
In 2012, Boston University professor Nathan Phillips and his students drove along all 785 miles (1,263 km) of Boston roads with a gas sensor , identifying 3300 leaks. [ 9 ] The Conservation Law Foundation produced a map showing around 4000 leaks reported to the Massachusetts Department of Public Utilities. [ 9 ] In July 2014, the Environmental Defense Fund released an interactive online map based on gas sensors attached to three mapping cars which already were being driven along Boston streets to update Google Earth Street View . This survey differed from the previous studies in that an estimate of leak severity was produced, rather than just leak detection . This map should help the gas utility to prioritize leak repairs, as well as raising public awareness of the problem. [ 9 ]
In 2017, Rhode Island released an estimated 15.7 million metric tons of greenhouse gases, about a third of which comes from leaks in natural gas pipes. This figure, published in 2019, was calculated based on an assumed leakage rate of 2.7% (as that is the rate of leakage in the nearby city of Boston). The study's authors estimated that fixing the leaks would incur an annual cost of $1.6 billion to $4 billion. [ 10 ]
In 2021, University of Geoscience(Beijing) affiliates Jian Rui Feng and Wen-men Gai, along with Chief Engineer of the Guangzhou Metro Group Co Ya-bin Yan, launched a case study modelling a subway within Guangzhou, China and potential evacuation plans and actions that could mitigate risk to personal against gas leaks via virtual computations. [ 11 ] This study found that the activation of air vents, the reduction number of initial people that needed to evacuate, and the increased ability for each person to identity the risk all reduced the risk that a gas leak would pose within the subway. [ 11 ]
Legislation passed in 2014 [ 12 ] requires gas suppliers to make greater efforts to control some of the 20,000 documented leaks in the US state of Massachusetts . The new law requires grade 1 and 2 leaks to be repaired if the street above a gas pipe is dug up, and requires priority be given to leaks near schools. It provides a mechanism for increased revenue from ratepayers (up to 1.5% without further approval) to cover the cost of repairs and replacement of leak-prone materials (like cast iron and non-cathodically protected steel) on an accelerated basis. The law sets a target of 20 years for replacement of pipes made from leak-prone materials if feasible given the revenue cap; as of 2015 [update] , Columbia Gas of Massachusetts (formerly named " Bay State Gas "), Berkshire Gas, Liberty Utilities , National Grid , and Unitil say they will meet this target, but NSTAR says it will take 25 years to complete. [ 13 ] [ 14 ] Leaks, statistics on leak-prone materials, and financial statements are reported annually to the Department of Public Utilities, which also has responsibility for rate-setting.
Additional proposals not included in the law would have required grade 3 leaks to be repaired during road construction, and priority for leaks which are killing trees or which were near hospitals or churches. [ 15 ] [ 16 ]
An attorney for the Conservation Law Foundation stated that the leaks were worth $38.8 million in lost natural gas, which also contributes 4% of the state's greenhouse gas emissions . [ 16 ] A federal study prompted by US Senator Edward J. Markey concluded that Massachusetts consumers paid approximately $1.5 billion from 2000–2011 for gas which leaked and benefited no one. [ 15 ] Markey has also backed legislation that would implement similar requirements at the national level, along with financing provisions for repairs. [ 15 ] [ needs update ]
Catastrophic gas leaks, such as the Bhopal disaster are well-recognized as problems, but the more-subtle effects of chronic low-level leaks have been slower to gain recognition.
In work with dangerous gases (such as in a lab or industrial setting), a gas leak may require hazmat emergency response, especially if the leaked material is flammable, explosive, corrosive, or toxic. For instance, the transportation of natural gasses can be susceptible to gas leaks them with themselves have explosive properties, such as the Latvian natural gas system and its report on the classification and potential risks of gas leakage as well as actionable responses. [ 17 ] There is also the safety of the public to consider, such as analyzing technics to help ensure the safety and ease of evacuation plans. | https://en.wikipedia.org/wiki/Gas_leak |
Gas lighting is the production of artificial light from combustion of a fuel gas such as methane , propane , butane , acetylene , ethylene , hydrogen , carbon monoxide , coal gas (town gas) or natural gas . The light is produced either directly by the flame, generally by using special mixes (typically propane or butane) of illuminating gas to increase brightness, or indirectly with other components such as the gas mantle or the limelight , with the gas primarily functioning to heat the mantle or the lime to incandescence . [ 1 ]
Before electricity became sufficiently widespread and economical to allow for general public use, gas lighting was prevalent for outdoor and indoor use in cities and suburbs where the infrastructure for distribution of gas was practical. [ 1 ] At that time, the most common fuels for gas lighting were wood gas , coal gas and, in limited cases, water gas . [ 2 ] Early gas lights were ignited manually by lamplighters , although many later designs are self-igniting. [ 3 ]
Gas lighting now is frequently used for camping , for which the high energy density of the hydrocarbon fuel , and the modular canisters on which camping lights are built, brings bright and long lasting light without complex equipment. [ 1 ] In addition, some urban historical districts retain gas street lighting , and gas lighting is used indoors or outdoors to create or preserve a nostalgic effect . [ 4 ]
Prior to use of gaseous fuels for lighting, the early lighting fuels consisted of olive oil , beeswax , fish oil , whale oil , sesame oil , nut oil, or other similar substances, which were all liquid fuels. These were the most commonly used fuels until the late 18th century. Whale oil was especially widely used for lighting in European cities such as London through the early 19th century. [ 2 ]
Chinese records dating back 1,700 years indicate the use of natural gas in homes for lighting and heating. The natural gas was transported by means of bamboo pipes to homes. [ 5 ] [ additional citation(s) needed ] The ancient Chinese of the Spring and Autumn period made the first practical use of natural gas for lighting purposes around 500 B.C. in which they used bamboo pipelines to transport both brine and natural gas for many miles, such as the ones in Zigong salt mines. [ citation needed ]
Public illumination preceded by centuries the development and widespread adoption of gas lighting. In 1417, Sir Henry Barton , Lord Mayor of London , ordained "Lanthornes with lights to bee hanged out on the Winter evening betwixt Hallowtide and Candlemassee ." [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] Paris was first illuminated by an order issued in 1524, and, in the beginning of the 16th century, the inhabitants were ordered to keep lights burning in the windows of all houses that faced streets. [ 11 ] In 1668, when some regulations were made for improving the streets of London, the residents were reminded to hang out their lanterns at the usual time, and, in 1690, an order was issued to hang out a light, or lamp, every night at nightfall, from Michaelmas to Christmas. By an Act of the Common Council in 1716, all housekeepers, whose houses faced any street, lane, or passage, were required to hang out, every dark night, one or more lights, to burn from six to eleven o'clock, under the penalty of one shilling as a fine for failing to do so. [ 12 ]
Accumulating and escaping gases were known originally among coal miners for their adverse effects rather than their useful characteristics. Coal miners described two types of gases, one called the choke damp and the other fire damp . In 1667, a paper detailing the effects of these gases was entitled, "A Description of a Well and Earth in Lancashire taking Fire, by a Candle approaching to it. Imparted by Thomas Shirley, Esq an eye-witness." [ 13 ]
British clergyman and scientist Stephen Hales experimented with the actual distillation of coal, thereby obtaining a flammable liquid. He reported his results in the first volume of his Vegetable Statics , published in 1726. From the distillation of "one hundred and fifty-eight grains [10.2 g] of Newcastle coal, he stated that he obtained 180 cubic inches [2.9 L] of gas, which weighed 51 grains [3.3 g], being nearly one third of the whole." [ 14 ] Hales's results garnered attention decades later as the unique chemical properties of various gases became understood through the work of Joseph Black , Henry Cavendish , Alessandro Volta , and others. [ 15 ]
A 1733 publication by Sir James Lowther in the Philosophical Transactions of the Royal Society detailed some properties of coal gas, including its flammability. Lowther demonstrated the principal properties of coal gas to different members of the Royal Society . He showed that the gas retained its flammability after storage for some time. The demonstration did not result in identification of utility. [ 16 ]
Minister and experimentalist John Clayton referred to coal gas as the "spirit" of coal. He discovered its flammability by an accident. The "spirit" he isolated from coal caught fire by coming in contact with a candle as it escaped from a fracture in one of his distillation vessels. He stored the coal gas in bladders, and at times he entertained his friends by demonstrating the flammability of the gas. Clayton published his findings in Philosophical Transactions . [ 17 ]
It took nearly 200 years for gas to become accessible for commercial use. [ clarification needed ] A Flemish alchemist, Jan Baptista van Helmont , was the first person to formally recognize gas as a state of matter. He would go on to identify several types of gases, including carbon dioxide. Over one hundred years later in 1733, Sir James Lowther had some of his miners working on a water pit for his mine. While digging the pit they hit a pocket of gas. Lowther took a sample of the gas and took it home to do some experiments. He noted, "The said air being put into a bladder … and tied close, may be carried away, and kept some days, and being afterwards pressed gently through a small pipe into the flame of a candle, will take fire, and burn at the end of the pipe as long as the bladder is gently pressed to feed the flame, and when taken from the candle after it is so lighted, it will continue burning till there is no more air left in the bladder to supply the flame." [ 18 ] Lowther had basically discovered the principle behind gas lighting.
Later in the 18th century William Murdoch (sometimes spelled "Murdock") stated: "the gas obtained by distillation from coal, peat, wood and other inflammable substances burnt with great brilliancy upon being set fire to … by conducting it through tubes, it might be employed as an economical substitute for lamps and candles." [ 19 ] Murdoch's first invention was a lantern with a gas-filled bladder attached to a jet. He would use this to walk home at night. After seeing how well this worked he decided to light his home with gas. In 1797, Murdoch installed gas lighting in his new home as well as the workshop in which he worked. “This work was of a large scale, and he next experimented to find better ways of producing, purifying, and burning the gas.” [ 20 ] The foundation had been laid for companies to start producing gas and other inventors to start playing with ways of using the new technology.
Murdoch was the first to exploit the flammability of gas for the practical application of lighting. He worked for Matthew Boulton and James Watt at their Soho Foundry steam engine works in Birmingham , England. In the early 1790s, while overseeing the use of his company's steam engines in tin mining in Cornwall, Murdoch began experimenting with various types of gas, finally settling on coal gas as the most effective. He first lit his own house in Redruth , Cornwall in 1792. [ 21 ] In 1798, he used gas to light the main building of the Soho Foundry and in 1802 lit the outside in a public display of gas lighting, the lights astonishing the local population. One of the employees at the Soho Foundry, Samuel Clegg , saw the potential of this new form of lighting. Clegg left his job to set up his own gas lighting business, the Gas Light and Coke Company .
A "thermolampe" using gas distilled from wood was patented in 1799, while German inventor Friedrich Winzer ( Frederick Albert Winsor ) was the first person to patent coal-gas lighting in 1804.
In 1801, Phillipe Lebon of Paris had also used gas lights to illuminate his house and gardens, and was considering how to light all of Paris. In 1820, Paris adopted gas street lighting.
In 1804, Dr Henry delivered a course of lectures on chemistry , at Manchester , in which he showed the mode of producing gas from coal, and the facility and advantage of its use. Dr Henry analysed the composition and investigated the properties of carburetted hydrogen gas (i.e. methane). His experiments were numerous and accurate and made upon a variety of substances; having obtained the gas from wood, peat , different kinds of coal, oil, wax, etc., he quantified the intensity of the light from each source.
In 1806 The Philips and Lee factory and a portion of Chapel Street in Salford, Lancashire were lit by gas, thought to be the first use of gas street lighting in the world.
Josiah Pemberton , an inventor, had for some time been experimenting on the nature of gas. A resident of Birmingham, his attention may have been roused by the exhibition at Soho. About 1806, he exhibited gas lights in a variety of forms and with great brilliance at the front of his factory in Birmingham. In 1808 he constructed an apparatus, applicable for several uses, for Benjamin Cooke , a manufacturer of brass tubes, gilt toys, and other articles.
In 1808, Murdoch presented to the Royal Society a paper entitled "Account of the Application of Gas from Coal to Economical Purposes" in which he described his successful application of coal gas to light the extensive establishment of Messrs. Phillips and Lea. For this paper he was awarded Count Rumford 's gold medal. [ 22 ] Murdoch's statements threw great light on the comparative advantage of gas and candles, and contained much useful information on the expenses of production and management.
Although the history is uncertain, David Melville has been credited [ 23 ] [ 24 ] [ 25 ] [ 26 ] with the first house and street lighting in the United States, in either 1805 or 1806 in Newport, Rhode Island .
In 1809, accordingly, the first application was made to Parliament to incorporate a company in order to accelerate the process, but the bill failed to pass. In 1810, however, the application was renewed by the same parties, and though some opposition was encountered and considerable expense incurred, the bill passed, but not without great alterations; and the London and Westminster Gas Light and Coke Company was established. Less than two years later, on 31 December 1813, Westminster Bridge was lit by gas. [ 27 ]
By 1816, Samuel Clegg obtained the patent for his horizontal rotative retort , his apparatus for purifying coal gas with cream of lime [ clarification needed ] , and for his rotative gas meter and self-acting governor . [ citation needed ]
Among the economic impacts of gas lighting was much longer work hours in factories. This was particularly important in Great Britain during the winter months when nights are significantly longer. Factories could even work continuously over 24 hours, resulting in increased production. Following successful commercialization, gas lighting spread to other countries.
In England, the first place outside London to have gas lighting was Preston, Lancashire , in 1816; this was due to the Preston Gaslight Company run by revolutionary Joseph Dunn , who found the most improved way [ clarification needed ] of brighter gas lighting. The parish church there was the first religious building to be lit by gas lighting. [ 28 ]
In Bristol , a Gas Light Company was founded on 15 December 1815. Under the supervision of the engineer, John Brelliat, extensive works were conducted in 1816-17 to build a gasholder, mains and street lights. Many of the principal streets in the centre of the city, as well as nearby houses, had switched to gas lighting by the end of 1817. [ 29 ]
In America, Seth Bemis lit his factory with gas illumination from 1812 to 1813. The use of gas lights in Rembrandt Peale 's Museum in Baltimore in 1816 was a great success. Baltimore was the first American city with gas street lights; Peale's Gas Light Company of Baltimore on 7 February 1817 lit its first street lamp at Market and Lemon Streets (currently Baltimore and Holliday Streets). The first private residence in the US illuminated by gas has been variously identified as that of David Melville (c. 1806), as described above, or of William Henry, a coppersmith , at 200 Lombard Street, Philadelphia , Pennsylvania, in 1816.
In 1817, at the three stations of the Chartered Gas Company in London, 25 chaldrons (24 m 3 ) of coal were carbonized daily, producing 300,000 cubic feet (8,500 m 3 ) of gas. This supplied gas lamps equal to 75,000 Argand lamps each yielding the light of six candles. At the City Gas Works, in Dorset Street, Blackfriars , three chaldrons of coal were carbonized each day, providing the gas equivalent of 9,000 Argand lamps. So 28 chaldrons of coal were carbonized daily, and 84,000 lights supplied by those two companies only.
At this period the principal difficulty in gas manufacture was purification. Mr. D. Wilson, of Dublin, patented a method for purifying coal gas by means of the chemical action of ammoniacal gas. [ clarification needed ] Another plan was devised by Reuben Phillips, of Exeter , who patented the purification of coal gas by the use of dry lime . G. Holworthy, in 1818, patented a method of purifying it by passing the gas, in a highly condensed state, through iron retorts heated to a dark red.
In 1820, Swedish inventor Johan Patrik Ljungström had developed a gas lighting with copper apparatuses and chandeliers of ink , brass and crystal , reportedly one of the first such public installations of gas lighting in the region, enhanced as a triumphal arch for the city gate for a royal visit of Charles XIV John of Sweden in 1820. [ 30 ]
By 1823, numerous towns and cities throughout Britain were lit by gas. Gas light cost up to 75% less than oil lamps or candles, which helped to accelerate its development and deployment. By 1859, gas lighting was to be found all over Britain and about a thousand gas works had sprung up to meet the demand for the new fuel. The brighter lighting which gas provided allowed people to read more easily and for longer. This helped to stimulate literacy and learning, speeding up the second Industrial Revolution .
In 1824 the English Association for Gas Lighting on the Continent , a sizeable business producing gas for several cities in mainland, Europe, including Berlin, was established, with Sir William Congreve, 2nd Baronet as general manager. [ 31 ]
The 1839 invention, the Bude-Light , provided a brighter and more economical lamp. [ 32 ]
Oil-gas appeared in the field as a rival of coal gas. In 1815, John Taylor patented an apparatus for the decomposition of "oil" and other animal substances. Public attention was attracted to "oil-gas" by the display of the patent apparatus at Apothecary's Hall , by Taylor & Martineau .
In 1891 the gas mantle was invented by the Austrian chemist Carl Auer von Welsbach . This eliminated the need for special illuminating gas (a synthetic mixture of hydrogen and hydrocarbon gases produced by destructive distillation of bituminous coal or peat ) to get bright shining flames. Acetylene was also used from about 1898 for gas lighting on a smaller scale. [ 33 ]
Illuminating gas was used for gas lighting, as it produces a much brighter light than natural gas or water gas . Illuminating gas was much less toxic than other forms of coal gas, but less could be produced from a given quantity of coal. The experiments with distilling coal were described by John Clayton in 1684. George Dixon's pilot plant exploded in 1760, setting back the production of illuminating gas a few years. The first commercial application was in a Manchester cotton mill in 1806. In 1901, studies of the defoliant effect of leaking gas pipes led to the discovery that ethylene is a plant hormone .
Throughout the 19th century and into the first decades of the 20th, the gas was manufactured by the gasification of coal. Later in the 19th century, natural gas began to replace coal gas, first in the US, and then in other parts of the world. In the United Kingdom, coal gas was used until the early 1970s.
The history of the Russian gas industry began with retired Lieutenant Pyotr Sobolevsky (1782–1841), who improved Philippe le Bon 's design for a "thermolamp" and presented it to Emperor Alexander I in 1811; in January 1812, Sobolevsky was instructed to draw up a plan for gas street-lighting for St. Petersburg. The French invasion of Russia delayed implementation, but St. Petersburg's Governor General Mikhail Miloradovich , who had seen the gas lighting of Vienna, Paris and other European cities, initiated experimental work on gas lighting for the capital, using British apparatus for obtaining gas from pit coal, and by the autumn of 1819, Russia's first gas street light was lit on one of the streets on Aptekarsky Island . [ 34 ]
In February 1835, the Company for Gas Lighting St. Petersburg was founded; towards the end of that year, a factory for the production of lighting gas was constructed near the Obvodny Canal , using pit coal brought in by ship from Cardiff ; and 204 gas lamps were ceremonially lit in St. Petersburg on 27 September 1839.
Over the next 10 years, their numbers almost quadrupled, to reach 800. By the middle of the 19th century, the central streets and buildings of the capital were illuminated: the Palace Square , Bolshaya and Malaya Morskaya streets, Nevsky and Tsarskoselsky Avenues, Passage Arcade, Noblemen's Assembly, the Technical Institute and Peter and Paul Fortress . [ 34 ]
It took many years of development and testing before gas lighting for the stage was commercially available. Gas technology was then installed in just about every major theatre in the world. But gas lighting was short-lived because the electric light bulb soon followed.
In the 19th century, gas stage lighting went from a crude experiment to the most popular way of lighting theatrical stages. In 1804, Frederick Albert Winsor first demonstrated the way to use gas to light the stage in London at the Lyceum Theatre . Although the demonstration and all the lead research were being done in London, "in 1816 at the Chestnut Street Theatre in Philadelphia was the earliest gas lit theatre in world". [ 35 ] In 1817 the Lyceum, Drury Lane , and Covent Garden theatres were all lit by gas. Gas was brought into the building by "miles of rubber tubing from outlets in the floor called 'water joints'" which "carried the gas to border-lights and wing lights". But before it was distributed, the gas came through a central distribution point called a "gas table", [ 36 ] which varied the brightness by regulating the gas supply, and the gas table, which allowed control of separate parts of the stage. Thus it became the first stage 'switchboard'. [ 37 ]
By the 1850s, gas lighting in theatres had spread practically all over the United States and Europe. Some of the largest installations of gas lighting were in large auditoriums, like the Théâtre du Chatelet , built in 1862. [ 38 ] In 1875, the new Paris Opera was constructed. "Its lighting system contained more than twenty-eight miles [45 km] of gas piping, and its gas table had no fewer than eighty-eight stopcocks, which controlled nine hundred and sixty gas jets." [ 38 ] The theatre that used the most gas lighting was Astley's Equestrian Amphitheatre in London. According to the Illustrated London News , "Everywhere white and gold meets the eye, and about 200,000 gas jets add to the glittering effect of the auditorium … such a blaze of light and splendour has scarcely ever been witnessed, even in dreams." [ 38 ]
Theatres switched to gas lighting because it was more economical than using candles and also required less labour to operate. With gas lighting, theatres would no longer need to have people tending to candles during a performance, or having to light each candle individually. "It was easier to light a row of gas jets than a greater quantity of candles high in the air." [ 37 ] Theatres also no longer needed to worry about wax dripping on the actors during a show.
Gas lighting also had an effect on the actors. As the stage was brighter, they could now use less make-up and their motions did not have to be as exaggerated. Half-lit stages had become fully lit stages. Production companies were so impressed with the new technology that one said, "This light is perfect for the stage. One can obtain gradation of brightness that is really magical." [ 37 ]
The best result was the improved respect from the audience. There was no more shouting or riots. The light pushed the actors more up stage behind the proscenium, helping the audience concentrate more on the action that was taking place on stage rather than what was going on in the house. Management had more authority on what went on during the show because they could see. [ 39 ] Gaslight was the leading cause of behaviour change in theatres. They were no longer places for mingling and orange selling, but places of respected entertainment.
There were six types of burners, but four burners were really experimented with: [ clarification needed ]
Several different instruments were used for stage lighting in the 19th century fell; these included footlights, border lights, groundrows, lengths, bunch lights, conical reflector floods, and limelight spots. These mechanisms sat directly on the stage, blinding the eyes of the audience.
Gas lighting did have some disadvantages. "Several hundred theatres are said to have burned down in America and Europe between 1800 and the introduction of electricity in the late 1800s. The increased heat was objectionable, and the border lights and wing lights had to be lighted by a long stick with a flaming wad of cotton at the end. For many years, an attendant or gas boy moved along the long row of jets, lighting them individually while gas was escaping from the whole row. Both actors and audiences complained of the escaping gas, and explosions sometimes resulted from its accumulation." [ 36 ]
These problems with gas lighting led to the rapid adoption of electric lighting. By 1881, the Savoy Theatre in London was using incandescent lighting. [ 42 ] While electric lighting was introduced to theatre stages, the gas mantle was developed in 1885 for gas-lit theatres. "This was a beehive-shaped mesh of knitted thread impregnated with lime that, in miniature, converted the naked gas flame into in effect, a lime-light ." [ 43 ] Electric lighting slowly took over in theatres. In the 20th century, it enabled better and safer theatre productions, with no smell, relatively very little heat, and more freedom for designers.
In the early 20th century, most cities in North America and Europe had gaslit streets, and most railway station platforms had gas lights too. However, around 1880 gas lighting for streets and train stations began giving way to high voltage (3,000–6,000 volt) direct current and alternating current arc lighting systems. This time period also saw the development of the first electric power utility designed for indoor use. The new system by inventor Thomas Edison was designed to function similar to gas lighting. For reasons of safety and simplicity it used direct current (DC) at a relatively low 110 volts to light incandescent light bulbs . Voltage in wires steadily declines as distance increases, and at this low voltage power plants needed to be within about 1 mile (1.6 km) of the lamps. This voltage drop problem made DC distribution relatively expensive and gas lighting retained widespread usage [ 44 ] with new buildings sometimes constructed with dual systems of gas piping and electrical wiring connected to each room, to diversify the power sources for lighting.
The development of new alternating current power transmission systems in the 1880s and 90s by companies such as Ganz and AEG in Europe and Westinghouse Electric and Thomson-Houston in the US solved the voltage and distance problem by using high transmission line voltages, and transformers to drop the voltage for distribution for indoor lighting. Alternating current technology overcame many of the limitations of direct current, enabling the rapid growth of reliable, low-cost electrical power networks which finally spelled the end of widespread usage of gas lighting. [ 44 ]
In some cities, gas lighting is preserved or restored as a vintage nostalgic feature to support the historic atmosphere of their historic centres.
In the 20th century, most cities with gas streetlights replaced them with new electric streetlights. For example, Baltimore, the first US city to install gas streetlights, removed nearly all of them. [ 45 ] A sole, token gas lamp is located at N. Holliday Street and E. Baltimore Street as a monument to the first gas lamp in America, erected at that location.
However, gas lighting of streets has not disappeared completely from some cities, and the few municipalities that retained gas lighting now find that it provides a pleasing nostalgic effect. Gas lighting is also seeing a resurgence in the luxury home market for those in search of historical authenticity.
The largest gas lighting network in the world is that of Berlin . With about 23,000 lamps (2022), [ 46 ] it holds more than half of all working gas street lamps in the world, followed by Düsseldorf with 14,000 lamps (2020), of which at least 10,000 are to be retained. [ 47 ]
In London there were about 1,500 working gas street lamps as of 2018, [update] although there were plans to replace 299 of those in Westminster (the first city in the world lit by gas) with LED lighting by 2023, which sparked public opposition. [ 48 ] [ 49 ] [ 50 ] [ 51 ]
In the United States, more than 2800 gas lights in Boston operate in the historic districts of Beacon Hill , Back Bay , Bay Village , Charlestown , and parts of other neighbourhoods. In Cincinnati , Ohio, more than 1100 gas lights operate in areas that have been named historic districts. Gas lights also operate in parts of the famed French Quarter and outside historic homes throughout the city in New Orleans . [ citation needed ]
Zagreb , the capital of Croatia, has used gas candelabras since 1863. Initially, Zagreb was illuminated by 60,000 lamps, but as of 1987, [update] only 248 gas street lamps illuminate old parts of the city. [ 52 ] Zagreb gas lamps are manually managed by lamplighters. [ 52 ]
Prague , where gas lighting was introduced on 15 September 1847, [ 53 ] had about 10,000 gas streetlamps in the 1940s. The last historic gas candelabras become electrified in 1985. [ 54 ] However, in 2002–2014, streetlamps along the Royal Route and some other streets in the centre were rebuilt to use gas (using replicas of the historic poles and lanterns), several historic candelabras ( Hradčanské náměstí , Loretánská street, Dražického náměstí etc.) were also converted back to gas lamps, and five new gas lamps were installed in the Michle Gasworks as a promotion. [ 55 ] In 2018, there were 417 points (about 650 lanterns) of street gas lighting in Prague. [ 56 ] [ 57 ] During Advent and Christmas, lanterns on the Charles Bridge are managed manually by a lamplighter in historic uniform. [ 58 ] The plan to reintroduce gas lights in Old Prague was proposed in 2002, and adopted by the Municipality of Prague in January 2004. [ 59 ]
The use of natural gas (methane) for indoor lighting is nearly extinct. Besides producing a lot of heat, the combustion of methane tends to release significant amounts of carbon monoxide , a colourless and odourless gas that is more readily absorbed by the blood than oxygen , and can be deadly. Historically, the use of lamps of all types was of shorter duration than we are accustomed to with electric lights, and in the far more draughty buildings, it was of less concern and danger. There are suppliers of new mantle gas lamps set up for use with natural gas; and, some old homes still have fixtures installed, and some period restorations have salvaged fixtures installed, more for decoration than use.
New fixtures are still made and available for propane (sometimes called "bottle(d) gas"), a product of oil refining , which under most circumstances burns more completely to carbon dioxide and water vapour. In some locations where public utility electricity or kerosene are not readily accessible or desirable, propane gas mantle lamps are still used, although the increased availability of alternative energy sources, such as solar panels and small scale wind turbines , combined with increasing efficiency of lighting products, such as compact fluorescent lamps and LEDs are also in use.
Perforated tubes bent into the shape of letters were used to form gas lit advertising signs, prior to the introduction of neon lights , as early as 1857 in Grand Rapids, Michigan . [ 60 ] Gas lighting is still in common use for camping lights. Small portable gas lamps, connected to a portable gas cylinder, are a common item on camping trips. Mantle lamps powered by vaporized petrol, such as the Coleman lantern , are also available. | https://en.wikipedia.org/wiki/Gas_lighting |
A gas mask is a piece of personal protective equipment used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Most gas masks are also respirators , though the word gas mask is often used to refer to military equipment (such as a field protective mask), the scope used in this article. Gas masks only protect the user from ingesting or inhaling chemical agents, as well as preventing contact with the user's eyes (many chemical agents affect through eye contact). Most combined gas mask filters will last around 8 hours in a biological or chemical situation. Filters against specific chemical agents can last up to 20 hours. [ citation needed ]
Airborne toxic materials may be gaseous (for example, chlorine or mustard gas ), or particulates (such as biological agents ). Many filters provide protection from both types.
The first gas masks mostly used circular lenses made of glass , mica or cellulose acetate to allow vision. Glass and mica were quite brittle and needed frequent replacement. The later Triplex lens style (a cellulose acetate lens sandwiched between glass ones) [ 1 ] became more popular, and alongside plain cellulose acetate they became the standard into the 1930s. Panoramic lenses were not popular until the 1930s, but there are some examples of those being used even during the war [ clarification needed ] (Austro-Hungarian 15M). Later, stronger polycarbonate came into use.
Some masks have one or two compact air filter containers screwed onto inlets, while others have a large air filtration container connected to the gas mask via a hose that is sometimes confused with an air-supplied respirator in which an alternate supply of fresh air (oxygen tanks) is delivered.
According to Popular Mechanics , "The common sponge was used in ancient Greece as a gas mask..." [ 2 ] In 1785, Jean-François Pilâtre de Rozier invented a respirator .
Primitive respirator examples were used by miners and introduced by Alexander von Humboldt in 1799, when he worked as a mining engineer in Prussia . [ 3 ] The forerunner to the modern gas mask was invented in 1847 by Lewis P. Haslett , a device that contained elements that allowed breathing through a nose and mouthpiece, inhalation of air through a bulb-shaped filter, and a vent to exhale air back into the atmosphere. [ 4 ] First Facts states that a "gas mask resembling the modern type" was patented by Lewis Phectic Haslett of Louisville, Kentucky , who received a patent on June 12, 1849. [ 5 ] U.S. patent #6,529 [ 6 ] issued to Haslett, described the first "Inhaler or Lung Protector" that filtered dust from the air.
Early versions were constructed by the Scottish chemist John Stenhouse in 1854 [ 7 ] and the physicist John Tyndall in the 1870s. [ 8 ] Another early design was the "Safety Hood and Smoke Protector" invented by Garrett Morgan in 1912, and patented in 1914. It was a simple device consisting of a cotton hood with two hoses which hung down to the floor, allowing the wearer to breathe the safer air found there. In addition, moist sponges were inserted at the end of the hoses in order to better filter the air. [ 9 ] [ 10 ]
The First World War brought about the first need for mass-produced gas masks on both sides because of extensive use of chemical weapons . The German army successfully used poison gas for the first time against Allied troops at the Second Battle of Ypres , Belgium on April 22, 1915. [ 11 ] An immediate response was cotton wool wrapped in muslin, issued to the troops by May 1. This was followed by the Black Veil Respirator , invented by John Scott Haldane , which was a cotton pad soaked in an absorbent solution which was secured over the mouth using black cotton veiling. [ 12 ]
Seeking to improve on the Black Veil respirator, Cluny Macpherson created a mask made of chemical-absorbing fabric which fitted over the entire head: a 50.5 cm × 48 cm (19.9 in × 18.9 in) canvas hood treated with chlorine-absorbing chemicals, and fitted with a transparent mica eyepiece. [ 13 ] [ 14 ] Macpherson presented his idea to the British War Office Anti-Gas Department on May 10, 1915; prototypes were developed soon after. [ 15 ] The design was adopted by the British Army and introduced as the British Smoke Hood in June 1915; Macpherson was appointed to the War Office Committee for Protection against Poisonous Gases. [ 16 ] More elaborate sorbent compounds were added later to further iterations of his helmet ( PH helmet ), to defeat other respiratory poison gases used such as phosgene , diphosgene and chloropicrin . In summer and autumn 1915, Edward Harrison , Bertram Lambert and John Sadd developed the Large Box Respirator. [ 17 ] [ better source needed ] This canister gas mask had a tin can containing the absorbent materials by a hose and began to be issued in February 1916. A compact version, the Small Box Respirator , was made a universal issue from August 1916. [ citation needed ]
In the first gas masks of World War I, it was initially found that wood charcoal was a good absorbent of poison gases. Around 1918, it was found that charcoals made from the shells and seeds of various fruits and nuts such as coconuts , chestnuts , horse-chestnuts , and peach stones performed much better than wood charcoal . These waste materials were collected from the public in recycling programs to assist the war effort. [ 18 ]
The first effective filtering activated charcoal gas mask in the world was invented in 1915 by Russian chemist Nikolay Zelinsky . [ 19 ]
Also in World War I, since dogs were frequently used on the front lines, a special type of gas mask was developed that dogs were trained to wear. [ 20 ] Other gas masks were developed during World War I and the time following for horses in the various mounted units that operated near the front lines. [ 21 ] In America, thousands of gas masks were produced for American as well as Allied troops. Mine Safety Appliances was a chief producer. This mask was later used widely in industry. [ 22 ]
The British Respirator, Anti-Gas (Light) was developed in 1943 by the British. [ 23 ] It was made of plastic and rubber-like material that greatly reduced the weight and bulk compared to World War I gas masks, and fitted the user's face more snugly and comfortably. The main improvement was replacing the separate filter canister connected with a hose by an easily replaceable filter canister screwed on the side of the gas mask. Also, it had replaceable plastic lenses. [ citation needed ]
Gas mask development since has mirrored the development of chemical agents in warfare, filling the need to protect against ever more deadly threats, biological weapons, and radioactive dust in the nuclear era. However, for agents that cause harm through contact or penetration of the skin, such as blister agent or nerve agent , a gas mask alone is not sufficient protection, and full protective clothing must be worn in addition to protect from contact with the atmosphere. For reasons of civil defence and personal protection, individuals often buy gas masks since they believe that they protect against the harmful effects of an attack with nuclear, biological, or chemical ( NBC ) agents, which is only partially true, as gas masks protect only against respiratory absorption. Most military gas masks are designed to be capable of protecting against all NBC agents, but they can have filter canisters proof against those agents (heavier) or only against riot control agents and smoke (lighter and often used for training purposes). There are lightweight masks solely for protection against riot-control agents and not for NBC situations. [ citation needed ]
Although thorough training and the availability of gas masks and other protective equipment can nullify the casualty-causing effects of an attack by chemical agents, troops who are forced to operate in full protective gear are less efficient in completing tasks, tire easily, and may be affected psychologically by the threat of attack by those weapons. During the Cold War , it was seen as inevitable that there would be a constant NBC threat on the battlefield and so troops needed protection in which they could remain fully functional; thus, protective gear and especially gas masks have evolved to incorporate innovations in terms of increasing user comfort and compatibility with other equipment (from drinking devices to artificial respiration tubes, to communications systems etc.).
During the Iran–Iraq War (1980–88), Iraq developed its chemical weapons program with the help of European countries such as Germany and France [ 24 ] and used them in a large scale against Iranians and Iraqi Kurds. Iran was unprepared for chemical warfare. In 1984, Iran received gas masks from the Republic of Korea and East Germany , but the Korean masks were not suited for the faces of non- East Asian people , the filter lasted for only 15 minutes, and the 5,000 masks bought from East Germany proved to be not gas masks but spray-painting goggles. As late as 1986, Iranian diplomats still travelled in Europe to buy active charcoal and models of filters to produce defensive gear domestically. In April 1988, Iran started domestic production of gas masks by the Iran Yasa factories. [ 25 ]
Absorption is the process of being drawn into a (usually larger) body or substrate, and adsorption is the process of deposition upon a surface. This can be used to remove both particulate and gaseous hazards. Although some form of reaction may take place, it is not necessary; the method may work by attractive charges . For example, if the target particles are positively charged, a negatively charged substrate may be used. Examples of substrates include activated carbon , and zeolites . This effect can be very simple and highly effective, for example using a damp cloth to cover the mouth and nose while escaping a fire. While this method can be effective at trapping particulates produced by combustion, it does not filter out harmful gases which may be toxic or which displace the oxygen required for survival.
Gas masks have a useful lifespan limited by the absorbent capacity of the filter. Filters cease to provide protection when saturated with hazardous chemicals, and degrade over time even if sealed. Most gas masks have sealing caps over the air intake and are stored in vacuum-sealed bags to prevent the filter from degrading due to exposure to humidity and pollutants in normal air. Unused gas mask filters from World War II may not protect the wearer at all, and could be harmful if worn due to long-term changes in the chemical composition of the filter. [ citation needed ]
Some World War II and Soviet Cold War gas mask filters contained chrysotile asbestos or crocidolite asbestos . [ 26 ] [ 27 ] [ 28 ] not known to be harmful at the time. It is not reliably known for how long the materials were used in filters.
Typically, masks using 40 mm connections are a more recent design. Rubber degrades with time, so boxed unused "modern type" masks can be cracked and leak. The US C2 canister (black) contains hexavalent chromium ; studies by the U.S. Army Chemical Corps found that the level in the filter was acceptable, but suggest caution when using, as it is a carcinogen . [ 29 ]
The filter is selected according to the toxic compound. [ 30 ] Each filter type protects against a particular hazard and is color-coded:
Particle filters are often included, because in many cases the hazardous materials are in the form of mist, which can be captured by the particle filter before entering the chemical adsorber. In Europe and jurisdictions with similar rules such as Russia and Australia, filter types are given suffix numbers to indicate their capacity. For non-particle hazards, the level "1" is assumed and a number "2" is used to indicate a better level. For particles (P), three levels are always given with the number. [ 30 ] In the US, only the particle part is further classified by NIOSH air filtration ratings . [ 31 ]
A filter type that can protect against multiple hazards is notated with the European symbols concatenated with each other. Examples include ABEK, ABEK-P3, and ABEK-HgP3. [ 30 ] A2B2E2K2-P3 is the highest rating of filter available. [ when? ] An entirely different "multi/CBRN" filter class with an olive color is used in the US. [ 31 ]
Filtration may be aided with an air pump to improve wearer comfort. Filtration of air is only possible if there is sufficient oxygen in the first place. Thus, when handling asphyxiants , or when ventilation is poor or the hazards are unknown, filtration is not possible and air must be supplied (with a SCBA system) from a pressurized bottle as in scuba diving.
A modern mask typically is constructed of an elastic polymer in various sizes. It is fitted with various adjustable straps which may be tightened to secure a good fit. Crucially, it is connected to a filter cartridge near the mouth either directly, or via a flexible hose. Some models contain drinking tubes which may be connected to a water bottle. Corrective lens inserts are also available for users who require them.
Masks are typically tested for fit before use. After a mask is fitted, it is often tested by various challenge agents. Isoamyl acetate , a synthetic banana flavourant, and camphor are often used as innocuous challenge agents. In the military, teargases such as CN , CS , and stannic chloride in a chamber may be used to give the users confidence in the efficacy of the mask. [ 32 ]
The protection of a gas mask comes with some disadvantages. The wearer of a typical gas mask must exert extra effort to breathe, and some of the exhaled air is re-inhaled due to the dead space between the facepiece and the user's face. The exposure to carbon dioxide may exceed its OELs (0.5% by volume/9 grammes per cubic metre for an eight-hour shift; 1.4%/27 grammes per m 3 for 15 minutes' exposure) [ 33 ] by a factor of many times: for gas masks and elastomeric respirators , up to 2.6% [ 34 ] ); [ 35 ] and in case of long-term use, headache , [ 36 ] dermatitis and acne [ 37 ] may appear. The UK HSE textbook recommends limiting the use of respirators without air supply (that is, not PAPR ) to one hour. [ 38 ]
This principle relies on substances harmful to humans being usually more reactive than air. This method of separation will use some form of generally reactive substance (for example an acid ) coating or supported by some solid material. An example is synthetic resins . These can be created with different groups of atoms (usually called functional groups ) that have different properties. Thus a resin can be tailored to a particular toxic group. When the reactive substance comes in contact with the resin, it will bond to it, removing it from the air stream. It may also exchange with a less harmful substance at this site.
Though it was crude, the hypo helmet was a stopgap measure for British troops in the trenches that offered at least some protection during a gas attack. As the months passed and poison gas was used more often, more sophisticated gas masks were developed and introduced. There are two main difficulties with gas mask design: | https://en.wikipedia.org/wiki/Gas_mask |
A gas meter is a specialized flow meter , used to measure the volume of fuel gases such as natural gas and liquefied petroleum gas . Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility . Gases are more difficult to measure than liquids, because measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume, regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure, and heating value compensation must be made to measure actual amount and value of gas moving through a meter.
Several different designs of gas meters are in common use, depending on the volumetric flow rate of gas to be measured, the range of flows anticipated, the type of gas being measured, and other factors.
Gas meters that exist in colder climates in buildings built prior to the 1970s were typically located inside the home, typically in the basement or garage. Since then, the vast majority are now placed outside though there are a few exceptions especially in older cities.
These are the most common type of gas meter, seen in almost all residential and small commercial installations. Within the meter there are two or more chambers formed by movable diaphragms . With the gas flow directed by internal valves , the chambers alternately fill and expel gas, producing a nearly continuous flow through the meter. As the diaphragms expand and contract, levers connected to cranks convert the linear motion of the diaphragms into rotary motion of a crank shaft which serves as the primary flow element . This shaft can drive an odometer -like counter mechanism or it can produce electrical pulses for a flow computer .
Diaphragm gas meters are positive displacement meters .
Rotary meters are highly machined precision instruments capable of handling higher volumes and pressures than diaphragm meters. Within the meter, two figure "8" shaped lobes, the rotors (also known as impellers or pistons), spin in precise alignment. With each turn, they move a specific quantity of gas through the meter. The operating principle is similar to that of a Roots blower . The rotational movement of the crank shaft serves as a primary flow element and may produce electrical pulses for a flow computer or may drive an odometer-like counter .
Turbine gas meters infer gas volume by determining the speed of the gas moving through the meter. Because the volume of gas is inferred from the flow, it is important that flow conditions are good. A small internal turbine measures the speed of the gas, which is transmitted mechanically to a mechanical or electronic counter. These meters do not impede the flow of gas, but are limited at measuring lower flow rates.
An orifice gas meter consists of a straight length of pipe inside which a precisely known orifice plate creates a pressure drop, thereby affecting flow. Orifice meters are a type of differential meter, all of which infer the rate of gas flow by measuring the pressure difference across a deliberately designed and installed flow disturbance. The gas static pressure, density, viscosity, and temperature must be measured or known in addition to the differential pressure for the meter to accurately measure the fluid. Orifice meters often do not handle a large range of flow rates . They are however accepted and understood in industrial applications since they are easy to field-service and have no moving parts.
Ultrasonic flow meters are more complex than meters that are purely mechanical, as they require significant signal processing and computation capabilities. Ultrasonic meters measure the speed of gas movement by measuring the speed at which sound travels in the gaseous medium within the pipe. The American Gas Association [ 1 ] covers the proper usage and installation of these meters, and it specifies a standardised speed-of-sound calculation which predicts the speed of sound in a gas with a known pressure, temperature, and composition .
The most elaborate types of ultrasonic flow meters average speed of sound over multiple paths in the pipe. The length of each path is precisely measured in the factory. Each path consists of an ultrasonic transducer at one end and a sensor at the other. The meter creates a 'ping' with the transducer and measures the time elapsed before the sensor receives the sonic pulse. Some of these paths point upstream so that the sum of the times of flight of the sonic pulses can be divided by the sum of the flight lengths to provide an average speed of sound in the upstream direction. This speed differs from the speed of sound in the gas by the velocity at which the gas is moving in the pipe. The other paths may be identical or similar, except that the sound pulses travel downstream. The meter then compares the difference between the upstream and downstream speeds to calculate the velocity of gas flow.
Ultrasonic meters are high-cost and work best with no liquids present at all in the measured gas, so they are primarily used in high-flow, high-pressure applications such as utility pipeline meter stations, where the gas is always dry and lean, and where small proportional inaccuracies are intolerable due to the large amount of money at stake. The turndown ratio of an ultrasonic meter is probably the largest of any natural gas meter type, and the accuracy and range ability of a high-quality ultrasonic meter is actually greater than that of the turbine meters against which they are proven.
Inexpensive varieties of ultrasonic meters are available as clamp-on flow meters, which can be used to measure flow in any diameter of pipe without intrusive modification. Such devices are based on two types of technology: (1) time of flight or transit time; and (2) cross correlation. Both technologies involve transducers that are simply clamped on to the pipe and programmed with the pipe size and schedule and can be used to calculate flow. Such meters can be used to measure almost any dry gas including natural gas, nitrogen, compressed air, and steam. Clamp-on meters are available for measuring liquid flow as well.
A coriolis meter is usually one or more pipes with longitudinally or axially displaced section(s) that are excited to vibrate at resonant frequency. Coriolis meters are used with liquids and gases. When the fluid within the displaced section is at rest, both the upstream and downstream portion of the displaced section will vibrate in phase with each other. The frequency of this vibration is determined by the overall density of the pipe (including its contents). This allows the meter to measure the flowing density of the gas in real time. Once the fluid begins to flow, however, the Coriolis force comes into play. This effect implies a relationship between the phase difference in the vibration of the upstream and downstream sections and the mass flow rate of the fluid contained by the pipe.
Again, owing to the amount of inference, analog control and calculation intrinsic to a coriolis meter, the meter is not complete with just its physical components. There are actuation, sensing, electronic, and computational elements that must be present for the meter to function.
Coriolis meters can handle a wide range of flow rates and have the unique ability to output mass flow - this gives the highest accuracy of flow measurement currently available for mass flow measurement. Since they measure flowing density, coriolis meters can also infer gas flow rate at flowing conditions.
American Gas Association Report No. 11 provides guidelines for obtaining good results when measuring natural gas with a coriolis meter.
Thermal mass flow meter are a pivotal innovation in gas metering technology, leveraging heat transfer principles to accurately measure gas flow rates. These sensors operate by introducing a small amount of heat into the gas stream and measuring the temperature change downstream. The rate of heat dissipation correlates directly to the mass flow rate of the gas, providing precise measurements even at low flow rates. [ 2 ]
Thermal flow sensors are particularly advantageous for gas meters due to their:
Minimal Maintenance: No moving parts reduce wear and tear, leading to long-term reliability.
These sensors are commonly paired with temperature and pressure compensation systems to account for variations in gas properties, ensuring accurate measurement across varying environmental conditions. Thermal sensors are also integral to advanced smart meters, enabling real-time data transmission and analytics for utilities and end-users.
Recent innovations in thermal sensor technology include microelectromechanical systems ( MEMS )-based sensors, which offer further miniaturization, enhanced sensitivity, and lower power consumption, making them ideal for IoT-enabled gas metering systems.
The volume of gas flow provided by a gas meter is just that, a reading of volume. Gas volume does not take into account the quality of the gas or the amount of heat available when burned. Utility customers are billed according to the heat available in the gas. The quality of the gas is measured and adjusted for in each billing cycle. This is known by several names as the calorific value , heating value, or therm value.
The calorific value of natural gas can be obtained using a process gas chromatograph , which measures the amount of each constituent of the gas, namely:
Additionally, to convert from volume to thermal energy, the pressure and temperature of the gas must be taken into consideration. Pressure is generally not a problem; the meter is simply installed immediately downstream of a pressure regulator and is calibrated to read accurately at that pressure. Pressure compensation then occurs in the utility's billing system. Varying temperature cannot be handled as easily, but some meters are designed with built-in temperature compensation to keep them reasonably accurate over their designed temperature range. Others are corrected for temperature electronically.
Any type of gas meter can be obtained with a wide variety of indicators. The most common are indicators that use multiple clock hands (pointer style) or digital readouts similar to an odometer , but remote readouts of various types are also becoming popular — see Automatic meter reading and Smart meter .
Gas meters are required to register the volume of gas consumed within an acceptable degree of accuracy. Any significant error in the registered volume can represent a loss to the gas supplier, or the consumer being overbilled. The accuracy is generally laid down in statute for the location in which the meter is installed. Statutory provisions should also specify a procedure to be followed should the accuracy be disputed.
In the UK, the permitted error for a gas meter manufactured prior to the European Measuring Instruments Directive [ 3 ] is ±2%. [ 4 ] However, the European Measuring Instrument Directive has harmonised gas meter errors across Europe and consequently meters manufactured since the directive came into force must read within ±3%. Meters whose accuracy is disputed by the customer have to be removed for testing by an approved meter examiner. [ 5 ] If the meter is found to be reading outside of the prescribed limits, the supplier has to refund the consumer for gas incorrectly measured while that consumer had that meter (but not vice versa). Any refund is limited to the previous six years. [ 6 ] If the meter cannot be tested or its reading is unreliable, the consumer and supplier have to negotiate a settlement. If the meter is found to be reading within limits, the consumer has to pay the costs of testing (and pay any outstanding charges). This contrasts with the position on electric meters, where the test is free and a refund is only given if the date that the meter started to read inaccurately can be determined.
Smart metering technologies for gas meters refer to advanced systems that enable real-time monitoring, data collection, and analysis of water usage through digital and connected devices. Unlike traditional mechanical gas meters, smart meters are equipped with electronic components that measure water flow and transmit the data wirelessly to utilities and consumers. Smart water meters are integrated with Internet of Things (IoT) platforms, allowing for more efficient gas management and improved customer engagement.
Radio Frequency (RF) technologies form the backbone of smart metering systems by enabling wireless communication between meters and utility networks. Several RF technologies and protocols are widely used in smart gas meter:
Application-layer protocols operating above RF communication technologies to standardize data exchange, ensure interoperability, and enhance device functionality. These protocols enable seamless integration of meters into broader utility and Internet of Things (IoT) ecosystems.
DLMS/COSEM (Device Language Message Specification/Companion Specification for Energy Metering) is one of the most widely adopted protocols in smart metering. It provides a flexible and standardized framework for data exchange between metering devices and utility systems. The protocol supports various communication technologies, including RF, wired, and cellular networks, and facilitates secure data transfer, structured data management, and remote monitoring.
Other application-layer protocols, such as MQTT (Message Queuing Telemetry Transport) and CoAP (Constrained Application Protocol), are also utilized in smart metering systems, particularly in IoT-centric deployments. These protocols focus on low-bandwidth, high-efficiency communication, ensuring reliable data exchange in diverse environments. [ 7 ] [ 8 ]
The adoption of these RF technologies and protocols enables seamless integration of smart water meters into utility systems, offering several advantages:
Turbine, rotary, and diaphragm meters can be compensated using a calculation specified in American Gas Association Report No. 7. This standardised calculation compensates the quantity of volume as measured to quantity of volume at a set of base conditions . The AGA 7 calculation itself is a simple ratio and is, in essence, a density correction approach to translating the volume or rate of gas at flowing conditions to a volume or rate at base conditions .
Orifice meters are a very commonly used type of meter, and because of their widespread use, the characteristics of gas flow through an orifice meter have been closely studied. American Gas Association Report No. 3 deals with a broad range of issues relating to orifice metering of natural gas, and it specifies an algorithm for calculating natural gas flow rates based on the differential pressure, static pressure, and temperature of a gas with a known composition.
These calculations depend in part on the ideal gas law and also require a gas compressibility calculation in order to account for the fact that real gases are not ideal. A very commonly used compressibility calculation is American Gas Association Report No. 8, detail characterization.
Residential, commercial and industrial gas meters have their own standard thread sizes. The gas meter is connected to customer piping through a swivel and nut, which has a dedicated set of thread sizes. [ 9 ] Threads are helical structures used on screws, bolts, pipes, and other fasteners to facilitate the joining of components. Their design and standardization vary depending on their intended application, material, and region.
Standardized Thread Systems
Several organizations and systems have established standards for threads to ensure interchangeability and reliability:
Thread standards can vary between regions and industries, often requiring adaptors or conversion charts for compatibility. For example:
The top ten depends on the ranking methods, [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/Gas_meter |
A gas meter prover is a device to verify the accuracy of a gas meter . Provers are typically used in gas meter repair facilities, municipal gas meter shops, and public works shops. Provers work by passing a known volume of air through a meter, while monitoring the gas meter's register, index, or internal displacement. The prover determines the meter factor , which is the volume of air passed divided by the volume of air measured. [ 1 ]
Since the early 1900s, bell provers have been the most common reference standard used in gas meter proving, and has provided standards for the gas industry that is unfortunately susceptible to a myriad of immeasurable uncertainties.
A bell prover (commonly referred to in the industry as a "bell") consists of a vertical inner tank surrounded by an outer shell. A space between the inner tank and outer shell is filled with a sealing liquid, usually oil. An inverted tank, called the bell, is placed over the inner tank. The liquid provides an air-tight seal. Bell provers are typically counterweighted to provide positive pressure through a hose and valve connected to a meter. Sometimes rollers or guides are installed on the moving part of the bell which allows for smooth linear movement without the potential for immeasurable pressure differentials caused by the bell rocking back or forth. [ citation needed ]
Bells provide a volume of air that may be predetermined by calculated temperature, pressure and the effective diameter of the bell. Bell scales are unique to each bell and are usually attached vertically with a needle-like pointer. When proving a meter using a manually controlled bell, an operator must first fill the bell with a controlled air supply or raise it manually by opening a valve and pulling a chained mechanism, seal the bell and meter and check the sealed system for leaks, determine the flow rate needed for the meter, install a special flow-rate cap on the meter outlet, note the starting points of both the bell scale and meter index, release the bell valve to pass air through the meter, observe the meter index and calculate the time it takes to pass the predetermined amount of air, then manually calculate the meter's proof accounting for bell air and meter temperature and in some cases other environmental factors.
Uncertainties commonly experienced, and possibly unaccounted for within a test when using bell provers can lead to incorrect proofs, by which an operator may adjust a gas meter incorrectly. Temperature inconsistencies between the bell air, meter and connecting hoses can account for most meter proof inaccuracies. Other factors may be mechanical such as stuck or sticky bell rollers or guides, loose piping connections or valves, a dent in the test area of the bell, incorrect counterweights, and human errors in the operation or calculations.
The invention of programmable logic controllers (PLC) allowed gas meter repair facilities to automate most of the manual bell prover's process and calculations. Instead of manually raising and lowering the bell prover, solenoid valves connected to a PLC control air flows through the meter. Temperature, pressure , and humidity sensors can be used to feed data into an automated bell PLC, and calculations for meter proofs can be handled by a computer or electronic device programmed for such a purpose. In the early 1990s, the PLC was replaced by PACs (Programmable Automated Controls) and modern computer systems. Sensors to read the index of a meter were added to further automate the process, removing much of the human error associated with manual bell provers.
The natural evolution of the automated bell and PAC controls led itself to the use of vacuum driven provers with arrays of sonic nozzles (utilizing choked flow to provide precise flow rates. Such a use eliminated the need for a bell, as the flow rate is provided through the nozzles. When sufficient vacuum is applied to a sonic nozzle it creates a constant flow rate. Bernoulli's principle is applied to calculate the chosen flow rates chosen by the user or automated by a computer . Computers and PAC systems automate the process, and most sonic nozzle provers are capable of displaying not only meter proofs to a user, but are also capable of transmitting proofs as well as other important data to database systems across a computer network. | https://en.wikipedia.org/wiki/Gas_meter_prover |
Gas networks simulation or gas pipeline simulation is a process of defining the mathematical model of gas transmission and gas distribution systems, which are usually composed of highly integrated pipe networks operating over a wide range of pressures. Simulation allows to predict the behaviour of gas network systems under different conditions. Such predictions can be effectively used to guide decisions regarding the design and operation of the real system.
Depending on the gas flow characteristics in the system there are two states that can be matter of simulation:
In the gas networks simulation and analysis, matrices turned out to be the natural way of expressing the problem. Any network can be described by set of matrices based on the network topology . Consider the gas network by the graph below. The network consists of one source node (reference node) L1, four load nodes (2, 3, 4 and 5) and seven pipes or branches. For network analysis it is necessary to select at least one reference node . Mathematically, the reference node is referred to as the independent node and all nodal and branch quantities are dependent on it. The pressure at source node is usually known, and this node is often used as the reference node . However, any node in the network may have its pressure defined and can be used as the reference node . A network may contain several sources or other pressure-defined nodes and these form a set of reference nodes for the network. The load nodes are points in the network where load values are known. These loads may be positive, negative or zero. A negative load represents a demand for gas from the network. This may consist in supplying domestic or commercial consumers, filling gas storage holders, or even accounting for leakage in the network. A positive load represents a supply of gas to the network. This may consist in taking gas from storage, source or from another network. A zero load is placed on nodes that do not have a load but are used to represent a point of change in the network topology , such as the junction of several branches. For steady state conditions, the total load on the network is balanced by the inflow into the network at the source node . The interconnection of a network can produce a closed path of branches, known as a loop . In figure, loop A consists of branches p12-p24-p14, loop B consists of p13-p34-p14, and loop C consists of p24-p25-p35-p34. A fourth loop may be defined as p12-p24-p34-p13, but it is redundant if loops A, B and C are also defined. Loops A, B and C are independent ones but the fourth one is not, as it can be derived from A, B and C by eliminating common branches . To define the network topology completely it is necessary to assign a direction to each branch. Each branch direction is assigned arbitrarily and is assumed to be positive direction of flow in the branch. If the flow has the negative value, then the direction of flow is opposite to branch direction. In the similar way, direction is assigned to each loop and flow in the loop. The solutions of problems involving gas network computation of any topology requires such a representation of the network to be found which enables the calculations to be performed in the most simple way. These requirements are met by the graph theory which permits representation of the network structure by means of the incidence properties of the network components and, in consequence, makes such a representation explicit.
The calculation of the pressure drop along the individual pipes of a gas network requires use of the flow equations . Many gas flow equations have been developed and a number have been used by the gas industry. Most are based on
the result of gas flow experiments. The result of the particular formula normally varies because these
experiments were conducted over different range of flow conditions, and on varying internal surface
roughness. Instead, each formula is applicable to a limited range of flow and pipe surface conditions.
A gas network is in the steady state when the values of gas flow characteristics are independent of time and system described by the set of nonlinear equations . The goal of simple simulation of a gas network is usually that of computing the values of nodes' pressures, loads and the values of flows in the individual pipes. The pressures at the nodes and the flow rates in the pipes must satisfy the flow equations, and together with nodes' loads must fulfill the first and second Kirchhoff's laws .
There are many methods of analyzing the mathematical models of gas networks but they can be divided into two types as the networks, the solvers for low pressure networks and solvers for high pressure networks . The networks equations are nonlinear and are generally solved by some of Newton iteration ; rather than use the full set of variables it is possible to eliminate some of them. Based on the type of elimination we [ who? ] can get solution techniques are termed either nodal or loop methods.
The method is based on the set of the nodal equations which are simply mathematical representation of Kirchhoff's first law which states that the inlet and outlet flow at each node should be equal. Initial approximation is made to the nodal pressures. The approximation is then successively corrected until the final solution is reached.
The method is based on the generated loops and the equations are simply mathematical representation of Kirchhoff's second law which states that the sum of the pressure-drops around any loop should be zero. Before using loops method the fundamental set of loops need to be found. Basically the fundamental set of loops can be found by constructing spanning tree for the network. The standard methods for producing spanning tree is based on a breadth-first search or on a depth-first search which are not so efficient for large networks, because the computing time of these methods is proportional to n 2 , where n is the number of pipes in the network. More efficient method for large networks is the forest method and its computational time is proportional to n*log 2 n.
The loops that are produced from the spanning tree are not the best set that could be produced. There is often significant overlap between loops with some pipes shared between several loops. This usually slows convergence, therefore the loops' reduction algorithm needs to be applied to minimize the loops overlapping. This is usually performed by replacing the loops in the original fundamental set by smaller loops produced by linear combination of the original set.
The Newton loop-node method is based on Kirchhoff’s first and second laws. The Newton loop-node method is the combination of the Newton nodal and loop methods and does not solve loop equations explicitly. The loop equations are transformed to an equivalent set of nodal equations, which are then solved to yield the nodal pressures. The nodal pressures are used then to calculate the corrections to the chord flows (which is synonymous to loop flows), and the tree branch flows are obtained from them.
The importance of the mathematical methods' efficiency arises from the large scale of simulated network. [ 1 ] It is required that the computation costs of the simulation method be low, this is related to the computation time and computer storage. At the same time the accuracy of the computed values must acceptable for the particular model. | https://en.wikipedia.org/wiki/Gas_networks_simulation |
Diesel fuel , also called diesel oil , heavy oil (historically) or simply diesel , is any liquid fuel specifically designed for use in a diesel engine , a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Therefore, diesel fuel needs good compression ignition characteristics.
The most common type of diesel fuel is a specific fractional distillate of petroleum fuel oil , but alternatives that are not derived from petroleum, such as biodiesel , biomass to liquid (BTL) or gas to liquid (GTL) diesel are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is sometimes called petrodiesel in some academic circles. [ 1 ] Diesel is a high-volume product of oil refineries. [ 2 ]
In many countries, diesel fuel is standardized. For example, in the European Union, the standard for diesel fuel is EN 590 . Ultra-low-sulfur diesel (ULSD) is a diesel fuel with substantially lowered sulfur contents. As of 2016, almost all of the petroleum-based diesel fuel available in the United Kingdom, mainland Europe, and North America is of a ULSD type. Before diesel fuel had been standardized, the majority of diesel engines typically ran on cheap fuel oils . These fuel oils are still used in watercraft diesel engines. Despite being specifically designed for diesel engines, diesel fuel can also be used as fuel for several non-diesel engines, for example the Akroyd engine , the Stirling engine , or boilers for steam engines . Diesel is often used in heavy trucks . However, diesel exhaust , especially from older engines, can cause health damage. [ 3 ] [ 4 ]
Diesel fuel has many colloquial names; most commonly, it is simply referred to as diesel . In the United Kingdom, diesel fuel for road use is commonly called diesel or sometimes white diesel if required to differentiate it from a reduced-tax agricultural-only product containing an identifying coloured dye known as red diesel . The official term for white diesel is DERV , standing for diesel-engine road vehicle . [ 5 ] In Australia , diesel fuel is also known as distillate [ 6 ] (not to be confused with "distillate" in an older sense referring to a different motor fuel), and in Indonesia (as well in Israel ), and most of the Middle East, it is known as Solar , a trademarked name from the country's national petroleum company Pertamina . The term gas oil (French: gazole ) is sometimes also used to refer to diesel fuel.
Diesel fuel originated from experiments conducted by German scientist and inventor Rudolf Diesel for his compression-ignition engine which he invented around 1892. Originally, Diesel did not consider using any specific type of fuel. Instead, he claimed that the operating principle of his rational heat motor would work with any kind of fuel in any state of matter. [ 7 ] The first diesel engine prototype and the first functional Diesel engine were only designed for liquid fuels. [ 8 ]
At first, Diesel tested crude oil from Pechelbronn , but soon replaced it with petrol and kerosene , because crude oil proved to be too viscous, [ 9 ] with the main testing fuel for the Diesel engine being kerosene ( paraffin ). [ 10 ] Diesel experimented with types of lamp oil from various sources, as well as types of petrol and ligroin , which all worked well as Diesel engine fuels. Later, Diesel tested coal tar creosote , [ 11 ] paraffin oil, crude oil, gasoline and fuel oil , which eventually worked as well. [ 12 ] In Scotland and France, shale oil was used as fuel for the first 1898 production Diesel engines because other fuels were too expensive. [ 13 ] In 1900, the French Otto society built a Diesel engine for the use with crude oil, which was exhibited at the 1900 Paris Exposition [ 14 ] and the 1911 World's Fair in Paris. [ 15 ] The engine actually ran on peanut oil instead of crude oil, and no modifications were necessary for peanut oil operation. [ 14 ]
During his first Diesel engine tests, Diesel also used illuminating gas as fuel, and managed to build functional designs, both with and without pilot injection. [ 16 ] According to Diesel, neither was a coal-dust–producing industry existent, nor was fine, high-quality coal-dust commercially available in the late 1890s. This is the reason why the Diesel engine was never designed or planned as a coal-dust engine. [ 17 ] Only in December 1899, did Diesel test a coal-dust prototype, which used external mixture formation and liquid fuel pilot injection. [ 18 ] This engine proved to be functional, but suffered from piston ring failure after a few minutes due to coal dust deposition. [ 19 ]
Before diesel fuel was standardised, diesel engines typically ran on cheap fuel oils. In the United States, these were distilled from petroleum, whereas in Europe, coal-tar creosote oil was used. Some diesel engines were fuelled with mixtures of fuels, such as petrol, kerosene, rapeseed oil, or lubricating oil which were cheaper because, at the time, they were not being taxed. [ 20 ] The introduction of motor-vehicle diesel engines, such as the Mercedes-Benz OM 138 , in the 1930s meant that higher-quality fuels with proper ignition characteristics were needed. At first no improvements were made to motor-vehicle diesel fuel quality. After World War II, the first modern high-quality diesel fuels were standardised. These standards were, for instance, the DIN 51601, VTL 9140–001, and NATO F 54 standards. [ 21 ] In 1993, the DIN 51601 was rendered obsolete by the new EN 590 standard, which has been used in the European Union ever since. In sea-going watercraft, where diesel propulsion had gained prevalence by the late 1970s due to increasing fuel costs caused by the 1970s energy crisis , cheap heavy fuel oils are still used instead of conventional motor-vehicle diesel fuel. These heavy fuel oils (often called Bunker C ) can be used in diesel-powered and steam-powered vessels. [ 22 ]
Diesel fuel is produced from various sources, the most common being petroleum . Other sources include biomass , animal fat , biogas , natural gas , and coal liquefaction .
Petroleum diesel is the most common type of diesel fuel. It is produced by the fractional distillation of crude oil between 200 and 350 °C (392 and 662 °F) at atmospheric pressure , resulting in a mixture of carbon chains that typically contain between 9 and 25 carbon atoms per molecule . [ 23 ] This fraction is subjected to hydrodesulfurization .
Usually such "straight-run" diesel is insufficient in supply and quality, so other sources of diesel fuels are blended in. One major source of additional diesel fuel is obtained by cracking heavier fractions, using visbreaking and coking. This technology converts less useful fractions but the product contains olefins ( alkenes ) which require hydrogenation to give the saturated hydrocarbons as desired. Another refinery stream that contributes to diesel fuel is hydrocracking . Finally, kerosene is added to modify its viscosity. [ 24 ]
Synthetic diesel can be produced from many carbonaceous precursors but natural gas is most important. Raw materials are converted to synthesis gas which by the Fischer–Tropsch process is converted to a synthetic diesel. [ 25 ] Synthetic diesel produced in this way generally is mainly paraffins with low sulfur and aromatics content. This material is blended often into the above mentions petroleum derived diesel. [ 24 ]
Biodiesel is obtained from vegetable oil or animal fats (bio lipids ) which are mainly fatty acid methyl esters (FAME), and transesterified with methanol . It can be produced from many types of oils, the most common being rapeseed oil (rapeseed methyl ester, RME) in Europe and soybean oil (soy methyl ester, SME) in the US. Methanol can also be replaced with ethanol for the transesterification process, which results in the production of ethyl esters. The transesterification processes use catalysts, such as sodium or potassium hydroxide, to convert vegetable oil and methanol into biodiesel and the undesirable byproducts glycerine and water, which will need to be removed from the fuel along with methanol traces. Biodiesel can be used pure (B100) in engines where the manufacturer approves such use, but it is more often used as a mix with diesel, BXX where XX is the biodiesel content in percent. [ 26 ] [ 27 ]
FAME used as fuel is specified in DIN EN 14214 [ 28 ] and ASTM D6751 standards. [ 29 ]
In the US, diesel is recommended to be stored in a yellow container to differentiate it from kerosene , which is typically kept in blue containers, and gasoline (petrol), which is typically kept in red containers. [ 30 ] In the UK, diesel is normally stored in a black container to differentiate it from unleaded or leaded petrol, which are stored in green and red containers, respectively. [ 31 ]
Ethylene-vinyl acetate (EVA) is added to diesel as a "cold flow improver". 50-500 ppm of EVA inhibits crystallization of waxes, which can block fuel filters. Antifoaming agents ( silicones ), antioxidants ( hindered phenols ), and "metal deactivating agents" (salicylaldimines) are other additives. Their use is dictated by the particular composition of and storage plans for diesel fuels. Each is added at the 5-50 ppm level. [ 24 ]
The diesel engine is a multifuel engine and can run on a huge variety of fuels. However, development of high-performance, high-speed diesel engines for cars and lorries in the 1930s meant that a proper fuel specifically designed for such engines was needed: diesel fuel. In order to ensure consistent quality, diesel fuel is standardised; the first standards were introduced after World War II. [ 21 ] Typically, a standard defines certain properties of the fuel, such as cetane number , density , flash point , sulphur content, or biodiesel content. Diesel fuel standards include:
Diesel fuel
Biodiesel fuel
The principal measure of diesel fuel quality is its cetane number . A cetane number is a measure of the delay of ignition of a diesel fuel. [ 32 ] A higher cetane number indicates that the fuel ignites more readily when sprayed into hot compressed air. [ 32 ] European (EN 590 standard) road diesel has a minimum cetane number of 51. Fuels with higher cetane numbers, normally "premium" diesel fuels with additional cleaning agents and some synthetic content, are available in some markets.
About 86.1% of diesel fuel mass is carbon, and when burned, it offers a net heating value of 43.1 MJ/kg as opposed to 43.2 MJ/kg for gasoline. Due to the higher density, diesel fuel offers a higher volumetric energy density: the density of EN 590 diesel fuel is defined as 0.820 to 0.845 kg/L (6.84 to 7.05 lb/US gal) at 15 °C (59 °F), about 9.0-13.9% more than EN 228 gasoline (petrol)'s 0.720–0.775 kg/L (6.01–6.47 lb/US gal) at 15 °C, which should be put into consideration when comparing volumetric fuel prices. The CO 2 emissions from diesel are 73.25 g/MJ, just slightly lower than for gasoline at 73.38 g/MJ. [ 33 ]
Diesel fuel is generally simpler to refine from petroleum than gasoline. Additional refining is required to remove sulfur, which contributes to a sometimes higher cost. In many parts of the United States and throughout the United Kingdom and Australia, [ 34 ] diesel fuel may be priced higher than petrol per gallon or liter . [ 35 ] [ 36 ] Reasons for higher-priced diesel include the shutdown of some refineries in the Gulf of Mexico , diversion of mass refining capacity to gasoline production, and a recent transfer to ultra-low-sulfur diesel (ULSD), which causes infrastructural complications. [ 37 ] In Sweden, a diesel fuel designated as MK-1 (class 1 environmental diesel) is also being sold. This is a ULSD that also has a lower aromatics content, with a limit of 5%. [ 38 ] This fuel is slightly more expensive to produce than regular ULSD. In Germany, the fuel tax on diesel fuel is about 28% lower than the petrol fuel tax.
Diesel fuel is similar to heating oil , which is used in central heating . In Europe, the United States, and Canada, taxes on diesel fuel are higher than on heating oil due to the fuel tax , and in those areas, heating oil is marked with fuel dyes and trace chemicals to prevent and detect tax fraud . "Untaxed" diesel (sometimes called "off-road diesel" or "red diesel" due to its red dye) is available in some countries for use primarily in agricultural applications, such as fuel for tractors, recreational and utility vehicles or other noncommercial vehicles that do not use public roads . This fuel may have sulfur levels that exceed the limits for road use in some countries (e.g. US).
This untaxed diesel is dyed red for identification, [ 39 ] and using this untaxed diesel fuel for a typically taxed purpose (such as driving use), the user can be fined (e.g. US$10,000 in the US). In the United Kingdom, Belgium and the Netherlands, it is known as red diesel (or gas oil), and is also used in agricultural vehicles, home heating tanks, refrigeration units on vans/trucks which contain perishable items such as food and medicine and for marine craft. Diesel fuel, or marked gas oil is dyed green in the Republic of Ireland and Norway. The term "diesel-engined road vehicle" (DERV) is used in the UK as a synonym for unmarked road diesel fuel. In India, taxes on diesel fuel are lower than on petrol, as the majority of the transportation for grain and other essential commodities across the country runs on diesel.
Taxes on biodiesel in the US vary between states. Some states (Texas, for example) have no tax on biodiesel and a reduced tax on biodiesel blends equivalent to the amount of biodiesel in the blend, so that B20 fuel is taxed 20% less than pure petrodiesel. [ 40 ] Other states, such as North Carolina, tax biodiesel (in any blended configuration) the same as petrodiesel, although they have introduced new incentives to producers and users of all biofuels. [ 41 ]
Diesel fuel is mostly used in high-speed diesel engines, especially motor-vehicle (e.g. car, lorry) diesel engines, but not all diesel engines run on diesel fuel. For example, large two-stroke watercraft engines typically use heavy fuel oils instead of diesel fuel, [ 22 ] and certain types of diesel engines, such as MAN M-System engines, are designed to run on petrol with knock resistances of up to 86 RON. [ 42 ] On the other hand, gas turbine and some other types of internal combustion engines, and external combustion engines , can also be designed to take diesel fuel.
The viscosity requirement of diesel fuel is usually specified at 40 °C. [ 32 ] A disadvantage of diesel fuel in cold climates is that its viscosity increases as the temperature decreases, changing it into a gel (see Compression Ignition – Gelling ) that cannot flow in fuel systems. Special low-temperature diesel contains additives to keep it liquid at lower temperatures.
Trucks and buses , which were often otto-powered in the 1920s through 1950s, are now almost exclusively diesel-powered. Due to its ignition characteristics, diesel fuel is thus widely used in these vehicles. Since diesel fuel is not well-suited for otto engines, passenger cars, which often use otto or otto-derived engines, typically run on petrol instead of diesel fuel. However, especially in Europe and India, many passenger cars have, due to better engine efficiency, [ 43 ] diesel engines, and thus run on regular diesel fuel.
Diesel displaced coal and fuel oil for steam-powered vehicles in the latter half of the 20th century, and is now used almost exclusively for the combustion engines of self-powered rail vehicles (locomotives and railcars). [ 44 ] [ 45 ]
In general, diesel engines are not well-suited for planes and helicopters. This is because of the diesel engine's comparatively low power-to-mass ratio , meaning that diesel engines are typically rather heavy, which is a disadvantage in aircraft. Therefore, there is little need for using diesel fuel in aircraft, and diesel fuel is not commercially used as aviation fuel. Instead, petrol ( Avgas ), and jet fuel (e. g. Jet A-1) are used. However, especially in the 1920s and 1930s, numerous series-production aircraft diesel engines that ran on fuel oils were made, because they had several advantages: their fuel consumption was low, they were reliable, not prone to catching fire, and required minimal maintenance. The introduction of petrol direct injection in the 1930s outweighed these advantages, and aircraft diesel engines quickly fell out of use. [ 46 ] With improvements in power-to-mass ratios of diesel engines, several on-road diesel engines have been converted to and certified for aircraft use since the early 21st century. These engines typically run on Jet A-1 aircraft fuel (but can also run on diesel fuel). Jet A-1 has ignition characteristics similar to diesel fuel, and is thus suited for certain (but not all) diesel engines. [ 47 ]
Until World War II, several military vehicles, especially those that required high engine performance ( armored fighting vehicles , for example the M26 Pershing or Panther tanks), used conventional otto engines and ran on petrol. Ever since World War II, several military vehicles with diesel engines have been made, capable of running on diesel fuel. This is because diesel engines are more fuel efficient, and diesel fuel is less prone to catching fire. [ 48 ] Some of these diesel-powered vehicles (such as the Leopard 1 or MAN 630 ) still ran on petrol, and some military vehicles were still made with otto engines (e. g. Ural-375 or Unimog 404 ), incapable of running on diesel fuel.
Today's tractors and heavy equipment are mostly diesel-powered. Among tractors, only the smaller classes may also offer gasoline-fuelled engines. The dieselization of tractors and heavy equipment began in Germany before World War II but was unusual in the United States until after that war. During the 1950s and 1960s, it progressed in the US as well. Diesel fuel is commonly used in oil and gas extracting equipment, although some locales use electric or natural gas powered equipment.
Tractors and heavy equipment were often multifuel in the 1920s through 1940s, running either spark-ignition and low-compression engines, akryod engines, or diesel engines. Thus many farm tractors of the era could burn gasoline, alcohol , kerosene , and any light grade of fuel oil such as heating oil , or tractor vaporising oil , according to whichever was most affordable in a region at any given time. On US farms during this era, the name "distillate" often referred to any of the aforementioned light fuel oils. Spark ignition engines did not start as well on distillate, so typically a small auxiliary gasoline tank was used for cold starting, and the fuel valves were adjusted several minutes later, after warm-up, to transition to distillate. Engine accessories such as vaporizers and radiator shrouds were also used, both with the aim of capturing heat, because when such an engine was run on distillate, it ran better when both it and the air it inhaled were warmer rather than at ambient temperature. Dieselization with dedicated diesel engines (high-compression with mechanical fuel injection and compression ignition) replaced such systems and made more efficient use of the diesel fuel being burned.
Poor quality diesel fuel has been used as an extraction agent for liquid–liquid extraction of palladium from nitric acid mixtures. [ 49 ] Such use has been proposed as a means of separating the fission product palladium from PUREX raffinate which comes from used nuclear fuel . [ 49 ] In this system of solvent extraction, the hydrocarbons of the diesel act as the diluent while the di alkyl sulfides act as the extractant. [ 49 ] This extraction operates by a solvation mechanism. [ 49 ] So far, neither a pilot plant nor full scale plant has been constructed to recover palladium, rhodium or ruthenium from nuclear wastes created by the use of nuclear fuel . [ 50 ]
Diesel fuel is often used as the main ingredient in oil-base mud drilling fluid. [ 51 ] The advantage of using diesel is its low cost and its ability to drill a wide variety of difficult strata, including shale, salt and gypsum formations. [ 51 ] Diesel-oil mud is typically mixed with up to 40% brine water. [ 52 ] Due to health, safety and environmental concerns, Diesel-oil mud is often replaced with vegetable, mineral, or synthetic food-grade oil-base drilling fluids, although diesel-oil mud is still in widespread use in certain regions. [ 53 ]
During development of rocket engines in Germany during World War II J-2 Diesel fuel was used as the fuel component in several engines including the BMW 109-718 . [ 54 ] J-2 diesel fuel was also used as a fuel for gas turbine engines. [ 54 ]
In the United States, petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n , iso , and cycloparaffins ), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes ). [ 55 ] The average chemical formula for common diesel fuel is C 12 H 23 , ranging approximately from C 10 H 20 to C 15 H 28 . [ 56 ]
Most diesel fuels freeze at common winter temperatures, while the temperatures greatly vary. [ 57 ] Petrodiesel typically freezes around temperatures of −8.1 °C (17.4 °F), whereas biodiesel freezes between temperatures of 2 to 15 °C (36 to 59 °F). [ 57 ] The viscosity of diesel noticeably increases as the temperature decreases, changing it into a gel at temperatures of −19 to −15 °C (−2 to 5 °F), that cannot flow in fuel systems. Conventional diesel fuels vaporise at temperatures between 149 °C and 371 °C. [ 32 ]
Conventional diesel flash points vary between 52 and 96 °C, which makes it safer than petrol and unsuitable for spark-ignition engines. [ 58 ] Unlike petrol, the flash point of a diesel fuel has no relation to its performance in an engine nor to its auto ignition qualities. [ 32 ]
As a good approximation the chemical formula of diesel is C n H 2n . Diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen has a molar mass of about 1 g/mol, so the fraction by weight of carbon in EN 590 diesel fuel is roughly 12/14.
The reaction of diesel combustion is given by:
2 C n H 2n + 3n O 2 ⇌ 2n CO 2 + 2n H 2 O
Carbon dioxide has a molar mass of 44g/mol as it consists of 2 atoms of oxygen (16 g/mol) and 1 atom of carbon (12 g/mol). So 12 g of carbon yield 44 g of Carbon dioxide.
Diesel has a density of 838 g per liter.
Putting everything together the mass of carbon dioxide that is produced by burning 1 liter of diesel fuel can be calculated as:
0.838 k g / L ⋅ 12 14 ⋅ 44 12 = 2.63 k g / L {\displaystyle 0.838kg/L\cdot {\frac {12}{14}}\cdot {\frac {44}{12}}=2.63kg/L}
The figure obtained with this estimation is close to the values found in the literature.
For gasoline, with a density of 0.75 kg/L and a ratio of carbon to hydrogen atoms of about 6 to 14, the estimated value of carbon emission if 1 liter of gasoline is burnt gives: [ 59 ]
0.75 k g / L ⋅ 6 ⋅ 12 6 ⋅ 12 + 14 ⋅ 1 ⋅ 44 12 = 2.3 k g / L {\displaystyle 0.75kg/L\cdot {{\frac {6\cdot 12}{6\cdot 12+14}}\cdot 1}\cdot {\frac {44}{12}}=2.3kg/L}
In the past, diesel fuel contained higher quantities of sulfur . European emission standards and preferential taxation have forced oil refineries to dramatically reduce the level of sulfur in diesel fuels. In the European Union, the sulfur content has dramatically reduced during the last 20 years. Automotive diesel fuel is covered in the European Union by standard EN 590 . In the 1990s specifications allowed a content of 2000 ppm max of sulfur, reduced to a limit of 350 ppm by the beginning of the 21st century with the introduction of Euro 3 specifications. The limit was lowered with the introduction of Euro 4 by 2006 to 50 ppm ( ULSD , Ultra Low Sulfur Diesel). The standard for diesel fuel in force in Europe as of 2009 is the Euro 5, with a maximum content of 10 ppm. [ 60 ]
In the United States, more stringent emission standards have been adopted with the transition to ULSD starting in 2006, and becoming mandatory on June 1, 2010 (see also diesel exhaust ).
There has been much discussion and misunderstanding of algae in diesel fuel. Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive, but some microbes can survive and feed on the diesel fuel. [ 61 ]
These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters. [ 62 ]
Water in fuel can damage a fuel injection pump . Some diesel fuel filters also trap water. Water contamination in diesel fuel can lead to freezing while in the fuel tank. The freezing water that saturates the fuel will sometimes clog the fuel injector pump. [ 63 ] Once the water inside the fuel tank has started to freeze, gelling is more likely to occur. When the fuel is gelled it is not effective until the temperature is raised and the fuel returns to a liquid state.
Diesel is less flammable than gasoline / petrol . However, because it evaporates slowly, any spills on a roadway can pose a slip hazard to vehicles. [ 64 ] After the light fractions have evaporated, a greasy slick is left on the road which reduces tire grip and traction, and can cause vehicles to skid. The loss of traction is similar to that encountered on black ice , resulting in especially dangerous situations for two-wheeled vehicles, such as motorcycles and bicycles , in roundabouts . | https://en.wikipedia.org/wiki/Gas_oil |
Gas phase electrophoretic molecular mobility analysis ( GEMMA ) is a method for chemical analysis in which nanoflow electrospray ionization creates highly charged ions from macromolecules that are charge reduced and separated in a differential mobility analyzer . [ 1 ] [ 2 ]
This physical chemistry -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gas_phase_electrophoretic_molecular_mobility_analysis |
Gas separation can refer to any of a number of techniques used to separate gases , either to give multiple products or to purify a single product.
Pressure swing adsorption (PSA) pressurizes and depressurizes a multicomponent gas around an adsorbent medium to selectively adsorb some components of a gas while leaving other components free-flowing. [ 1 ]
Vacuum swing adsorption (VSA) uses the same principle as PSA but swings between vacuum pressures and atmospheric pressure . [ 2 ] PSA and VSA techniques may be combined and are called "vacuum pressure swing adsorption" (VPSA) in this case.
Temperature swing adsorption (TSA) is similar to other swing adsorption techniques but cycles the temperature of the adsorbent bed-gas system instead of the gas pressure to achieve separation. [ 2 ]
Cryogenic distillation is typically only used for very high volumes because of its nonlinear cost-scale relationship, which makes the process more economical at larger scales. Because of this it is typically only used for air separation. [ 3 ] | https://en.wikipedia.org/wiki/Gas_separation |
A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure . Gas storage cylinders may also be called bottles . Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid , or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened or dished bottom end or foot ring, with the cylinder valve screwed into the internal neck thread at the top for connecting to the filling or receiving apparatus. [ 1 ]
Gas cylinders may be grouped by several characteristics, such as construction method, material, pressure group, class of contents, transportability, and re-usability. [ 2 ]
The size of a pressurised gas container that may be classed as a gas cylinder is typically 0.5 litres to 150 litres. Smaller containers may be termed gas cartridges, and larger may be termed gas tubes, tanks, or other specific type of pressure vessel. A gas cylinder is used to store gas or liquefied gas at pressures above normal atmospheric pressure. [ 2 ] In South Africa, a gas storage cylinder implies a refillable transportable container with a water capacity volume of up to 150 litres. Refillable transportable cylindrical containers from 150 to 3,000 litres water capacity are referred to as tubes. [ 1 ]
In the United States, " bottled gas " typically refers to liquefied petroleum gas . "Bottled gas" is sometimes used in medical supply, especially for portable oxygen tanks . Packaged industrial gases are frequently called "cylinder gas", though "bottled gas" is sometimes used. The term propane tank is also used for cylinders for propane. [ citation needed ]
The United Kingdom and other parts of Europe more commonly refer to "bottled gas" when discussing any usage, whether industrial, medical, or liquefied petroleum. In contrast, what is called liquefied petroleum gas in the United States is known generically in the United Kingdom as "LPG" and it may be ordered by using one of several trade names , or specifically as butane or propane , depending on the required heat output. [ citation needed ]
The term cylinder in this context is sometimes confused with tank , the latter being an open-top or vented container that stores liquids under gravity, though the term scuba tank is commonly used to refer to a compressed gas cylinder used for breathing gas supply to an underwater breathing apparatus .
Since fibre-composite materials have been used to reinforce pressure vessels, various types of cylinder distinguished by the construction method and materials used have been defined: [ 7 ] [ 8 ]
Assemblies comprising a group of cylinders mounted together for combined use or transport:
All-metal cylinders are the most rugged and usually the most economical option, but are relatively heavy. Steel is generally the most resistant to rough handling and most economical, and is often lighter than aluminium for the same working pressure, capacity, and form factor due to its higher specific strength. The inspection interval of industrial steel cylinders has increased from 5 or 6 years to 10 years. Diving cylinders that are used in water must be inspected more often; intervals tend to range between 1 and 5 years. Steel cylinders are typically withdrawn from service after 70 years, or may continue to be used indefinitely providing they pass periodic inspection and testing. [ citation needed ] When they were found to have inherent structural problems, certain steel and aluminium alloys were withdrawn from service, or discontinued from new production, while existing cylinders may require different inspection or testing, but remain in service provided they pass these tests. [ citation needed ]
For very high pressures, composites have a greater mass advantage. Due to the very high tensile strength of carbon fiber reinforced polymer , these vessels can be very light, but are more expensive to manufacture. [ 12 ] Filament wound composite cylinders are used in fire fighting breathing apparatus, high altitude climbing, and oxygen first aid equipment because of their low weight, but are rarely used for diving, due to their high positive buoyancy . They are occasionally used when portability for accessing the dive site is critical, such as in cave diving where the water surface is far from the cave entrance. [ 13 ] [ 14 ] Composite cylinders certified to ISO-11119-2 or ISO-11119-3 may only be used for underwater applications if they are manufactured in accordance with the requirements for underwater use and are marked "UW". [ 15 ]
Cylinders reinforced with or made from a fibre reinforced material usually must be inspected more frequently than metal cylinders, e.g. , every 5 instead of 10 years, and must be inspected more thoroughly than metal cylinders as they are more susceptible to impact damage. They may also have a limited service life. [ citation needed ] Fibre composite cylinders were originally specified for a limited life span of 15, 20 or 30 years, but this has been extended when they proved to be suitable for longer service. [ citation needed ]
The Type 1 pressure vessel is a seamless cylinder normally made of cold-extruded aluminum or forged steel . [ 16 ] The pressure vessel comprises a cylindrical section of even wall thickness, with a thicker base at one end, and domed shoulder with a central neck to attach a cylinder valve or manifold at the other end.
Occasionally other materials may be used. Inconel has been used for non-magnetic and highly corrosion resistant oxygen compatible spherical high-pressure gas containers for the US Navy's Mk-15 and Mk-16 mixed gas rebreathers, and a few other military rebreathers.
Most aluminum cylinders are flat bottomed, allowing them to stand upright on a level surface, but some were manufactured with domed bottoms.
Aluminum cylinders are usually manufactured by cold extrusion of aluminum billets in a process which first presses the walls and base, then trims the top edge of the cylinder walls, followed by press forming the shoulder and neck. The final structural process is machining the neck outer surface, boring and cutting the neck threads and O-ring groove. The cylinder is then heat-treated, tested and stamped with the required permanent markings. [ 17 ]
Steel cylinders are often used because they are harder and more resistant to external surface impact and abrasion damage, and can tolerate higher temperatures without affecting material properties. They also may have a lower mass than aluminium cylinders with the same gas capacity , due to considerably higher specific strength . Steel cylinders are more susceptible than aluminium to external corrosion, particularly in seawater, and may be galvanized or coated with corrosion barrier paints to resist corrosion damage. It is not difficult to monitor external corrosion, and repair the paint when damaged, and steel cylinders which are well maintained have a long service life, often longer than aluminium cylinders, as they are not susceptible to fatigue damage when filled within their safe working pressure limits.
Steel cylinders are manufactured with domed (convex) and dished (concave) bottoms. The dished profile allows them to stand upright on a horizontal surface, and is the standard shape for industrial cylinders. The cylinders used for emergency gas supply on diving bells are often this shape, and commonly have a water capacity of about 50 litres ("J"). Domed bottoms give a larger volume for the same cylinder mass, and are the standard for scuba cylinders up to 18 litres water capacity, though some concave bottomed cylinders have been marketed for scuba. Domed end industrial cylinders may be fitted with a press-fitted foot ring to allow upright standing. [ 18 ] [ 19 ]
Steel alloys used for gas cylinder manufacture are authorised by the manufacturing standard. For example, the US standard DOT 3AA requires the use of open-hearth, basic oxygen, or electric steel of uniform quality. Approved alloys include 4130X, NE-8630, 9115, 9125, Carbon-boron and Intermediate manganese, with specified constituents, including manganese and carbon, and molybdenum, chromium, boron, nickel or zirconium. [ 20 ]
Steel cylinders may be manufactured from steel plate discs stamped from annealed plate or coil, which are lubricated and cold drawn to a cylindrical cup form, by a hydraulic press, this is annealed and drawn again in two or three stages, until the final diameter and wall thickness is reached. They generally have a domed base if intended for the scuba market, so they cannot stand up by themselves.For industrial use a dished base allows the cylinder to stand on the end on a flat surface. After forming the base and side walls, the top of the cylinder is trimmed to length, heated and hot spun to form the shoulder and close the neck. This process thickens the material of the shoulder. The cylinder is heat-treated by quenching and tempering to provide the best strength and toughness. The cylinders are machined to provide the neck thread and o-ring seat (if applicable), then chemically cleaned or shot-blasted inside and out to remove mill-scale. After inspection and hydrostatic testing they are stamped with the required permanent markings, followed by external coating with a corrosion barrier paint or hot dip galvanising and final inspection. [ 21 ] [ 4 ]
A related method is to start with seamless steel tube of a suitable diameter and wall thickness, manufactured by a process such as the Mannesmann process , and to close both ends by the hot spinning process. This method is particularly suited to high pressure gas storage tubes , which usually have a threaded neck opening at both ends, so that both ends are processed alike. When a neck opening is only required at one end, the base is spun first and dressed inside for a uniform smooth surface, then the process of closing the shoulder and forming the neck is the same as for the pressed plate method. [ 4 ]
An alternative production method is backward extrusion of a heated steel billet, similar to the cold extrusion process for aluminium cylinders, followed by hot drawing and bottom forming to reduce wall thickness, and trimming of the top edge in preparation for shoulder and neck formation by hot spinning. The other processes are much the same for all production methods. [ 22 ] [ 4 ]
The neck of the cylinder is the part of the end which is shaped as a narrow concentric cylinder, and internally threaded to fit a cylinder valve. There are several standards for neck threads, which include parallel threads where the seal is by an O-ring gasket, and taper threads which seal along the contact surface by deformation of the contact surfaces, and on thread tape or sealing compound . [ 3 ]
Type 2 is hoop wrapped with fibre reinforced resin over the cylindrical part of the cylinder, where circumferential load is highest. The fibres share the circumferential load with the metal core, and achieve a significant weight saving due to efficient stress distribution and high specific strength and stiffness of the composite. The core is a seamless metal cylinder, manufactured in any of the ways suitable for a type 1 cylinder, but with thinner walls, as they only carry about half the load, mainly the axial load. Hoop winding is at an angle to the length axis of close to 90°, so the fibres carry negligible axial load. [ 4 ]
Type 3 is wrapped over the entire cylinder except for the neck, and the metal liner is mainly to make the cylinder gas tight, so very little load is carried by the liner. Winding angles are optimised to carry all the loads (axial and circumferential) from the pressurised gas in the cylinder. Only the neck metal is exposed on the outside. This construction can save in the order of 30% of the mass compared with type 2, as the fibre composite has a higher specific strength than the metal of the type 2 liner that it replaces. [ 4 ]
Type 4 is wrapped in the same way as type 3, but the liner is non-metallic. A metal neck boss is fitted to the shoulder of the plastic liner before winding, and this carries the neck threads for the cylinder valve. The outside of the neck of the insert is not covered by the fibre wrapping, and may have axial ridges to engage with a wrench or clamp for torsional support when fitting or removing the cylinder valve. There is a mass reduction compared with type 3 due to the lower density of the plastic liner. [ 4 ]
A welded gas cylinder comprises two or more shell components joined by welding. The most commonly used material is steel, but stainless steel, aluminium and other alloys can be used when they are better suited to the application. Steel is strong, resistant to physical damage, easy to weld, relatively low cost, and usually adequate for corrosion resistance, and provides an economical product.
The components of the shell are usually domed ends, and often a rolled cylindrical centre section. The ends are usually domed by cold pressing from a circular blank, and may be drawn in two or more stages to get the final shape, which is generally semi-elliptical in section. The end blank is typically punched from sheet, drawn to the required section, edges trimmed to size and necked for overlap where appropriate, and hole(s) for the neck and other fittings punched. The neck boss is inserted from the concave side and welded in place before shell assembly. [ 23 ]
Smaller cylinders are typically assembled from a top and bottom dome, with an equatorial weld seam. Larger cylinders with a longer cylindrical body comprise dished ends circumferentially welded to a rolled central cylindrical section with a single longitudinal welded seam. Welding is typically automated gas metal arc welding . [ 23 ]
Typical accessories which are welded to the outside of the cylinder include a foot ring, a valve guard with lifting handles, and a neck boss threaded for the valve. Occasionally other through-shell and external fittings are also welded on. [ 23 ]
After welding, the assembly may be heat treated for stress-relief and to improve mechanical characteristics, cleaned by shotblasting , and coated with a protective and decorative coating. Testing and inspection for quality control will take place at various stages of production. [ 23 ]
The transportation of high-pressure cylinders is regulated by many governments throughout the world. Various levels of testing are generally required by the governing authority for the country in which it is to be transported while filled. In the United States, this authority is the United States Department of Transportation (DOT). Similarly in the UK, the European transport regulations (ADR) are implemented by the Department for Transport (DfT). For Canada, this authority is Transport Canada (TC). Cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriters Laboratories (UL). Each manufacturer of high-pressure cylinders is required to have an independent quality agent that will inspect the product for quality and safety.
Within the UK the " competent authority " — the Department for Transport (DfT) — implements the regulations and appointment of authorised cylinder testers is conducted by United Kingdom Accreditation Service (UKAS), who make recommendations to the Vehicle Certification Agency (VCA) for approval of individual bodies.
There are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test , burst test, ultimate tensile strength , Charpy impact test and pressure cycling.
During the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the serial number, date of manufacture, the manufacture's registered code and sometimes the test pressure. Other information may also be stamped, depending on the regulation requirements.
High-pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years. [ 24 ] In the United States, hydrostatic or ultrasonic testing is required either every five years or every ten years, depending on cylinder and its service.
Cylinder neck thread can be to any one of several standards. Both taper thread sealed with thread tape and parallel thread sealed with an O-ring have been found satisfactory for high pressure service, but each has advantages and disadvantages for specific use cases, and if there are no regulatory requirements, the type may be chosen to suit the application. [ 3 ]
A tapered thread provides simple assembly, but requires high torque for establishing a reliable seal, which causes high radial forces in the neck, and has a limited number of times it can be used before it is excessively deformed. This can be extended a bit by always returning the same fitting to the same cylinder, and avoiding over-tightening. [ 3 ]
In Australia, Europe and North America, tapered neck threads are generally preferred for inert, flammable, corrosive and toxic gases, but when aluminium cylinders are used for oxygen service to United States Department of Transportation (DOT) or Transport Canada (TC) specifications in North America, the cylinders must have parallel thread. DOT and TC allow UN pressure vessels to have tapered or parallel threaded openings. In the US, 49 CFR Part 171.11 applies, and in Canada, CSA B340-18 and CSA B341-18. In Europe and other parts of the world, tapered thread is preferred for cylinder inlets for oxidising gases. [ 3 ]
Scuba cylinders typically have a much shorter interval between internal inspections, so the use of tapered thread is less satisfactory due to the limited number of times a tapered thread valve can be re-used before it wears out, [ 3 ] so parallel thread is generally used for this application. [ 1 ]
Parallel thread can be tightened sufficiently to form a good seal with the O-ring without lubrication, which is an advantage when the lubricant may react with the O-ring or the contents. Repeated secure installations are possible with different combinations of valve and cylinder provided they have compatible thread and correct O-ring seals. Parallel thread is more likely to give the technician warning of residual internal pressure by leaking or extruding the O-ring before catastrophic failure when the O-ring seal is broken during removal of the valve. The O-ring size must be correct for the combination of cylinder and valve, and the material must be compatible with the contents and any lubricant used. [ 3 ]
Gas cylinders usually have an angle stop valve at one end, and the cylinder is usually oriented so the valve is on top. During storage, transportation, and handling when the gas is not in use, a cap may be screwed over the protruding valve to protect it from damage or breaking off in case the cylinder were to fall over. Instead of a cap, cylinders sometimes have a protective collar or neck ring around the valve assembly which has an opening for access to fit a regulator or other fitting to the valve outlet, and access to operate the valve. Installation of valves for high pressure aluminum alloy cylinders is described in the guidelines: CGA V-11, Guideline for the Installation of Valves into High Pressure Aluminum Alloy Cylinders and ISO 13341, Transportable gas cylinders—Fitting of valves to gas cylinders. [ 3 ]
The valves on industrial, medical and diving cylinders usually have threads or connection geometries of different handedness, sizes and types that depend on the category of gas, making it more difficult to mistakenly misuse a gas. For example, a hydrogen cylinder valve outlet does not fit an oxygen regulator and supply line, which could result in catastrophe. Some fittings use a right-hand thread, while others use a left-hand thread ; left-hand thread fittings are usually identifiable by notches or grooves cut into them, and are usually used for flammable gases.
In the United States, valve connections are sometimes referred to as CGA connections , since the Compressed Gas Association (CGA) publishes guidelines on what connections to use for what gasses. For example, an argon cylinder may have a "CGA 580" connection on the valve. High purity gases sometimes use CGA-DISS (" Diameter Index Safety System ") connections.
Medical gases may use the Pin Index Safety System to prevent incorrect connection of gases to services.
In the European Union, DIN connections are more common than in the United States.
In the UK, the British Standards Institution sets the standards. Included among the standards is the use left-hand threaded valves for flammable gas cylinders (most commonly brass, BS4, valves for non-corrosive cylinder contents or stainless steel, BS15, valves for corrosive contents). Non flammable gas cylinders are fitted with right-hand threaded valves (most commonly brass, BS3, valves for non-corrosive components or stainless steel, BS14, valves for corrosive contents). [ 25 ]
When the gas in the cylinder is to be used at low pressure, the cap is taken off and a pressure-regulating assembly is attached to the stop valve. This attachment typically has a pressure regulator with upstream (inlet) and downstream (outlet) pressure gauges and a further downstream needle valve and outlet connection. For gases that remain gaseous under ambient storage conditions, the upstream pressure gauge can be used to estimate how much gas is left in the cylinder according to pressure. For gases that are liquid under storage, e.g., propane, the outlet pressure is dependent on the vapor pressure of the gas, and does not fall until the cylinder is nearly exhausted, although it will vary according to the temperature of the cylinder contents. The regulator is adjusted to control the downstream pressure, which will limit the maximum flow of gas out of the cylinder at the pressure shown by the downstream gauge. For some purposes, such as shielding gas for arc welding, the regulator will also have a flowmeter on the downstream side.
The regulator outlet connection is attached to whatever needs the gas supply.
Because the contents are under pressure and are sometimes hazardous materials , handling bottled gases is regulated. Regulations may include chaining bottles to prevent falling and damaging the valve, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards. If a compressed gas cylinder falls over, causing the valve block to be sheared off, the rapid release of high-pressure gas may cause the cylinder to be violently accelerated, potentially causing property damage, injury, or death. To prevent this, cylinders are normally secured to a fixed object or transport cart with a strap or chain. They can also be stored in a safety cabinet .
In a fire, the pressure in a gas cylinder rises in direct proportion to its temperature . If the internal pressure exceeds the mechanical limitations of the cylinder and there are no means to safely vent the pressurized gas to the atmosphere, the vessel will fail mechanically. If the vessel contents are flammable, this event may result in a "fireball". [ 26 ] Oxidisers such as oxygen and fluorine will produce a similar effect by accelerating combustion in the area affected. If the cylinder's contents are liquid, but become a gas at ambient conditions, this is commonly referred to as a boiling liquid expanding vapour explosion (BLEVE). [ 27 ]
Medical gas cylinders in the UK and some other countries have a fusible plug of Wood's metal in the valve block between the valve seat and the cylinder. [ citation needed ] This plug melts at a comparatively low temperature (70 °C) and allows the contents of the cylinder to escape to the surroundings before the cylinder is significantly weakened by the heat, lessening the risk of explosion.
More common pressure relief devices are a simple burst disc installed in the base of the valve between the cylinder and the valve seat. A burst disc is a small metal gasket engineered to rupture at a pre-determined pressure. Some burst discs are backed with a low-melting-point metal, so that the valve must be exposed to excessive heat before the burst disc can rupture. [ citation needed ]
The Compressed Gas Association publishes a number of booklets and pamphlets on safe handling and use of bottled gases.
There is a wide range of standards relating to the manufacture, use and testing of pressurised gas cylinders and related components. Some examples are listed here.
Gas cylinders are often color-coded , but the codes are not standard across different jurisdictions, and sometimes are not regulated. Cylinder color can not safely be used for positive product identification; cylinders have labels to identify the gas they contain.
The Indian Standard for Gas Cylinder Color Code applies to the identification of the contents of gas cylinders intended for medical use. Each cylinder shall be painted externally in the colours corresponding to its gaseous contents. [ 35 ]
The below are example cylinder sizes and do not constitute an industry standard. [ citation needed ] [ clarification needed ]
(US DOT specs define material, making, and maximum pressure in psi. They are comparable to Transport Canada specs, which shows pressure in bars . A 3E-1800 in DOT nomenclature would be a TC 3EM 124 in Canada. [ 36 ] )
For larger volume, high pressure gas storage units, known as tubes , are available. They generally have a larger diameter and length than high pressure cylinders, and usually have a tapped neck at both ends. They may be mounted alone or in groups on trailers, permanent bases, or intermodal transport frames . Due to their length, they are mounted horizontally on mobile structures. In general usage they are often manifolded together and managed as a unit. [ 37 ] [ 38 ]
Groups of similar size cylinders may be mounted together and connected to a common manifold system to provide larger storage capacity than a single standard cylinder. This is commonly called a cylinder bank or a gas storage bank. The manifold may be arranged to allow simultaneous flow from all the cylinders, or, for a cascade filling system , where gas is tapped off cylinders according to the lowest positive pressure difference between storage and destination cylinder, being a more efficient use of pressurised gas. [ 39 ]
A gas cylinder quad, also known as a gas cylinder bundle, is a group of high pressure cylinders mounted on a transport and storage frame. There are commonly 16 cylinders, each of about 50 litres capacity mounted upright in four rows of four, on a square base with a square plan frame with lifting points on top and may have fork-lift slots in the base. The cylinders are usually interconnected by a manifold for use as a unit, but many variations in layout and structure are possible. [ 9 ] | https://en.wikipedia.org/wiki/Gas_storage_cylinder |
Gas to liquids ( GTL ) is a refinery process to convert natural gas or other gaseous hydrocarbons into longer-chain hydrocarbons, such as gasoline or diesel fuel . Methane -rich gases are converted into liquid synthetic fuels . Two general strategies exist: (i) direct partial combustion of methane to methanol and (ii) Fischer–Tropsch -like processes that convert carbon monoxide and hydrogen into hydrocarbons. Strategy ii is followed by diverse methods to convert the hydrogen-carbon monoxide mixtures to liquids. Direct partial combustion has been demonstrated in nature but not replicated commercially. Technologies reliant on partial combustion have been commercialized mainly in regions where natural gas is inexpensive. [ 1 ] [ 2 ]
The motivation for GTL is to produce liquid fuels, which are more readily transported than methane. Methane must be cooled below its critical temperature of −82.3 °C in order to be liquified under pressure. Because of the associated cryogenic apparatus, LNG tankers are used for transport. Methanol is a conveniently handled combustible liquid, but its energy density is half of that of gasoline. [ 3 ]
A GtL process may be established via the Fischer–Tropsch process which comprises several chemical reactions that convert a mixture of carbon monoxide (CO) and hydrogen (H 2 ) into long chained hydrocarbons. These hydrocarbons are typically liquid or semi-liquid and ideally have the formula (C n H 2 n +2 ).
In order to obtain the mixture of CO and H 2 required for the Fischer–Tropsch process, methane (main component of natural gas) may be subjected to partial oxidation which yields a raw synthesis gas mixture of mostly carbon dioxide , carbon monoxide , hydrogen gas (and sometimes water and nitrogen). [ 4 ] The ratio of carbon monoxide to hydrogen in the raw synthesis gas mixture can be adjusted e.g. using the water gas shift reaction . Removing impurities, particularly nitrogen, carbon dioxide and water, from the raw synthesis gas mixture yields pure synthesis gas (syngas).
The pure syngas is routed into the Fischer–Tropsch process, where the syngas reacts over an iron or cobalt catalyst to produce synthetic hydrocarbons, including alcohols.
Methanol is made from methane (natural gas) in a series of three reactions:
The methanol thus formed may be converted to gasoline by the Mobil process and methanol-to-olefins.
In the early 1970s, Mobil developed an alternative procedure in which natural gas is converted to syngas, and then methanol . The methanol reacts in the presence of a zeolite catalyst to form various compounds. In the first step methanol is partially dehydrated to give dimethyl ether :
The mixture of dimethyl ether and methanol is then further dehydrated over a zeolite catalyst such as ZSM-5 , and in practice is polymerized and hydrogenated to give a gasoline with hydrocarbons of five or more carbon atoms making up 80% of the fuel by weight. The Mobil MTG process is practiced from coal-derived methanol in China by JAMG . A more modern implementation of MTG is the Topsøe improved gasoline synthesis (TiGAS). [ 5 ]
Methanol can be converted to olefins using zeolite and SAPO-based heterogeneous catalysts . Depending on the catalyst pore size, this process can afford either C2 or C3 products, which are important monomers. [ 6 ] [ 7 ]
Methanol to olefins technology is widely used in China in order to produce plastics from coal gasification. It is also discussed as a method to make fossil-free plastics in the future. [ 8 ]
A third gas-to-liquids process builds on the MTG technology by converting natural gas-derived syngas into drop-in gasoline and jet fuel via a thermochemical single-loop process. [ 9 ]
The STG+ process follows four principal steps in one continuous process loop. This process consists of four fixed bed reactors in series in which a syngas is converted to synthetic fuels. The steps for producing high-octane synthetic gasoline are as follows: [ 10 ]
With methane as the predominant target for GTL, much attention has focused on the three enzymes that process methane. These enzymes support the existence of methanotrophs , microorganisms that metabolize methane as their only source of carbon and energy. Aerobic methanotrophs harbor enzymes that oxygenate methane to methanol. The relevant enzymes are methane monooxygenases , which are found both in soluble and particulate (i.e. membrane-bound) varieties. They catalyze the oxygenation according to the following stoichiometry:
Anaerobic methanotrophs rely on the bioconversion of methane using the enzymes called methyl-coenzyme M reductases . These organisms effect reverse methanogenesis . Strenuous efforts have been made to elucidate the mechanisms of these methane-converting enzymes, which would enable their catalysis to be replicated in vitro. [ 11 ]
Biodiesel can be made from CO 2 using the microbes Moorella thermoacetica and Yarrowia lipolytica . This process is known as biological gas-to-liquids. [ 12 ]
Using gas-to-liquids processes, refineries can convert some of their gaseous waste products ( flare gas ) into valuable fuel oils , which can be sold as is or blended only with diesel fuel . The World Bank estimates that over 150 billion cubic metres (5.3 × 10 ^ 12 cu ft) of natural gas are flared or vented annually, an amount worth approximately $30.6 billion, equivalent to 25% of the United States' gas consumption or 30% of the European Union's annual gas consumption, [ 13 ] a resource that could be useful using GTL. Gas-to-liquids processes may also be used for the economic extraction of gas deposits in locations where it is not economical to build a pipeline. This process will be increasingly significant as crude oil resources are depleted .
Royal Dutch Shell produces a diesel from natural gas in a factory in Bintulu , Malaysia . Another Shell GTL facility is the Pearl GTL plant in Qatar , the world's largest GTL facility. [ 14 ] [ 15 ] Sasol has recently built the Oryx GTL facility in Ras Laffan Industrial City , Qatar and together with Uzbekneftegaz and Petronas builds the Uzbekistan GTL plant. [ 16 ] [ 17 ] [ 18 ] Chevron Corporation , in a joint venture with the Nigerian National Petroleum Corporation is commissioning the Escravos GTL in Nigeria , which uses Sasol technology. PetroSA , South Africa's national oil company, owns and operates a 22,000 barrels/day (capacity) GTL plant in Mossel Bay , using Sasol GTL technology. [ 19 ]
New generation of GTL technology is being pursued for the conversion of unconventional, remote and problem gas into valuable liquid fuels. [ 20 ] [ 21 ] GTL plants based on innovative Fischer–Tropsch catalysts have been built by INFRA Technology . Other mainly U.S. companies include Velocys, ENVIA Energy, Waste Management, NRG Energy, ThyssenKrupp Industrial Solutions, Liberty GTL, Petrobras , [ 22 ] Greenway Innovative Energy, [ 23 ] Primus Green Energy, [ 24 ] Compact GTL, [ 25 ] and Petronas. [ 26 ] Several of these processes have proven themselves with demonstration flights using their jet fuels. [ 27 ] [ 28 ]
Another proposed solution to stranded gas involves use of novel FPSO for offshore conversion of gas to liquids such as methanol , diesel , petrol , synthetic crude , and naphtha . [ 29 ]
GTL using natural gas is more economical when there is wide gap between the prevailing natural gas price and crude oil price on a Barrel of oil equivalent (BOE) basis. A coefficient of 0.1724 results in full oil parity . [ 30 ] GTL is a mechanism to bring down the diesel/gasoline/crude oil international prices at par with the natural gas price in an expanding global natural gas production at cheaper than crude oil price. When natural gas is converted in to GTL, the liquid products are easier to export at cheaper price rather than converting in to LNG and further conversion to liquid products in an importing country. [ 31 ] [ 32 ]
However, GTL fuels are much more expensive to produce than conventional fuels. [ 33 ] | https://en.wikipedia.org/wiki/Gas_to_liquids |
A gas torus is a toroidal cloud of gas or plasma that encircles a planet or moon. In the Solar System , gas tori tend to be produced by the interaction of a satellite's atmosphere with the magnetic field of a planet. The most famous example of this is the Io plasma torus , which is produced by the ionization of roughly 1 ton per second of oxygen and sulfur from the tenuous atmosphere of Jupiter's [ 1 ] volcanic moon Io . Before being ionized, these particles are part of a neutral torus, also centered on the orbit of Io. Energetic particle observations also suggest the presence of a neutral torus around the orbit of Jupiter's moon Europa [ 2 ] although such a torus would be merged with the outer portions of an Io torus.
Other examples include the largely neutral torus of oxygen and hydrogen produced by Saturn's moon Enceladus . The Enceladus and Io tori differ in that particles in the Io torus are predominantly ionized while in the Enceladus torus, the neutral density is much greater than the ion density.
After the Voyager encounters, the possibility of a torus of nitrogen produced by Saturn's moon Titan was proposed. Subsequent observations by the Cassini spacecraft showed no clear evidence of such a torus. While neutral nitrogen could not be measured, the ions near the orbit of Titan were primarily hydrogen or water group (O + , OH + , H 2 O + and H 3 O + ) from the Enceladus torus. Trace amounts of nitrogen ions were detected but at levels consistent with an Enceladus source.
This astronomy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gas_torus |
A gas turbine or gas turbine engine is a type of continuous flow internal combustion engine . [ 1 ] The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the direction of flow:
Additional components have to be added to the gas generator to suit its application. Common to all is an air inlet but with different configurations to suit the requirements of marine use, land use or flight at speeds varying from stationary to supersonic. A propelling nozzle is added to produce thrust for flight. An extra turbine is added to drive a propeller ( turboprop ) or ducted fan ( turbofan ) to reduce fuel consumption (by increasing propulsive efficiency) at subsonic flight speeds. An extra turbine is also required to drive a helicopter rotor or land-vehicle transmission ( turboshaft ), marine propeller or electrical generator (power turbine). Greater thrust-to-weight ratio for flight is achieved with the addition of an afterburner .
The basic operation of the gas turbine is a Brayton cycle with air as the working fluid : atmospheric air flows through the compressor that brings it to higher pressure; energy is then added by spraying fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-temperature pressurized gas enters a turbine, producing a shaft work output in the process, used to drive the compressor; the unused energy comes out in the exhaust gases that can be repurposed for external work, such as directly producing thrust in a turbojet engine , or rotating a second, independent turbine (known as a power turbine ) that can be connected to a fan, propeller, or electrical generator. The purpose of the gas turbine determines the design so that the most desirable split of energy between the thrust and the shaft work is achieved. The fourth step of the Brayton cycle (cooling of the working fluid) is omitted, as gas turbines are open systems that do not reuse the same air.
Gas turbines are used to power aircraft , trains , ships , electric generators , pumps , gas compressors , and tanks . [ 2 ]
In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and isobaric heat rejection. Together, these make up the Brayton cycle , also known as the "constant pressure cycle" . [ 28 ] It is distinguished from the Otto cycle , in that all the processes (compression, ignition combustion, exhaust), occur at the same time, continuously. [ 28 ]
In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor ). Heat is added in the combustion chamber and the specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection.
Air is taken in by a compressor, called a gas generator , with either an axial or centrifugal design, or a combination of the two. [ 28 ] This air is then ducted into the combustor section which can be of a annular , can , or can-annular design. [ 28 ] In the combustor section, roughly 70% of the air from the compressor is ducted around the combustor itself for cooling purposes. [ 28 ] The remaining roughly 30% the air is mixed with fuel and ignited by the already burning air-fuel mixture , which then expands producing power across the turbine . [ 28 ] This expansion of the mixture then leaves the combustor section and has its velocity increased across the turbine section to strike the turbine blades, spinning the disc they are attached to, thus creating useful power. Of the power produced, 60-70% is solely used to power the gas generator. [ 28 ] The remaining power is used to power what the engine is being used for, typically an aviation application, being thrust in a turbojet , driving the fan of a turbofan , rotor or accessory of a turboshaft , and gear reduction and propeller of a turboprop . [ 29 ] [ 28 ]
If the engine has a power turbine added to drive an industrial generator or a helicopter rotor, the exit pressure will be as close to the entry pressure as possible with only enough energy left to overcome the pressure losses in the exhaust ducting and expel the exhaust. For a turboprop engine there will be a particular balance between propeller power and jet thrust which gives the most economical operation. In a turbojet engine only enough pressure and energy is extracted from the flow to drive the compressor and other components. The remaining high-pressure gases are accelerated through a nozzle to provide a jet to propel an aircraft.
The smaller the engine, the higher the rotation rate of the shaft must be to attain the required blade tip speed. Blade-tip speed determines the maximum pressure ratios that can be obtained by the turbine and the compressor. This, in turn, limits the maximum power and efficiency that can be obtained by the engine. In order for tip speed to remain constant, if the diameter of a rotor is reduced by half, the rotational speed must double. For example, large jet engines operate around 10,000–25,000 rpm, while micro turbines spin as fast as 500,000 rpm. [ 30 ]
Mechanically, gas turbines can be considerably less complex than Reciprocating engines . Simple turbines might have one main moving part, the compressor/shaft/turbine rotor assembly, with other moving parts in the fuel system. This, in turn, can translate into price. For instance, costing 10,000 ℛℳ for materials, the Jumo 004 proved cheaper than the Junkers 213 piston engine, which was 35,000 ℛℳ , [ 31 ] and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for the BMW 801 . [ 32 ] This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modern jet engines or combined cycle power plants) may have 2 or 3 shafts (spools), hundreds of compressor and turbine blades, movable stator blades, and extensive external tubing for fuel, oil and air systems; they use temperature resistant alloys, and are made with tight specifications requiring precision manufacture. All this often makes the construction of a simple gas turbine more complicated than a piston engine.
Moreover, to reach optimum performance in modern gas turbine power plants the gas needs to be prepared to exact fuel specifications. Fuel gas conditioning systems treat the natural gas to reach the exact fuel specification prior to entering the turbine in terms of pressure, temperature, gas composition, and the related Wobbe index .
The primary advantage of a gas turbine engine is its power to weight ratio. [ citation needed ] Since significant useful work can be generated by a relatively lightweight engine, gas turbines are perfectly suited for aircraft propulsion.
Thrust bearings and journal bearings are a critical part of a design. They are hydrodynamic oil bearings or oil-cooled rolling-element bearings . Foil bearings are used in some small machines such as micro turbines [ 33 ] and also have strong potential for use in small gas turbines/ auxiliary power units [ 34 ]
A major challenge facing turbine design, especially turbine blades , is reducing the creep that is induced by the high temperatures and stresses that are experienced during operation. Higher operating temperatures are continuously sought in order to increase efficiency, but come at the cost of higher creep rates. Several methods have therefore been employed in an attempt to achieve optimal performance while limiting creep, with the most successful ones being high performance coatings and single crystal superalloys . [ 35 ] These technologies work by limiting deformation that occurs by mechanisms that can be broadly classified as dislocation glide, dislocation climb and diffusional flow.
Protective coatings provide thermal insulation of the blade and offer oxidation and corrosion resistance. Thermal barrier coatings (TBCs) are often stabilized zirconium dioxide -based ceramics and oxidation/corrosion resistant coatings (bond coats) typically consist of aluminides or MCrAlY (where M is typically Fe and/or Cr) alloys. Using TBCs limits the temperature exposure of the superalloy substrate, thereby decreasing the diffusivity of the active species (typically vacancies) within the alloy and reducing dislocation and vacancy creep. It has been found that a coating of 1–200 μm can decrease blade temperatures by up to 200 °C (392 °F). [ 36 ] Bond coats are directly applied onto the surface of the substrate using pack carburization and serve the dual purpose of providing improved adherence for the TBC and oxidation resistance for the substrate. The Al from the bond coats forms Al 2 O 3 on the TBC-bond coat interface which provides the oxidation resistance, but also results in the formation of an undesirable interdiffusion (ID) zone between itself and the substrate. [ 37 ] The oxidation resistance outweighs the drawbacks associated with the ID zone as it increases the lifetime of the blade and limits the efficiency losses caused by a buildup on the outside of the blades. [ 38 ]
Nickel-based superalloys boast improved strength and creep resistance due to their composition and resultant microstructure . The gamma (γ) FCC nickel is alloyed with aluminum and titanium in order to precipitate a uniform dispersion of the coherent Ni 3 (Al,Ti) gamma-prime (γ') phases. The finely dispersed γ' precipitates impede dislocation motion and introduce a threshold stress, increasing the stress required for the onset of creep. Furthermore, γ' is an ordered L1 2 phase that makes it harder for dislocations to shear past it. [ 39 ] Further Refractory elements such as rhenium and ruthenium can be added in solid solution to improve creep strength. The addition of these elements reduces the diffusion of the gamma prime phase, thus preserving the fatigue resistance, strength, and creep resistance. [ 40 ] The development of single crystal superalloys has led to significant improvements in creep resistance as well. Due to the lack of grain boundaries, single crystals eliminate Coble creep and consequently deform by fewer modes – decreasing the creep rate. [ 41 ] Although single crystals have lower creep at high temperatures, they have significantly lower yield stresses at room temperature where strength is determined by the Hall-Petch relationship. Care needs to be taken in order to optimize the design parameters to limit high temperature creep while not decreasing low temperature yield strength.
Airbreathing jet engines are gas turbines optimized to produce thrust from the exhaust gases, or from ducted fans connected to the gas turbines. [ 42 ] [ 43 ] Jet engines that produce thrust from the direct impulse of exhaust gases are often called turbojets . While still in service with many militaries and civilian operators, turbojets have mostly been phased out in favor of the turbofan engine due to the turbojet's low fuel efficiency, and high noise. [ 28 ] Those that generate thrust with the addition of a ducted fan are called turbofans or (rarely) fan-jets. These engines produce nearly 80% of their thrust by the ducted fan, which can be seen from the front of the engine. They come in two types, low-bypass turbofan and high bypass , the difference being the amount of air moved by the fan, called "bypass air". These engines offer the benefit of more thrust without extra fuel consumption. [ 28 ] [ 29 ]
Gas turbines are also used in many liquid-fuel rockets , where gas turbines are used to power a turbopump to permit the use of lightweight, low-pressure tanks, reducing the empty weight of the rocket.
A turboprop engine is a turbine engine that drives an aircraft propeller using a reduction gear to translate high turbine section operating speed (often in the 10s of thousands) into low thousands necessary for efficient propeller operation. The benefit of using the turboprop engine is to take advantage of the turbine engines high power-to-weight ratio to drive a propeller, thus allowing a more powerful, but also smaller engine to be used. [ 29 ] Turboprop engines are used on a wide range of business aircraft such as the Pilatus PC-12 , commuter aircraft such as the Beechcraft 1900 , and small cargo aircraft such as the Cessna 208 Caravan or De Havilland Canada Dash 8 , and large aircraft (typically military) such as the Airbus A400M transport, Lockheed AC-130 and the 60-year-old Tupolev Tu-95 strategic bomber. While military turboprop engines can vary, in the civilian market there are two primary engines to be found: the Pratt & Whitney Canada PT6 , a free-turbine turboshaft engine, and the Honeywell TPE331 , a fixed turbine engine (formerly designated as the Garrett AiResearch 331).
Aeroderivative gas turbines are generally based on existing aircraft gas turbine engines and are smaller and lighter than industrial gas turbines. [ 44 ]
Aeroderivatives are used in electrical power generation due to their ability to be shut down and handle load changes more quickly than industrial machines. [ 45 ] They are also used in the marine industry to reduce weight. Common types include the General Electric LM2500 , General Electric LM6000 , and aeroderivative versions of the Pratt & Whitney PW4000 , Pratt & Whitney FT4 and Rolls-Royce RB211 . [ 44 ]
Increasing numbers of gas turbines are being used or even constructed by amateurs.
In its most straightforward form, these are commercial turbines acquired through military surplus or scrapyard sales, then operated for display as part of the hobby of engine collecting. [ 46 ] [ 47 ] In its most extreme form, amateurs have even rebuilt engines beyond professional repair and then used them to compete for the land speed record.
The simplest form of self-constructed gas turbine employs an automotive turbocharger as the core component. A combustion chamber is fabricated and plumbed between the compressor and turbine sections. [ 48 ]
More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft. [ 49 ] The Schreckling design [ 49 ] constructs the entire engine from raw materials, including the fabrication of a centrifugal compressor wheel from plywood, epoxy and wrapped carbon fibre strands.
Several small companies now manufacture small turbines and parts for the amateur. Most turbojet-powered model aircraft are now using these commercial and semi-commercial microturbines, rather than a Schreckling-like home-build. [ 50 ]
Small gas turbines are used as auxiliary power units (APUs) to supply auxiliary power to larger, mobile, machines such as an aircraft , and are a turboshaft design. [ 28 ] They supply:
Industrial gas turbines differ from aeronautical designs in that the frames, bearings, and blading are of heavier construction. They are also much more closely integrated with the devices they power—often an electric generator —and the secondary-energy equipment that is used to recover residual energy (largely heat).
They range in size from portable mobile plants to large, complex systems weighing more than a hundred tonnes housed in purpose-built buildings. When the gas turbine is used solely for shaft power, its thermal efficiency is about 30%. However, it may be cheaper to buy electricity than to generate it. Therefore, many engines are used in CHP (Combined Heat and Power) configurations that can be small enough to be integrated into portable container configurations.
Gas turbines can be particularly efficient when waste heat from the turbine is recovered by a heat recovery steam generator (HRSG) to power a conventional steam turbine in a combined cycle configuration. [ 51 ] The 605 MW General Electric 9HA achieved a 62.22% efficiency rate with temperatures as high as 1,540 °C (2,800 °F). [ 52 ] For 2018, GE offers its 826 MW HA at over 64% efficiency in combined cycle due to advances in additive manufacturing and combustion breakthroughs, up from 63.7% in 2017 orders and on track to achieve 65% by the early 2020s. [ 53 ] In March 2018, GE Power achieved a 63.08% gross efficiency for its 7HA turbine. [ 54 ]
Aeroderivative gas turbines can also be used in combined cycles, leading to a higher efficiency, but it will not be as high as a specifically designed industrial gas turbine. They can also be run in a cogeneration configuration: the exhaust is used for space or water heating, or drives an absorption chiller for cooling the inlet air and increase the power output, technology known as turbine inlet air cooling .
Another significant advantage is their ability to be turned on and off within minutes, supplying power during peak, or unscheduled, demand. Since single cycle (gas turbine only) power plants are less efficient than combined cycle plants, they are usually used as peaking power plants , which operate anywhere from several hours per day to a few dozen hours per year—depending on the electricity demand and the generating capacity of the region. In areas with a shortage of base-load and load following power plant capacity or with low fuel costs, a gas turbine powerplant may regularly operate most hours of the day. A large single-cycle gas turbine typically produces 100 to 400 megawatts of electric power and has 35–40% thermodynamic efficiency . [ 55 ]
Industrial gas turbines that are used solely for mechanical drive or used in collaboration with a recovery steam generator differ from power generating sets in that they are often smaller and feature a dual shaft design as opposed to a single shaft. The power range varies from 1 megawatt up to 50 megawatts. [ citation needed ] These engines are connected directly or via a gearbox to either a pump or compressor assembly. The majority of installations are used within the oil and gas industries. Mechanical drive applications increase efficiency by around 2%.
Oil and gas platforms require these engines to drive compressors to inject gas into the wells to force oil up via another bore, or to compress the gas for transportation. They are also often used to provide power for the platform. These platforms do not need to use the engine in collaboration with a CHP system due to getting the gas at an extremely reduced cost (often free from burn off gas). The same companies use pump sets to drive the fluids to land and across pipelines in various intervals.
One modern development seeks to improve efficiency in another way, by separating the compressor and the turbine with a compressed air store. In a conventional turbine, up to half the generated power is used driving the compressor. In a compressed air energy storage configuration, power is used to drive the compressor, and the compressed air is released to operate the turbine when required.
Turboshaft engines are used to drive compressors in gas pumping stations and natural gas liquefaction plants. They are also used in aviation to power all but the smallest modern helicopters, and function as an auxiliary power unit in large commercial aircraft. A primary shaft carries the compressor and its turbine which, together with a combustor, is called a Gas Generator . A separately spinning power-turbine is usually used to drive the rotor on helicopters. Allowing the gas generator and power turbine/rotor to spin at their own speeds allows more flexibility in their design.
Also known as miniature gas turbines or micro-jets.
With this in mind the pioneer of modern Micro-Jets, Kurt Schreckling , produced one of the world's first Micro-Turbines, the FD3/67. [ 49 ] This engine can produce up to 22 newtons of thrust, and can be built by most mechanically minded people with basic engineering tools, such as a metal lathe . [ 49 ]
Evolved from piston engine turbochargers , aircraft APUs or small jet engines , microturbines are 25 to 500 kilowatt turbines the size of a refrigerator .
Microturbines have around 15% efficiencies without a recuperator , 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in cogeneration . [ 56 ]
Most gas turbines are internal combustion engines but it is also possible to manufacture an external combustion gas turbine which is, effectively, a turbine version of a hot air engine .
Those systems are usually indicated as EFGT (Externally Fired Gas Turbine) or IFGT (Indirectly Fired Gas Turbine).
External combustion has been used for the purpose of using pulverized coal or finely ground biomass (such as sawdust) as a fuel. In the indirect system, a heat exchanger is used and only clean air with no combustion products travels through the power turbine. The thermal efficiency is lower in the indirect type of external combustion; however, the turbine blades are not subjected to combustion products and much lower quality (and therefore cheaper) fuels are able to be used.
When external combustion is used, it is possible to use exhaust air from the turbine as the primary combustion air. This effectively reduces global heat losses, although heat losses associated with the combustion exhaust remain inevitable.
Closed-cycle gas turbines based on helium or supercritical carbon dioxide also hold promise for use with future high temperature solar and nuclear power generation.
Gas turbines are often used on ships , locomotives , helicopters , tanks , and to a lesser extent, on cars, buses, and motorcycles.
A key advantage of jets and turboprops for airplane propulsion – their superior performance at high altitude compared to piston engines, particularly naturally aspirated ones – is irrelevant in most automobile applications. Their power-to-weight advantage, though less critical than for aircraft, is still important.
Gas turbines offer a high-powered engine in a very small and light package. However, they are not as responsive and efficient as small piston engines over the wide range of RPMs and powers needed in vehicle applications. In series hybrid vehicles, as the driving electric motors are mechanically detached from the electricity generating engine, the responsiveness, poor performance at low speed and low efficiency at low output problems are much less important. The turbine can be run at optimum speed for its power output, and batteries and ultracapacitors can supply power as needed, with the engine cycled on and off to run it only at high efficiency. The emergence of the continuously variable transmission may also alleviate the responsiveness problem.
Turbines have historically been more expensive to produce than piston engines, though this is partly because piston engines have been mass-produced in huge quantities for decades, while small gas turbine engines are rarities; however, turbines are mass-produced in the closely related form of the turbocharger .
The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine's exhaust gas . The centripetal turbine wheel drives a centrifugal compressor wheel through a common rotating shaft. This wheel supercharges the engine air intake to a degree that can be controlled by means of a wastegate or by dynamically modifying the turbine housing's geometry (as in a variable geometry turbocharger ).
It mainly serves as a power recovery device which converts a great deal of otherwise wasted thermal and kinetic energy into engine boost.
Turbo-compound engines (actually employed on some semi-trailer trucks ) are fitted with blow down turbines which are similar in design and appearance to a turbocharger except for the turbine shaft being mechanically or hydraulically connected to the engine's crankshaft instead of to a centrifugal compressor, thus providing additional power instead of boost. While the turbocharger is a pressure turbine, a power recovery turbine is a velocity one. [ citation needed ]
A number of experiments have been conducted with gas turbine powered automobiles , the largest by Chrysler . [ 57 ] [ 58 ] More recently, there has been some interest in the use of turbine engines for hybrid electric cars. For instance, a consortium led by micro gas turbine company Bladon Jets has secured investment from the Technology Strategy Board to develop an Ultra Lightweight Range Extender (ULRE) for next-generation electric vehicles. The objective of the consortium, which includes luxury car maker Jaguar Land Rover and leading electrical machine company SR Drives, is to produce the world's first commercially viable – and environmentally friendly – gas turbine generator designed specifically for automotive applications. [ 59 ]
The common turbocharger for gasoline or diesel engines is also a turbine derivative.
The first serious investigation of using a gas turbine in cars was in 1946 when two engineers, Robert Kafka and Robert Engerstein of Carney Associates, a New York engineering firm, came up with the concept where a unique compact turbine engine design would provide power for a rear wheel drive car. After an article appeared in Popular Science , there was no further work, beyond the paper stage. [ 60 ]
In 1950, designer F.R. Bell and Chief Engineer Maurice Wilks from British car manufacturers Rover unveiled the first car powered with a gas turbine engine. The two-seater JET1 had the engine positioned behind the seats, air intake grilles on either side of the car, and exhaust outlets on the top of the tail. During tests, the car reached top speeds of 140 km/h (87 mph), at a turbine speed of 50,000 rpm. After being shown in the United Kingdom and the United States in 1950, JET1 was further developed, and was subjected to speed trials on the Jabbeke highway in Belgium in June 1952, where it exceeded 240 km/h (150 mph). [ 61 ] The car ran on petrol , paraffin (kerosene) or diesel oil, but fuel consumption problems proved insurmountable for a production car. JET1 is on display at the London Science Museum .
A French turbine-powered car, the SOCEMA-Grégoire, was displayed at the October 1952 Paris Auto Show . It was designed by the French engineer Jean-Albert Grégoire . [ 62 ]
The first turbine-powered car built in the US was the GM Firebird I which began evaluations in 1953. While photos of the Firebird I may suggest that the jet turbine's thrust propelled the car like an aircraft, the turbine actually drove the rear wheels. The Firebird I was never meant as a commercial passenger car and was built solely for testing & evaluation as well as public relation purposes. [ 63 ] Additional Firebird concept cars, each powered by gas turbines, were developed for the 1953, 1956 and 1959 Motorama auto shows. The GM Research gas turbine engine also was fitted to a series of transit buses , starting with the Turbo-Cruiser I of 1953. [ 64 ]
Starting in 1954 with a modified Plymouth , [ 65 ] the American car manufacturer Chrysler demonstrated several prototype gas turbine -powered cars from the early 1950s through the early 1980s. Chrysler built fifty Chrysler Turbine Cars in 1963 and conducted the only consumer trial of gas turbine-powered cars. [ 66 ] Each of their turbines employed a unique rotating recuperator , referred to as a regenerator that increased efficiency. [ 65 ]
In 1954, Fiat unveiled a concept car with a turbine engine, called Fiat Turbina . This vehicle, looking like an aircraft with wheels, used a unique combination of both jet thrust and the engine driving the wheels. Speeds of 282 km/h (175 mph) were claimed. [ 67 ]
In the 1960s, Ford and GM also were developing gas turbine semi-trucks. Ford displayed the Big Red at the 1964 World's Fair . [ 68 ] With the trailer, it was 29 m (96 ft) long, 4.0 m (13 ft) high, and painted crimson red. It contained the Ford-developed gas turbine engine, with output power and torque of 450 kW (600 hp) and 1,160 N⋅m (855 lb⋅ft). The cab boasted a highway map of the continental U.S., a mini-kitchen, bathroom, and a TV for the co-driver. The fate of the truck was unknown for several decades, but it was rediscovered in early 2021 in private hands, having been restored to running order. [ 69 ] [ 70 ] The Chevrolet division of GM built the Turbo Titan series of concept trucks with turbine motors as analogs of the Firebird concepts, including Turbo Titan I ( c. 1959 , shares GT-304 engine with Firebird II), Turbo Titan II ( c. 1962 , shares GT-305 engine with Firebird III), and Turbo Titan III (1965, GT-309 engine); in addition, the GM Bison gas turbine truck was shown at the 1964 World's Fair. [ 71 ]
As a result of the U.S. Clean Air Act Amendments of 1970, research was funded into developing automotive gas turbine technology. [ 72 ] Design concepts and vehicles were conducted by Chrysler , General Motors , Ford (in collaboration with AiResearch ), and American Motors (in conjunction with Williams Research ). [ 73 ] Long-term tests were conducted to evaluate comparable cost efficiency. [ 74 ] Several AMC Hornets were powered by a small Williams regenerative gas turbine weighing 250 lb (113 kg) and producing 80 hp (60 kW; 81 PS) at 4450 rpm. [ 75 ] [ 76 ] [ 77 ]
In 1982, General Motors used an Oldsmobile Delta 88 powered by a gas turbine using pulverised coal dust. This was considered for the United States and the western world to reduce dependence on middle east oil at the time [ 78 ] [ 79 ] [ 80 ]
Toyota demonstrated several gas turbine powered concept cars, such as the Century gas turbine hybrid in 1975, the Sports 800 Gas Turbine Hybrid in 1979 and the GTV in 1985. No production vehicles were made. The GT24 engine was exhibited in 1977 without a vehicle.
In the early 1990s, Volvo introduced the Volvo ECC which was a gas turbine powered hybrid electric vehicle . [ 81 ]
In 1993, General Motors developed a gas turbine powered EV1 series hybrid —as a prototype of the General Motors EV1 . A Williams International 40 kW turbine drove an alternator which powered the battery–electric powertrain . The turbine design included a recuperator. In 2006, GM went into the EcoJet concept car project with Jay Leno .
At the 2010 Paris Motor Show Jaguar demonstrated its Jaguar C-X75 concept car. This electrically powered supercar has a top speed of 204 mph (328 km/h) and can go from 0 to 62 mph (0 to 100 km/h) in 3.4 seconds. It uses lithium-ion batteries to power four electric motors which combine to produce 780 bhp. It will travel 68 miles (109 km) on a single charge of the batteries, and uses a pair of Bladon Micro Gas Turbines to re-charge the batteries extending the range to 560 miles (900 km). [ 82 ]
The first race car (in concept only) fitted with a turbine was in 1955 by a US Air Force group as a hobby project with a turbine loaned them by Boeing and a race car owned by Firestone Tire & Rubber company. [ 83 ] The first race car fitted with a turbine for the goal of actual racing was by Rover and the BRM Formula One team joined forces to produce the Rover-BRM , a gas turbine powered coupe, which entered the 1963 24 Hours of Le Mans , driven by Graham Hill and Richie Ginther . It averaged 107.8 mph (173.5 km/h) and had a top speed of 142 mph (229 km/h). American Ray Heppenstall joined Howmet Corporation and McKee Engineering together to develop their own gas turbine sports car in 1968, the Howmet TX , which ran several American and European events, including two wins, and also participated in the 1968 24 Hours of Le Mans . The cars used Continental gas turbines, which eventually set six FIA land speed records for turbine-powered cars. [ 84 ]
For open wheel racing , 1967's revolutionary STP-Paxton Turbocar fielded by racing and entrepreneurial legend Andy Granatelli and driven by Parnelli Jones nearly won the Indianapolis 500 ; the Pratt & Whitney ST6B-62 powered turbine car was almost a lap ahead of the second place car when a gearbox bearing failed just three laps from the finish line. The next year the STP Lotus 56 turbine car won the Indianapolis 500 pole position even though new rules restricted the air intake dramatically. In 1971 Team Lotus principal Colin Chapman introduced the Lotus 56B F1 car, powered by a Pratt & Whitney STN 6/76 gas turbine. Chapman had a reputation of building radical championship-winning cars, but had to abandon the project because there were too many problems with turbo lag .
General Motors fitted the GT-30x series of gas turbines (branded "Whirlfire") to several prototype buses in the 1950s and 1960s, including Turbo-Cruiser I (1953, GT-300); Turbo-Cruiser II (1964, GT-309); Turbo-Cruiser III (1968, GT-309); RTX (1968, GT-309); and RTS 3T (1972). [ 85 ]
The arrival of the Capstone Turbine has led to several hybrid bus designs, starting with HEV-1 by AVS of Chattanooga, Tennessee in 1999, and closely followed by Ebus and ISE Research in California, and DesignLine Corporation in New Zealand (and later the United States). AVS turbine hybrids were plagued with reliability and quality control problems, resulting in liquidation of AVS in 2003. The most successful design by Designline is now operated in 5 cities in 6 countries, with over 30 buses in operation worldwide, and order for several hundred being delivered to Baltimore, and New York City.
Brescia Italy is using serial hybrid buses powered by microturbines on routes through the historical sections of the city. [ 86 ]
The MTT Turbine Superbike appeared in 2000 (hence the designation of Y2K Superbike by MTT) and is the first production motorcycle powered by a turbine engine – specifically, a Rolls-Royce Allison model 250 turboshaft engine, producing about 283 kW (380 bhp). Speed-tested to 365 km/h or 227 mph (according to some stories, the testing team ran out of road during the test), it holds the Guinness World Record for most powerful production motorcycle and most expensive production motorcycle, with a price tag of US$185,000.
Several locomotive classes have been powered by gas turbines, the most recent incarnation being Bombardier 's JetTrain .
The Third Reich Wehrmacht Heer 's development division, the Heereswaffenamt (Army Ordnance Board), studied a number of gas turbine engine designs for use in tanks starting in mid-1944. The first gas turbine engine design intended for use in armored fighting vehicle propulsion, the BMW 003 -based GT 101 , was meant for installation in the Panther tank . [ 87 ] Towards the end of the war, a Jagdtiger was fitted with one of the aforementioned gas turbines. [ 88 ]
The second use of a gas turbine in an armored fighting vehicle was in 1954 when a unit, PU2979, specifically developed for tanks by C. A. Parsons and Company , was installed and trialed in a British Conqueror tank . [ 89 ] The Stridsvagn 103 was developed in the 1950s and was the first mass-produced main battle tank to use a turbine engine, the Boeing T50 . Since then, gas turbine engines have been used as auxiliary power units in some tanks and as main powerplants in Soviet/Russian T-80s and U.S. M1 Abrams tanks, among others. They are lighter and smaller than diesel engines at the same sustained power output but the models installed to date are less fuel efficient than the equivalent diesel, especially at idle, requiring more fuel to achieve the same combat range. Successive models of M1 have addressed this problem with battery packs or secondary generators to power the tank's systems while stationary, saving fuel by reducing the need to idle the main turbine. T-80s can mount three large external fuel drums to extend their range. Russia has stopped production of the T-80 in favor of the diesel-powered T-90 (based on the T-72 ), while Ukraine has developed the diesel-powered T-80UD and T-84 with nearly the power of the gas-turbine tank. The French Leclerc tank 's diesel powerplant features the "Hyperbar" hybrid supercharging system, where the engine's turbocharger is completely replaced with a small gas turbine which also works as an assisted diesel exhaust turbocharger, enabling engine RPM-independent boost level control and a higher peak boost pressure to be reached (than with ordinary turbochargers). This system allows a smaller displacement and lighter engine to be used as the tank's power plant and effectively removes turbo lag . This special gas turbine/turbocharger can also work independently from the main engine as an ordinary APU.
A turbine is theoretically more reliable and easier to maintain than a piston engine since it has a simpler construction with fewer moving parts, but in practice, turbine parts experience a higher wear rate due to their higher working speeds. The turbine blades are highly sensitive to dust and fine sand so that in desert operations air filters have to be fitted and changed several times daily. An improperly fitted filter, or a bullet or shell fragment that punctures the filter, can damage the engine. Piston engines (especially if turbocharged) also need well-maintained filters, but they are more resilient if the filter does fail.
Like most modern diesel engines used in tanks, gas turbines are usually multi-fuel engines.
Gas turbines are used in many naval vessels , where they are valued for their high power-to-weight ratio and their ships' resulting acceleration and ability to get underway quickly.
The first gas-turbine-powered naval vessel was the Royal Navy 's motor gunboat MGB 2009 (formerly MGB 509 ) converted in 1947. Metropolitan-Vickers fitted their F2/3 jet engine with a power turbine. The Steam Gun Boat Grey Goose was converted to Rolls-Royce gas turbines in 1952 and operated as such from 1953. [ 90 ] The Bold class Fast Patrol Boats Bold Pioneer and Bold Pathfinder built in 1953 were the first ships created specifically for gas turbine propulsion. [ 91 ]
The first large-scale, partially gas-turbine powered ships were the Royal Navy's Type 81 (Tribal class) frigates with combined steam and gas powerplants. The first, HMS Ashanti was commissioned in 1961.
The German Navy launched the first Köln -class frigate in 1961 with 2 Brown, Boveri & Cie gas turbines in the world's first combined diesel and gas propulsion system.
The Soviet Navy commissioned in 1962 the first of 25 Kashin -class destroyer with 4 gas turbines in combined gas and gas propulsion system. Those vessels used 4 M8E gas turbines, which generated 54,000–72,000 kW (72,000–96,000 hp). Those ships were the first large ships in the world to be powered solely by gas turbines.
The Danish Navy had 6 Søløven -class torpedo boats (the export version of the British Brave class fast patrol boat ) in service from 1965 to 1990, which had 3 Bristol Proteus (later RR Proteus) Marine Gas Turbines rated at 9,510 kW (12,750 shp) combined, plus two General Motors Diesel engines, rated at 340 kW (460 shp), for better fuel economy at slower speeds. [ 92 ] And they also produced 10 Willemoes Class Torpedo / Guided Missile boats (in service from 1974 to 2000) which had 3 Rolls-Royce Marine Proteus Gas Turbines also rated at 9,510 kW (12,750 shp), same as the Søløven-class boats, and 2 General Motors Diesel Engines, rated at 600 kW (800 shp), also for improved fuel economy at slow speeds. [ 93 ]
The Swedish Navy produced 6 Spica-class torpedo boats between 1966 and 1967 powered by 3 Bristol Siddeley Proteus 1282 turbines , each delivering 3,210 kW (4,300 shp). They were later joined by 12 upgraded Norrköping class ships, still with the same engines. With their aft torpedo tubes replaced by antishipping missiles they served as missile boats until the last was retired in 2005. [ 94 ]
The Finnish Navy commissioned two Turunmaa -class corvettes , Turunmaa and Karjala , in 1968. They were equipped with one 16,410 kW (22,000 shp) Rolls-Royce Olympus TM1 gas turbine and three Wärtsilä marine diesels for slower speeds. They were the fastest vessels in the Finnish Navy; they regularly achieved speeds of 35 knots, and 37.3 knots during sea trials. The Turunmaa s were decommissioned in 2002. Karjala is today a museum ship in Turku , and Turunmaa serves as a floating machine shop and training ship for Satakunta Polytechnical College.
The next series of major naval vessels were the four Canadian Iroquois -class helicopter carrying destroyers first commissioned in 1972. They used 2 ft-4 main propulsion engines, 2 ft-12 cruise engines and 3 Solar Saturn 750 kW generators.
The first U.S. gas-turbine powered ship was the U.S. Coast Guard's Point Thatcher , a cutter commissioned in 1961 that was powered by two 750 kW (1,000 shp) turbines utilizing controllable-pitch propellers. [ 95 ] The larger Hamilton -class High Endurance Cutters , was the first class of larger cutters to utilize gas turbines, the first of which ( USCGC Hamilton ) was commissioned in 1967. Since then, they have powered the U.S. Navy's Oliver Hazard Perry -class frigates , Spruance and Arleigh Burke -class destroyers, and Ticonderoga -class guided missile cruisers . USS Makin Island , a modified Wasp -class amphibious assault ship , is to be the Navy's first amphibious assault ship powered by gas turbines.
The marine gas turbine operates in a more corrosive atmosphere due to the presence of sea salt in air and fuel and use of cheaper fuels.
Up to the late 1940s, much of the progress on marine gas turbines all over the world took place in design offices and engine builder's workshops and development work was led by the British Royal Navy and other Navies. While interest in the gas turbine for marine purposes, both naval and mercantile, continued to increase, the lack of availability of the results of operating experience on early gas turbine projects limited the number of new ventures on seagoing commercial vessels being embarked upon.
In 1951, the diesel–electric oil tanker Auris , 12,290 deadweight tonnage (DWT) was used to obtain operating experience with a main propulsion gas turbine under service conditions at sea and so became the first ocean-going merchant ship to be powered by a gas turbine. Built by Hawthorn Leslie at Hebburn-on-Tyne , UK, in accordance with plans and specifications drawn up by the Anglo-Saxon Petroleum Company and launched on the UK's Princess Elizabeth 's 21st birthday in 1947, the ship was designed with an engine room layout that would allow for the experimental use of heavy fuel in one of its high-speed engines, as well as the future substitution of one of its diesel engines by a gas turbine. [ 96 ] The Auris operated commercially as a tanker for three-and-a-half years with a diesel–electric propulsion unit as originally commissioned, but in 1951 one of its four 824 kW (1,105 bhp) diesel engines – which were known as "Faith", "Hope", "Charity" and "Prudence" – was replaced by the world's first marine gas turbine engine, a 890 kW (1,200 bhp) open-cycle gas turbo-alternator built by British Thompson-Houston Company in Rugby . Following successful sea trials off the Northumbrian coast, the Auris set sail from Hebburn-on-Tyne in October 1951 bound for Port Arthur in the US and then Curaçao in the southern Caribbean returning to Avonmouth after 44 days at sea, successfully completing her historic trans-Atlantic crossing. During this time at sea the gas turbine burnt diesel fuel and operated without an involuntary stop or mechanical difficulty of any kind. She subsequently visited Swansea, Hull, Rotterdam , Oslo and Southampton covering a total of 13,211 nautical miles. The Auris then had all of its power plants replaced with a 3,910 kW (5,250 shp) directly coupled gas turbine to become the first civilian ship to operate solely on gas turbine power.
Despite the success of this early experimental voyage the gas turbine did not replace the diesel engine as the propulsion plant for large merchant ships. At constant cruising speeds the diesel engine simply had no peer in the vital area of fuel economy. The gas turbine did have more success in Royal Navy ships and the other naval fleets of the world where sudden and rapid changes of speed are required by warships in action. [ 97 ]
The United States Maritime Commission were looking for options to update WWII Liberty ships , and heavy-duty gas turbines were one of those selected. In 1956 the John Sergeant was lengthened and equipped with a General Electric 4,900 kW (6,600 shp) HD gas turbine with exhaust-gas regeneration, reduction gearing and a variable-pitch propeller . It operated for 9,700 hours using residual fuel ( Bunker C ) for 7,000 hours. Fuel efficiency was on a par with steam propulsion at 0.318 kg/kW (0.523 lb/hp) per hour, [ 98 ] and power output was higher than expected at 5,603 kW (7,514 shp) due to the ambient temperature of the North Sea route being lower than the design temperature of the gas turbine. This gave the ship a speed capability of 18 knots, up from 11 knots with the original power plant, and well in excess of the 15 knot targeted. The ship made its first transatlantic crossing with an average speed of 16.8 knots, in spite of some rough weather along the way. Suitable Bunker C fuel was only available at limited ports because the quality of the fuel was of a critical nature. The fuel oil also had to be treated on board to reduce contaminants and this was a labor-intensive process that was not suitable for automation at the time. Ultimately, the variable-pitch propeller, which was of a new and untested design, ended the trial, as three consecutive annual inspections revealed stress-cracking. This did not reflect poorly on the marine-propulsion gas-turbine concept though, and the trial was a success overall. The success of this trial opened the way for more development by GE on the use of HD gas turbines for marine use with heavy fuels. [ 99 ] The John Sergeant was scrapped in 1972 at Portsmouth PA.
Boeing launched its first passenger-carrying waterjet -propelled hydrofoil Boeing 929 , in April 1974. Those ships were powered by two Allison 501 -KF gas turbines. [ 100 ]
Between 1971 and 1981, Seatrain Lines operated a scheduled container service between ports on the eastern seaboard of the United States and ports in northwest Europe across the North Atlantic with four container ships of 26,000 tonnes DWT. Those ships were powered by twin Pratt & Whitney gas turbines of the FT 4 series. The four ships in the class were named Euroliner , Eurofreighter , Asialiner and Asiafreighter . Following the dramatic Organization of the Petroleum Exporting Countries (OPEC) price increases of the mid-1970s, operations were constrained by rising fuel costs. Some modification of the engine systems on those ships was undertaken to permit the burning of a lower grade of fuel (i.e., marine diesel ). Reduction of fuel costs was successful using a different untested fuel in a marine gas turbine but maintenance costs increased with the fuel change. After 1981 the ships were sold and refitted with, what at the time, was more economical diesel-fueled engines but the increased engine size reduced cargo space. [ citation needed ]
The first passenger ferry to use a gas turbine was the GTS Finnjet , built in 1977 and powered by two Pratt & Whitney FT 4C-1 DLF turbines, generating 55,000 kW (74,000 shp) and propelling the ship to a speed of 31 knots. However, the Finnjet also illustrated the shortcomings of gas turbine propulsion in commercial craft, as high fuel prices made operating her unprofitable. After four years of service, additional diesel engines were installed on the ship to reduce running costs during the off-season. The Finnjet was also the first ship with a combined diesel–electric and gas propulsion. Another example of commercial use of gas turbines in a passenger ship is Stena Line 's HSS class fastcraft ferries. HSS 1500-class Stena Explorer , Stena Voyager and Stena Discovery vessels use combined gas and gas setups of twin GE LM2500 plus GE LM1600 power for a total of 68,000 kW (91,000 shp). The slightly smaller HSS 900-class Stena Carisma , uses twin ABB – STAL GT35 turbines rated at 34,000 kW (46,000 shp) gross. The Stena Discovery was withdrawn from service in 2007, another victim of too high fuel costs. [ citation needed ]
In July 2000, the Millennium became the first cruise ship to be powered by both gas and steam turbines. The ship featured two General Electric LM2500 gas turbine generators whose exhaust heat was used to operate a steam turbine generator in a COGES (combined gas electric and steam) configuration. Propulsion was provided by two electrically driven Rolls-Royce Mermaid azimuth pods. The liner RMS Queen Mary 2 uses a combined diesel and gas configuration. [ 101 ]
In marine racing applications the 2010 C5000 Mystic catamaran Miss GEICO uses two Lycoming T-55 turbines for its power system. [ citation needed ]
Gas turbine technology has steadily advanced since its inception and continues to evolve. Development is actively producing both smaller gas turbines and more powerful and efficient engines. Aiding in these advances are computer-based design (specifically computational fluid dynamics and finite element analysis ) and the development of advanced materials: Base materials with superior high-temperature strength (e.g., single-crystal superalloys that exhibit yield strength anomaly ) or thermal barrier coatings that protect the structural material from ever-higher temperatures. These advances allow higher compression ratios and turbine inlet temperatures, more efficient combustion and better cooling of engine parts.
Computational fluid dynamics (CFD) has contributed to substantial improvements in the performance and efficiency of gas turbine engine components through enhanced understanding of the complex viscous flow and heat transfer phenomena involved. For this reason, CFD is one of the key computational tools used in design and development of gas [ 102 ] [ 103 ] turbine engines.
The simple-cycle efficiencies of early gas turbines were practically doubled by incorporating inter-cooling, regeneration (or recuperation), and reheating. These improvements, of course, come at the expense of increased initial and operation costs, and they cannot be justified unless the decrease in fuel costs offsets the increase in other costs. The relatively low fuel prices, the general desire in the industry to minimize installation costs, and the tremendous increase in the simple-cycle efficiency to about 40 percent left little desire for opting for these modifications. [ 104 ]
On the emissions side, the challenge is to increase turbine inlet temperatures while at the same time reducing peak flame temperature in order to achieve lower NOx emissions and meet the latest emission regulations. In May 2011, Mitsubishi Heavy Industries achieved a turbine inlet temperature of 1,600 °C (2,900 °F) on a 320 megawatt gas turbine, and 460 MW in gas turbine combined-cycle power generation applications in which gross thermal efficiency exceeds 60%. [ 105 ] [ 106 ]
Compliant foil bearings were commercially introduced to gas turbines in the 1990s. These can withstand over a hundred thousand start/stop cycles and have eliminated the need for an oil system. The application of microelectronics and power switching technology have enabled the development of commercially viable electricity generation by microturbines for distribution and vehicle propulsion.
In 2013, General Electric started the development of the GE9X with a compression ratio of 61:1. [ 107 ]
The following are advantages and disadvantages of gas-turbine engines: [ 108 ]
Advantages include:
Disadvantages include:
British, German, other national and international test codes are used to standardize the procedures and definitions used to test gas turbines. Selection of the test code to be used is an agreement between the purchaser and the manufacturer, and has some significance to the design of the turbine and associated systems. In the United States, ASME has produced several performance test codes on gas turbines. This includes ASME PTC 22–2014. These ASME performance test codes have gained international recognition and acceptance for testing gas turbines. The single most important and differentiating characteristic of ASME performance test codes, including PTC 22, is that the test uncertainty of the measurement indicates the quality of the test and is not to be used as a commercial tolerance. | https://en.wikipedia.org/wiki/Gas_turbine |
Gas vesicles , also known as gas vacuoles , are nanocompartments in certain prokaryotic organisms, which help in buoyancy. [ 1 ] Gas vesicles are composed entirely of protein ; no lipids or carbohydrates have been detected.
Gas vesicles occur primarily in aquatic organisms as they are used to modulate the cell's buoyancy and modify the cell's position in the water column so it can be optimally located for photosynthesis or move to locations with more or less oxygen. [ 1 ] Organisms that could float to the air–liquid interface out competes other aerobes that cannot rise in a water column, through using up oxygen in the top layer.
In addition, gas vesicles can be used to maintain optimum salinity by positioning the organism in specific locations in a stratified body of water to prevent osmotic shock . [ 2 ] High concentrations of solute will cause water to be drawn out of the cell by osmosis , causing cell lysis. The ability to synthesize gas vesicles is one of many strategies that allow halophilic organisms to tolerate environments with high salt content.
Gas vesicles are likely one of the most early mechanisms of motility among microscopic organisms due to the fact that it is the most widespread form of motility conserved within the genome of prokaryotes, some of which have evolved about 3 billion years ago. [ 3 ] [ 4 ] Modes of active motility such as flagella movement require a mechanism that could convert chemical energy into mechanical energy, and thus is much more complex and would have evolved later. Functions of the gas vesicles are also largely conserved among species, although the mode of regulation might differ, suggesting the importance of gas vesicles as a form of motility. In certain organism such as enterobacterium Serratia sp. flagella-based motility and gas vesicle production are regulated oppositely by a single RNA binding protein, RsmA, suggesting alternate modes of environmental adaptation which would have developed into different taxons through regulation of the development between motility and flotation. [ 5 ]
Although there is evidence suggesting the early evolution of gas vesicles, plasmid transfer serves as an alternate explanation of the widespread and conserved nature of the organelle. [ 4 ] Cleavage of a plasmid in Halobacterium halobium resulted in the loss of the ability to biosynthesize gas vesicles, indicating the possibility of horizontal gene transfer , which could result in a transfer of the ability to produce gas vesicles among different strains of bacteria. [ 6 ]
Gas vesicles are generally lemon-shaped or cylindrical, hollow tubes of protein with conical caps on both ends. The vesicles vary most in their diameter. Larger vesicles can hold more air and use less protein making them the most economic in terms of resource use, however, the larger a vesicle is the structurally weaker it is under pressure and the less pressure required before the vesicle would collapse. Organisms have evolved to be the most efficient with protein use and use the largest maximum vesicle diameter that will withstand the pressure the organism could be exposed to. In order for natural selection to have affected gas vesicles, the vesicles' diameter must be controlled by genetics.
Although genes encoding gas vesicles are found in many species of haloarchaea , only a few species produce them. The first Haloarchaeal gas vesicle gene, GvpA was cloned from Halobacterium sp. NRC-1. [ 7 ] 14 genes are involved in forming gas vesicles in haloarchaea. [ 8 ]
The first gas vesicle gene, GvpA was identified in Calothrix. [ 9 ] There are at least two proteins that compose a cyanobacterium's gas vesicle: GvpA, and GvpC. GvpA forms ribs and much of the mass (up to 90%) of the main structure. GvpA is strongly hydrophobic and may be one of the most hydrophobic proteins known. GvpC is hydrophilic and helps to stabilize the structure by periodic inclusions into the GvpA ribs. GvpC is capable of being washed out of the vesicle and a consequential decreases in the vesicle's strength. The thickness of the vesicle's wall may range from 1.8 to 2.8 nm. The ribbed structure of the vesicle is evident on both inner and outer surfaces with a spacing of 4–5 nm between ribs. Vesicles may be 100–1400 nm long and 45–120 nm in diameter.
Within a species gas vesicle sizes are relatively uniform with a standard deviation of ±4%.
It appears that gas vesicles begin their existence as small biconical (two cones with the flat bases joined) structures which enlarge to the specific diameter than grow and expand their length. It is unknown exactly what controls the diameter but it may be a molecule that interferes with GvpA or the shape of GvpA may change.
Formation of gas vesicles are regulated by two Gvp proteins: GvpD, which represses the expression of GvpA and GvpC proteins, and GvpE, which induces expression. [ 10 ] Extracellular environmental factors also affect vesicle formation, either by regulating Gvp protein production or by directly disturbing the vesicle structure. [ 8 ] [ 11 ]
Light intensity has been found to affect gas vesicles production and maintenance differently between different bacteria and archaea. For Anabaena flos-aquae , higher light intensities leads to vesicle collapse from an increase in turgor pressure and greater accumulation of photosynthetic products. In cyanobacteria, vesicle production decreases at high light intensity due to exposure of the bacterial surface to UV radiation, which can damage the bacterial genome. [ 11 ]
Accumulation of glucose, maltose, or sucrose in Haloferax mediterranei and Haloferax volcanii were found to inhibit the expression of GvpA proteins and, therefore, a decrease of gas vesicle production. However, this only occurred at the cell's early exponential growth phase. Vesicle formation could also be induced in decreasing extracellular glucose concentrations. [ 12 ]
A lack of oxygen was found to negatively affect gas vesicle formation in halophilic archaea. Halobacterium salinarum produce little or no vesicles under anaerobic conditions due to reduced synthesis of mRNA transcripts encoding for Gvp proteins. H. mediterranei and H. volcanii do not produce any vesicles under anoxic conditions due to a decrease in synthesized transcripts encoding for GvpA and truncated transcripts expressing GvpD. [ 12 ]
Increased extracellular pH levels have been found to increase vesicle formation in Microcytis species. Under increased pH, levels of gvpA and gvpC transcripts increase, allowing more exposure to ribosomes for expression and leading to upregulation of Gvp proteins. It may be attributed to greater transcription of these genes, decreased decay of the synthesized transcripts or the higher stability of the mRNA. [ 13 ]
Ultrasonic irradiation, at certain frequencies, was found to collapse gas vesicles in cyanobacteria Spirulina platensis , preventing them from blooming. [ 14 ]
In enterobacterium; Serratia sp. strain ATCC39006 , gas vesicle is produced only when there is sufficient concentration of a signalling molecule, N-acyl homoserine lactone. In this case, the quorum sensing molecule, N-acyl homoserine lactone acts as a morphogen initiating organelle development. [ 5 ] This is advantageous to the organism as resources for gas vesicle production are utilized only when there is oxygen limitation caused by an increase in bacterial population.
Gas vesicle gene gvp C from Halobacterium sp. is used as delivery system for vaccine studies.
Several characteristics of the protein encoded by the gas vesicle gene gvp C allow it to be used as carrier and adjuvant for antigens: it is stable, resistant to biological degradation, tolerates relatively high temperatures (up to 50 °C), and non-pathogenic to humans. [ 15 ] Several antigens from various human pathogens have been recombined into the gvp C gene to create subunit vaccines with long-lasting immunologic responses. [ 16 ]
Different genomic segments encoding for several Chlamydia trachomatis pathogen's proteins, including MOMP, OmcB, and PompD, are joined to the gvp C gene of Halobacteria . In vitro assessments of cells show expression of the Chlamydia genes on cell surfaces through imaging techniques and show characteristic immunologic responses such as TLRs activities and pro-inflammatory cytokines production. [ 17 ] Gas vesicle gene can be exploited as a delivery vehicle to generate a potential vaccine for Chlamydia. Limitations of this method include the need to minimize the damage of the GvpC protein itself while including as much of the vaccine target gene into the gvp C gene segment. [ 17 ]
A similar experiment uses the same gas vesicle gene and Salmonella enterica pathogen's secreted inosine phosphate effector protein SopB4 and SopB5 to generate a potential vaccine vector. Immunized mice secrete pro-inflammatory cytokines IFN-γ, IL-2, and IL-9. Antibody IgG is also detected. After an infection challenge, none or significantly less amount of bacteria were found in the harvested organs such as the spleen and the liver. Potential vaccines using gas vesicle as an antigen display can be given via the mucosal route as an alternative administration pathway, increasing its accessibility to more people and eliciting a wider range of immune responses within the body. [ 15 ]
Gas vesicles have several physical properties that make them visible on various medical imaging modalities. [ 18 ] The ability of gas vesicle to scatter light has been used for decades for estimating their concentration and measuring their collapse pressure . The optical contrast of gas vesicles also enables them to serve as contrast agents in optical coherence tomography , with applications in ophthalmology . [ 19 ] The difference in acoustic impedance between the gas in their cores and the surrounding fluid gives gas vesicles robust acoustic contrast. [ 20 ] Moreover, the ability of some gas vesicle shells to buckle generates harmonic ultrasound echoes that improves the contrast to tissue ratio. [ 21 ] Finally, gas vesicles can be used as contrast agents for magnetic resonance imaging (MRI), relying on the difference between the magnetic susceptibility of air and water. [ 22 ] The ability to non-invasively collapse gas vesicles using pressure waves provides a mechanism for erasing their signal and improving their contrast. Subtracting the images before and after acoustic collapse can eliminate background signals enhancing the detection of gas vesicles.
Heterologous expression of gas vesicles in bacterial [ 23 ] and mammalian [ 24 ] cells enabled their use as the first family of acoustic reporter genes . [ 25 ] While fluorescent reporter genes like green fluorescent protein (GFP) had widespread use in biology, their in vivo applications are limited by the penetration depth of light in tissue, typically a few mm. Luminescence can be detected deeper within the tissue, but have a low spatial resolution. Acoustic reporter genes provide sub-millimeter spatial resolution and a penetration depth of several centimeters, enabling the in vivo study of biological processes deep within the tissue. | https://en.wikipedia.org/wiki/Gas_vesicle |
Gas well deliquification , also referred to as "gas well dewatering", is the general term for technologies used to remove water or condensates build-up from producing gas wells .
When natural gas flows to the surface in a producing gas well, the gas carries liquids to the surface if the velocity of the gas is high enough. A high gas velocity results in a mist flow pattern in which liquids are finely dispersed in the gas. Consequently, a low volume of liquid is present in the tubing or production conduit, resulting in a pressure drop caused by gravity acting on the flowing fluids. As the gas velocity in the production tubing drops with time, the velocity of the liquids carried by the gas declines even faster. Flow patterns of liquids on the walls of the conduit cause liquid to accumulate in the bottom of the well, which can either slow or stop gas production altogether.
Possible solutions to this problem include the installation of a velocity string, a capillary string injecting foamers (often with corrosive effects on surface wellhead seals), or a pump to continuously or intermittently pump the water to the surface to remove the hydrostatic barrier that the water creates. A common practice is to use a device called a plunger to lift the liquids. Improved electrical pumps coming onto the market may enhance the effectiveness of the technology. More recently, downhole compressors are being used to increase velocity of gas flow, which in turn accelerates liquid unloading. [ 1 ]
The same concept is also applicable to oil wells when they are at the end stage of production. In this case, the reservoir pressure drops to such a low level that it cannot lift the weight of the oil/water column to the surface. By injecting a gas (such as nitrogen) into the wellbore at a specific point, the density of the fluid column can be reduced to the point that the reservoir pressure is once again able to lift fluids to the surface. | https://en.wikipedia.org/wiki/Gas_well_deliquification |
The gaseous detection device ( GDD ) is a method and apparatus for the detection of signals in the gaseous environment of an environmental scanning electron microscope (ESEM) and all scanned beam type of instruments that allow a minimum gas pressure for the detector to operate.
In the course of development of the ESEM , the detectors previously employed in the vacuum of a scanning electron microscope (SEM) had to be adapted for operation in gaseous conditions. The backscattered electron (BSE) detector was adapted by an appropriate geometry in accordance with the requirements for optimum electron beam transmission, BSE distribution and light guide transmission. [ 1 ] However, the corresponding secondary electron (SE) detector ( Everhart–Thornley detector ) could not be adapted, because the high potential required would cause a catastrophic breakdown even with moderate increase of pressure, such as low vacuum. Danilatos (1983) [ 2 ] [ 3 ] overcame this problem by using the environmental gas itself as the detector, by virtue of the ionizing action of various signals. With appropriate control of electrode configuration and bias, detection of SE was achieved. A comprehensive survey dealing with the theory and operation of GDD has been published, [ 4 ] from which the majority of the material presented below has been used.
The GDD is in principle an adaptation of techniques for particle detection used in nuclear physics and astronomy. The adaptation involves the parameters required for the formation of images in the conditions of an electron microscope and in the presence of gas inside the specimen chamber. The signals emanating from the beam specimen-interaction, in turn, interact with the surrounding gas in the form of gaseous ionization and excitation. The type, intensity and distribution of signal-gas interactions vary. It is fortunate that generally the time-constant of these interactions is compatible with the time-constant required for the formation of images in the ESEM. The establishment of this compatibility constitutes the basis of the invention of GDD and the leap from particle physics to electron microscopy. The dominant signal-gas interactions are those by the BSE and SE, as they are outlined below.
In its simplest form, the GDD involves one or more electrodes biased with a generally low voltage (e.g. up to 20 V), which is sufficient to collect the ionization current created by whatever sources. This is much the same as an ionization chamber in particle physics. The size and location of these electrodes determine the detection volume in the gas and hence the type of signal detected. The energetic BSE traverse a long distance, whereas the SE travel a much shorter lateral distance mainly by way of diffusion in the gas. Correspondingly, an electrode placed further away from the beam axis will have a predominantly BSE component in comparison to the predominant SE component collected by an electrode placed close to the axis. The precise proportion of signal mix and intensity depends on the additional parameters of gas nature and pressure in conjunction with electrode configurations and bias, bearing in mind that there is no abrupt physical distinction between SE and BSE, apart from the conventional definition of the 50 eV boundary between them.
In another form, the GDD involves one or more electrodes as above but biased with a generally high voltage (e.g. 20–500 V). The processes involved are the same as in the low voltage case with the addition of an amplification of signal along the principle of a proportional amplifier as used in particle physics. That is, all slow electrons in the gas emanating either from the ionizing BSE or directly from the specimen (i.e. the SE) are multiplied in an avalanche form. The energy imparted on the traveling slow electrons by the external electrode field is sufficient to ionize the gas molecules through successive (cascade) collisions. The discharge is controlled in proportion by the applied electrode bias below the breakdown point. This form of detection is referred as ionization-GDD. [ 4 ]
Parallel to the ionization, there is also excitation of the gas in both cases above. The gaseous photons are produced both by BSE and SE both directly and by cascade avalanche with the ionization electrons. These photons are detected by appropriate means, like photo-multipliers. By positioning Light tubes strategically, using filters and other light optics means, the SE can again be separated from the BSE and corresponding images formed. This form of detection is referred as scintillation-GDD. [ 4 ]
The principles outlined above are best described by considering plane electrodes biased to form a uniform electric field, such as shown in the accompanying diagram of GDD-principle . The electron beam striking the specimen at the cathode effectively creates a point source of SE and BSE. The distribution of slow electrons emitted from a point source inside a gas acted upon by a uniform field is given from the equations (low field): [ 5 ]
where R is the fraction of SE that arrives at the anode inside radius r , V the potential difference between the electrodes placed at distance d , k is the Boltzmann constant, T the absolute gas temperature, e the elementary charge and ε is the ratio of the thermal (agitation and kinetic) energy of the electrons divided by the thermal energy of the host gas; I is the corresponding current collected by the anode inside r , δ is the SE yield coefficient and I b the incident electron beam current. This provides the spatial distribution of the initial electrons SE as they are acted upon by the uniform electric field that moves them from the cathode to the anode, while the electrons also diffuse away due to thermal collisions with the gas molecules. Plots are provided in the accompanying efficiency characteristics of the GDD , for a set of operating conditions of pressure p and distance d . We note that a 100% collection efficiency is fast approached within a small radius even at moderate field strength. At high bias, a nearly complete collection is achieved within a very small radius, a fact that has favorable design implications.
The above radial distribution is valid also in the presence of formation of electron avalanches at high electric field, but it must be multiplied by an appropriate gain factor. In its simplest form for parallel electrodes, [ 6 ] the gain factor is the exponential in the current equation:
where α is the first Townsend coefficient . This gives the total signal amplification due to both electrons and ions. The spatial charge distribution and gain factor varies with electrode configuration and geometry and by additional discharge processes described in the referenced theory of the GDD.
The BSE usually have energies in the kV range so that the much lower electrode bias has only a secondary effect on their trajectory. For the same reason, the finite number of collisions with the gas also results in a second order deflection from their trajectory they would have in vacuum. Therefore, their distribution is practically the same as has been worked out by SEM workers, the variation of which depends on the specimen surface properties (geometry and material composition). For a polished specimen surface the BSE distribution assumes a nearly cosine function but for a rough surface we may take it to be spherical (i.e. uniform in all directions). [ 7 ] For brevity, the equations of the second case only are given below. In vacuum, the current distribution from BSE on the electrode is given by
where η is the BSE yield coefficient.
In the presence of gas at low electric field the corresponding equations become:
where S is the ionization coefficient of the gas and p its pressure.
Finally, for a high electric field we get
For practical purposes, the BSE predominantly fall outside the volume acted upon by predominantly the SE, while there is an intermediate volume of comparable fraction of the two signals. The interplay of the various parameters involved has been studied in the main, but it also constitutes a new field for further research and development, especially as we move outside the plane electrode geometry.
Prior to practical implementations, it is helpful to consider a more esoteric aspect (principle), namely, the fundamental physical process taking place in the GDD. The signal in the external circuit is a displacement current i created by induction of charge on the electrodes by a moving charge e with velocity υ in the space between them:
At the point in time when the charge arrives at the electrode, there is no current flowing in the circuit since υ = 0, only when the charge is in motion between the electrodes do we have a signal current. This is important in the case, for example, when a new electron-ion pair is generated at any point in the space between anode-cathode, say at x distance from the anode. Then, only a fraction ex / d of charge is induced by the electron during its transit to the anode, whilst the remainder fraction of e ( d − x )/ d charge is induced by the ion during its transit to the cathode. Addition of those two fractions gives a charge equal to the charge of one electron. Thus by counting the electrons arriving at the anode or the ions at the cathode we derive the same figure in current measurement. However, since the electrons have a drift velocity about three orders of magnitude greater (in nanosecond range) than the ions, the induced signal may be separated in two components of different significance when the ion transit time may become greater than the pixel time on the scanned image. The GDD has thus two inherent time-constants, a very short one due to the electrons and a longer one due to the ions. When the ion transit time is greater than the pixel dwell time, the useful signal intensity decreases together with an increase of signal background noise or smearing of image edges due to the ions lagging behind. As a consequence, the above derivations, which include the total electron and ion contributions must be modified accordingly with new equations for the case of fast scanning rates. [ 7 ] The electrode geometry can be altered with a view to decrease the ion transit time as can be done with a needle or cylindrical geometry.
This fundamental approach helps also understand the so-called “ specimen absorbed current ” mode of detection in the vacuum SEM, which is limited only to conductive specimens. Image formation of non-conductive specimens now possible in the ESEM, can be understood in terms of an induced displacement current in the external circuit via a capacitor-like action with the specimen being the dielectric between its surface and the underlying electrode. [ 4 ] Therefore, the (misnomer) "specimen absorbed current" per se plays no part in any useful image formation except to dissipate the charge (in conductors), without which insulators cannot be generally imaged in vacuum (except in the rare case when the incident beam current equals the total emitted current).
By use of a derivation for the Townsend coefficient given by von Engel, [ 6 ] the gain factor G , in the case of SE with total current collection I tot (i.e. for R = 1), is found by:
where A and B are tabulated constants for various gases. In the diagram supplied, we plot the gain characteristics for nitrogen with A = 9.0 and B = 256.5 valid in the range 75–450 V/(Pa·m) for the ratio E / p . We should note that in ESEM work the product pd < 3 Pa·m, since at higher values no useful beam is transmitted through the gas layer to the specimen surface. [ 8 ] The gray-shaded area shows the region of GDD operation provided also that the γ processes are very low and do not trigger a breakdown of the proportional amplification. [ 4 ] This area contains the maxima of the gain curves, which further re-enforces the successful application of this technology to ESEM. The curves outside the shaded area can be used with beam energy greater than 30 kV, and in future development of environmental or atmospheric transmission scanning electron microscopes employing very high beam energy.
The diagram showing the principle of GDD constitutes a versatile implementation that includes not only the SE mode but also the BSE and a combination of these. Even if only the SE signal is desirable to use alone, at least one additional concentric electrode is recommended to employ in order to help in the separation from interference of BSE and also from other noise sources such as the skirt electrons scattered out of the primary beam by the gas. This addition may act as a "guard" electrode, and by varying its bias independently from the SE electrode, the image contrast can be controlled purposefully. Alternative control electrodes are used such as a mesh between anode and cathode. [ 4 ] A multipurpose array of electrodes below and above the specimen and above the pressure limiting aperture of the ESEM has also been described elsewhere. [ 9 ]
The development of this detector has required devoted electronics circuitry, especially when the signal is picked up by the anode at high bias, because the floating current amplified must be coupled at full bandwidth to the ground amplifier and video display circuits (developed by ElectroScan). [ 9 ] An alternative is to bias the cathode with a negative potential and pickup the signal from the anode at floating ground without the need for coupling between amplifier stages. However, this would require extra precaution to protect users from exposure to a high potential at the specimen stage.
A further alternative that has been implemented at the laboratory stage is by the application of a high bias at the anode but by pickup of the signals from the cathode at floating ground, as shown in the accompanying diagram . [ 10 ] Concentric electrodes (E2, E3, E4) are made on a copper-coated fiberglass printed circuit board (PCB) and a copper wire (E1) is added at the center of the disk. The anode is made again from the same PCB with a conical hole (400 micrometres) to act as a pressure limiting aperture in the ESEM. The exposed fiberglass material inside the aperture cone together with its surface above are coated with silver paint in continuity with the copper material of the anode electrode (E0), which is held at high potential. The cathode electrodes are independently connected to ground amplifiers, which, in fact, can be biased with low voltage directly from the amplifier power supplies in the range of ±15 volts without any further coupling required. On account of the induction mechanism operating behind the GDD, this configuration is equivalent to the previous diagram, except for the inverted signal that is electronically restored. While electrode E0 is held at 250 V, meaningful imaging is done as shown by a series of images with composition of signals from various electrodes at two pressures of supplied air. All images show part of the central copper wire (E1), exposed fibreglass (FG, middle), and copper (part of E2) with some silver paint used to attach the wire. The close resemblance of (a) with (b) at low pressure and (c) with (d) at high pressure is a manifestation of the principle of equivalence by induction. The purest SE image is (e) and the purest BSE is (h). Image (f) has prevailing SE characteristics, whilst (g) has a comparable contribution of both SE and BSE. Images (a) and (b) are dominated by SE with some BSE contribution, whilst (c) and (d) have comparable contribution by both SE and BSE.
The very bright areas on the FG material result from genuine high specimen signal yield and not from erratic charging or other artifacts familiar with plastics in vacuum SEM. High yield of edges, oblique incidence, etc. can for the first time be studied from the true surfaces without obstruction in ESEM. Mild charging, if present, may produce stable contrast characteristic of material properties and can be used as a means for studies of the physics of the surfaces. [ 10 ] The images presented in this series are reproductions from photographic paper with limited bandwidth, on which attempting to bring up detail in dark areas results in saturating the bright areas and vice versa, whilst a lot more information is usually contained on the negative film. Electronic manipulation of the signal together with modern computer graphics can overcome some old imaging limitations.
An example of the GDD operating at low voltage is shown with four images of the same field of view of a polished mineral containing aluminum, iron, silicon and some unknown surface impurities. The anode electrode is a single thin wire placed on the side and below the specimen surface, several mm away from it. [ 11 ] Image (a) shows predominantly SE contrast at low pressure, whilst (b) shows BSE material contrast at higher pressure. Image (c) shows cathodoluminescence (CL) from the specimen surface by use of water vapor (which does not scintillate), whilst (d) shows additional photon signal by changing the gas to air which scintillates by signal electrons originating from the specimen. The latter appears to be a mixture of CL with SE, but it may also contain additional information from the surface contaminant charging to a varying degree with gas pressure.
The GDD at high voltage has clear advantages over the low voltage mode, but the latter may be used easily with special applications such as at very high pressures where the BSE produce a high ionization gain from their own high energy, or in cases when the electric field requires shaping to purposeful ends. In general, the detector should be designed to operate at both high and low bias levels including variable negative (electron retarding) bias [ 7 ] with important contrast generation.
Further improvements have been envisaged, such as the use of special electrode materials, gas composition and shaping the trajectory of detection electrons by special electric and magnetic fields (page 91). [ 4 ]
The above described principles have been further implemented in ESEM with detection of secondary and backscattered electrons for 3D imaging with multi-detector method by Slowko et al. [ 12 ] Fitzek et al. have rectified some drawbacks of an available commercial ESEM by optimizing the pressure limiting system and the secondary electron detection resulting in high-quality imaging. [ 13 ]
The first commercial implementation of the GDD was carried out by ElectroScan Corporation [ 14 ] employing the acronym ESD for "environmental secondary detector", which was followed by an improved version termed "gaseous secondary electron detector" (GSED). The use of the magnetic field of the objective lens of the microscope has been incorporated in another commercial patent. [ 15 ] LEO company (now Carl Zeiss SMT [ 16 ] ) has used the scintillation mode and the ionization (needle) mode of the GDD on its environmental SEMs at low and also extended pressure range. | https://en.wikipedia.org/wiki/Gaseous_detection_device |
Gaseous diffusion is a technology that was used to produce enriched uranium by forcing gaseous uranium hexafluoride (UF 6 ) through microporous membranes. This produces a slight separation (enrichment factor 1.0043) between the molecules containing uranium-235 ( 235 U) and uranium-238 ( 238 U). By use of a large cascade of many stages, high separations can be achieved. It was the first process to be developed that was capable of producing enriched uranium in industrially useful quantities, but is nowadays considered obsolete, having been superseded by the more-efficient gas centrifuge process (enrichment factor 1.05 to 1.2). [ 1 ] [ 2 ]
Gaseous diffusion was devised by Francis Simon and Nicholas Kurti at the Clarendon Laboratory in 1940, tasked by the MAUD Committee with finding a method for separating uranium-235 from uranium-238 in order to produce a bomb for the British Tube Alloys project. The prototype gaseous diffusion equipment itself was manufactured by Metropolitan-Vickers (MetroVick) at Trafford Park , Manchester, at a cost of £150,000 for four units, for the M. S. Factory, Valley . This work was later transferred to the United States when the Tube Alloys project became subsumed by the later Manhattan Project . [ 3 ]
Of the 33 known radioactive primordial nuclides , two ( 235 U and 238 U) are isotopes of uranium . These two isotopes are similar in many ways, except that only 235 U is fissile (capable of sustaining a nuclear chain reaction of nuclear fission with thermal neutrons ). In fact, 235 U is the only naturally occurring fissile nucleus. [ 4 ] Because natural uranium is only about 0.72% 235 U by mass, it must be enriched to a concentration of 2–5% to be able to support a continuous nuclear chain reaction [ 5 ] when normal water is used as the moderator. The product of this enrichment process is called enriched uranium.
Gaseous diffusion is based on Graham's law , which states that the rate of effusion of a gas is inversely proportional to the square root of its molecular mass . For example, in a box with a microporous membrane containing a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules, if the pore diameter is smaller than the mean free path length ( molecular flow ). The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. A single container wherein the enrichment process takes place through gaseous diffusion is called a diffuser .
UF 6 is the only compound of uranium sufficiently volatile to be used in the gaseous diffusion process. Fortunately, fluorine consists of only a single isotope 19 F, so that the 1% difference in molecular weights between 235 UF 6 and 238 UF 6 is due only to the difference in weights of the uranium isotopes. For these reasons, UF 6 is the only choice as a feedstock for the gaseous diffusion process. [ 6 ] UF 6 , a solid at room temperature, sublimes at 56.4 °C (133 °F) at 1 atmosphere. [ 7 ] The triple point is at 64.05 °C and 1.5 bar. [ 8 ] Applying Graham's law gives:
where:
This explains the 0.4% difference in the average velocities of 235 UF 6 molecules over that of 238 UF 6 molecules. [ 9 ]
UF 6 is a highly corrosive substance . It is an oxidant [ 10 ] and a Lewis acid which is able to bind to fluoride , for instance the reaction of copper(II) fluoride with uranium hexafluoride in acetonitrile is reported to form copper(II) heptafluorouranate(VI), Cu(UF 7 ) 2 . [ 11 ] It reacts with water to form a solid compound, and is very difficult to handle on an industrial scale. [ 6 ] As a consequence, internal gaseous pathways must be fabricated from austenitic stainless steel and other heat-stabilized metals. Non-reactive fluoropolymers such as Teflon must be applied as a coating to all valves and seals in the system.
Gaseous diffusion plants typically use aggregate barriers (porous membranes) constructed of sintered nickel or aluminum , with a pore size of 10–25 nanometers (this is less than one-tenth the mean free path of the UF 6 molecule). [ 4 ] [ 6 ] They may also use film-type barriers, which are made by boring pores through an initially nonporous medium. One way this can be done is by removing one constituent in an alloy, for instance using hydrogen chloride to remove the zinc from silver-zinc (Ag-Zn) or sodium hydroxide to remove aluminum from Ni-Al alloy.
Because the molecular weights of 235 UF 6 and 238 UF 6 are nearly equal, very little separation of the 235 U and 238 U occurs in a single pass through a barrier, that is, in one diffuser. It is therefore necessary to connect a great many diffusers together in a sequence of stages, using the outputs of the preceding stage as the inputs for the next stage. Such a sequence of stages is called a cascade . In practice, diffusion cascades require thousands of stages, depending on the desired level of enrichment. [ 6 ]
All components of a diffusion plant must be maintained at an appropriate temperature and pressure to assure that the UF 6 remains in the gaseous phase. The gas must be compressed at each stage to make up for a loss in pressure across the diffuser. This leads to compression heating of the gas, which then must be cooled before entering the diffuser. The requirements for pumping and cooling make diffusion plants enormous consumers of electric power . Because of this, gaseous diffusion was the most expensive method used until recently for producing enriched uranium. [ 12 ]
Workers working on the Manhattan Project in Oak Ridge, Tennessee , developed several different methods for the separation of isotopes of uranium. Three of these methods were used sequentially at three different plants in Oak Ridge to produce the 235 U for " Little Boy " and other early nuclear weapons . In the first step, the S-50 uranium enrichment facility used the thermal diffusion process to enrich the uranium from 0.7% up to nearly 2% 235 U. This product was then fed into the gaseous diffusion process at the K-25 plant, the product of which was around 23% 235 U. Finally, this material was fed into calutrons at the Y-12 . These machines (a type of mass spectrometer ) employed electromagnetic isotope separation to boost the final 235 U concentration to about 84%.
The preparation of UF 6 feedstock for the K-25 gaseous diffusion plant was the first ever application for commercially produced fluorine, and significant obstacles were encountered in the handling of both fluorine and UF 6 . For example, before the K-25 gaseous diffusion plant could be built, it was first necessary to develop non-reactive chemical compounds that could be used as coatings, lubricants and gaskets for the surfaces that would come into contact with the UF 6 gas (a highly reactive and corrosive substance). Scientists of the Manhattan Project recruited William T. Miller , a professor of organic chemistry at Cornell University , to synthesize and develop such materials, because of his expertise in organofluorine chemistry . Miller and his team developed several novel non-reactive chlorofluorocarbon polymers that were used in this application. [ 13 ]
Calutrons were inefficient and expensive to build and operate. As soon as the engineering obstacles posed by the gaseous diffusion process had been overcome and the gaseous diffusion cascades began operating at Oak Ridge in 1945, all of the calutrons were shut down. The gaseous diffusion technique then became the preferred technique for producing enriched uranium. [ 4 ]
At the time of their construction in the early 1940s, the gaseous diffusion plants were some of the largest buildings ever constructed. [ citation needed ] Large gaseous diffusion plants were constructed by the United States, the Soviet Union (including a plant that is now in Kazakhstan ), the United Kingdom , France , and China . Most of these have now closed or are expected to close, unable to compete economically with newer enrichment techniques. Some of the technology used in pumps and membranes remains top secret. Some of the materials that were used remain subject to export controls, as a part of the continuing effort to control nuclear proliferation .
In 2008, gaseous diffusion plants in the United States and France still generated 33% of the world's enriched uranium. [ 12 ] However, the French plant ( Eurodif 's Georges-Besse plant ) definitively closed in June 2012, [ 14 ] and the Paducah Gaseous Diffusion Plant in Kentucky operated by the United States Enrichment Corporation (USEC) (the last fully functioning uranium enrichment facility in the United States to employ the gaseous diffusion process [ 5 ] [1] ) ceased enrichment in 2013. [ 15 ] The only other such facility in the United States, the Portsmouth Gaseous Diffusion Plant in Ohio, ceased enrichment activities in 2001. [ 5 ] [ 16 ] [ 17 ] Since 2010, the Ohio site is now used mainly by AREVA , a French conglomerate , for the conversion of depleted UF 6 to uranium oxide . [ 18 ] [ 19 ]
As existing gaseous diffusion plants became obsolete, they were replaced by second generation gas centrifuge technology, which requires far less electric power to produce equivalent amounts of separated uranium. AREVA replaced its Georges Besse gaseous diffusion plant with the Georges Besse II centrifuge plant. [2] | https://en.wikipedia.org/wiki/Gaseous_diffusion |
Gaseous fire suppression , also called clean agent fire suppression , is the use of inert gases and chemical agents to extinguish a fire . These agents are governed by the National Fire Protection Association (NFPA) Standard for Clean Agent Fire Extinguishing Systems – NFPA 2001 in the US, with different standards and regulations elsewhere. The system typically consists of the agent, agent storage containers, agent release valves, fire detectors , fire detection system (wiring control panel, actuation signaling), agent delivery piping, and agent dispersion nozzles.
There are four means used by the agents to extinguish a fire. They act on the " fire tetrahedron ": [ 1 ]
Broadly speaking, there are two methods for applying an extinguishing agent: total flooding and local application:
In the context of automatic extinguishing systems, local application generally refers to the use of systems that have been emplaced some time prior to their usage rather than the use of manually operated wheeled or portable fire extinguishers, although the nature of the agent delivery is similar and many automatic systems may also be activated manually. The lines are blurred somewhat with portable automatic extinguishing systems, although these are not common.
Room integrity testing (RIT) is also required in conjunction with gas fire suppression systems. RIT ensures that in the event of a fire, the room's containment is sufficient to ensure the effectiveness of the suppression system. RIT works by creating pressure within the room or enclosure where the suppression system has been installed and ensuring that the gas does not escape from the room so quickly that it is unable to extinguish the fire. [ 2 ]
An extinguishing system which is primarily based on inert gases, such as CO 2 or nitrogen, in enclosed spaces presents a risk of suffocation. [ 3 ] Some incidents have occurred where individuals in these spaces have been killed by inert gas release. When installed according to fire codes the systems have an excellent safety record. To prevent such occurrences, additional life safety systems are typically installed with a warning alarm that precedes the agent release. The warning, usually an audible and visible alert, advises the immediate evacuation of the enclosed space. After a preset time, the agent starts to discharge. This can be paused by activating an abort switch, which pauses the countdown as long as it is activated, allowing everyone to evacuate the area. Accidents have also occurred during maintenance of these systems, so proper safety precautions must be taken beforehand. [ 4 ]
The pressure differential caused by these gases may be sufficient to break windows and walls. Pressure vents are mandatory on inert gases and may be required on synthetic agents. These are installed working on the physical strength of the protected space and vary in size.
A study carried out by the Italian Workers' Compensation Authority and the Italian Fire Brigade (Piccolo et al., 2018) reported 12 different accidents caused by inert gas fire suppression systems that in many cases have resulted in serious injuries. From the cases analyzed, it was determined that the over pressure of inert gas systems can constitute a risk even in the presence of a system designed and built according to technical standards. [ 5 ] On September 20, 2018, two people died after an inert gas leak from a fire suppression system located in the State Archives in Arezzo (Italy). [ 6 ] On 8 July 2013 an explosion of Argonite cylinders tore through a Hertfordshire (U.K.) construction site, killing a plumber and injuring six other workers. [ 7 ]
Red Bee Media had a major incident with their broadcast playout facility in London, England, that is used by BBC Television , Channel 4 , Channel 5 and ViacomCBS . The broadcasters upload programs and continuity links to Red Bee's servers and then broadcast to tv and online. On 25 September 2021 a gaseous fire suppression system at the facility was triggered, causing loss of service. It was found that an acoustic shock wave from the gas release nozzles had severely damaged the servers resulting in the hard drives being destroyed. [ 8 ] | https://en.wikipedia.org/wiki/Gaseous_fire_suppression |
Gaseous mediators are chemicals that are produced in small amounts by some cells of the mammalian body and have a number of biological signalling functions. There are three so-far-identified gaseous mediator molecules: nitric oxide (NO), hydrogen sulfide (H 2 S), and carbon monoxide (CO). [ 1 ]
Endogenous gaseous mediators have shown anti-inflammatory and cytoprotective properties [ 2 ] Combination nonsteroidal anti-inflammatory drugs featuring both a cyclooxygenase inhibitor and gaseous mediator releasing component are being investigated as a safer alternative to current anti-inflammatory drugs [ 3 ] due to their potential reduction in risk for gastrointestinal ulcer formation. [ 4 ]
When septic shock occurs in the human body due to bacterial toxins, nitric oxide is released by a variety of cells through the expression of inducible nitric oxide synthase in order to induce vasodilation as part of the inflammatory response. [ 5 ] The released nitric oxide can be crucial to the body by reducing instances of platelet and leukocyte adhesion while also counteracting apoptosis. [ 6 ] However, prolonged septic shock could lead to the overproduction of nitric oxide, which could lead to cell damage due to nitric oxide radical formation and peroxynitrite (ONOO − ) formation after interacting with oxygen in the body. [ 5 ] In order to alleviate the toxic effects caused by overproduction of nitric oxide during septic shock, a single high dose (5g IV) of Vitamin B12 has shown the potential to inhibit nitric oxide synthase while acting as a radical scavenger that assists in the elimination of excess nitric oxide produced during prolonged septic shock. [ 6 ] | https://en.wikipedia.org/wiki/Gaseous_mediator |
Gaseous signaling molecules are gaseous molecules that are either synthesized internally ( endogenously ) in the organism , tissue or cell or are received by the organism, tissue or cell from outside (say, from the atmosphere or hydrosphere , as in the case of oxygen ) and that are used to transmit chemical signals which induce certain physiological or biochemical changes in the organism, tissue or cell. The term is applied to, for example, oxygen , carbon dioxide , sulfur dioxide , nitrous oxide , hydrogen cyanide , ammonia , methane , hydrogen , ethylene , etc.
Select gaseous signaling molecules behave as neurotransmitters and are called gasotransmitters . These include nitric oxide , carbon monoxide , and hydrogen sulfide .
Historically, the study of gases and physiological effects was categorized under factitious airs .
The biological roles of each of the gaseous signaling molecules are outlined below.
Gasotransmitters are a class of neurotransmitters . Only three gases are accepted to be classified as gasotransmitters including nitric oxide , carbon monoxide , and hydrogen sulfide .
Oxygen , O 2 , is an essential gaseous signaling molecule & biological messenger important in many physiological and pathological processes, acting via cellular gasoreceptor proteins and other signaling pathways. [ 1 ] [ 2 ] The levels of O 2 in cells or organisms must be tighly regulated to ensure normoxic and not uncontrolled hypoxic or anoxic or hyperoxic states. In mammals , specialized tissues such as carotid body sense O 2 levels.
Carbon dioxide, CO 2 , is one of the mediators of local autoregulation of blood supply. If its levels are high, the capillaries expand to allow a greater blood flow to that tissue.
Mosquitoes are attracted to humans by sensing the CO 2 via gustatory receptors, a type of gasoreceptor. [ 3 ]
Although the body requires oxygen for metabolism, low oxygen levels normally do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels. [ 4 ]
The respiratory centers try to maintain an arterial CO 2 pressure of 40 mm Hg. With intentional hyperventilation, the CO 2 content of arterial blood may be lowered to 10–20 mm Hg (the oxygen content of the blood is little affected), and the respiratory drive is diminished. This is why one can hold one's breath longer after hyperventilating than without hyperventilating. This carries the risk that unconsciousness may result before the need to breathe becomes overwhelming, which is why hyperventilation is particularly dangerous before free diving.
Nitric oxide , NO, is a key vertebrate biological messenger important in many physiological and pathological processes, acting, for instance, as a powerful vasodilator in humans (see Biological functions of nitric oxide ). Mammalian cells have a specialized gasoreceptor soluble guanylyl cyclase that bind to NO and trigger NO-dependent cellular signaling.
Nitrous oxide , N 2 O, in biological systems can be formed by an enzymatic or non-enzymatic reduction of nitric oxide . [ 5 ] In vitro studies have shown that endogenous nitrous oxide can be formed by the reaction between nitric oxide and thiol . [ 6 ] Some authors have shown that this process of NO reduction to N 2 O takes place in hepatocytes , specifically in their cytoplasm and mitochondria , and suggested that the N 2 O can possibly be produced in mammalian cells. [ 7 ] It is well known that N 2 O is produced by some bacteria during process called denitrification. [ 8 ]
In 1981, it was first suggested from clinical work with nitrous oxide (N 2 O) that a gas had a direct action at pharmacological receptors and thereby acted as a neurotransmitter. [ 9 ] [ 10 ] [ 11 ] In vitro experiments confirmed these observations [ 12 ] which were replicated at NIDA later. [ 13 ]
Apart from its direct [ 14 ] [ 15 ] and indirect actions at opioid receptors, [ 16 ] it was also shown that N 2 O inhibits NMDA receptor -mediated activity and ionic currents and diminishes NMDA receptor-mediated excitotoxicity and neurodegeneration. [ 17 ] Nitrous oxide also inhibits methionine synthase and slows the conversion of homocysteine to methionine , increases homocysteine concentration and decreases methionine concentration. This effect was shown in lymphocyte cell cultures [ 18 ] and in human liver biopsy samples. [ 19 ]
Nitrous oxide does not bind as a ligand to the heme and does not react with thiol-containing proteins . Nevertheless, studies have shown that nitrous oxide can reversibly and non-covalently "insert" itself into the inner structures of some heme-containing proteins such as hemoglobin , myoglobin , cytochrome oxidase and alter their structure and function. [ 20 ] The ability of nitrous oxide to alter the structure and function of these proteins was demonstrated by shifts in infrared spectra of cysteine thiols of hemoglobin [ 21 ] and by partial and reversible inhibition of cytochrome oxidase. [ 22 ]
Endogenous nitrous oxide can possibly play a role in modulating endogenous opioid [ 23 ] [ 24 ] and NMDA systerosclerosis, severe sepsis, severe malaria, or autoimmunity. Clinical tests involving humans have been performed, but the results have not yet been released. [ 25 ]
Carbon suboxide , C 3 O 2 , can be produced in small amounts in any biochemical process that normally produces carbon monoxide , CO, for example, during heme oxidation by heme oxygenase-1. It can also be formed from malonic acid. It has been shown that carbon suboxide in an organism can quickly polymerize into macrocyclic polycarbon structures with the common formula (C 3 O 2 ) n (mostly (C 3 O 2 ) 6 and (C 3 O 2 ) 8 ), and that those macrocyclic compounds are potent inhibitors of Na + /K + -ATP-ase and Ca-dependent ATP-ase, and have digoxin -like physiological properties and natriuretic and antihypertensive actions. Those macrocyclic carbon suboxide polymer compounds are thought to be endogenous digoxin-like regulators of Na + /K + -ATP-ases and Ca-dependent ATP-ases, and endogenous natriuretics and antihypertensives. [ 26 ] [ 27 ] [ 28 ] Other than that, some authors think also that those macrocyclic compounds of carbon suboxide can possibly diminish free radical formation and oxidative stress and play a role in endogenous anticancer protective mechanisms, for example in the retina . [ 29 ]
The role of sulfur dioxide , SO 2 , in mammalian biology is not well understood. [ 30 ] Sulfur dioxide blocks nerve signals from the pulmonary stretch receptors and abolishes the Hering–Breuer inflation reflex .
Sulfur dioxide plays a role in diminishing an experimental lung damage caused by oleic acid . Endogenous sulfur dioxide lowered lipid peroxidation, free radical formation, oxidative stress and inflammation during an experimental lung damage. Conversely, a successful lung damage caused a significant lowering of endogenous sulfur dioxide production, and an increase in lipid peroxidation, free radical formation, oxidative stress and inflammation. Moreover, blockade of an enzyme that produces endogenous SO 2 significantly increased the amount of lung tissue damage in the experiment. Conversely, adding acetylcysteine or glutathione to the rat diet increased the amount of endogenous SO 2 produced and decreased the lung damage, the free radical formation, oxidative stress, inflammation and apoptosis. [ 31 ]
Endogenous sulfur dioxide may play a role in regulating cardiac and blood vessel function, and aberrant or deficient sulfur dioxide metabolism can contribute to several different cardiovascular diseases, such as arterial hypertension , atherosclerosis , pulmonary arterial hypertension , stenocardia . [ 32 ]
In children with pulmonary arterial hypertension due to congenital heart diseases, the level of homocysteine is higher and the level of endogenous sulfur dioxide is lower than in normal control children. Moreover, these biochemical parameters strongly correlated to the severity of pulmonary arterial hypertension. Authors considered homocysteine to be one of useful biochemical markers of disease severity and sulfur dioxide metabolism to be one of potential therapeutic targets in those patients. [ 33 ]
Endogenous sulfur dioxide also lowers the proliferation rate of endothelial smooth muscle cells in blood vessels, via lowering the MAPK activity and activating adenylyl cyclase and protein kinase A . [ 34 ] Smooth muscle cell proliferation is one of important mechanisms of hypertensive remodeling of blood vessels and their stenosis , so it is an important pathogenetic mechanism in arterial hypertension and atherosclerosis.
Endogenous sulfur dioxide in low concentrations causes endothelium-dependent vasodilation . In higher concentrations it causes endothelium-independent vasodilation and has a negative inotropic effect on cardiac output function, thus effectively lowering blood pressure and myocardial oxygen consumption. The vasodilating effects of sulfur dioxide are mediated via ATP-dependent calcium channels and L-type ("dihydropyridine") calcium channels. Endogenous sulfur dioxide is also a potent antiinflammatory, antioxidant and cytoprotective agent. It lowers blood pressure and slows hypertensive remodeling of blood vessels, especially thickening of their intima. It also regulates lipid metabolism. [ 35 ]
Endogenous sulfur dioxide also diminishes myocardial damage, caused by isoproterenol adrenergic hyperstimulation, and strengthens the myocardial antioxidant defense reserve. [ 36 ]
Some authors have shown that neurons can produce hydrogen cyanide , HCN, upon activation of their opioid receptors by endogenous or exogenous opioids. They have also shown that neuronal production of HCN activates NMDA receptors and plays a role in signal transduction between neuronal cells ( neurotransmission ). Moreover, increased endogenous neuronal HCN production under opioids was seemingly needed for adequate opioid analgesia , as analgesic action of opioids was attenuated by HCN scavengers. They considered endogenous HCN to be a neuromodulator. [ 37 ]
It was also shown that, while stimulating muscarinic cholinergic receptors in cultured pheochromocytoma cells increases HCN production, in a living organism ( in vivo ) muscarinic cholinergic stimulation actually decreases HCN production. [ 38 ]
Leukocytes generate HCN during phagocytosis . [ 37 ]
The vasodilatation , caused by sodium nitroprusside , has been shown to be mediated not only by NO generation, but also by endogenous cyanide generation, which adds not only toxicity, but also some additional antihypertensive efficacy compared to nitroglycerine and other non-cyanogenic nitrates which do not cause blood cyanide levels to rise. [ 39 ]
Ammonia, NH 3 , also plays a role in both normal and abnormal animal physiology . It is biosynthesised through normal amino acid metabolism, but is toxic in high concentrations. [ 40 ] The liver converts ammonia to urea through a series of reactions known as the urea cycle . Liver dysfunction, such as that seen in cirrhosis , may lead to elevated amounts of ammonia in the blood ( hyperammonemia ). Likewise, defects in the enzymes responsible for the urea cycle, such as ornithine transcarbamylase , lead to hyperammonemia. Hyperammonemia contributes to the confusion and coma of hepatic encephalopathy , as well as the neurologic disease common in people with urea cycle defects and organic acidurias . [ 41 ]
Ammonia is important for normal animal acid/base balance. After formation of ammonium from glutamine , α-ketoglutarate may be degraded to produce two molecules of bicarbonate , which are then available as buffers for dietary acids. Ammonium is excreted in the urine, resulting in net acid loss. Ammonia may itself diffuse across the renal tubules, combine with a hydrogen ion, and thus allow for further acid excretion. [ 42 ]
Some authors have shown that endogenous methane , CH 4 , is produced not only by the intestinal flora and then absorbed into the blood , but also is produced - in small amounts - by eukaryotic cells (during process of lipid peroxidation). And they have also shown that the endogenous methane production rises during an experimental mitochondrial hypoxia , for example, sodium azide intoxication. They thought that methane could be one of intercellular signals of hypoxia and stress. [ 43 ]
Other authors have shown that cellular methane production also rises during sepsis or bacterial endotoxemia , including an experimental imitation of endotoxemia by lipopolysaccharide (LPS) administration. [ 44 ]
Some other researchers have shown that methane, produced by the intestinal flora, is not fully "biologically neutral" to the intestine, and it participates in the normal physiologic regulation of peristalsis . And its excess causes not only belching, flatulence and belly pain, but also functional constipation. [ 45 ]
Ethylene , H 2 C=CH 2 , serves as a hormone in plants . [ 46 ] It acts at trace levels throughout the life of the plant by stimulating or regulating the ripening of fruit , the opening of flowers , and the abscission (or shedding) of leaves .
Commercial ripening rooms use "catalytic generators" to make ethylene gas from a liquid supply of ethanol. Typically, a gassing level of 500 to 2,000 ppm is used, for 24 to 48 hours. Care must be taken to control carbon dioxide levels in ripening rooms when gassing, as high temperature ripening (20 °C; 68 °F) has been seen to produce CO 2 levels of 10% in 24 hours. [ 47 ]
Ethylene has been used since the ancient Egyptians, who would gash figs in order to stimulate ripening (wounding stimulates ethylene production by plant tissues). The ancient Chinese would burn incense in closed rooms to enhance the ripening of pears. In 1864, it was discovered that gas leaks from street lights led to stunting of growth, twisting of plants, and abnormal thickening of stems. [ 46 ] In 1901, a Russian scientist named Dimitry Neljubow showed that the active component was ethylene. [ 48 ] Sarah Doubt discovered that ethylene stimulated abscission in 1917. [ 49 ] It wasn't until 1934 that Gane reported that plants synthesize ethylene. [ 50 ] In 1935, Crocker proposed that ethylene was the plant hormone responsible for fruit ripening as well as senescence of vegetative tissues. [ 51 ]
Ethylene is produced from essentially all parts of higher plants, including leaves, stems, roots, flowers, fruits, tubers, and seeds.
Ethylene production is regulated by a variety of developmental and environmental factors. During the life of the plant, ethylene production is induced during certain stages of growth such as germination , ripening of fruits, abscission of leaves, and senescence of flowers. Ethylene production can also be induced by a variety of external aspects such as mechanical wounding, environmental stresses, and certain chemicals including auxin and other regulators. [ 52 ]
Ethylene is biosynthesized from the amino acid methionine to S -adenosyl- L -methionine (SAM, also called Adomet) by the enzyme Met Adenosyltransferase. SAM is then converted to 1-aminocyclopropane-1-carboxylic acid (ACC) by the enzyme ACC synthase (ACS). The activity of ACS determines the rate of ethylene production, therefore regulation of this enzyme is key for the ethylene biosynthesis. The final step requires oxygen and involves the action of the enzyme ACC-oxidase (ACO), formerly known as the ethylene forming enzyme (EFE). Ethylene biosynthesis can be induced by endogenous or exogenous ethylene. ACC synthesis increases with high levels of auxins , especially indole acetic acid (IAA) and cytokinins .
Ethylene is perceived by a family of five transmembrane protein dimers such as the ETR 1 gasoreceptor protein in Arabidopsis . The gene encoding an ethylene receptor [ which? ] has been cloned in Arabidopsis thaliana and then in tomato . [ citation needed ] Ethylene receptors are encoded by multiple genes in the Arabidopsis and tomato genomes . Mutations in any of the gene family , which comprises five receptors in Arabidopsis and at least six in tomato, can lead to insensitivity to ethylene. [ 53 ] DNA sequences for ethylene receptors have also been identified in many other plant species and an ethylene binding protein has even been identified in Cyanobacteria . [ 46 ]
Environmental cues such as flooding, drought, chilling, wounding, and pathogen attack can induce ethylene formation in plants. In flooding, roots suffer from lack of oxygen, or anoxia , which leads to the synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC). ACC is transported upwards in the plant and then oxidized in leaves. The ethylene produced causes nastic movements (epinasty) of the leaves, perhaps helping the plant to lose water. [ 54 ]
Ethylene in plant induces such responses:
Small amounts of endogenous ethylene are also produced in mammals , including humans , due to lipid peroxidation. Some of endogenous ethylene is then oxidized to ethylene oxide , which is able to alkylate DNA and proteins , including hemoglobin (forming a specific adduct with its N-terminal valine , N-hydroxyethyl-valine). [ 71 ] Endogenous ethylene oxide, just as like environmental (exogenous) one, can alkylate guanine in DNA, forming an adduct 7-(2-hydroxyethyl)-guanine, and this poses an intrinsic carcinogenic risk. [ 72 ] It is also mutagenic. [ 73 ] [ 74 ] | https://en.wikipedia.org/wiki/Gaseous_signaling_molecules |
Gasification is a process that converts biomass - or fossil fuel -based carbonaceous materials into gases, including as the largest fractions: nitrogen (N 2 ), carbon monoxide (CO), hydrogen (H 2 ), and carbon dioxide (CO 2 ). This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling the amount of oxygen and/or steam present in the reaction. The resulting gas mixture is called syngas (from synthesis gas) or producer gas and is itself a fuel due to the flammability of the H 2 and CO of which the gas is largely composed. Power can be derived from the subsequent combustion of the resultant gas, and is considered to be a source of renewable energy if the gasified compounds were obtained from biomass feedstock. [ 1 ] [ 2 ] [ 3 ] [ 4 ]
An advantage of gasification is that syngas can be more efficient than direct combustion of the original feedstock material because it can be combusted at higher temperatures so that the thermodynamic upper limit to the efficiency defined by Carnot's rule is higher. Syngas may also be used as the hydrogen source in fuel cells, however the syngas produced by most gasification systems requires additional processing and reforming to remove the contaminants and other gases such as CO and CO 2 to be suitable for low-temperature fuel cell use, but high-temperature solid oxide fuel cells are capable of directly accepting mixtures of H 2 , CO, CO 2 , steam, and methane. [ 5 ]
Syngas is most commonly burned directly in gas engines , used to produce methanol and hydrogen, or converted via the Fischer–Tropsch process into synthetic fuel . For some materials gasification can be an alternative to landfilling and incineration , resulting in lowered emissions of atmospheric pollutants such as methane and particulates . Some gasification processes aim at refining out corrosive ash elements such as chloride and potassium , allowing clean gas production from otherwise problematic feedstock material. Gasification of fossil fuels is currently widely used on industrial scales to generate electricity. Gasification can generate lower amounts of some pollutants as SO x and NO x than combustion. [ 6 ]
Energy has been produced at industrial scale via gasification since the early 19th century. Initially coal and peat were gasified to produce town gas for lighting and cooking, with the first public street lighting installed in Pall
Mall, London on January 28, 1807, spreading shortly to supply commercial gas lighting to most industrialized cities until the end of the 19th century [ 7 ] when it was replaced with electrical lighting. Gasification and syngas continued to be used in blast furnaces and more significantly in the production of synthetic chemicals where it has been in use since the 1920s. The thousands of sites left toxic residue. Some sites have been remediated, while others are still polluted. [ 8 ]
During both world wars , especially the World War II , the need for fuel produced by gasification reemerged due to the shortage of petroleum. [ 9 ] Wood gas generators , called Gasogene or Gazogène, were used to power motor vehicles in Europe . By 1945 there were trucks, buses and agricultural machines that were powered by gasification. It is estimated that there were close to 9,000,000 vehicles running on producer gas all over the world.
Another example, the Xe than (literally, "coal car" in Vietnamese ) was a minibus that has been converted to run on coal instead of gasoline . This modification regained popularity in Vietnam during the subsidy period , when gasoline was in short supply. Xe than became much less common during the Đổi Mới period, when gasoline became widely accessible again.
In a gasifier, the carbonaceous material undergoes several different processes:
In essence, a limited amount of oxygen or air is introduced into the reactor to allow some of the organic material to be "burned" to produce carbon dioxide and energy, which drives a second reaction that converts further organic material to hydrogen and additional carbon dioxide. Further reactions occur when the formed carbon monoxide and residual water from the organic material react to form methane and excess carbon dioxide (4CO + 2H 2 O → CH 4 + 3CO 2 ). This third reaction occurs more abundantly in reactors that increase the residence time of the reactive gases and organic materials, as well as heat and pressure. Catalysts are used in more sophisticated reactors to improve reaction rates, thus moving the system closer to the reaction equilibrium for a fixed residence time.
Several types of gasifiers are currently available for commercial use: counter-current fixed bed, co-current fixed bed, fluidized bed , entrained flow, plasma, and free radical. [ 1 ] [ 10 ] [ 11 ] [ 12 ]
A fixed bed of carbonaceous fuel (e.g. coal or biomass) through which the "gasification agent" (steam, oxygen and/or air) flows in counter-current configuration. [ 13 ] The ash is either removed in the dry condition or as a slag . The slagging gasifiers have a lower ratio of steam to carbon, [ 14 ] achieving temperatures higher than the ash fusion temperature. The nature of the gasifier means that the fuel must have high mechanical strength and must ideally be non-caking so that it will form a permeable bed, although recent developments have reduced these restrictions to some extent. [ citation needed ] The throughput for this type of gasifier is relatively low. Thermal efficiency is high as the temperatures in the gas exit are relatively low. However, this means that tar and methane production is significant at typical operation temperatures, so product gas must be extensively cleaned before use. The tar can be recycled to the reactor.
In the gasification of fine, undensified biomass such as rice hulls , it is necessary to blow air into the reactor by means of a fan. This creates very high gasification temperature, as high as 1000 C. Above the gasification zone, a bed of fine and hot char is formed, and as the gas is blow forced through this bed, most complex hydrocarbons are broken down into simple components of hydrogen and carbon monoxide. [ 15 ]
Similar to the counter-current type, but the gasification agent gas flows in co-current configuration with the fuel (downwards, hence the name "down draft gasifier"). Heat needs to be added to the upper part of the bed, either by combusting small amounts of the fuel or from external heat sources. The produced gas leaves the gasifier at a high temperature, and most of this heat is often transferred to the gasification agent added in the top of the bed, resulting in an energy efficiency on level with the counter-current type. Since all tars must pass through a hot bed of char in this configuration, tar levels are much lower than the counter-current type.
The fuel is fluidized in oxygen and steam or air. The ash is removed dry or as heavy agglomerates that defluidize. The temperatures are relatively low in dry ash gasifiers, so the fuel must be highly reactive; low-grade coals are particularly suitable. The agglomerating gasifiers have slightly higher temperatures, and are suitable for higher rank coals. Fuel throughput is higher than for the fixed bed, but not as high as for the entrained flow gasifier. The conversion efficiency can be rather low due to elutriation of carbonaceous material. Recycle or subsequent combustion of solids can be used to increase conversion. Fluidized bed gasifiers are most useful for fuels that form highly corrosive ash that would damage the walls of slagging gasifiers. Biomass fuels generally contain high levels of corrosive ash.
Fluidized bed gasifiers uses inert bed material at a fluidized state which enhance the heat and biomass distribution inside a gasifier. At a fluidized state, the superficial fluid velocity is greater than the minimum fluidization velocity required to lift the bed material against the weight of the bed. Fluidized bed gasifiers are divided into Bubbling Fluidized Bed (BFB), Circulating Fluidized Bed (CFB) and Dual Fluidized Bed (DFB) gasifiers.
A dry pulverized solid, an atomized liquid fuel or a fuel slurry is gasified with oxygen (much less frequent: air) in co-current flow. The gasification reactions take place in a dense cloud of very fine particles. Most coals are suitable for this type of gasifier because of the high operating temperatures and because the coal particles are well separated from one another.
The high temperatures and pressures also mean that a higher throughput can be achieved, however thermal efficiency is somewhat lower as the gas must be cooled before it can be cleaned with existing technology. The high temperatures also mean that tar and methane are not present in the product gas; however the oxygen requirement is higher than for the other types of gasifiers. All entrained flow gasifiers remove the major part of the ash as a slag as the operating temperature is well above the ash fusion temperature.
A smaller fraction of the ash is produced either as a very fine dry fly ash or as a black colored fly ash slurry. Some fuels, in particular certain types of biomasses, can form slag that is corrosive for ceramic inner walls that serve to protect the gasifier outer wall. However some entrained flow type of gasifiers do not possess a ceramic inner wall but have an inner water or steam cooled wall covered with partially solidified slag. These types of gasifiers do not suffer from corrosive slags.
Some fuels have ashes with very high ash fusion temperatures. In this case mostly limestone is mixed with the fuel prior to gasification. Addition of a little limestone will usually suffice for the lowering the fusion temperatures. The fuel particles must be much smaller than for other types of gasifiers. This means the fuel must be pulverized, which requires somewhat more energy than for the other types of gasifiers. By far the most energy consumption related to entrained flow gasification is not the milling of the fuel but the production of oxygen used for the gasification.
In a plasma gasifier a high-voltage current is fed to a torch, creating a high-temperature arc. The inorganic residue is retrieved as a glass like substance.
There are a large number of different feedstock types for use in a gasifier, each with different characteristics, including size, shape, bulk density, moisture content, energy content, chemical composition, ash fusion characteristics, and homogeneity of all these properties. Coal and petroleum coke are used as primary feedstocks for many large gasification plants worldwide. Additionally, a variety of biomass and waste-derived feedstocks can be gasified, with wood pellets and chips, waste wood, plastics and aluminium, Municipal Solid Waste (MSW), Refuse-derived fuel (RDF), agricultural and industrial wastes, sewage sludge, switch grass, discarded seed corn, corn stover and other crop residues all being used. [ 1 ]
Chemrec has developed a process for gasification of black liquor . [ 17 ]
Waste gasification has several advantages over incineration:
A major challenge for waste gasification technologies is to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning. Another challenge becoming apparent when implementing the processes in real life is to obtain long service intervals in the plants, so that it is not necessary to close down the plant every few months for cleaning the reactor.
Environmental advocates have called gasification "incineration in disguise" and argue that the technology is still dangerous to air quality and public health. "Since 2003 numerous proposals for waste treatment facilities hoping to use... gasification technologies failed to receive final approval to operate when the claims of project proponents did not withstand public and governmental scrutiny of key claims," according to the Global Alliance for Incinerator Alternatives. [ 18 ] One facility which operated from 2009–2011 in Ottawa had 29 "emissions incidents" and 13 "spills" over those three years. It was also only able to operate roughly 25% of the time. [ 19 ]
Several waste gasification processes have been proposed, but few have yet been built and tested, and only a handful have been implemented as plants processing real waste, and most of the time in combination with fossil fuels. [ 20 ]
One plant (in Chiba , Japan, using the Thermoselect process [ 21 ] ) has been processing industrial waste with natural gas and purified oxygen since year 2000, but has not yet documented positive net energy production from the process.
In 2007 Ze-gen erected a waste gasification demonstration facility in New Bedford, Massachusetts . The facility was designed to demonstrate gasification of specific non-MSW waste streams using liquid metal gasification . [ 22 ] This facility came after widespread public opposition shelved plans for a similar plant in Attleboro, Massachusetts . [ 23 ] Today Ze-gen appears to be defunct, and the company website was taken down in 2014. [ 24 ]
Also in the US, in 2011 a plasma system delivered by PyroGenesis Canada Inc. was tested to gasify municipal solid waste, hazardous waste and biomedical waste at the Hurlburt Field Florida Special Operations Command Air Force base. The plant, which cost $7.4 million to construct, [ 25 ] was closed and sold at a government liquidation auction in May 2013. [ 26 ] [ 27 ] The opening bid was $25. The winning bid was sealed.
In December 2022, the Sierra BioFuels Plant opened in Reno, Nevada, converting landfill waste to synthetic crude oil. [ 28 ]
Syngas can be used for heat production and for generation of mechanical and electrical power. Like other gaseous fuels, producer gas gives greater control over power levels when compared to solid fuels, leading to more efficient and cleaner operation.
Syngas can also be used for further processing to liquid fuels or chemicals.
Gasifiers offer a flexible option for thermal applications, as they can be retrofitted into existing gas fueled devices such as ovens , furnaces , boilers , etc., where syngas may replace fossil fuels. Heating values of syngas are generally around 4–10 MJ/m 3 .
Currently Industrial-scale gasification is primarily used to produce electricity from fossil fuels such as coal, where the syngas is burned in a gas turbine. Gasification is also used industrially in the production of electricity, ammonia and liquid fuels (oil) using Integrated Gasification Combined Cycles ( IGCC ), with the possibility of producing methane and hydrogen for fuel cells. IGCC is also a more efficient method of CO 2 capture as compared to conventional technologies. IGCC demonstration plants have been operating since the early 1970s and some of the plants constructed in the 1990s are now entering commercial service.
In small business and building applications, where the wood source is sustainable, 250–1000 kWe and new zero carbon biomass gasification plants have been installed in Europe that produce tar free syngas from wood and burn it in reciprocating engines connected to a generator with heat recovery. This type of plant is often referred to as a wood biomass CHP unit but is a plant with seven different processes: biomass processing, fuel delivery, gasification, gas cleaning, waste disposal, electricity generation and heat recovery. [ 29 ]
Diesel engines can be operated on dual fuel mode using producer gas. Diesel substitution of over 80% at high loads and 70–80% under normal load variations can easily be achieved. [ 30 ] Spark ignition engines and solid oxide fuel cells can operate on 100% gasification gas. [ 31 ] [ 32 ] [ 33 ] Mechanical energy from the engines may be used for e.g. driving water pumps for irrigation or for coupling with an alternator for electrical power generation.
While small scale gasifiers have existed for well over 100 years, there have been few sources to obtain a ready-to-use machine. Small scale devices are typically DIY projects. However, currently in the United States, several companies offer gasifiers to operate small engines.
In principle, gasification can proceed from just about any organic material, including biomass and plastic waste . The resulting syngas can be combusted. Alternatively, if the syngas is clean enough, it may be used for power production in gas engines, gas turbines or even fuel cells, or converted efficiently to dimethyl ether (DME) by methanol dehydration, methane via the Sabatier reaction , or diesel-like synthetic fuel via the Fischer–Tropsch process . In many gasification processes most of the inorganic components of the input material, such as metals and minerals, are retained in the ash. In some gasification processes (slagging gasification) this ash has the form of a glassy solid with low leaching properties, but the net power production in slagging gasification is low (sometimes negative) and costs are higher.
Regardless of the final fuel form, gasification itself and subsequent processing neither directly emits nor traps greenhouse gases such as carbon dioxide. Power consumption in the gasification and syngas conversion processes may be significant though, and may indirectly cause CO 2 emissions; in slagging and plasma gasification, the electricity consumption may even exceed any power production from the syngas.
Combustion of syngas or derived fuels emits exactly the same amount of carbon dioxide as would have been emitted from direct combustion of the initial fuel. Biomass gasification and combustion could play a significant role in a renewable energy economy, because biomass production removes the same amount of CO 2 from the atmosphere as is emitted from gasification and combustion. While other biofuel technologies such as biogas and biodiesel are carbon neutral , gasification in principle may run on a wider variety of input materials and can be used to produce a wider variety of output fuels.
There are at present a few industrial scale biomass gasification plants. Since 2008 in Svenljunga, Sweden, a biomass gasification plant generates up to 14 MW th , supplying industries and citizens of Svenljunga with process steam and district heating , respectively. The gasifier uses biomass fuels such as CCA or creosote impregnated waste wood and other kinds of recycled wood to produces syngas that is combusted on site. [ 34 ] [ 35 ]
Examples of demonstration projects include: | https://en.wikipedia.org/wiki/Gasification |
Gasochromism is closely related to electrochromism . The process involves the interaction of an electrochrome, usually a metal oxide, such as tungsten oxide, with an oxidizing or reducing gas, commonly oxygen and hydrogen, producing reversible color changes. The gasochromic technology is used commercially in reversible smart windows and gas sensing of oxygen, hydrogen, nitric oxide, hydrogen sulphide and carbon monoxide.
This article about materials science is a stub . You can help Wikipedia by expanding it .
This spectroscopy -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gasochromism |
The gasogene (or gazogene or seltzogene ) is a late Victorian device for producing carbonated water . It consists of two linked glass globes: the lower contained water or other drink to be made sparkling, the upper a mixture of tartaric acid and sodium bicarbonate that reacts to produce carbon dioxide . The produced gas pushes the liquid in the lower container up a tube and out of the device. The globes are surrounded by a wicker or wire protective mesh, as they have a tendency to explode. [ 1 ]
The earliest occurrence of the word noted in the Oxford English Dictionary dates from 1853, quoting a reference in Practical Mechanic's Journal on "Gaillard and Dubois' 'Gazogene' or Aerated Water apparatus". [ 2 ]
A gasogene is mentioned as a residential fixture at 221B Baker Street in Arthur Conan Doyle 's Sherlock Holmes story " A Scandal in Bohemia ": "With hardly a word spoken, but with a kindly eye, he waved me to an armchair, threw across his case of cigars, and indicated a spirit case and a gasogene in the corner." [ 3 ] One is also mentioned in "The Adventure of the Mazarin Stone". The device plays a key role in Bernard Shaw 's 1905 comic play Passion, Poison, and Petrifaction, Or The Fatal Gazogene . [ 4 ]
The word is also used in Douglas Preston and Lincoln Child 's novel Brimstone , published in 2005, on page 106, [ 5 ] and in their 2010 novel Fever Dream on page 362, [ 6 ] and in their 2013 novel "White Fire."
A gasogene is mentioned, on page 13, as being in the forensic laboratory of Dr. Kingsley, consultant forensic examiner of Scotland Yard in Alex Grecian 's 2012 novel The Yard . [ 7 ]
A gasogene is mentioned and its use described in Sherry Thomas 's novel A Study in Scarlet Women (Book 1 of the Lady Sherlock series) on pages 244 to 246. (Ebook ISBN 9780698196353 )
Amelia Peabody pulls a bottle of whiskey, a gasogene, and glasses from a hamper in order to make herself a whiskey and soda after getting her family on a train to Luxor in the novel The Golden One by Elizabeth Peters, a pen name of Barbara Mertz .
This article about an item of drinkware or tool used in preparation or serving of drink is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gasogene |
Gasoline ( North American English ) or petrol ( Commonwealth English ) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines . When formulated as a fuel for engines , gasoline is chemically composed of organic compounds derived from the fractional distillation of petroleum and later chemically enhanced with gasoline additives . It is a high-volume profitable product produced in crude oil refineries. [ 1 ]
The ability of a particular gasoline blend to resist premature ignition (which causes knocking and reduces efficiency in reciprocating engines ) is measured by its octane rating . Tetraethyl lead was once widely used to increase the octane rating but is not used in modern automotive gasoline due to the health hazard . Aviation, off-road motor vehicles, and racing car engines still use leaded gasolines. [ 2 ] [ 3 ] Other substances are frequently added to gasoline to improve chemical stability and performance characteristics, control corrosion, and provide fuel system cleaning. Gasoline may contain oxygen-containing chemicals such as ethanol , MTBE , or ETBE to improve combustion .
English dictionaries show that the term gasoline originates from gas plus the chemical suffixes -ole and -ine . [ 4 ] [ 5 ] [ 6 ] Petrol derives from the Medieval Latin word petroleum (L. petra , rock + oleum , oil). [ 7 ]
Interest in gasoline-like fuels started with the invention of internal combustion engines suitable for use in transportation applications. The so-called Otto engines were developed in Germany during the last quarter of the 19th century. The fuel for these early engines was a relatively volatile hydrocarbon obtained from coal gas . With a boiling point near 85 °C (185 °F) ( n -octane boils at 125.62 °C (258.12 °F) [ 8 ] ), it was well suited for early carburetors (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher compression ratios , but early attempts were blocked by the premature explosion of fuel, known as knocking . In 1891, the Shukhov cracking process became the world's first commercial method to break down heavier hydrocarbons in crude oil to increase the percentage of lighter products compared to simple distillation.
Commercial gasoline as well as other liquid transportation fuels are complex mixtures of hydrocarbons. [ 9 ] The performance specification also varies with season, requiring less volatile blends during summer, in order to minimize evaporative losses.
Gasoline is produced in oil refineries . Roughly 72 liters (19 U.S. gal) of gasoline is derived from a 160-liter (42 U.S. gal) barrel of crude oil . [ 10 ] Material separated from crude oil via distillation , called virgin or straight-run gasoline, does not meet specifications for modern engines (particularly the octane rating ; see below), but can be pooled to the gasoline blend.
The bulk of a typical gasoline consists of a homogeneous mixture of hydrocarbons with between four and twelve carbon atoms per molecule (commonly referred to as C4–C12). [ 11 ] It is a mixture of paraffins ( alkanes ), olefins ( alkenes ), napthenes ( cycloalkanes ), and aromatics . The use of the term paraffin in place of the standard chemical nomenclature alkane is particular to the oil industry (which relies extensively on jargon). The composition of a gasoline depends upon:
The various refinery streams blended to make gasoline have different characteristics. Some important streams include the following:
The terms above are the jargon used in the oil industry, and the terminology varies.
Currently, many countries set limits on gasoline aromatics in general, benzene in particular, and olefin (alkene) content. Such regulations have led to an increasing preference for alkane isomers, such as isomerate or alkylate, as their octane rating is higher than n-alkanes. In the European Union, the benzene limit is set at one percent by volume for all grades of automotive gasoline. This is usually achieved by avoiding feeding C6, in particular cyclohexane , to the reformer unit, where it would be converted to benzene. Therefore, only (desulfurized) heavy virgin naphtha (HVN) is fed to the reformer unit [ 18 ]
Gasoline can also contain other organic compounds , such as organic ethers (deliberately added), plus small levels of contaminants, in particular organosulfur compounds (which are usually removed at the refinery).
On average, U.S. petroleum refineries produce about 19 to 20 gallons of gasoline, 11 to 13 gallons of distillate fuel diesel fuel and 3 to 4 gallons of jet fuel from each 42 U.S. gallons (160 liters) barrel of crude oil. The product ratio depends upon the processing in an oil refinery and the crude oil assay . [ 19 ]
The specific gravity of gasoline ranges from 0.71 to 0.77, [ 20 ] with higher densities having a greater volume fraction of aromatics. [ 21 ] Finished marketable gasoline is traded (in Europe) with a standard reference of 0.755 kilograms per liter (6.30 lb/U.S. gal), (7,5668 lb/ imp gal) its price is escalated or de-escalated according to its actual density. [ clarification needed ] Because of its low density, gasoline floats on water, and therefore water cannot generally be used to extinguish a gasoline fire unless applied in a fine mist.
Quality gasoline should be stable for six months if stored properly, but can degrade over time. [ 22 ] Gasoline stored for a year will most likely be able to be burned in an internal combustion engine without too much trouble. [ 22 ] Gasoline should ideally be stored in an airtight container (to prevent oxidation or water vapor mixing in with the gas) that can withstand the vapor pressure of the gasoline without venting (to prevent the loss of the more volatile fractions) at a stable cool temperature (to reduce the excess pressure from liquid expansion and to reduce the rate of any decomposition reactions). When gasoline is not stored correctly, gums and solids may result, which can corrode system components and accumulate on wet surfaces, resulting in a condition called "stale fuel". Gasoline containing ethanol is especially subject to absorbing atmospheric moisture, then forming gums, solids, or two phases (a hydrocarbon phase floating on top of a water-alcohol phase). [ 22 ]
The presence of these degradation products in the fuel tank or fuel lines plus a carburetor or fuel injection components makes it harder to start the engine or causes reduced engine performance [ 23 ] On resumption of regular engine use, the buildup may or may not be eventually cleaned out by the flow of fresh gasoline. The addition of a fuel stabilizer to gasoline can extend the life of fuel that is not or cannot be stored properly, though removal of all fuel from a fuel system is the only real solution to the problem of long-term storage of an engine or a machine or vehicle. Typical fuel stabilizers are proprietary mixtures containing mineral spirits , isopropyl alcohol , 1,2,4-trimethylbenzene or other additives . Fuel stabilizers are commonly used for small engines, such as lawnmower and tractor engines, especially when their use is sporadic or seasonal (little to no use for one or more seasons of the year). Users have been advised to keep gasoline containers more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor. [ 11 ]
Gasoline stability requirements are set by the standard ASTM D4814. This standard describes the various characteristics and requirements of automotive fuels for use over a wide range of operating conditions in ground vehicles equipped with spark-ignition engines.
A gasoline-fueled internal combustion engine obtains energy from the combustion of gasoline's various hydrocarbons with oxygen from the ambient air, yielding carbon dioxide and water as exhaust. The combustion of octane , a representative species, performs the chemical reaction:
By weight, combustion of gasoline releases about 46.7 megajoules per kilogram (13.0 kWh /kg; 21.2 MJ/ lb ) or by volume 33.6 megajoules per liter (9.3 kWh/L; 127 MJ/U.S. gal; 121,000 BTU/U.S. gal), quoting the lower heating value . [ 24 ] Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 1.75 percent more or less than the average. [ 25 ] On average, about 74 liters (20 U.S. gal) of gasoline are available from a barrel of crude oil (about 46 percent by volume), varying with the quality of the crude and the grade of the gasoline. The remainder is products ranging from tar to naphtha . [ 26 ]
A high-octane-rated fuel, such as liquefied petroleum gas (LPG), has an overall lower power output at the typical 10:1 compression ratio of an engine design optimized for gasoline fuel. An engine tuned for LPG fuel via higher compression ratios (typically 12:1) improves the power output. This is because higher-octane fuels allow for a higher compression ratio without knocking, resulting in a higher cylinder temperature, which improves efficiency . Also, increased mechanical efficiency is created by a higher compression ratio through the concomitant higher expansion ratio on the power stroke, which is by far the greater effect. The higher expansion ratio extracts more work from the high-pressure gas created by the combustion process. An Atkinson cycle engine uses the timing of the valve events to produce the benefits of a high expansion ratio without the disadvantages, chiefly detonation, of a high compression ratio. A high expansion ratio is also one of the two key reasons for the efficiency of diesel engines , along with the elimination of pumping losses due to throttling of the intake airflow.
The lower energy content of LPG by liquid volume in comparison to gasoline is due mainly to its lower density. This lower density is a property of the lower molecular weight of propane (LPG's chief component) compared to gasoline's blend of various hydrocarbon compounds with heavier molecular weights than propane. Conversely, LPG's energy content by weight is higher than gasoline's due to a higher hydrogen -to- carbon ratio.
Molecular weights of the species in the representative octane combustion are 114, 32, 44, and 18 for C 8 H 18 , O 2 , CO 2 , and H 2 O, respectively; therefore one kilogram (2.2 lb) of fuel reacts with 3.51 kilograms (7.7 lb) of oxygen to produce 3.09 kilograms (6.8 lb) of carbon dioxide and 1.42 kilograms (3.1 lb) of water.
Spark-ignition engines are designed to burn gasoline in a controlled process called deflagration . However, the unburned mixture may autoignite by pressure and heat alone, rather than igniting from the spark plug at exactly the right time, causing a rapid pressure rise that can damage the engine. This is often referred to as engine knocking or end-gas knock. Knocking can be reduced by increasing the gasoline's resistance to autoignition , which is expressed by its octane rating. A detailed analysis further explores the conditions where premium fuel provides actual performance benefits versus when it is unnecessary. [ 27 ]
Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane ) and n- heptane . There are different conventions for expressing octane ratings, so the same physical fuel may have several different octane ratings based on the measure used. One of the best known is the research octane number (RON).
The octane rating of typical commercially available gasoline varies by country. In Finland , Sweden , and Norway , 95 RON is the standard for regular unleaded gasoline and 98 RON is also available as a more expensive option.
In the United Kingdom, over 95 percent of gasoline sold has 95 RON and is marketed as Unleaded or Premium Unleaded. Super Unleaded, with 97/98 RON and branded high-performance fuels (e.g., Shell V-Power, BP Ultimate) with 99 RON make up the balance. Gasoline with 102 RON may rarely be available for racing purposes. [ 28 ] [ 29 ] [ 30 ]
In the U.S., octane ratings in unleaded fuels vary between 85 [ 31 ] and 87 AKI (91–92 RON) for regular, 89–90 AKI (94–95 RON) for mid-grade (equivalent to European regular), up to 90–94 AKI (95–99 RON) for premium (European premium).
As South Africa's largest city, Johannesburg , is located on the Highveld at 1,753 meters (5,751 ft) above sea level, the Automobile Association of South Africa recommends 95-octane gasoline at low altitude and 93-octane for use in Johannesburg because "The higher the altitude the lower the air pressure, and the lower the need for a high octane fuel as there is no real performance gain". [ 32 ]
Octane rating became important as the military sought higher output for aircraft engines in the late 1920s and the 1940s. A higher octane rating allows a higher compression ratio or supercharger boost, and thus higher temperatures and pressures, which translate to higher power output. Some scientists [ who? ] even predicted that a nation with a good supply of high-octane gasoline would have the advantage in air power. In 1943, the Rolls-Royce Merlin aero engine produced 980 kilowatts (1,320 hp) using 100 RON fuel from a modest 27 liters (1,600 cu in) displacement. By the time of Operation Overlord , both the RAF and USAAF were conducting some operations in Europe using 150 RON fuel (100/150 avgas ), obtained by adding 2.5 percent aniline to 100-octane avgas. [ 33 ] By this time, the Rolls-Royce Merlin 66 was developing 1,500 kilowatts (2,000 hp) using this fuel.
Gasoline, when used in high- compression internal combustion engines, tends to auto-ignite or "detonate" causing damaging engine knocking (also called "pinging" or "pinking"). To address this problem, tetraethyl lead (TEL) was widely adopted as an additive for gasoline in the 1920s. With a growing awareness of the seriousness of the extent of environmental and health damage caused by lead compounds, however, and the incompatibility of lead with catalytic converters , governments began to mandate reductions in gasoline lead.
In the U.S., the Environmental Protection Agency issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, scheduled to begin in 1973 but delayed by court appeals until 1976. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales and under 1,800 metric tons (2,000 short tons; 1,800 long tons) of lead per year. From 1 January 1996, the U.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the U.S. The use of TEL also necessitated other additives, such as dibromoethane .
European countries began replacing lead-containing additives by the end of the 1980s, and by the end of the 1990s, leaded gasoline was banned within the entire European Union with an exception for Avgas 100LL for general aviation . [ 34 ] The UAE started to switch to unleaded in the early 2000s. [ 35 ]
Reduction in the average lead content of human blood may be a major cause for falling violent crime rates around the world [ 36 ] including South Africa. [ 37 ] A study found a correlation between leaded gasoline usage and violent crime (see Lead–crime hypothesis ). [ 38 ] [ 39 ] Other studies found no correlation.
In August 2021, the UN Environment Programme announced that leaded gasoline had been eradicated worldwide, with Algeria being the last country to deplete its reserves. UN Secretary-General António Guterres called the eradication of leaded petrol an "international success story". He also added: "Ending the use of leaded petrol will prevent more than one million premature deaths each year from heart disease, strokes and cancer, and it will protect children whose IQs are damaged by exposure to lead". Greenpeace called the announcement "the end of one toxic era". [ 40 ] However, leaded gasoline continues to be used in aeronautic, auto racing, and off-road applications. [ 41 ] The use of leaded additives is still permitted worldwide for the formulation of some grades of aviation gasoline such as 100LL , because the required octane rating is difficult to reach without the use of leaded additives.
Different additives have replaced lead compounds. The most popular additives include aromatic hydrocarbons , ethers ( MTBE and ETBE ), and alcohols , most commonly ethanol .
Lead replacement petrol (LRP) was developed for vehicles designed to run on leaded fuels and incompatible with unleaded fuels. Rather than tetraethyllead, it contains other metals such as potassium compounds or methylcyclopentadienyl manganese tricarbonyl (MMT); these are purported to buffer soft exhaust valves and seats so that they do not suffer recession due to the use of unleaded fuel.
LRP was marketed during and after the phaseout of leaded motor fuels in the United Kingdom, Australia , South Africa , and some other countries. [ vague ] Consumer confusion led to a widespread mistaken preference for LRP rather than unleaded, [ 42 ] and LRP was phased out 8 to 10 years after the introduction of unleaded. [ 43 ]
Leaded gasoline was withdrawn from sale in Britain after 31 December 1999, seven years after EEC regulations signaled the end of production for cars using leaded gasoline in member states. At this stage, a large percentage of cars from the 1980s and early 1990s which ran on leaded gasoline were still in use, along with cars that could run on unleaded fuel. However, the declining number of such cars on British roads saw many gasoline stations withdrawing LRP from sale by 2003. [ 44 ]
Methylcyclopentadienyl manganese tricarbonyl (MMT) is used in Canada and the U.S. to boost octane rating. [ 45 ] Its use in the U.S. has been restricted by regulations, although it is currently allowed. [ 46 ] Its use in the European Union is restricted by Article 8a of the Fuel Quality Directive [ 47 ] following its testing under the Protocol for the evaluation of effects of metallic fuel-additives on the emissions performance of vehicles. [ 48 ]
Gummy, sticky resin deposits result from oxidative degradation of gasoline during long-term storage. These harmful deposits arise from the oxidation of alkenes and other minor components in gasoline [ citation needed ] (see drying oils ). Improvements in refinery techniques have generally reduced the susceptibility of gasolines to these problems. Previously, catalytically or thermally cracked gasolines were most susceptible to oxidation. The formation of gums is accelerated by copper salts, which can be neutralized by additives called metal deactivators .
This degradation can be prevented through the addition of 5–100 ppm of antioxidants , such as phenylenediamines and other amines . [ 11 ] Hydrocarbons with a bromine number of 10 or above can be protected with the combination of unhindered or partially hindered phenols and oil-soluble strong amine bases, such as hindered phenols. "Stale" gasoline can be detected by a colorimetric enzymatic test for organic peroxides produced by oxidation of the gasoline. [ 49 ]
Gasolines are also treated with metal deactivators , which are compounds that sequester (deactivate) metal salts that otherwise accelerate the formation of gummy residues. The metal impurities might arise from the engine itself or as contaminants in the fuel.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion and allow easier starting in cold climates. High levels of detergent can be found in Top Tier Detergent Gasolines . The specification for Top Tier Detergent Gasolines was developed by four automakers: GM , Honda , Toyota , and BMW . According to the bulletin, the minimal U.S. EPA requirement is not sufficient to keep engines clean. [ 50 ] Typical detergents include alkylamines and alkyl phosphates at a level of 50–100 ppm. [ 11 ]
In the EU, 5 percent ethanol can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10 percent blending of ethanol (available in Finnish, French and German gasoline stations). In Finland, most gasoline stations sell 95E10, which is 10 percent ethanol, and 98E5, which is 5 percent ethanol. Most gasoline sold in Sweden has 5–15 percent ethanol added. Three different ethanol blends are sold in the Netherlands—E5, E10 and hE15. The last of these differs from standard ethanol–gasoline blends in that it consists of 15 percent hydrous ethanol (i.e., the ethanol–water azeotrope ) instead of the anhydrous ethanol traditionally used for blending with gasoline.
From 2009 to 2022, renewable percentage in gasoline slowly increased from 5% to 10%, even though EU-produced ethanol can achieve a climate-neutral production capability and most EU cars can use E10. E10 availability is low even in larger countries like Germany (26%) and France (58%). 8 countries in the EU have not adopted E10 as of 2024. [ 51 ]
The Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) requires gasoline for automobile use to have 27.5 percent of ethanol added to its composition. [ 52 ] Pure hydrated ethanol is also available as a fuel.
Australia uses both E10 (up to 10% ethanol) and E85 (up to 85% ethanol) in its gasoline. New South Wales mandated biofuel in its Biofuels Act 2007, and Queensland had a biofuel mandate since 2017. Fuel pumps must be clearly labeled with its ethanol/biodiesel content. [ 53 ]
The federal Renewable Fuel Standard (RFS) effectively requires refiners and blenders to blend renewable biofuels (mostly ethanol) with gasoline, sufficient to meet a growing annual target of total gallons blended. Although the mandate does not require a specific percentage of ethanol, annual increases in the target combined with declining gasoline consumption have caused the typical ethanol content in gasoline to approach 10 percent. Most fuel pumps display a sticker that states that the fuel may contain up to 10 percent ethanol, an intentional disparity that reflects the varying actual percentage. In parts of the U.S., ethanol is sometimes added to gasoline without an indication that it is a component.
In October 2007, the Government of India decided to make five percent ethanol blending (with gasoline) mandatory. Currently, 10 percent ethanol blended product (E10) is being sold in various parts of the country. [ 54 ] [ 55 ] Ethanol has been found in at least one study to damage catalytic converters. [ 56 ]
Though gasoline is a naturally colorless liquid, many gasolines are dyed in various colors to indicate their composition and acceptable uses. In Australia, the lowest grade of gasoline (RON 91) was dyed a light shade of red/orange, but is now the same color as the medium grade (RON 95) and high octane (RON 98), which are dyed yellow. [ 57 ] In the U.S., aviation gasoline ( avgas ) is dyed to identify its octane rating and to distinguish it from kerosene-based jet fuel, which is left colorless. [ 58 ] In Canada, the gasoline for marine and farm use is dyed red and is not subject to fuel excise tax in most provinces. [ 59 ]
Oxygenate blending adds oxygen -bearing compounds such as methanol , MTBE , ETBE , TAME , TAEE , ethanol , and biobutanol . The presence of these oxygenates reduces the amount of carbon monoxide and unburned fuel in the exhaust. In many areas throughout the U.S., oxygenate blending is mandated by EPA regulations to reduce smog and other airborne pollutants. For example, in Southern California fuel must contain two percent oxygen by weight, resulting in a mixture of 5.6 percent ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline, or, in the case of California, California reformulated gasoline (CARBOB). The federal requirement that RFG contain oxygen was dropped on 6 May 2006 because the industry had developed VOC -controlled RFG that did not need additional oxygen. [ 60 ]
MTBE was phased out in the U.S. due to groundwater contamination and the resulting regulations and lawsuits. Ethanol and, to a lesser extent, ethanol-derived ETBE are common substitutes. A common ethanol-gasoline mix of 10 percent ethanol mixed with gasoline is called gasohol or E10, and an ethanol-gasoline mix of 85 percent ethanol mixed with gasoline is called E85 . The most extensive use of ethanol takes place in Brazil , where the ethanol is derived from sugarcane . In 2004, over 13 billion liters (3.4 × 10 ^ 9 U.S. gal) of ethanol was produced in the U.S. for fuel use, mostly from corn and sold as E10. E85 is slowly becoming available in much of the U.S., though many of the relatively few stations vending E85 are not open to the general public. [ 61 ]
The use of bioethanol and bio-methanol, either directly or indirectly by conversion of ethanol to bio-ETBE, or methanol to bio-MTBE is encouraged by the European Union Directive on the Promotion of the use of biofuels and other renewable fuels for transport . Since producing bioethanol from fermented sugars and starches involves distillation , though, ordinary people in much of Europe cannot legally ferment and distill their own bioethanol at present (unlike in the U.S., where getting a BATF distillation permit has been easy since the 1973 oil crisis ).
The safety data sheet for a 2003 Texan unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts, including benzene (up to five percent by volume), toluene (up to 35 percent by volume), naphthalene (up to one percent by volume), trimethylbenzene (up to seven percent by volume), methyl tert -butyl ether (MTBE) (up to 18 percent by volume, in some states), and about 10 others. [ 62 ] Hydrocarbons in gasoline generally exhibit low acute toxicities, with LD50 of 700–2700 mg/kg for simple aromatic compounds. [ 63 ] Benzene and many antiknocking additives are carcinogenic .
People can be exposed to gasoline in the workplace by swallowing it, breathing in vapors, skin contact, and eye contact. Gasoline is toxic. The National Institute for Occupational Safety and Health (NIOSH) has also designated gasoline as a carcinogen. [ 64 ] Physical contact, ingestion, or inhalation can cause health problems. Since ingesting large amounts of gasoline can cause permanent damage to major organs, a call to a local poison control center or emergency room visit is indicated. [ 65 ]
Contrary to common misconception , swallowing gasoline does not generally require special emergency treatment, and inducing vomiting does not help, and can make it worse. According to poison specialist Brad Dahl, "even two mouthfuls wouldn't be that dangerous as long as it goes down to your stomach and stays there or keeps going". The U.S. CDC 's Agency for Toxic Substances and Disease Registry says not to induce vomiting, lavage , or administer activated charcoal . [ 66 ] [ 67 ]
Inhaled (huffed) gasoline vapor is a common intoxicant. Users concentrate and inhale gasoline vapor in a manner not intended by the manufacturer to produce euphoria and intoxication . Gasoline inhalation has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand, and some Pacific Islands. [ 68 ] The practice is thought to cause severe organ damage, along with other effects such as intellectual disability and various cancers . [ 69 ] [ 70 ] [ 71 ] [ 72 ]
In Canada, Native children in the isolated Northern Labrador community of Davis Inlet were the focus of national concern in 1993, when many were found to be sniffing gasoline. The Canadian and provincial Newfoundland and Labrador governments intervened on several occasions, sending many children away for treatment. Despite being moved to the new community of Natuashish in 2002, serious inhalant abuse problems have continued. Similar problems were reported in Sheshatshiu in 2000 and also in Pikangikum First Nation . [ 73 ] In 2012, the issue once again made the news media in Canada. [ 74 ]
Australia has long faced a petrol (gasoline) sniffing problem in isolated and impoverished aboriginal communities. Although some sources argue that sniffing was introduced by U.S. servicemen stationed in the nation's Top End during World War II [ 75 ] or through experimentation by 1940s-era Cobourg Peninsula sawmill workers, [ 76 ] other sources claim that inhalant abuse (such as glue inhalation) emerged in Australia in the late 1960s. [ 77 ] Chronic, heavy petrol sniffing appears to occur among remote, impoverished indigenous communities, where the ready accessibility of petrol has helped to make it a common substance for abuse.
In Australia, petrol sniffing now occurs widely throughout remote Aboriginal communities in the Northern Territory , Western Australia , northern parts of South Australia , and Queensland . [ 78 ] The number of people sniffing petrol goes up and down over time as young people experiment or sniff occasionally. "Boss", or chronic, sniffers may move in and out of communities; they are often responsible for encouraging young people to take it up. [ 79 ] In 2005, the Government of Australia and BP Australia began the usage of Opal fuel in remote areas prone to petrol sniffing. [ 80 ] Opal is a non-sniffable fuel (which is much less likely to cause a high) and has made a difference in some indigenous communities.
Gasoline is flammable with low flash point of −23 °C (−9 °F). Gasoline has a lower explosive limit of 1.4 percent by volume and an upper explosive limit of 7.6 percent. If the concentration is below 1.4 percent, the air-gasoline mixture is too lean and does not ignite. If the concentration is above 7.6 percent, the mixture is too rich and also does not ignite. However, gasoline vapor rapidly mixes and spreads with air, making unconstrained gasoline quickly flammable.
The exhaust gas generated by burning gasoline is harmful to both the environment and to human health. After CO is inhaled into the human body, it readily combines with hemoglobin in the blood, and its affinity is 300 times that of oxygen. Therefore, the hemoglobin in the lungs combines with CO instead of oxygen, causing the human body to be hypoxic , causing headaches, dizziness, vomiting, and other poisoning symptoms. In severe cases, it may lead to death. [ 81 ] [ 82 ] Hydrocarbons only affect the human body when their concentration is quite high, and their toxicity level depends on the chemical composition. The hydrocarbons produced by incomplete combustion include alkanes, aromatics, and aldehydes. Among them, a concentration of methane and ethane over 35 g/m 3 (0.035 oz/cu ft) will cause loss of consciousness or suffocation, a concentration of pentane and hexane over 45 g/m 3 (0.045 oz/cu ft) will have an anesthetic effect, and aromatic hydrocarbons will have more serious effects on health, blood toxicity, neurotoxicity , and cancer. If the concentration of benzene exceeds 40 ppm, it can cause leukemia, and xylene can cause headache, dizziness, nausea, and vomiting. Human exposure to large amounts of aldehydes can cause eye irritation, nausea, and dizziness. In addition to carcinogenic effects, long-term exposure can cause damage to the skin, liver, kidneys, and cataracts. [ 83 ] After NO x enters the alveoli, it has a severe stimulating effect on the lung tissue. It can irritate the conjunctiva of the eyes, cause tearing, and cause pink eyes. It also has a stimulating effect on the nose, pharynx, throat, and other organs. It can cause acute wheezing, breathing difficulties, red eyes, sore throat, and dizziness causing poisoning. [ 83 ] [ 84 ] Fine particulates are also dangerous to health. [ 85 ]
The air pollution in many large cities has changed from coal-burning pollution to "motor vehicle pollution". In the U.S., transportation is the largest source of carbon emissions, accounting for 30 percent of the total carbon footprint of the U.S. [ 86 ] Combustion of gasoline produces 2.35 kilograms per liter (19.6 lb/U.S. gal) of carbon dioxide, a greenhouse gas . [ 87 ] [ 88 ]
Unburnt gasoline and evaporation from the tank , when in the atmosphere , react in sunlight to produce photochemical smog . Vapor pressure initially rises with some addition of ethanol to gasoline, but the increase is greatest at 10 percent by volume. [ 89 ] At higher concentrations of ethanol above 10 percent, the vapor pressure of the blend starts to decrease. At a 10 percent ethanol by volume, the rise in vapor pressure may potentially increase the problem of photochemical smog. This rise in vapor pressure could be mitigated by increasing or decreasing the percentage of ethanol in the gasoline mixture. The chief risks of such leaks come not from vehicles, but gasoline delivery truck accidents and leaks from storage tanks. Because of this risk, most (underground) storage tanks now have extensive measures in place to detect and prevent any such leaks, such as monitoring systems (Veeder-Root, Franklin Fueling).
Production of gasoline consumes 1.5 liters per kilometer (0.63 U.S. gal/mi) of water by driven distance. [ 90 ]
Gasoline use causes a variety of deleterious effects to the human population and to the climate generally. The harms imposed include a higher rate of premature death and ailments, such as asthma , caused by air pollution , higher healthcare costs for the public generally, decreased crop yields , missed work and school days due to illness, increased flooding and other extreme weather events linked to global climate change , and other social costs. The costs imposed on society and the planet are estimated to be $3.80 per gallon of gasoline, in addition to the price paid at the pump by the user. The damage to the health and climate caused by a gasoline-powered vehicle greatly exceeds that caused by electric vehicles. [ 91 ] [ 92 ]
Gasoline can be released into the environment as an uncombusted liquid fuel, as a flammable liquid, or as a vapor by way of leakages occurring during its production, handling, transport and delivery. [ 93 ] Gasoline contains known carcinogens , [ 94 ] [ 95 ] [ 96 ] and gasoline exhaust is a health risk. [ 85 ] Gasoline is often used as a recreational inhalant and can be harmful or fatal when used in such a manner. [ 97 ] When burned, one liter (0.26 U.S. gal) of gasoline emits about 2.3 kilograms (5.1 lb) of CO 2 , a greenhouse gas , contributing to human-caused climate change . [ 98 ] [ 99 ] Oil products, including gasoline, were responsible for about 32% of CO 2 emissions worldwide in 2021. [ 100 ]
About 2.353 kilograms per liter (19.64 lb/U.S. gal) of carbon dioxide (CO 2 ) are produced from burning gasoline that does not contain ethanol. [ 88 ] Most of the retail gasoline now sold in the U.S. contains about 10 percent fuel ethanol (or E10) by volume. [ 88 ] Burning E10 produces about 2.119 kilograms per liter (17.68 lb/U.S. gal) of CO 2 that is emitted from the fossil fuel content. If the CO 2 emissions from ethanol combustion are considered, then about 2.271 kilograms per liter (18.95 lb/U.S. gal) of CO 2 are produced when E10 is combusted. [ 88 ]
Worldwide 7 liters of gasoline are burnt for every 100 km driven by cars and vans. [ 101 ]
In 2021, the International Energy Agency stated, "To ensure fuel economy and CO2 emissions standards are effective, governments must continue regulatory efforts to monitor and reduce the gap between real-world fuel economy and rated performance." [ 101 ]
Gasoline enters the environment through the soil, groundwater, surface water, and air. Therefore, humans may be exposed to gasoline through methods such as breathing, eating, and skin contact. For example, using gasoline-filled equipment, such as lawnmowers, drinking gasoline-contaminated water close to gasoline spills or leaks to the soil, working at a gasoline station, inhaling gasoline volatile gas when refueling at a gasoline station is the easiest way to be exposed to gasoline. [ 102 ]
The International Energy Agency said in 2021 that "road fuels should be taxed at a rate that reflects their impact on people's health and the climate". [ 101 ]
Countries in Europe impose substantially higher taxes on fuels such as gasoline when compared to the U.S. The price of gasoline in Europe is typically higher than that in the U.S. due to this difference. [ 103 ]
From 1998 to 2004, the price of gasoline fluctuated between $0.26 and $0.53 per liter ($1 and $2/U.S. gal). [ 104 ] After 2004, the price increased until the average gasoline price reached a high of $1.09 per liter ($4.11/U.S. gal) in mid-2008 but receded to approximately $0.69 per liter ($2.60/U.S. gal) by September 2009. [ 104 ] The U.S. experienced an upswing in gasoline prices through 2011, [ 105 ] and, by 1 March 2012, the national average was $0.99 per liter ($3.74/U.S. gal). California prices are higher because the California government mandates unique California gasoline formulas and taxes. [ 106 ]
In the U.S., most consumer goods bear pre-tax prices, but gasoline prices are posted with taxes included. Taxes are added by federal, state, and local governments. As of 2009 [update] , the federal tax was $0.049 per liter ($0.184/U.S. gal) for gasoline and $0.064 per liter ($0.244/U.S. gal) for diesel (excluding red diesel ). [ 107 ]
About nine percent of all gasoline sold in the U.S. in May 2009 was premium grade, according to the Energy Information Administration. Consumer Reports magazine says, "If [your owner's manual] says to use regular fuel, do so—there's no advantage to a higher grade." [ 108 ] The Associated Press said premium gas—which has a higher octane rating and costs more per gallon than regular unleaded—should be used only if the manufacturer says it is "required". [ 109 ] Cars with turbocharged engines and high compression ratios often specify premium gasoline because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation. [ 110 ] The price of gasoline varies considerably between the summer and winter months. [ 111 ]
There is a considerable difference between summer oil and winter oil in gasoline vapor pressure (Reid Vapor Pressure, RVP), which is a measure of how easily the fuel evaporates at a given temperature. The higher the gasoline volatility (the higher the RVP), the easier it is to evaporate. The conversion between the two fuels occurs twice a year, once in autumn (winter mix) and the other in spring (summer mix). The winter blended fuel has a higher RVP because the fuel must be able to evaporate at a low temperature for the engine to run normally. If the RVP is too low on a cold day, the vehicle will be difficult to start; however, the summer blended gasoline has a lower RVP. It prevents excessive evaporation when the outdoor temperature rises, reduces ozone emissions, and reduces smog levels. At the same time, vapor lock is less likely to occur in hot weather. [ 112 ]
Below is a table of the energy density (per volume) and specific energy (per mass) of various transportation fuels as compared with gasoline. In the rows with gross and net , they are from the Oak Ridge National Laboratory 's Transportation Energy Data Book. [ 114 ]
Chevron published a free high-quality technical guide Motor Gasolines Technical Review using common language that explains gasoline production, blending, and combustion in an engine. The report covers the US and other locations globally. | https://en.wikipedia.org/wiki/Gasoline |
Gastric electrical stimulation , also known as implantable gastric stimulation , is the use of specific devices to provide electrical stimulation to the stomach to try to bring about weight loss in those who are overweight or improve gastroparesis . [ 1 ] [ 2 ]
Gastric electrical stimulation is a pacemaker -like device with electrical connections to the surface of the stomach . The device works by disrupting of the motility cycle or stimulating enteric nervous system . There are a number of different devices on the market including Transend, Maestro, and Diamond. [ 1 ]
These devices are for treatment of gastroparesis . The best available evidence, however, find that they are of questionable utility for this condition. [ 2 ]
As of 2017 it is not approved for use for obesity in the United States. [ 3 ] The first studies done did not find a benefit, however, research is ongoing . [ 4 ]
Once food leaves the stomach and enters the duodenum , the gut-brain-liver axis is activated, which involves signaling between the gastrointestinal tract and the nervous system. For patients without type 2 diabetes , the gastric transit time of food is estimated to be 30–45 minutes (the time from food ingestion to food leaving the stomach into the duodenum). In type 2 diabetes, the neurohormonal communication system is impaired. Delayed signaling within the gut-brain-liver axis leads to high blood glucose concentration after meals. [ 5 ]
There are approximately 4,000 gastric pacer surgeries a year in the United States.
The Diamond system first received CE mark in 2007 and is approved for sale in Europe, Australia, and Hong Kong. [ 6 ] It is not approved in the United States for obesity. | https://en.wikipedia.org/wiki/Gastric_electrical_stimulation |
The gastric mucosa is the mucous membrane layer of the stomach , which contains the gastric pits , to which the gastric glands empty. In humans, it is about one mm thick, and its surface is smooth, soft, and velvety. It consists of simple secretory columnar epithelium , an underlying supportive layer of loose connective tissue called the lamina propria , and the muscularis mucosae , a thin layer of muscle that separates the mucosa from the underlying submucosa.
In its fresh state, it is of a pinkish tinge at the pyloric end and of a red or reddish-brown color over the rest of its surface. In infancy it is of a brighter hue, the vascular redness being more marked.
It is thin at the cardiac extremity, but thicker toward the pylorus. During the contracted state of the stomach it is thrown into numerous folds or rugae , which, for the most part, have a longitudinal direction. They are most marked toward the pyloric end of the stomach, and along the greater curvature , and are entirely obliterated when the organ becomes distended .
When examined with a lens, the inner surface of the mucous membrane presents a peculiar honeycomb appearance from being covered with funnel-like polygonal or hexagonal depressions which vary from 0.12 to 0.25 mm. in diameter. These are the ducts of the gastric glands , at the bottom of each may be seen one or more minute openings of the gland tubes. Gastric glands are simple or branched tubular glands that emerge on the deeper part of the gastric pits , and outlined by the folds of the mucosa.
The gastric glands in the cardiac region of the stomach are known as cardiac glands. In the pyloric region the glands are known as pyloric glands, and in the rest of the stomach they are called gastric glands. [ 1 ]
Several types of endocrine cells are found in the gastric glands. The pyloric glands contain gastrin -producing cells ( G cells ); this hormone stimulates acid production from the parietal cells. Enterochromaffin-like cells (ECLs), found in the oxyntic glands release histamine , which also is a powerful stimulant of the acid secretion.
The surface of the mucous membrane is covered by a single layer of columnar epithelium . This epithelium commences very abruptly at the cardiac orifice , where there is a sudden transition from the stratified epithelium of the esophagus . The epithelial lining of the gland ducts is of the same character and is continuous with the general epithelial lining of the stomach.
The sodium-iodide symporter (SIP) is expressed in all the surface mucous cells (at the basolateral membrane) but not in the mucous neck cells. SIP mediates the transport of iodide from the bloodstream and secretes it into the gastric lumen where it is taken up in the gastric juice. Its role is not known but it has been shown to be absent in gastric cancer. [ 2 ]
This article incorporates text in the public domain from page 1166 of the 20th edition of Gray's Anatomy (1918) | https://en.wikipedia.org/wiki/Gastric_mucosa |
The gastrocolic reflex or gastrocolic response is a physiological reflex that controls the motility , or peristalsis , of the gastrointestinal tract following a meal. It involves an increase in motility of the colon consisting primarily of giant migrating contractions , in response to stretch in the stomach following ingestion and byproducts of digestion entering the small intestine . [ 1 ] The reflex propels existing intestinal contents through the digestive system helps make way for ingested food, and is responsible for the urge to defecate following a meal. [ 2 ]
An increase in electrical activity is seen as little as 15 minutes after eating. The gastrocolic reflex is unevenly distributed throughout the colon, with the sigmoid colon exhibiting a greater phasic response to propel food distally into the rectum ; however, the tonic response across the colon is uncertain. [ 1 ] Increased pressure within the rectum acts as stimulus for defecation. [ 1 ] [ 3 ] Small intestine motility is also increased in response to the gastrocolic reflex. [ 2 ]
These contractions are generated by the muscularis externa stimulated by the myenteric plexus . [ 1 ] A number of neuropeptides have been proposed as mediators of the gastrocolic reflex. These include serotonin , neurotensin , cholecystokinin , prostaglandin E1 , and gastrin . [ 1 ] [ 3 ]
Clinically, the gastrocolic reflex has been implicated in pathogenesis of irritable bowel syndrome (IBS): the very act of eating or drinking can provoke an overreaction of the gastrocolic response in some patients with IBS due to their heightened visceral sensitivity, and this can lead to abdominal pain and distension , flatulence , and diarrhea . [ 4 ] [ 1 ] The gastrocolic reflex has also been implicated in pathogenesis of functional constipation , where patients with spinal cord injury and diabetics with gastroparesis secondary to diabetic neuropathy have an increased colonic transit time . [ 1 ]
The gastrocolic reflex can also be used to optimise the treatment of constipation. Since the reflex is most active in the mornings and immediately after meals, consumption of stimulant laxatives , such as sennosides and bisacodyl , during these times will augment the reflex and help increase colonic contractions and therefore defecation. [ 1 ]
This human digestive system article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gastrocolic_reflex |
The gastroileal reflex is one of the three extrinsic reflexes of the gastrointestinal tract , the other two being the gastrocolic reflex and the enterogastric reflex . The gastroileal reflex is stimulated by the presence of food in the stomach and gastric peristalsis. Initiation of the reflex causes peristalsis in the ileum and the opening of the ileocecal valve (which allows the emptying of the ileal contents into the large intestine, or colon). [ 1 ] This in turn stimulates colonic peristalsis and an urge to defecate.
This gastroenterology article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gastroileal_reflex |
Gastruloids are three dimensional aggregates of embryonic stem cells (ESCs) that, when cultured in specific conditions, exhibit an organization resembling that of an embryo. They develop with three orthogonal axes and contain the primordial cells for various tissues derived from the three germ layers, without the presence of extraembryonic tissues. Notably, they do not possess forebrain , midbrain , and hindbrain structures. Gastruloids serve as a valuable model system for studying mammalian development, including human development, as well as diseases associated with it. They are a model system an embryonic organoid for the study of mammalian development (including humans) and disease. [ 1 ] [ 2 ] [ 3 ]
The Gastruloid model system draws its origins from work by Marikawa et al. . [ 4 ] In that study, small numbers of mouse P19 embryonal carcinoma (EC) cells , were aggregated as embryoid bodies (EBs) and used to model and investigate the processes involved in anteroposterior polarity and the formation of a primitive streak region. [ 4 ] In this work, the EBs were able to organise themselves into structures with polarised gene expression, axial elongation/organisation and up-regulation of posterior mesodermal markers. This was in stark contrast to work using EBs from mouse ESCs, which had shown some polarisation of gene expression in a small number of cases but no further development of the multicellular system. [ 5 ] [ 6 ]
Following this study, the Martinez Arias laboratory in the Department of Genetics at the University of Cambridge demonstrated how aggregates of mouse embryonic stem cells (ESCs) were able to generate structures that exhibited collective behaviours with striking similarity to those during early development such as symmetry-breaking (in terms of gene expression), axial elongation and germ-layer specification. [ 1 ] [ 2 ] [ 3 ] To quote from the original paper: "Altogether, these observations further emphasize the similarity between the processes that we have uncovered here and the events in the embryo. The movements are related to those of cells in gastrulating embryos and for this reason we term these aggregates ‘gastruloids’". As noted by the authors of this protocol, a crucial difference between this culture method and previous work with mouse EBs was the use of small numbers of cells which may be important for generating the correct length scale for patterning, and the use of culture conditions derived from directed differentiation of ESCs in adherent culture [ 1 ] [ 7 ] [ 3 ] [ 2 ] [ 8 ] [ 9 ]
Brachyury (T/Bra) , a gene which marks the primitive streak and the site of gastrulation, is up-regulated in the Gastruloids following a pulse of the Wnt/β-Catenin agonist CHIR99021 [ 10 ] (Chi; other factors have also been tested [ 1 ] ) and becomes regionalised to the elongating tip of the Gastruloid. From or near the region expressing T/Bra, cells expressing the mesodermal marker tbx6 are extruded from the similar to cells in the gastrulating embryo; it is for this reason that these structures are called Gastruloids. [ 1 ]
Further studies revealed that the events that specify T/Bra expression in gastruloids mimic those in the embryo. [ 2 ] After seven days gastruloids exhibit an organization very similar to a midgestation embryo with spatially organized primordia for all mesodermal (axial, paraxial, intermediate, cardiac, cranial and hematopoietic) and endodermal derivatives as well as the spinal cord. [ 11 ] [ 12 ] [ 3 ] They also implement Hox gene expression with the spatiotemporal coordinates as the embryo. [ 3 ] Gastruloids lack brain as well as extraembryonic tissues but characterisation of the cellular complexity of gastruloids at the level of single cell and spatial transcriptomics, reveals that they contain representatives of the three germ layers including neural crest, Primordial Germ cells and placodal primordia. [ 13 ] [ 14 ]
A feature of gastruloids is a disconnect between the transcriptional programs and outlines and the morphogenesis. However, changes in the culture conditions can elicit morphogenesis, most significantly gastruloids have been shown to form somites [ 14 ] [ 13 ] and early cardiac structures. [ 15 ] In addition, interactions between gastruloids and extraembryonic tissues promote an anterior, brain-like polarised tissue. [ 16 ]
Gastruloids have recently been obtained from human ESCs, [ 17 ] which gives developmental biologists the ability to study early human development without needing human embryos. Importantly though, the human gastruloid model is not able to form a human embryo, meaning that is a non-intact, non-viable and non-equivalent to in vivo human embryos.
The term Gastruloid has been expanded to include self-organised human embryonic stem cell arrangements on patterned (micro patterns) that mimic early patterning events in development; [ 18 ] [ 19 ] these arrangements should be referred to as 2D gastruloids. | https://en.wikipedia.org/wiki/Gastruloid |
A gasworks or gas house is an industrial plant for the production of flammable gas. Many of these have been made redundant in the developed world by the use of natural gas , though they are still used for storage space.
Coal gas was introduced to Great Britain in the 1790s as an illuminating gas by the Scottish inventor William Murdoch . [ 1 ]
Early gasworks were usually located beside a river or canal so that coal could be brought in by barge . Transport was later shifted to railways and many gasworks had internal railway systems with their own locomotives.
Early gasworks were built for factories in the Industrial Revolution from about 1805 as a light source and for industrial processes requiring gas, and for lighting in country houses from about 1845. Country house gas works are extant at Culzean Castle in Scotland and Owlpen in Gloucestershire .
A gasworks was divided into several sections for the production, purification and storage of gas.
This contained the retorts in which coal was heated to generate the gas. The crude gas was siphoned off and passed on to the condenser . The waste product left in the retort was coke . In many cases the coke was then burned to heat the retorts or sold as smokeless fuel.
This consisted of a bank of air-cooled gas pipes over a water-filled sump. Its purpose was to remove tar from the gas by condensing it out as the gas was cooled. Occasionally the condenser pipes were contained in a water tank similar to a boiler but operated in the same manner as the air-cooled variant. The tar produced was then held in a tar well/tank which was also used to store liquor .
An impeller or pump was used to increase the gas pressure before scrubbing. Exhausters were optional components and could be placed anywhere along the purifying process but were most often placed after the condensers and immediately before the gas entered the gas holders.
A sealed tank containing water through which the gas was bubbled. This removed ammonia and ammonium compounds. The water often contained dissolved lime to aid the removal of ammonia. The water left behind was known as ammonical liquor . Other versions used consisted of a tower, packed with coke, down which water was trickled.
Also known as an Iron Sponge, this removed hydrogen sulfide from the gas by passing it over wooden trays containing moist ferric oxide . The gas then passed on to the gasholder and the iron sulfide was sold to extract the sulfur. Waste from this process often gave rise to blue billy , a ferrocyanide contaminant in the land which causes problems when trying to redevelop an old gasworks site.
Often only used at large gasworks sites, a benzole plant consisted of a series of vertical tanks containing petroleum oil through which the gas was bubbled. The purpose of a benzole plant was to extract benzole from the gas. The benzole dissolved into the petroleum oil was run through a steam separating plant to be sold separately.
The gas holder or gasometer was a tank used for storage of the gas and to maintain even pressure in distribution pipes. The gas holder usually consisted of an upturned steel bell contained within a large frame that guided it as it rose and fell depending on the amount of gas it contained. [ 2 ]
The by-products of gas-making, such as coke , coal tar , ammonia and sulfur had many uses. For details, see coal gas .
Coal gas is no longer made in the UK but many gasworks sites are still used for storage and metering of natural gas and some of the old gasometers are still in use. Fakenham gasworks dating from 1846 is the only complete, non-operational gasworks remaining in England. Other examples exist at Biggar in Scotland and Carrickfergus in Northern Ireland .
Gasworks were noted for their foul smell and generally located in the poorest metropolitan areas. Cultural remnants of gasworks include many streets named Gas Street or Gas Avenue and groups or gangs known as Gas House Gang , such as the 1934 St. Louis Cardinals baseball team. The 1946 film Gas House Kids features children from New York's Gas House District taking on a gang, and spawned two sequels. Ewan McColl 's 1968 song " Dirty Old Town " (about his home town of Salford ) famously begins "Found my love by the gaswork croft …" (in cover versions often "I met my love by the gasworks wall…") [ 3 ]
Fans of Bristol Rovers F.C. in south west England are known as ‘Gas-Heads’ due to the proximity of gasometers near to their original ground at Eastville in Bristol. Bristol Rovers F.C. is also known as ‘The Gas’.
Gas was used for many years to illuminate the interior of railway carriages. The New South Wales Government Railways manufactured its own oil-gas for this purpose, together with reticulated coal-gas to railway stations and associated infrastructure. Such works were established at the Macdonaldtown Carriage Sheds , Newcastle , Bathurst , Junee and Werris Creek . These plants followed on from the works of a private supplier which the railway took over in 1884.
Gas was also transported in special travelling gas reservoir wagons from the gasworks to stationary reservoirs located at a number of country stations where carriage reservoirs were replenished.
With the spreading conversion to electric power for lighting buildings and carriages during the 1920s and 1930s, the railway gasworks were progressively decommissioned. [ 4 ]
The Gasworks Newstead site in Brisbane Australia has been a stalwart of the river's edge since its development in 1863. By 1890, the works were supplying gas to Brisbane streets from Toowong to Hamilton [ 5 ] : 7 and over the next 100 years, it would grow to supply Brisbane city with the latest in gas technology until it was decommissioned in 1996.
In March 1866, the Queensland Defence Force placed an official request for town gas connection, evidence of the vital role the gasworks played in the economic development of colonial Brisbane. [ 6 ] : 9 In fact, the gasworks were considered to be of such importance, that during World War II, genuine fears of attack from Japanese air raids motivated the installation of anti aircraft guns which vigilantly watched over the plant and its employees throughout the war. [ 6 ] : 10
The site itself has been synonymous with economic growth and benefit to Brisbane and Queensland with the success of the gasworks facilitating further development of the Newstead/Teneriffe area to include the James Hardie fibro-cement manufacturing plant, Shell Oil plant, Brisbane Water and Sewerage Depot and even the “Brisbane Gas Company Cookery School” which operated in the 1940s. In 1954, a carbonizing plant was built, giving Brisbane the "most modern gas producing plant in Australia", [ 6 ] : 10 consuming 100 tonnes of coal every eight hours.
During its golden years in the late 19th and early 20th centuries, the site also played a vital role in providing employment to aboriginal Australians and many migrant workers arriving there from Europe after the second World War.
The fine tradition of the Brisbane Gasworks economic and employment-based successes will not be lost or forgotten with the Teneriffe Gasworks Village Development paying homage to the sites history and integrity in its pending urban development.
The gasholder structure at this site is set to become a hub of a new property development on the site – keeping the structural integrity of the pig iron structure. It will be a true reflection of urban renewal embracing its industrial past. [ 5 ] [ 6 ]
Located in South Dunedin , New Zealand , the Dunedin Gasworks Museum consists of a conserved engine house featuring a working boiler house, fitting shop and collection of five stationary steam engines. There are also displays of domestic and industrial gas appliances.
Located in Athens, Greece Technopolis (Gazi) is a gasworks converted to an exhibition space.
The Gas Museum in Leicester, UK, is operated by The National Gas Museum Trust .
Gas Works Park is a public park in Seattle, Washington .
The Warsaw Gasworks Museum is a museum in Warsaw, Poland .
The Museo dell'Acqua e del Gas is a museum in Genoa, Italy.
It is located in the industrial area of the IREN Archived 14 December 2021 at the Wayback Machine company, an Italian multi-utility, where coal gas has been produced till 1972.
The small Museum, managed by Fondazione AMGA , hosts a rich collection of industrial finds, related to water and gas works history.
Hasanpaşa Gasworks is an 1892-built gasworks in Istanbul , Turkey, which was redeveloped into a museum in 2021.
Photos of Fakenham Gas Works | https://en.wikipedia.org/wiki/Gasworks |
A gas–liquid contactor is a particular chemical equipment used to realize the mass and heat transfer between a gas phase and a liquid phase. Gas–liquid contactors can be used in separation processes (e.g. distillation , absorption ) or as gas–liquid reactors or to achieve both purposes within the same device (e.g. reactive distillation ).
They are divided into two main categories: [ 1 ]
Examples of differential gas–liquid contactors are:
Examples of stagewise gas–liquid contactors are:
Some important factors to take into account to choice the typology of gas–liquid contactor more suitable for a particular application are:
In particular heat and mass transfer velocity is higher for equipment with higher values of gas–liquid interface surface area, so gas–liquid contactors with high surface area (e.g. packed column, spray tower) are often preferred when it is important to lower the cost of the equipment.
Liquid hold-up is also an important factor for the economy of the process, because for low values of liquid hold-up a bigger equipment is needed to have the same heat and mass transfer velocity. For this reason, gas–liquid contactors with low liquid-hold-up (e.g. falling-film column) in general are not used at industrial scale. | https://en.wikipedia.org/wiki/Gas–liquid_contactor |
In the upstream oil industry , a gas–oil separation plant (GOSP) is temporary or permanent facilities that separate wellhead fluids into constituent vapor (gas) and liquid (oil and produced water) components.
Temporary gas–oil separation facilities are associated with newly drilled or newly sidetracked wells where the production potential of the well is being assessed. [ 1 ] The plant, comprising a test separator vessel, is connected to the wellhead after the choke valve . The separator allows the fluids to separate by gravity into its component phases: solids such as sand (the densest phase) settle to the bottom of the separator, then produced water and oil which are drawn separately from the base of the separator, and vapor or gas (the lightest phase) separates to the top of the separator vessel from where it is withdrawn. [ 2 ] Each of the three fluid phases is metered to determine the relative flow-rates of the components and production potential of the well. [ 1 ] In temporary facilities the vapor is generally flared; produced water is disposed of overboard after treatment to reduce its oil content to statutory levels; and the crude oil phase may be diverted to tote tanks for removal and treatment onshore. Alternatively, if the temporary GOSP plant is associated with a permanent production facility, the oil phase may be treated in the installation's permanent gas–oil separation plant. [ 3 ]
Permanent gas–oil separation plant is associated with permanent offshore production facilities. For a full description of such a plant, see Oil production plant . [ 3 ]
A gas–oil–and–water separator is called a 3-phase separator. [ 4 ]
The gas and oil or condensate are pumped through designated pipelines, while the sand and other solids are washed from the separator and disposed of overboard.
Water need not be separated, and a single liquid (oil and water) phase produced together with a separate gas phase. Chemicals are added so that the crude and water emulsify. This process is then reversed at the storage and processing facility by adding demulsifiers that make the water separate out, and is drawn from the bottom of the tank.
After storage, the crude oil can be sold to refineries, which produce fuels, chemicals, and energy products.
The well fluids at the wellhead are at high pressure. Production pressures of greater than 23,000 pounds per square inch (1,600 atm) are not uncommon, but typically are lower than this. [ 2 ] The high pressure is reduced at the choke valve to typically 7 to 30 bar at the separator, although the first stage separator could operate at higher pressure c. 250 bar. [ 2 ] Modern oil recovery practice may place a hydro-cyclone to replace the temporary GOSP, allowing the water to be removed immediately and re-injected into the reservoir. The hydro-cyclone will vary the flows according to the water content and can also separate condensate from the gas where separate storage and export can be provided for the products close to the production well (e.g. on offshore platforms).
Crude oil leaving the well may contain quantities of sulfur (e.g. hydrogen sulfide and thiols ) and/or carbon dioxide, and is known as "sour" crude. The gas–oil separator will typically partition the hydrogen sulfide and carbon dioxide preferentially into the vapor or gas phase, where it may be further treated. [ 3 ] The most usual "crude sweetening packages" use amines to remove the sulfur and CO 2 content. Crude that contains water is called "wet", and the water can then be bound in an emulsion in the crude to allow pumping through a pipeline. The crude is processed and treated to make it acceptable for the entry and transportation specification of the pipeline, before it can be transported to a refinery for processing. [ 5 ]
It is often appropriate to separate gases and liquids for separate processing. This also involves the separation of oily and water liquid phases.
In the past, and in some places today, the gas is considered a waste product and was flared off (burned). Collecting the gas reduces carbon emissions, and produces a marketable commodity. | https://en.wikipedia.org/wiki/Gas–oil_separation_plant |
A gate in cytometry is a set of value limits (boundaries) that serve to isolate a specific group of cytometric events from a large set. Gates can be defined by discrimination analysis, or can simply be drawn around a given set of data points on a printout and then converted to a computer-useful form. Gates can be implemented with a physical blinder. Gates may be used either to selectively gather data or to segregate data for analysis.
Gates are divided mathematically into inclusive gates and exclusive gates. Inclusive gates select data that falls within the limits set, while exclusive gates select data that falls outside the limits.
A live gate is a term used for a process that prevents the acquisition by the computer of non-selected data from the flow cytometer . | https://en.wikipedia.org/wiki/Gate_(cytometry) |
Gated drug delivery systems are a method of controlled drug release that center around the use of physical molecules that cover the pores of drug carriers until triggered for removal by an external stimulus. Gated drug delivery systems are a recent innovation in the field of drug delivery and pose as a promising candidate for future drug delivery systems that are effective at targeting certain sites without having leakages or off target effects in normal tissues. This new technology has the potential to be used in a variety of tissues over a wide range of disease states and has the added benefit of protecting healthy tissues and reducing systemic side effects. [ 1 ]
Gated drug delivery systems are an emerging concept that have drawn a lot of attention for their wide variety of potential applications in the medical field. The abnormal physiological conditions found within the tumor environment provide a breadth of options that could be used for externally stimulating these systems to release cargo. Gated systems in cancer therapy also have the added effect of reducing off target effects and decreasing leakage and delivery of drug to normal tissues . Another use for this technology could also be antibacterial regulation. These systems could be used to limit bacterial resistance as well as accumulation of antibiotics within the body. Antibacterial regulation potentially opens the door to using gated systems in theranostics , in which the system is able to detect an issue and then provide a therapeutic response. [ 2 ]
There is also the potential for inhalable pulmonary drug delivery . [ 3 ] With an increase in respiratory disease cases, the need for a drug delivery system that can be targeted to the lungs and provide sustained release is becoming more severe. This type of system would be applicable to patients experiencing asthma , pneumonia , obstructive pulmonary disease , and a number of other lung related diseases. [ 4 ]
The history of gated drug delivery systems starts in the mid-1960s when the concept of zero order controlled drug delivery was first thought of. Researchers raced to be able to find a drug delivery platform that would be able to have perfectly sustained drug release . These efforts were initially on the macroscopic level with some of the first controlled drug delivery (CDD) devices being an ophthalmic insert , an intrauterine device , and a skin patch . [ 5 ] In the 1970s the drug delivery field shifted from macroscopic systems and started to delve into microscopic systems . Ideas such as steroid loaded poly (lactic-co-glycolic acid), PLGA , microparticles came into existence. The next major jump came in the 1980s in the form of nanotherapeutics . There were some major technological advances that allowed this next generation of drug delivery systems to come along. Those ideas were PEGylation , active targeting, and the enhanced permeation and retention effect (EPR). [ 5 ]
Some of the issues that had been seen with earlier renditions of nanoparticle drug delivery was that there were off target effects from drug being delivered to normal tissue, the delivery system wasn't highly controllable, and there wasn't optimal accumulation of drug in the targeted area. [ 6 ] This is when the development of "smart drug delivery" originated. Encapsulated within the idea of smart drug delivery is the use of gated delivery systems. Researchers discovered that certain materials could be loaded and capped to prevent premature drug release. The caps could subsequently be removed using different external stimuli. This created a class of drug delivery systems that were able to solve a number of problems exhibited by normal nanoparticle drug delivery systems. These smart drug delivery systems are able to deliver the drug with minimal leakage, can be actively or passively targeted to different areas within the body, and will only release drug in the presence of certain triggers, creating a sustained local response and accumulation of drug at the disease area. [ 6 ]
There are many different materials and fabrication methods that can be used to produce gated drug delivery scaffolding. In general, porous materials, such as mesoporous silica nanoparticles are used because of their expansive surface area, large loading capacity, and porous structures. [ 2 ] These characteristics make it possible to load a variety of molecules that vary greatly in size.
Mesoporous silica nanoparticles (MSN) are considered to be one of the most widely used systems for drug delivery. MSN's have some of the characteristic features of gated systems such as being porous and having a high loading capacity, but they also exhibit some special features such as increased biocompatibility and chemical inertness . [ 7 ] These delivery systems are composed of two parts: the inorganic scaffold and the molecular gates. In a study conducted by the Kong Lab at Deakin University in Australia, the researchers generated MSN's by adding tetraethyl orthosilicate to aqueous cetyltrimethylammonium bromide . [ 8 ] The MSN's they created had a surface area of 363 m^2/g, an average pore size of 2.59 nm, and a pore volume of 0.33 cm^3/g. [ 8 ]
Mesoporous carbon nanoparticles (MCN) are similar to MSN's. They have a similar structure and share key physical properties and characteristics. However, it has been found that MCN's can exhibit lower toxicity that MSN's. To date, not much research has been done on MCN's. The Du lab based in Nanjing , China took made MSN templates using the common method of combining CTAB and TEOS. The researchers then took the MSN templates and dispersed them in a glucose solution followed by autoclaving the mixture to produce a reaction. The product was then subjected to carbonization at 900 degrees Celsius and the MCN's were generated. [ 9 ] The researchers found that MCN's had a surface area of 1575 m^2/g, a pore size of 2.2 nm, and an average diameter of 115 nm. [ 9 ]
There is a number of external triggers that can be used to release cargo on gated delivery systems. Examples of some triggers include pH, redox, enzyme, light, temperature, magnetic, ultrasound, and small molecule responsive gated systems.
One of the most common triggers for drug delivery systems is pH . This stimulus is abundantly used in cancer therapies due to the fact that the tumor microenvironment is acidic. The development of pH triggered systems meant that drug could be introduced to the body but not be deployed until encountering the tumor microenvironment. Hence a possible and probable reason that pH triggered systems are so common. There are a few approaches to making these systems. One method is using linkages that dissolve at certain pH levels. As the system enters an acidic environment, the linkages that hold that gates onto the porous scaffold are hydrolyzed and the cargo can be released. [ 7 ] Examples of pH linkages are imine , amides , esters , and acetals . [ 7 ] Another method that can be used is protonation . This method relies on electrostatic interactions between the gate molecule and the porous scaffold. The two will be linked together with a certain molecule, for example, acetylated carboxymethyl . When the system reaches an acidic environment, protonation of the molecule is initiated. The protonation causes a disruption in the linkage and the cargo can be released. [ 7 ]
Redox reactions are also used for gated delivery systems. Within cells and the bloodstream there are several reducing agents that can be used to trigger drug release in gated systems. The most common reducing agent used in gated delivery system is glutathione (GSH) because it has been determined that GSH is the most abundant reducing agent in the body. [ 1 ] GSH also has significantly different concentrations between the intracellular and extracellular environments making it easier to target either environment without getting triggered by the other. [ 1 ] Furthermore, GSH is found in higher concentration within tumor cells. [ 1 ] This provides another way to have sustained and local release of drug at tumor sites. There are generally 2 different mechanisms for this type of gated system. One method is to cleave disulfide bonds . Another method is to cleave bonds through the use of reactive oxygen species (ROS). Bonds that are able to be cleaved by ROS are generally thioketals , ketals , and diselenides . [ 7 ]
Enzyme responsive gated materials are another class of gated delivery systems. In these scenarios, enzymes can trigger release of the gates from the scaffolds in drug delivery systems. The mechanism for this type of gate is that certain linkages are used that can be hydrolyzed by select enzymes. The two most popular choices are protease and hyaluronidase . An advantage of using enzyme responsive triggers is that there is a large amount of substrate specificity , and the enzymes are able to trigger their target with high selectivity, even under mild conditions. [ 6 ] Another advantage of this system is that enzymes are found throughout the entire body and work on almost all biological processes so the delivery system could potentially be activated in any part of the body during many points within a singular process. [ 6 ] One study done by the Martinez-Manez lab in Valencia , Spain aimed to generate MSNs linked to poly-l-glutamic acid (PGA) gates through peptide bonds . The trigger for this system was the presence of a lysosomal proteolytic enzyme (protease), in this case, pronase . The researchers found that in the absence of pronase, the system was only able to release less than 20% of its cargo in 24 hours, however, in the presence of pronase, there was a 90% release of cargo within 5 hours. [ 10 ]
Within the topic of gated drug delivery systems, utilizing magnetic forces generally goes hand in hand with temperature stimulus. The phenomenon of magnetic hyperthermia is when superparamagnetic nanoparticles reorient themselves after being exposed to heat generated by an alternating magnetic field (AMF). This concept has been utilized within the drug delivery field wherein gatekeepers are magnetically linked to the scaffolding and upon the application of heat, reorient and allow for the release of drug. [ 7 ] This particular method has not been researched as heavily given the drawback that high energy is needed to produce the AMF and uncap the system. However, the Vallet-Regi lab based in Madrid , Spain decided to investigate the possibility of using magnetic gates bound to the scaffold using DNA. The lab generated oligonucleotide -modified superparamagnetic mesoporous silica nanoparticles. They capped the scaffolding using iron oxide nanoparticles that carried complementary DNA to the scaffold's oligonucleotide sequence. What the lab found was that they were able to cap their system due to the DNA coming together and creating a double strand. Upon heating the system using an AMF, the DNA bonds detached, the system became uncapped, and the drug was able to be released. [ 11 ] Furthermore, the lab found that this linkage was reversible. As temperature was reduced, the DNA was able to re-link to its complementary half. This study was able to illustrate the possibility of having a drug delivery system that could be remotely triggered and exhibit an on-off switch. [ 11 ]
Researchers started investigating electrostatic gating because some trigger drug delivery systems on the market are not entirely feasible. The main complaint of these other systems is that continual external stimulation is required for the therapy to function. [ 12 ] In order to combat this complaint, the Grattoni lab in Houston , Texas started working on a drug delivery system that utilized electrostatic gating. The researchers generated a silicon carbide coated nanofluidic membrane that would have controlled release of a drug when a buried electrode was exposed to low intensity voltage. [ 12 ] What the researchers found was that their device was able to successfully release drug and do it in such a way that drug release was proportional to the applied voltage. They also found that the device was chemically inert, making it feasible for long term implantation. [ 12 ] | https://en.wikipedia.org/wiki/Gated_drug_delivery_systems |
The Gateway cloning method is a method of molecular cloning invented and commercialized by Invitrogen since the late 1990s, which makes use of the integration and excision recombination reactions that take place when bacteriophage lambda infects bacteria. This technology provides a fast and highly efficient way to transport DNA sequences into multi-vector systems for functional analysis and protein expression using Gateway att sites and two proprietary enzyme mixes called BP Clonase and LR Clonase. In vivo , these recombination reactions are facilitated by the recombination of attachment sites from the lambda/phage chromosome (attP) and the bacteria (attB). As a result of recombination between the attP and attB sites, the phage integrates into the bacterial genome flanked by two new recombination sites (attLeft and attRight). The removal of the phage from the bacterial chromosome and the regeneration of attP and attB sites can both result from the attL and attR sites recombining under specific circumstances.
DNA sequences of interest are added to modified versions of these special Gateway Att sites. Two enzyme reactions take place, BP Clonase and LR Clonase. The BP Clonase occurs between the attB sites surrounding the insert and the attP sites of the donor vector. This reaction is catalyzed by the BP Clonase enzyme mixture and produces the entry clone containing the DNA of interest flanked by attL domains. As a byproduct of the reaction, the lethal ccdB gene is excised from the donor vector. The LR Clonase occurs between the attL regions of the generated entry clone and the attR regions of the target vector and is catalyzed by the LR Clonase enzyme mix. As a result, an expression clone with DNA of interest flanked by attB regions is produced. As in the BP reaction, a DNA sequence containing the ccdB gene is cut from the target vector.
Large archives of Gateway Entry clones, containing the vast majority of human, mouse, and rat ORFs ( open reading frames ) have been cloned from human cDNA libraries or chemically synthesized to support the research community using NIH (National Institutes of Health) funding (e.g. Mammalian Gene Collection, http://mgc.nci.nih.gov/ Archived 2015-02-25 at the Wayback Machine ). The availability of these gene cassettes in a standard Gateway cloning plasmid helps researchers quickly transfer these cassettes into plasmids that facilitate the analysis of gene function. Gateway cloning does take more time for initial set-up, and is more expensive than traditional restriction enzyme and ligase-based cloning methods, but it saves time and offers simpler and highly efficient cloning for downstream applications.
The technology has been widely adopted by the life science research community especially for applications that require the transfer of thousands of DNA fragments into one type of plasmid (e.g., one containing a CMV promoter for protein expression in mammalian cells), or for the transfer of one DNA fragment into many different types of plasmids (e.g., for bacterial, insect, and mammalian protein expression).
The first step in Gateway cloning is the preparation of a Gateway Entry clone. There are a few different ways to make entry clone.
The second step in Gateway cloning is the preparation of a Gateway Destination vector. It is important to choose the target vector that best suits your target when preparing the expression clone. The gene cassette in the Gateway Entry clone can then be simply and efficiently transferred into any Gateway Destination vector (Invitrogen nomenclature for any Gateway plasmid that contains Gateway “attR” recombination sequences and elements such as promoters and epitope tags, but not ORFs ) using the proprietary enzyme mix, “LR Clonase”. Thousands of Gateway Destination plasmids have been made and are freely shared amongst researchers across the world. Gateway Destination vectors are similar to classical expression vectors containing multiple cloning sites, before the insertion of a gene of interest, using restriction enzyme digestion and ligation. Gateway Destination vectors are commercially available from Invitrogen, EMD ( Novagen ) and Covalys.
The third step in Gateway cloning is the preparation of express your gene of interest. Make sure to use sequencing or a restriction digest to check the integrity of your expression clone. Once your construct is working, you can transform or transfect the cells you intend to employ in your investigations.
Since Gateway cloning uses patented recombination sequences, and proprietary enzyme mixes available only from Invitrogen, the technology does not allow researchers to switch vendors and contributes to the lock-in effect of all such patented procedures.
To summarize the different steps involved in Gateway cloning: | https://en.wikipedia.org/wiki/Gateway_Technology |
In telecommunication , the term gating has the following meanings:
This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from the original on 2022-01-22. (in support of MIL-STD-188 ).
This article related to telecommunications is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gating_(telecommunication) |
The Gattermann reaction (also known as the Gattermann formylation and the Gattermann salicylaldehyde synthesis ) is a chemical reaction in which aromatic compounds are formylated by a mixture of hydrogen cyanide (HCN) and hydrogen chloride (HCl) in the presence of a Lewis acid catalyst such as aluminium chloride (AlCl 3 ). [ 1 ] It is named for the German chemist Ludwig Gattermann [ 2 ] and is similar to the Friedel–Crafts reaction .
Modifications have shown that it is possible to use sodium cyanide or cyanogen bromide in place of hydrogen cyanide. [ 3 ]
The reaction can be simplified by replacing the HCN/AlCl 3 combination with zinc cyanide . [ 4 ] Although it is also highly toxic, Zn(CN) 2 is a solid, making it safer to work with than gaseous HCN. [ 5 ] The Zn(CN) 2 reacts with the HCl to form the key HCN reactant and Zn(Cl) 2 that serves as the Lewis-acid catalyst in-situ . An example of the Zn(CN) 2 method is the synthesis of mesitaldehyde from mesitylene . [ 6 ]
The Gattermann–Koch reaction , named after the German chemists Ludwig Gattermann and Julius Arnold Koch , [ 7 ] is a variant of the Gattermann reaction in which carbon monoxide (CO) is used instead of hydrogen cyanide. [ 8 ]
Unlike the Gattermann reaction, this reaction is not applicable to phenol and phenol ether substrates. [ 5 ] Although the highly unstable formyl chloride was initially postulated as an intermediate, formyl cation (i.e., protonated carbon monoxide), [HCO] + , is now thought to react directly with the arene without the initial formation of formyl chloride. [ 9 ] Additionally, when zinc chloride is used as the Lewis acid instead of aluminum chloride for example, or when the carbon monoxide is not used at high pressure, the presence of traces of copper(I) chloride or nickel(II) chloride co-catalyst is often necessary. The transition metal co-catalyst may server as a "carrier" by first reacting with CO to form a carbonyl complex, which is then transformed into the active electrophile. [ 10 ] | https://en.wikipedia.org/wiki/Gattermann_reaction |
In the study of conformational isomerism , the gauche effect is an atypical situation where a gauche conformation (groups separated by a torsion angle of approximately 60°) is more stable than the anti conformation (180°). [ 2 ]
There are both steric and electronic effects that affect the relative stability of conformers. Ordinarily, steric effects predominate to place large substituents far from each other. However, this is not the case for certain substituents, typically those that are highly electronegative . Instead, there is an electronic preference for these groups to be gauche. Typically studied examples include 1,2-difluoroethane (H 2 FCCFH 2 ), ethylene glycol, and vicinal-difluoroalkyl structures.
There are two main explanations for the gauche effect: hyperconjugation and bent bonds . In the hyperconjugation model, the donation of electron density from the C−H σ bonding orbital to the C−F σ * antibonding orbital is considered the source of stabilization in the gauche isomer. Due to the greater electronegativity of fluorine, the C−H σ orbital is a better electron donor than the C−F σ orbital, while the C−F σ * orbital is a better electron acceptor than the C−H σ * orbital. Only the gauche conformation allows good overlap between the better donor and the better acceptor.
Key in the bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both C−F bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the central C−C bond. The resulting reduced orbital overlap can be partially compensated when a gauche conformation is assumed, forming a bent bond. Of these two models, hyperconjugation is generally considered the principal cause behind the gauche effect in difluoroethane. [ 5 ] [ 6 ]
The molecular geometry of both rotamers can be obtained experimentally by high-resolution infrared spectroscopy augmented with in silico work. [ 2 ] In accordance with the model described above, the carbon–carbon bond length is higher for the anti-rotamer (151.4 pm vs. 150 pm). The steric repulsion between the fluorine atoms in the gauche rotamer causes increased CCF bond angles (by 3.2°) and increased FCCF dihedral angles (from the default 60° to 71°).
In the related compound 1,2-difluoro-1,2-diphenylethane, the threo isomer is found (by X-ray diffraction and from NMR coupling constants ) to have an anti conformation between the two phenyl groups and the two fluorine groups and a gauche conformation is found for both groups for the erythro isomer. [ 7 ] According to in silico results, this conformation is more stable by 0.21 kcal/mol (880 J/mol).
A gauche effect has also been reported for a molecule featuring an all-syn array of four consecutive fluoro substituents. The reaction to install the fourth one is stereoselective : [ 8 ]
The gauche effect is also seen in 1,2-dimethoxyethane [ citation needed ] and some vicinal-dinitroalkyl compounds.
The alkene cis effect is an analogous atypical stabilizing of certain alkenes.
The gauche effect is very sensitive to solvent effects , due to the large difference in polarity between the two conformers. For example, 2,3-dinitro-2,3-dimethylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride , it prefers the anti conformer by a ratio of 58:42. [ 9 ] Another case is trans -1,2 difluorocyclohexane, which has a larger preference for the di-equatorial conformer, rather than the anti-diaxial conformer, in more polar solvents. [ 6 ] | https://en.wikipedia.org/wiki/Gauche_effect |
In science and engineering , a dimensional gauge or simply gauge is a device used to make measurements or to display certain dimensional information. A wide variety of tools exist which serve such functions, ranging from simple pieces of material against which sizes can be measured to complex pieces of machinery.
Dimensional properties include thickness, gap in space, diameter of materials. [ 1 ] [ 2 ]
All gauges can be divided into four main types, independent of their actual use.
The two basic types with an analogue display are usually easier for the human eyes and brain to interpret, especially if many instrument meters must be read simultaneously. An indicator or needle indicates the measurement on the gauge. The other two types are only displaying digits, which are more complex for humans to read and interpret. The ultimate example is cockpit instrumentation in aircraft. The flight instruments cannot display figures only, hence even in the most modern "glass-cockpits" where almost all instruments are displayed at screens, few figures are visible. Instead the screens display analogue meters.
Various types of dimensional gauges include: | https://en.wikipedia.org/wiki/Gauge_(instrument) |
In particle physics , a gauge boson is a bosonic elementary particle that acts as the force carrier for elementary fermions . [ 1 ] [ 2 ] Elementary particles whose interactions are described by a gauge theory interact with each other by the exchange of gauge bosons, usually as virtual particles .
Photons , W and Z bosons , and gluons are gauge bosons. All known gauge bosons have a spin of 1 and therefore are vector bosons . For comparison, the Higgs boson has spin zero and the hypothetical graviton has a spin of 2.
Gauge bosons are different from the other kinds of bosons: first, fundamental scalar bosons (the Higgs boson); second, mesons , which are composite bosons, made of quarks ; third, larger composite, non-force-carrying bosons, such as certain atoms .
The Standard Model of particle physics recognizes four kinds of gauge bosons: photons , which carry the electromagnetic interaction ; W and Z bosons, which carry the weak interaction ; and gluons , which carry the strong interaction . [ 3 ]
Isolated gluons do not occur because they are colour-charged and subject to colour confinement .
In a quantized gauge theory , gauge bosons are quanta of the gauge fields . Consequently, there are as many gauge bosons as there are generators of the gauge field. In quantum electrodynamics , the gauge group is U(1) ; in this simple case, there is only one gauge boson, the photon. In quantum chromodynamics , the more complicated group SU(3) has eight generators, corresponding to the eight gluons. The three W and Z bosons correspond (roughly) to the three generators of SU(2) in electroweak theory .
Gauge invariance requires that gauge bosons are described mathematically by field equations for massless particles. Otherwise, the mass terms add non-zero additional terms to the Lagrangian under gauge transformations, violating gauge symmetry. Therefore, at a naïve theoretical level, all gauge bosons are required to be massless, and the forces that they describe are required to be long-ranged. The conflict between this idea and experimental evidence that the weak and strong interactions have a very short range requires further theoretical insight.
According to the Standard Model, the W and Z bosons gain mass via the Higgs mechanism . In the Higgs mechanism, the four gauge bosons (of SU(2)×U(1) symmetry) of the unified electroweak interaction couple to a Higgs field . This field undergoes spontaneous symmetry breaking due to the shape of its interaction potential. As a result, the universe is permeated by a non-zero Higgs vacuum expectation value (VEV). This VEV couples to three of the electroweak gauge bosons (W + , W − and Z), giving them mass; the remaining gauge boson remains massless (the photon). This theory also predicts the existence of a scalar Higgs boson , which has been observed in experiments at the LHC . [ 4 ] tau
The Georgi–Glashow model predicts additional gauge bosons named X and Y bosons. The hypothetical X and Y bosons mediate interactions between quarks and leptons , hence violating conservation of baryon number and causing proton decay . Such bosons would be even more massive than W and Z bosons due to symmetry breaking . Analysis of data collected from such sources as the Super-Kamiokande neutrino detector has yielded no evidence of X and Y bosons. [ 5 ]
The fourth fundamental interaction, gravity , may also be carried by a boson, called the graviton. In the absence of experimental evidence and a mathematically coherent theory of quantum gravity , it is unknown whether this would be a gauge boson or not. The role of gauge invariance in general relativity is played by a similar [ clarification needed ] symmetry: diffeomorphism invariance .
W′ and Z′ bosons refer to hypothetical new gauge bosons (named in analogy with the Standard Model W and Z bosons). | https://en.wikipedia.org/wiki/Gauge_boson |
Gauge factor (GF) or strain factor of a strain gauge is the ratio of relative change in electrical resistance R, to the mechanical strain ε. The gauge factor is defined as: [ 1 ]
where
It is a common misconception that the change in resistance of a strain gauge is based solely, or most heavily, on the geometric terms. This is true for some materials ( Δ ρ = 0 {\displaystyle \Delta \rho =0} ), and the gauge factor is simply:
However, most commercial strain gauges utilise resistors made from materials that demonstrate a strong piezoresistive effect . The resistivity of these materials changes with strain, accounting for the Δ ρ / ρ ε {\displaystyle {\frac {\Delta \rho /\rho }{\varepsilon }}} term of the defining equation above. In constantan strain gauges (the most commercially popular), the effect accounts for 20% of the gauge factor, but in silicon gauges, the contribution of the piezoresistive term is much larger than the geometric terms. This can be seen in the general examples of strain gauges below:
The definition of the gauge factor does not rely on temperature, however the gauge factor only relates resistance to strain if there are no temperature effects. In practice, where changes in temperature or temperature gradients exist, the equation to derive resistance will have a temperature term. The total effect is:
where | https://en.wikipedia.org/wiki/Gauge_factor |
A gauge group is a group of gauge symmetries of the Yang–Mills gauge theory of principal connections on a principal bundle . Given a principal bundle P → X {\displaystyle P\to X} with a structure Lie group G {\displaystyle G} , a gauge group is defined to be a group of its vertical automorphisms, that is, its group of bundle automorphisms. This group is isomorphic to the group G ( X ) {\displaystyle G(X)} of global sections of the associated group bundle P ~ → X {\displaystyle {\widetilde {P}}\to X} whose typical fiber is a group G {\displaystyle G} which acts on itself by the adjoint representation . The unit element of G ( X ) {\displaystyle G(X)} is a constant unit-valued section g ( x ) = 1 {\displaystyle g(x)=1} of P ~ → X {\displaystyle {\widetilde {P}}\to X} .
At the same time, gauge gravitation theory exemplifies field theory on a principal frame bundle whose gauge symmetries are general covariant transformations which are not elements of a gauge group.
In the physical literature on gauge theory , a structure group of a principal bundle often is called the gauge group .
In quantum gauge theory , one considers a normal subgroup G 0 ( X ) {\displaystyle G^{0}(X)} of a gauge group G ( X ) {\displaystyle G(X)} which is the stabilizer
of some point 1 ∈ P ~ x 0 {\displaystyle 1\in {\widetilde {P}}_{x_{0}}} of a group bundle P ~ → X {\displaystyle {\widetilde {P}}\to X} . It is called the pointed gauge group . This group acts freely on a space of principal connections. Obviously, G ( X ) / G 0 ( X ) = G {\displaystyle G(X)/G^{0}(X)=G} . One also introduces the effective gauge group G ¯ ( X ) = G ( X ) / Z {\displaystyle {\overline {G}}(X)=G(X)/Z} where Z {\displaystyle Z} is the center of a gauge group G ( X ) {\displaystyle G(X)} . This group G ¯ ( X ) {\displaystyle {\overline {G}}(X)} acts freely on a space of irreducible principal connections.
If a structure group G {\displaystyle G} is a complex semisimple matrix group , the Sobolev completion G ¯ k ( X ) {\displaystyle {\overline {G}}_{k}(X)} of a gauge group G ( X ) {\displaystyle G(X)} can be introduced. It is a Lie group. A key point is that the action of G ¯ k ( X ) {\displaystyle {\overline {G}}_{k}(X)} on a Sobolev completion A k {\displaystyle A_{k}} of a space of principal connections is smooth, and that an orbit space A k / G ¯ k ( X ) {\displaystyle A_{k}/{\overline {G}}_{k}(X)} is a Hilbert space . It is a configuration space of quantum gauge theory.
This article about theoretical physics is a stub . You can help Wikipedia by expanding it .
This geometry-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gauge_group_(mathematics) |
In physics , a gauge principle specifies a procedure for obtaining an interaction term from a free Lagrangian which is symmetric with respect to a continuous symmetry —the results of localizing (or gauging ) the global symmetry group must be accompanied by the inclusion of additional fields (such as the electromagnetic field ), with appropriate kinetic and interaction terms in the action , in such a way that the extended Lagrangian is covariant with respect to a new extended group of local transformations. [ 1 ]
This quantum mechanics -related article is a stub . You can help Wikipedia by expanding it .
This article about theoretical physics is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gauge_principle |
In mathematics, any Lagrangian system generally admits gauge symmetries, though it may happen that they are trivial. In theoretical physics , the notion of gauge symmetries depending on parameter functions is a cornerstone of contemporary field theory .
A gauge symmetry of a Lagrangian L {\displaystyle L} is defined as a differential operator on some vector bundle E {\displaystyle E} taking its values in the linear space of (variational or exact) symmetries of L {\displaystyle L} . Therefore, a gauge symmetry of L {\displaystyle L} depends on sections of E {\displaystyle E} and their partial derivatives. [ 1 ] For instance, this is the case of gauge symmetries in classical field theory . [ 2 ] Yang–Mills gauge theory and gauge gravitation theory exemplify classical field theories with gauge symmetries. [ 3 ]
Gauge symmetries possess the following two peculiarities.
Note that, in quantum field theory , a generating functional may fail to be invariant under gauge transformations, and gauge symmetries are replaced with the BRST symmetries , depending on ghosts and acting both on fields and ghosts. [ 6 ] | https://en.wikipedia.org/wiki/Gauge_symmetry_(mathematics) |
Gauge vector–tensor gravity [ 1 ] ( GVT ) is a relativistic generalization of Mordehai Milgrom 's modified Newtonian dynamics (MOND) paradigm [ 2 ] where gauge fields cause the MOND behavior. The former covariant realizations of MOND such as the Bekenstein's tensor–vector–scalar gravity and the Moffat's scalar–tensor–vector gravity attribute MONDian behavior to some scalar fields. GVT is the first example wherein the MONDian behavior is mapped to the gauge vector fields.
The main features of GVT can be summarized as follows:
Its dynamical degrees of freedom are:
The physical geometry, as seen by particles, represents the Finsler geometry –Randers type:
This implies that the orbit of a particle with mass m {\displaystyle m} can be derived from the following effective action:
The geometrical quantities are Riemannian. GVT, thus, is a bi-geometric gravity.
The metric's action coincides to that of the Einstein–Hilbert gravity:
where R {\displaystyle R} is the Ricci scalar constructed out from the metric. The action of the gauge fields follow:
where L has the following MOND asymptotic behaviors
and κ , κ ~ {\displaystyle \kappa ,{\widetilde {\kappa }}} represent the coupling constants of the theory while ℓ , ℓ ~ {\displaystyle \ell ,{\widetilde {\ell }}} are the parameters of the theory and ℓ < ℓ ~ . {\displaystyle \ell <{\widetilde {\ell }}.}
Metric couples to the energy-momentum tensor. The matter current is the source field of both gauge fields. The matter current is
where ρ {\displaystyle \rho } is the density and u μ {\displaystyle u^{\mu }} represents the four velocity.
GVT accommodates the Newtonian and MOND regime of gravity; but it admits the post-MONDian regime.
The strong and Newtonian regime of the theory is defined to be where holds:
The consistency between the gravitoelectromagnetism approximation to the GVT theory and that predicted and measured by the Einstein–Hilbert gravity demands that
which results in
So the theory coincides to the Einstein–Hilbert gravity in its Newtonian and strong regimes.
The MOND regime of the theory is defined to be
So the action for the B μ {\displaystyle B_{\mu }} field becomes aquadratic. For the static mass distribution, the theory then converts to the AQUAL model of gravity [ 3 ] with the critical acceleration of
So the GVT theory is capable of reproducing the flat rotational velocity curves of galaxies. The current observations do not fix κ {\displaystyle \kappa } which is supposedly of order one.
The post-MONDian regime of the theory is defined where both of the actions of the B μ , B ~ μ {\displaystyle B_{\mu },{\widetilde {B}}_{\mu }} are aquadratic. The MOND type behavior is suppressed in this regime due to the contribution of the second gauge field. | https://en.wikipedia.org/wiki/Gauge_vector–tensor_gravity |
Gauged supergravity is a supergravity theory in which some R-symmetry is gauged such that the gravitinos ( superpartners of the graviton ) are charged with respect to the gauge fields . Consistency of the supersymmetry transformation often requires
the presence of the potential for the scalar fields of the theory, or the cosmological constant if the theory
contains no scalar degree of freedom. The gauged supergravity often has the anti-de Sitter space as a supersymmetric vacuum.
Notable exception is a six-dimensional N =(1,0) gauged supergravity.
"Gauged supergravity" in this sense should be contrasted with Yang–Mills–Einstein supergravity in which some other would-be global symmetries of the theory are gauged and fields other than the gravitinos are charged with respect to the gauge fields.
This relativity -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Gauged_supergravity |
Gauss's diary was a record of the mathematical discoveries of German mathematician Carl Friedrich Gauss from 1796 to 1814. It was rediscovered in 1897 and published by Klein (1903) , and reprinted in volume X 1 of his collected works and in ( Gauss 2005 ). There is an English translation with commentary given by Gray (1984) , reprinted in the second edition of ( Dunnington 2004 ).
Most of the entries consist of a brief and sometimes cryptic statement of a result in Latin.
Entry 1, dated 1796, March 30, states " Principia quibus innititur sectio circuli, ac divisibilitas eiusdem geometrica in septemdecim partes etc. ", which records Gauss's discovery of the construction of a heptadecagon by ruler and compass.
Entry 18, dated 1796, July 10, states " ΕΥΡΗΚΑ ! num = Δ + Δ + Δ " and records his discovery of a proof that any number is the sum of 3 triangular numbers, a special case of the Fermat polygonal number theorem .
Entry 43, dated 1796, October 21, states "Vicimus GEGAN" (We have conquered GEGAN). The meaning of this was a mystery for many years. Biermann (1997) found a manuscript by Gauss suggesting that GEGAN is a reversal of the acronym NAGEG standing for Nexum medii Arithmetico-Geometricum Expectationibus Generalibus and refers to the connection between the arithmetic geometric mean and elliptic functions.
Entry 146, dated 1814 July 9, is the last entry, and records an observation relating biquadratic residues and the lemniscate functions , later proved by Gauss and by Chowla (1940) . More precisely, Gauss observed that if a + bi is a (Gaussian) prime and a –1+ bi is divisible by 2+2 i , then the number of solutions to the congruence 1= xx + yy + xxyy (mod a + bi ), including x =∞, y =± i and x =± i , y =∞, is ( a –1) 2 + b 2 . | https://en.wikipedia.org/wiki/Gauss's_diary |
In Riemannian geometry , Gauss's lemma asserts that any sufficiently small sphere centered at a point in a Riemannian manifold is perpendicular to every geodesic through the point. More formally, let M be a Riemannian manifold , equipped with its Levi-Civita connection , and p a point of M . The exponential map is a mapping from the tangent space at p to M :
which is a diffeomorphism in a neighborhood of zero. Gauss' lemma asserts that the image of a sphere of sufficiently small radius in T p M under the exponential map is perpendicular to all geodesics originating at p . The lemma allows the exponential map to be understood as a radial isometry , and is of fundamental importance in the study of geodesic convexity and normal coordinates .
We define the exponential map at p ∈ M {\displaystyle p\in M} by
where γ p , v {\displaystyle \gamma _{p,v}} is the unique geodesic with γ p , v ( 0 ) = p {\displaystyle \gamma _{p,v}(0)=p} and tangent γ p , v ′ ( 0 ) = v ∈ T p M {\displaystyle \gamma _{p,v}'(0)=v\in T_{p}M} and ϵ {\displaystyle \epsilon } is chosen small enough so that for every t ∈ [ 0 , 1 ] , v t ∈ B ϵ ( 0 ) ⊂ T p M {\displaystyle t\in [0,1],vt\in B_{\epsilon }(0)\subset T_{p}M} the geodesic γ p , v ( t ) {\displaystyle \gamma _{p,v}(t)} is defined. So, if M {\displaystyle M} is complete, then, by the Hopf–Rinow theorem , exp p {\displaystyle \exp _{p}} is defined on the whole tangent space.
Let α : I → T p M {\displaystyle \alpha :I\rightarrow T_{p}M} be a curve differentiable in T p M {\displaystyle T_{p}M} such that α ( 0 ) := 0 {\displaystyle \alpha (0):=0} and α ′ ( 0 ) := v {\displaystyle \alpha '(0):=v} . Since T p M ≅ R n {\displaystyle T_{p}M\cong \mathbb {R} ^{n}} , it is clear that we can choose α ( t ) := v t {\displaystyle \alpha (t):=vt} . In this case, by the definition of the differential of the exponential in 0 {\displaystyle 0} applied over v {\displaystyle v} , we obtain:
So (with the right identification T 0 T p M ≅ T p M {\displaystyle T_{0}T_{p}M\cong T_{p}M} ) the differential of exp p {\displaystyle \exp _{p}} is the identity. By the implicit function theorem, exp p {\displaystyle \exp _{p}} is a diffeomorphism on a neighborhood of 0 ∈ T p M {\displaystyle 0\in T_{p}M} . The Gauss Lemma now tells that exp p {\displaystyle \exp _{p}} is also a radial isometry.
Let p ∈ M {\displaystyle p\in M} . In what follows, we make the identification T v T p M ≅ T p M ≅ R n {\displaystyle T_{v}T_{p}M\cong T_{p}M\cong \mathbb {R} ^{n}} .
Gauss's Lemma states: Let v , w ∈ B ϵ ( 0 ) ⊂ T v T p M ≅ T p M {\displaystyle v,w\in B_{\epsilon }(0)\subset T_{v}T_{p}M\cong T_{p}M} and M ∋ q := exp p ( v ) {\displaystyle M\ni q:=\exp _{p}(v)} . Then, ⟨ T v exp p ( v ) , T v exp p ( w ) ⟩ q = ⟨ v , w ⟩ p . {\displaystyle \langle T_{v}\exp _{p}(v),T_{v}\exp _{p}(w)\rangle _{q}=\langle v,w\rangle _{p}.}
For p ∈ M {\displaystyle p\in M} , this lemma means that exp p {\displaystyle \exp _{p}} is a radial isometry in the following sense: let v ∈ B ϵ ( 0 ) {\displaystyle v\in B_{\epsilon }(0)} , i.e. such that exp p {\displaystyle \exp _{p}} is well defined.
And let q := exp p ( v ) ∈ M {\displaystyle q:=\exp _{p}(v)\in M} . Then the exponential exp p {\displaystyle \exp _{p}} remains an isometry in q {\displaystyle q} , and, more generally, all along the geodesic γ {\displaystyle \gamma } (in so far as γ p , v ( 1 ) = exp p ( v ) {\displaystyle \gamma _{p,v}(1)=\exp _{p}(v)} is well defined)! Then, radially, in all the directions permitted by the domain of definition of exp p {\displaystyle \exp _{p}} , it remains an isometry.
Recall that
We proceed in three steps:
α : R ⊃ I → T p M {\displaystyle \alpha :\mathbb {R} \supset I\rightarrow T_{p}M} such that α ( 0 ) := v ∈ T p M {\displaystyle \alpha (0):=v\in T_{p}M} and α ′ ( 0 ) := v ∈ T v T p M ≅ T p M {\displaystyle \alpha '(0):=v\in T_{v}T_{p}M\cong T_{p}M} . Since T v T p M ≅ T p M ≅ R n {\displaystyle T_{v}T_{p}M\cong T_{p}M\cong \mathbb {R} ^{n}} , we can put α ( t ) := v ( t + 1 ) {\displaystyle \alpha (t):=v(t+1)} .
Therefore,
T v exp p ( v ) = d d t ( exp p ∘ α ( t ) ) | t = 0 = d d t ( exp p ( t v ) ) | t = 1 = Γ ( γ ) p exp p ( v ) v = v , {\displaystyle T_{v}\exp _{p}(v)={\frac {\mathrm {d} }{\mathrm {d} t}}{\Bigl (}\exp _{p}\circ \alpha (t){\Bigr )}{\Big \vert }_{t=0}={\frac {\mathrm {d} }{\mathrm {d} t}}{\Bigl (}\exp _{p}(tv){\Bigr )}{\Big \vert }_{t=1}=\Gamma (\gamma )_{p}^{\exp _{p}(v)}v=v,}
where Γ {\displaystyle \Gamma } is the parallel transport operator and γ ( t ) = exp p ( t v ) {\displaystyle \gamma (t)=\exp _{p}(tv)} . The last equality is true because γ {\displaystyle \gamma } is a geodesic, therefore γ ′ {\displaystyle \gamma '} is parallel.
Now let us calculate the scalar product ⟨ T v exp p ( v ) , T v exp p ( w ) ⟩ {\displaystyle \langle T_{v}\exp _{p}(v),T_{v}\exp _{p}(w)\rangle } .
We separate w {\displaystyle w} into a component w T {\displaystyle w_{T}} parallel to v {\displaystyle v} and a component w N {\displaystyle w_{N}} normal to v {\displaystyle v} . In particular, we put w T := a v {\displaystyle w_{T}:=av} , a ∈ R {\displaystyle a\in \mathbb {R} } .
The preceding step implies directly:
We must therefore show that the second term is null, because, according to Gauss's Lemma, we must have:
⟨ T v exp p ( v ) , T v exp p ( w N ) ⟩ = ⟨ v , w N ⟩ = 0. {\displaystyle \langle T_{v}\exp _{p}(v),T_{v}\exp _{p}(w_{N})\rangle =\langle v,w_{N}\rangle =0.}
Let us define the curve
Note that
Let us put:
and we calculate:
and
Hence
We can now verify that this scalar product is actually independent of the variable t {\displaystyle t} , and therefore that, for example:
because, according to what has been given above:
being given that the differential is a linear map. This will therefore prove the lemma.
Since the maps t ↦ f ( s , t ) {\displaystyle t\mapsto f(s,t)} are geodesics,
the function t ↦ ⟨ ∂ f ∂ t , ∂ f ∂ t ⟩ {\displaystyle t\mapsto \left\langle {\frac {\partial f}{\partial t}},{\frac {\partial f}{\partial t}}\right\rangle } is constant. Thus, | https://en.wikipedia.org/wiki/Gauss's_lemma_(Riemannian_geometry) |
Gauss's lemma in number theory gives a condition for an integer to be a quadratic residue . Although it is not useful computationally, it has theoretical significance, being involved in some proofs of quadratic reciprocity .
It made its first appearance in Carl Friedrich Gauss 's third proof (1808) [ 1 ] : 458–462 of quadratic reciprocity and he proved it again in his fifth proof (1818). [ 1 ] : 496–501
For any odd prime p let a be an integer that is coprime to p .
Consider the integers
and their least positive residues modulo p . These residues are all distinct, so there are ( p − 1)/2 of them.
Let n be the number of these residues that are greater than p /2 . Then
where ( a p ) {\displaystyle \left({\frac {a}{p}}\right)} is the Legendre symbol .
Taking p = 11 and a = 7, the relevant sequence of integers is
After reduction modulo 11, this sequence becomes
Three of these integers are larger than 11/2 (namely 6, 7 and 10), so n = 3. Correspondingly Gauss's lemma predicts that
This is indeed correct, because 7 is not a quadratic residue modulo 11.
The above sequence of residues
may also be written
In this form, the integers larger than 11/2 appear as negative numbers. It is also apparent that the absolute values of the residues are a permutation of the residues
A fairly simple proof, [ 1 ] : 458–462 reminiscent of one of the simplest proofs of Fermat's little theorem , can be obtained by evaluating the product
modulo p in two different ways. On one hand it is equal to
The second evaluation takes more work. If x is a nonzero residue modulo p , let us define the "absolute value" of x to be
Since n counts those multiples ka which are in the latter range, and since for those multiples, − ka is in the first range, we have
Now observe that the values | ra | are distinct for r = 1, 2, …, ( p − 1)/2 . Indeed, we have
because a is coprime to p .
This gives r = s , since r and s are positive least residues. But there are exactly ( p − 1)/2 of them, so their values are a rearrangement of the integers 1, 2, …, ( p − 1)/2 . Therefore,
Comparing with our first evaluation, we may cancel out the nonzero factor
and we are left with
This is the desired result, because by Euler's criterion the left hand side is just an alternative expression for the Legendre symbol ( a p ) {\displaystyle \left({\frac {a}{p}}\right)} .
For any odd prime p let a be an integer that is coprime to p .
Let I ⊂ ( Z / p Z ) × {\displaystyle I\subset (\mathbb {Z} /p\mathbb {Z} )^{\times }} be a set such that ( Z / p Z ) × {\displaystyle (\mathbb {Z} /p\mathbb {Z} )^{\times }} is the disjoint union of I {\displaystyle I} and − I = { − i : i ∈ I } {\displaystyle -I=\{-i:i\in I\}} .
Then ( a p ) = ( − 1 ) t {\displaystyle \left({\frac {a}{p}}\right)=(-1)^{t}} , where t = # { j ∈ I : a j ∈ − I } {\displaystyle t=\#\{j\in I:aj\in -I\}} . [ 2 ]
In the original statement, I = { 1 , 2 , … , p − 1 2 } {\displaystyle I=\{1,2,\dots ,{\frac {p-1}{2}}\}} .
The proof is almost the same.
Gauss's lemma is used in many, [ 3 ] : Ch. 1 [ 3 ] : 9 but by no means all, of the known proofs of quadratic reciprocity.
For example, Gotthold Eisenstein [ 3 ] : 236 used Gauss's lemma to prove that if p is an odd prime then
and used this formula to prove quadratic reciprocity. By using elliptic rather than circular functions, he proved the cubic and quartic reciprocity laws. [ 3 ] : Ch. 8
Leopold Kronecker [ 3 ] : Ex. 1.34 used the lemma to show that
Switching p and q immediately gives quadratic reciprocity.
It is also used in what are probably the simplest proofs of the "second supplementary law"
Generalizations of Gauss's lemma can be used to compute higher power residue symbols. In his second monograph on biquadratic reciprocity, [ 4 ] : §§69–71 Gauss used a fourth-power lemma to derive the formula for the biquadratic character of 1 + i in Z [ i ] , the ring of Gaussian integers . Subsequently, Eisenstein used third- and fourth-power versions to prove cubic and quartic reciprocity . [ 3 ] : Ch. 8
Let k be an algebraic number field with ring of integers O k , {\displaystyle {\mathcal {O}}_{k},} and let p ⊂ O k {\displaystyle {\mathfrak {p}}\subset {\mathcal {O}}_{k}} be a prime ideal . The ideal norm N p {\displaystyle \mathrm {N} {\mathfrak {p}}} of p {\displaystyle {\mathfrak {p}}} is defined as the cardinality of the residue class ring. Since p {\displaystyle {\mathfrak {p}}} is prime this is a finite field O k / p {\displaystyle {\mathcal {O}}_{k}/{\mathfrak {p}}} , so the ideal norm is N p = | O k / p | {\displaystyle \mathrm {N} {\mathfrak {p}}=|{\mathcal {O}}_{k}/{\mathfrak {p}}|} .
Assume that a primitive n th root of unity ζ n ∈ O k , {\displaystyle \zeta _{n}\in {\mathcal {O}}_{k},} and that n and p {\displaystyle {\mathfrak {p}}} are coprime (i.e. n ∉ p {\displaystyle n\not \in {\mathfrak {p}}} ). Then no two distinct n th roots of unity can be congruent modulo p {\displaystyle {\mathfrak {p}}} .
This can be proved by contradiction, beginning by assuming that ζ n r ≡ ζ n s {\displaystyle \zeta _{n}^{r}\equiv \zeta _{n}^{s}} mod p {\displaystyle {\mathfrak {p}}} , 0 < r < s ≤ n . Let t = s − r such that ζ n t ≡ 1 {\displaystyle \zeta _{n}^{t}\equiv 1} mod p {\displaystyle {\mathfrak {p}}} , and 0 < t < n . From the definition of roots of unity,
and dividing by x − 1 gives
Letting x = 1 and taking residues mod p {\displaystyle {\mathfrak {p}}} ,
Since n and p {\displaystyle {\mathfrak {p}}} are coprime, n ≢ 0 {\displaystyle n\not \equiv 0} mod p , {\displaystyle {\mathfrak {p}},} but under the assumption, one of the factors on the right must be zero. Therefore, the assumption that two distinct roots are congruent is false.
Thus the residue classes of O k / p {\displaystyle {\mathcal {O}}_{k}/{\mathfrak {p}}} containing the powers of ζ n are a subgroup of order n of its (multiplicative) group of units, ( O k / p ) × = O k / p − { 0 } . {\displaystyle ({\mathcal {O}}_{k}/{\mathfrak {p}})^{\times }={\mathcal {O}}_{k}/{\mathfrak {p}}-\{0\}.} Therefore, the order of ( O k / p ) × {\displaystyle ({\mathcal {O}}_{k}/{\mathfrak {p}})^{\times }} is a multiple of n , and
There is an analogue of Fermat's theorem in O k {\displaystyle {\mathcal {O}}_{k}} . If α ∈ O k {\displaystyle \alpha \in {\mathcal {O}}_{k}} for α ∉ p {\displaystyle \alpha \not \in {\mathfrak {p}}} , then [ 3 ] : Ch. 4.1
and since N p ≡ 1 {\displaystyle \mathrm {N} {\mathfrak {p}}\equiv 1} mod n ,
is well-defined and congruent to a unique n th root of unity ζ n s .
This root of unity is called the n th-power residue symbol for O k , {\displaystyle {\mathcal {O}}_{k},} and is denoted by
It can be proven that [ 3 ] : Prop. 4.1
if and only if there is an η ∈ O k {\displaystyle \eta \in {\mathcal {O}}_{k}} such that α ≡ η n mod p {\displaystyle {\mathfrak {p}}} .
Let μ n = { 1 , ζ n , ζ n 2 , … , ζ n n − 1 } {\displaystyle \mu _{n}=\{1,\zeta _{n},\zeta _{n}^{2},\dots ,\zeta _{n}^{n-1}\}} be the multiplicative group of the n th roots of unity, and let A = { a 1 , a 2 , … , a m } {\displaystyle A=\{a_{1},a_{2},\dots ,a_{m}\}} be representatives of the cosets of ( O k / p ) × / μ n . {\displaystyle ({\mathcal {O}}_{k}/{\mathfrak {p}})^{\times }/\mu _{n}.} Then A is called a 1/ n system mod p . {\displaystyle {\mathfrak {p}}.} [ 3 ] : Ch. 4.2
In other words, there are m n = N p − 1 {\displaystyle mn=\mathrm {N} {\mathfrak {p}}-1} numbers in the set A μ = { a i ζ n j : 1 ≤ i ≤ m , 0 ≤ j ≤ n − 1 } , {\displaystyle A\mu =\{a_{i}\zeta _{n}^{j}\;:\;1\leq i\leq m,\;\;\;0\leq j\leq n-1\},} and this set constitutes a representative set for ( O k / p ) × . {\displaystyle ({\mathcal {O}}_{k}/{\mathfrak {p}})^{\times }.}
The numbers 1, 2, … ( p − 1)/2 , used in the original version of the lemma, are a 1/2 system (mod p ).
Constructing a 1/ n system is straightforward: let M be a representative set for ( O k / p ) × . {\displaystyle ({\mathcal {O}}_{k}/{\mathfrak {p}})^{\times }.} Pick any a 1 ∈ M {\displaystyle a_{1}\in M} and remove the numbers congruent to a 1 , a 1 ζ n , a 1 ζ n 2 , … , a 1 ζ n n − 1 {\displaystyle a_{1},a_{1}\zeta _{n},a_{1}\zeta _{n}^{2},\dots ,a_{1}\zeta _{n}^{n-1}} from M . Pick a 2 from M and remove the numbers congruent to a 2 , a 2 ζ n , a 2 ζ n 2 , … , a 2 ζ n n − 1 {\displaystyle a_{2},a_{2}\zeta _{n},a_{2}\zeta _{n}^{2},\dots ,a_{2}\zeta _{n}^{n-1}} Repeat until M is exhausted. Then { a 1 , a 2 , … a m } is a 1/ n system mod p . {\displaystyle {\mathfrak {p}}.}
Gauss's lemma may be extended to the n th power residue symbol as follows. [ 3 ] : Prop. 4.3 Let ζ n ∈ O k {\displaystyle \zeta _{n}\in {\mathcal {O}}_{k}} be a primitive n th root of unity, p ⊂ O k {\displaystyle {\mathfrak {p}}\subset {\mathcal {O}}_{k}} a prime ideal, γ ∈ O k , n γ ∉ p , {\displaystyle \gamma \in {\mathcal {O}}_{k},\;\;n\gamma \not \in {\mathfrak {p}},} (i.e. p {\displaystyle {\mathfrak {p}}} is coprime to both γ and n ) and let A = { a 1 , a 2 , …, a m } be a 1/ n system mod p . {\displaystyle {\mathfrak {p}}.}
Then for each i , 1 ≤ i ≤ m , there are integers π ( i ) , unique (mod m ), and b ( i ) , unique (mod n ), such that
and the n th-power residue symbol is given by the formula
The classical lemma for the quadratic Legendre symbol is the special case n = 2 , ζ 2 = −1 , A = {1, 2, …, ( p − 1)/2} , b ( k ) = 1 if ak > p /2 , b ( k ) = 0 if ak < p /2 .
The proof of the n th-power lemma uses the same ideas that were used in the proof of the quadratic lemma.
The existence of the integers π ( i ) and b ( i ) , and their uniqueness (mod m ) and (mod n ), respectively, come from the fact that Aμ is a representative set.
Assume that π ( i ) = π ( j ) = p , i.e.
and
Then
Because γ and p {\displaystyle {\mathfrak {p}}} are coprime both sides can be divided by γ , giving
which, since A is a 1/ n system, implies s = r and i = j , showing that π is a permutation of the set {1, 2, …, m } .
Then on the one hand, by the definition of the power residue symbol,
and on the other hand, since π is a permutation,
so
and since for all 1 ≤ i ≤ m , a i and p {\displaystyle {\mathfrak {p}}} are coprime, a 1 a 2 … a m can be cancelled from both sides of the congruence,
and the theorem follows from the fact that no two distinct n th roots of unity can be congruent (mod p {\displaystyle {\mathfrak {p}}} ).
Let G be the multiplicative group of nonzero residue classes in Z / p Z , and let H be the subgroup {+1, −1}. Consider the following coset representatives of H in G ,
Applying the machinery of the transfer to this collection of coset representatives, we obtain the transfer homomorphism
which turns out to be the map that sends a to (−1) n , where a and n are as in the statement of the lemma. Gauss's lemma may then be viewed as a computation that explicitly identifies this homomorphism as being the quadratic residue character. | https://en.wikipedia.org/wiki/Gauss's_lemma_(number_theory) |
The principle of least constraint is one variational formulation of classical mechanics enunciated by Carl Friedrich Gauss in 1829, equivalent to all other formulations of analytical mechanics . Intuitively, it says that the acceleration of a constrained physical system will be as similar as possible to that of the corresponding unconstrained system. [ 1 ]
The principle of least constraint is a least squares principle stating that the true accelerations of a mechanical system of n {\displaystyle n} masses is the minimum of the quantity
where the j th particle has mass m j {\displaystyle m_{j}} , position vector r j {\displaystyle \mathbf {r} _{j}} , and applied non-constraint force F j {\displaystyle \mathbf {F} _{j}} acting on the mass.
The notation r ˙ {\displaystyle {\dot {\mathbf {r} }}} indicates time derivative of a vector function r ( t ) {\displaystyle \mathbf {r} (t)} , i.e. position. The corresponding accelerations r ¨ j {\displaystyle {\ddot {\mathbf {r} }}_{j}} satisfy the imposed constraints, which in general depends on the current state of the system, { r j ( t ) , r ˙ j ( t ) } {\displaystyle \{\mathbf {r} _{j}(t),{\dot {\mathbf {r} }}_{j}(t)\}} .
It is recalled the fact that due to active F j {\displaystyle \mathbf {F} _{j}} and reactive (constraint) F c j {\displaystyle \mathbf {F_{c}} _{j}} forces being applied, with resultant R = ∑ j = 1 n F j + F c j {\textstyle \mathbf {R} =\sum _{j=1}^{n}\mathbf {F} _{j}+\mathbf {F_{c}} _{j}} , a system will experience an acceleration r ¨ = ∑ j = 1 n F j m j + F c j m j = ∑ j = 1 n a j + a c j {\textstyle {\ddot {\mathbf {r} }}=\sum _{j=1}^{n}{\frac {\mathbf {F} _{j}}{m_{j}}}+{\frac {\mathbf {F_{c}} _{j}}{m_{j}}}=\sum _{j=1}^{n}\mathbf {a} _{j}+\mathbf {a_{c}} _{j}} .
Gauss's principle is equivalent to D'Alembert's principle .
The principle of least constraint is qualitatively similar to Hamilton's principle , which states that the true path taken by a mechanical system is an extremum of the action . However, Gauss's principle is a true (local) minimal principle, whereas the other is an extremal principle.
Hertz's principle of least curvature is a special case of Gauss's principle, restricted by the three conditions that there are no externally applied forces, no interactions (which can usually be expressed as a potential energy ), and all masses are equal. Without loss of generality, the masses may be set equal to one. Under these conditions, Gauss's minimized quantity can be written
The kinetic energy T {\displaystyle T} is also conserved under these conditions
Since the line element d s 2 {\displaystyle ds^{2}} in the 3 N {\displaystyle 3N} -dimensional space of the coordinates is defined
the conservation of energy may also be written
Dividing Z {\displaystyle Z} by 2 T {\displaystyle 2T} yields another minimal quantity
Since K {\displaystyle {\sqrt {K}}} is the local curvature of the trajectory in the 3 n {\displaystyle 3n} -dimensional space of the coordinates, minimization of K {\displaystyle K} is equivalent to finding the trajectory of least curvature (a geodesic ) that is consistent with the constraints.
Hertz's principle is also a special case of Jacobi 's formulation of the least-action principle .
Hertz designed the principle to eliminate the concept of force and dynamics, so that physics would consist exclusively of kinematics, of material points in constrained motion. He was critical of the "logical obscurity" surrounding the idea of force.
I would mention the experience that it is exceedingly difficult to expound to thoughtful hearers that very introduction to mechanics without being occasionally embarrassed, without feeling tempted now and again to apologize, without wishing to get as quickly as possible over the rudiments, and on to examples which speak for themselves. I fancy that Newton himself must have felt this embarrassment...
To replace the concept of force, he proposed that the acceleration of visible masses are to be accounted for, not by force, but by geometric constraints on the visible masses, and their geometric linkages to invisible masses. In this, he understood himself as continuing the tradition of Cartesian mechanical philosophy , such as Boltzmann 's explaining of heat by atomic motion, and Maxwell's explaining of electromagnetism by ether motion. Even though both atoms and the ether were not observable except via their effects, they were successful in explaining apparently non-mechanical phenomena mechanically. In trying to explain away "mechanical force", Hertz was "mechanizing classical mechanics". [ 2 ] | https://en.wikipedia.org/wiki/Gauss's_principle_of_least_constraint |
In mathematics , in number theory , Gauss composition law is a rule, invented by Carl Friedrich Gauss , for performing a binary operation on integral binary quadratic forms (IBQFs). Gauss presented this rule in his Disquisitiones Arithmeticae , [ 1 ] a textbook on number theory published in 1801, in Articles 234 - 244. Gauss composition law is one of the deepest results in the theory of IBQFs and Gauss's formulation of the law and the proofs its properties as given by Gauss are generally considered highly complicated and very difficult. [ 2 ] Several later mathematicians have simplified the formulation of the composition law and have presented it in a format suitable for numerical computations. The concept has also found generalisations in several directions.
An expression of the form Q ( x , y ) = α x 2 + β x y + γ y 2 {\displaystyle Q(x,y)=\alpha x^{2}+\beta xy+\gamma y^{2}} , where α , β , γ , x , y {\displaystyle \alpha ,\beta ,\gamma ,x,y} are all integers , is called an integral binary quadratic form (IBQF). The form Q ( x , y ) {\displaystyle Q(x,y)} is called a primitive IBQF if α , β , γ {\displaystyle \alpha ,\beta ,\gamma } are relatively prime. The quantity Δ = β 2 − 4 α γ {\displaystyle \Delta =\beta ^{2}-4\alpha \gamma } is called the discriminant of the IBQF Q ( x , y ) {\displaystyle Q(x,y)} . An integer Δ {\displaystyle \Delta } is the discriminant of some IBQF if and only if Δ ≡ 0 , 1 ( m o d 4 ) {\displaystyle \Delta \equiv 0,1(\mathrm {mod} \,\,4)} . Δ {\displaystyle \Delta } is called a fundamental discriminant if and only if one of the following statements holds
If Δ < 0 {\displaystyle \Delta <0} and α > 0 {\displaystyle \alpha >0} then Q ( x , y ) {\displaystyle Q(x,y)} is said to be positive definite; if Δ < 0 {\displaystyle \Delta <0} and α < 0 {\displaystyle \alpha <0} then Q ( x , y ) {\displaystyle Q(x,y)} is said to be negative definite; if Δ > 0 {\displaystyle \Delta >0} then Q ( x , y ) {\displaystyle Q(x,y)} is said to be indefinite.
Two IBQFs g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} are said to be equivalent (or, properly equivalent) if there exist integers α, β, γ, δ such that
The notation g ( x , y ) ∼ h ( x , y ) {\displaystyle g(x,y)\sim h(x,y)} is used to denote the fact that the two forms are equivalent. The relation " ∼ {\displaystyle \sim } " is an equivalence relation in the set of all IBQFs. The equivalence class to which the IBQF g ( x , y ) {\displaystyle g(x,y)} belongs is denoted by [ g ( x , y ) ] {\displaystyle [g(x,y)]} .
Two IBQFs g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} are said to be improperly equivalent if
The relation in the set of IBQFs of being improperly equivalent is also an equivalence relation.
It can be easily seen that equivalent IBQFs (properly or improperly) have the same discriminant.
The following identity, called Brahmagupta identity , was known to the Indian mathematician Brahmagupta (598–668) who used it to calculate successively better fractional approximations to square roots of positive integers:
Writing f ( x , y ) = x 2 + D y 2 {\displaystyle f(x,y)=x^{2}+Dy^{2}} this identity can be put in the form
Gauss's composition law of IBQFs generalises this identity to an identity of the form g ( x , y ) h ( u , v ) = F ( X , Y ) {\displaystyle g(x,y)h(u,v)=F(X,Y)} where g ( x , y ) , h ( x , y ) , F ( X , Y ) {\displaystyle g(x,y),h(x,y),F(X,Y)} are all IBQFs and X , Y {\displaystyle X,Y} are linear combinations of the products x u , x v , y u , y v {\displaystyle xu,xv,yu,yv} .
Consider the following IBQFs:
If it is possible to find integers p , q , r , s {\displaystyle p,q,r,s} and p ′ , q ′ , r ′ , s ′ {\displaystyle p^{\prime },q^{\prime },r^{\prime },s^{\prime }} such that the following six numbers
have no common divisors other than ±1, and such that if we let
the following relation is identically satisfied
then the form F ( x , y ) {\displaystyle F(x,y)} is said to be a composite of the forms g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} . It may be noted that the composite of two IBQFs, if it exists, is not unique.
Consider the following binary quadratic forms:
Let
We have
These six numbers have no common divisors other than ±1.
Let
Then it can be verified that
Hence F ( x , y ) {\displaystyle F(x,y)} is a composite of g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} .
The following algorithm can be used to compute the composite of two IBQFs. [ 3 ]
Given the following IBQFs having the same discriminant Δ {\displaystyle \Delta } :
Then F ( X , Y ) = f 1 ( x 1 , y 1 ) f 2 ( x 2 , y 2 ) {\displaystyle F(X,Y)=f_{1}(x_{1},y_{1})f_{2}(x_{2},y_{2})} so that F ( x , y ) {\displaystyle F(x,y)} is a composite of f 1 ( x , y ) {\displaystyle f_{1}(x,y)} and f 2 ( x , y ) {\displaystyle f_{2}(x,y)} .
The composite of two IBQFs exists if and only if they have the same discriminant.
Let g ( x , y ) , h ( x , y ) , g ′ ( x , y ) , h ′ ( x , y ) {\displaystyle g(x,y),h(x,y),g^{\prime }(x,y),h^{\prime }(x,y)} be IBQFs and let there be the following equivalences:
If F ( x , y ) {\displaystyle F(x,y)} is a composite of g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} , and F ′ ( x , y ) {\displaystyle F^{\prime }(x,y)} is a composite of g ′ ( x , y ) {\displaystyle g^{\prime }(x,y)} and h ′ ( x , y ) {\displaystyle h^{\prime }(x,y)} , then
Let D {\displaystyle D} be a fixed integer and consider set S D {\displaystyle S_{D}} of all possible primitive IBQFs of discriminant D {\displaystyle D} . Let G D {\displaystyle G_{D}} be the set of equivalence classes in this set under the equivalence relation " ∼ {\displaystyle \sim } ". Let [ g ( x , y ) ] {\displaystyle [g(x,y)]} and [ h ( x , y ) ] {\displaystyle [h(x,y)]} be two elements of G D {\displaystyle G_{D}} . Let F ( x , y ) {\displaystyle F(x,y)} be a composite of the IBQFs g ( x , y ) {\displaystyle g(x,y)} and h ( x , y ) {\displaystyle h(x,y)} in S D {\displaystyle S_{D}} . Then the following equation
defines a well-defined binary operation " ∘ {\displaystyle \circ } " in G D {\displaystyle G_{D}} .
The following sketch of the modern approach to the composition law of IBQFs is based on a monograph by Duncan A. Buell. [ 4 ] The book may be consulted for further details and for proofs of all the statements made hereunder.
Let Z {\displaystyle \mathbb {Z} } be the set of integers. Hereafter, in this section, elements of Z {\displaystyle \mathbb {Z} } will be referred as rational integers to distinguish them from algebraic integers to be defined below.
A complex number α {\displaystyle \alpha } is called a quadratic algebraic number if it satisfies an equation of the form
α {\displaystyle \alpha } is called a quadratic algebraic integer if it satisfies an equation of the form
The quadratic algebraic numbers are numbers of the form
The integer d {\displaystyle d} is called the radicand of the algebraic integer α {\displaystyle \alpha } . The norm of the quadratic algebraic number α {\displaystyle \alpha } is defined as
Let Q {\displaystyle \mathbb {Q} } be the field of rational numbers. The smallest field containing Q {\displaystyle \mathbb {Q} } and a quadratic algebraic number α {\displaystyle \alpha } is the quadratic field containing α {\displaystyle \alpha } and is denoted by Q ( α ) {\displaystyle \mathbb {Q} (\alpha )} . This field can be shown to be
The discriminant Δ {\displaystyle \Delta } of the field Q ( d ) {\displaystyle \mathbb {Q} ({\sqrt {d}})} is defined by
Let d ≠ 1 {\displaystyle d\neq 1} be a rational integer without square factors (except 1). The set of quadratic algebraic integers of radicand d {\displaystyle d} is denoted by O ( d ) {\displaystyle O({\sqrt {d}})} . This set is given by
O ( d ) {\displaystyle O({\sqrt {d}})} is a ring under ordinary addition and multiplication. If we let
then
Let a {\displaystyle \mathbf {a} } be an ideal in the ring of integers O ( d ) {\displaystyle O({\sqrt {d}})} ; that is, let a {\displaystyle \mathbf {a} } be a nonempty subset of O ( d ) {\displaystyle O({\sqrt {d}})} such that for any α , β ∈ a {\displaystyle \alpha ,\beta \in \mathbf {a} } and any λ , μ ∈ O ( d ) {\displaystyle \lambda ,\mu \in O({\sqrt {d}})} , λ α + μ β ∈ a {\displaystyle \lambda \alpha +\mu \beta \in \mathbf {a} } . (An ideal a {\displaystyle \mathbf {a} } as defined here is sometimes referred to as an integral ideal to distinguish from fractional ideal to be defined below.) If a {\displaystyle \mathbf {a} } is an ideal in O ( d ) {\displaystyle O({\sqrt {d}})} then one can find α 1 , α 2 ∈ O ( d ) {\displaystyle \alpha _{1},\alpha _{2}\in O({\sqrt {d}})} such any element in a {\displaystyle \mathbf {a} } can be uniquely represented in the form α 1 x + α 2 y {\displaystyle \alpha _{1}x+\alpha _{2}y} with x , y ∈ Z {\displaystyle x,y\in \mathbb {Z} } . Such a pair of elements in O ( d ) {\displaystyle O({\sqrt {d}})} is called a basis of the ideal a {\displaystyle \mathbf {a} } . This is indicated by writing a = ⟨ α 1 , α 2 ⟩ {\displaystyle \mathbf {a} =\langle \alpha _{1},\alpha _{2}\rangle } . The norm of a = ⟨ α 1 , α 2 ⟩ {\displaystyle \mathbf {a} =\langle \alpha _{1},\alpha _{2}\rangle } is defined as
The norm is independent of the choice of the basis.
There is this important result: "Given any ideal (integral or fractional) a {\displaystyle \mathbf {a} } , there exists an integral ideal b {\displaystyle \mathbf {b} } such that the product ideal a b {\displaystyle \mathbf {ab} } is a principal ideal."
Two (integral or fractional) ideals a {\displaystyle \mathbf {a} } and b {\displaystyle \mathbf {b} } ares said to be equivalent , dented a ∼ b {\displaystyle \mathbf {a} \sim \mathbf {b} } , if there is a principal ideal ( α ) {\displaystyle (\alpha )} such that a = ( α ) b {\displaystyle \mathbf {a} =(\alpha )\mathbf {b} } . These ideals are narrowly equivalent if the norm of α {\displaystyle \alpha } is positive. The relation, in the set of ideals, of being equivalent or narrowly equivalent as defined here is indeed an equivalence relation.
The equivalence classes (respectively, narrow equivalence classes) of fractional ideals of a ring of quadratic algebraic integers O ( d ) {\displaystyle O({\sqrt {d}})} form an abelian group under multiplication of ideals. The identity of the group is the class of all principal ideals (respectively, the class of all principal ideals ( α ) {\displaystyle (\alpha )} with N ( α ) > 0 {\displaystyle N(\alpha )>0} ). The groups of classes of ideals and of narrow classes of ideals are called the class group and the narrow class group of the Q ( d ) {\displaystyle \mathbb {Q} ({\sqrt {d}})} .
The main result that connects the IBQFs and classes of ideals can now be stated as follows:
Manjul Bhargava , a Canadian-American Fields Medal winning mathematician introduced a configuration, called a Bhargava cube , of eight integers a , b , c , d , e , f {\displaystyle a,b,c,d,e,f} (see figure) to study the composition laws of binary quadratic forms and other such forms. Defining matrices associated with the opposite faces of this cube as given below
Bhargava constructed three IBQFs as follows:
Bhargava established the following result connecting a Bhargava cube with the Gauss composition law: [ 5 ] | https://en.wikipedia.org/wiki/Gauss_composition_law |
In mathematics , Gauss congruence is a property held by certain sequences of integers , including the Lucas numbers and the divisor sum sequence. Sequences satisfying this property are also known as Dold sequences, Fermat sequences, Newton sequences, and realizable sequences. [ 1 ] The property is named after Carl Friedrich Gauss (1777–1855), although Gauss never defined the property explicitly. [ 2 ]
Sequences satisfying Gauss congruence naturally occur in the study of topological dynamics , algebraic number theory and combinatorics . [ 3 ]
A sequence of integers ( a 1 , a 2 , … ) {\displaystyle (a_{1},a_{2},\dots )} satisfies Gauss congruence if
for every n ≥ 1 {\displaystyle n\geq 1} , where μ {\displaystyle \mu } is the Möbius function . By Möbius inversion , this condition is equivalent to the existence of a sequence of integers ( b 1 , b 2 , … ) {\displaystyle (b_{1},b_{2},\dots )} such that
for every n ≥ 1 {\displaystyle n\geq 1} . Furthermore, this is equivalent to the existence of a sequence of integers ( c 1 , c 2 , … ) {\displaystyle (c_{1},c_{2},\dots )} such that
for every n ≥ 1 {\displaystyle n\geq 1} . [ 4 ] If the values c n {\displaystyle c_{n}} are eventually zero, then the sequence ( a 1 , a 2 , … ) {\displaystyle (a_{1},a_{2},\dots )} satisfies a linear recurrence .
A direct relationship between the sequences ( b 1 , b 2 , … ) {\displaystyle (b_{1},b_{2},\dots )} and ( c 1 , c 2 , … ) {\displaystyle (c_{1},c_{2},\dots )} is given by the equality of generating functions
Below are examples of sequences ( a n ) n ≥ 1 {\displaystyle (a_{n})_{n\geq 1}} known to satisfy Gauss congruence.
Consider a discrete-time dynamical system , consisting of a set X {\displaystyle X} and a map T : X → X {\displaystyle T:X\to X} . We write T n {\displaystyle T^{n}} for the n {\displaystyle n} th iteration of the map, and say an element x {\displaystyle x} in X {\displaystyle X} has period n {\displaystyle n} if T n x = x {\displaystyle T^{n}x=x} .
Suppose the number of points in X {\displaystyle X} with period n {\displaystyle n} is finite for every n ≥ 1 {\displaystyle n\geq 1} . If a n {\displaystyle a_{n}} denotes the number of such points, then the sequence ( a n ) n ≥ 1 {\displaystyle (a_{n})_{n\geq 1}} satisfies Gauss congruence, and the associated sequence ( b n ) n ≥ 1 {\displaystyle (b_{n})_{n\geq 1}} counts orbits of size n {\displaystyle n} . [ 1 ]
For example, fix a positive integer α {\displaystyle \alpha } . If X {\displaystyle X} is the set of aperiodic necklaces with beads of α {\displaystyle \alpha } colors and T {\displaystyle T} acts by rotating each necklace clockwise by a bead, then a n = α n {\displaystyle a_{n}=\alpha ^{n}} and b n {\displaystyle b_{n}} counts Lyndon words of length n {\displaystyle n} in an alphabet of α {\displaystyle \alpha } letters.
Gauss congruence can be extended to sequences of rational numbers, where such a sequence ( a n ) n ≥ 1 {\displaystyle (a_{n})_{n\geq 1}} satisfies Gauss congruence at a prime p {\displaystyle p} if
for every n = p r {\displaystyle n=p^{r}} with r ≥ 1 {\displaystyle r\geq 1} , or equivalently, if a p r ≡ a p r − 1 mod p r {\displaystyle a_{p^{r}}\equiv a_{p^{r-1}}{\text{ mod }}p^{r}} for every r ≥ 1 {\displaystyle r\geq 1} .
A sequence of rational numbers ( a n ) n ≥ 1 {\displaystyle (a_{n})_{n\geq 1}} defined by a linear recurrence satisfies Gauss congruence at all but finitely many primes if and only if
where K {\displaystyle \mathbb {K} } is an algebraic number field with θ 1 , … , θ r ∈ K {\displaystyle \theta _{1},\dots ,\theta _{r}\in \mathbb {K} } , and q 1 , … , q r ∈ Q {\displaystyle q_{1},\dots ,q_{r}\in \mathbb {Q} } . [ 5 ] | https://en.wikipedia.org/wiki/Gauss_congruence |
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