Editing Gas turbine (section)

==Types==

===Jet engines===
[[File:J85 ge 17a turbojet engine.jpg|thumb|typical axial-flow gas turbine turbojet, the [[General Electric J85|J85]], sectioned for display. Flow is left to right, multistage compressor on left, combustion chambers center, two-stage turbine on right]]

Airbreathing [[jet engine]]s are gas turbines optimized to produce thrust from the exhaust gases, or from [[ducted fan]]s connected to the gas turbines.<ref>{{cite tech report |url=https://pure.manchester.ac.uk/ws/files/83828293/Modelling_of_a_Turbojet_Gas_Turbine_Engine.pdf |title=Modelling of a turbojet gas turbine engine |last1=Klein |first1=D. |last2=Abeykoon |first2=C. |publisher=University of Manchester |year=2015}}</ref><ref name = "Dk">{{cite journal|last=Dick |first=Erik |title=Thrust Gas Turbines |journal=Fundamentals of Turbomachines |volume=109 |year=2015}}</ref> Jet engines that produce thrust from the direct impulse of exhaust gases are often called [[turbojet]]s. 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.<ref name=":0">{{Cite book |url=https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-32-AMT-Powerplant-Vol-1.pdf |title=8083 Aviation Maintenance Technician Handbook–Powerplant Volume 1 |publisher=Federal Aviation Administration |year=2018 |isbn=978-0983865810 |location=USA}}</ref> Those that generate thrust with the addition of a ducted fan are called [[turbofan]]s 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.<ref name=":0" /><ref name=":1">{{Cite book |title=A&P Powerplant Textbook |publisher=Jeppeson |year=2011 |isbn=978-0884873389 |edition=3rd}}</ref>

Gas turbines are also used in many [[liquid-fuel rocket]]s, 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.

===Turboprop engines===
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.<ref name=":1" /> 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===
[[File:General Electric LM6000.jpg|thumb|An LM6000 in an electrical [[power plant]] application]]

Aeroderivative gas turbines are generally based on existing aircraft gas turbine engines and are smaller and lighter than industrial gas turbines.<ref name="Robb">{{cite web|url=https://www.turbomachinerymag.com/aeroderivative-gas-turbines/|title=Aeroderivative gas turbines|last=Robb|first=Drew|date=December 1, 2017|work=Turbomachinery International Magazine|access-date=26 June 2020}}</ref>

Aeroderivatives are used in electrical power generation due to their ability to be shut down and handle load changes more quickly than industrial machines.<ref>{{cite conference |first=R. P. |last=Smith |title= Power generation using high efficiency aeroderivative gas turbines |conference= International Conference on Opportunities and Advances in International Electric Power Generation (Conf. Publ. No. 419) |location= Durham, UK |year= 1996 |pages= 104–110 |doi= 10.1049/cp:19960128 |url= https://ieeexplore.ieee.org/document/643453 |url-access= subscription}}</ref> 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]].<ref name="Robb"/>

===Amateur gas turbines===
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.<ref name="latexiron" >{{cite web|url= http://www.vb.n00bunlimited.net/vBTube.php?do=view&vidid=5iQRdBE3IS0 |archive-url= https://archive.today/20130413204957/http://www.vb.n00bunlimited.net/vBTube.php?do=view&vidid=5iQRdBE3IS0 |url-status= dead |archive-date= 13 April 2013 |title=Vulcan APU startup |format=video}}</ref><ref name="Internal Fire, Proteus">{{cite web|title=Bristol Siddeley Proteus |year=1999 |publisher=Internal Fire Museum of Power |url=http://www.internalfire.com/modules.php?name=Content&pa=showpage&pid=136 |url-status=dead |archive-url=https://web.archive.org/web/20090118165708/http://www.internalfire.com/modules.php?name=Content&pa=showpage&pid=136 |archive-date=18 January 2009}}</ref> 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.<ref name="Scrapheap Challenge, gas turbine go-cart" >{{cite episode|title=Jet Racer |series=Scrapheap Challenge |series-link=Scrapheap Challenge |season=6 |url= http://www.channel4.com/programmes/scrapheap-challenge/4od#3349454 |location=UK |year=2003 |access-date=13 March 2016}}</ref>

More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft.<ref name="Schreckling, Gas Turbines for Model Aircraft" >{{cite book |last=Schreckling |first=Kurt |title=Gas Turbines for Model Aircraft |year=1994 |publisher=Traplet Publications |isbn=978-0-9510589-1-6}}</ref> The [[Kurt Schreckling|Schreckling]] design<ref name="Schreckling, Gas Turbines for Model Aircraft" /> 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.<ref name="Kamps" >{{cite book|title=Model Jet Engines |isbn=978-1-900371-91-9 |year=2005 |last=Kamps |first=Thomas |publisher=Traplet Publications}}</ref>

===Auxiliary power units===
Small gas turbines are used as [[auxiliary power unit]]s (APUs) to supply auxiliary power to larger, mobile, machines such as an [[aircraft]], and are a [[turboshaft]] design.<ref name=":0" /> They supply:
* compressed air for [[air cycle machine]] style air conditioning and ventilation,
* compressed air start-up power for larger [[jet engine]]s,
* mechanical (shaft) power to a gearbox to drive shafted accessories, and
* electrical, hydraulic and other power-transmission sources to consuming devices remote from the APU.

===Industrial gas turbines for power generation===
[[File:Gateway Generating Station rectified.jpg|thumb|[[Gateway Generating Station]], a [[combined cycle power generation|combined-cycle]] [[gas-fired power plant|gas-fired power station]] in California, uses two GE 7F.04 combustion turbines to burn [[natural gas]].]]
[[File:GE H series Gas Turbine.jpg|thumb|GE H series power generation gas turbine: in [[combined cycle]] configuration, its highest [[thermodynamic efficiency]] is 62.22%]]{{See also|Gas-fired power plant}}
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 [[Intermodal container|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.<ref>{{cite web |url= http://memagazineblog.org/2012/07/01/efficiency-by-the-numbers/ |archive-url= https://web.archive.org/web/20130207053320/http://memagazineblog.org/2012/07/01/efficiency-by-the-numbers/ |url-status= dead |archive-date= 7 February 2013 |title= Efficiency by the Numbers |first=Lee S. |last=Langston |date= July 2012 }}</ref> The 605 MW [[General Electric]] 9HA achieved a 62.22% efficiency rate with temperatures as high as {{convert|2800|°F|°C|order=flip}}.<ref>{{cite press release |url=http://www.gereports.com/bouchain/ |title=Here's Why The Latest Guinness World Record Will Keep France Lit Up Long After Soccer Fans Leave |first=Tomas |last=Kellner |publisher=[[General Electric]] |date=17 June 2016 |access-date=21 June 2016 |archive-date=16 June 2017 |archive-url=https://web.archive.org/web/20170616021542/http://www.gereports.com/bouchain/ |url-status=dead }}</ref>
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.<ref>{{cite press release |url= https://www.genewsroom.com/press-releases/ha-technology-now-available-industry-first-64-percent-efficiency-284144 |title= HA technology now available at industry-first 64 percent efficiency |date=4 December 2017 |publisher= GE Power}}</ref>
In March 2018, GE Power achieved a 63.08% gross efficiency for its 7HA turbine.<ref>{{cite press release |url= https://www.ge.com/news/press-releases/ges-ha-gas-turbine-delivers-second-world-record-efficiency/ |title= GE's HA Gas Turbine Delivers Second World Record for Efficiency |publisher= GE Power |date= March 27, 2018}}</ref>

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 plant]]s, 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&nbsp;megawatts of electric power and has 35–40% [[thermodynamic efficiency]].<ref name=siemens>{{cite web |first1=Phil |last1=Ratliff |first2=Paul |last2=Garbett |first3=Willibald |last3=Fischer |title=The New Siemens Gas Turbine SGT5-8000H for More Customer Benefit |work=VGB PowerTech |publisher=Siemens Power Generation |date=September 2007 |url=http://www.energy.siemens.com/us/pool/hq/power-generation/gas-turbines/downloads/SGT5-8000H_benefits.pdf |access-date=17 July 2010 |archive-date=13 August 2011 |archive-url=https://web.archive.org/web/20110813030259/http://www.energy.siemens.com/us/pool/hq/power-generation/gas-turbines/downloads/SGT5-8000H_benefits.pdf |url-status=dead }}</ref>

===Industrial gas turbines for mechanical drive===
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|date=December 2012}} 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.

====Compressed air energy storage====
{{Main|Compressed air energy storage}}

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===
{{Main|Turboshaft}}
[[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.

===Radial gas turbines===
{{Main|Radial turbine}}

===Scale jet engines===
[[File:DH Goblin annotated colour cutaway.png|thumb|Scale jet engines are scaled down versions of this early full scale engine]]

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.<ref name="Schreckling, Gas Turbines for Model Aircraft" /> This engine can produce up to 22 [[newton (unit)|newtons]] of thrust, and can be built by most mechanically minded people with basic engineering tools, such as a [[metal lathe]].<ref name="Schreckling, Gas Turbines for Model Aircraft" />

===Microturbines===
{{Main|Microturbine}}

Evolved from piston engine [[turbocharger]]s, aircraft [[auxiliary power unit|APU]]s or small [[jet engine]]s, [[microturbine]]s are 25 to 500 [[kilowatt]] turbines the size of a [[refrigerator]].<!--<ref name=wbdg22dec2016/>-->
Microturbines have around 15% [[engine efficiency|efficiencies]] without a [[recuperator]], 20 to 30% with one and they can reach 85% combined thermal-electrical efficiency in [[cogeneration]].<ref name=wbdg22dec2016>{{cite news |url= https://www.wbdg.org/resources/microturbines |title= Microturbines |first=Barney L. |last=Capehart |date=22 December 2016 |publisher=National Institute of Building Sciences |work=Whole Building Design Guide}}</ref>