Gas turbine

Examples of gas turbine configurations: (1)turbojet,(2)turboprop,(3)turboshaft(shown as electric generator), (4) high-bypassturbofan,(5) low-bypassafterburningturbofan

Agas turbine,gas turbine engine,or also known by its old nameinternal combustion turbine,is a type ofcontinuous flowinternal combustion engine.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:

• a rotatinggas compressor
• acombustor
• a compressor-drivingturbine.

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). Greaterthrust-to-weight ratiofor flight is achieved with the addition of anafterburner.

The basic operation of the gas turbine is aBrayton cyclewith air as theworking fluid:atmospheric air flows through the compressor that brings it to higher pressure;energyis 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 producingthrustin aturbojet engine,or rotating a second, independent turbine (known as apower 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 areopen systemsthat do not reuse the same air.

Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, andtanks.

Timeline of development

Sketch of John Barber's gas turbine, from his patent

• 50: Earliest records ofHero'sengine (aeolipile). It most likely served no practical purpose, and was rather more of a curiosity; nonetheless, it demonstrated an important principle of physics that all modern turbine engines rely on.
• 1000: The "Trotting Horse Lamp" (Chinese:Đèn kéo quân,zŏumădēng) was used by the Chinese at lantern fairs as early as theNorthern Song dynasty.When the lamp is lit, the heated airflow rises and drives an impeller with horse-riding figures attached on it, whose shadows are then projected onto the outer screen of the lantern.
• 1500: TheSmoke jackwas drawn byLeonardo da Vinci:Hot air from a fire rises through a single-stage axial turbine rotor mounted in the exhaust duct of the fireplace and turns the roasting spit by gear-chain connection.
• 1791: A patent was given toJohn Barber,an Englishman, for the first true gas turbine. His invention had most of the elements present in the modern day gas turbines. The turbine was designed to power ahorseless carriage.
• 1894: SirCharles Parsonspatented the idea of propelling a ship with asteam turbine,and built a demonstration vessel, theTurbinia,easily the fastest vessel afloat at the time.
• 1899:Charles Gordon Curtispatented the first gas turbine engine in the US.
• 1900:Sanford Alexander Mosssubmitted a thesis on gas turbines. In 1903, Moss became an engineer forGeneral Electric's Steam Turbine Department inLynn, Massachusetts.While there, he applied some of his concepts in the development of theturbocharger.
• 1903: A Norwegian,Ægidius Elling,built the first gas turbine that was able to produce more power than needed to run its own components, which was considered an achievement in a time when knowledge about aerodynamics was limited. Using rotary compressors and turbines it produced 8 kW (11 hp).
• 1904: A gas turbine engine designed byFranz Stolze,based on his earlier 1873 patent application, is built and tested in Berlin. The Stolze gas turbine was too inefficient to sustain its own operation.
• 1906: TheArmengaud-Lemale gas turbinetested in France. This was a relatively large machine which included a 25 stage centrifugal compressor designed byAuguste Rateauand built by theBrown Boveri Company.The gas turbine could sustain its own air compression but was too inefficient to produce useful work.
• 1910: The first operationalHolzwarth gas turbine(pulse combustion) achieves an output of 150 kW (200 hp). Planned output of the machine was 750 kW (1,000 hp) and its efficiency of 8% is below that of contemporary reciprocating engines.
• 1920s The practical theory of gas flow through passages was developed into the more formal (and applicable to turbines) theory of gas flow past airfoils byA. A. Griffithresulting in the publishing in 1926 ofAn Aerodynamic Theory of Turbine Design.Working testbed designs of axial turbines suitable for driving a propeller weredeveloped by the Royal Aeronautical Establishment.
• 1930: Having found no interest from the RAF for his idea,Frank Whittlepatentedthe design for a centrifugal gas turbine forjet propulsion.The first successful test run of his engine occurred in England in April 1937.
• 1932: TheBrown Boveri Companyof Switzerland starts sellingaxial compressorand turbine turbosets as part of the turbocharged steam generatingVelox boiler.Following the gas turbine principle, the steamevaporationtubes are arranged within the gas turbine combustion chamber; the first Velox plant is erected at a FrenchSteel millinMondeville, Calvados.
• 1936: The first constant flow industrial gas turbine is commissioned by the Brown Boveri Company and goes into service atSun Oil'sMarcus Hookrefinery inPennsylvania,US.
• 1937: Working proof-of-concept prototype turbojet engine runs in UK (Frank Whittle's) and Germany (Hans von Ohain'sHeinkel HeS 1).Henry Tizardsecures UK government funding for further development ofPower Jetsengine.
• 1939: The First 4 MW utility power generation gas turbine is built by the Brown Boveri Company for anemergency power station in Neuchâtel, Switzerland.The turbojet poweredHeinkel He 178,the world's first jet aircraft, makes its first flight.
• 1940:Jendrassik Cs-1,aturbopropengine, made its first bench run. The Cs-1 was designed by Hungarian engineerGyörgy Jendrassik,and was intended to power a Hungarian twin-engine heavy fighter, the RMI-1. Work on the Cs-1 stopped in 1941 without the type having powered any aircraft.
• 1944: TheJunkers Jumo 004engine enters full production, powering the first German military jets such as theMesserschmitt Me 262.This marks the beginning of the reign of gas turbines in the sky.
• 1946:National Gas Turbine Establishmentformed from Power Jets and the RAE turbine division to bring together Whittle andHayne Constant's work.InBeznau,Switzerland the first commercial reheated/recuperated unit generating 27 MW was commissioned.
• 1947: AMetropolitan VickersG1 (Gatric) becomes the first marine gas turbine when it completes sea trials on theRoyal Navy's M.G.B 2009 vessel.The Gatric was an aeroderivative gas turbine based on theMetropolitan Vickers F2jet engine.
• 1995:Siemensbecomes the first manufacturer of large electricity producing gas turbines to incorporatesingle crystalturbine bladetechnology into their production models, allowing higher operating temperatures and greater efficiency.
• 2011Mitsubishi Heavy Industriestests the first >60% efficiencycombined cyclegas turbine (the M501J) at its Takasago, Hyōgo, works.

Theory of operation

TheBrayton cycle

In an ideal gas turbine, gases undergo fourthermodynamicprocesses: anisentropiccompression, anisobaric(constant pressure) combustion, an isentropic expansion and isobaric heat rejection. Together, these make up theBrayton cycle,also known as the"constant pressure cycle".It is distinguished from theOtto cycle,in that all the processes (compression, ignition combustion, exhaust), occur at the same time, continuously.

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 axialcompressor). Heat is added in thecombustion chamberand thespecific volumeof 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 agas generator,with either anaxialorcentrifugaldesign, or a combination of the two.This air is then ducted into thecombustorsection which can be of aannular,can,orcan-annulardesign.In the combustor section, roughly 70% of the air from the compressor is ducted around the combustor itself for cooling purposes.The remaining roughly 30% the air is mixed with fuel and ignited by the already burningair-fuel mixture,which then expands producing power across theturbine.This expansion of the mixture then leaves the combustor section and has its velocity increased across theturbinesection 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.The remaining power is used to power what the engine is being used for, typically an aviation application, being thrust in aturbojet,driving the fan of aturbofan,rotor or accessory of aturboshaft,and gear reduction and propeller of aturboprop.

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 aturbopropengine there will be a particular balance between propeller power and jet thrust which gives the most economical operation. In aturbojet engineonly 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, therotational speedmust double. For example, large jet engines operate around 10,000–25,000 rpm, while micro turbines spin as fast as 500,000 rpm.

Mechanically, gas turbinescanbe considerably less complex thanReciprocating 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 10,000ℛℳfor materials, the Jumo 004 proved cheaper than theJunkers 213piston engine, which was 35,000ℛℳ,and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for theBMW 801.This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modernjet enginesor 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 relatedWobbe index.

The primary advantage of a gas turbine engine is its power to weight ratio. Since significant useful work can be generated by a relatively lightweight engine, gas turbines are perfectly suited for aircraft propulsion.

Thrust bearingsandjournal bearingsare a critical part of a design. They arehydrodynamic oil bearingsor oil-cooledrolling-element bearings.Foil bearingsare used in some small machines such as micro turbinesand also have strong potential for use in small gas turbines/auxiliary power units

Creep

A major challenge facing turbine design, especiallyturbine blades,is reducing thecreepthat 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 crystalsuperalloys.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 providethermal insulationof the blade and offeroxidationandcorrosionresistance. Thermal barrier coatings (TBCs) are often stabilizedzirconium dioxide-based ceramics and oxidation/corrosion resistant coatings (bond coats) typically consist ofaluminidesor 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). 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 Al₂O₃on 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.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.

Nickel-based superalloys boast improved strength and creep resistance due to their composition and resultantmicrostructure.The gamma (γ) FCC nickel is alloyed with aluminum and titanium in order to precipitate a uniform dispersion of the coherentNi₃(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 L1₂phase that makes it harder for dislocations to shear past it.FurtherRefractoryelements such asrheniumandrutheniumcan be added in solid solution to improve creep strength. The addition of these elements reduces the diffusion of the gamma prime phase, thus preserving thefatigueresistance, strength, and creep resistance.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 eliminateCoble creepand consequently deform by fewer modes – decreasing the creep rate.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.

Types

Jet engines

typical axial-flow gas turbine turbojet, theJ85,sectioned for display. Flow is left to right, multistage compressor on left, combustion chambers center, two-stage turbine on right

Airbreathingjet enginesare gas turbines optimized to produce thrust from the exhaust gases, or fromducted fansconnected to the gas turbines.Jet engines that produce thrust from the direct impulse of exhaust gases are often calledturbojets.While still in service with many militaries and civilian operators, turbojets have mostly been phased out in favor of theturbofanengine due to the turbojet's low fuel efficiency, and high noise.Those that generate thrust with the addition of a ducted fan are calledturbofansor (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 turbofanandhigh 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.

Gas turbines are also used in manyliquid-fuel rockets,where gas turbines are used to power aturbopumpto permit the use of lightweight, low-pressure tanks, reducing the empty weight of the rocket.

Turboprop engines

Aturbopropengine 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 highpower-to-weight ratioto drive a propeller, thus allowing a more powerful, but also smaller engine to be used.Turboprop engines are used on a wide range ofbusiness aircraftsuch as thePilatus PC-12,commuter aircraftsuch as theBeechcraft 1900,and small cargo aircraft such as theCessna 208 CaravanorDe Havilland Canada Dash 8,and large aircraft (typically military) such as theAirbus A400Mtransport,Lockheed AC-130and the 60-year-oldTupolev Tu-95strategic bomber. While military turboprop engines can vary, in the civilian market there are two primary engines to be found: thePratt & Whitney Canada PT6,afree-turbine turboshaftengine, and theHoneywell TPE331,afixed turbineengine (formerly designated as theGarrett AiResearch331).

Aeroderivative gas turbines

An LM6000 in an electricalpower plantapplication

Aeroderivative gas turbines are generally based on existing aircraft gas turbine engines and are smaller and lighter than industrial gas turbines.

Aeroderivatives are used in electrical power generation due to their ability to be shut down and handle load changes more quickly than industrial machines.They are also used in the marine industry to reduce weight. Common types include theGeneral Electric LM2500,General Electric LM6000,and aeroderivative versions of thePratt & Whitney PW4000,Pratt & Whitney FT4andRolls-Royce RB211.

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.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 automotiveturbochargeras the core component. A combustion chamber is fabricated and plumbed between the compressor and turbine sections.

More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft.TheSchrecklingdesignconstructs the entire engine from raw materials, including the fabrication of acentrifugal compressorwheel 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.

Auxiliary power units

Small gas turbines are used asauxiliary power units(APUs) to supply auxiliary power to larger, mobile, machines such as anaircraft,and are aturboshaftdesign.They supply:

• compressed air forair cycle machinestyle air conditioning and ventilation,
• compressed air start-up power for largerjet engines,
• 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

Gateway Generating Station,acombined-cyclegas-fired power stationin California, uses two GE 7F.04 combustion turbines to burnnatural gas.

GE H series power generation gas turbine: incombined cycleconfiguration, its highestthermodynamic efficiencyis 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 anelectric 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 portablecontainerconfigurations.

Gas turbines can be particularly efficient whenwaste heatfrom the turbine is recovered by a heat recovery steam generator (HRSG) to power a conventional steam turbine in acombined cycleconfiguration.The 605 MWGeneral Electric9HA achieved a 62.22% efficiency rate with temperatures as high as 1,540 °C (2,800 °F). For 2018, GE offers its 826 MW HA at over 64% efficiency in combined cycle due to advances inadditive manufacturingand combustion breakthroughs, up from 63.7% in 2017 orders and on track to achieve 65% by the early 2020s. In March 2018, GE Power achieved a 63.08% gross efficiency for its 7HA turbine.

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 acogenerationconfiguration: the exhaust is used for space or water heating, or drives anabsorption chillerfor cooling the inlet air and increase the power output, technology known asturbine 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 aspeaking 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 andload following power plantcapacity 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.

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.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 article: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 article:Turboshaft

Turboshaftengines 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 anauxiliary power unitin large commercial aircraft. A primary shaft carries the compressor and its turbine which, together with a combustor, is called aGas 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 article:Radial turbine

Scale jet engines

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.This engine can produce up to 22newtonsof thrust, and can be built by most mechanically minded people with basic engineering tools, such as ametal lathe.

Microturbines

Main article:Microturbine

Evolved from piston engineturbochargers,aircraftAPUsor smalljet engines,microturbinesare 25 to 500kilowattturbines the size of arefrigerator. Microturbines have around 15%efficiencieswithout arecuperator,20 to 30% with one and they can reach 85% combined thermal-electrical efficiency incogeneration.

External combustion

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 ahot 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 usingpulverized coalor finely ground biomass (such as sawdust) as a fuel. In the indirect system, aheat exchangeris used and only clean air with no combustion products travels through the power turbine. Thethermal efficiencyis 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 turbinesbased onheliumorsupercritical carbon dioxidealso hold promise for use with future high temperature solar and nuclear power generation.

In surface vehicles

MAZ-7907,atransporter erector launcherwith aturbine–electric powertrain

Gas turbines are often used onships,locomotives,helicopters,tanks,and to a lesser extent, on cars, buses, and motorcycles.

A key advantage of jets andturbopropsfor airplane propulsion – their superior performance at high altitude compared to piston engines, particularlynaturally aspiratedones – 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. Inseries hybridvehicles, 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 andultracapacitorscan supply power as needed, with the engine cycled on and off to run it only at high efficiency. The emergence of thecontinuously variable transmissionmay 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 theturbocharger.

The turbocharger is basically a compact and simple free shaft radial gas turbine which is driven by the piston engine'sexhaust 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 awastegateor by dynamically modifying the turbine housing's geometry (as in avariable 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 somesemi-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.

Passenger road vehicles (cars, bikes, and buses)

A number of experiments have been conducted with gas turbine poweredautomobiles,the largest byChrysler.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 companyBladon Jetshas 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.

The common turbocharger for gasoline or diesel engines is also a turbine derivative.

Concept cars

The 1950RoverJET1

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 inPopular Science,there was no further work, beyond the paper stage.

Early concepts (1950s/60s)

In 1950, designer F.R. Bell and Chief EngineerMaurice Wilksfrom British car manufacturersRoverunveiled the first car powered with a gas turbine engine. The two-seaterJET1had 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).The car ran onpetrol,paraffin (kerosene)ordieseloil, but fuel consumption problems proved insurmountable for a production car. JET1 is on display at the LondonScience Museum.

A French turbine-powered car, the SOCEMA-Grégoire, was displayed at the October 1952Paris Auto Show.It was designed by the French engineerJean-Albert Grégoire.

GM Firebird I

The first turbine-powered car built in the US was theGM Firebird Iwhich 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.Additional Firebird concept cars, each powered by gas turbines, were developed for the 1953, 1956 and 1959Motoramaauto shows. The GM Research gas turbine engine also was fitted to a series oftransit buses,starting with the Turbo-Cruiser I of 1953.

Engine compartment of a Chrysler 1963 Turbine car

Starting in 1954 with a modifiedPlymouth,the American car manufacturerChryslerdemonstrated severalprototype gas turbine-powered cars from the early 1950s through the early 1980s. Chrysler built fiftyChrysler Turbine Carsin 1963 and conducted the only consumer trial of gas turbine-powered cars.Each of their turbines employed a unique rotatingrecuperator,referred to as a regenerator that increased efficiency.

In 1954,Fiatunveiled aconcept carwith a turbine engine, calledFiat 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.

In the 1960s, Ford and GM also were developing gas turbine semi-trucks. Ford displayed the Big Red at the1964 World's Fair.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.The Chevrolet division of GM built theTurbo Titanseries 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), andTurbo Titan III(1965, GT-309 engine); in addition, the GM Bison gas turbine truck was shown at the 1964 World's Fair.

Emissions and fuel economy (1970s/80s)

As a result of the U.S.Clean Air ActAmendments of 1970, research was funded into developing automotive gas turbine technology.Design concepts and vehicles were conducted byChrysler,General Motors,Ford(in collaboration withAiResearch), andAmerican Motors(in conjunction withWilliams Research).Long-term tests were conducted to evaluate comparable cost efficiency.SeveralAMC Hornetswere powered by a small Williams regenerative gas turbine weighing 250 lb (113 kg) and producing 80 hp (60 kW; 81 PS) at 4450 rpm.

In 1982, General Motors used anOldsmobile Delta 88powered by a gas turbine using pulverised coal dust. This was considered for the United States and the western world to reduce dependence onmiddle east oil at the time

Toyotademonstrated several gas turbine powered concept cars, such as theCentury gas turbine hybridin 1975, theSports 800 Gas Turbine Hybridin 1979 and theGTVin 1985. No production vehicles were made. The GT24 engine was exhibited in 1977 without a vehicle.

Later development

In the early 1990s,Volvointroduced theVolvo ECCwhich was a gas turbine poweredhybrid electric vehicle.

In 1993,General Motorsdeveloped a gas turbine powered EV1 serieshybrid—as a prototype of theGeneral Motors EV1.AWilliams International40 kW turbine drove an alternator which powered the battery–electricpowertrain.The turbine design included a recuperator. In 2006, GM went into theEcoJet concept carproject withJay Leno.

At the2010 Paris Motor ShowJaguardemonstrated itsJaguar C-X75concept car. This electrically poweredsupercarhas 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).

Racing cars

The 1967STP Oil Treatment Specialon display at theIndianapolis Motor SpeedwayHall of Fame Museum, with thePratt & Whitneygas turbine shown

A 1968Howmet TX,the only turbine-powered race car to have won a race

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.The first race car fitted with a turbine for the goal of actual racing was by Rover and theBRMFormula Oneteam joined forces to produce theRover-BRM,a gas turbine powered coupe, which entered the1963 24 Hours of Le Mans,driven byGraham HillandRichie 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, theHowmet TX,which ran several American and European events, including two wins, and also participated in the1968 24 Hours of Le Mans.The cars usedContinentalgas turbines, which eventually set sixFIAland speed records for turbine-powered cars.

Foropen wheel racing,1967's revolutionarySTP-Paxton Turbocarfielded by racing and entrepreneurial legendAndy Granatelliand driven byParnelli Jonesnearly won theIndianapolis 500;thePratt & Whitney ST6B-62powered 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 STPLotus 56turbine car won the Indianapolis 500 pole position even though new rules restricted the air intake dramatically. In 1971Team LotusprincipalColin Chapmanintroduced theLotus 56BF1 car, powered by aPratt & Whitney STN 6/76gas turbine. Chapman had a reputation of building radical championship-winning cars, but had to abandon the project because there were too many problems withturbo lag.

Buses

General Motors fitted theGT-30x series of gas turbines (branded "Whirlfire" )to several prototype buses in the 1950s and 1960s, includingTurbo-Cruiser I(1953, GT-300);Turbo-Cruiser II(1964, GT-309); Turbo-Cruiser III (1968, GT-309);RTX(1968, GT-309); andRTS 3T(1972).

The arrival of theCapstone Turbinehas 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, andDesignLine Corporationin 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 Italyis using serial hybrid buses powered by microturbines on routes through the historical sections of the city.

Motorcycles

TheMTT Turbine Superbikeappeared 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.

Trains

Main article:Gas turbine locomotive

Several locomotive classes have been powered by gas turbines, the most recent incarnation beingBombardier'sJetTrain.

Tanks

Marines from 1st Tank Battalion load aHoneywell AGT1500multi-fuel turbine back into an M1 Abrams tank at Camp Coyote, Kuwait, February 2003

The Third ReichWehrmacht Heer's development division, theHeereswaffenamt(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, theBMW 003-basedGT 101,was meant for installation in thePanther tank.Towards the end of the war, aJagdtigerwas fitted with one of the aforementioned gas turbines.

The second use of a gas turbine in an armored fighting vehicle was in 1954 when a unit, PU2979, specifically developed for tanks byC. A. Parsons and Company,was installed and trialed in a BritishConqueror tank.TheStridsvagn 103was developed in the 1950s and was the first mass-produced main battle tank to use a turbine engine, theBoeing T50.Since then, gas turbine engines have been used asauxiliary power unitsin some tanks and as main powerplants in Soviet/RussianT-80sand U.S.M1 Abramstanks, among others. They are lighter and smaller thandiesel enginesat 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-poweredT-90(based on theT-72), while Ukraine has developed the diesel-powered T-80UD and T-84 with nearly the power of the gas-turbine tank. The FrenchLeclerc 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 removesturbo 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.

Marine applications

Main article:Marine propulsion

Naval

The Gas turbine from MGB 2009

Gas turbines are used in manynaval vessels,where they are valued for their highpower-to-weight ratioand their ships' resulting acceleration and ability to get underway quickly.

The first gas-turbine-powered naval vessel was theRoyal Navy'smotor gunboatMGB 2009(formerlyMGB 509) converted in 1947.Metropolitan-Vickersfitted theirF2/3jet engine with a power turbine. TheSteam Gun BoatGrey Goosewas converted to Rolls-Royce gas turbines in 1952 and operated as such from 1953.TheBold classFast Patrol BoatsBold PioneerandBold Pathfinderbuilt in 1953 were the first ships created specifically for gas turbine propulsion.

The first large-scale, partially gas-turbine powered ships were the Royal Navy'sType 81(Tribal class)frigateswithcombined steam and gaspowerplants. The first,HMSAshantiwas commissioned in 1961.

TheGerman Navylaunched the firstKöln-classfrigatein 1961 with 2Brown, Boveri & Ciegas turbines in the world's firstcombined diesel and gaspropulsion system.

TheSoviet Navycommissioned in 1962 the first of 25Kashin-classdestroyerwith 4 gas turbines incombined gas and gaspropulsion 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.

Project 61 large ASW ship,Kashin-classdestroyer

TheDanish Navyhad 6Søløven-class torpedo boats (the export version of the BritishBrave class fast patrol boat) in service from 1965 to 1990, which had 3Bristol Proteus(later RR Proteus) Marine Gas Turbines rated at 9,510 kW (12,750 shp) combined, plus twoGeneral MotorsDiesel engines, rated at 340 kW (460 shp), for better fuel economy at slower speeds.And they also produced 10 Willemoes Class Torpedo / Guided Missile boats (in service from 1974 to 2000) which had 3Rolls-RoyceMarine 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.

TheSwedish Navyproduced 6 Spica-class torpedo boats between 1966 and 1967 powered by 3Bristol SiddeleyProteus 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.

TheFinnish Navycommissioned twoTurunmaa-classcorvettes,TurunmaaandKarjala,in 1968. They were equipped with one 16,410 kW (22,000 shp)Rolls-Royce OlympusTM1 gas turbine and threeWärtsilämarine 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. TheTurunmaas were decommissioned in 2002.Karjalais today amuseum shipinTurku,andTurunmaaserves as a floating machine shop and training ship for Satakunta Polytechnical College.

The next series of major naval vessels were the four CanadianIroquois-classhelicopter 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.

An LM2500 gas turbine onUSSFord

The first U.S. gas-turbine powered ship was theU.S. Coast Guard'sPoint Thatcher,a cutter commissioned in 1961 that was powered by two 750 kW (1,000 shp) turbines utilizing controllable-pitch propellers.The largerHamilton-classHigh Endurance Cutters,was the first class of larger cutters to utilize gas turbines, the first of which (USCGCHamilton) was commissioned in 1967. Since then, they have powered theU.S. Navy'sOliver Hazard Perry-class frigates,SpruanceandArleigh Burke-classdestroyers, andTiconderoga-classguided missile cruisers.USSMakin Island,a modifiedWasp-classamphibious 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.

Civilian maritime

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 BritishRoyal Navyand 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 tankerAuris,12,290deadweight 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 byHawthorn LeslieatHebburn-on-Tyne,UK, in accordance with plans and specifications drawn up by theAnglo-Saxon Petroleum Companyand launched on the UK'sPrincess 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.TheAurisoperated 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 byBritish Thompson-Houston CompanyinRugby.Following successful sea trials off the Northumbrian coast, theAurisset sail from Hebburn-on-Tyne in October 1951 bound forPort Arthurin the US and thenCuracaoin the southern Caribbean returning toAvonmouthafter 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,Osloand Southampton covering a total of 13,211 nautical miles. TheAuristhen 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.

TheUnited States Maritime Commissionwere looking for options to update WWIILiberty ships,and heavy-duty gas turbines were one of those selected. In 1956 theJohn Sergeantwas lengthened and equipped with aGeneral Electric4,900 kW (6,600 shp) HD gas turbine with exhaust-gas regeneration, reduction gearing and avariable-pitch propeller.It operated for 9,700 hours using residual fuel (Bunker C) for 7,000 hours.Fuel efficiencywas on a par with steam propulsion at 0.318 kg/kW (0.523 lb/hp) per hour,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.TheJohn Sergeantwas scrapped in 1972 at Portsmouth PA.

Boeing Jetfoil 929-100-007UrzelaofTurboJET

Boeinglaunched its first passenger-carryingwaterjet-propelledhydrofoilBoeing 929,in April 1974. Those ships were powered by twoAllison 501-KF gas turbines.

Between 1971 and 1981,Seatrain Linesoperated a scheduledcontainerservice 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 twinPratt & Whitneygas turbines of the FT 4 series. The four ships in the class were namedEuroliner,Eurofreighter,AsialinerandAsiafreighter.Following the dramaticOrganization 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.

The first passenger ferry to use a gas turbine was theGTSFinnjet,built in 1977 and powered by twoPratt & WhitneyFT 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 acombined diesel–electric and gaspropulsion. Another example of commercial use of gas turbines in a passenger ship isStena Line'sHSS classfastcraft ferries. HSS 1500-classStena Explorer,Stena VoyagerandStena Discoveryvessels usecombined gas and gassetups of twinGELM2500plus GE LM1600 power for a total of 68,000 kW (91,000 shp). The slightly smaller HSS 900-classStena Carisma,uses twinABB–STALGT35 turbines rated at 34,000 kW (46,000 shp) gross. TheStena Discoverywas withdrawn from service in 2007, another victim of too high fuel costs.

In July 2000, theMillenniumbecame the firstcruise shipto 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 aCOGES(combined gas electric and steam) configuration. Propulsion was provided by two electrically driven Rolls-Royce Mermaid azimuth pods. The linerRMSQueen Mary 2uses a combined diesel and gas configuration.

In marine racing applications the 2010 C5000 Mystic catamaranMiss GEICOuses two Lycoming T-55 turbines for its power system.

Advances in technology

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 (specificallycomputational fluid dynamicsandfinite element analysis) and the development of advanced materials: Base materials with superior high-temperature strength (e.g.,single-crystalsuperalloysthat exhibityield strength anomaly) orthermal barrier coatingsthat protect the structural material from ever-higher temperatures. These advances allow highercompression ratiosand 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 gasturbine 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.

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 Industriesachieved a turbine inlet temperature of 1,600 °C (2,900 °F) on a 320 megawatt gas turbine, and 460 MW in gas turbinecombined-cyclepower generation applications in which grossthermal efficiencyexceeds 60%.

Compliantfoil bearingswere 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 andpower switchingtechnology have enabled the development of commercially viable electricity generation by microturbines for distribution and vehicle propulsion.

In 2013, General Electric started the development of theGE9Xwith a compression ratio of 61:1.

Advantages and disadvantages

The following are advantages and disadvantages of gas-turbine engines:

Advantages include:

• Very highpower-to-weight ratiocompared to reciprocating engines.
• Smaller than most reciprocating engines of the same power rating.
• Smooth rotation of the main shaft produces far less vibration than a reciprocating engine.
• Fewer moving parts than reciprocating engines results in lower maintenance cost and higher reliability/availability over its service life.
• Greater reliability, particularly in applications where sustained high power output is required.
• Waste heat is dissipated almost entirely in the exhaust. This results in a high-temperature exhaust stream that is very usable for boiling water in acombined cycle,or forcogeneration.
• Lower peak combustion pressures than reciprocating engines in general.
• High shaft speeds in smaller "free turbine units", although larger gas turbines employed in power generation operate at synchronous speeds.
• Low lubricating oil cost and consumption.
• Can run on a wide variety of fuels.
• Very low toxic emissions of CO and HC due to excess air, complete combustion and no "quench" of the flame on cold surfaces.

Disadvantages include:

• Core engine costs can be high due to the use of exotic materials, especially in applications where high reliability is required (e.g. aircraft propulsion)
• Less efficient than reciprocating engines at idle speed.
• Longer startup than reciprocating engines.
• Less responsive to changes in power demand compared with reciprocating engines.
• Characteristic whine can be hard to suppress. The exhaust (particularly on turbojets) can also produce a distinctive roaring sound.

Major manufacturers

• Siemens Energy
• Ansaldo
• Mitsubishi Heavy Industries
• Rolls-Royce
• General Electric
• Silmash
• ODK
• Pratt & Whitney
• P&W Canada
• Solar Turbines
• Alstom
• Zorya-Mashproekt
• MTU Aero Engines
• MAN Turbo
• IHI Corporation
• Kawasaki Heavy Industries
• HAL
• BHEL
• MAPNA
• Techwin
• Doosan Heavy
• Shanghai Electric
• Harbin Electric
• AECC

Testing

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,ASMEhas 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.

See also

• List of aircraft engines
• Centrifugal compressor
• Gas turbine modular helium reactor
• Pneumatic motor
• Pulsejet
• Steam turbine
• Turbine engine failure
• Wind turbine

Further reading

• Stationary Combustion Gas Turbines including Oil & Over-Speed Control System description
• "Aircraft Gas Turbine Technology" by Irwin E. Treager, McGraw-Hill, Glencoe Division, 1979,ISBN0-07-065158-2.
• "Gas Turbine Theory" by H.I.H. Saravanamuttoo, G.F.C. Rogers and H. Cohen, Pearson Education, 2001, 5th ed.,ISBN0-13-015847-X.
• Leyes II, Richard A.; Fleming, William A. (1999).The History of North American Small Gas Turbine Aircraft Engines.Washington, DC: Smithsonian Institution.ISBN978-1-56347-332-6.
• R. M. "Fred" Klaass and Christopher DellaCorte, "The Quest for Oil-Free Gas Turbine Engines," SAE Technical Papers, No. 2006-01-3055, available at sae.org
• "Model Jet Engines" by Thomas KampsISBN0-9510589-9-1Traplet Publications
• Aircraft Engines and Gas Turbines,Second Edition by Jack L. Kerrebrock, The MIT Press, 1992,ISBN0-262-11162-4.
• "Forensic Investigation of a Gas Turbine Event"by John Molloy, M&M Engineering
• "Gas Turbine Performance, 2nd Edition "by Philip Walsh and Paul Fletcher, Wiley-Blackwell, 2004ISBN978-0-632-06434-2
• Advanced Technologies for Gas Turbines (Report). Washington, DC: The National Academies Press. 2020.doi:10.17226/25630.ISBN978-0-309-66422-6.

External links

• Gas turbineatCurlie
• Armagnac, Alden P. (December 1939)."New Era In Power To Turn Wheels".Popular Science.p. 81.
• Technology Speed of Civil Jet Engines
• MIT Gas Turbine LaboratoryArchived21 July 2010 at theWayback Machine
• MIT Microturbine research
• California Distributed Energy Resource guide – Microturbine generators
• Introduction to how a gas turbine works from "how stuff works"Archived16 June 2008 at theWayback Machine
• Aircraft gas turbine simulator for interactive learning
• An online handbook on stationary gas turbine technologies compiled by the US DOE.Archived1 July 2017 at theWayback Machine