Gas turbine use in military technology A gas turbine , also called a combustion turbine , is a type of internal combustion engine . It has an upstream rotating compressor coupled to a downstream turbine , and a combustion chamber in - between . The basic operation of the gas turbine is similar to that of the steam power plant except that air is used instead of water . Fresh atmospheric air flows through a compressor that brings it to higher pressure . Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high - temperature flow . This high - temperature high - pressure gas enters a turbine , where it expands down to the exhaust pressure , producing a shaft work output in the process . The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft . The energy that is not used for shaft work comes out in the exhaust gases , so these have either a high temperature or a high velocity . The purpose of the gas turbine determines the design so that the most desirable energy form is maximized . Gas turbines are used to power aircraft , trains , ships , electrical generators , or even tank s . Theory of operation . Gases passing through an ideal gas turbine undergo three thermodynamic processes . These are isentropic compression , isobaric ( constant pressure ) combustion and isentropic expansion . Together , these make up the Brayton cycle . In a practical gas turbine , gases are first accelerated in either a centrifugal or axial compressor . These gases are then slowed using a diverging nozzle known as a diffuser ; these processes increase the pressure and temperature of the flow . In an ideal system , this is isentropic . However , in practice , energy is lost to heat , due to friction and turbulence . Gases then pass from the diffuser to a combustion chamber , or similar device , where heat is added . In an ideal system , this occurs at constant pressure ( isobaric heat addition ) . As there is no change in pressure the specific volume of the gases increases . In practical situations this process is usually accompanied by a slight loss in pressure , due to friction . Finally , this larger volume of gases is expanded and accelerated by nozzle guide vanes before energy is extracted by a turbine . In an ideal system , these gases are expanded isentropically and leave the turbine at their original pressure . In practice this process is not isentropic as energy is once again lost to friction and turbulence . If the device has been designed to power a shaft as with an industrial generator or a turboprop , the exit pressure will be as close to the entry pressure as possible . In practice it is necessary that some pressure remains at the outlet in order to fully expel the exhaust gases . In the case of a jet 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 to provide a jet that can , for example , be used to propel an aircraft . As with all cyclic heat engines , higher combustion temperatures can allow for greater efficiencies . However , temperatures are limited by ability of the steel , nickel , ceramic , or other materials that make up the engine to withstand high temperatures and stresses . To combat this many turbines feature complex blade cooling systems . As a general rule , the smaller the engine , the higher the rotation rate of the shaft ( s ) must be to maintain 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 rpm , while micro turbines spin as fast as 500 , 000 rpm . Mechanically , gas turbines can be considerably less complex than internal combustion piston engines . Simple turbines might have one moving part : the shaft / compressor / turbine / alternative - rotor assembly ( see image above ) , not counting the fuel system . However , the required precision manufacturing for components and temperature resistant alloys necessary for high efficiency often make the construction of a simple turbine more complicated than piston engines . More sophisticated turbines ( such as those found in modern jet engines ) may have multiple shafts ( spools ) , hundreds of turbine blades , movable stator blades , and a vast system of complex piping , combustors and heat exchangers . Types of gas turbines . Jet engines . Airbreathing jet engines are gas turbines optimized to produce thrust from the exhaust gases , or from ducted fan s connected to the gas turbines . Jet engines that produce thrust from the direct impulse of exhaust gases are often called turbojets , whereas those that generate thrust with the addition of a ducted fan are often called turbofans or ( rarely ) fan - jets . Gas turbines are also used in many liquid propellant rocket s , the gas turbines are used to power a turbopump to permit the use of lightweight , low pressure tanks , which saves considerable dry mass . Turboprop engines . A turboprop engine is a type of turbine engine which drives an external aircraft propeller using a reduction gear . Turboprop engines are generally used on small subsonic aircraft , but some large military and civil aircraft , such as the Airbus A400M , Lockheed L - 188 Electra and Tupolev Tu - 95 , have also used turboprop power . Aeroderivative gas turbines . Aeroderivatives are also 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 . The General Electric LM2500 , General Electric LM6000 , Rolls - Royce RB211 and Rolls - Royce Avon are common models of this type of machine . Gas turbines in surface vehicles . Gas turbines are often used on ships , locomotives , helicopter s , tank s , and to a lesser extent , on cars , buses , and motorcycles . A key advantage of jets and turboprops for aeroplane 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 . Tanks . The German Army ' s development division , the Heereswaffenamt ( Army Ordnance Board ) , studied a number of gas turbine engines for use in tanks starting in mid - 1944 . The first gas turbine engines used for armoured fighting vehicle GT 101 was installed in the Panther tank . The second use of a gas turbine in an armoured fighting vehicle was in 1954 when a unit , PU2979 , specifically developed for tanks by C . A . Parsons & Co . , was installed and trialled in a British Conqueror tank . The Stridsvagn 103 was developed in the 1950s and was the first mass - produced main battle tank to use a turbine engine . Since then , gas turbine engines have been used as APUs in some tanks and as main powerplants in Soviet / Russian T - 80 s and U . S . M1 Abrams tanks , among others . They are lighter and smaller than diesels 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 favour 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 MBT ' 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 powerplant 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 . Marine applications . Naval . 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 Gun Boat " 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 . The Bold class Fast Patrol Boat s " Bold Pioneer " and " Bold Pathfinder " built 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 ' s Type 81 ( Tribal class ) frigate s with combined steam and gas powerplants . The first , HMS " Ashanti " was commissioned in 1961 . The German Navy launched the first in 1961 with 2 Brown , Boveri & Cie gas turbines in the worlds first combined diesel and gas propulsion system . 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 combined , plus two General Motors Diesel engines , rated at , 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 3 Rolls Royce Marine Proteus Gas Turbines also rated at , same as the Søløven class boats , and 2 General Motors Diesel Engines , rated at , also for improved fuel economy at slow speeds . The Swedish Navy produced 6 Spica - class torpedo boats between 1966 and 1967 powered by 3 Bristol Siddeley Proteus 1282 turbines , each delivering . 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 . The Finnish Navy commissioned two Turunmaa class corvette s , Turunmaa and Karjala , in 1968 . They were equipped with one Rolls - Royce Olympus TMB3 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 Turunmaas were paid off 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 , a cutter commissioned in 1961 that was powered by two turbines utilizing controllable pitch propellers . 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 " Perry " - class frigates , " Spruance " - class and " Arleigh Burke " - class destroyer s , 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 presence of sea salt in air and fuel and use of cheaper fuels . 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 ( specifically CFD and finite element analysis ) and the development of advanced materials : Base materials with superior high temperature strength ( e . g . , single - crystal superalloy s 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 . 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 Industries achieved a turbine inlet temperature of 1 , 600 °C on a 320 megawatt gas turbine , and 460 MW in gas turbine combined - cycle power generation applications in which gross thermal efficiency exceeds 60 % . Compliant foil bearing s 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 micro turbines for distribution and vehicle propulsion . Advantages and disadvantages of gas turbine engines . Reference for this section : External links . Turbine Inlet Air Cooling