SEMINAR TURBINE ENGINES

8/8/2019 SEMINAR TURBINE ENGINES

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Turbojet and Turbofan Engine Performance

Increases through Turbine Burners

SEMINAR GUIDE: PROF. G.P. LOHARSUBMITTED BY:

ADITYA SANGOTRA

T.E.MECHANICAL ENGG.

ROLL NO 08ME201


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Introductiony Of the various means of producing mechanical power

the turbines are more satisfactory. The absence of

reciprocating and rubbing members means thatbalancing problems are few, than the lubricating oilconsumption is exceptionally low and that reliabilitycan be high. The gas turbine obtains its power byutilizing energy of burnt gases and air which are athigh temperature and pressure by expanding throughseveral rings of fixed and moving blades.


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Basic Operationsy Agas turbine has a compressor to draw in and

compress air; a combustor (or burner) to add fuel toheat the compressed air; and a turbine to extract powerfrom the hot air flow. The gas turbine is an internalcombustion (IC) engine employing a continuouscombustion process. This differs from the intermittentcombustion occurring in diesel and automotive IC

engines.A

bout 2/3rds of the shaft power produced bythe turbine is used to run the compressor, leavingabout 1/3rd available to turn a genset to produce power.


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BRAYTON CYCLEy The Brayton cycle (1876), shown in graphic form as a

pressure-volume diagram, is a representation of theproperties of a fixed amount of air as it passes through a gas

turbine in operation.y Air is compressed from point 1 to point 2. This increases the

pressure as the volume of space occupied by the air isreduced. The air is then heated at constant pressure from 2to 3.

y The hot compressed air at point 3 is then allowed to expand(from point 3 to 4) reducing the pressure and temperatureand increasing its volume. In the engine, this representsflow through the turbine to point 3' and then flow throughthe power turbine to point 4 to turn a shaft.


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HISTORYy During the last eighties the turbine engine came to

existence. At that time the turbine engine was using a

single spool.y Lack of required power and thrust produced by single

spool engine lead to the development in this field anda double spool engine came to existence.


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DEVELOPMENTy 1)Regeneration: It involves the installation of a heat

exchanger (recuperator) through which the turbineexhaust gases pass.

y The compressed air is then heated in the exhaust gas heatexchanger, before the f low enters the combustor. If theregenerator is well designed (ifie., the heat exchangereffectiveness is high and the pressure drops are small) the

efficiency will be increased over the simple cycle value.y Regenerated gas turbines increase efficiency 5-6% and are

even more effective in improved part-load applications.


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INTERCOOLINGy It also involves the use of a heat exchanger. An intercooler

is a heat exchanger that cools compressor gas during thecompression process.

y For instance, if the compressor consists of a high and a lowpressure unit the intercooler could be mounted betweenthem to cool the flow and decrease the work necessary forcompression in the high pressure compressor.

y The cooling fluid could be atmospheric air or water (e.g.,sea water in the case of a marine gas turbine). It can beshown that the output of a gas turbine is increased with awell-designed intercooler.


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REHEATINGy It occurs in the turbine and is a way to increase turbine

work without changing compressor work or meltingthe materials from which the turbine is constructed.

y If a gas turbine has a high pressure and a low pressureturbine at the back end of the machine, a reheater(usually another combustor) can be used to "reheat"the flow between the two turbines.

y This can increase efficiency by 1-3%. Reheat in a jetengine is accomplished by adding an afterburner atthe turbine exhaust, thereby increasing thrust, at theexpense of a greatly increased fuel consumption rate.


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LATESTDEVELOPMENTy In a conventional turbojet and turbofan engine, fuel is burned in the

main combustor before the heated high pressure gas expands throughthe turbine.

y Aturbine-burner concept was proposed in paper presentation in which

combustion is continued inside the turbine to increase the efficiencyand specific thrust of the turbojet engine.

y This concept is extended to include not only continuous burning inthe turbine but also discrete inter stage turbine burners as anintermediate option. Athermodynamic cycle analysis is performed tocompare the relative performances of the conventional engine and theturbine-burner engine with different combustion options for bothturbojet and turbofan configurations.

y Turbine-burner engines are shown to provide significantly higherspecific thrust with no or only small increases in thrust specific fuelconsumption compared to conventional engines.


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ContinuousTurbine-Burner and

Inter-Turbine-Burner Enginesy Air from the far upstream (state a) comes into the inlet/diffuser and is

compressed to state 02 (the 0 here denotes stagnation state) before itsplits into the core engine and the fan bypass streams.

y The stream that goes into the core engine is further compressed by the

compressor, which usually consists of a low-pressure (LP) portion and ahigh-pressure (HP) portion on concentric spools, to state 03 beforegoing into the conventional main burner where heat Qb is added toincrease the flow temperature to T04.

y In a conventional configuration (dashed line in Figure) the HP, high-temperature gas expands through the turbine, which provides enoughpower to drive the compressor and fan and other engine auxiliaries. Tofurther increase the thrust level, fuel may be injected and burned inthe optional afterburner to increase further the temperature of the gasbefore the flow expands through the nozzle to produce the high-speed

jet. For a turbofan engine part of the flow that comes into the inlet isdiverted to the fan bypass. The pressure of the bypass flow is increasedthrough the fan. The flow state after the fan is marked as 03f.


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CONCLUSIONy Burning in the turbine passages reduces the tradeoff

between ST and TSFC. It allows significant increases in

ST with only small increases in TSFC.y The fundamental benefit of a CTB engine is to be able

to produce gases of high kinetic energy at highthermal efficiency, providing a very desirable gas

generator as the basis of high-performance enginesapplicable to both military and commercialapplications.


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yTHANK YOU

SEMINAR TURBINE ENGINES

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