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1、PARTTWO.GASTURBINEENGINESCHAPTER3PRINCIPLES,OPERATION,ANDCONSTRUCTIONAgasturbineengineisanair-dependent,thermaljetpropulsiondevicethatusesexhaust-gas-driventurbinewheelstodriveacompressor,makingcontinuousoperationoftheenginepossible.PRINCIPLESAlthought
2、hegasturbineenginediffersradicallyinconstructionfromtheconventionalfour-stroke,five-eventcyclereciprocatingengine,bothoperateonthesameprinciple.Inthepiston(reciprocating)engine,thefunctionsofintake,compression,combustion,andexhaustalltakeplaceinthesame
3、combustionchambertherefore,eachmustcompletelyoccupythechamberduringitsrespectivepartofthecombustioncycle.Inthegasturbineengine,aseparatesectionisdevotedtoeachfunction;allfunctionsareperformedatthesametimewithoutinterruption.Thesesectionsaretheair-inlet
4、sectionthecompressorsection,thecombustionsection,andaturbineandexhaustsection.Thecompressorbringsincompresses,andforcesairintothecombustionsection.Fuelistheninjectedintothecombustionarea,whereitmixeswiththecompressedair.Thefuelandairmixtureisignitedbya
5、nelectricalignitionplug;however,oncestarted,ignitionisshutoffandcombustioniscontinuousandself-supporting.IngasturbineenginesdesignedforArmyuse,nearlytwo-thirdsoftheenergyavailablefromtheproductsofcombustionisnecessarytodrivethecompressor.Thepowerturbin
6、eisdesignedtoextractasmuchoftheremainingenergyaspossiblefromthegasesandtransformitintoshafthorsepowerwhichisusedtodriveanoutputshaftorpropellerfromapowershaft.AbasicgasturbineengineisillustratedinFigure3-1.Acontainerofcompressedairhasbeenprovidedwithan
7、opening(nozzle)throughwhichtheairpassesoffintotheatmosphereuntilthepressureisexhausted(A).Thisbriefhigh-speedairflow(velocity)throughthenodeproducesamildmomentaryreactionforce(solidarrow).Thedensityoftheaircanbeincreasedbyheating(B).Theresultofthisincr
8、easedvolumeisagreatervelocityasindicatedbythelongarrow(heatedair)ascomparedtotheshortbrokenarrow.In(C)theheatedair(solidarrow)isdirected(impinged)ontotheairfoil-shapedbladesattachedtotherimofthedisc(turbine)causingtheturbinetorotateonit
