汽车发动机外文翻译文献.docx

汽车发动机外文翻译文献.docx

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汽车发动机外文翻译文献

汽车发动机外文翻译文献

（文档含中英文对照即英文原文和中文翻译）

AUTOMOTIVEENGINE

1EngineClassificationandOverallMechanics

Theautomobileenginescanbeclassifiedaccordingto:

（1）cycles,

（2）coolingsystem,（3）fuelsystem,（4）ignitionmethod,（5）valvearrangement,（6）cylinderarrangement,（7）enginespeed.

Enginesusedinautomobilesaretheinternalcombustionheatengines.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcepistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thecrankshaftisthusmadetorotate:

therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandthecarmoves.

Theenginerequiresfourbasicsystemstorun（Fig.2-1）.Dieselenginesrequirethreeofthesesystems.Theyarefuelsystem,ignitionsystem（exceptdiesel）,lubricatingsystemandcoolingsystem.However,threeotherrelatedsystemsarealsonecessary.Thesearetheexhaustsystem,theemission-controlsystem,andthestartingsystem.Eachperformsabasicjobinmakingtheenginerun.

Fig.2-1Theengineconstruction

2 Engine OperatingPrinciples

Fig.2-2Engineterms

Theterm“stroke”isusedtodescribethemovementofthepistonwithinthecylinder.Themovementofthepistonfromitsuppermostposition（TDC,topdeadcenter）toitslowestposition（BDC,bottomdeadcenter）iscalledastroke.Theoperatingcyclemayrequireeithertwoorfourstrokestocomplete.Mostautomobileenginesoperateonthefourstrokecycle（Fig.2-2）.

Infour-strokeengine,fourstrokesofthepistoninthecylinderarerequiredtocompleteonefulloperatingcycle.Eachstrokeisnamedaftertheaction.Itperformsintake,compression,power,andexhaustinthatorder（Fig.2-3）.

IntakestrokeCompressionstrokePowerstrokeExhauststroke

Fig.2-3Four-stroke-cyclegasolineengine

1.Theintakestroke

Theintakestrokebeginswiththepistonnearthetopofitstravel.Asthepistonbeginsitsdescent,theexhaustvalveclosesfully,theintakevalveopensandthevolumeofthecombustionchamberbeginstoincrease,creatingavacuum.Asthepistondescends,anair/fuelmixtureisdrawnfromthecarburetorintothecylinderthroughtheintakemanifold.Theintakestrokeendswiththeintakevalveclosejustafterthepistonhasbegunitsupstroke.

2.Compressionstroke

AsthepistonismovedupbythecrankshaftfromBDC,theintakevalvecloses.Theair/fuelmixtureistrappedinthecylinderabovethepiston.Futurepistontravelcompressestheair/fuelmixturetoapproximatelyone-eighthofitsoriginalvolume（approximately8:

1compressionratio）whenthepistonhasreachedTDC.Thiscompletesthecompressionstroke.

3.Powerstroke

AsthepistonreachesTDConthecompressionstroke,anelectricsparkisproducedatthesparkplug.Theignitionsystemdeliversahigh-voltagesurgeofelectricitytothesparkplugtoproducethespark.Thesparkignites,orsetsfireto,theair/fuelmixture.Itnowbeginstoburnveryrapidly,andthecylinderpressureincreasestoasmuchas3-5MPaorevenmore.Thisterrificpushagainstthepistonforcesitdownward,andapowerfulimpulseistransmittedthroughtheconnectingrodtothecrankpinonthecrankshaft.Thecrankshaftisrotatedasthepistonispusheddownbythepressureaboveit.

4.Exhauststroke

Attheendofthepowerstrokethecamshaftopenstheexhaustvalve,andtheexhauststrokebegins.Remainingpressureinthecylinder,andupwardmovementofthepiston,forcetheexhaustgasesoutofthecylinder.Attheendoftheexhauststroke,theexhaustvalveclosesandtheintakevalveopens,repeatingtheentirecycleofeventsoverandoveragain.

3EngineBlockandCylinderHead

3.1EngineBlock

Theengineblockisthebasicframeoftheengine.Allotherenginepartseitherfitinsideitorfastentoit.Itholdsthecylinders,waterjacketsandoilgalleries（Fig.2-4）.Theengineblockalsoholdsthecrankshaft,whichfastenstothebottomoftheblock.Thecamshaftalsofitsintheblock,exceptonoverhead-camengines.Inmostcars,thisblockismadeofgrayiron,oranalloy（mixture）ofgrayironandothermetals,suchasnickelorchromium.Engineblocksarecastings.

Fig.2-4V6engineblock

Someengineblocks,especiallythoseinsmallercars,aremadeofcastaluminum.Thismetalismuchlighterthaniron.However,ironwearsbetterthanaluminum.Therefore,thecylindersinmostaluminumenginesarelinedwithironorsteelsleeves.Thesesleevesarecalledcylindersleeves.Someengineblocksaremadeentirelyofaluminum.

3.2CylinderSleeves

Cylindersleevesareusedinengineblockstoprovideahardwearingmaterialforpistonsandpistonrings.Theblockcanbemadeofonekindofironthatislightandeasytocastwhilethesleevesusesanotherthatisbetterabletost