汽车专业英语ppt全套配套课件优化word教案参考译文2 Chapter 2.1-2.3

复习1.Discribethemainpartsofacar?说明汽车的主要组成部件（系统）有哪些？2.Vehicleclassificatin汽车分类提问学习内容本次课学习内容、目标和重点难点学习目标难点重点 PrincipleofOperation Classifications Mainpartsandsystems1.掌握内燃机的分类英文术语2.掌握机体、曲柄连杆机构、配气机构的英文术语2.了解各个系统的主要功能1.重点为记忆分类和主要部件英文专业术语2.难点需要记忆的生词偏多3.准确汉译达也是难点Chapter2InternalCombustionEngine2.1PrincipleofOperation2.1.1NewWordsandPhrasesChapter2InternalCombustionEngine2.1PrincipleofOperationChapter2InternalCombustionEngine2.1PrincipleofOperationChapter2InternalCombustionEngine2.1PrincipleofOperationChapter2InternalCombustionEngine2.1PrincipleofOperationChapter2InternalCombustionEngine2.1PrincipleofOperationChapter2InternalCombustionEngine2.1PrincipleofOperationThefirstinternal-combustionenginetooperatesuccessfullyonthefour-strokecycleusedgasasafuelandwasbuiltin1876byNicolausAugustOtto,aself-taughtGermanengineerattheGas-motoreufabrikDeutzfactorynearCologne,formanyyearsthelargestmanufacturerofinternal-combustionenginesintheworld.ItwasoneofOtto’sassociates–GottliebDaimler–wholaterdevelopedanenginetorunonpetrolwhichwasdescribedinpatentnumber4315of1885.Healsopioneereditsapplicationtothemotorvehicle.Petrolenginestakeinaflammablemixtureofairandpetrolwhichisignitedbyatimedsparkwhenthechargeiscompressed.Theseenginesarethereforesometimescalledspark-ignition(S.I.)engines.2.1.2TextChapter2InternalCombustionEngine2.1PrincipleofOperationTheseenginesrequirefourpistonstrokestocompleteonecycle:anair-and-fuelintakestrokemovingoutwardfromthecylinderhead,aninwardmovementtowardsthecylinderheadcompressingthecharge,anoutwardpowerstroke,andaninwardexhauststroke.Inductionstroke.Theinletvalveisopenedandtheexhaustvalveisclosed.Thepistondescends,movingawayfromthecylinderhead(Fig.2-1(a)).Thespeedofthepistonmovingalongthecylindercreatesapressurereductionordepressionwhichreachesamaximumofabout0.3barbelowatmosphericpressureatone-thirdfromthebeginningofthestroke.Thedepressionactuallygeneratedwilldependonthespeedandloadexperiencedbytheengine,butatypicalaveragevaluemightbe0.12barbelowatmosphericpressure.Chapter2InternalCombustionEngine2.1PrincipleofOperationThisdepressioninduces(sucksin)afreshchargeofairandatomisedpetrolinproportionsrangingfrom10to17partsofairtoonepartofpetrolbyweight.Anenginewhichinducesfreshchargebymeansofadepressioninthecylinderissaidtobe‘normallyaspirated’or‘naturallyaspirated’.Compressionstroke.Boththeinletandtheexhaustvalvesareclosed.Thepistonbeginstoascendtowardsthecylinderhead(Fig.2-1(b)).Theinducedair-and-petrolchargeisprogressivelycompressedtosomethingoftheorderofone-eighthtoone-tenthofthecylinder’soriginalvolumeatthepiston’sinnermostposition.Thiscompressionsqueezestheairandatomised-petrolmoleculesclosertogetherandnotonlyincreasesthechargepressureinthecylinderbutalsoraisesthetemperature.Chapter2InternalCombustionEngine2.1PrincipleofOperationTypicalmaximumcylindercompressionpressureswillrangebetween8and14barswiththethrottleopenandtheenginerunningunderload.Powerstroke.Boththeinletandtheexhaustvalvesareclosedand,justbeforethepistonapproachesthetopofitsstrokeduringcompression,aspark-plugignitesthedensecombustiblecharge(Fig.2-1(c)).Bythetimethepistonreachestheinnermostpointofitsstroke,thechargemixturebeginstoburn,generatesheat,andrapidlyraisesthepressureinthecylinderuntilthegasforcesexceedtheresistingload.Theburninggasesthenexpandandsochangethepiston’sdirectionofmotionandpushittoitsoutermostposition.Thecylinderpressurethendropsfromapeakvalueofabout60barsunderfullloaddowntomaybe4barneartheoutermostmovementofthepiston.Chapter2InternalCombustionEngine2.1PrincipleofOperationExhauststroke.Attheendofthepowerstroketheinletvalveremainsclosedbuttheexhaustvalveisopened.Thepistonchangesitsdirectionofmotionandnowmovesfromtheoutermosttotheinnermostposition(Fig.2-1(d)).Mostoftheburntgaseswillbeexpelledbytheexistingpressureenergyofthegas,butthereturningpistonwillpushthelastofthespentgasesoutofthecylinderthroughtheexhaust-valveportandtotheatmosphere.Chapter2InternalCombustionEngine2.1PrincipleofOperationFig2-1Four-stroke-cyclepetrolengineChapter2InternalCombustionEngine2.2EngineClassificationsFig2-1Four-stroke-cyclepetrolengineChapter2InternalCombustionEngine2.2EngineClassifications2.2.1NewWordsandPhrasesChapter2InternalCombustionEngine2.2EngineClassificationsChapter2InternalCombustionEngine2.2EngineClassificationsToday’sautomotiveenginescanbeclassifiedinseveralwaysdependingonthefollowingdesignfeatures:·Operationalcycles.Therearetwo-strokeandfour-strokecycles.Four-stroke-cycleenginesarewidelyusedonroadvehicles.However,afewoldercarshaveusedandsomecarsinthefuturewilluseatwo-strokeengine.·Numberofcylinders.Currentenginedesignsinclude3-,4-,5-,6-,8-,10-,and12-cylinderengines.·Cylinderarrangement.Anenginecanbeflat(horizontal-opposed),inline,orV-type.Othermorecomplicateddesignshavealsobeenused.Seefigure2-2.2.2.2TextChapter2InternalCombustionEngine2.2EngineClassificationsFig.2-2CylinderarrangementsChapter2InternalCombustionEngine2.2EngineClassifications·Valvetraintype.Enginevalvetrainscanbeeithertheoverheadcamshaft(OHC)typeorthecamshaftin-blockoverheadvalve(OHV)type(Figure2-3).Someenginesseparatecamshaftsfortheintakeandexhaustvalves.ThesearebasedontheOHCdesignandarecalleddoubleoverheadcamshaft(DOHC)engines.V-typeDOHCengineshavefourcamshafts—twooneachside.Figure2-3(a)Overheadcamshaft（OHC）Chapter2InternalCombustionEngine2.2EngineClassifications·Valvetraintype.Enginevalvetrainscanbeeithertheoverheadcamshaft(OHC)typeorthecamshaftin-blockoverheadvalve(OHV)type(Figure2-3).Someenginesseparatecamshaftsfortheintakeandexhaustvalves.ThesearebasedontheOHCdesignandarecalleddoubleoverheadcamshaft(DOHC)engines.V-typeDOHCengineshavefourcamshafts—twooneachside.Figure2-3(b)Overheadvalve(OHV)enginesChapter2InternalCombustionEngine2.2EngineClassifications·Ignitiontype.Therearetwotypesofignitionsystems:sparkignitionandcompressionignition.Gasolineenginesuseasparkignitionsystemandaresortedtosparkignitionengines.Inasparkignitionengine,theair-fuelmixtureisignitedbyanelectricalspark.Dieselengines,orcompressionignitionengines,havenosparkplugs.Anautomotivedieselenginereliesontheheatgeneratedasairiscompressedtoignitetheair-fuelmixtureforthepowerstroke.·Coolingsystems.Therearebothair-cooledandliquid-cooledenginesinuse.Nearlyalloftoday’sengineshaveliquid-coolingsystems.·Fueltype.Severaltypesoffuelcurrentlyusedinautomobileenginesincludegasoline,naturalgas,methanol,diesel,andpropane.Themostcommonlyusedisgasolinealthoughnewfuelsarebeingtested.Chapter2InternalCombustionEngine2.3Engineblockandhead2.3.1NewWordsandPhrasesChapter2InternalCombustionEngine2.3EngineblockandheadChapter2InternalCombustionEngine2.3Engineblockandhead2.3.1EngineblockTheengineblock(orcylinderblock)servesasarigidmetalfoundationforallpartsofanengine(Fig.2-4).Itcontainsthecylindersandsupportsthecrankshaftandcamshaft.Accessoryunitsandtheclutchhousingareboltedtoit.Blocksaremadeofeithercastironoraluminum.2.3.2TextChapter2InternalCombustionEngine2.3EngineblockandheadThecylinderisaroundholeformedintheblock.Itformsaguideforthepistonandactsasacontainerfortakingin,compressing,firing,andexhaustingtheair-fuelcharge.Cylindershavebeenmadeofbothsteelandcastiron.Castironisbyfarthemostpopular.Whensteelcylindersaredesiredinanaluminumblock,theyareinstalledintheformofcylindersleeves(round,pipe-likeliners).Thesesleevesmaybeeithercastorpressedintotheblock.Someenginesuseremovablecylindersleeves.Whenthecylinderbecomesworn,theoldsleevescanbepulledoutandnewsleevescanbepressedin.Chapter2InternalCombustionEngine2.3Engineblockandhead2.3.2CylinderheadThecylinderheadfastenstothetopoftheblock(Fig.2-4).Theundersideformsthecombustionchamberwiththetopofthepiston.In-lineenginesoflightvehicleshavejustonecylinderheadforallcylinders;largerin-lineenginescanhavetwoormore.Justaswithengineblocks,cylinderheadscanbemadeofcastironoraluminumalloy.Chapter2InternalCombustionEngine2.3EngineblockandheadFig.2-4Cylinderblock,cylinderheadandcamshaft小结与作业 Mainengineparts,classification 阅读并记住黑体字专业词汇；提出疑难问题 掌握发动机工作原理、主要组成和分类术语