汽车专业英语课件-2cha

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,PrincipleofOperationClassificationsMainpartsandsystems,1.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.准确汉译表达也是难点,Chapter2InternalCombustionEngine2.1PrincipleofOperation,2.1.1NewWordsandPhrases,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Therstinternal-combustionenginetooperatesuccessfullyonthefour-strokecycleusedgasasafuelandwasbuiltin1876byNicolausAugustOtto,aself-taughtGermanengineerattheGas-motoreufabrikDeutzfactorynearCologne,formanyyearsthelargestmanufacturerofinternal-combustionenginesintheworld.ItwasoneofOttosassociatesGottliebDaimlerwholaterdevelopedanenginetorunonpetrolwhichwasdescribedinpatentnumber4315of1885.Healsopioneereditsapplicationtothemotorvehicle.Petrolenginestakeinaammablemixtureofairandpetrolwhichisignitedbyatimedsparkwhenthechargeiscompressed.Theseenginesarethereforesometimescalledspark-ignition(S.I.)engines.,2.1.2Text,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Theseenginesrequirefourpistonstrokestocompleteonecycle:anair-and-fuelintakestrokemovingoutwardfromthecylinderhead,aninwardmovementtowardsthecylinderheadcompressingthecharge,anoutwardpowerstroke,andaninwardexhauststroke.Inductionstroke.Theinletvalveisopenedandtheexhaustvalveisclosed.Thepistondescends,movingawayfromthecylinderhead(Fig.2-1(a).Thespeedofthepistonmovingalongthecylindercreatesapressurereductionordepressionwhichreachesamaximumofabout0.3barbelowatmosphericpressureatone-thirdfromthebeginningofthestroke.Thedepressionactuallygeneratedwilldependonthespeedandloadexperiencedbytheengine,butatypicalaveragevaluemightbe0.12barbelowatmosphericpressure.,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Thisdepressioninduces(sucksin)afreshchargeofairandatomisedpetrolinproportionsrangingfrom10to17partsofairtoonepartofpetrolbyweight.Anenginewhichinducesfreshchargebymeansofadepressioninthecylinderissaidtobenormallyaspiratedornaturallyaspirated.Compressionstroke.Boththeinletandtheexhaustvalvesareclosed.Thepistonbeginstoascendtowardsthecylinderhead(Fig.2-1(b).Theinducedair-and-petrolchargeisprogressivelycompressedtosomethingoftheorderofone-eighthtoone-tenthofthecylindersoriginalvolumeatthepistonsinnermostposition.Thiscompressionsqueezestheairandatomised-petrolmoleculesclosertogetherandnotonlyincreasesthechargepressureinthecylinderbutalsoraisesthetemperature.,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Typicalmaximumcylindercompressionpressureswillrangebetween8and14barswiththethrottleopenandtheenginerunningunderload.Powerstroke.Boththeinletandtheexhaustvalvesareclosedand,justbeforethepistonapproachesthetopofitsstrokeduringcompression,aspark-plugignitesthedensecombustiblecharge(Fig.2-1(c).Bythetimethepistonreachestheinnermostpointofitsstroke,thechargemixturebeginstoburn,generatesheat,andrapidlyraisesthepressureinthecylinderuntilthegasforcesexceedtheresistingload.Theburninggasesthenexpandandsochangethepistonsdirectionofmotionandpushittoitsoutermostposition.Thecylinderpressurethendropsfromapeakvalueofabout60barsunderfullloaddowntomaybe4barneartheoutermostmovementofthepiston.,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Exhauststroke.Attheendofthepowerstroketheinletvalveremainsclosedbuttheexhaustvalveisopened.Thepistonchangesitsdirectionofmotionandnowmovesfromtheoutermosttotheinnermostposition(Fig.2-1(d).Mostoftheburntgaseswillbeexpelledbytheexistingpressureenergyofthegas,butthereturningpistonwillpushthelastofthespentgasesoutofthecylinderthroughtheexhaust-valveportandtotheatmosphere.,Chapter2InternalCombustionEngine2.1PrincipleofOperation,Fig2-1Four-stroke-cyclepetrolengine,Chapter2InternalCombustionEngine2.2EngineClassifications,Fig2-1Four-stroke-cyclepetrolengine,Chapter2InternalCombustionEngine2.2EngineClassifications,2.2.1NewWordsandPhrases,Chapter2InternalCombustionEngine2.2EngineClassifications,Chapter2InternalCombustionEngine2.2EngineClassifications,Todaysautomotiveenginescanbeclassifiedinseveralwaysdependingonthefollowingdesignfeatures: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.,2.2.2Text,Fig.2-2Cylinderarrangements,Chapter2InternalCombustionEngine2.2EngineClassifications,Valvetraintype.Enginevalvetrainscanbeeithertheoverheadcamshaft(OHC)typeorthecamshaftin-blockoverheadvalve(OHV)type(Figure2-3).Someenginesseparatecamshaftsfortheintakeandexhaustvalves.ThesearebasedontheOHCdesignandarecalleddoubleoverheadcamshaft(DOHC)engines.V-typeDOHCengineshavefourcamshaftstwooneachside.,Figure2-3(a)Overheadcamshaft（OHC）,Chapter2InternalCombustionEngine2.2EngineClassifications,Valvetraintype.Enginevalvetrainscanbeeithertheoverheadcamshaft(OHC)typeorthecamshaftin-blockoverheadvalve(OHV)type(Figure2-3).Someenginesseparatecamshaftsfortheintakeandexhaustvalves.ThesearebasedontheOHCdesignandarecalleddoubleoverheadcamshaft(DOHC)engines.V-typeDOHCengineshavefourcamshaftstwooneachside.,Figure2-3(b)Overheadvalve(OHV)engines,Chapter2InternalCombustionEngine2.2EngineClassifications,Ignitiontype.Therearetwotypesofignitionsystems:sparkignitionandcompressionignition.Gasolineenginesuseasparkignitionsystemandaresortedtosparkignitionengines.Inasparkignitionengine,theair-fuelmixtureisignitedbyanelectricalspark.Dieselengines,orcompressionignitionengines,havenosparkplugs.Anautomotivedieselenginereliesontheheatgeneratedasairiscompressedtoignitetheair-fuelmixtureforthepowerstroke.Coolingsystems.Therearebothair-cooledandliquid-cooledenginesinuse.Nearlyalloftodaysengineshaveliquid-coolingsystems.Fueltype.Severaltypesoffuelcurrentlyusedinautomobileenginesincludegasoline,naturalgas,methanol,diesel,andpropane.Themostcommonlyusedisgasolinealthoughnewfuelsarebeingtested.,Chapter2InternalCombustionEngine2.2EngineClassifications,Chapter2InternalCombustionEngine2.3Engineblockandhead,2.3.1NewWordsandPhrases,Chapter2InternalCombustionEngine2.3Engineblockandhead,Chapter2InternalCombustionEngine2.3Engineblockandhead,2.3.1EngineblockTheengineblock(orcylinderblock)servesasarigidmetalfoundationforallpartsofanengine(Fig.2-4).Itcontainsthecylindersandsupportsthecrankshaftandcamshaft.Accessoryunitsandtheclutchhousingareboltedtoit.Blocksaremadeofeithercastironoraluminum.,2.3.2Text,Chapter2InternalCombustionEngine2.3Engineblockandhead,Thecylinderisaroundholeformedintheblock.Itformsaguideforthepistonandactsasacontainerfortakingin,compressing,firing,andexhaustingtheair-fuelcharge.Cylindershavebeenmadeofbothsteelandcastiron.Castironisbyfarthemostpopular.Whensteelcylindersar