汽车构造(发动机)中英文课件1-4

STRUCTUREOFAUTOMOBILEENGINE汽车发动机构造汽车运用教研组黄银娣开发Chapter1:TheInternalCombustionEngine§1-1General●Definition:TheInternalCombustionengineVSTheExternalCombustionEngine------Thecombustion(orburning)fueltakesplaceinsidetheengine.●Fuel:1.Mostautomobileengineproducepowerbyburningamixtureofairandgasoline;2.somekindsofenginebydieselfuel;3.somebyalternativefuelssuchasCNG（天然气）,LNG（液化石油气）,Methanol(甲醇）,ethanol(乙醇）andetc.汽车运用教研组黄银娣开发2003年8月Mainobjection:Tostudytheinternalcombustionengine汽车运用教研组黄银娣开发2003年8月§1-2Gasolineasafuelknowaboutfollowingpoints:●NO.1Howtheburningofgasolineproducesmechanicalpower?(1)Gasolineinliquidformisnoncombustible(non-burning)(2)however,gasolineVapordoesburn,combinedwithair(oxygeninair),gasolinevaporburnsinsidetheenginetoproducepower.汽车运用教研组黄银娣开发●NO.2Howdoestheliquidgasolineinthegastankbecomegasolinevapor?Evaporation:Gasolinebecomesavaporbyevaporation,whichistheprocessofturningaliquidintoavapor.Gasolinebeginstoevaporateatamuchlowertemperaturethanwater:Tevaporationofgasoline﹤Tevaporationofwateritmeans:Gasolineismoreeasytovaporizethanwater.汽车运用教研组黄银娣开发EvaporateEvaporationtakesplaceabovethesurfaceofaliquidwhenitisexposedtotheair.-----thus,gasolinevaporwillfillthespaceabovethesurfaceofgasoline.letshaveanexperiment:seeFig.1-1★Remember:thereisalwaysvaporabovethesurfaceofgasoline.Whiletheliquidmaynotburn,thevaporwill.汽车运用教研组黄银娣开发AtomizedparticlesAtomizer1-1:thevapormadebyasprayevaporatesquickly.汽车运用教研组黄银娣开发SprayingthegasolineintotheairThebestwaytoevaporategasolineistoexposetotheairasmuchofitssurfaceaspossible------tomakeliquidgasolineintothetinydroplets.e.gFig.1—2Thevapormadebyasprayevaporatesquickly.汽车运用教研组黄银娣开发fuseFuel-airmixturestopper1-2:Inthisexperiment,gasolinevaporburninginacanhasenoughpowertohavethestopperout.汽车运用教研组黄银娣开发2003年8月No.3Whathappenswhengasolineevaporates?Theevaporatinggasolinemixedwithair.Theevaporatinggasolineexpandstofillmorespacethanitdidasaliquid.Ifaflameistouchedtothismixture,thegasolinevaporandairburnrapidlyproducingintenseheat.Whenveryhot,themixturequicklyexpandsevenmore.汽车运用教研组黄银娣开发No.4Whathappenstothemixturewhenitisburnedinsideaclosedcontainer?Fig.1---3Suppose:①attheopenendofatincan------putacork(塞子）；②throughtheclosedend------ranafuse(引线，导火线）③closedspacefilledwithfuel-airmixtureinside汽车运用教研组黄银娣开发2003年8月SparkplugExhaustvalveIntakevalveCombustionchamberpistoncylinder1-3:Inthisengine.Atight-fittingpistonmovesupanddowninthecylinder.Theintakevalvetakesinvapor.Theexhaustvalvereleasestheburnedmixture.汽车运用教研组黄银娣开发2003年8月Makeanexperiment:First:sprayedinamixtureofvaporizedgasolineandairwithatomizer.Second:litthefuseThen:thefusewillignitethegasolinevapor.Thelast:theburningvaporwouldexpandwithsuchforcethatitwouldblowthestopperoff---that’s“explosion”★conclusion:Internalcombustionengineburnsgasolinevaporandairtoproducepower.汽车运用教研组黄银娣开发§1-3AOne-cylinderInternalCombustionengineThetincan------LikethecylinderofengineThestopperinthetincan------LikeapistonThefuseinthetincan------LikeasparkplugSpacebetweenthetopofthepistonandthetopofthecylinder.------Thecombustionchamber汽车运用教研组黄银娣开发Intakevalve------themixtureisletinandignitedExhaustvalve------exhaustgaswasreleasedfromthecylinderthroughtheexhaustvalveCrankshaft(曲轴）-----lookslikeastraightbarwithanoffset(n.偏置）sectioninthecenterofit(crankshaft)function:tochangepiston’supanddownmotiontotherotationofthecrankshaft●Aconnectingrod------joinsthepistonandthecrankshaftPistonConnectingrodcrankshaft1-4:thecrankshaftisstraight,withanoffsetsectioninthemiddleofit.Itisjoinedtothepistonmovesthecrankshaft.Thisconvertstheverticalmotionofthepistonintotherotarymotionofthecrankshaft.汽车运用教研组黄银娣开发§1-5Boreandstroke汽车运用教研组黄银娣开发2003年8月汽车运用教研组黄银娣开发2003年8月●bore(缸径)=D:thedistancefromonesideofthecylindertotheotherside=innerdiameterofthecylinder●Stroke(行程)：thedistancethepistontravelsfromitshighestpositioninthecylindertoitslowest.●Offset(偏置又叫曲轴半径)：theoffsetofthecrankshaftisequeltohalfthedistanceofthestroke.S=2rYoucanincreasethestrokebyincreasingthelengthofthecrankshaft’soffset.●TDC(上止点)：thepistonactuallystopsdeadatthetopiscalledTopdeadcenter(TDC).●BDC(下止点)：thebottomofthepistontraveliscalledbottomdeadcenter(BDC)汽车运用教研组黄银娣开发2003年8月§1-6pistonstrokesIntakestroke(进气行程)Compressionstroke(压缩行程)Powerstroke(做功行程)Exhauststroke(排气行程)汽车运用教研组黄银娣开发第二节四冲程发动机工作原理四冲程柴油机工作过程汽车运用教研组黄银娣开发2003年8月汽车运用教研组黄银娣开发2003年8月1.intakestrokesPistonstartsdownwardformTDCtoBDCTheintakevalveopenstotakeintheairandfuelmixture.2.CompressionstrokeThepistonstartsbackupthecylinderagainfromBDCtoTDC.Boththeintakeandexhaustvalvesareclosed.Thevaporizedmixtureiscontainedbythecylinder,itbecomescompressed(squeezed)intoaverysmallspace.Onefullrevolution:Withtheintakeandcompressionstrokes,thepistonhasgonefromTDCtoBDCandbackuptoTDCagain,thecrankshafthascompletedonefullrevolution.SparkNeartheTDCofthecompressionstroke,thesparkplugmakesasparkthatignitesthemixturewhichburnsrapidly.Asmixtureburns,itexpands,placinggreatpressureonthepiston.汽车运用教研组黄银娣开发2003年8月3..powerstrokePistondownwardagainonthethirdstr