汽车专业英语课件：Engine Structure -

汽车专业英语EngineStructure2.1Structuraldrawingandterminology1.intakeairtank(进气管)2.throttlevalve(节流阀)3.cylinderhead(气缸盖)4.cylinder(气缸)5.cylinderblock(气缸体)6.flywheel(飞轮)7.cylinderjacket(气缸套)8.piston(活塞)9.oilpan(油底壳)10.crankshaft(曲轴)11.timingbeltpulley(同步皮带轮)12.crankshaftpulley(曲轴皮带轮)13.timingbelt(正时皮带)14.camshaft(凸轮轴)15.timingbeltcover(正时皮带护罩)16.sparkplug(火花塞)Fig.2-1Theoverallstructureofanengine1.switch(开关)2.heatermachine(暖风机)3.heatermachinepenstoke(暖风机进水管)

4.thermostat(节温器)5.waterpump(水泵)6.waterpipe(水管)7.waterswell(水箱)8.waterlid(加水盖)9.bulgewaterswell(膨胀水箱)10.pressurelimitingvalve(限压阀)Fig.2-2CoolingSystem1.camshaft(凸轮轴)2.overpressvalve(过压阀)3.hydraulicswitch(油压开关)4.filters(滤清器)5.oilsumptank(油底壳)6.oilpump(机油泵)7.overpressvalve(过压阀)8.backclosingvalve(回油关闭阀)Fig.2-3LubricationSystem2.2ClassificationofEngineThereareavarietyofengines,andmostofthemusethepetroleumfuelandareknownasgasolineengines.Thevaporizedliquidfuelismixedupwiththeair,burntandexpandedtoproducethepowertodrivethecars.Thiskindofengineiscalledtheinternalcombustionengine.Nowadays,carsaremostlyequippedwiththegasolineengines.Theautomobileenginescanbeclassifiedaccordingto:numberofcylinders;arrangementofcylinders;arrangementofvalves;typeofcooling;numberofcycles;typeoffuelburned;typeofignition.有各种各样的发动机，其中大部分使用石油燃料，被称为汽油发动机。气化的液体燃料与空气混合，燃烧和膨胀产生动力驱动汽车。这种发动机是内燃发动机。如今，汽车主要配备汽油发动机。1.2.1Engine1.ClassifiedbytheNumberofCylindersAccordingtothenumberofcylinders,theautomobileenginescanbeclassifiedsinglecylinderengineandmulticylinderengine.2.ClassifiedbytheArrangementofCylindersThetermengineconfigurationreferstothewaythatthecylindersofanenginearearranged.Thecylinderscanbein-line,opposed,oratanangle(V-type).Withinthreebasicarrangements,thereareanumberofvariations.发动机布置形式是指发动机气缸的布置方式，可分为直列式、对置式、V型发动机，在三种基本的排列类型中，也有一些变动。inlineengine.Somein-lineengineshavetheircylinderhorizontal,sothattheengineismoreorlessonitsside.Thisreducestheoverallheightunderthecab.Themechanicalarrangementoffour-cylinderin-lineiscommonlyusedforpassengercars.直列式发动机。有一些直列发动机的气缸是卧式的，因此发动机或多或少地处于一侧，这样会减少驾驶室下部的发动机的总体高度。四缸直列发动机布置形式常见于小汽车中。Horizontal-OpposedEngine.Thisarrangementhasitscylindersarrangedintwoflatsideswiththecrankshaftbetweenthem.Theengineshownhasashortrigidcrankshaftwithfivebearings.Ahorizontal-opposedenginehasevenfiringimpulsesandgoodbalance.Movementofapistoninonedirectionisopposedbymovementofapistonintheopposeddirection.Horizontal-opposedengines,withtheirflatdesign,givetheenginealowheightandalsohelptokeepthecenterofgravityofthevehiclelow.Alowcenterofgravitygivesthevehiclestability.水平对置式发动机。这种布置是使气缸布置于曲轴的两侧。所示发动机具有含5个轴承的刚性短曲轴。水平对置式发动机具有均匀的触发脉冲和良好的平衡。某一方向上活塞的运行与其对置方向的活塞的运行是相反的。由于其扁平的设计，水平对置式发动机的高度不高，这样也使得车辆的中心保持较低，使车辆稳定性较好。V-TypeEngine.

WithV-typeengines,thecylindersarearrangedintwoblanksatanangle.Thisreducesthelengthoftheengineandmakesitmorecompact.Thisalsoreducesthelengthofthecrankshaft,whichcanbedesignedtobemorerigidthanalongshaft.V型发动机。发动机的布置成一定角度，这样能够缩小发动机的长度，使其更加紧凑，同样也会缩小曲轴的长度，这样使得曲轴的设计更加注重刚度而非是长轴。3.ClassifiedbytheArrangementofValvesAccordingtothearrangementofvalves,theautomobileenginescanbeclassifiedintofour-cylinderengine,five-cylinderengine,six-cylinderandsoon.4.ClassifiedbytheNumberofCyclesAccordingtothenumberofcycles,theautomobileenginescanbeclassifiedintotwo-strokecycleengineandfour-strokecycleengine.SeeFig.2-5.a.Two-strokecycleengineb.Four-strokecycleengineFig.2-5Classifiedbythenumberofcycles5.ClassifiedbytheTypeofCoolingAccordingtothetypeofcooling,theautomobileenginescanbeclassifiedintowater-cooledorliquid-cooledengineandair-cooledengine.6.ClassifiedbytheTypeofFuelBurnedAccordingtothetypeoffuelburned,theautomobileenginescanbeclassifiedintogasolineengineanddieselengine.SeeFig.2-6.

Fig.2-6ClassifiedbythetypeofthefuelburnedTheengineisthesourceofpowerthatmakesthewheelsrotateandthecarmove.Theautomobileengineisaninternalcombustionenginebecausethefuel(gasoline)isburnedinsideit.Theburningofgasolineinsidetheengineproduceshighpressureintheenginecombustionchamber.Thishighpressureforcespistontomove,themovementiscarriedbyconnectingrodstotheenginecrankshaft.Thus,thecrankshaftismadetorotate,therotarymotioniscarriedthroughthepowertraintothecarwheelssothattheyrotateandcarmoves.Theenginerequiresfivesystems.Theyarefuelsystem,coolingsystem,lubricationsystem,ignitionsystemandstartingsystem.Thesefivesystemsarediscussedbrieflyinthefollowingunits.Theoverallstructureofanengineisasfollows.SeeFig.2-7.Thecompleteengineassemblyofthemechanicalcomponentsthatmakesuptheengineitselfandalsoanumberofassociatedsystems,thesearethesystemsthatareneededtostarttheengineandalsotocontrolitandkeepitrunning.Themechanicalpartsoftheengineassemblycanbebrokendownintoanumberofsub-assemblies,orgroupofassociatedcomponents,althoughtheseareusuallyreferredtomerelyasassemblies,forexample,cylinder-headassemblyandpistonassembly.Somepartsofanengineareinternal,otherpartsareexternal-thisillustrationidentifiesanumberofexternalparts.2.3ConstructionofEngine

发动机运转需要五个系统，分别是燃油系统，冷却系统，润滑系统，点火系统和起动系统。1.CylinderBlock

Theengineblockisthemainsupportingstructuretowhichallotherenginepartsareattached.Ithastwomainsections:thecylindersectionandthecrankcasesection.Thecrankcasesectionisusedtohousethecrankshaft,oilpan.Coolingpassagewaysarebuiltwithintheblock.Thesepassageways,alsoknownaswatersockets,surroundthecylinders.Theyallowcoolanttocirculatethroughoutthecylinderareatokeeptheenginecool.Thereisalsoadrilledpassagewaywithinsomeblocksforthecamshaft.Manyoilholesaredrilledinternallysothatenginepartscanbeadequatelylubricated.SeeFig.2-7.1.cylinder(气缸)2.waterjacket(水套)3.mainoilgallery(主油道)4.blockunderside(机体底面)5.reinforcingrib(横隔板加强肋)6.headstock(柱轴承座)7.blocksidewall(机体侧壁)8.sidewallreinforcerib(侧壁加强肋)9.blocktipsurface(机体顶面)Fig.2-7Cylinderblock

机体组是发动机的支架，是其它发动机零部件的装配基体，有两个主要的部分：气缸体和曲轴箱。曲轴箱用于装配曲轴和油底壳，冷却水道被铸在气缸体周围，也叫做水套，这些水套能够使冷却液在气缸周围不断循环以使发动机冷却下来。2.CylinderHeadThecylinderheadisusedtoholdthevalves,andithasportstoallowair,fuelandexhausttomovethroughtheengine.Inaddition,ithascoolantpassages.Fig.2-8showsacylinderhead.Afterthecylinderheadhasbeencast,someareasmustbeseated,sparkplugsandinjectorscanbeinstalled,andinjectorscanbeinstalled,andagoodsealcanbeprovidedtotheblock.1.cylinderheadcover(气缸盖罩)2.gasket(密封垫)3.cylinderhead(缸盖)4.cylinderheadgasket(气缸盖垫圈)Fig.2-8Cylinderhead3.PistonandConnectingRodAssemblyThepistonandconnectingrodassemblytransmitsthepowerfromcombustiontothecrankshaft.ItsshowninFig.2-9,mainlyconsistsofpiston,compressionrings,oilcontrolrings,pistonpinandconnectingrod.1.piston(活塞)2.pistonrings(活塞环)3.pistonpin(活塞销)4.connectingrod(连杆)5.connectingrodbolts(连杆螺栓)6.connectingrodcap(连杆盖)7.connectingrodbearing(连杆轴承)Fig.2-9PistonandrodassemblyPiston.Pistonfitscloselywithintheenginecylinderorlinerandisabletomovealternatelyupanddowninthecylinder.PistonRings.Thesearetwotypesofpistonrings-compressionandoilcontrolrings.Thecompressionringsareusedtosealthepressuresofcompressionandpower.Theoilcontrolringsareemployedtoscrapeoilfromthecylinderwalls.PistonPin.Itisusedtoconnectpistontoconnectingrod.ConnectingRod.Itisusedtoconnectpistontocrankshaft,anditchangesthereciprocatingmotiontotherotarymotion.4.CrankshaftAssemblyItisboltedtothebottomofthecylinderblock.Thecrankshaftisaone-piececastingorforgingofheart-treatedalloysteelofconsiderablemechanicalstrength.Itmustbestrongenoughtotakethedownwardthrustsofthepistonsduringthepowerstrokeswithoutexcessivedistortion.Inaddition,itmustbecarefullybalancedtoeliminateunduevibrationresultingfromtheweightoftheoffsetcranks.Toprovidebalance,crankshaftshavecounterweightsoppositethecranks.Crankshaftshavedrilledoilpassagesthroughwhichoilcanflowfromthemaintotheconnecting-rod,bearings.Thecrankshaftassemblyincludesthecrankshaft,bearings,flywheel,harmonicbalancer,timinggear,frontandrearseals.Fig.2-10showscrankshaftassembly.1.crankshaftfrontend(曲轴前端)2.frontmainjournal(前轴轴颈)3.oilpassagehole(油道孔)4.crankpin(曲柄销)5.crankweb(曲柄臂)6.counterweight(平衡锤)7.oilpassageplug(润滑油孔塞)8.oilpassage(润滑油孔)9.crankshaftcollar(曲轴后端凸缘)10.flywheel(飞轮)11.flywheelgearring(飞轮齿环)12.flywheellockplate(飞轮锁板)13.clutchshaftbearing(离合器轴轴承)Fig.2-10Crankshaftassembly5.CamshaftAssembly

Thecamshaftisdrivenbythecrankshaftandusedtoopenandclosethevalves.Mostpistonsaremadefromcastaluminum.Thepiston,throughtheconnectingrod,transferstothecrankshafttheforcecreatedbytheburningfuelmixture.Thisforceturnsthecrankshaft.Thecamshaftassemblyincludesthecamshaft,camshafttiminggear,camshaftbearing,timingchain,andbelt(ifused).SeeFig.2-11.1.camshaftjournal(凸轮轴)2.cam(凸轮)3.oilhole(油孔)4.timinggear(定时齿轮)Fig.2-11Camshaft

凸轮轴是由曲轴驱动，用于开启和关闭气门。大多数活塞由铸铝制成。通过连杆、活塞将燃油混合气燃烧产生的动力传递给曲轴，使曲轴转动起来。凸轮轴总成包括凸轮轴、凸轮轴定时齿轮、凸轮轴轴承、正时链条和皮带（如果使用的话）。6.FlywheelTheflowofpowerfromtheenginecylinderisnotsmooth.Althoughthepowerimpulseoverlap(onsixandeight-cylinderengines),thesearetimeswhenmorepowerisbeingdeliveredthanatothertimes.Thistendstomakethecrankshaftspeedupandthenslowdown.However,theflywheelcombatsthetendency.Theflywheelisacomparativelyheavywheelboltedtotherearendofthecrankshaft.Theinertiaoftheflywheeltendstokeepitturningatconstantspeed.Thus,theflywheelabsorbsenergyasthecrankshafttriestospeedupandgivebackenergyasthecrankshafttriestoslowdown.Ineffect,theflywheelabsorbspowerfromtheengineduringthepowerstroke(orspeeduptime)andthengivesittotheengineduringtheotherthreestrokesofthecycle.2.4EngineOperatingPrinciplesTheactionstakingplaceintheenginecylindercanbedividedintofourstages,orstrokes.“Stroke”referstopistonmovement;astrokeoccurswhenthepistonmovesfromonelimitingpositiontotheother.TheupperlimitofpistonmovementiscalledTDC(topdeadcenter).ThelowerlimitofpistonmovementiscalledBDC(bottomdeadcenter).AstrokeispistonmovementfromTDCtoBDCorformBDCtoTDC,inotherwords,thepistoncompletesastrokeeachtime,itchangesitsdirectionofmotion.1.IntakeStrokeThefirststrokeistheintakestroke.Asthepistonstartsdown,theintakevalveopensandtheair-fuelmixtureentersintothecylinder.Whenthepistonreachesthebottomoftheintakestroke,theintakevalvecloses,trappingtheair-fuelmixtureinthecylinder.Duringthisstoke,theexhaustvalvestaysclosed.

第一个冲程是进气冲程。当活塞开始下降，进气阀打开，可燃混合气进入气缸。当活塞到达进气冲程底部，进气阀关闭，封闭可燃混合气在气缸中。在这整个过程中，排气门都保持关闭。2.CompressionStrokeThesecondstrokeisthecompressionstroke.Thepistonmovesupinthecylinderwithbothvalvesclosedandcompressesthetrappedair-fuelmixture.Whenthepistonreachesthetopofthecylinder,thepressurerises.

第二个冲程是压缩冲程。活塞在气缸内上升，进排气门均关闭，对被困在气缸内的可燃混合气进行压缩。当活塞到达气缸顶部，气缸内压力上升。3.PowerstrokeThethirdstrokeisthepowerstroke.Neartheendofthecompressionstroke,thesparkplugfires,ignitingthecompressedair-fuelmixturethatproducesapowerfulexplosion.Thecombustionprocesspushesthepistondownthecylinderwithgreatforceturningthecrankshafttoprovidethepowertodrivethecar.第三个冲程是做功冲程。接近压缩冲程结束时，火花塞跳火，点燃压缩的可燃混合气，产生强大的爆炸。燃烧过程推动活塞沿着缸体向下运动，产生巨大的力使得曲轴转动，进而为汽车行进提供动力。4.ExhaustStrokeThefourthstrokeistheexhauststroke.Withthepistonatthebottomofthecylinder,theexhaustvalveopen,andthepistonmovesupagainandforcestheburnedgasesoutofthecylinder.Thepistontravelsuptothetopofthecylinderpushingalltheexhaustoutbeforeclosingtheexhaustvalveinpreparationforstartingthefour-strokeprocessoveragain.第四冲程是排气冲程。随着活塞到达气缸底部，排气门打开，活塞再次向上移动，迫使燃烧后的废气排出气缸。在排气门关闭之前，活塞再继续向上运动到达气缸顶部，并排出所有废气，并开始为再一次的四冲程循环做准备。2.4EngineOperatingPrinciples2.5EngineStartingSystem

Thestartingsystemistheheartoftheelectricalsysteminyourcar.Thestartingsystemperformsthisfunctionbychangingelectricalenergyfromthebatterytomechanicalenergyinthestartingmotor.Thismotorthentransfersthemechanicalenergy,throughgears,totheflywheelontheengine’scrankshaft.Duringcranking,theflywheelrotatesandtheair-fuelmixtureisdrawnintothecylinders,compressed,andignitedtostarttheengine.Mostenginesrequireacrankingspeedofabout200r/min.Thestartingsystemincludesthefollowingcomponents:battery,cableandwires,ignitionswitch,startersolenoidorrelay,startermotor,starterdriveandflywheelringgear.Fig.2-12showsthecomponentsinasimplifiedcrankingsystemcircuit.1.battery(蓄电池)2.startingcircuit(起动电路)3.magneticswitch(电磁开关)4.startermotor(起动电动机)5.controlcircuit(控制电路)6.startingsafetyswitch(起动安全开关)7.ignitionswitch(点火开关)Fig.2-12Startingsystem

起动系统是汽车电器系统的核心。起动系统能够实现将蓄电池的电能转变成起动机的机械能，起动机再通过齿轮将机械能传递到发动机曲轴的飞轮上。在起动过程中，飞轮旋转，空气混合气被吸入气缸，进行压缩，最后点燃，将发动机起动。多数发动机要求其起动速度为200转/分。起动系统包括以下部分：蓄电池、电缆和电线、点火开关、起动机电磁开关或继电器、起动机、起动机传动机构、飞轮环齿。图2-12描述了一个简化的起动系统电路的各部分组成。Thefunctionofthestartingsystemistocrankingtheenginefastenoughtoallowtheenginetostart.Thestartingsystemandignitionsystemmustworktogetherforgoodenginestarting.

起动系统的作用以足够快的速度起动发动机以使发动机自动的进入怠速运转状态，起动系统必须要和点火系统一起工作才能保证良好的发动机起动。Theautomotivebatteryservesasanenergy“bank”.Itreceivesfromthevehicl’schargingsystemandstoresituntilneeded.Thenitprovidestheenergytomostelectricalsystemsondemand.Thebatteryconvertsitbackintoelectricityduringdischarging.

汽车蓄电池作为能源的“银行”，它从汽车的充电系统在需要的时候吸收并存储能源，然后为绝大多数有需要的电器系统提供能源。在放电的过程中，电池将这些能源转变成电能。Thekeyswitch,orignitionswitch,controlstheignitioncircuit.Italsocontrolsthestartingsystemandthepowerfortheinstrumentsandvehicleaccessories.Thestartermotor,orstarter,isacompactbutverypowerfuldirect-currentelectricmotordesignedtocranktheenginefastenoughforittostart.Itrotatesasmallgearcalledapinion.Astarterdriveassemblyconnectsthesmallpiniongeartotheendofthestartermotor.Thepiniongearmesheswiththeringgearontheengine’sflywheel.Whenthedriverturnsthekeyswitch,thestartermotordrivesthepiniongear,whichdrivestheflywheelandcrankstheengine.Instartingmotor,fieldcoilsinastartingmotorareusedtoproducethepoles.Armatureinastartingmotorisarotationalpartthathasmanyloopsofwirewithacommutator.Brushesareusedtomakeelectricalcontactbetweentherotatingarmatureandthestationarybattery.Fig.2-13isthestructureofthestarter.1.over-runningclutch(超速离合器)2.shiftlever(拨叉)3.solenoid(电磁线圈)4.brushhold(夹持刷)5.commutator(换向器)6.motorarmature(电动机电枢)7.fieldcoil(激磁线圈)8.flywheel(飞轮)9.piniongear(行星齿轮)Fig.2-13ThestructureofthestarterThepurposeofthestarterclutchistoengageanddisengagethepiniongearfromtheflywheel.Whenthestarteriscranked,thepiniongearslidesonthearmatureshaftandengagestheflywheel.Toavoiddamagingthearmatureandthecommutator,thestarterdriveassemblyisdesignedtodisengagethepiniongearfromtheringgearassoonastheenginebeginstooperate.

Thesolenoidisamagneticswitchmountedontopofthestartermotor.Ithastwoimportantfunctions:itcontrolstheelectricalcircuitbetweenthebatteryandstartermotor,itshiftsthepiniongearinandoutofmeshwiththeringgear.电磁开关安装在起动机顶部，它有两个重要的作用：控制蓄电池和起动机之间的电路和实现行星齿轮与环形齿轮之间的啮合。2.6EFISystemElectronicfuelinjection(EFI)systemcollectsinformationthroughvarioussensors,andthecomputercontrolstheoperationoffuelinjectorsbasedontheinformation.Electronicfuelinjectionworksonsomeverybasicprinciples.Itcanbedividedintothreebasicsub-systems:thefueldeliverysystem,airinductionsystemandelectroniccontrolsystem.Toensuretheengineworksregularly,enoughfuelandairareneeded.Thefunctionofthefuelsupplysystemistosupplyequipment:thecarburetorandtheelectricalcontrolled.Forthesakeofthedevelopmentoftechnologyandtherequirementoftheenvironmentalprotection,theelectricalcontrolledisusedwidelywhilethecarburetorisalreadyobsolete.1.throttle(节流阀)2.idleaircontrolvalve(怠速空气控制阀)3.intakepipe(进气管)4.injector(喷油器)5.intakemanifold(进气歧管)6.airflowmeter(空气流量计)7.resonator(谐振器)8.aircleaner(空气滤清器)9.intakeflowpipe(进气管)10.throttlepositionsensor(节气门位置传感器)Fig.2-14Thestructureoftheintakeairsystem电子燃油喷射(电喷)系统通过各种传感器收集信息，根据这些信息计算机控制喷油器喷射。电子燃油喷射的基本原理很相似，可以分为三个基本子系统：燃油供给系统，进气系统和电子控制系统。Airisfilteredthroughtheaircleanerandtheamountflowingtotheairintakechamberisdeterminedaccordingtothethrottlevalveopeninginthethrottlebodyandtheenginespeed.Intakeaircontrolledbythethrottlevalveopeningisdistributedfromtheairintakechambertothemanifoldofeachcylinderandisdrawnintothecombustionchamber.Atlowtemperature,theIdleAirControl(IAC)valveopensandtheairflowsthroughtheIACvalveandthethrottlebody,intotheairintakechamber,therebyincreasingtheidlespeed(firstidleoperation).Theairintakechamberpreventspulsationoftheintakeair.Italsopreventsintakeairinterferenceineachcylinder.

Theengineelectroniccontrolsystemconsistsofvarioussensors,switchesandactuators.Thevarioussensorsdetecttheintakeairpressure,enginespeed,oxygendensityintheexhaustgas,enginecoolanttemperatureandatmosphericpressure,etc.,andconverttheinformationintoanelectricalsignal,whichissenttotheelectricalcontrolmodule(ECM).Basedonthesesignals,theECMdeterminestheinjectionvolumeandcalculatestheoptimumignitiontimingforthecurrentconditions.空气过滤是通过空气滤清器完成的，流入进气室的进气量是根据节气门开度以及发动机转速来确定的，由节气门开度控制的进气量从进气室分配到每个气缸的进气歧管，然后引入燃烧室。发动机电子控制系统由各种传感器、开关和执行机构。不同的传感器能够检测进气压力、发动机转速、废气里的氧气浓度、发动机冷却液温度和大气压力等等，并将这些信息转换成电信号，被发送到电子控制模块。根据这些信号，电子控制模块确定喷油量和计算目前状态下的最佳点火时间。

TheECMcontrolsnotonlythefuelinjectiontiming,butalsotheself-diagnosticfunctionwhichrecordstheoccurrenceofamalfunction,ignitiontimingcontrol,idlespeedcontrol.TheelectroniccontrolsystemisshowninFig.2-15.1.EFImanifoldrelay(电喷歧管继电器)2.variableresistor(可变电阻)3.engineECU(发动机电控单元)4.fuelpumpECU(燃油泵电控单元)5.vacuumsensor(真空传感器)

6.ACISVSV(谐波进气增压系统真空电磁阀)7.No.2knocksensor(第二爆震传感器)8.No.1knocksensor(第一爆震传感器)9.watertemperaturesensor(水温传感器)10.intakeairtemperaturesensor(进气温度传感器)Fig.2-15ElectroniccontrolsystemThrottleBodyFuelInjectioniscalledsinglepointfuelinjectionsystem.Fuelisinjectedintotheareaaroundthethrottlevalve,whereairvelocityisatamaximum,thusensuringfueldropletsarethoroughlyatomizedandwillbedistributedthroughouttheairmass.PortFuelInjection(alsocalledmultiple-pointfuelinjection)systemsuseasolenoidfuelinjectorwithacoilandaspringtoopenandclosetheneedlevalveineachcylinder.Gasolineisinjectedintotheintakemanifoldabovetheintakevalve70-100mm.节气门体喷射被称为单点燃油喷射系统，燃料被注入到节气门附近气流速度最大的区域，从而保证燃料充分雾化，均匀地与空气混合。2.7CoolingSystemInternalcombustionenginecoolingreferstothecoolingofaninternalcombustionengine,typicallyusingeitherairoraliquid.Heatenginesgeneratemechanicalpowerbyextractingenergyfromheatflows,muchasawaterwheelextractsmechanicalpowerfromaflowofmassfallingthroughadistance.Enginesarenotperfectlyefficient,somoreheatenergyenterstheenginethancomesoutasmechanicalpower;theremainderiswasteheatandmustberemoved.Internalcombustionenginesremovewasteheatthroughcoolintakeair,hotexhaustgases,andexplicitenginecooling.Engineswithhigherefficiencyhavemoreenergyleaveasmechanicalmotionandlessaswasteheat.Somewasteheatisessential:itguidesheatthroughtheengine,muchasawaterwheelworksonlyifthereissomeexitvelocity(energy)inthewastewatertocarryitawayandmakeroomformorewater.Thus,allheatenginesneedthecoolingtooperate.Coolingisalsoneededbecausehightemperaturesdamageenginematerialsandlubricants.Internal-combustionenginesburnsfuelhotterthanthemeltingtemperatureofenginematerials,andhotenoughtosetfiretolubricants.Enginecoolingremovesenergyfastenoughtokeeptemperatureslowsotheenginecansurvive.内燃机冷却是指冷却内燃机，通常使用的是空气或液体。热力发动机通过吸收来自热流的能量产生机械能，就像水车源源不断从高处落下的水吸收机械能一样。发动机并非完全高效，因此只有一部分热能被转化成机械能，其余的就是废热，必须要被清除。Somehigh-efficiencyenginesrunwithoutexplicitcoolingandwithonlyaccidentalheatloss,adesigncalledadiabatic.Forexample,10,000mile-per-gallon“cars”fortheshelleconomychallengeareinsulated,bothtotransferasmuchenergyaspossiblefromhotgasestomechanicalmotion,andtoreducereheatlosseswhenrestarting.Suchenginescanachievehighefficiencybutcompromisepoweroutput,dutycycle,engineweight,durability,andemissions.Mostinternalcombustionenginesarefluidcooledusingeitherair(agaseousfluid)oraliquidcoolantrunthroughaheatexchanger(radiator)cooledbyair.Thewatermaybeuseddirectlytocooltheengine,butoftenhassediment,whichcanclogcoolantpassages,orchemicals,suchassalt,thatcanchemicallydamagetheengine.Thus,enginecoolantmayberunthroughaheatexchangerthatiscooledbythewater.大多数内燃机是利用空气（气态流体）或冷却液流经空气冷却的热交换器（散热器）进行流动冷却的。水可直接用于冷却发动机，但往往有沉积物，可以堵塞冷却通道，或化学品，如盐，可以化学腐蚀发动机。因此，发动机冷却液可通过一个被水冷却的热交换器。Mostliquid-cooledenginesuseamixtureofwaterandchemicalssuchasantifreezeandrustinhibitors.Someusenowateratall,insteadusingaliquidwithdifferentproperties,suchaspropyleneglycoloracombinationofpropyleneglycolandethyleneglycol.Most“air-cooled”enginesusesomeliquidoilcooling,tomaintainacceptabletemperaturesforbothcriticalenginepartsandtheoilitself.Therearemanydemandsonacoolingsystem.Onekeyrequirementisthatanenginefailsifjustonepartoverheats.Therefore,itisvitalthatthecoolingsystemkeepallpartsatsuitablylowtemperatures.Liquid-cooledenginesareabletovarythesizeoftheirpassagewaysthroughtheengineblocksothatcoolantflowmaybetailoredtotheneedsofeacharea.Locationswitheitherhighpeaktemperatures(narrowislandsaroundthecombustionchamber)orhighheatflow(aroundexhaustports)mayrequiregenerouscooling.对于冷却系统有很多要求，非常重要的一点是，即使有一个部件过热发动机也会发生故障，因此，冷却系统要保证所有部件都处于合适的温度这一点很关键。水冷发动机的缸体周围的水道尺寸各有不同，这样才能够达到随时调整冷却液的流动以满足不同区域的冷却需求。Thisreducestheoccurrenceofhotspots,whicharemoredifficulttoavoidwithaircooling.Onlythefixedpartsoftheengine,suchastheblockandhead,arecooleddirectlybythemaincoolantsystem.Movingpartssuchasthepistons,andtoalesserextentthecrankandrods,mustrelyonthelubricationoilasacoolant,ortoaverylimitedamountofconductionintotheblockandthencethemaincoolant.Liquid-cooledenginesusuallyhaveacirculationpump.Thefirstenginesreliedonthermo-syphoncoolingalone,wherehotcoolantleftthetopoftheengineblockandpassedtotheradiator,whereitwascooledbeforereturningtothebottomoftheengine.Circulationwaspoweredbyconvectionalone.Conductiveheattransferisproportionaltothetemperaturedifferencebetweenmaterials.Ifenginemetalisat250°Candtheairisat20°C,thenthereisa230°Ctemperaturedifferenceforcooling.Anair-cooledengineusesallofthisdifference.Incontrast,aliquid-cooledenginemightdumpheatfromtheenginetoaliquid,heatingtheliquidto135°C(Water'sstandardboilingpointof100°Ccanbeexceededasthecoolingsystemisbothpressurized,andusesamixturewithantifreeze)whichisthencooledwith20°Cair.水冷发动机通常有一个循环泵。第一代发动机仅仅依靠温差环流冷却系统实现冷却，其原理是热的冷却液离开发动机缸体顶部流入到散热器，散热器能够使冷却液在返回发动机底部之前将其冷却。支持循环进行的动力只是对流。Ineachstep,theliquid-cooledenginehashalfthetemperaturedifferenceandsoatfirstappearstoneedtwicethecoolingarea.However,propertiesofthecoolant(water,oil,orair)alsoaffectcooling.Thethermalconductivityofwaterisabout4timesthatofoil,whichcanaidheattransfer.Waterboilsataboutthesametemperaturedesiredforenginecooling.Thishastheadvantagethatitabsorbsagreatdealofenergywithverylittleriseintemperature(calledheatofvaporization),whichisgoodforkeepingthingscool,especiallyforpassingonestreamofcoolantoverseveralhotobjectsandachievinguniformtemperature.However,oncewaterboils,itisaninsulator,leadingtoasuddenlossofcoolingwheresteambubblesform.Unfortunately,steammayreturntowaterasitmixeswithothercoolant,soanenginetemperaturegaugecanindicateanacceptabletemperatureeventhoughlocaltemperaturesarehighenoughthatdamageisbeingdone.Anengineneedsdifferenttemperatures.Theinletincludingthecompressorofaturboand