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HowCarEnginesWorkHerewelldiscussthebasicideabehindanengine,andthengointodetailabouthowallthepiecesfittogetherandhowtoincreaseperformanceInternalCombustionAlmostallcarscurrentlyusewhatiscalledafourstrokecombustioncycletoconvertgasolineintomotion.ThefourstrokeapproachisalsoknownastheOttocycle,inhonorofNicholasOtto,whoinventeditin1867.TheyareIntakestrokeorsuckstrokeCompressionstrokeorsqueezestrokeCombustionstrokeorbangstrokeExhauststrokeorblowstrokeThepistonisconnectedtothecrankshaftbyaconnectingrod.Hereswhathappensastheenginegoesthroughitscycle1.Thepistonstartsatthetop,theintakevalveopens,andthepistonmovesdowntolettheenginetakeinacylinderfullofairandgasoline.Thisistheintakestroke.Onlythetiniestdropofgasolineneedstobemixedintotheairforthistowork.2.Thenthepistonmovesbackuptocompressthisfuel/airmixture.Compressionmakestheexplosionmorepowerful.3.Whenthepistonreachesthetopofitsstroke,thesparkplugemitsasparktoignitethegasoline.Thegasolinechargeinthecylinderexplodes,drivingthepistondown.4.Oncethepistonhitsthebottomofitsstroke,theexhaustvalveopensandtheexhaustleavesthecylindertogooutthetailpipe.Nowtheengineisreadyforthenextcycle,soitintakesanotherchargeofairandgas.Noticethatthemotionthatcomesoutofaninternalcombustionengineisrotational.Inanenginethelinearmotionisconvertedintorotationalmotionbythecrankshaft.Therotationalmotionisnicebecauseweplantoturnrotatethecarswheelswithitanyway.AlmostallcarstodayuseareciprocatinginternalcombustionenginebecausethisengineisRelativelyefficientcomparedtoanexternalcombustionengineRelativelyinexpensivecomparedtoagasturbineRelativelyeasytorefuelcomparedtoanelectriccarTheseadvantagesbeatanyotherexistingtechnologyformovingacararound.Nowletslookatallthepartsthatworktogethertomakethishappen.PartsofanEngineHeresaquickdescriptionofeachone,alongwithalotofvocabularythatwillhelpyouunderstandwhatallthecaradsaretalkingabout.CylinderThecoreoftheengineisthecylinder.Thepistonmovesupanddowninsidethecylinder.Theenginedescribedherehasonecylinder.Thatistypicalofmostlawnmowers,butmostcarshavemorethanonecylinderfour,sixandeightcylindersarecommon.Inamulticylinderenginethecylindersusuallyarearrangedinoneofthreewaysinline,Vorflatalsoknownashorizontallyopposedorboxer,asshowninthefollowingfigures.Figure1.InlineThecylindersarearrangedinalineinasinglebank.Figure2.VThecylindersarearrangedintwobankssetatanangletooneanother.Figure3.FlatThecylindersarearrangedintwobanksonoppositesidesoftheengine.Differentconfigurationshavedifferentsmoothness,manufacturingcostandshapecharacteristicsthatmakethemmoresuitableinsomevehicles.SparkplugThesparkplugsuppliesthesparkthatignitestheair/fuelmixturesothatcombustioncanoccur.Thesparkmusthappenatjusttherightmomentforthingstoworkproperly.ValvesTheintakeandexhaustvalvesopenatthepropertimetoletinairandfuelandtoletoutexhaust.Notethatbothvalvesareclosedduringcompressionandcombustionsothatthecombustionchamberissealed.PistonApistonisacylindricalpieceofmetalthatmovesupanddowninsidethecylinder.PistonringsPistonringsprovideaslidingsealbetweentheouteredgeofthepistonandtheinneredgeofthecylinder.TheringsservetwopurposesTheypreventthefuel/airmixtureandexhaustinthecombustionchamberfromleakingintothesumpduringcompressionandcombustion.Theykeepoilinthesumpfromleakingintothecombustionarea,whereitwouldbeburnedandlost.Mostcarsthatburnoilandhavetohaveaquartaddedevery1,000milesareburningitbecausetheengineisoldandtheringsnolongersealthingsproperly.CombustionchamberThecombustionchamberistheareawherecompressionandcombustiontakeplace.Asthepistonmovesupanddown,youcanseethatthesizeofthecombustionchamberchanges.Ithassomemaximumvolumeaswellasaminimumvolume.ThedifferencebetweenthemaximumandminimumiscalledthedisplacementandismeasuredinlitersorCCsCubicCentimeters,where1,000cubiccentimetersequalsaliter.Soifyouhavea4cylinderengineandeachcylinderdisplaceshalfaliter,thentheentireengineisa2.0literengine.IfeachcylinderdisplaceshalfaliterandtherearesixcylindersarrangedinaVconfiguration,youhavea3.0literV6.Generally,thedisplacementtellsyousomethingabouthowmuchpoweranenginehas.Acylinderthatdisplaceshalfalitercanholdtwiceasmuchfuel/airmixtureasacylinderthatdisplacesaquarterofaliter,andthereforeyouwouldexpectabouttwiceasmuchpowerfromthelargercylinderifeverythingelseisequal.Soa2.0literengineisroughlyhalfaspowerfulasa4.0literengine.Youcangetmoredisplacementeitherbyincreasingthenumberofcylindersorbymakingthecombustionchambersofallthecylindersbiggerorboth.ConnectingrodTheconnectingrodconnectsthepistontothecrankshaft.Itcanrotateatbothendssothatitsanglecanchangeasthepistonmovesandthecrankshaftrotates.CrankshaftThecrankshaftturnsthepistonsupanddownmotionintocircularmotionjustlikeacrankonajackintheboxdoes.SumpThesumpsurroundsthecrankshaft.Itcontainssomeamountofoil,whichcollectsinthebottomofthesumptheoilpan.EngineSubsystemsAnenginehasanumberofsystemsthathelpitdoitsjobofconvertingfuelintomotion.Mostofthesesubsystemscanbeimplementedusingdifferenttechnologies,andbettertechnologiescanimprovetheperformanceoftheengine.HeresalookatallofthedifferentsubsystemsusedinmodernenginesValvetrainThevalvetrainconsistsofthevalvesandamechanismthatopensandclosesthem.Theopeningandclosingsystemiscalledacamshaft.Thecamshafthaslobesonitthatmovethevalvesupanddown,asshowninFigure4.Mostmodernengineshavewhatarecalledoverheadcams.Thismeansthatthecamshaftislocatedabovethevalves,asyouseeinFigure5.Thecamsontheshaftactivatethevalvesdirectlyorthroughaveryshortlinkage.Olderenginesusedacamshaftlocatedinthesumpnearthecrankshaft.Rodslinkedthecambelowtovalveliftersabovethevalves.Thisapproachhasmoremovingpartsandalsocausesmorelagbetweenthecamsactivationofthevalveandthevalvessubsequentmotion.Atimingbeltortimingchainlinksthecrankshafttothecamshaftsothatthevalvesareinsyncwiththepistons.Thecamshaftisgearedtoturnatonehalftherateofthecrankshaft.Manyhighperformanceengineshavefourvalvespercylindertwoforintake,twoforexhaust,andthisarrangementrequirestwocamshaftsperbankofcylinders,hencethephrasedualoverheadcams.StartingsystemThestartingsystemconsistsofanelectricstartermotorandastartersolenoid.Whenyouturntheignitionkey,thestartermotorspinstheengineafewrevolutionssothatthecombustionprocesscanstart.Ittakesapowerfulmotortospinacoldengine.ThestartermotormustovercomeAlloftheinternalfrictioncausedbythepistonringsThecompressionpressureofanycylindersthathappenstobeinthecompressionstrokeTheenergyneededtoopenandclosevalveswiththecamshaftAlloftheotherthingsdirectlyattachedtotheengine,likethewaterpump,oilpump,alternator,etc.Becausesomuchenergyisneededandbecauseacarusesa12voltelectricalsystem,hundredsofampsofelectricitymustflowintothestartermotor.Thestartersolenoidisessentiallyalargeelectronicswitchthatcanhandlethatmuchcurrent.Whenyouturntheignitionkey,itactivatesthesolenoidtopowerthemotor.Above,wearediscussingabasicphilosophyofengine,andadetailedunderstandingofhowtointegrateallthecomponentstogether,andhowtoimprovetheperformanceofthatThus,theworkoftheengineforvehicleisveryimportant.汽车发动机如何工作在这里,我们将讨论的是一个发动机的基本理念,然后进入详细了解如何将所有部件结合在一起,以及如何提高性能内部燃烧目前几乎所有的汽车使用的是所谓的四冲程燃烧循环转换成汽油的方案。这种四冲程步骤,又被称为了奥托循环,由受人尊敬的尼古拉斯奥托在1867年发明的。他们分别是摄入冲程或吸吮冲程压缩冲程或挤压冲程燃烧冲程或重击冲程排气冲程或吹气冲程活塞通过连杆连接到曲柄轴。这是发动机通过运行周期产生的1.活塞在顶部启动,进气阀开启时,活塞向下移动,使发动机吸收满一缸空气和汽油。这是摄入冲程。只有很少的、微量的汽油需要加以混合到空气中以完成这项工作。2.然后活塞撤回直到压缩这种燃料/空气混合气。压缩,使爆炸更加强大。3.当活塞到达其冲程,火花塞发出一道火花,引燃汽油。汽油在气缸激发下装满,推动活塞下降。4.一旦活塞在其冲程下到达底部,排气阀门打开,排气叶片将气体排出汽缸的排气尾管。现在发动机开始准备下一个周期,因此,进另外的空气和汽油。应该注意到,这种源自于内燃机运动是轮流的。在发动机里,直线运动转化为旋转运动是由曲柄轴完成的。旋转运动是好的,因为我们计划无论如何把它(旋转)用于汽车的车轮。几乎所有现代汽车用往复式内燃机,因为这种发动机效率比较高(相比外部内燃机)价格相对低廉(相比燃气轮机)相对容易加油(相比电动汽车)这些优势击败其他任何现有的技术,为汽车运转所用。现在让我们看看所有部件如何共同工作,使这一切发生。发动机部分这里快速描述每个部件,连同大量的词汇帮助您了解所有的汽车广告所谈论的内容。发动机的核心是汽缸。活塞在汽缸内上下活动。这里形容发动机有一个汽缸。这是最典型的草坪割草机,但多数车有一个以上的汽缸(4,6,8缸是常见的。在多缸发动机里汽缸通常都被排列成三个方式直列,V式排列或平列(也称为横向反对或拳击手),这通过以下一些图形可以描述出来。
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