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外文翻译 --汽车发动机如何工作.doc

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外文翻译 --汽车发动机如何工作.doc

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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