汽车专业英语unit2

PAGEPAGE8UNIT2AUTOMOTIVEENGINE2.1PurposeandLocationsofEnginesThepurposeofanautomotiveengineistosupplythepowerneededtomovethevehicle.Theengineproducesthispowerbyburningfuelinsideit.Becausetheengineburnsfuelinside,orinternally,theengineisknownasaninternalcombustionengine（ICE）.汽车发动机的功用是汽车行驶提供必需的动力。发动机通过它内部的燃料燃烧来产生动力。由于发动机在其内部燃烧燃料，所以发动机被称作内燃机。Enginesmaybefueledbygasoline,propane（LPG-liquefiedpetroleumgas）,ordieselfuel.Compressednaturalgas（CNG）mayalsobeusedinsomevehicles.发动机燃料可以是汽油、丙烷（液化石油汽体）或柴油。压缩天燃气也可以用在一些车辆上。befueledby通过…得到燃料Mostautomotiveenginesarelocatedatthefrontofthevehicle.Manyenginesdrivetherearwheels.Thisrequiresalongdriveshaftextendingformthefrontwheelstotherearwheels.Otherenginesdrivethefrontwheels.Intherear-wheel-drivearrangement,theenginesitslongitudinally.Itslongdimensionisfromfronttoback.大多数汽车发动机位于汽车前方。许多发动机由后轮驱动。这需要一根长传动轴从前轮延伸到后轮。其它发动机由前轮驱动。在后轮驱动布置中，发动机纵向放置。它前后尺寸最长。Inthefront-wheel-drivearrangement,theenginesitscrosswise,transversely.Witheitherarrangement,thepoweriscarriedtothedrivewheels（rearorfront）bygearsandshafts.在前轮驱动布置中，发动机横向放置。不管哪种放置方式，动力都是通过齿轮和轴传递到驱动轮。Crosswise交叉地，横向的Somecarshavetheenginemountedinbackofthefrontseat.Thisiscalledamid-enginearrangement.Othercarshavebeenbuiltwiththeenginemountedattherear,inbackofrearseat.TheVolkswagen"beetle"isanexampleofrear.一些轿车把发动机安装在前排座位的后面，这称为中置发动机布置。其它轿车发动机安装在车的尾部，也就是后排座的后面。比如：大众汽车甲壳虫就是采用这种发动机后置布置。2.2EngineTypesVariouskindsofenginesareusedinautomotivevehicles.Thetwomajortypesare:机动车辆上采用各种各样的发动机，其两种主要类型为：1.Thepistonengineinwhichpistonsmoveupanddown,orreciprocate,intheenginecylinders.Thisistheengineusedinallcarstoday,exceptforsomemodelsofMazda.活塞发动机，活塞在其气缸内上下或往复运动。这就是现今轿车所采用的发动机形式，除了马自达的一些型号发动机。2.TheWankelrotaryengineinwhichrotorsrotate,orspin.TheMazdaMotorCorporationofJapanisthemajormanufacturerofthisengine.汪克尔转子发动机，由其转子回转。日本马自达发动机公司是这类发动机的主要生产商。Therearetwotypesofpistonengines-sparkignition（SI）andcompressionignition（CI）.Spark-ignitionenginesuseanelectricignitionsystemwithsparkplugs.Electricsparksatthesparkplugsignite,orsetfire,thefuelintheenginecylinders.Thecombustionofthefuelmakestheenginerunandproducepower.Thisisthetypeofengineusedinmostproducepower.Thisisthetypeofengineusedinmostautomotivevehicles.有两种类型的活塞发动机：火花点火和压缩点火。火花点火发动机采用带有火花塞的电子点火系统。火花塞的电子点火点燃发动机气缸中的燃料。燃料燃烧使发动机运转并产生动力。这是在大多数产生动力的发动机所采用的形式，这种类型的发动机在大部分机动车辆上使用。Thecompression-ignitionenginethedieselusestheheatofcompressiontoignitethefuel.Whenairiscompressed,itgetsveryhot.Inthedieselengine,theairiscompressedsomuchthatitstemperaturegoesupto1,000degreesFahrenheit（538degreesCelsius）orhigher.Thedieselfuelissprayedintothisveryhotairandisignitedbytheheat.Someautomobileshavedieselengines.Manyheavy-dutytrucksandbusesarepoweredbydieselengines.压缩点火发动机，柴油机使用压缩产生的热量来点燃燃料。当空气被压缩时，会变得非常热。柴油机内空气压缩温度可过1000华氏以上（538摄氏度）。然后柴油被喷射到这种热空气中，并被这种热度点燃。一些汽车上采用柴油机。大多重型卡车和客车由柴油机提供动力。Thereareotherenginesstillintheexperimentalstagethatmightsomedaybecomeimportant.Theseincludegas-turbineengines,steamengines,Stirlingengines,andelectricmotors.还有一些其它的发动机仍处于实验阶段，总有一天会变得重要。它们包括燃气涡轮发动机、蒸汽汽、斯特林（热气体）发动机和电动机。2.3BasicEngineSystemsAspark-ignitionenginerequiresfourbasicsystemstorun.Dieselenginesrequirethreeofthesesystems.Theyarefuelsystem,ignitionsystem（exceptdiesel）,lubricatingsystemandcoolingsystem.Eachperformsabasicjobinmakingtheenginerun.Thesearedescribedbrieflybelow.火花点火发动机运转需要4个基本系统。柴油发动机需要其中的3个。它们是燃料系统，点火系统（除了柴油机），润滑系统和冷却系统。其每个系统在使发动机运转时完成一个基本工作。简要介绍如下：2.3.1FuelSystemsThefuelsystemsuppliesgasolineordieselfueltotheengine.Thisfuelismixedwithairtomakeacombustiblemixture（amixturethatwillburn）.Eachcylinderisrepeatedlyfilledwiththemixture.Then,themixtureisignitedandburned,producinghighpressure.Thehighpressuremakesthepistonsmove（orrotorsspin）.Thisturnsshaftsthatrotatethewheels,causingthevehicletomove.燃料系统给发动机提供汽油或柴油燃料。燃料与空气混合形成可燃混合气（一种会燃烧的混合物）。气缸被反复填充这种混合气体。然后被点燃、燃烧，产生高压，推动活塞运动（或转子旋转）。这使车轴带到车轮旋转，从而使车辆移动。2.3.2IgnitionsystemEverytimethefuelsystemdeliversair/fuelmixturetoacylinder,theignitionsystemfollowsupbydeliveringanelectricspark.Thisignitesthemixturewhichcreatesthehighpressurethatmovesthepistonsandturnsthecarwheels.Theactionisrepeatedmanytimeseachsecondwhiletheengineisrunning.每当燃料系统传送可燃混合气给气缸，点火系统随后会产生电火花来点燃混合气，从而产生高压，使活塞运动和车轮运转。当发动机运转时，每秒钟这个动作重复多次。Theignitionsystemtakesthelowvoltage,ofthebatteryandbuildsituptoaveryhighvoltage:ashighas47,000voltsinsomesystems.Thishighvoltagejumpsthegapsinthesparkplugs,producingthesparksthatignitetheair/fuelmixtureintheenginecylinders.点火系统把蓄电池的低压增到高压，在一些系统中可达到47000伏。高压击穿火花塞（两电极之间）间隙，产生电火花，点燃发动机气缸内的可燃混合气。2.3.3LubricatingsystemTheenginehasmanymovingmetalparts.Ifmetalpartsrubagainsteachother,theywillwearrapidly.Topreventthis,engineshavelubricatingoil.Theoilgetsbetweenthemetalpartssotheyslideontheoil,andnotoneachother.发动机有许多运动金属部件。如果金属部件之间相互磨擦，会加速磨损。为防止这样，发动机带有润滑油。润滑油充斥在金属部件之间，从而使它们在油面上滑动，而不是在其表面。Thelubricatingsystemhasanoilpanatthebottomoftheenginewhichholdsseveralquarts（liters）ofoil.Anoilpump,drivenbytheengine,sendsoilfromthisreservoirthroughtheengine.Aftercirculatingthroughtheengine,theoildropsbackdownintotheoilpan.Theoilpumpcontinuestocirculatetheoilaslongastheengineisrunning.润滑系统油底壳位于发动机的底部，它可保存几夸脱（升）的润滑油。油泵由发动机驱动把润滑油从油底壳送到发动机各个部件，润滑油在发动机内循环后，回落到油底壳中。只要发动机不断运转，油泵就会连续循环润滑油。夸脱(容量单位=1/4加仑,约1.14升)throughprep，通过，到，各处，各地wentthroughthetunnel.atourthroughFrance.adj.直达的,直通的athroughbus一辆直达的公共汽车；adv，从头到尾，完全，彻底seeamatterthrough，drovethroughtotheirfinaldestination.2.3.4CoolingsystemWherethereisfire（combustion）,thereisheat.Burningoftheair/fuelmixtureraisesthetemperatureinsidetheenginecylindersseveralthousanddegrees.Someofthisheatproducesthehighpressurethatmovesthepistonstoproducepower.Someoftheheatleavesthecylinderswiththeexhaustgas.Theexhaustgasiswhatisleftaftertheair/fuelmixtureburns.Itisclearedoutofthecylindersaftercombustioniscomplete.有火（燃烧）的地方，就会有热。可燃混合气的燃烧会把发动机气缸内的温度提升到几千摄氏度。其中一部分热量产生高压推动活塞运动来产生动力。另外一部分热量随着废气排出气缸。废气是指可燃混合气燃烧后残留的气体。它在燃烧完成后被排出气缸。Someoftheheatisremovedbythecirculatingoil.Afterthehotoildropsdownintotheoilpan,theoilgivesupsomeofthisheattotheairpassingundertheoilpan.Therestoftheheatisremovedbythecoolingsystem.还有一部分热量由循环润滑油带走。灼热的润滑油落到油底壳后，会把部分热量传给通过油底壳下方的空气。其余热量由冷却系散发。2.3.5OtherenginesystemsAnenginewillrunwiththefourbasicsystemsdescribedabove—fuel,ignition,lubricating,andcooling.However,threeotherrelatedsystemsarealsonecessary.Thesearetheexhaustsystem,theemission-controlsystem,andthestartingsystem.发动机运转需要上述4个基本系统－燃料、点火、润滑和冷却。但是，还有另外三个相关系统也是必需的。它们是排放系统、废气处理（排气净化）系统和起动系统。Theexhaustsystemreducesthenoiseoftheburnedgasesleavingtheenginecylindersandcarriestheseexhaustgasessafelyawayfromthepeopleinthecar.Theemission-controlsystemisrequiredbylawtoreducetheairpollutiontheenginecouldproduce.Thestartingsystemisneededtocranktheengine.Abatteryprovidestheelectricpowertooperatethestartingmotorandtheignitionsystemduringcranking.排放系统功能，一方面减小燃烧废气排出气缸时所产生的噪声，另一方面把这些废气从车中乘客身边安全带走。废气处理（排放控制）系统是法规所要求的用来降低发动机所产生的空气污染。起动系统用来转动发动机曲轴。蓄电池在起动时为开动起动机和点火系统提供电力。Crankn.曲轴曲柄→vt.转动曲柄Cranking摇动，起动2.4EnergyConversionTheinternalcombustionengineisadeviceusedtoconvertthechemicalenergyofthefuel（gasolineordieselfuel）intoheatenergy,andthentoconvertthisheatenergyintousablemechanicalenergy.Thisisachievedbycombiningtheappropriateamountsofairandfuel,andburningthemixtureinanenclosedcylinderatacontrolledrate.Amovablepistoninthecylinderisforceddownbytheexpandinggasesofcombustion.内燃机是一种把（汽油或柴油）燃料的化学能转变成热能，再转换成可利用的机械能的装置。这通过混合适量的空气和燃料，并在密闭的汽缸中按照控制速度燃烧来实现。气缸中活塞由燃烧气体膨胀作功来压下。Enclosevt.装入，围绕Enclosedadj.被附上的，封闭的enclosern.外壳，外罩。Anaverageair/fuelratioforgoodcombustionisabout15partsofairto1partoffuelbyweight.Thismeansthatforeverygallonofgasolineburned,theoxygenisabout9,000to10,000gallonsofairisrequired.Airisabout21%oxygenand78%nitrogen.燃烧良好的空燃比，按质量平均大约是15：1。这意味着每加仑汽油完全燃烧所需的空气质量大约在9000到10000加仑。空气中氧气成份点21%，氮气占78%。air/fuelratio空气/燃油混合比，即空燃比，可燃混合气中空气质量与燃油质量之比。Dieselenginesoperateonamuchwiderair/fuelratio,sinceairintakeisnotregulatedonmostdiesels.Ratiosmayrangefromabout20:1toabout100:1.Thefact,plusthehighcompressionofthediesel,makesitaveryfuelefficientengine.因为进气量在大多数内柴油机上不规则的，柴油机有更宽的空燃比。其范围大约在20：1到100：1之间。实际上，加上柴油机的高压缩比，使其成为极其节约燃油的发动机。fuelefficient节约燃油的，燃油经济性高的Themovablepistoninthecylinderisconnectedtothetopofaconnectingrod.Thebottomoftheconnectingrodisattachedtotheoffsetportionofacrankshaft.Asthepistonisforcedown,thisforceistransferredtothecrankshaft,causingthecrankshafttorotate.Thereciprocating（backandforthorupanddown）movementofthepistonisconvertedtorotary（turning）motionofthecrankshaft,whichsuppliesthepowertodrivethevehicle.气缸活塞与连杆上端相连。连杆底部则连到曲轴的偏心部。当活塞被压下时，驱动力被传递到曲轴，并带动曲轴旋转。活塞的往复运动转化成曲轴的旋转运动，从而为驱动车辆提供动力。Theefficiencyoftheinternalcombustion,reciprocatingpistonengineinconvertingthepotentialenergyinfuelintomechanicalenergyisonlyabout33%.Oftheavailableheatenergyinthefuel,aboutone-thirdislostthroughtheexhaustsystemandone-thirdisabsorbedanddissipatedbythecoolingsystem.Oftheremainingone-third,aboutone-halfislostthroughavailableatthevehicle’sdrivewheels.活塞发动机在转化燃料的势能为机械能时的效率大约只有33%。对于燃料的可用热能，大概有1/3损失在排放系统中，另外1/3被冷却系统吸收和散发。在剩余的1/3中，约有一半完全利用在车辆的驱动轮上。Theoverallefficiencyofthedieselengineisconsiderablyhigherthanthatofthegasolineengine.Thereasonsforthisare:thehighercompressionratio,thehigherair/fuelratio,andthehigherheatvalueofthefuel.Theusefulpowerdevelopedatthedrivewheelsbyadieselengineisabout25%ascomparedto15%byagasolineengine.柴油机的总效率明显高于汽油机。原因在于柴油机的高压缩比，高空燃比和柴油的高热值。柴油机传递到车轮的有效功率大约在25%，而汽油机只有15%。heatvalue高热值，单位燃料燃烧时释放的热量。ascomparedto同…相比2.5Four-Stroke-CycleGasolineEngineOperationThemovementofthepistonfromitsuppermostposition（TDC,topdeadcenter）toitslowestposition（BDC,bottomdeadcenter）iscalledastroke.Mostautomobileenginesoperateonthefourstroke-cycleprinciple.Aseriesofeventsinvolvingfourstrokesofthepistoncompletesonecycle.Figure2-1.Theseeventsare:（1）theintakestroke,（2）thecompressionstroke,（3）thepowerstroke,and（4）theexhauststroke.Tworevolutionsofthecrankshaftandonerevolutionofthecamshaftarerequiredtocompleteonecycle.从活塞的最上端（上止点）到它的最下端（下止点）的运动过程称为一个行程。大多数汽车发动机根据四冲程原理工作。四个活塞行程完成一个工作周期。这4个行程是进气行程，压缩行程，作功行程和排气行程。同时，需要曲轴转动两圈，凸轮轴转动一圈。Event事件→过程，（内燃机）行程Ontheintakestrokethepistonispulleddowninthecylinderbythecrankshaftandconnectingrod.Duringthistimetheintakevalveisheldopenbythecamshaft.Sincethepistonhasmoveddowninthecylinder,creatingalow-pressurearea（vacuum）,atmosphericpressureforcesamixtureofairandfuelpasttheintakevalveintothecylinder.Atmosphericpressureisapproximately14.7poundspersquareinch（about101.35kilopascals）atsealevel.Pressureinthecylinderduringtheintakestrokeisconsiderablylessthanthis.Thepressuredifferenceistheforcethatcausestheair/fuelmixturetoflowintothecylinder,sincealiquidoragas（vapor）willalwaysflowfromahigh-pressuretoalow-pressurearea.在进气行程中，活塞在气缸中被曲轴和连杆拉下。这时，进气门被凸轮轴开启。因为活塞在气缸中向下移动，产生一个低压区（真空），大气压将可燃混合气通过进气门压入气缸。大气压在海平面上大约为14.7磅/平方英寸(101.35千帕)。进气行程中气缸内压力远小于大气压力。因为液体或气体（蒸汽）总是从高压区流向低压区，所以这个压力差促使可燃混合气注入汽缸。AsthepistonismovedupbythecrankshaftfromBDC,theintakevalvecloses.Theair/fuelmixtureistrappedinthecylinderabovethepiston.Furtherpistontravelcompressestheair/fuelmixturetoapproximatelyone-eighthofitsoriginalvolume（approximately8:1compressionratio）whenthepistonhasreachedTDC.Thiscompletesthecompressionstroke.当活塞曲轴带动从下止点向上移时，进气门关闭。可燃混合气封在气缸内活塞的上方。当活塞到达上止点时，可燃混合气体积由活塞运动压缩至其原来体积的约1/8（8:1的压缩比）。这就完成了压缩行程。WhenthepistonisatornearTDC,theair/fuelmixtureisignited.Theburningoftheair/fuelmixture（combustion）takesplaceatacontrolledrate.Expansionoftheburningmixturecausesarapidriseinpressure.Thisincreasedpressureforcesthepistondownonthepowerstroke,causingthecrankshafttorotate.当活塞移动到上止点附近时，可燃混合气被点燃。混合物的燃烧按照控制速度进行。燃烧气体体积膨胀使（气缸内）压力迅速上升。在此作功行程中，气体增压推动活塞向下移动，带动曲轴旋转。Attheendofthepowerstrokethecamshaftopenstheexhaustvalve,andtheexhauststrokebegins.Remainingpressureinthecylinder,andupwardmovementofpiston,forcetheexhaustgasesoutofthecylinder.Attheendoftheexhauststroke,theexhaustvalveclosesandtheintakevalveopens,repeatingtheentirecycleofeventsoverandoveragain.在作功行程结束时，凸轮轴打开排气门，进入排气行程。气缸中剩余压力和活塞的向上移动把废气排出气缸。排气行程结束时，排气门关闭，进气门打开，反复不断重复整个冲程循环周期。overandoveragain反复不断地Tostarttheengine,somemethodofcrankingtheengineisrequiredtoturnthecrankshaftandcausepistonmovement.Thisisdonebythestartermotorwhentheignitionkeyisinthestartposition.Whensufficientair/fuelmixturehasenteredthecylindersandisignited,thepowerstrokescreateenoughenergytocontinuecrankshaftrotation.Atthepoint,theignitionkeyisreleasedtotherunpositionandthestarterisdisengaged.为了起动发动机，需要一些起动方法来转动发动机曲轴，使活塞（上下）运动。这在点火开关处于起动位置时由起动机来实现。当足量的可燃混合气进入气缸并且被点燃，作功行程能产生足够的热量来继续曲轴旋转，此时点火开关释放至运行位置，起动机解除。Sufficientenergyisstoredintheflywheelandotherrotatingpartsonthepowerstroketomovethepistonandrelatedpartsthroughtheotherthreestrokes（exhaust,intake,andcompression）.Theamountofair/fuelmixtureallowedtoenterthecylinderdeterminesthepowerandspeeddevelopedbytheengine.在作功行程中，能量被存储在飞轮和其它旋转部件中，并在其它三个行程（排气、进气和压缩）中推动活塞和相关部件。进入气缸中的可燃混合气的量决定着该发动机的功率和转速。EXERCISEI.Answerthefollowingquestions:1.Whatisthepurposeofanautomotiveengine?Itissupplythepowerneededtomovethevehicle.2.Whatisthedifferencebetweenagasolineengineandadieselengine?Theoverallefficiencyofthedieselengineishigherthanthatofthegasolineengine.P15Gasolineengineissparkignitionanddieselengineiscompressionignition.3.Whatarethebasicsystemstorunasparkignitionenginerequired?Theyarefuelsystem,ignitionsystem,lubricatingsystemandcoolingsystem.4．Listthestrokesofafour-stroke-cyclegasolineeng