汽车发动机如何工作中英文翻译文档格式.docx

汽车发动机如何工作中英文翻译文档格式.docx

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and"

dualoverheadcams"

tunedportfuelinjection."

Whatdoesallofthatmean?

Ifyouhaveeverwonderedaboutthiskindofstuff,thenreadon--Inthisarticle,we'

lldiscussthebasicideabehindanengineandthengointodetailabouthowallthepiecesfittogether,whatcangowrongandhowtoincreaseperformance.

Thepurposeofagasolinecarengineistoconvertgasolineintomotionsothatyourcarcanmove.Currentlytheeasiestwaytocreatemotionfromgasolineistoburnthegasolineinsideanengine.Therefore,acarengineisaninternalcombustionengine--combustiontakesplaceinternally.

Twothingstonote:

Therearedifferentkindsofinternalcombustionengines.Dieselenginesareoneformandgasturbineenginesareanother.SeealsothearticlesonHEMIengines,rotaryenginesandtwo-strokeengines.Eachhasitsownadvantagesanddisadvantages.

Thereissuchathingasanexternalcombustionengine.Asteamengineinold-fashionedtrainsandsteamboatsisthebestexampleofanexternalcombustionengine.Thefuel（coal,wood,oil,whatever）inasteamengineburnsoutsidetheenginetocreatesteam,andthesteamcreatesmotioninsidetheengine.Internalcombustionisalotmoreefficient（takeslessfuelpermile）thanexternalcombustion,plusaninternalcombustionengineisalotsmallerthananequivalentexternalcombustionengine.Thisexplainswhywedon'

tseeanycarsfromFordandGMusingsteamengines

Almostallcarstodayuseareciprocatinginternalcombustionenginebecausethisengineis:

Relativelyefficient（comparedtoanexternalcombustionengine）

Relativelyinexpensive（comparedtoagasturbine）

Relativelyeasytorefuel（comparedtoanelectriccar）

Theseadvantagesbeatanyotherexistingtechnologyformovingacararound.

Tounderstandthebasicideabehindhowareciprocatinginternalcombustionengineworks,itishelpfultohaveagoodmentalimageofhow"

internalcombustion"

works.OnegoodexampleisanoldRevolutionaryWarcannon.Youhaveprobablyseentheseinmovies,wherethesoldiersloadthecannonwithgunpowderandacannonballandlightit.Thatisinternalcombustion.

Almostallcarscurrentlyusewhatiscalledafour-strokecombustioncycletoconvertgasolineintomotion.Thefour-strokeapproachisalsoknownastheOttocycle,inhonorofNikolausOtto,whoinventeditin1867.Thefourstrokesareillustratedbellow,theyare:

Intakestroke

Compressionstroke

Combustionstroke

Exhauststroke

Thepistonisconnectedtothecrankshaftbyaconnectingrod.Asthecrankshaftrevolves,ithastheeffectof"

resettingthecannon."

Here'

swhathappensastheenginegoesthroughitscycle：

1.Thepistonstartsatthetop,theintakevalveopens,andthepistonmovesdowntolettheenginetakeinacylinder-fullofairandgasoline.Thisistheintakestroke.Onlythetiniestdropofgasolineneedstobemixedintotheairforthistowork.

2.Thenthepistonmovesbackuptocompressthisfuel/airmixture.Compressionmakestheexplosionmorepowerful.

3.Whenthepistonreachesthetopofitsstroke,thesparkplugemitsasparktoignitethegasoline.Thegasolinechargeinthecylinderexplodes,drivingthepistondown.

4.Oncethepistonhitsthebottomofitsstroke,theexhaustvalveopensandtheexhaustleavesthecylindertogooutthetailpipe.

Thentheenginegetsreadyforthenextcircle.

Cylinders,DisplacementandOtherEngineParts

Thecoreoftheengineisthecylinder,withthepistonmovingupanddowninsidethecylinder.Theenginedescribedabovehasonecylinder.Thatistypicalofmostlawnmowers,butmostcarshavemorethanonecylinder（four,sixandeightcylindersarecommon）.Inamulti-cylinderengine,thecylindersusuallyarearrangedinoneofthreeways:

inline,Vorflat（alsoknownashorizontallyopposedorboxer）,asshowninthefollowingfigures.

Differentconfigurationshavedifferentadvantagesanddisadvantagesintermsofsmoothness,manufacturing-costandshapecharacteristics.Theseadvantagesanddisadvantagesmakethemmoresuitableforcertainvehicles.

Displacement

Thecombustionchamberistheareawherecompressionandcombustiontakeplace.Asthepistonmovesupanddown,youcanseethatthesizeofthecombustionchamberchanges.Ithassomemaximumvolumeaswellasaminimumvolume.ThedifferencebetweenthemaximumandminimumiscalledthedisplacementandismeasuredinlitersorCCs（CubicCentimeters,where1,000cubiccentimetersequalsaliter）.

Valves

Theintakeandexhaustvalvesopenatthepropertimetoletinairandfuelandtoletoutexhaust.Notethatbothvalvesareclosedduringcompressionandcombustionsothatthecombustionchamberissealed.

Piston

Apistonisacylindricalpieceofmetalthatmovesupanddowninsidethecylinder.

Pistonrings

Pistonringsprovideaslidingsealbetweentheouteredgeofthepistonandtheinneredgeofthecylinder.Theringsservetwopurposes:

∙Theypreventthefuel/airmixtureandexhaustinthecombustionchamberfromleakingintothesumpduringcompressionandcombustion.

∙Theykeepoilinthesumpfromleakingintothecombustionarea,whereitwouldbeburnedandlost.

Mostcarsthat"

burnoil"

andhavetohaveaquartaddedevery1,000milesareburningitbecausetheengineisoldandtheringsnolongersealthingsproperly.

Connectingrod

Theconnectingrodconnectsthepistontothecrankshaft.Itcanrotateatbothendssothatitsanglecanchangeasthepistonmovesandthecrankshaftrotates.

Crankshaft

Thecrankshaftturnsthepiston'

supanddownmotionintocircularmotion.

Sump

Thesumpsurroundsthecrankshaft.Itcontainssomeamountofoil,whichcollectsinthebottomofthesump（theoilpan）.

ValveTrainsandSystems

Thevalvetrainconsistsofthevalvesandamechanismthatopensandclosesthem.Theopeningandclosingsystemiscalledacamshaft.Thecamshafthaslobesonitthatmovethevalvesupanddown。

Mostmodernengineshavewhatarecalledoverheadcams.Thismeansthatthecamshaftislocatedabovethevalves.Thecamsontheshaftactivatethevalvesdirectlyorthroughaveryshortlinkage.Olderenginesusedacamshaftlocatedinthesumpnearthecrankshaft.Thisapproachhasmoremovingpartsandalsocausesmorelagbetweenthecam'

sactivationofthevalveandthevalve'

ssubsequentmotion.Atimingbeltortimingchainlinksthecrankshafttothecamshaftsothatthevalvesareinsyncwiththepistons.Thecamshaftisgearedtoturnatone-halftherateofthecrankshaft.Manyhigh-performanceengineshavefourvalvespercylinder（twoforintake,twoforexhaust）,andthisarrangementrequirestwocamshaftsperbankofcylinders,hencethephrase"

dualoverheadcams."

IgnitionandCoolingSystems

Theignitionsystemproducesahigh-voltageelectricalchargeandtransmitsittothesparkplugsviaignitionwires.Thechargefirstflowstoadistributor,whichyoucaneasilyfindunderthehoodofmostcars.Thedistributorhasonewiregoinginthecenterandfour,six,oreightwires（dependingonthenumberofcylinders）comingoutofit.Theseignitionwiressendthechargetoeachsparkplug.Theengineistimedsothatonlyonecylinderreceivesasparkfromthedistributoratatime.Thisapproachprovidesmaximumsmoothness.

CoolingSystem

Thecoolingsysteminmostcarsconsistsoftheradiatorandwaterpump.Watercirculatesthroughpassagesaroundthecylindersandthentravelsthroughtheradiatortocoolitoff.Inafewcars（mostnotablyVolkswagenBeetles）,aswellasmostmotorcyclesandlawnmowers,theengineisair-cooledinstead.Air-coolingmakestheenginelighterbuthotter,generallydecreasingenginelifeandoverallperformance.

Air-intakeandStartingSystems

Mostcarsarenormallyaspirated,whichmeansthatairflowsthroughanairfilteranddirectlyintothecylinders.High-performanceenginesareeitherturbochargedorsupercharged,whichmeansthataircomingintotheengineisfirstpressurizedtoincreaseperformance.Theamountofpressurizationiscalledboost.Aturbochargerusesasmallturbineattachedtotheexhaustpipetospinacompressingturbineintheincomingairstream.Asuperchargerisattacheddirectlytotheenginetospinthecompressor.

StartingSystem

Thestartingsystemconsistsofanelectricstartermotorandastartersolenoid.Whenyouturntheignitionkey,thestartermotorspinstheengineafewrevolutionssothatthecombustionprocesscanstart.Ittakesapowerfulmotortospinacoldengine.Thestartermotormustovercome:

∙Alloftheinternalfrictioncausedbythepistonrings

∙Thecompressionpressureofanycylinder（s）thathappenstobeinthecompressionstroke

∙Theenergyneededtoopenandclosevalveswiththecamshaft

∙Allofthe"

other"

thingsdirectlyattachedtotheengine,likethewaterpump,oilpump,alternator,etc.

Becausesomuchenergyisneededandbecauseacarusesa12-voltelectricalsystem,hundredsofampsofelectricitymustflowintothestartermotor.Thestartersolenoidisessentiallyalargeelectronicswitchthatcanhandlethatmuchcurrent.Whenyouturntheignitionkey,itactivatesthesolenoidtopowerthemotor.

LubricationandFuelSystems

Thelubricationsystemmakessurethateverymovingpartintheenginegetsoilsothatitcanmoveeasily.Thetwom