外文翻译--柴油发动机工作原理.doc

无锡太湖学院2009届本科生毕业设计（论文）翻译1Adieselengineworks【Abstract】Inadieselenginecylinder,thepistoninthepartoftheworkcycleofcompressedgas,andinanotherpartoftheworkcycleofthecombustiongasmixturewithinthecylindersothepistontopsurfaceexpansionhighpressure(about116120Kgf/cm2)underhightemperature(about569C)gasrole,andthepressurethroughthepistonpin,connectingrodtothecrankshaft.Canbeseenthatthepistonisalongtimeunderhightemperatureandhighpressureincontinuousreciprocatingmotionoftheload,itsloadandworkingconditionswereappalling.Duringthedesignprocessofthepistonwillbedesignedtoensurelong-termstabilityoftheworkpiston.Thedesignoftheworkdonebyabriefintroductionasfollows:DieselEnginePiston180Creasonableprocessingtechnologyisimportant,theroleofpartsandtechnologyprogramanalysis,preparationofroughformandprocessmanufacturingline,throughtheanalysis,comparison,useoftherelativeconcentrationofprocessingprograms,andultimatelymorereasonabletodeterminethemechanicallineprocessing.Thedevelopmentprocessofroughlinethemainconsideration,finishingarrangements,choiceofprocessingmethods,centralizedanddecentralizedprocesses,suchasprocessingtheorderrequirements.Thendeterminetheallowance,processsize,aftertheanalysisofthecharacteristicsoftheprocess,selecttheappropriateprocessingequipmentandtechnicalequipment.Calculatedlook-uptabletodeterminethenextmajorpistoncuttingprocessandthemappingofprocessescard,thedesignofthefinalfixture.Fixturedesign,itisnecessarytotakevariousaspectsintoaccount,thestrictrequirementsofthefixtureadirectimpactonthesurfaceoftheworkpieceprocessingpositionaccuracy.Therefore,themachinetooldesignfixturedesignisanimportanttaskistheprocessingofoneofthemostactive.Duringthegraduationprojectinaspeciallydesignedpositioningaccuracy,simplestructureandeasy-to-useprecisionpinholeboringjig.Keywords:Piston；Technology；processingequipment；cutting；FixtureAnytypeofmachinethatobtainsmechanicalenergydirectlyfromtheexpenditureofthechemicalenergyoffuelburnedinacombustionchamberthatisanintegralpartoftheengine.Fourprincipaltypesofinternal-combustionenginesareingeneraluse:theOtto-cycleengine,thedieselengine,therotaryengine,andthegasturbine.Forthevarioustypesofenginesemployingtheprincipleofjetpropulsion,seeJetPropulsion；Rocket.TheOtto-cycleengine,namedafteritsinventor,theGermantechnicianNikolausAugustOtto,isthefamiliargasolineengineusedinautomobilesandairplanes；thedieselengine,namedaftertheFrench-bornGermanengineerRudolfChristianKarlDiesel,operatesonadifferentprincipleandusuallyusesoilasafuel.Itisemployedinelectric-generatingandmarine-powerplants,intrucksandbuses,andinsomeautomobiles.BothOtto-cycleanddieselenginesaremanufacturedin无锡太湖学院2009届本科生毕业设计（论文）翻译2two-strokeandfour-strokecyclemodels.TheessentialpartsofOtto-cycleanddieselenginesarethesame.Thecombustionchamberconsistsofacylinder,usuallyfixed,thatisclosedatoneendandinwhichaclose-fittingpistonslides.Thein-and-outmotionofthepistonvariesthevolumeofthechamberbetweentheinnerfaceofthepistonandtheclosedendofthecylinder.Theouterfaceofthepistonisattachedtoacrankshaftbyaconnectingrod.Thecrankshafttransformsthereciprocatingmotionofthepistonintorotarymotion.Inmulticylinderedenginesthecrankshafthasoneoffsetportion,calledacrankpin,foreachconnectingrod,sothatthepowerfromeachcylinderisappliedtothecrankshaftattheappropriatepointinitsrotation.Crankshaftshaveheavyflywheelsandcounterweights,whichbytheirinertiaminimizeirregularityinthemotionoftheshaft.Anenginemayhavefrom1toasmanyas28cylinders.Thefuelsupplysystemofaninternal-combustionengineconsistsofatank,afuelpump,andadeviceforvaporizingoratomizingtheliquidfuel.InOtto-cycleenginesthisdeviceiseitheracarburetoror,morerecently,afuel-injectionsystem.Inmostengineswithacarburetor,vaporizedfuelisconveyedtothecylindersthroughabranchedpipecalledtheintakemanifoldand,inmanyengines,asimilarexhaustmanifoldisprovidedtocarryoffthegasesproducedbycombustion.Thefuelisadmittedtoeachcylinderandthewastegasesexhaustedthroughmechanicallyoperatedpoppetvalvesorsleevevalves.Thevalvesarenormallyheldclosedbythepressureofspringsandareopenedatthepropertimeduringtheoperatingcyclebycamsonarotatingcamshaftthatisgearedtothecrankshaft.Bythe1980smoresophisticatedfuel-injectionsystems,alsousedindieselengines,hadlargelyreplacedthistraditionalmethodofsupplyingthepropermixofairandfuel.Inengineswithfuelinjection,amechanicallyorelectronicallycontrolledmonitoringsysteminjectstheappropriateamountofgasdirectlyintothecylinderorinletvalveattheappropriatetime.Thegasvaporizesasitentersthecylinder.Thissystemismorefuelefficientthanthecarburetorandproduceslesspollution.Inallenginessomemeansofignitingthefuelinthecylindermustbeprovided.Forexample,theignitionsystemofOtto-cycleenginesdescribedbelowconsistsofasourceoflow-voltage,direct-currentelectricitythatisconnectedtotheprimaryofatransformercalledanignitioncoil.Thecurrentisinterruptedmanytimesasecondbyanautomaticswitchcalledthetimer.Thepulsationsofthecurrentintheprimaryinduceapulsating,high-voltagecurrentinthesecondary.Thehigh-voltagecurrentisledtoeachcylinderinturnbyarotaryswitchcalledthedistributor.Theactualignitiondeviceisthesparkplug,aninsulatedconductorsetinthewallortopofeachcylinder.Attheinnerendofthesparkplugisasmallgapbetween无锡太湖学院2009届本科生毕业设计（论文）翻译3twowires.Thehigh-voltagecurrentarcsacrossthisgap,yieldingthesparkthatignitesthefuelmixtureinthecylinder.Becauseoftheheatofcombustion,allenginesmustbeequippedwithsometypeofcoolingsystem.Someaircraftandautomobileengines,smallstationaryengines,andoutboardmotorsforboatsarecooledbyair.Inthissystemtheoutsidesurfacesofthecylinderareshapedinaseriesofradiatingfinswithalargeareaofmetaltoradiateheatfromthecylinder.Otherenginesarewater-cooledandhavetheircylindersenclosedinanexternalwaterjacket.Inautomobiles,wateriscirculatedthroughthejacketbymeansofawaterpumpandcooledbypassingthroughthefinnedcoilsofaradiator.Someautomobileenginesarealsoair-cooled,andinmarineenginesseawaterisusedforcooling.Unlikesteamenginesandturbines,internal-combustionenginesdevelopnotorquewhenstarting,andthereforeprovisionmustbemadeforturningthecrankshaftsothatthecycleofoperationcanbegin.Automobileenginesarenormallystartedbymeansofanelectricmotororstarterthatisgearedtothecrankshaftwithaclutchthatautomaticallydisengagesthemotoraftertheenginehasstarted.Smallenginesaresometimesstartedmanuallybyturningthecrankshaftwithacrankorbypullingaropewoundseveraltimesaroundtheflywheel.Methodsofstartinglargeenginesincludetheinertiastarter,whichconsistsofaflywheelthatisrotatedbyhandorbymeansofanelectricmotoruntilitskineticenergyissufficienttoturnthecrankshaft,andtheexplosivestarter,whichemploystheexplosionofablankcartridgetodriveaturbinewheelthatiscoupledtotheengine.Theinertiaandexplosivestartersarechieflyusedtostartairplaneengines.TheordinaryOtto-cycleengineisafour-strokeengine；thatis,inacompletepowercycle,itspistonsmakefourstrokes,twotowardthehead(closedhead)ofthecylinderandtwoawayfromthehead.Duringthefirststrokeofthecycle,thepistonmovesawayfromthecylinderheadwhilesimultaneouslytheintakevalveisopened.Themotionofthepistonduringthisstrokesucksaquantityofafuelandairmixtureintothecombustionchamber.Duringthenextstroke,thepistonmovestowardthecylinderheadandcompressesthefuelmixtureinthecombustionchamber.Atthemomentwhenthepistonreachestheendofthisstrokeandthevolumeofthecombustionchamberisataminimum,thefuelmixtureisignitedbythesparkplugandburns,expandingandexertingapressureonthepiston,whichisthendrivenawayfromthecylinderheadinthethirdstroke.Duringthefinalstroke,theexhaustvalveisopenedandthepistonmovestowardthecylinderhead,drivingtheexhaustgasesoutofthecombustionchamberandleavingthecylinderreadytorepeatthecycle.TheefficiencyofamodernOtto-cycleengineislimitedbyanumberoffactors,includinglossesbycoolingandbyfriction.Ingeneral,theefficiencyofsuchenginesis无锡太湖学院2009届本科生毕业设计（论文）翻译4determinedbythecompressionratiooftheengine.Thecompressionratio(theratiobetweenthemaximumandminimumvolumesofthecombustionchamber)isusuallyabout8to1or10to1inmostmodernOtto-cycleengines.Highercompressionratios,uptoabout15to1,witharesultingincreaseofefficiency,arepossiblewiththeuseofhigh-octaneantiknockfuels.TheefficienciesofgoodmodernOtto-cycleenginesrangebetween20and25percentinotherwords,onlythispercentageoftheheatenergyofthefuelistransformedintomechanicalenergyTheoretically,thedieselcyclediffersfromtheOttocycleinthatcombustiontakesplaceatconstantvolumeratherthanatconstantpressure.Mostdieselsarealsofour-strokeenginesbuttheyoperatedifferentlythanthefour-strokeOtto-cycleengines.Thefirst,orsuction,strokedrawsair,butnofuel,intothecombustionchamberthroughanintakevalve.Onthesecond,orcompression,stroketheairiscompressedtoasmallfractionofitsformervolumeandisheatedtoapproximately440C(approximately820F)bythiscompression.Attheendofthecompressionstroke,vaporizedfuelisinjectedintothecombustionchamberandburnsinstantlybecauseofthehightemperatureoftheairinthechamber.Somedieselshaveauxiliaryelectricalignitionsystemstoignitethefuelwhentheenginestartsanduntilitwarmsup.Thiscombustiondrivesthepistonbackonthethird,orpower,strokeofthecycle.Thefourthstroke,asintheOtto-cycleengine,isanexhauststroke.Theefficiencyofthedieselengine,whichisingeneralgovernedbythesamefactorsthatcontroltheefficiencyofOtto-cycleengines,isinherentlygreaterthanthatofanyOtto-cycl