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外文翻译--柴油发动机工作原理.doc

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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,andinanotherpartoftheworkcycleofthecombustiongasmixturewithinthecylindersothepistontopsurfaceexpansionhighpressureabout116120Kgf/cm2underhightemperatureabout569°Cgasrole,andthepressurethroughthepistonpin,connectingrodtothecrankshaft.Canbeseenthatthepistonisalongtimeunderhightemperatureandhighpressureincontinuousreciprocatingmotionoftheload,itsloadandworkingconditionswereappalling.Duringthedesignprocessofthepistonwillbedesignedtoensurelongtermstabilityoftheworkpiston.ThedesignoftheworkdonebyabriefintroductionasfollowsDieselEnginePiston180Creasonableprocessingtechnologyisimportant,theroleofpartsandtechnologyprogramanalysis,preparationofroughformandprocessmanufacturingline,throughtheanalysis,comparison,useoftherelativeconcentrationofprocessingprograms,andultimatelymorereasonabletodeterminethemechanicallineprocessing.Thedevelopmentprocessofroughlinethemainconsideration,finishingarrangements,choiceofprocessingmethods,centralizedanddecentralizedprocesses,suchasprocessingtheorderrequirements.Thendeterminetheallowance,processsize,aftertheanalysisofthecharacteristicsoftheprocess,selecttheappropriateprocessingequipmentandtechnicalequipment.Calculatedlookuptabletodeterminethenextmajorpistoncuttingprocessandthemappingofprocessescard,thedesignofthefinalfixture.Fixturedesign,itisnecessarytotakevariousaspectsintoaccount,thestrictrequirementsofthefixtureadirectimpactonthesurfaceoftheworkpieceprocessingpositionaccuracy.Therefore,themachinetooldesignfixturedesignisanimportanttaskistheprocessingofoneofthemostactive.Duringthegraduationprojectinaspeciallydesignedpositioningaccuracy,simplestructureandeasytouseprecisionpinholeboringjig.KeywordsPistonTechnologyprocessingequipmentcuttingFixtureAnytypeofmachinethatobtainsmechanicalenergydirectlyfromtheexpenditureofthechemicalenergyoffuelburnedinacombustionchamberthatisanintegralpartoftheengine.FourprincipaltypesofinternalcombustionenginesareingeneralusetheOttocycleengine,thedieselengine,therotaryengine,andthegasturbine.Forthevarioustypesofenginesemployingtheprincipleofjetpropulsion,seeJetPropulsionRocket.TheOttocycleengine,namedafteritsinventor,theGermantechnicianNikolausAugustOtto,isthefamiliargasolineengineusedinautomobilesandairplanesthedieselengine,namedaftertheFrenchbornGermanengineerRudolfChristianKarlDiesel,operatesonadifferentprincipleandusuallyusesoilasafuel.Itisemployedinelectricgeneratingandmarinepowerplants,intrucksandbuses,andinsomeautomobiles.BothOttocycleanddieselenginesaremanufacturedin无锡太湖学院2009届本科生毕业设计(论文)翻译2twostrokeandfourstrokecyclemodels.TheessentialpartsofOttocycleanddieselenginesarethesame.Thecombustionchamberconsistsofacylinder,usuallyfixed,thatisclosedatoneendandinwhichaclosefittingpistonslides.Theinandoutmotionofthepistonvariesthevolumeofthechamberbetweentheinnerfaceofthepistonandtheclosedendofthecylinder.Theouterfaceofthepistonisattachedtoacrankshaftbyaconnectingrod.Thecrankshafttransformsthereciprocatingmotionofthepistonintorotarymotion.Inmulticylinderedenginesthecrankshafthasoneoffsetportion,calledacrankpin,foreachconnectingrod,sothatthepowerfromeachcylinderisappliedtothecrankshaftattheappropriatepointinitsrotation.Crankshaftshaveheavyflywheelsandcounterweights,whichbytheirinertiaminimizeirregularityinthemotionoftheshaft.Anenginemayhavefrom1toasmanyas28cylinders.Thefuelsupplysystemofaninternalcombustionengineconsistsofatank,afuelpump,andadeviceforvaporizingoratomizingtheliquidfuel.InOttocycleenginesthisdeviceiseitheracarburetoror,morerecently,afuelinjectionsystem.Inmostengineswithacarburetor,vaporizedfuelisconveyedtothecylindersthroughabranchedpipecalledtheintakemanifoldand,inmanyengines,asimilarexhaustmanifoldisprovidedtocarryoffthegasesproducedbycombustion.Thefuelisadmittedtoeachcylinderandthewastegasesexhaustedthroughmechanicallyoperatedpoppetvalvesorsleevevalves.Thevalvesarenormallyheldclosedbythepressureofspringsandareopenedatthepropertimeduringtheoperatingcyclebycamsonarotatingcamshaftthatisgearedtothecrankshaft.Bythe1980smoresophisticatedfuelinjectionsystems,alsousedindieselengines,hadlargelyreplacedthistraditionalmethodofsupplyingthepropermixofairandfuel.Inengineswithfuelinjection,amechanicallyorelectronicallycontrolledmonitoringsysteminjectstheappropriateamountofgasdirectlyintothecylinderorinletvalveattheappropriatetime.Thegasvaporizesasitentersthecylinder.Thissystemismorefuelefficientthanthecarburetorandproduceslesspollution.Inallenginessomemeansofignitingthefuelinthecylindermustbeprovided.Forexample,theignitionsystemofOttocycleenginesdescribedbelowconsistsofasourceoflowvoltage,directcurrentelectricitythatisconnectedtotheprimaryofatransformercalledanignitioncoil.Thecurrentisinterruptedmanytimesasecondbyanautomaticswitchcalledthetimer.Thepulsationsofthecurrentintheprimaryinduceapulsating,highvoltagecurrentinthesecondary.Thehighvoltagecurrentisledtoeachcylinderinturnbyarotaryswitchcalledthedistributor.Theactualignitiondeviceisthesparkplug,aninsulatedconductorsetinthewallortopofeachcylinder.Attheinnerendofthesparkplugisasmallgapbetween无锡太湖学院2009届本科生毕业设计(论文)翻译3twowires.Thehighvoltagecurrentarcsacrossthisgap,yieldingthesparkthatignitesthefuelmixtureinthecylinder.Becauseoftheheatofcombustion,allenginesmustbeequippedwithsometypeofcoolingsystem.Someaircraftandautomobileengines,smallstationaryengines,andoutboardmotorsforboatsarecooledbyair.Inthissystemtheoutsidesurfacesofthecylinderareshapedinaseriesofradiatingfinswithalargeareaofmetaltoradiateheatfromthecylinder.Otherenginesarewatercooledandhavetheircylindersenclosedinanexternalwaterjacket.Inautomobiles,wateriscirculatedthroughthejacketbymeansofawaterpumpandcooledbypassingthroughthefinnedcoilsofaradiator.Someautomobileenginesarealsoaircooled,andinmarineenginesseawaterisusedforcooling.Unlikesteamenginesandturbines,internalcombustionenginesdevelopnotorquewhenstarting,andthereforeprovisionmustbemadeforturningthecrankshaftsothatthecycleofoperationcanbegin.Automobileenginesarenormallystartedbymeansofanelectricmotororstarterthatisgearedtothecrankshaftwithaclutchthatautomaticallydisengagesthemotoraftertheenginehasstarted.Smallenginesaresometimesstartedmanuallybyturningthecrankshaftwithacrankorbypullingaropewoundseveraltimesaroundtheflywheel.Methodsofstartinglargeenginesincludetheinertiastarter,whichconsistsofaflywheelthatisrotatedbyhandorbymeansofanelectricmotoruntilitskineticenergyissufficienttoturnthecrankshaft,andtheexplosivestarter,whichemploystheexplosionofablankcartridgetodriveaturbinewheelthatiscoupledtotheengine.Theinertiaandexplosivestartersarechieflyusedtostartairplaneengines.TheordinaryOttocycleengineisafourstrokeenginethatis,inacompletepowercycle,itspistonsmakefourstrokes,twotowardtheheadclosedheadofthecylinderandtwoawayfromthehead.Duringthefirststrokeofthecycle,thepistonmovesawayfromthecylinderheadwhilesimultaneouslytheintakevalveisopened.Themotionofthepistonduringthisstrokesucksaquantityofafuelandairmixtureintothecombustionchamber.Duringthenextstroke,thepistonmovestowardthecylinderheadandcompressesthefuelmixtureinthecombustionchamber.Atthemomentwhenthepistonreachestheendofthisstrokeandthevolumeofthecombustionchamberisataminimum,thefuelmixtureisignitedbythesparkplugandburns,expandingandexertingapressureonthepiston,whichisthendrivenawayfromthecylinderheadinthethirdstroke.Duringthefinalstroke,theexhaustvalveisopenedandthepistonmovestowardthecylinderhead,drivingtheexhaustgasesoutofthecombustionchamberandleavingthecylinderreadytorepeatthecycle.TheefficiencyofamodernOttocycleengineislimitedbyanumberoffactors,includinglossesbycoolingandbyfriction.Ingeneral,theefficiencyofsuchenginesis无锡太湖学院2009届本科生毕业设计(论文)翻译4determinedbythecompressionratiooftheengine.Thecompressionratiotheratiobetweenthemaximumandminimumvolumesofthecombustionchamberisusuallyabout8to1or10to1inmostmodernOttocycleengines.Highercompressionratios,uptoabout15to1,witharesultingincreaseofefficiency,arepossiblewiththeuseofhighoctaneantiknockfuels.TheefficienciesofgoodmodernOttocycleenginesrangebetween20and25percentinotherwords,onlythispercentageoftheheatenergyofthefuelistransformedintomechanicalenergyTheoretically,thedieselcyclediffersfromtheOttocycleinthatcombustiontakesplaceatconstantvolumeratherthanatconstantpressure.MostdieselsarealsofourstrokeenginesbuttheyoperatedifferentlythanthefourstrokeOttocycleengines.Thefirst,orsuction,strokedrawsair,butnofuel,intothecombustionchamberthroughanintakevalve.Onthesecond,orcompression,stroketheairiscompressedtoasmallfractionofitsformervolumeandisheatedtoapproximately440°Capproximately820°Fbythiscompression.Attheendofthecompressionstroke,vaporizedfuelisinjectedintothecombustionchamberandburnsinstantlybecauseofthehightemperatureoftheairinthechamber.Somedieselshaveauxiliaryelectricalignitionsystemstoignitethefuelwhentheenginestartsanduntilitwarmsup.Thiscombustiondrivesthepistonbackonthethird,orpower,strokeofthecycle.Thefourthstroke,asintheOttocycleengine,isanexhauststroke.Theefficiencyofthedieselengine,whichisingeneralgovernedbythesamefactorsthatcontroltheefficiencyofOttocycleengines,isinherentlygreaterthanthatofanyOttocycleengineandinactualenginestodayisslightlymorethan40percent.Dieselsare,ingeneral,slowspeedengineswithcrankshaftspeedsof100to750revolutionsperminuterpmascomparedto2500to5000rpmfortypicalOttocycleengines.Sometypesofdiesel,however,havespeedsupto2000rpm.Becausedieselsusecompressionratiosof14ormoreto1,theyaregenerallymoreheavilybuiltthanOttocycleengines,butthisdisadvantageiscounterbalancedbytheirgreaterefficiencyandthefactthattheycanbeoperatedonlessexpensivefueloils.BysuitabledesignitispossibletooperateanOttocycleordieselasatwostrokeortwocycleenginewithapowerstrokeeveryotherstrokeofthepistoninsteadofonceeveryfourstrokes.Thepowerofatwostrokeengineisusuallydoublethatofafourstrokeengineofcomparablesize.Thegeneralprincipleofthetwostrokeengineistoshortentheperiodsinwhichfuelisintroducedtothecombustionchamberandinwhichthespentgasesareexhaustedtoasmallfractionofthedurationofastrokeinsteadofallowingeachoftheseoperationstooccupyafullstroke.Inthesimplesttypeoftwostrokeengine,thepoppetvalvesarereplacedbysleeve

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