柴油机燃油喷射 毕业论文外文翻译

DieselFuelInjectionThepurposeofthefuelinjectionsystemistodeliverfuelintoenginecylinders,whilepreciselycontrollingtheinjectiontiming,fuelatomization,andotherparameters.Thetypesofinjectionsystemsincludepump-line-nozzle,unitinjector,andcommonrail.Moderninjectionsystemsreachveryhighinjectionpressures,andutilizesophisticatedelectroniccontrolmethods.1.IntroductionTheperformanceofdieselenginesisheavilyinfluencedbytheirinjectionsystemdesign.Infact,thenotableadvancesachievedindieselenginesresulteddirectlyfromsuperiorfuelinjectionsystemdesigns.Whilethemainpurposeofthesystemistodeliverfueltothecylindersofdieselengine,itishowisdeliveredthatmakesthedifferenceperformance,emissions,andnoisecharacteristics.Unlikeitsspark-ignitedenginecounterpart,theinjectionsystemdeliversfuelunderextremelyhighinjectionpressures.Thisimpliesthatthesystemcomponentdesignsandmaterialsshouldbeselectedtowithstandhigherstresses,whilestillperformingforextendeddurationsmatchingtheengine'sdurabilitytargets.Greatermanufacturingprecisionandtighttolerancesarealsorequiredforthesystemefficientfunction.Inadditiontoexpensivematerialsandmanufacturingcosts,injectionsystemsarecharacterizedbymoreintricatecontrolrequirements.Allthesefeaturesupasystemwhosecostrepresentasmuchas30%ofthetotalcostoftheThisandthefollowingpaperswillreviewthebasicdieselinjectionsystemanditscomponents,thevarioustypesofinjectionsystems,andmeteranddeliverfuelintothecylindersofaengine.Themechanicalfunctionofthesesystemswillbedescribedwithemphasisontheirformationrole.Variousinjectiontimingandmeteringschemeswillbedescribed.anyspecializedtermsareusedtodescribethecomponentsandtheoperationoffuelinjectionsystems.Thefollowingaredefinitionsofselected,morecommonterms.ozzlereferstothepartofnozzlebody/needleassemblywhichinterfaceswiththecombustionchamberoftheengine.TermslikeP-Type,M-Type,ornozzlerefertostandardizeddimensionsofnozzleparameters,asperISOspecifications.Nozzleholderorinjectorbodyreferstothepartnozzleismountedon.Inconventionalinjectionthispartservedthemountingandnozzleneedlespringpreloadingpurpose.Incommonrailsystem,itcontainsthemainfunctionalparts:theservo-hydraulicandthehydraulicactuator(electromagneticorpiezoelectric).Injectorcommonlytothenozzleholderandnozzleassembly.Rateofinjectionistheofoutofthenozzle,typicallyshownoveratimeaxis.Startofinjectionandendofinjectionrefertothestartendofflowfromthenozzle,oftenreferredtowithreferencetotheenginecrankangle.Openingrateandclosingraterefersthegradientsintherateinjectionduringneedleopeningandrespectively.Injectionisnotusedconsistentlyintheliterature.Itrefertopressureinthehydraulicsystemforsystems,ortothemaximumduringaninjection(peakinjectionpressure)inconventionalsystems.2.PurposesofFuelInjectionSystemAsstatedthemainpurposeofthefuelinjectionsystemistodeliverfuelintothecylindersofanWhilethisbethepurposethesystem,twospecificobjectivesofafundamentalimportancemaybedescribedbythefollowingfunctions:Timelyoftheintothecylinder,thatinjectiontiminganditscontrol.Deliveryofanaccurateamountfueltomeetpowerrequirement,thatis,injectionmeteringanditscontrol.Todeliveranaccuratelyamountoffuelatthepropertimetoachievegoodcombustion.Howdeliveredmixeswiththeinductedairisofmajorimportance.Therefore,fuelatomization,i.e.,howsmallparticlesizeisandhowdisperseditisincylinder,shouldbeaprimarydesignobjectiveasuccessfuldieselfuelinjectionsystem.Yet,evenproperlyatomized,accuratelymetered,andwelltimedfueldeliverymaynotprovidethedesiredcombustionefficiency.Anotherimportantparameterinthisrespectisqualityofthemixture(fuelandair).Whilegoodatomizationgoestowardimprovingcombustionefficiency,howwelltheavailableairisusedisalsoanindicatorofcombustionefficiency.Toachievethisobjective,betterairutilizationmustbeachieved.parametercanbeaccomplishedthroughacombinationoffuelpenetrationintothedenseairthatiscompressedincylinder,andequallydividingthetotalfuelamongcylindersofanengine.TheprimarypurposesofthedieselfuelinjectionsystemaregraphicallyrepresentedinFigure6.Figure6FunctionsofDieselFuelInjectionSystemToaccomplishdescribedfunctionsisnosmalltask,andtodoiteffectivelyrequiresthecollectiveexperienceofmanyexpertsspecializedinthedisciplinesofmaterials,mechanicaldesign,hydraulicsandfluiddynamics,aswellascombustionsystems.Asmorelimitswereimposedonemissionsdieselengines,andpressureswerefeltfromcustomersforbetterperformance,theneedforadditionalfuelinjectionsystemfunctionsbecameapparent.Indeedthemoderndieselinjectionsystemthetasksofmetering,andatomizingaswellascontributetogoodairandfuelmixing.Inaddition,experiencegainedsincethemid-1970’shasshownschedulingofthemeteredfuelintothecylinderisimportanttotheperformance,emissions,andnoisecharacteristicsofthecombustionprocess.Ageneraltermdescribingtheschedulingofinjectedfuelisrateshaping.Yet,modernsystemsonlyconcernedwithhowmuchfuelisdeliveredpercrankangledegree,butalsowiththenumberofinjectionspercombustioncycle.3.TypesofDieselFuelInjectionSystemsDieselfuelinjectionsystemscanbeclassifiedintothreecategories,asfollows:Pump-Line-NozzleUnitInjectorCommonRailP-L-NconfigurationsandcomponentsarediscussedinPump-Line-NozzleInjectionSystemFigure7.Pump-Line-NozzleSystemPrinciplePump-Line-NozzleSystemPrinciplePump-line-nozzle(P-L-N)isafuelsystemusingcentralinjectionpumpdrivenoffthegeartrain,Figure7.Theinjectionpumpfeedsseparateinjectionnozzlesinthecylinderheadaboveeachcylinder.Lines—whichmustbeofexactlyequallengthlinkthepumpwithnozzles.Inthecaseofthein-linepump,thepumpincorporatesnumberofseparateplunger/barrelpumpingelements(suchasthatshowninFigureservingoneinjector.Eachnozzleincorporatesaneedlevalveandtheorificeswhichprovidefuelatomization.TheP-L-Nfuelsystemusedtobecommontypeofinjection,dominatingmostdieselengineapplications.Inadditiontothein-linepumpdesign,whereeachinjectorisfedbyaseparatepumpingelement,otherconfigurationsthathavebeendeveloped,includingthedistributor/rotarypump.BothtypesofpumpsystemstheircomponentsarediscussedinmoredetailinthePump-Line-NozzleInjectionSystempaper.MoredetailsareavailableinCommonRailFuelInjection.Thetotalcommonrailsystemincludesapressuredrawsfuelfromthetankandfeedsittothepressurepump.Highpressurefueldeliveredintothemaybringalongpressurepulsations,thereforethevolumeofthecommonrailshouldbedesignedtodampenthosepulsations.Thesepulsationsresultfromthedeliverycharacteristicsofthemulti-plungersradialfuelpump.Drivingthepumpatenginespeedincreasesfuelpumpingandimprovesthepotentialforhighinjectionpressure.offuelmeteringandinjectiontimingissimilartothatinthein-linepumpandunitinjectorsystems.Inspiteoftheavailabilityofthesedesirablefeaturesincommonrailsystems,itneedsbeemphasizedthatsuchsystemscouldnotattaintheirpotentialwithoutthehelpfromelectroniccontrols.Inelectronicswerealloffuelinjectionsystemstoexpandtheircapabilitiesandtheirperformance.Foreachoftheaboveinjectionsystemcategoriesthereareanumberofsub-categoriesthatwilldetailedinfollowingpapers.However,therearesomegeneralizedthatcanbemadeatthisstagetofurtherclarifyhowquicklythesethreeverygeneralcategoriescanoutintomanyanddistinctdesigns.Forinstance,pump-line-nozzlesystemsincludein-line,distributor(rotary),aswellaspumps.Notonlycouldwedifferentiatethemassuch,butwecanalsoseparatebetweenthemonthebasisofwhethertheyaremechanically-orelectronically-controlled.Similarly,unitinjectorscanbemechanically-orelectronically-controlled.Unitinjectorsystemscanalsobedesignedtodeliverextremelyhighinjectionpressures,inwhichcasemayfeaturemechanicalintensifiersinofplungershavingtwodifferentdiameters.TheymayalsobeactuatedbybruteforceimpartedtotopoftheinjectorbyalargecamsuchtheCumminspressure-timecontrolled(PT)system.Thecommonrailcategoryenjoysasimilarvarietyofdesigndetails.Theevolutionofthedieselinjectionsystemsfromtheoldmechanically-controlledP-L-Ndesignstothemodernelectronically-controlledinjectorandaccumulatordesigns,driveningeneralbytheneedachievingtighterinjectioncontrolandloweremissions,followsonedistincttrend:increasedinjectionpressures.Infact,thistrendcontinuedthroughthelastForheavy-applications,itacceleratedin1970’stomeetthedemandforcleaner,aswellasmorefuelefficientengines.Eventuallythehighspeed,passengercarmarketadoptedthesamephilosophy,andevenitstartedadecadeaftertheheavy-dutyapplications,bothlight-dutyheavy-dutyapplicationshavenowsimilarinjectionpressures.4.ElectronicControlinFuelInjectionOverviewTheneedtomeetemissionregulationswasoneofmostimportant—notthemostimportant—reasonformodernizingthedieselfuelinjectionsystem.demandforbetterengineresponseanddriveabilityalsoplayedamajorroleinadvancingthefuelsystem’s-of-the-art.Dieselenginedesignersandbuilderswerenotjustsatisfiedwithitssuperiorfueleconomy,butsoughttocontinuetoimproveittomaintainitsleadoveritsNotonlythegoaltoimproveitsfuelstanding,buttoachievethisobjectivewhilealsomeetingthetoughemissionregulationsthatwereimposedthe1980’s1990’s,aswellasearlyinthe21Asalreadymentioned,sometheearlygainsintheevolutionofthemoderndieselinjectionsystemwererealizedthroughincreasinginjectionpressures.However,enginedesignersfelttheirhandsweretiedandwereunabletomakeothergainsuntilwereabletointroduceelectroniccontrolintotheinjectionsystem.IntroducingthistechnologymadeotheradvanceseasiertoItwastocustomizetorqueoutputsfromthesamebasetomeetthedemandsseveralapplicationsintheheavy-dutymarket.Itwaseasytoincludemanyvalueaddedfeaturessuchaslimitingmaximumroadspeedforfleetswherefuelconsumptionisdirectlyrelatedtodrivinghabits.Forthefirsttimeinjectedfuelquantitywastrimmedaccordingtofueltemperatureforconsistentpowerregardlessoffueltemperature,withincertainlimits.Electronicsbroughtalongthepromiseofreducedcostthroughsimplifyingmanyofthefunctionsotherwiseprovidedcumbersomemechanicaldevices,andallowedimplementationoffull-authorityparametercontrolstrategies.Forinstance,drive-by-wiresystemallowedtheimplementationoflow-orno-smokestrategiesversussystemswheretheinjectionwassolidlyconnectedtotheacceleratorIntostrategies,electroniccontrolsfacilitatedflexibilityininjectiontimingandmeteringcontrol,andreducedcycle-to-cycle,andcylinder-to-cylindervariability.柴油机燃油射燃油喷射系统的目的是将燃油输送到发动机缸体内时精确地控制喷射正时油化和其他参数喷系统的主要型包括--嘴单体泵和共轨现喷射系统可达到很高的喷射压力，使用的是复杂的电子控制系统。1.介绍柴油发动机的性能受喷射系统设计的影响很大际上油发动机的先进性直接体现在高级喷射系统的设计上射统的主要目的是将燃油输送给柴油发动机的缸体样送燃油才能使发动机的性能排和噪音等特性不象点燃式发动机柴喷射系统可在很高的喷射压力下输送燃油意着系统零部件的设计和材料应当选择能抵抗高压力时能提高发动机可靠性指标为满系统功效需要较高的生产精度和较小的公差除了昂贵的材料和生产成本柴油发动机射系统以具有更复杂的控制要求为特征有这些特点组成系统，其成本可占到发动机总成本3。下面将回顾基本的柴油喷射系统和与它相关的附件及其他各种类型的喷射系统有他们如何测量和输送燃油给柴油机的缸体的系统的机械功能的重点在于混合物的形成。各种不同的喷射正时和测量策略将被介绍。许多专用术语用于描述零部件和燃油喷射系统的运行是选得更为普及的一些术语。喷嘴是指喷嘴壳体和针的装配体，他与发动机的燃烧室相接触。P型、型S型喷嘴之累的术语是指喷嘴参数的标准尺寸，ISO准规范。喷嘴支撑或喷射器壳体是指安放喷嘴的部件传统的喷射系统中个部件主要用于安放喷嘴和预加载荷的喷嘴针阀弹簧共轨系统中它含主要的功能部件伺液压电路和液压激励（电磁或压电）。喷射器通常是指喷嘴支撑和喷嘴的组合体。喷射率是燃油出喷嘴的质量流量型显示在间坐标上射的开始和结束是指柴油从喷嘴出来的开始和结束时刻，经常参照发动机的曲轴转角。开启和关闭速率分别指针阀开启和关闭之间喷射率的梯度压力并不是一贯使用在文献中是支持共轨系统的压系统的平均压力或传统系统中喷射过程的最大压峰值压力）2.燃油喷射系统的作用如上所述燃油喷射系统的主要用是将燃油输送进发动机的缸体这系统的一般作用，两个特别的目的如下所述：燃油进缸体的时刻介绍，即喷射正时和它的控制。输送精确的燃油量以满足功率的需要，即喷射计量和它的控制。然而它然不足以满足精确测燃油合适的时刻进行输送从而达到好的燃烧效果。怎样将燃油混合物，含有吸进的空气，输送缸体是主要的。因此，燃油雾化，无论燃油颗粒尺寸多么小以及在缸内如何分散成功的柴油喷射系统主要的设计指标然而一合适的雾化精确的计量和良好正时时刻可能也不会提供想要的燃烧效率外一个重要的参数就是混合物的质量（燃油和空气）。然而，雾化好对提高燃烧效率是有利的，还有所吸入的空气的质量也是高效燃烧的一个指标达到这个指标要高质量的空气这方面可通过压入汽缸中的空气中渗入进来的燃油的混合等分配在发动机汽缸内的燃油。柴油机燃油喷射系统的主要作用如下所示。图6柴油燃油喷射系统的功能要完成功能介绍是一个不小的任务需要许多专家集体的经验特在材料规范机械设计、液压和流体动力，还有燃烧系统等方面。由于柴油发动机的排放存在更多的限制，以及来自消费者对更好性能需求的压力附增喷射系统功能的需要明显了事实上现柴油喷射系统必须进行计量任务、正时、雾化和充分的空气燃油混合。此外，自二十世纪七十年代中期以来所获取的经验示进入缸体计量燃油的控制对于性能排放和燃烧过程的噪音特性是非常重要的燃油射控制的一般描述是速率修正然而现系统不仅仅关于每个曲轴转角的送油量，而且也涉及了每个燃烧循环的喷射次数。3.柴油机燃油喷射系统的分类