J2715Gasoline Fuel Injector Spray Measurement and Characterization中英对照原版08.docx
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J2715Gasoline Fuel Injector Spray Measurement and Characterization中英对照原版08.docx
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J2715GasolineFuelInjectorSprayMeasurementandCharacterization中英对照原版08
GasolineFuelInjectorSprayMeasurementandCharacterization
汽油燃油喷油器喷雾测量与特性
3.BASICSPRAYCHARACTERISTICSANDDEFINITIONS
基本的喷雾特性与定义
3.1IntroductiontoGasolineFuelSpray
汽油燃油喷雾的介绍
Theprimaryfunctionofthegasolinefuelinjectoristoaccuratelymetertherequiredamountoffuel.Anotherkeyfunction,however,istoatomizetheinjectedliquidfuel.Thetransformationoftheliquidstreamintoamyriadofsmallgasolinedropsdramaticallyincreasesthesurfaceareaoftheinjectedfuel,thusenhancingtherateofvaporization.Thetransienteventthatsimultaneouslymetersandatomizestheliquidgasolinemaybeconsideredasconcurrentsprayformationandpenetrationprocessesthatoccurontheorderofmilliseconds.Theresultantatomizationisapositivefactorintheportfuelinjectionapplication,butisanevenmorecriticalfactorforgasoline-directinjection,duetothefactthatforG-DI,theavailabletimeintervalbetweentheendofinjectionandignitionisverybrief.Themeandiameterofarepresentativesampleofthedeliveredgasolinedropsisastatisticalmetricthatisakeymeasureofgoodnessofthespraydeliveredbya
particularinjector.Asthemeandiameterbecomessmaller,thesurface-to-volumeratiooftheinjectedgasolineincreases,andthevaporizationrateincreasessubstantially.
汽油燃油喷油器的一个基本功能是精确计量需要的燃油量。
另一个关键的功能是将液态燃油喷射成雾状。
液流变成大量的小的汽油颗粒大大地增加了喷射燃油的表面积,加快燃油汽化速度。
液态汽油的计量和雾化两个同步瞬态事件可以看作以毫秒级时间发生的喷雾生成和渗透过程。
由于在GDI喷射结束和点火之间的有效时间间隔非常短,由此产生的燃油雾化是进气道燃油喷射应用的一个重要因素,更是汽油直接喷射应用的一个决定性因素。
输送的汽油油滴典型样本的平均直径是一个统计指标,是特定喷油器输送的喷雾效果好坏的关键测量指标。
如果平均直径变小,喷射的汽油的面容比就增大,汽化速率就大幅提高。
Therearemanysprayclassificationsinthefieldofgasolineinjection,buttheinitial,primaryclassificationishistoricallybasedupontheapplication.Thetwomajorgasolineapplicationsareportfuelinjection(PFI)andgasoline,direct,incylinderinjection(G-DI).ThisisillustratedinFigure1.Ingeneral,thePFIinjectorapplicationutilizesrelativelylowfuelpressuresoflessthan0.5MPa,andachievesameandropdiameterintherangefrom50to200micronsinthedeliveredspray,dependinguponthedesign.SAEJ1832referstoinjectorswithfuelpressurebelow1000kPaaslow-pressuregasolineinjectors.TheG-DIinjector,however,isrequiredtodeliverameandropdiameteroflessthan30micronsinordertosustaincombustion;therefore,extensivemeasuressuchasahighfuelpressure(5.0to20.0MPa)ortheintroductionofcompressedairaregenerallyrequired.
在汽油喷射领域有多种喷雾分类,但是最初的基本分类是以往基于应用的分类方法。
两个主要的汽油应用是进气道燃油喷射(PFI)和汽油缸内直接喷射(GDI)。
如图1所示。
一般来说,PFI喷油器应用使用相对较低的燃油压力,低于0.5MPa,在生成的喷雾中形成的平均油滴直径范围是50微米到200微米之间,与具体设计有关。
SAEJ1832中将低于1000KPa燃油压力喷油器称为低压汽油喷油器。
然而,GDI直接喷射喷油器要求生成的喷雾平均油滴直径小于30微米才能维持燃烧,因此,需要更广泛的测量,如高燃油压力(5.0到20.0MPa)或者引入压缩空气。
FIGURE1-MAJORCLASSIFICATIONOFSPRAYSFROMAUTOMOTIVEFUELINJECTORS
TypicalgeometricconfigurationsforbothaPFIapplicationandaG-DIapplicationareillustratedinFigure2.Ontherightinthisillustration,αdepictstheinjectormountinganglerelativetotheenginefiredeck,andβdepictsthesprayangleofthesprayplume.IntheportinjectorclassificationillustratedontheleftpanelinFigure2,thefuelinjectorispositionedtointroducethefuelsprayintotheintakeportupstreamoftheintakevalveorvalves.Thismaybeanywherewithinasignificantrangeofdistancesfromtheinjectortiptotherearfaceoftheintakevalve.Thisdistanceiscommonlyreferredtoasthe“targetingdistance”,andisakeyparameterintheoveralldesignofthecombustionsystem.ThePFIinjectorismostcommonlymountedintheintakemanifoldrunner,whichyieldstargetingdistancesof65to120mm.Somespecialapplicationssuchassuperchargingmayhavetheinjectormountedinthecylinderheadportionoftheintakerunner,withassociatedshortertargetingdistancesof40to65mm.Thisoption,andtheG-DIin-cylindermounting,generallyyieldelevatedinjectoroperatingtemperatures.Thetimingoftheportfuelinjectioneventinthevastmajorityofapplicationsoccurswhiletheintakevalveisclosed,andwithnomeanairflowintheport.Thisresultsfromtheobservedfactthatengine-outUBHC(unburnedhydrocarbon)emissionsaresignificantlyelevatedifinjectionintotheportoccursduringtheperiodwhentheintakevalveisopen.ThefuelsprayfromthePFIinjectornormallyrequiresfrom4to9millisecondstotraversethetargetingdistanceandtoimpacttherearfaceoftheintakevalve.Thisrearfaceisthemostcommon“target”forthefuelsprayaxis,whichisagainduetotheobservedfactthattheenginecombustionandemissioncharacteristicsarebothdegradedasgreateramountsofthefuelspraymassareallowedtocontacttheportwall.
PFI和GDI应用的典型几何结构如图2所示。
在右图中
表示喷油器相对发动机点火平面的安装角度,
表示喷雾的喷雾角。
在图2左边所示进气道喷油器类型中,燃油喷油器是在将燃油喷雾引入到进气阀的进气口上游的位置。
它的位置可以是在喷油器顶端到进气阀背面距离范围内的任何地方。
这个距离通常称为“目标距离”,而且是整个燃烧系统设计中的一个关键参数。
PFI喷油器通常安装在进气歧管,目标距离是65到120mm。
一些象增压压力一样特殊的应用可能要求喷油器安装在进气歧管的缸盖部分,另外有40到65mm的较短的目标距离。
一般这种选择和GDI缸内安装将具有提高喷油器工作温度的作用。
在大多数实际应用中,进气道燃油喷射事件发生在进气门关闭时刻,而且在气道里没有有效的空气流。
实际观察的结果是,如果在进气门打开期间在气道内进行喷射,发动机的未燃烧碳氢排放会严重增加。
通常要求PFI喷油器的燃油喷雾在4到9毫秒通过目标距离,与进气门背面发生碰撞。
这个气门的背面就是通常燃油喷雾轴线上的“目标”,同样实际观察表明当更多燃油喷雾的燃油量与进气道壁面接触时,发动机的燃烧和排放特性都将下降。
FIGURE2-SCHEMATICREPRESENTATIONSOFTHEPORTFUELINJECTION
ANDGASOLINE-DIRECTINJECTIONCLASSIFICATIONS
TheG-DIinjector,incontrast,introducesthefuelspraydirectlyintotheenginecylinder.ThisisdepictedschematicallyintherightpanelofFigure2.Asadirectconsequenceoftheverylimitedtimeavailableforpenetration,evaporationandmixing,thespraymust,outofnecessity,besignificantlymorebriefandofafineratomizationlevelthanthatfromaPFIinjector.TheG-DIinjectormaybeopenlessthan2millisecondsatlightloadoperatingconditions,andwillnormallyexhibitameandropsizethatisanorderofmagnitudesmallerthanthatofaPFIspray.Thetimescaleofthesprayeventisquitedifferentforthetwomainapplicationclassifications,withnearlyalloftheeventtimemarkerssuchasinjectoropening,sprayformation,pulseduration,penetration,vaporizationandinjectorclosingbeingtwotofourtimesfasterfordirectinjection.Thisis,ofcourse,forcedbythestringenttimingrequirementsforachievingstablecombustionwheninjectingdirectlyintothecombustionchamber.AsisthecaseforthemountingofPFIinjectors,anumberofoptionsexistforG-DIinjectors.Dependinguponthetypeofintendedcombustionsystem,thespraymaybeintentionallydirectedatthepistoncrown,ataspecialbowlinthepistoncrownoragainstorwiththein-cylinderairmotion.
相反,GDI的喷油器直接将燃油喷雾引入到发动机的汽缸。
如图2右图所示。
出于必要性,一个对渗透、蒸发和混合有效的非常有限时间,喷雾必须更短(简单),而且要比PFI喷油器有更好的雾化水平。
在小负荷工作条件下,GDI喷油器的打开时间可能小于2毫秒,而且通常体现出油滴的平均尺寸要比PFI喷雾小一个数量级。
从这两种主要的应用类型来看,喷雾事件的时间范围非常不同,对于直接喷射几乎所有事件的时间标注,如喷油器打开、喷雾生成、脉冲持续时间、渗透、蒸发和喷油器关闭等,都要快2到4倍。
当然,这是直接喷射到燃烧室时实现稳定燃烧对时间有严格要求的原因。
象PFI喷油器的安装情况一样,GDI喷油器的安装也有许多的选择。
根据燃烧系统的类型,喷雾可能故意直接喷射到活塞顶部、活塞顶部专门的凹坑、或者与缸内空气运动方向一致或者相反。
Forthetransientprocessesofsprayformation,penetrationanddissipation,thereareanumberofkeysprayfeaturesthatmaybereadilyidentified.ThesefeaturesareillustratedandidentifiedinFigure3.AlthoughthesprayfeaturesareillustratedschematicallyforaG-DIinjectorspray,nearlyallthoseshownexceptforthetoroidalvortexalsoexistintheportinjectionspray.Thus,eachclassificationmayhaveanearlysacsprayandalatermainspray,andmayhaveoneormoreafter-injections.
对喷雾生成、渗透和消散的瞬态过程,有一些关键喷雾特性可能比较容易识别出来。
图3说明了这些特性和它们的识别。
尽管图示说明了GDI喷油器喷雾的喷雾特性,但是在图中显示的特性中除了环形涡流以外,几乎所有特性在进气道喷射喷雾中也都存在。
每种类型可能都有一个早期的囊状喷雾和后期的主喷雾,而且可能还有一个或者多个后喷射。
FIGURE3-GEOMETRICCHARACTERISTICSOFATRANSIENTG-DISPRAY
ThisdocumentwilldetailtherecommendedpracticesforobtainingnumerouskeymetricsthatquantifythesprayperformanceparametersforbothPFIandG-DIgasolinesprays.Thisincludesrecommendedproceduresfortheimaging,measurementandreportingofimportantsprayparameterssuchaspenetration,dropsizesandsprayconeangle.Theserecommendedpracticesthathavebeendevelopedbyanindustry-widecommitteewillprovidebothendusersandOEMswithmeasurementandreportingcriteriathatarecriticalforfuturetechnicaldevelopments,andthatwillsignificantlyenhancetheabilityoftheresultstobeverifiedbyrepeattestinginotherlaboratories.
报告。
工业委员会开发的推荐实验将给终端用户和原型设备制造商提供对将来技术发展很重3.2FuelInjectorandSprayClassifications
燃油喷油器和喷雾分类
ThetwomajorclassificationsofautomotivefuelinjectorsarethePFIinjectorandtheG-DIinjector,aswasbrieflydiscussedintheprevioussection.Beyondthatbroaddivision,however,arenumeroussub-categoriesofmanycommoninjectortypesthatarecurrentlyinuse.Thesecondlevelofclassificationisbynozzledesign,withsomecommonrepresentativetypesillustratedforgasoline-directinjectioninFigure4.
汽车燃油喷油器的两个主要类型是PFI和GDI喷油器,在前面章节已经简单的讨论过。
除了广义的划分,当前有大量的普通喷油器类型的子类型在使用。
第二级的分类是按喷嘴设计进行分类,在图4中说明了一些汽油直接喷射的常见的有代表性的类型。
FIGURE4-G-DIINJECTORSUB-CLASSIFICATIONBYNOZZLEDESIGN
Thedesigncategoriesarequitediverse,andonlythemostrepresentativesareshownhere.Asdiscussedinthenextsection,manyoftheclassificationsforG-DIinjectorsalsoapplytoPFIinjectors.Thisincludesthemultihole,thebentsprayandtheair-assist.Therearenumerousadditionalsub-classificationsthatmaybeusedtoconvenientlyidentifytypesofPFIandG-DIinjectors.Mostofthesesub-classificationsapplytobothoveralltypes.Theseincludethetypeoftip,whichmaybeapintleoranisolatingdirectorplatecontainingoneormoredeliveryholes.TheCasting-Netinjectortip,forexample,wasdevelopedtoalleviatethecommondifficultyencounteredinbendingaspray,whichistonormallyyieldagre
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