进气和排气外文文献翻译、中英文翻译、外文翻译

IntakeandExhaust

Tunedintakemanifold

FirstintroducedbyMercedes300SLin1954,tunedintakemanifoldisnotexactlyanewtechnology.Itisdiscussedherejustbecauseitsprincipleisusefultoourfurtherstudyofvariableintakemanifold.

Before1950s,engineersbelievedshortintakemanifoldswerethebesttoenginebreathing.Thentheydiscoveredthatundersomeconditionslongintakemanifoldscouldactuallyimproveoutput,thankstoaso-called"superchargingeffect".Howisthatdone?Let'sseethefollowingillustration:Whenfreshairissuckedintocombustionchamber,itgathersspeedandmomentumintheintakemanifold.Assoonastheinletvalveisclosed,thefast-movingairhitsthevalveandcompresses,generatinghighpressure.Withnowheretogo,thishighpressurebouncesback,travelsalongtheintakemanifold,hitstheplenumattheothersideandbouncesbackagain.Inthisway,thehighpressurebouncesbackandforthalongtheintakemanifolduntiltheinletvalveopensagain,creating

pressurewaves.

Nowtheinterestingthingis:iftheinletvalveopensagainexactlywhenthepressurewavecomesback,thepressurewavewillhelpchargingthecombustionchamberduetoitshighpressure.Thisisnotunlikechargingthecombustionchamberwithalightsupercharger,thuswecallthissuperchargingeffect.

Inordertomatchthetimingofvalveopening,thefrequencyofpressurewaveshallsynchronizewithenginerev,obviously.Thisfrequencyisdependentonthelengthoftheintakemanifold(Linthefigure).Thelongerthelength,thelongerthetimepressurewavetakestobouncebackthusthelowerfrequencyofpressurewaveisattained.Asaresult,alongerintakemanifoldleadstosuperchargingeffectatlowerenginerev.Ashortermanifoldleadstosuperchargingeffectathigherrev.Byselectingasuitablemanifoldlength,wecanobtainthedesiredpowercharacteristic.

Calculationsfoundinordertoachieveusefulsuperchargingeffect,theintakemanifoldshallbeunusuallylong.Ifitistooshort,thepressurewavewillbouncebackandforthtoomanytimesinthemanifoldbeforethevalveopensagain,bythenthehighpressureislargelydiminished.Thereforeatunedintakemanifoldshallbelong.Unfortunately,tunedintakemanifoldworksonlyacrossanarrowrevband.Iftheenginerevsbeyondthatband,thepressurewavewillarrivetoolateintheintakestroke,contributinglittletocharging.Iftheenginerunsbelowthatrevband,thepressurewavewillarrivetheinletvalvebeforeitopens.Inbothcases,thelowpressureareaofpressurewavemayevenworkagainstcylindercharging,hamperingtorqueoutput.

Asportscarenginemayemployashortertunedintakemanifoldtooptimizeitsoutputathighrev(intheexpenseoflowtomediumrevoutput).Onthecontrary,aheavysedanorcommercialvanenginemaychoosealongermanifoldtofavourlow-rpmoutputatthepriceofhigh-revoutput.Asyoucansee,theselectionofmanifoldlengthisalwaysacompromise.That'swhymanymodernenginesturntovariableintakemanifold...

VariableIntakeManifold(VIM)

Variableintakemanifoldhasbeenpopularonnaturallyaspiratedenginessincethemid-1990s.Itisprimarilyemployedtobroadenthetorquecurve,orinorderwords,improvetheflexibilityofengine.Conventionaltunedintakemanifoldfocusesonanarrowrevrange.Incontrast,VIMoffers2ormorestagesofintakeconfigurationtodealwithdifferentenginespeeds.Thissoundsverymuchlikevariablevalvetiming,butVIMisgenerallycheapertoproducebecauseitinvolvesonlysomecastorplasticmanifoldsandafewelectric-operatedvalves.ThatexplainswhyitwasappliedtocheaperandsmallerengineswellbeforeVVTbecamepopular.Today,manyenginesemploybothfeaturestoachievethebestresults.

However,variableintakemanifoldisrarelyusedonturbochargedorsuperchargedengines-Volkswagen's2.0TFSIengineisoneofthefewexceptions.Thisisbecauseforcedinductionoffersastrongsuperchargingeffectalready.ThislargelyreducesthebenefitofVIM,thusitsadditionalcostsandweightaredifficulttojustify.Asmoreandmorecarsareswitchingtoturbochargedengines,thepopularityofVIMisexpectedtocooldownintheforeseeablefuture.

TherearetwokindsVIM:variablelengthtypeandresonancetype.

Variablelengthintakemanifold(VLIM)

Variablelengthintakemanifoldisadirectanswertotheshortcomingofconventionaltunedintakemanifold.Ifafixedlengthintakemanifoldisoptimizedforaverynarrowrevband,whynotgiveit2setsofintakemanifold,onewithshortpipestoservehighrpmwhileanotherwithlongpipestoservelowrpm?Byusingsimplebutterflyvalves,switchingbetweenthelongandshortpipesareeasy.SomeearlyVLIMsystems,likethisFord2.5DuratecV6,usedseparatelongandshortpipes,whichiseasilyvisiblehere.Theshortpipesgotothenearestcylinderbankwhilethelongpipesgototheoppositebank.Sucharrangementisspaceengaging.Thelackofspaceleadstonarrowerpipesused,thusitisnotverysuitabletohigh-performanceengines.ThatiswhymostVLIMsystems,likethisoneonHondaK20Cengine,havetheirlongandshortintakepathssharingthesamemanifolds.Atlowrpm,theairrunsthroughthelongmanifold;Athighrpm,avalveopenstoashort-cutpath,thustheairjoinsthemanifoldatlaterstage.

3-stagevariablelengthintakemanifoldIf2stagesarenotgoodenoughtobroadenthetorquecurve,whynotuse3stages?

ShownhereistheAudi4.2-liter40-valveV8usedinthelate1990stomid-2000s.ItsVLIMsystemislocatedinsidetheV-valleytosavespace.Therearetwoflapsinsidethesystem.Withbothclosed,thefreshairrunsthroughthefulllengthofmanifold.Withoneflapopens,theairrunsthroughashort-cutpath.Withanotherflapopens,anevenshorterpathisestablished.

Thefollowingtorquecurveshowstheeffectofthe3stagesofVLIM:The3-stagesystemisalittlebitmorecomplicatedandspaceengagingthan2-stagesystem.ItwaseventuallyabandonedwhenAudiintroduceddual-continuousVVTandFSItobroadenthetorquecurve.Continuousvariablelengthintakemanifold-e.g.BMWDIVABMW'sDIVA(DifferentiatedVariableAirIntake)systemwasfirstintroducedtotheN52V8engineson7-Seriesin2001.Itistheworld'sfirstcontinuouslyvariablelengthintakemanifold.

Theprincipleissimple.Theintakemanifoldofeachcylinderisarrangedincircularshapeandhalf-recessedintotheV-valley.Theinnerwallisactuallyarotor,onwhichtheairinletislocated.Whentherotorswivels,thepositionoftheairinletmovesinrelationtotheouterhousingofmanifold.Thisvariestheeffectivelengthoftheintakemanifold,fromamaximum673mmto231mm.

Below3500rpm,theDIVAusesthemaximummanifoldlengthtooptimizelow-endtorque.Beyond3500rpm,thelengthisreducedgraduallyaccordingtorev,keepingthesuperchargingeffectatoptimumlevel.

AstheDIVArequiresacircularconstruction,itoccupiesmorespace(especiallyheight)thanotherVLIMsystems.Thispreventitfrombecomingpopular.EvenBMWitselfwasnotkeenonthetechnology.Whenthe4.4-literV8wasenlargedto4.8liters,itsextratorqueallowedBMWtoabandontheDIVAforasimpler2-stageVLIMsystem.ThenextgenerationV8evenswitchedtoturbocharging,soDIVAhasnohopetoreturn.Today,itremainstobetheonlycontinuousvariableintakemanifoldevermadetoproduction.Resonanceintakemanifold

BoxerenginesandV-typeenginesmayemployresonanceintakemanifoldtobroadentorquecurve.Eachbankofcylindersarefedbyacommonplenumchamberthroughseparatepipes.Thetwoplenumchambersareinterconnectedbytwopipesofdifferentdiameters.Oneofthepipescanbeclosedbyavalvecontrolledbyenginemanagementsystem.Thefiringorderisarrangedsuchthatthecylindersbreathalternatelyfromeachchamber,creatingpressurewavesbetweenthem.Ifthefrequencyofpressurewavesmatchestherev,itcanhelpfillingthecylinders,thusimprovedbreathingefficiency.Asthefrequencydependsalsoonthecross-sectionalareaoftheinterconnectingpipes,byclosingoneofthematlowrev,theareaaswellasfrequencyreduce,thusenhanceoutputatlowerrev.Athighrpm,thevalveisopenedthusimproveshigh-speedcylinderfilling.ThisistheresonanceintakesystemonPorsche996GT3.Notethatithas2pipesconnectingbetweenteh2plenumchambers.

ResonanceintakesystemhasbeenusedinvariousPorschesstartingfrom964Carrera.In993,Porschecombineditwithanadditionalvariablelengthmanifoldtoforma3-stageintakesystemnames

VarioRam.However,thesystemisveryspaceconsuming(seerighthandsidepicturebelow),sofrom996forwarditrevertstotheresonanceintakesystemonly,althoughPorschekeepsusingthenameVarioRam.HondaNSXisanotherrareapplicationoftheresonanceintakesystem.

PorscheVarioRamsystemon993A:below5000rpm:longpipes;resonanceintakedisabled.

B:5000-5800rpm:longpipesplusshort-piperesonanceintake,withoneinterconnectedpipeoftheresonanceintakeclosed.

C:above5800rpm:longpipesplusshort-piperesonanceintake,withbothinterconnectedpipesoftheresonanceintakeopened.TunedExhaust&VariableBack-PressureExhaust

Thedesignofexhaustmanifoldisnotunlikeintakemanifold.Exhaustgasemitsintheformofhigh-pressurepulse.Ifyouhaveamicro-analysisonthepulse,youwillfindthepulseisnotalwayshigh-pressure.Infact,shortlyafterthefirstsurgeofpressure,thereisaperiodofnegativepressure(i.e.lowerthanatmosphericpressureor1bar),asshowninthegraphbelow.Why?Becausethegaspulsehasmassandmomentum.Toletyoueasiertounderstand,imaginethegaspulseasabigtruckrunningonhighwayandyouarestandingattheroadside.Whenthetruckpassesyou,yourhairislikelytobesuckedtowardstheroad,becausethereisalow-pressureareatailingthetruck.Thefasterthetruckruns,thelowerpressureisbuilt.Ifwecancollecttheexhaustpulsesfromallcylinderswithequal-lengthexhaustmanifolds(or"header"),wewillgetanevenlydistributedpulsetrain.Interestingly,thisevenlydistributedpulsetrainactuallyhelpssuckingexhaustgasoutofthecombustionchambers,asthelow-pressuretailofonepulsesucksthenextpulse,soforth.Whenbothintakeandexhaustvalvesareopenedduringtheoverlappingperiod,theaforementionedeffectevenhelpssuckingfreshairintothecombustionchamber.Asaresult,thiseffectiscalled"reverse-supercharging"or"scavenging".

Tomakethebestuseofscavengingeffect,anequal-lengthexhaustmanifoldisamust.Besides,toreducetheinterencebetweentheexhaustgaspulsesfromdifferentcylinders,theindividualpipesshallbelong.Thisexplainswhymostracingenginesandhigh-performanceenginesemploytunedexhaustmanifoldswithverylongandstrangelyroutedpipes.Thetunedexhaustmanifold(header)onBMWM3V8.Notetheindividualpipesbeforethecollectorarelongandequal-length.Togetthescavengingeffectworking,thegasflowshouldrunquickenoughintheexhaustmanifold.Takeourtruckexampleagain,ifthetruckiscruisingslowlyonmotorway,thereishardlyanyvacuumeffectyoucanfeel.Exhaustgaspulseisthesame.Tospeedupthegasflow,obviously,thebestwayistousenarrowerexhaustpipesthroughoutthewholeexhaustsystem-includingmanifolds,collectorandmuffler.However,narrowerpipesalsogeneratemoreresistancetogasflow,orwhatwecall"back-pressure".Athighrpmwheretheexhaustgasrateisenormous,theback-pressurewillbebigenoughtooutweighthebenefitsofscavengingeffect.Consequently,narrowexhaustpipesareonlybenefitialtolowrevoutput.Onthecontrary,large-diameterexhaustpipesreduceback-pressureathighrpm,boostingtop-endpower,butatlowrpmtheexhaustgasflowistooslowtogeneratescavengingeffect,soitsoutputsuffersatlowrpm.

Thatiswhymanyperformancecarsoptfor

variableback-pressureexhaust.Atlowrpm,theexhaustgasgoesthroughanarrowpathinthemuffler,whichconsistsofmultiplestagesofsilencer.Thisreturnsrelativelyhighback-pressure,butthenarrowpathresultsinhighflowingspeed,hencegoodscavengingeffect.Athighrev,aby-passvalveopenstoasecondpathforthegastoescape,reducingback-pressureandenhancepoweroutput.Principleofvariableback-pressureexhaustTheby-passalsochangesthesoundquality,makingitlouderand"sportier".Thereforevariableback-pressureexhaustispopularonsportscars.外文文献翻译第第页共9页进气和排气一进气歧管首先介绍了梅赛德斯300SL1954、进气歧管是不是一个新技术。这里讨论的只是因为它的原则是有用的，我们进一步研究可变进气歧管。1950年以前，工程师们认为短进气歧管是发动机呼吸的最佳选择。然后，他们发现，在某些条件下，长进气歧管实际上可以提高产量，由于所谓的“增压效应”。这是怎么做的？让我们看看下面的插图：当新鲜空气吸入燃烧室时，它在进气歧管中聚集速度和动量。当入口阀门关闭时，快速移动的空气撞击阀门并压缩，产生高压。没有地方去，这种高压反弹，沿着进气歧管，击中在另一侧的全会和反弹回来。这样，高压来回沿进气歧管到进气阀再次打开，创建压力波。现在有趣的是：如果进气阀在压力波回来的时候完全打开，压力波会因为高压而帮助燃烧室充电。这与用轻增压器增压燃烧室不同，因此我们称之为增压效应。为了匹配阀门开启的时间，压力波的频率应与发动机转速同步，明显。这个频率取决于进气歧管的长度（L在图中）。长度越长，压力波恢复的时间越长，压力波的频率越低。其结果是，较长的进气歧管导致增压效果在较低的发动机转速。较短的歧管导致增压效应在更高的转速。通过选择合适的歧管长度，我们可以得到所需的功率特性。计算发现，为了实现有益的增压效果，进气歧管应异常长。如果太短，压力波会在阀门开启之前多次在歧管中来回跳动，这时高压会大大降低。因此，调谐进气歧管应该是长的。不幸的是，调谐进气歧管只工作在一个狭窄的转速带。如果发动机转速超过波段，压力波到达进气行程太晚，贡献不充电。如果发动机运行低于转速带，压力波将到达进气阀打开之前。在这两种情况下，压力波的低压区甚至可以对气缸充电，阻碍转矩输出。跑车发动机可以采用较短的调谐进气歧管优化其输出在高转速（费用低到中等转速输出）。与此相反，一个沉重的轿车或商用面包车发动机可以选择一个较长的流形，有利于低转速输出的价格高转速输出。正如你所看到的，流形长度的选择总是一种折衷。这就是为什么许多现代发动机转向可变进气歧管…二可变进气歧管（进气）自上世纪90年代中期以来，可变进气歧管在自然吸气式发动机上得到了广泛的应用，主要用于拓宽扭矩曲线，或者提高发动机的灵活性。传统的调谐进气歧管集中在一个狭窄的转速范围。与此相反，提供了2个或更多的进气配置阶段，以处理不同的发动机转速。这听起来很像可变气门正时，但一般来说生产成本较低，因为它只涉及一些铸造或塑料歧管和一些电动阀。这解释了为什么它被应用到更便宜和更小的发动机VVT走红之前。今天，许多发动机采用这两种功能，以达到最佳效果。然而，可变进气歧管是很少使用涡轮增压或增压引擎-大众的2TFSI发动机是少数例外之一。这是因为强迫感应已经提供了很强的增压作用。这在很大程度上降低了成本效益，因此其额外的成本和重量难以自圆其说。随着越来越多的汽车转向涡轮增压发动机，预计在未来可预见的未来，汽车的普及将会降温。有两种类型：可变长度型和谐振型。三可变长度进气歧管（VLIM）可变长度进气歧管是直接调节传统进气歧管的缺点。如果一个固定长度的进气歧管进行了优化，一个非常狭窄的转速波段，为什么不给它2套进气歧管，一个短管，以高转速，而另一个长管，以低转速？通过使用简单的蝶阀，长和短管道之间的切换是容易的。一些早期的VLIM系统，这样福特2.5DuratecV6，用单独的长和短的管道，这是很明显的在这里。短管到最近的气缸组，而长管转到相反的银行。这样的安排是空间啮合。空间的缺乏导致使用的管道变窄，因此它不是非常适合高性能发动机。这就是为什么大多数VLIM系统，像这样一个在本田K20C引擎，有长、短进气路径共享同一流形。在低转速时，空气流经长歧管；在高转速时，阀门打开一个捷径路径，从而空气加入歧管在稍后阶段。四三级可变长度进气歧管如果2个阶段不够好，以扩大扭矩曲线，为什么不使用3个阶段？这里显示的是奥迪4.2升40阀V8用在上世纪90年代末到2000，VLIM系统位于v-valley节省空间。系统内有两个襟翼。两个封闭的，新鲜的空气贯穿歧管的全长。一个皮瓣打开，空气通过一个捷径路径。随着另一个皮瓣打开，甚至更短的路径建立。以下的扭矩曲线显示的VLIM3阶段的影响：三级系统是更复杂一点，空间啮合比二级系统。最终被放弃，当奥迪推出双连续可变气门正时及FSI扩大扭矩曲线。五连续可变长度进气歧管-例如宝马宝马的Diva（区分可变进气）系统首次引入到N52的V8引擎在7系列2001。它是世界上第一个连续可变长度进气歧管。原理简单。各缸的进气歧管安装在圆形和半凹进v-valley。内壁实际上是一个转子，入口位于其上。当转子旋转，在关系到歧管外壳进风口移动位置。这改变了进气歧管的有效长度，从最大673毫米到231毫米。低于3500转，使用最大的流形长度优化低端扭矩。超过3500转，转速逐渐降低根据长度，保持在最佳水平增压效果。作为主角需要一个圆形建筑，它占用更多的空间（特别是高