外文翻譯--內燃機主動衰減排氣閥門設計 英文版.pdfVIP

Designofanactiveexhaustattenuatingvalveforinternalcombustionengines.R.Boonen,P.SasKULeuven,DepartmentofMechanicalEngineering,Celestijnenlaan300B,B-3001,Heverlee,Belgiume-mail:rene.boonenmech.kuleuven.ac.beAbstractAnactivesilencertoattenuateinternalcombustionengineexhaustnoiseisdeveloped.Thesilencerconsistsofanelectricallycontrolledvalveconnectedtoabuffervolume.Thepulsatingflowfromtheengineisbufferedinthevolumeandthevalveresistanceiscontinuouslycontrolledsuchthatonlythemeanflowpassestotheatmosphere.Thisflowisfreeoffluctuationsandconsequentlyfreeofsound.Thedesignoftheactivesilenceriscarriedoutusingelectricalanalogcircuits.First,theinteractionbetweentheactivesilencerandtheenginewillbestudiedusingananalogcircuitincludingthecombustionengineandalinearizedactivesilencer.Then,adetailedvalvemodelisbuiltinaseparateelectricalanalogcircuit.Itincludestheelectrical,themechanicalandtheflow-dynamicpropertiesoftheactuatorvalve.Theactuatorvalveconceptisthensimulated,fromwhichaprototypecanbeconstructed.Theactivesilencerhasbeentestedonacoldenginesimulator.Thisdevicegeneratesrealisticexhaustnoisewiththeassociatedgasflowusingcompressedair.Thesilencercanattenuatepulsationsfromenginesatverylowrevolutionspeed,withoutpassiveelementspreconnectedbetweentheengineandtheactivesilencer.Thisisnotpossibleusingloudspeakerbasedactivesilencers.1IntroductionTheinternalcombustionenginehasfounditswayintoabroadspectrumofapplications,whereintransporta-tionhasfarthelargestshare.Thesuccessofthein-ternalcombustionenginehasalsocreatedproblemsassociatedwithit,suchasairpollutionandenviron-mentalnoise.Duringthepastdecades,legislationhascomefor-wardwhichstringentlyreducesairpollutants,green-housegasesandnoiseemission.Today,thenoiseemissionlimitsaresetto74dBAforcarsand80dBAforheavyvehicles1.Forcars,theemissionofCO2islimitedto190g/km(EUIII-directive),andwillbefurtherreducedto170g/km(EUIV)in2003and140g/km(EUV)in2008.Althoughthesedirectivesarenotrelatedatfirstsight,theydohavetheirimpli-cationsontheexhaustsystemdevelopment.Itwillbenecessarytodevelopexhaustsystemswithminimumbackpressuretotheengine,tomaximizeengineeffi-ciencyandthiswithoutlossofnoiseattenuationper-formance.Awayouttothisproblemistodevelopactiveexhaustsystems.Muchresearchonactivenoisecancellationinductsiscarriedoutintherecentyearsandnumer-ouspatentshavebeengenerated.Loudspeakersys-temsaresuccessfullyappliedandcommercialavail-ableinventilationchannels2.Loudspeakersystemsarealsodevelopedforstationarydieselengines,forexamplebyDetroitDieselCorporation3andtheKEBAAISTM-system.Forcars,activeloudspeakersystemsaredevelopedforsixormorecylinderen-gines4.Forfour-cylinderengines,loudspeakersys-temssufferfromproblemsasthelowsoundgenerat-ingefficiencyandreliabilityintheextremeconditionsofanengineexhaust.Applyingacontrollablevalveintheexhaustductisamorerobustconcept.Therestrictingelementofthevalvecanbesmallandrigidlyconstructed.Itcanbeexposedtotheexhaustgasdirectly.Theresistanceofthevalveiscontinuouslyvari-ablebyapplyinganexternalsignal.Itisassumedthatthevalveispurelyresistive,itisntcapabletostoreenergyfromthegasflow.Asconsequenceofthegasflow,thevalvegeneratesapressuredropoverit.Ac-tivenoisecancellationisachieved,whenthevolumevelocitybehindthevalveiskeptconstant.Infigure1,thefirstgraphdemonstrateshowthesoundpressureinfluencesthefluidflowviathevalveresistancecharacteristic.Thesecondgraphdemon-strateshowtheoppositefluctuatingflowisgeneratedfromthemeanpressuredropoverthevalvebyvary-33Figure1:Basicprincipleusingavalvetocontroltheflowthroughaduct.Thesymbolsinthefiguremean:Q0ismeanfluidflow,qisflowfluctuation,p0ismeanpressure,pisthepressurefluctuation,Kisthevalveconstantwhichexpressestherelationbetweenpressureandflow,kisthevariationonK.ingthevalveresistance.Superpositionofbotheffectsresultsinaconstantvolumeflow,showninthethirdgraph.Basedonthisconcept,anoiseattenuatingde-viceisdevelopedbyLEA(UniversityofPoitiers,France)5,6,usingabutterflyvalve,andistestedonaninternalcombustionenginetestrig.Thetestrigconsistsofan1350cm3fourcylindercarengineequippedwithanhydraulicbrake.Intheexhaustlinetwopassivemufflersarepreconnectedtotheactuatorvalve.Ascontrolstrategy,ax-LMSfeedforwardandafeedbackcontrolsystemaretested.Inthefeedfor-wardcase,thethreefirstharmonicsarereducedby20to30dB.Inthefeedbackcase,thefirstharmonicisreducedby20dB,thesecondharmonicby5dB.Theresearchworkpresentedinthispaperaimstodevelopanactiveexhaustsilencerbasedonavalveconcept,capabletohandletheacousticalpowerofthepressurepulsationoftheengineexhaustwithouttherequirementtoinstallsilencerspriortotheactivede-vice.Thegeneratedbackpressuremustbelow.Aftertheactivedevice,asmallpassivesilencercanbein-stalledtoattenuatethehighfrequencynoise.2Developmentoftheactivesi-lencer2.1PrincipleTheoretically,insertinganactivevalveintheflowofavolumevelocitysource,likeacombustionengine,hasnoeffectifnocapacitiveelementsarepresentbe-tweenthesourceandthevalve.Thevolumevelocitysourceforcesaprescribedflowthroughtheexhaustsystem,whateverthepressurebecomesinit.Capac-itiveelementscanbeintroducedusingductsorvol-umes.Whenthevalveisinsertedinanexhaustductofanenginewithoutadditionalcapacitiveelements,ahighbackpressurewillbegeneratedoronlyalownoiseattenuationwillresult.Themostsimplesystemabletocontrolofavol-umevelocitysourceusingacontrolledvalveispre-sentedinfigure2.Theengineactsasavolumeveloc-itysource.Attheexhaust,avolumewithcapacityCandaregulatingvalvewithvariableresistanceR(t)isconnected.Thetranslationofthephysicalsystemresultsintheelectricalequivalentcircuit7showninfigure2below.TheimpedanceZistheimpedanceofthetailpipeandtheopenairradiator.TheflowfromthesourcewillsplitoverthecapacitorCandthetimedependentresistorR(t).Now,thecontrollerhastovarythevalveresistanceduringtime,suchthatthefluctuatingflowthroughtheresistancebecomeszero.Figure2:Themostsimpleschemeofanactivecon-trolvalveonaninternalcombustionengine,approxi-matedasavolumevelocitysource.Thevariationofthevalveresistanceisobtainedfromtheelectricalequivalentcircuit:UB=1CintegraldisplayICdt=IR(R(t)+Z)(1)Differentiating(1)resultsin:IC1C=dIRdtR(t)+IRdR(t)dt+ZdIRdt(2)Constantflowthroughthevalveopeningimplies:dIRdt=0(3)Thecontrollerhastovarythevalveresistanceduringtimeaccording:R(t)=R0+integraldisplay1CICIRdt(4)34PROCEEDINGSOFISMA2002-VOLUMEIwhereinR0istheinitialvalveresistance.Thesameresultcanbeachievedbyacontrollerwhichmini-mizesthepressureUZafterthevalve:dUZdt=ZdIRdt=0(5)Thissimpleconsiderationhastwoimportantconse-quences.First,bybalancingthevolume-valvecom-bination,itisalwayspossibletocontroltheflowofanyvolumevelocitysource.Second,theresistanceR0canbechosenfreelywiththeonlyrestrictionthattheresistanceR(t)remainsalwayspositive.There-sistanceR0canbeoptimizedtoobtainminimumbackpressuretotheengine,resultinginahigherengineef-ficiency.2.2ElectricalequivalentmodelfortheengineandthesilencerThesimplemodel,presentedinfigure2,looksnotveryrealisticforanengineexhaustsystem,thereforethemodelwillbeexpanded.Thevolumevelocitysourcewillbereplacedbyanenginemodel,andaductisconnectedbetweentheengineandtheactivesilencer.Atailpipeisconnectedbehindthesilencer.Theresultingcircuitispresentedinfigure3.Theleftpartofthecircuitistheenginemodel.Thefourvariablecapacitorsrepresentthefouren-ginecylinders,whosvolumevariessinusoidalbe-tweenmaximumanddeadvolume.Theuppersetofswitch-resistorsrepresenttheintakevalves,thelowersettheexhaustvalves.Theswitchesareactuatedinthesamesequenceasthecamshaftoperatestheen-ginevalves.Thefourshorttransmissionlinesbehindtheexhaustvalveresistorsrepresentthefourexhaustconduitsbetweenthecylinderportsandtheexhaustmanifoldjunction.TheintakesideisconnectedtoavoltagesourceUBrepresentingtheatmosphericpres-sureandequals100kV.Thecombustionissimulatedbychargingthecylindercapacitorbyapulsingcur-rentsourceparalleloverthecapacitor.Thechargetimepointcorrespondstotheignitiontimepoint.Therightpartrepresentstheactiveexhaustsys-tem.ThesilencerisconnectedtotheengineviatheductrepresentedbythetransmissionlineT.Theca-pacitorCrepresentsthebuffervolumeandthevari-ableresistorR(t)thecontrolvalve.Thetransmis-sionlineTtrepresentsthetailpipeandtheresistor-inductorcombinationRaandLacorrespondstothesphericalradiatorimpedance.Insimulation,acollo-catedfeedbackcontrollerconductsthecontrolvalveFigure3:Electricalanalogcircuitforaninternalcombustionengineequippedwithanactivenoisecon-trolvalve.resistance.Thiscontrollerisonlyneededtodeter-minetheactivesilencerproperties.Inpractice,othercontrolstrategiesmustbeappliedtohandlethetimedelaybetweenthevalveactionanditseffectintheerrorsensor.Inprinciple,thebackpressuretotheenginecanbesettoanydesiredvaluebychoosingtheappropriatebuffervolumecapacitorC.Inpractice,itwillresultinacompromisebetweenavailablespacefortheactivesilencerandacceptablebackpressure.Figure4:Simulatedindicatordiagramfromthecir-cuitpresentedinfigure3.2.3SimulationresultsIntheelectricalcircuitoffigure3,theengineparam-etersofa2000cm3engineareintroduced.Theductshaveadiameterof60mm.Theductbetweentheen-gineandthesilenceris500mmlong,thetailpipe700mmlong.Thebackpressureissetto10kPa,resultinginabuffervolumeof12dm3.Theinitialactuatorvalveresistanceissetto200k(1=1Pas/m3).Thefeedbackcontrolgainissetto108.Infigure4,thesimulatedengineindicatordiagramACTIVENOISECONTROL35Figure5:Simulatedtailpipeabsolutepressure.Thecontrollerstartsat0.2s.ispresented.Actually,thisdiagramhasnophysicalsignificance,itisan”isothermal”simulation.Onlythepressureattheexhaustvalveopeningtimepointmusthaveitscorrectvalue,whichisdeterministicfortheexhaustnoise.Theexhaustpressureinthetailpipeisdisplayedinfigure5.Thecontrollerisacti-vatedat0.2s.Activatingthecontrollerat0.2sdoesnoteffectthegasflowfromtheengine,asindicatedinfigure6.Theenginebehavesasavolumevelocitysource.Infigure7,theabsoluteb