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1、ProclMechEPartD:DOI: 10.1177/09544070221104350S SageReviewArticIeStudyonturbocompoundsystemforaheavy-dutydieselenginebycombiningmatchinganalysiswithexperimentsYinYong1,2,WuZhijun1zZhaoRongchao3GzZhugeWeilin4andHuZongjie1AbstractJAutomobiteEngineering2023,Vol.237(8)1775-1789IMechE2022Articlereuseguid
2、elines:Inthiswork,toimprovethefueleconomyoflong-haulcommercialvehicles,theeffectsofturbocompoundsystemmatchingonengineperformancewerenumericallyandexperimentallystudied.Firstly,aIDGT-POWERsimulationmodelofan11Lheavy-dutydieselenginewasestablishedandverifiedbytheexperimentaldata.Secondly,theperforman
3、cesoftheturbocompoundenginematchingwithdifferentsizesoffixedgeometryturbine(FGT)andpowerturbineswereanalyzed.Itwasfoundthattheexhaustenergydistributionbetweentheturbochargerturbineandpowerturbinehadasignificantimpactonengineperformance,andthesizeoftheturbochargerturbinehadamorenoticeableimpactthanth
4、epowerturbine.BasedontheFGTturbocompoundsystemsimulationresult,anappropriatevariablegeometryturbocharger(VGT)andthreewastegateturbochargers(WGT)wereselectedforfurthersimulationandexperimentalresearch.Inaddition,theimpactsofthetransmissionratiobetweenthepowerturbineshaftandtheenginecrankshaft,andthef
5、uelinjectiontimingontheengineperformancewereexperimentallystudied.Theenginetestresultshowedthatthefueleconomywasimprovedby1.6%underEuropeanSteadyState(ESC)cyclewhilekeepingtheweightedNOxemissionthesameastheoriginalengine.Finally,theturbocompoundenginewithWGTwasinstalledonaheavy-dutylong-haulcommerci
6、alvehicleforroadtests.Thefueleconomyofthevehiclewasimprovedby2.54%underthe80km/hconstantspeedroadtest.KeywordsTurbocompoundsystem,heavy-dutydieselengine,variablegeometryturbine,wastegateturbine,powerturbineDatereceived:27October2021;accepted:2May2022IntroductionDieselengineshavebeentheprimarypowerso
7、urcesforcommercialvehiclesandengineeringmachineryforalongtimebecauseoftheirexcellentadaptability,highefficiency,andreliability.Itisimportanttofurtherimprovethedieselenginesthermalefficiency.Thein-cylindercombustionprocessofdieselengineshasbeendramaticallyimprovedbytechnologiessuchashigh-pressurecomm
8、on-rail,high-efficiencyturbocharging,andexhaustgasrecirculation(EGR).Dieselenginesbrakethermalefficiency(BTE)hasreachedmorethan45%.However,ithasbecomeincreasinglydifficulttoimproveBTEonlybyoptimizingtheincylindercombustionprocess.Wasteheatrecoveryisgenerallyacceptedtoimprovetheenginesoverallefficien
9、cy.Themaintechnologiesofwasteheatrecoverj,includeOrganicRankineCycle(ORC),1ThermoelectricGeneration(TEG),2andturbocompounding.3ComparedwithORCandTEGtechnology,turbocompoundinghastheadvantagesofrelativelysimplestructureandgoodenergy-savingperformance.Inaddition,theenginebackpressurecanbeincreasedsign
10、ificantlyduetoapowerturbinedownstreamoftheturbochargerturbine.Asaresult,ahigherEGRratecanbeadoptedtoreduceNitrogenOxides(NOx)emission.Furthermore,theengineexhaustenergyisabundantforlong-haulcommercialvehiclesbecausetheir1TongjiUniversity,Shanghai,China2DongfengCommercialVehicleCo.Ltd.,Wuhan,China3So
11、uthChinaUniversityofTechnology,Guangzhou,China4TsinghuaUniversity,Beijing,ChinaCorrespondingauthor:ZhaoRongchao,SouthChinaUniversityofTechnology,381WushanRoad,TianheDistrict,Guangzhou510640,China.Email:merczhaoenginesmainlyoperateathighspeedsandhighloadscomparedwithpassengercarengines.Therefore,itis
12、conducivetoreducingfuelconsumptionbyapplyingturbocompoundtechnologyinlong-haulcommercialvehicles.Inaturbocompoundengine,apowerturbineisusedtorecovertheexhaustenergyandturnitintomechanicalworkorelectricity.Therearethreemainconfigurationsforthepowerturbineandturbocharger,includingseries,parallelandint
13、egratedlayouts.Weietal.4comparedtheperformanceofa1.8LturbochargedgasolineenginewiththreeIurbocompoundlayoutsunderdrivingcycles.Itwasshownthattheparallelturbocompoundlayouthadthebestfuelsavingperformance.However,theexhaustmassflowratiobetweenthepowerturbineandturbochargerturbineneedstobeadjustedusing
14、twovalvesaccordingtotheengineoperatingcondition.Sincetheoperationconditionfrequentlychangesontheroad,theparallelconfigurationisunsuitableforvehicleapplication.Inintegratedlayouts,5amotor/generatorisintegratedwiththeturbocharger.Itactsa$amotortoacceleratetheturbochargeratlowenginespeedconditionsforbe
15、ttertransientresponseandasageneratortorecoverthewasteheatforlowerfuelconsumptionathigh-speedconditions.Thematchingandcontrolmethodfortheintegratedturbocompoundsystemiscrucialtogethighoverallefficiency.Yangetal.6proposedamatchingguidelinefortheintegratedturbocompoundsystemandappliedittoatwo-strokelow
16、speedmarineengine.Resultsshowedthatthefuelconsumptioncouldbereducedby2%-3%althreeloadprofiles.Joshietal.78proposedanovelsystemconsistingofsupercharging,turbocompounding,andelectrification.Thepowerflowcouldbeoptimallymanagedinthislayoutbyemployingaplanetarygearsetaccordingtotheroadconditions.Resultss
17、howedthatthefueleconomywasimprovedby11.1%.ThemainchallengeforanintegratedIurbocompoundsystemistodevelopareliablehigh-speedmotorbecauseoftheextremelyhighturbochargerspeed.Theturbineshightemperaturealsorisksdamagingtheelectricmachine.Seriesturbocompounddrawsthemostattentioninvehicleapplication.9Thepow
18、erturbineisgenerallyplaceddownstreamoftheturbochargerturbineinthisconfiguration.Thepowerdistributionbetweenthetwoturbinesismainlydecidedbytheexpansionratiosofthetwoturbines.Theenginebackpressurewillbeincreasedduetotheextractpressuredropinthepowerturbine.Briggsetal.,foundthattheoptimalratedpowerofthe
19、powerturbinefora2.4Lturbochargeddieselenginewas7.0kWatfullengineloads.TheenginesBSFCandBMEPimprovedby2.41%and2.21%,respectively.Mamatetal.1112designedapowerturbinewithalowexpansionratioof1.1,whichcouldreducetheimpactontheenginebackpressure.Thetestresultsshowedthatamaximumbreakspecificfuelconsumption
20、(BSFC)reductionof2.6%wasachievedattheenginespeedof2500rmin.Theoptimalexpansionratioiscloselyrelatedtotheengineparameters.Zhaoetal.13establishedananalyticalmodelwiththerelationshipamongtheseparameters,includingturbineexpansionratio,efficiency,exhausttemperature,enginefuelconsumption,etc.Basedontheana
21、lyticalmodel,theoptimumvalueofthepowerturbineexpansionratiowasdisclosed.Sincetheoptimumexpansionratiosoftheturbochargerturbineandpowerturbinevariedastheengineoperationconditionchanged,avariablegeometryturbinewasadoptedtoregulatetheturbineexpansionratioforhigherengineperformanceatdifferentenginespeed
22、s.14Jyeetal.15establishedanumericalsimulationmodeltostudytheinfluenceofseriesturbocompoundontheperformanceoftraditionalturbochargeddieselengines.Itshowedthattheengine,smaximumpowercouldincreaseby7%athighenginespeed.Onthecontrary,theenginepowerwouldbereducedby4.7%atlowspeedduetoincreasedexhaustbackpr
23、essure.Thenegativeeffectofthepowerturbinecouldbereducedbybypassingtheexhaustflowinthepowerturbine.Finally,theaveragefuelconsumptioncanbereducedby1.9%underallengineworkingconditions.Thespeedofthepowerturbinecanalsobeadjustedaccordingtotheoperationconditionforthebestengineperformance.Katsanosetal.16st
24、udiedtheinfluenceofpowerturbinespeedonengineperformancebasedonanumericalmodel.Itwasfoundthattheoptimalpowerturbinespeeddecreasedwiththedecreaseofengineload.Theoif-designperformanceoftheenginecouldbeimprovedbyadjustingthepowerturbinespeed.Heetal.17proposedacontrollableturbo-compoundingsystemincluding
25、variabletransmissionandapowerturbinebypassvalve.Thetransmissionratiobetweenthepowerturbineshaftandenginecrankshaft,andtheopeningdegreeofthepowerturbinebypassvalvewereoptimizedunderoff-designconditions.Thefuelconsumptionwasreducedby2%and3.4%underthehighwayfueleconomylestandTianjin503drivingcycles.Ins
26、ummary,Iurbocompoundtechnologycanimprovetheenginesfueleconomyby2%-10%inaspecificworkingcondition.However,thepowerturbineincreasestheexhaustbackpressure,increasingthepumpinglossanddeterioratingtheenginefueleconomy.Iftherecoveredexhaustenergybythepowerturbineisinsufficienttooffsetthepowerlossoftheengi
27、ne,theengine,soperatingperformancewilldeteriorate.Theheavy-dutydieselonthelong-haulcommercialvehiclemainlyoperatesathighspeedsandhighloads.Theexcellentmatchingoftheturbocompoundsystemfortheseoperatingconditionsisessentialfortheenginesfuelefficiencyandotherperformances.However,theimpactsofFGT,VGT,WGT
28、matchingwithpowerturbine,andthetransmissionfactoroftheturbocompoundingontheoff-designperformancehavenotbeenthoroughlyanalyzedinpreviousstudies.Thispaperfocusesonthematchinganalysisandexperimentalstudyofturbocompoundsystemsforheavy-onlyonemainfuelinjectionatfullloadconditions.Becausethisstudymainlyfo
29、cusesonFigure 2. Performance map of the power turbine.Figure1.Schematicoftheseriesmechanicalturbocompoundengineandenginetestbench.dulydieselengines.AcomparisonoflheimpactsofFGT,VGT,andWGTontheturbocompoundengineoff-designperformancewasperformed.ThematchingprocesswillbedisclosedfortheVGTandWGTcoupled
30、withthepowerturbinetoimproveengineperformance.ThematchinganalysisinthispaperisbasedonthetypicalseriesturbocompoundsystembyIDenginesimulationandenginetests.Aftertheanalysis,theengineequippedwithWGTwaschosenforfurtherexperimentalstudyandoptimization.Themechanicaltransmissionratiobetweenthepowerturbine
31、shaftandenginecrankshaft,andthefuelinjectiontimingwereexperimentallyoptimized.Inaddition,theturbocompoundenginewasinstalledinaheavydutytruck,androadtestswerecarriedout.Thisworkcanprovideasystematicreferenceforturbocompoundsystemsimulation,matching,andoptimization.EnginesimulationandtestbenchTheschem
32、aticoftheseriesmechanicalturbocompoundengineispresentedinFigureI.Thepowerturbineisfitteddownstreamoftheturbochargerturbine.Itconvertspartoftheexhaustenergyintorolationalkineticenergyoftheenginecrankshaftbythegearsandhydrauliccoupler.Thehydrauliccouplerwasintegratedwithanoverrunningclutch.Itreducesth
33、etorsionalvibrationbetweenthehighspeedpowerturbineshaftandlow-speedenginecrankshaft.Inaddition,itcanpreventreverseworkdonebytheengineatlowpowerturbinespeed.ThepowerturbineinthispaperwasfromCummins(HP841).Itsmaximumpoweroutputis30kW.ThemapofthispowerturbineisshowninFigure2.Allexperimentswereconducted
34、inan11L,fourstroke,six-cylinder,turbochargedheavy-dutydieselengineequippedwithahigh-pressurecommon-railinjectionsystem.Anelectroniccontrolunit(ECU)madebyBoschwasusedtocontrol(hefuelinjectionparameters.ThereisTable1.Specificationsofthetestengine.ParameterDescriptionEnginedisplacement11.12LRatedpower3
35、03kW1900r/minMaximumtorque1850Nm1200-1700r/minCompressionratio18Bore3Stroke(mm)123mm3156mmCombustionchamberRe-entranttypeTurbochargerFixedGeometryTurbineMaximuminjectionpressure1800barEmissionscomplianceChinaVtheeffectoftheturbocompoundsystemonengineperformance,thereisnoengineexhaustafter-treatments
36、ysteminthetest.Butaback-pressurevalvewasfitteddownstreamofthepowerturbineintheexhaustpipetosimulatetheback-pressurecausedbytheaftertreatmentsystem.Theback-pressurewaskept25kPaattheratingcondition.Andtheengine,srawNOxemissionwaskepttheTable 2. Main equipment and their uncertainties of engine test ben
37、ch.EquipmentModelUncertaintiesDynamometerHORIBA WS700FSpeed: 65 rminz Torque: 60.5% FSFuel consumption meterHORIBA FQ-3200CR60.12% FSAirflow meterAVL Flow Sonix Air61%Gas emission analyzerHORIBA MEXA 7100DEGR60.5%Cooling systemEME 42061Csameastheoriginalengine.Themainspecificationsoftheengineareshow
38、ninTable1.TheprimarytestequipmentanditsuncertaintiesareshowninTable2.Apiezoelectricpressuresensor(Kistler6125CU20)coupledwithachargeamplifier(AVL365C01)wasemployedtomeasurein-cylinderpressure.Thepressuredataacquisitionwastriggeredbyanopticalcrankshaftangleencoder(AVL365CC)witharesolutionof0.5CA.Thei
39、ncylinderpressuretracewasutilizedtoverifythecombustionmodel.Theenginespeedandtorquewerecontrolledandmeasuredbyaneddydynamometer.Thegaseousexhaustemissionsandlambdaweremeasuredbyagasemissionanalyzer.AsimulationmodeloftheturbocompoundengineisdevelopedbasedoncommercialsoftwareGT-POWER,asshowninFigure3.
40、Theengineperformancesatfullloadweresimulatedinthissimulation.TheheatreleaseinthecylinderismodeledusingtheWiebefunctionasshowninequation(1),whereDjandSarethecombustiondurationandshapefactor,respectively.u()isthecrankshaftanglecorrespondingtothestartofignition.Sincethisstudymainlyfocusesonfueleconomy,
41、pilotandpostinjectionwerenotusedinthisexperiment.Thefuelisinjectedonlyonceinoneengineworkingcycle.Asaresult,asingleWiebefunctioncanbeused.dQbQbUUOs=6:9s+1PduDuDuuUaS+i#61Dexp6:9DuwhereDiscylinderdiameter,pisin-cylinderpressure,Tistheaveragetemperature,andCmisthemeanvelocityofthepiston.Figure3.Engine
42、simulationmodelwithturbocompoundsystem.Theenergydistributionbetweentheturbochargerturbineandthepowerturbineaffectstheenginesoverallperformance.Theturbochargerandpowerturbineenergyarecalculatedfromequation(4)toequation(7).Intheseequations,thesubscriptOmeans“total,“andthenumberfrom1to6representstheloc
43、ationofthemeasurepointfromtheturbochargercompressorinlettothepowerturbineoutlet,whichisshowninFigure1.Thepoweroutputoftheturbochargerturbine(Wcr)iscalculatedinequation(4):：k41Wc= mi CpjToi (p02=p01) k 1 =hc 351Theheattransfertothewallsinsidethecylinderisobtainedaccordingtoequation(2).dQwdu=aAwTTP2Pw
44、hereAwistheareaofthecontactwall,andthecoefficientaiscalculatedusingtheWoschnimodel,18aspresentedinequation(3).a=3:26Do：2po：8To：55Cm63DWct=hcr114cp,4T041(p5=p04)md4Dwherem4istheexhaustmassflowratethroughtheturbine,cp,4isthespecificheatatconstantpressureoftheexhaust,T04isthegastotaltemperatureatthetur
45、bochargerturbineinlet,hcisturbineefficiency,p5issialicpressureaftertheturbine,PNistotalpressurebeforetheturbine,k4isthespecificheatratiooftheexhaust,whichis1.33.Thepowerconsumedbythecompressor(Wc)isgiveninequation(5).kll100012001400160018002000Engine speed (rmin)1716 (EN) nbJOH190(MWS ouls(dwheremis
46、intakeairmassflowratethroughthecompressor;cp.isthespecificheatatconstantpressureoffreshair;ToisthegastotaltemperatureattheFigure 4 Spressorinlet;hciscompressorefficiency;pandp02istotalpressureatthecompressorinletandexit,respectively,kisthespecificheatratioofair,whichis1.4.Accordingtotheenergybalance
47、oftheturbocharger,equation(6)canbeobtained.Wc=hmWc6PInequation(6),hnisthemechanicalefficiencyoftheturbocharger.Thetheoreticalpoweroutputofthepowerturbine(WPT)iscalculatedusingequation(7).k4lWpT=hprm5Cp.5To5I(p6=p05)m1Pwherem$isexhaustmassflowratethroughthepowerturbine;cp,5isthespecificheatatconstant
48、pressureoftheexhaust;h11istheefficiencyofthepowerturbine;To5isthetotaltemperatureatthepowerturbineinlet;POSandp6isthetotalpressureatthepowerturbineinletandstaticpressurealthepowerturbineexit,respectively.TheaccuracyoftheGT-POWERsimulationmodelinFigure3isverifiedbyexperimentaldata.ThecomparisonbetweenthesimulationresultsandexperimentalresultsisshowninFigure4.Regardingtheenginetorqueandspecificfuelconsumption,itisshownthatthedifferencesarewithin5%betw
