Investigation of Partially Premixed Combustion in an Optical Engine In-Cylinder Flow and Combustion Characterization Tanov, Slavey 2017 Document Version: Publisher's PDF, also known as Version of record Link to publication Citation for published version (APA): Tanov, S. (2017). Investigation of Partially Premixed Combustion in an Optical Engine: In-Cylinder Flow and Combustion Characterization. [Doctoral Thesis (compilation), Combustion Engines]. Energy Sciences, Lund University. 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LUND UNIVERSITY PO Box 117 221 00 Lund +46 46-222 00 00 Investigation of Partially Premixed Combustion in an Optical Engine Investigation of Partially Premixed Combustion in an Optical Engine In-Cylinder Flow and Combustion Characterization bySlavey Tanov Doctoral Thesis Thesisadvisor: ProfessorÖivindAndersson Facultyopponent: ProfessorFabriceFoucher,Universitéd’Orléans,France Tobepresented,withthepermissionoftheFacultyofCombustionEnginesofLundUniversity,forpublic criticismintheM:BlecturehallattheDepartmentofEnergySciencesonFriday,thethofJuneat :. Organization Documentname LUNDUNIVERSITY DOCTORALDISSERTATION DepartmentofEnergySciences Dateofdisputation Box -- SE–LUND Sponsoringorganization Sweden Author(s) SlaveyTanov Titleandsubtitle InvestigationofPartiallyPremixedCombustioninanOpticalEngine:In-CylinderFlowandCombustionChar- acterization Abstract Thedieselengineisoneofthemosteconomicpowersourcesandisthereforeusedinarangeoftechnicalsolutions. Thelowfuelconsumptioncombinedwithhighengineperformancemakesitattractivefortransportationvehicles. Theyarerelativelyunproblematicintermsofemissionsofcarbon-monoxideandhydrocarbonsbut,ontheother hand,theyareassociatedwithhighemissionsofnitrogenoxidesandsoot. Intheatmosphere,theseemissions constituteaseriousconcernforbothhumanhealthandtheenvironment.Forthisreason,therecentresearchand developmenteffortsofmanyautomakersandresearchinstituteshaveshiftedfocustonewtechnologiessuchas advancedcombustionconcepts. Partiallypremixedcombustion(PPC)isoneofthenovelcombustionconcepts thataimtoyieldlowNOxandsootemissionswhilemaintaininghighengineefficiency.Thiscombustionprocess belongstoaclassoftechnologiescalledlowtemperaturecombustionconcepts.Inconventionaldieselcombustion, thecombustionispromptlyinitiatedbyauto-ignitionasfuelisinjectedintothecylinder,vaporizes,mixes,and reactswithhotair.InPPC,bycontrast,allthefuelisinjectedbeforeitauto-ignites,whichismadepossiblebythe distributionofmixturestrengths(fuelstratification)priortocombustion.ThePPCprocesscombinedwithhigh 21 exhaust-gasrecirculation(EGR)ratesgiveslowercombustiontemperaturesandthusreducestheNOxemissions 1 4 andsootformation. 1 6 Allthecombustionoccursinpremixedmode,whichmainlymeansinmixturepacketsthathavemixedwith nlSIS oxygentodifferentdegreesduringtheignitiondelay. Theignitiondelayiscontrolledbytemperature,charge De composition,fueltypeandfuelinjectiontiming.Theworkpresentedinthisthesisisexperimentalinvestigationsto BLA understandthein-cylindercombustionandfuel–airmixingprocessundergasoline-PPCconditions.Thefirstpart ATA describesanewapproachtodeterminethein-cylindercombustionstratificationforvariousinjectionsstrategies. NTD Thesecondpartisdevotedtothein-cylinderfluidmotionwhichisimportantforthefuel-airmixing,heattransfer, ME combustion,andemissionformationprocesses. Forthesetwoparts,anopticalengineisusedtocarryoutthe KU experimentalinvestigations.Thelastpartconsistsofmulti-cylinderexperimentswheretheengineisfuelledwith O D ablendbetweengasolineandethanolandcombustionisstudiedthroughanendoscope.Differentstrategieswere usedtomaintainstablecombustionandrelativelylowemissionsofsootunderPPCconditions. Keywords PPC,In-CylinderFlow,Gasoline,Gasoline-Ethanol,OpticalDiagnostic,MultipleInjection,StratificationLevel Classificationsystemand/orindexterms(ifany) Supplementarybibliographicalinformation Language English ISSNandkeytitle ISBN ----(print) ---- (pdf) Recipient’snotes Numberofpages Price  Securityclassification I,theundersigned,beingthecopyrightowneroftheabstractoftheabove-mentioneddissertation,herebygrantto allreferencesourcesthepermissiontopublishanddisseminatetheabstractoftheabove-mentioneddissertation. Signature Date -- Investigation of Partially Premixed Combustion in an Optical Engine In-Cylinder Flow and Combustion Characterization bySlaveyTanov Doctoral Thesis Thesisadvisor: ProfessorÖivindAndersson Facultyopponent: ProfessorFabriceFoucher,Universitéd’Orléans,France Tobepresented,withthepermissionoftheFacultyofCombustionEnginesofLundUniversity,forpublic criticismintheM:BlecturehallattheDepartmentofEnergySciencesonFriday,thethofJuneat :. A doctoral thesis at a university in Sweden takes either the form of a single, cohesive re- searchstudy(monograph)orasummaryofresearchpapers(compilationthesis),whichthe doctoralstudenthaswrittenaloneortogetherwithoneorseveralotherauthor(s). Inthelattercasethethesisconsistsoftwoparts. Anintroductorytextputstheresearchwork intocontextandsummarizesthemainpointsofthepapers. Then,theresearchpublications themselves are reproduced, together with a description of the individual contributions of theauthors. Theresearchpapersmayeitherhavebeenalreadypublishedoraremanuscripts atvariousstages(inpress,submitted,orindraft). Fundinginformation: TheresearchleadingtotheseresultshasreceivedfundingfromthePeople Programme(MarieCurieActions)oftheEuropeanUnion’sSeventhFrameworkProgrammeFP/- /underREAgrantagreementn°. © SlaveyTanov FacultyofCombustionEngines,DepartmentofEnergySciences isbn: ----(print) isbn: ---- (pdf) issn: <-> PrintedinSwedenbyMedia-Tryck,LundUniversity,Lund TiefverbundenunddankbarbinichmeinenElternundmeinenBruderfürdieunermüdliche UnterstützungbeiderErstellungdieserDoktorarbeit. Abstract Duetothestrongfocusonemissionreductionandimprovingfueleconomyinthetrans- portsector,manyresearchersexploreanddevelopvariousadvancedcombustionstrategies. Partially premixed combustion (PPC) is a novel strategy to face these major challenges, whichhasreceivedincreasedattention. ThegoalofthePPCprocessistoachievesufficient pre-mixingbetweenthefuelandairtoavoidsootformation,andtomaintaincombustion temperatureslowenoughtoreducethermalNO formationbyusinghighEGRrates. Due x to its potential to simultaneously reduce soot and NO , PPC may reduce the demand on x exhaustaftertreatmentsystemsinmotorizedvehicles. Stratificationofboththechargeand temperatureareimportantforachievingPPC.Theycanbeachievedbyadvancingthefuel injection into the cylinder, and by controlling the composition of the fuel-air mixture to promoteauto-ignition. Intermsofstratificationlevels,PPCrangesbetweenthefullyho- mogeneous(lessstratified)HCCIconceptandtheconventionaldieselcombustion(highly stratified). By utilizing proper fuel injection and dilution strategies, the combustion is controlled so that excessive heat-release rates can be avoided. The work presented in this thesis are experimental investigations of the in-cylinder combustion and fuel–air mixing processes under PPC conditions. The objective is to gain information and better under- standingofhowthecombustionstratificationlevelandthein-cylinderturbulentflowfields affect combustion and emission formation. The last stage of the research mainly focused onthedetailedstudyofdifferentEGRsettingsatvariousair-fuelratiostocharacterizethe gasolinePPCconcept. Usingsplitinjectionshastheadvantagesofreducingthemaximumheatreleaserate, thus reducingthecombustionnoise,aswellasextendingtheoperablerange. Ontheotherhand, splitinjectionscanleadtoincreasedUHCandCOemissions. Multipleinjectionstrategies also provide flexibility concerning the fuel stratification, which is used in this thesis to extendtheignitiondelayforenhancedfuel-airmixingpriortothestartofcombustion. Inthefirstmeasurements,OH*chemiluminescencewasimagedinthecylinderofanop- tical engine to study the combustion process throughout the cycle and to analyze the de- greeofstratification. HotresidualgasesweretrappedbyusingNVOtodilutethecylinder mixture. TheresultsclarifythemechanismscontrollingthePPCenergyrelease. Chemilu- minescenceimagingshowsthatPPCfeaturesahightemperaturereactionzonethatappears togrowbytheappearanceofsmallauto-ignitionregions. Therateofreactionzonegrowth is controlled by the stratification level. Going from single injections to a triple injection strategy, a distinct change in the stratification is seen, which is also apparent in the heat releaserate. Turbulentflowstructureswithinthecylinderareessentialtothemixturepreparation,com- bustion, andpollutantformationinlight-duty(LD)direct-injectiondieselengines. Both i