Investigation of Partially Premixed Combustion in an Optical Engine In-Cylinder Flow and ...

105 Pages·2017·60.4 MB·English

Investigation of Partially Premixed Combustion in an Optical Engine
In-Cylinder Flow and Combustion Characterization
Tanov, Slavey
2017
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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.
Total number of authors:
1
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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
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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