THREE DIMENSIONAL ANALYSIS OF THE GAS FLOW IN PISTON RING PACK By Ali Kharazmi A

132 Pages·2017·13.51 MB·English

THREEDIMENSIONALANALYSISOFTHEGASFLOWINPISTONRINGPACK
By
AliKharazmi
ADISSERTATION
Submitted
toMichiganStateUniversity
inpartialfulfillmentoftherequirements
forthedegreeof
MechanicalEngineering–DoctorofPhilosophy
2017
ABSTRACT
THREEDIMENSIONALANALYSISOFTHEGASFLOWINPISTONRINGPACK
By
AliKharazmi
Cylinder-kit dynamics design in an internal combustion engine is highly relevant for the engine
performance characteristics, durability and reliability. Since the middle of the 20th century, re-
searchers have been using numerical models to describe the processes that occur in a ring pack.
Because it is difficult and extremely costly to conduct experiments on every series of engines to
checkfortheblow-byandoilconsumption,acomputationalanalysiscanbeperformedonthering
packtostudytheblow-byandoil-consumptioncharacteristics.
In this dissertation a 3D CFD simulation model is introduced to analyze the flow between the
cylinderlinerandthepiston. Thismodelallowsforcalculationofthepistonassemblywithconsid-
eration of the ring dynamics, transient boundary conditions for combustion chamber pressure and
temperatureaswellasthermaldistortionofthepistonandliner. Thedeterminationofthecomplex
geometry of the cylinder-kit is established in a STL (STereoLithography) format by considering
the complicated geometrical details of the ring pack such as thermal distortion of piston and liner,
ring twist and ring/groove conformability. The blow by and blow back is numerically calculated
forasmallborecylinderoperatingat2000RPMandverifiedbytheresultsofcommerciallyavail-
able1Dmodels.
Thecalculatedvelocityfiledshowssubstantialcircumferentialflowinthepistonringpackthat
isdominatedbytheringandgroovegeometryaswellastherelativepositionoftheringsendgap.
It is found that the amount of gas that flows back to the combustion chamber increases when the
in-cylinder pressure trace decreases from its peak value. The knowledge from this study can be
usedasabasisforfurthermultiphasecalculationscontainingoilflowsuchasoilconsumption,oil
evaporationandeventuallycylinder-kitwear.
Copyrightby
ALIKHARAZMI
2017
Thisthesisisdedicatedtomyparentsfortheirconstantsupportandunconditionalloveandtomy
grandfatherwhotaughtmehowtolivelifetothefullest
iv
ACKNOWLEDGMENTS
I would like to thank my committee members for their guidance and constructive advices. In par-
ticular,IwouldliketothankmythesissupervisorDr. HaroldJ.Schock,whonotonlygavemethe
opportunity to conduct my doctoral studies at Michigan State University, but also supported and
guided me consistently through his insightful and broad knowledge. I enjoyed and will remem-
ber every single discussion with him, which helped me to solve the problems I encountered and
eventually leaded to the achievement of my thesis work. Besides being a respectable advisor, Dr.
Schock has been the most instructive and supportive friend during my time at MSU. I would also
like to express my gratitude to Professor Farhad Jaberi for the continuous help over the years, es-
peciallyhisadvicesonComputationalfluiddynamics. MysincerelythankstoProfessorGuoming
ZhuandProfessorCarlLiraforacceptingbeingpartofthecommitteeanddelightfulsuggestions.
IwouldliketothankthepeoplefromCumminsincludingDr. DanRichardonandMr. William
D.McNulty,whomIhavetheopportunitytoworkwith. AlsoIwouldliketotakethisopportunity
to thank the passionate and gifted engineer Dr. Chao Cheng from Cummins for his supports and
invaluablesuggestionsthroughouttheyearsaswellashisguidanceinunderstandingthemodeling
techniquesinCASE.
My deep appreciation goes out to my friends and colleagues: Ravi Vedula, Sedigheh Tolou,
Tom Stuecken, Brian Rowley, Jenny Higel and Jeff Higel. They have made the lab a fun place to
workandhavebeenalwaystheretosupportme.
Last but not the least, I would like to thank my family: my parents and to my brothers for
their encouragements trust and faith. This thesis would not have been completed without their
unconditionalsupport.
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TABLEOFCONTENTS
LISTOFTABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LISTOFFIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
CHAPTER1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Structureofthisdissertation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
CHAPTER2 INTERNALCOMBUSTIONENGINES . . . . . . . . . . . . . . . . . . . 4
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Cylinderkitassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Pistonskirtandringgroove . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4 Pistonringdesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.5 Gasflowthroughringpack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.6 Blow-by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.7 Interringgasanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.8 Pistonringflutter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.9 Pistonringcollapse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.10 Pistonringtwist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.11 Pistonringlubrications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.12 Threedimensionalgasflowanalysis . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.13 Previousefforts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
CHAPTER3 DEVELOPMENTOFALINKPROGRAM . . . . . . . . . . . . . . . . . 33
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2 LINKprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2.1 OverviewoftheGeometryinSTLformat . . . . . . . . . . . . . . . . . . 34
3.2.2 GeometryofCylinderKitAssemblyinSTLformat . . . . . . . . . . . . . 35
3.2.3 Modificationofsurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.4 Ringconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.5 Pistonconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2.6 CylinderLinerconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2.7 FinalAssemblyofthegeometry . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 Simulationmethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.4 Geometryoftheproposedproblem . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.4.1 In-cylinderpressure"Binning" . . . . . . . . . . . . . . . . . . . . . . . . 47
3.4.2 Governingequations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.3 Boundaryconditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.4.4 Gridgeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.4.4.1 2Dand3DGeometriesgrid . . . . . . . . . . . . . . . . . . . . 55
3.5 Simulationtimeofthe3Dgeometry . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.6 Parallelcomputing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
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3.6.1 Classificationofparallelcomputerarchitecture . . . . . . . . . . . . . . . 67
3.6.2 Issuesinparallelcomputing . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.6.3 Scalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.6.4 ParallelprocessinginCONVERGE . . . . . . . . . . . . . . . . . . . . . 70
CHAPTER4 RESULTSANDDISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . 74
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.1.1 Testrun1(Narrowchannel) . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.1.2 Testrun2(HollowCylinder) . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.1.3 Testrun3(ChannelwithObstacle) . . . . . . . . . . . . . . . . . . . . . . 78
4.2 CylinderkitassemblyResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2.1 2DResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2.2 2DVelocityProfile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.2.3 2DBlow-Bycalculation . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.2.4 3D-Steadyresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.2.4.1 Convergenceoftheresults . . . . . . . . . . . . . . . . . . . . . 88
4.2.4.2 Pressuredistribution . . . . . . . . . . . . . . . . . . . . . . . . 92
4.2.4.3 Circumferentialflow . . . . . . . . . . . . . . . . . . . . . . . . 94
4.2.4.4 Blow-bycalculation . . . . . . . . . . . . . . . . . . . . . . . . 97
4.2.5 3D-Unsteadyresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4.2.5.1 Blow-bycalculation . . . . . . . . . . . . . . . . . . . . . . . . 101
4.2.5.2 Blow-back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.3.1 Wallclocktime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.3.2 Flowstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
4.3.3 Blow-byandblow-backs . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
CHAPTER5 SUMMARY,CONCLUSIONSANDFUTUREWORK . . . . . . . . . . . 107
5.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.2 Futurework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.2.1 Simplifyingthegeometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.2.2 Alternativemethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
5.2.3 FluentastheCFDsolver . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
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LISTOFTABLES
Table3.1 Gridspecificationfor2Dcylinder-kitassembly . . . . . . . . . . . . . . . . . . 56
Table3.2 Gridspecificationfor3Dcylinder-kitassembly . . . . . . . . . . . . . . . . . . 61
Table3.3 Simulationtimefordifferentgridlevelsofbin#1inletpressure . . . . . . . . . 66
Table3.4 Flynn‘sTaxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Table4.1 Gridsystemsusedfortestrun1-Narrowchannel . . . . . . . . . . . . . . . . . 75
Table4.2 Gridsystemsusedfortestrun2-Hollowcylinder . . . . . . . . . . . . . . . . . 77
Table4.3 Pressurebinsafterbinningprocess . . . . . . . . . . . . . . . . . . . . . . . . . 83
Table4.4 Comparisonbetweenthe3D-steadyandCASEpressureresults(pressuresare
inkPa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Table4.5 Calculatedmassflowrateforeachbinpressure . . . . . . . . . . . . . . . . . . 99
Table4.6 Calculateddischargedmassforeachbinpressure . . . . . . . . . . . . . . . . . 99
viii
LISTOFFIGURES
Figure2.1 Schematicviewofatypicalcylinderkitassembly . . . . . . . . . . . . . . . . 5
Figure2.2 Pistonterminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure2.3 Schematicviewofapistonandpistonringpackassembly . . . . . . . . . . . . 8
Figure2.4 Variouspistonringcrosssections . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure2.5 Ringendgapsandclearances . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure2.6 CompressionRingterminology . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure2.7 Pistonringfreeshape(camshape) . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure2.8 Detailedschematicviewofcrevicevolumesinringpacks . . . . . . . . . . . . 15
Figure2.9 Gasflowthroughcrevicesandlocationofblow-by . . . . . . . . . . . . . . . . 15
Figure2.10 Conceptualdiagramofthegasflowmodelinthepistonrigpack . . . . . . . . 17
Figure2.11 Forcesactingonapistonringinsidearinggroove . . . . . . . . . . . . . . . . 18
Figure2.12 RingFlutterScenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure2.13 Gaspressureontheringwithpositiverelativeangleshowingcollapsescenario . 21
Figure2.14 Positivetwistofthetopring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure2.15 Negativetwistofthe2nd ring . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure2.16 Crosssectionoftheoilfilmbetweenthepistonringandcylinderliner . . . . . 24
Figure2.17 Flowofthegasthroughtheringendgapusingorifice-volumemethod . . . . . 27
Figure2.18 Calculatedgeometryofadeformed(twisted)Pistonring . . . . . . . . . . . . . 31
Figure3.1 Orientationofafacetanditsnormalvector . . . . . . . . . . . . . . . . . . . . 34
Figure3.2 Vertextovertexrule-theleftfigureistheviolationofthisrule . . . . . . . . . 35
Figure3.3 AcuberepresentedinSTLformat . . . . . . . . . . . . . . . . . . . . . . . . 35
Figure3.4 Geometryofcylinder-kitassemblyinSTLformat . . . . . . . . . . . . . . . . 36
Figure3.5 Exampleofoverlapsurfacescondition . . . . . . . . . . . . . . . . . . . . . . 37
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Figure3.6 Exampleofoverlappointscondition . . . . . . . . . . . . . . . . . . . . . . . 38
Figure3.7 Topviewofainstalledpistonringinabore . . . . . . . . . . . . . . . . . . . 38
Figure3.8 Topviewofasliceofapistonringinstalledinabore . . . . . . . . . . . . . . 39
Figure3.9 Anarbitrarynon-touchingringcrosssection . . . . . . . . . . . . . . . . . . . 39
Figure3.10 Anarbitrarytouchingringcrosssection . . . . . . . . . . . . . . . . . . . . . 39
Figure3.11 Pistonringelementtypes. Fromlefttoright1)TT2)TN3)NT4)NN . . . . . . 40
Figure3.12 Frontviewofasliceofapistonringconstructedbyringelementconcept . . . . 40
Figure3.13 Differentcrosssectionsoftheportionofapistonring . . . . . . . . . . . . . . 41
Figure3.14 Crosssectionofapiston . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Figure3.15 ConstructedpistoninSTLformat . . . . . . . . . . . . . . . . . . . . . . . . . 42
Figure3.16 3Drepresentationofacompletedcylinderkitassembly . . . . . . . . . . . . . 43
Figure3.17 Crosssectionofthestudiedgeometry(unitsaremm) . . . . . . . . . . . . . . . 46
Figure3.18 2D-cutofthecylinder-kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Figure3.19 Complete3Dcylinder-kitgeometry(sectioned) . . . . . . . . . . . . . . . . . 47
Figure3.20 Pressuretracecurve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Figure3.21 Binnedpressuretrace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Figure3.22 Schematicviewoftheboundaryconditions . . . . . . . . . . . . . . . . . . . . 54
Figure3.23 Anexampleofgridembedding(a)beforeand(b)after . . . . . . . . . . . . . . 55
Figure3.24 Gridaroundring1-CaseNo. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Figure3.25 Gridaroundring1-CaseNo. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Figure3.26 Gridaroundring1-CaseNo. 3 . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Figure3.27 Gridaroundring1-CaseNo. 4 . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Figure3.28 Gridaroundring2-CaseNo. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Figure3.29 Gridaroundring2-CaseNo. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 59
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