performance evaluation of low heat rejection diesel · pdf fileinvestigations are carried out...

INTERNATIONALJOURNALOFAPPLIEDENGINEERINGRESEARCH,DINDIGULVolume1,No 3,2010
Copyright2010AllrightsreservedIntegratedPublishingAssociation
REVIEWARTICLE ISSN09764259
428
PerformanceEvaluationofLowHeatRejectionDieselEnginewithPureDiesel
Murthy P.V.K1,MuraliKrishnaM.V.S.2,SitaramaRajuA3, VaraPrasadC.M.4SrinivasuluN.V.2
1 VivekanandaInstituteofScienceandInformationTechnology,Shadnagar,Mahabubnagar
2 MechanicalEngineeringDepartment,ChaitanyaBharathiInstituteofTechnology,Gandipet,Hyderabad.
3 MechanicalEngineeringDepartment,J.N.T.University,Kukatpally,Hyderabad
4SreenidhiInstituteofScienceandTechnology,NaYampet,GhatkeswarMandal,Hyderabad
[email protected]
ABSTRACT
Investigations are carried out to evaluate the performance of a low heat rejection (LHR)dieselengineconsistingofairgapinsulatedpistonwith3mmairgap,withsuperni(analloyofnickel)crown,airgapinsulatedlinerwithsuperniinsertandceramiccoatedcylinderheadwithpuredieseloperationwithvaried injection timingand injectionpressure.Performanceparametersaredeterminedatvariousmagnitudesofbrakemeaneffectivepressure.Pollutionlevelsofsmokeandoxidesofnitrogen(NOx)arerecordedatthepeakloadoperationoftheengine.Combustioncharacteristicsof theengine aremeasuredwithTDC(topdeadcentre)encoder, pressure transducer, console and special pressurecrank angle software package.Zero dimensional, multizone combustion model is assumed to predict combustioncharacteristics and validated with experimental results. LHR engine showed deterioratedperformance at recommended injection timing and pressure and improved performance atadvanced injection timing and higher injectionpressure,when comparedwith conventionalengine(CE).Atpeakloadoperation,brakespecificfuelconsumption(BSFC)decreasedby12%,whilesmokelevelsby16%andNOxlevelsincreasedby34%withLHRengineataninjectiontimingof32obTDC(beforetopdeadcentre)andaninjectionpressureof270bars,incomparisonwithCEoperatingataninjectiontimingof27obTDC,andaninjectionpressure
of190bars.
Keywords: Low heat rejection, Performance, Pollution levels, Combustion characteristics,Zerodimensionalmultizonecombustionmodel.
NOMENCLATURE
aConstantusedinAnnandsequationA Totalheattransfersurfaceareainm2b ConstantusedinAnnandsequationBDCBottomDeadCentreBMEP BrakemeaneffectivepressureinbarBSFC Brakespecificfuelconsumptioninkg/hkWbTDC Beforetopdeadcentre

429
BTEBrakethermalefficiencyinpercentagec ConstantusedinAnnandsequationCEConventionalengineCV CalorificvalueofthefuelinkJ/kg.Dl Cylinderboreinmetredn DiameterofnozzleinmetreDsm SautermeandiameteroffuelparticleinmicrometersEGT ExhaustgastemperatureinoCHSUHartridgesmokeunitsIVCInletvalveclosingJ TotalnumberofradialdivisionsK ThermalconductivityinW/mKL LatentheatofevaporationoffuelinJ/kg,LHRLowheatrejectionM MassMRPRMaximumrateofpressureriseinbar/degreeN/ NumberofdropletsNOx OxidesofnitrogenO/F OxygentofuelratioO2 OxygenPPressureinmegaPascalP()InstantaneousgaspressureinbarPhiEquivalencefuelairratioPPPeakpressureinbarQHeattransferinW
1injQ Amountoffueldeliveredpercyclepersecondinm3 /sec
R GasconstantinkJ/kgKR UniversalgasconstantkJ/K,r RadialcoordinateofcylindricalcoordinatesystemRe Reynoldsnumberrs Radiusofdropletinmicrometers,SMD SautermeandiameterofdropletinmicronsTSurroundingtemperatureinKelvintbu BrakeuptimeforelementinsecTDCTopDeadCentreTl TemperatureofliquidfuelinKelvin.TOMRPRTimeofoccurrenceofmaximumrateofpressureriseindegrees
TOPP Timeofoccurrenceofpeakpressureindegrees
TRTheoreticalResultthroughComputerPredictionTw WalltemperatureinKelvin
tIgnitiondelayofgaseousmixture
VVolumeordomainVVelocityinm/sV1inj Velocityofinjection

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VEVolumetricefficiencyinpercentageVdis Displacementvolumeinm3W MolecularweightXij SpraytippenetrationinaxialdirectioninmetersY Massfractionofchemicalspecies27obTDCManufacturersrecommendedinjectiontiming190barsManufacturersrecommendedinjectionpressure
Subscripts
a airaeAirentrainmentb burntbu brakeupc combustiondisDisplacemente entrainmentfFuelggasfgGaseousfuelhcylinderheadi indexforanelementintheaxialdirectioninjinjectionj indexforanelementintheradialdirectionlliquidLLatentheatofvaporizationliLinerNS Indexforchemicalspeciesvaryfrom1to5referringtofuel
(Referringtothefuel,O2,N2,CO2andH2Orespectively)nnetoreferencestatep PistonStStoichiometricratiossurfaceofdropletuunburntvvaporw wall298DatumtemperatureinKelvin
Greeksymbols Crankangleindegrees Differential DynamicviscosityinNs/m2
Correspondingtochangeinaquantity i Crank anglecorrespondingtothelocationofthepackage o Crankanglecorrespondingtoonecompletecycleindegrees

431
Spaldingnumber a Densityofairinkg/m3
g Gasdensityinkg/m3
l Liquiddensityinkg/m3
s Densityofdropletinkg/m3
Ignitiondelayinmilliseconds
1.Introduction
In thescenarioof increaseofvehiclepopulationatanalarmingrateduetoadvancementofcivilization, use of diesel fuel in not only transport sector but also in agriculture sectorleading to fast depletion of diesel fuels and increase of pollution levels with these fuels,efficient fuel utilization has become pertinent for the engine manufacturers, users andresearchers involved in the combustion research. While search for alternate fuels iscontinuing, researchers are also attempting to find different techniques of efficient fuelutilizationindieselengines.
Itiswellknownfactthatabout30%oftheenergysuppliedislostthroughthecoolantandthe30%iswastedthroughfrictionandotherlosses,thusleavingonly30%ofenergyutilizationforusefulpurposes.Inviewoftheabove,themajorthrustinengineresearchduringthelastoneortwodecadeshasbeenondevelopmentofLHRengines.SeveralmethodsadoptedforachievingLHRtothecoolantarei)usingceramiccoatingsonpiston,linerandcylinderheadii) creating air gap in the piston and other components with lowthermal conductivitymaterialslikesuperni,castironandmildsteeletc.Krishnaneal.andWadeetal.observedin improvement in thermal efficiency with ceramiccoated component with diesel as fuel.Woschnietal.andColeetal.reportedreductioninBSFCwithanairgapinsulatedpistonatpart loads. Creating an air gap in the piston involved the complications of joining twodifferentmetals.ThoughParkeretal. observedeffective insulationprovidedbyanairgap,thebolteddesignemployedbythemcouldnotprovidecompletesealingofairintheairgap.Rama Mohan made a successful attempt of screwing the crown made of low thermalconductivitymaterial, nimonic (an alloy of nickel) to the body of thepiston, by keeping agasket,madeofnimonic,inbetweenthesetwoparts.
TheconceptofLHRengineistoreduceheatlosstocoolantandthattoospecificallyfromthepiston topto thebodyof thepiston. It shouldbeexpectedthat the thicknessof theairgapplayanimportantroleontheinsulationeffectinLHRengines.RamaMohanandDhinagaretal.workedinthisdirectioninordertogethigherinsulationeffect.Inordertoincreasethedegreeoftheinsulation,airgapisnotonlycreatedinthepistonbutalsointheliner.MuraliKrishna conductedexperimentsonLHRenginewhichconsistedofairgapinsulatedpistonwith supernicrownandairgap insulated linerwith superni insert withadvanced injectiontimingsandincreasedinjectionpressurewithdifferentalternatefuels likealcoholsandnonediblevegetableoilandreportedimprovedperformancewithLHRengine.WhileSeiglaetal.andMiyairi et al. found deterioration of the engine performance with retarded injectiontimings, Dhinagar et al. claimed improved performance with retarded injection timing inLHRenginewithdieselasfuel.

432
The complexities involved like heterogeneous combustion of diesel fuel and air inminutefraction of time, various sizes of fuel droplets and their penetration and evaporation etc.,makedieselcombustionusuallynotamenableforeffectivemodelling.Miyairi useda twozone combustion model and a computer simulation model was used byRafiqulIslametalforpredictingtheperformanceoftheceramiccoateddirectinjection(DI)dieselengines.RamamohanetalandMuraliKrishnaemployedzerodimensionalmultizonecombustion models for predicting the performance of the LHR engine and validated thetheoreticalresultswithexperimentaldataandfound57%deviationbetweenthesetwo.
Thepresentpaperattempts toevaluate theperformanceofLHRengine,whichcontainsairgap insulatedpiston,air gap insulated liner andceramic coated cylinderheadwith varyingengine parameters of changeof injection pressure and injection timing andcomparedwithCEatrecommendedinjectiontimingandinjectionpressure.Anattemptismadetodevelopazero dimensional, multizone combustion model and correlate theoretical analysis withexperimentalresults.
2.ExperimentalProgramme
Figure1givesthedetailsofinsulatedpiston,insulatedlinerandceramiccoatedcylinderheademployed in the experimentation. LHR diesel engine contains a twopart piston the topcrownmadeoflowthermalconductivitymaterial,superni90screwedtoaluminumbodyofthepiston,providinga3mmairgap inbetween thecrownand thebodyof thepiston.Theoptimum thickness of air gap in the air gap piston is found to be 3mm [6], for betterperformance of the engine with superni inserts with diesel as fuel. A superni90 insert isscrewedtothetopportionofthelinerinsuchamannerthatanairgapof3mmismaintained

performance evaluation of low heat rejection diesel · pdf fileinvestigations are carried out...

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