文獻出處：ChauhanBS,KumarN,ChoHM.AstudyontheperformaneeandemissionofadieselenginefueledwithJatrophabiodieseloilanditsblends[J].Energy,2012,37(1):616-622.AstudyontheperformanceandemissionofadieselenginefueledwithJatropha

biodieseloilanditsblendsChauhanBS,KumarN,ChoHMAbstractBiodieseleitherinneatformorasamixturewithdieselfueliswidelyinvestigatedtosolvethetwinproblemofdepletionoffossilfuelsandenvironmentaldegradation.Themainobjectiveofthepresentstudyistocompareperformance,emissionandcombustioncharacteristicsofbiodieselderivedfromnonedibleJatrophaoilinadualfueldieselenginewithbaselineresultsofdieselfuel.Theperformanceparametersevaluatedwere:brakethermalefficiency,brakespecificfuelconsumption,poweroutput.Asapartofcombustionstudy,in-cylinderpressure,rateofpressureriseandheatreleaserateswereevaluated.Theemissionparameterssuchascarbonmonoxide,carbondioxide,un-burnthydrocarbon,oxidesofnitrogenandsmokeopacitywiththedifferentfuelswerealsomeasuredandcomparedwithbaselineresults.ThedifferentpropertiesofJatrophaoilaftertransestrificationwerewithinacceptablelimitsofstandardsassetbymanycountries.ThebrakethermalefficiencyofJatrophamethylesteranditsblendswithdieselwerelowerthandieselandbrakespecificenergyconsumptionwasfoundtobehigher.However,HC,COandCO2andsmokewerefoundtobelowerwithJatrophabiodieselfuel.NOxemissionsonJatrophabiodieselanditsblendwerehigherthanDiesel.TheresultsfromtheexperimentssuggestthatbiodieselderivedfromnonedibleoillikeJatrophacouldbeagoodsubstitutetodieselfuelindieselengineinthenearfutureasfarasdecentralizedenergyproductionisconcerned.Inviewofcomparableengineperformanceandreductioninmostoftheengineemissions,itcanbeconcludedandbiodieselderivedfromJatrophaanditsblendscouldbeusedinaconventionaldieselenginewithoutanymodification.Keywords:Biodiesel;Brakethermalefficiency;Exhaustmissions;Transesterification1.IntroductionInthewakeofcurrentenergyscenario,majorresearchisfocusedonsustainableenergysolutionwithmajoremphasisonenergyefficiencyanduseofrenewableenergysources.Dieselengineshaveproventheirutilityinthetransportationandpowersectorsduetotheirhigherefficiencyandruggedness.Theyarealsopotentialsourcesofdecentralizedenergygenerationforsmallelectrificationplant.However,concernsaboutlong-termavailabilityofpetroleumdieselandthestringentenvironmentalnormshavemandatedthesearchforarenewablealternativetodieselfueltoaddresstheseproblems.Liquidbio-originfuelsarerenewablefuelscomingfrombiologicalsourcesandhaveprovedtobeagoodsubstituteforpetroleumderivedoilintransportationandsmallenergyneeds.Thesefuelsaregainingworldwideacceptanceasasolutionforproblemofenvironmentaldegradation,energysecurity,restrictingimport,ruralemploymentandagriculturaleconomy.Alargevarietyofalternativefuelsareconsideredpotentialsubstitutetopetroleumbaseddiesel,however,modification,handlingandtransportation,easeofproduction,andinvestmentcostaresomeoftheimportantparametersthatshouldbeconsideredbeforeusinganalternativefuelinanexistingdieselengine.Themodificationrequiredintheenginedesignneedtobemadeinsuchawaysoastominimizetheinvestmentcostintheenginemodification[3].Overthepastfewyears,hugefluctuationinoilpriceshavebeenseen,reachingtorecord$147.27in2008ofandthenfallingbackagainto$33.87inDecember2008.Evenso,overthewholeof2009,theaverageoilpricewasstillbetween$60and$80perbarrel.In2009,thetotallevelofannualinvestmentincleanenergywas$145billion,onlya6.5%dropfromtherecordpreviousyear,whiletheglobalwindpowermarketgrewbyanannual41.5%.Oilremainsthehighestconsumedsourceofenergyintheworld.Today,renewableenergysourcesaccountfor13%oftheworld'sprimaryenergydemand.Biomass,whichismostlyusedintheheatsector,isthemainsourceofrenewableenergy.Theshareofrenewableenergiesforelectricitygenerationis18%,whiletheircontributiontoheatsupplyisaround24%.About80%oftheprimaryenergysupplytodaystillcomesfromfossilfuels.Inthelightofabove,thereis anurgentneedtoreducedependenceonpetroleumderivedfuelsforbettereconomyandenvironment.Themostpromisingliquidbiofuelsclosesttobeingcompetitiveincurrentmarketswithout subsidy, areethanol, methanol,vegetableoilsandbiodiesel.Theyhavebeenutilizedeitherinoneformor anotherformorethanonehundredyears.Thesearchforalternativefueloverconventionalpetroleumbasedfuelshasbeensubjectedtovariousstudiesthroughouttheworld.Thermodynamictests,basedonengineperformanceevaluationhaveestablishedthefeasibilityofusingavarietyofalternativefuelssuchashydrogen,alcohols,biogas,producergasandhostofvegetableoils.Biodieselisconsideredasustainablesubstitutetodieselfuelduetoitsrenewablenatureandpositiveenvironmentalimpact.Dependingupontheavailabilityandproductioncapabilities,biodieselisderivedfromalargevarietyofoilseed.BiodieselderivedfromsoybeanoilisofprimaryinterestintheUnitedStateswhilemanyEuropeancountriesareconcernedwithrapeseedoil,andcountrieswithtropicalclimateprefertoutilizecoconutoilorpalmoil.InIndia,around450typesofoilbearingcropsareavailableforuseasenergycrops,andtheeffortsmustbeputtoincreasetheyieldandoilcontentofthesecrops.Inthiscontext,itisessentialtopromotetheuseofnon-ediblevegetableoilderivedfuelseitherasasubstituteoranextenderoffossilfuelswhichwouldbringenergycropsontheforefrontinenergyscenario.Consideringtheimportantparameterssuchasenergysecurity,greenhouseemission,fastdepletionoffossilfuelreserveandpotentialutilizationinexistingdieselenginewithnoorminimumdesignmodification,biodieselisconsideredmostpromisingrenewablefuelformankindandenvironment.Inthepresentstudy,nonediblevegetableoilderivedfromJatrophaplantwastransesterifiedandmajorphysico-chemicalpropertieswereevaluatedinaccordancewithASTMstandards.Further,acompressionignitionenginewasfuelledwithJatrophamethylesteranditsblendswithdieselandperformance,combustionandemissionscharacteristicswereevaluatedtofindouttheirsuitabilityasadieselenginefuel.Thestudy ofcombustion characteristicswascarriedwiththehelpofpressure-crankangleandheatreleaseratediagrams.Theresultswerecomparedwiththosefromthediesel fuel.2.NonedibleJatrophabiodieselasapotentialsubstitutefordieselfuelInrecentyears,systematiceffortshavebeenmadebyseveralresearcherstousevegetableoilsderivedfuelsindieselengines.Theoiltestedincludedanumberofdifferentrawandprocessedvegetableoilslikerapeseedoil,sunfloweroil,palmoil,soybeanoiletc.Pascaletal.studiedpalmoilinCIengineswithwastecookingoil,whichwereconvertedintoestersbyatransestrificationprocess.ThebrakethermalefficiencyincreasesforthePO/Dieselblends.HCemissionsforallthosefuelsexceptforthePO/Dieselblendsarefoundlower,whileCOemissionsriseforalltypesoffuels.NOxemissionswerehigheratlowload,butloweratfullload.Ghestudytransesterifiedapricotseedkerneloilwithmethanolusingpotassiumhydroxideascatalysttoobtainapricotseedkerneloilmethylester.Neatapricotseedkerneloilmethylesteranditsblendswithdieselfuelweretestedinacompressionignitiondieselenginetoevaluateperformanceandemissionsparameters.Kegl]discussedtheinfluenceofrapeseedbiodieselontheinjection,sprayandenginecharacteristicswiththeaimtoreduceharmfulemissions.Theresultsindicatethatbyusingbiodiesel,harmfulemissionscanbereducedtosomeextentbyadjustingtheinjectionpumptimingproperly.Sahooetal.usednon-ediblefilteredhighviscousandhighacidvaluepolangaoilbasedmonoestersblendedwithhighspeeddieselasasubstituteofdieselinasinglecylinderdieselengine.Agarwaletal.foundthatbiodiesel-fueledenginesproducelesscarbonmonoxide,unburnedhydrocarbon,andparticulateemissionscomparedtomineraldieselfuelbuthigherNOxemissions.Canakciandstudiedandcomparedthecombustioncharacteristicsandemissionsofpetroleumdieselandbiodieselfromsoybeanoil.HefoundsignificantreductionsinPM,CO,andunburnedHC,whileNOxincreasedwithsoybeanbiodiesel.Fenetal.preparedbiodieselthroughtransestrificationfromwastedcookingoilandtesteditindieselengineandconcludedthatB20andB50aretheoptimumfuelblends.Tsolakisetal.studiedtheeffectsofrapeseedmethylesteranddifferentdiesel/RMEblendsonthedieselengine'semNOisxsions,smoke,fuelconsumption,engineefficiency,cylinderpressureandnetheatreleaserateandreportedincreasedNOxemissions.Whensimilarpercentages(%byvolume)ofexhaustgasrecirculation(EGR)areusedinthecasesofdieselandRME,NOxemissionsarereducedtosimilarvalues,butthesmokeemissionsaresignificantlylowerinthecaseofRME.TheretardationoftheinjectiontiminginthecaseofpureRMEand50/50(byvolume)blendwithdieselresultedinfurtherreductionofNOxatacostofsmallincreasesofsmokeandfuelconsumption.Linetal.studiedbiodieselfromwastecookingoilasaneconomicalsourceandthusaneffectivestrategyforreducingtherawmaterialcost.UsingwastecookingoilanddieselblendsdecreasesPAHsby7.53%—37.5%,particulatematterby5.29%—8.32%,totalhydrocarbonsby10.5%—36.0%,andcarbonmonoxideby3.33%—13.1%ascomparedtousingULSD.Buenoetal.studiedtheengineperformanceimpactofsoybeanoilethylesterblendingintodieselfuelandreportedanaverageincreaseof4.16%inbrakethermalefficiencywithB20blend.Underthesameconditions,anaveragegainof1.15%inbrakepowerandareductionof1.73%inspecificfuelconsumptionwithB10blendwereobserved.Macoretal.observedadrasticreductioninCOandPMemissionswhileusingbiodieselwithrespecttohomeheatingoil.ThePAHscontainedinPM,incaseofbiodieselwerenearly13timeslesstoxicthantheoil;formaldehydeonthecontrary,wasnearlydoubleforbiodiesel.TheVOCswereverylowforboththefuels.Theresultsshowthattheremaybebenefitsinusingbiodieselinhomeheatingorinindustrialprocesses.Taymazetal.studiedtheengineperformanceandexhaustemissionsofadieseldirectinjectionengineusingmixedpalmolein/Soybeanvegetableoilethylester.Torqueandbrakepoweroutputoftheenginewhichusesbiodiesel,wereslightlylowerandspecificfuelconsumptionwashigherincomparisontoDiesel.DecreaseinCOandHC,CO2emissions,indicatesanadvantageofexhaustemissionswiththoseofdieselfuel,however,NOandNOxemissionswerehigherwiththebiodiesels.Theuseofediblevegetableoilsandanimalfatsforbiodieselproductionhasrecentlybeenofgreatconcernbecausetheycompetewithhumanfoodchain.Asthedemandforvegetableoilsforfoodhasincreasedtremendouslyinrecentyears,itisimpossibletojustifytheuseoftheseoilsasfueluseforpurposeofbiodieselproduction.Moreover,theseoilswouldbemoreexpensivetouseasfuels.Hence,thecontribution(完整文獻請到百度文庫)ofnon-edibleoilssuchasJatrophawillbesignificantforbiodieselproduction.TheadaptationofJatrophaoiltothedieselenginecouldbedonebyusingneatJatrophaoilbyadualtankapproach,blendingtheJatrophaoilwithdieselandproducingmethylorethylestersthroughtransestrificationprocess.Petroleumdieselfuelismadeupofhundredsofdifferenthydrocarbonchainsandcontainsaromatichydrocarbons,sulfurandcrudeoilresiduecontaminants.However,thechemicalcompositionofbiodieselisdifferentfromthatofpetroleumbaseddieselfuel.Thenormalstructureofhydrocarbonispreferredforbetterignitionquality.Biodieselhydrocarbonchainsaregenerally16—20carbonsinlengthandcontainoxygenatoneend.Biodieselcontainsabout10%oxygenbyweight,whichresultsinpooroxidationstability.Biodieseldoesnotcontainanysulfur,aromatichydrocarbons,metalsorcrudeoilresidues.Fatsandoilsareprimarilywater-insolublethataremadeupof1molofglyceroland3moloffattyacidsandarecommonlyreferredtoastriglycerides.Fattyacidsvaryincarbonchainlengthandinthenumberofunsaturatedbonds.Thefattyacidsfoundinvegetableoilsaresummarizedin.Someofthepropertiesofvegetableoilsaredifferentfromanimalfatsbecauseoftheirorigin.Oilfromalgae,bacteriaandfungialsohasalsobeeninvestigated].Vegetableoilsconsistof97%triglyceridesand3%asdi-andmonoglycerides].Theprocessofconvertingvegetableoilintobiodieselfueliscalledtransestrification.Chemically,transestrificationmeansthereactionoftriglyceridemoleculewithmethylalcoholinpresenceofcatalystatselectedtemperatureproducingglycerinandfattyacidmethylesters.Thereactionisshownin.Becausethereactionisreversible,excessalcoholisusedtoshifttheequilibriumtotheproductsside.Tocompleteatransestrificationstoichiometrically,a3:1molarratioofalcoholtotriglyceridesisneeded.Inpractice,therationeedstobehighertodrivetheequilibriumtoamaximumesteryield.R,RandR''arethealkylgroupsofdifferentcarbonchainlengths.Table1.Chemicalstructureofcommonfattyacids.Fatty StruFormacid Systematicname ctureula

FattyStruFormacidSystematicnamectureulaLauriDodecanoic12:C12Hc024O2MyriTetradecanoic14:C14Hstic028O2PlamHexadecanoic16:C16Hitic032O2SteariOctadecanoic18:C18Hc03602AracEicosanoic20:C20Hhidic040O2BeheDocosanoic22:C22Hnic044O2LignTeracosanoic24:C24Hoceric048O2OleicCis-9-Octadecenoic18:C18H134O2LinolCis-9,cis-12octadecenoic18:C18Heic232O2LinolCis-9,cis-12,cis-15-octadecatri18:C18Henicenole330O2EruciCis-13-Docosenoic22:C22Hc142O2Boilingpointsandmeltingpointsofthefattyacids,methylesters,mono-,di-andtriglyceridesincreasesasthenumberofcarbonatomsinthecarbonchainincrease,butdecreasewithincreaseinthenumberofdoublebonds.Themeltingpointsincreaseintheorderoftriglycerides,diglyceridesandmonoglyceridesduetothepolarityofthemoleculesandhydrogenbonding.TheoilsamplesweresubjectedtoseveralpropertytestsinaccordancewithdifferentASTMstandards.ThefattyacidcompositionofJatrophamethylesterevaluatedwiththehelpofgaschromatographisshowninFig.2.TheresultssuggestthatunsaturatedfattyacidismorethansaturatedfattyacidinJatrophabiodiesel.ThegreatestdifferenceinusingJatrophaoilascomparedtodieselisthehigherviscositywhichcouldcontributetohighercarbondepositintheenginesandalsocausesomedurabilityproblems.However,thehighcetanenumberandcalorificvaluethatisapproximatelyequaltodieselfuelmakeitpossibletouseJatrophaoilindieselengines.Additionally,thehighflashpointofJatrophaoilmakesitsafertostore,useandhandlethanpetroleumdiesel;210°Cisthetemperatureatwhichitwillignitewhenexposedtoaflamewhiledieselisonly45—55°C.Theirheatingvalueliesintherangeof39-40MJ/kg,whichiscomparativelylowerthanthatofdieselfuels(about45MJ/kg).Thisisbecauseofthepresenceofchemicallybondedoxygeninvegetableoilslowerstheheatingvaluebyabout10%.Thecetanenumberisintherangeof32-40,whiletheiodinevaluerangesfrom0to200,dependingonunsaturation.Thecloudandpourpointofvegetableoilsishigherthanthatofdieselfuel[21].Thedifferentphysico-chemicalpropertiesofdieselandJatrophabiodieselaresummarizedinTable2.Table2.Physico-chemicalpropertiesofdieselandJatrophabiodieseloil.ASTM D Jatr JatrophaProperty methodieselophaoilbiodiesel(JMElOO)HighercalorificD-4439,539,594value(kJ/kg)8092,23284DensityD-40.0.920.881(kg/m3)0528311KinematicD-43.384.12

ASTMDJatrJatrophaPropertymethodieselophaoilbiodiesel(JME100)viscosity @452140°C(mm2/s)Acid no.D-60.2.320.09(mg.KOH/gm)642Cloudpoint,°C500D-212——1—4Pourpoint°C7D-917——6—8CFPP,°C371D-614———6Flashpoint,°C3D-967235162SulfurcontentD-23一8(ppm)62240APIgravity87D-28.773—29.11Cetaneindex6D977.144—48.13ExperimentalsetupAKirloskarmake,singlecylinder,aircooled,directinjection,DAF8modeldieselenginewasselectedforthepresentresearchwork,whichisprimarilyusedforagriculturalactivitiesandhouseholdelectricitygenerations.Itwasasinglecylinder,naturallyaspirated,vertical,air-cooledengine.ThedetailedtechnicalspecificationsoftheenginearegiveninTable3.TheschematicdiagramoftheexperimentalsetupalongwithallinstrumentationisshowninFig.3.TheenginetrialwasconductedasspecifiedbyIS:10,000.Themainparametersdesiredfromtheenginewerepowerproducedbytheengines,enginespeed(rpm),fuelconsumption,exhaustgastemperature,exhaustgasanalysis,crankanglemeasurementbycrankshaftencoder,in-cylindergaspressuremeasurementandheatreleaseratebyusingpressuretransducers.Thetransducerandthermocoupleswerefittedatthesuitablepositionstomeasurethereadingsatdifferentengineloadings.Thefuelinjectionsystemwasatraditionalsystemconsistingofasingleholepintlenozzlewhichinjectthefuelat200-205bar.Table3.Specificationofthedieselengine.Make KirloskarModelDAF10Ratedbrakepower(bhp/kW)10/7.4Ratedspeed(rpm)1500NumberofcylinderOneBorexStroke(mm)102x116Compressionratio17.5:1CoolingsystemAirCooled(RadialCooled)LubricationsystemSAE30/SAE40,ForcedfeedCubiccapacity0.78LitInjectionpressure(bar)200-205Afterfinalizingtheprocedurefordatacollectionandprocurementofthedesiredinstruments,theywereputonapanelboard.Oneburettewithstopcockandatwowayvalveswasmountedonthefrontsideofthepanelforfuelflowmeasurementsandselectingbetweenbothdieselfuelandbiodiesel.Thetwofueltanksof10Lcapacityweremountedforstoringthefuelsontherearsideofthepanelathighestposition.AVL437smokemeterandAVLDiGasAnalyzerwereusedforthemeasurementsofvariousexhaustgasparameters.Theaccuracyandreproducibilityoftheinstrumentwas±1%offullscalereading.ThedetectorwasaSeleniumphotocellwithdiameter45mm.Itsmaximumsensitivityinlightwaswithinthefrequencyrangeof550—570nm.Below430nmandabove680nm,thesensitivityoftheinstrumentwaslessthan4%relatedtothemaximumsensitivity.ThemeasurementprincipleforCO,HC,CO2wasinfraredmeasurementandforNOandO2itwaselectrochemicalmeasurement.Thedataacquisitionandcombustionanalysiswasdonethroughthesoftware‘engine-soft'providedbyApexTechnologiesandthiswasalsousedtodecomposetheextremedatafromthereadoutsofthemeasuringdevices.Atthesteadystatecondition,thedatacollectedwasrepeatedtotaketheaveragesoastominimizetheeffectoffluctuations.Forswitchingtheenginefromdieseltobiodiesel,atwowayvalvewasprovidedonthecontrolpanel.Boththefuelsfromthetwotankscouldbefeedtotheenginethroughthisvalveseparately.Thefuelfromthevalveenteredintotheenginethroughthefuelmeasuringunit.Thefuelfromfuelmeasuringunitthenenteredintothefuelfilterbeforeenteringtotheengine.Theenginewasloadedintherangeofnoload,20%,40%,60%,80%and100%load.Theperformance,combustionandemissioncharacteristicsofneatbiodieselanddifferentblendsofbiodieselanddiesel(5%,10%,20%,30%)wereevaluatedandcomparedwithdieselfuel.ResultanddiscussionsInthisstudy,analysisofcombustioncharacteristicofJatrophabiodieselanddieselwerecarriedout.ItisclearfromFig.4andFig.5thatignitionoffuelstartsearlierforbiodieselbasedfuelsincomparisontodieselfuel.Maximumcylindergaspressurewasfoundtobelowerforbiodieselbasedfuels.Indieselengine,cylinderpressuredependsontheburntfuelfractionduringthepremixedburningphasei.e.,initialstageofcombustion.Cylinderpressurecharacterizestheabilityofthefueltomixwellwithairandburn.Highpeakpressureandmaximumrateofpressurerisecorrespondtolargeamountoffuelburntinpremixedcombustionstage.ItmaybeduetohighercetaneindexofJatrophabiodieselresultinginshorterignitiondelayandmorefuelburntindiffusionstage.Theignitiondelayinadieselengineisdefinedasthetimebetweenthestartoffuelinjectionandtheonsetofcombustion.Rapidpremixedburningfollowedbydiffusioncombustionistypicalfornaturallyaspirateddieselengines.Aftertheignitiondelayperiod,thepremixedfuelairmixtureburnsrapidlyreleasingheatataveryrapidrate,afterwhichdiffusioncombustiontakesplace,wheretheburningrateiscontrolledbytheavailabilityofcombustiblefuel-airmixture.Theignitionqualityofafuelisusuallycharacterizedbyitscetanenumberorcetaneindex.Highercetaneindex/numbergenerallymeansshorterignitiondelay.Intheentiresetoftest,itwasfoundthatbiodieselhashighercetaneindexthanconventionaldieselfuel.Shorterignitiondelaycauseslowerpeakheatreleaseratetoloweraccumulationofthefuel.Thereforepremixedcombustionheatreleaseishigherfordiesel,whichisresponsibleforhigherpeakpressureandhigherrateofpressureriseincomparisontobiodiesel.Theignitiondelaydependsonfuelviscositywithresultinpooratomization,slowermixing,increasedmixingandreducedconeangle.Higherenginespeedleadstofastermixingbetweenfuelandairandshorterignitionoccur.Thevariationofbrakethermalefficiency(BTE)withrespecttomeaneffectivepressureisshownintheFig.6.FromthetestresultsofJatrophaderivedbiodieselandtheirblendsintheratioof5%,10%,20%,30%andmineraldiesel,itwasobservedthatinitiallywithincreasingbrakepower,thebrakethermalefficiencyofJatrophabiodieselanditsblendsalsoincreasestogetherwithdiesel.ThebrakethermalefficienciesoftheJatrophabiodieseloilanditsblendswerefoundtobelowerthandieselfuelthroughouttheentirerange.ThepossiblereasonsforthisreductionarelowercalorificvalueandincreaseinfuelconsumptionofJMEanditsblendsascomparedtodieselfuel.Thebrakespecificfuelconsumptions(BSFC)incaseofJatrophabiodieselanditsblendswerealsofoundtobehigherthandieselfuelasevidentfromtheFig.7.Thisismainlyduetothecombinedeffectsoftherelativefueldensity,viscosityandheatingvalueoftheblends.ThehigherdensityofJatrophabiodieselhasledtomoredischargeoffuelforthesamedisplacementoftheplungerinthefuelinjectionpump,therebyincreasingthespecificfuelconsumption.TheresultsobtainedduringthetestshowsthatthebrakespecificconsumptionofJatrophamethylesteranditsblends,whenusedinanunmodifieddieselenginewashigherthanthedieselfuel.ThevariationsofBSECwithrespecttochangeinbrakemeaneffectivepressure(BMEP)forJatrophamethylester,itsblendsanddieselfuelsisshownintheFig.8.ItisclearfromthefigurethatthebrakespecificenergyconsumptionofJatrophabiodieselanditsblendsishigherthandieselwhichisduetohighdensityandlowcalorificvalueofthefuel.Fig.9showsthevariationofexhausttemperaturewithbrakemeaneffectivepressureofdieselfuelandJatrophabiodieselanditsblends.Itshowsthattheexhaustgastemperatureincreasedwithincreaseinbrakepowerinallcases.Thehighestvalueofexhaustgastemperatureof505°CwasobservedwiththeJatrophabiodiesel,whereasthecorrespondingvaluewithdieselwasfoundtobe610°C.ThisisduetothepoorcombustioncharacteristicsoftheJatrophabiodieselanditsblendsbecauseofitsviscosityvariation.ThevariationinCO2emissionsisshownintheFig.10.Intherangeofwholeengineload,theCO2emissionsofdieselfuelarelowerthanthatofJatrophabiodieselanditsblendedfuels.Thisisbecausebiodieselcontainsoxygenelement,thecarboncontentisrelativelylowerinthesamevolumeoffuelconsumedatthesameengineloadandconsequentlytheCO2emissionsfromthevegetableoilanditsblendsarelower.TheresultshowsthattherewasaslightincreaseinCO2emissionswhenusingJatrophabiodieselanditsblends.Withinthewholeexperimentalrange,theCOemissionfromtheJatrophamethylesteranditsblendsislowerthanneatdieselfuelasshownintheFig.11.Withincreaseinbiodieselpercentageinbiodiesel-dieselblends,COdecreases,asbiodieselisoxygenatedfuelandcontainsoxygenwhichhelpsforcompletecombustion.HenceCOemissiondecreaseswithincreasingbiodieselpercentageinfuel.ThevaluesofunburnedhydrocarbonemissionfromthedieselengineincaseofJatrophamethylesteranditsblendsislessthandieselfuelasevidentfromtheHCemissionsareloweratpartialload,buttendtoincreaseathigherloadsforboththefuels.Thisisduetolackofoxygenresultingfromengineoperationathigherequivalenceratio.Thus,highpercentageofoxygenleadstolowHC.ThevariationofNOxemissionsfromJatrophamethylesteranditsblendswithrespecttodieselfuelareshowninTheNOxemissionsincreasedwiththeincreasingengineload,duetoahighercombustiontemperature.ThemostimportantfactorfortheemissionsofNOxisthecombustiontemperatureintheenginecylinderandthelocalstoichiometricofthemixture.Itcanbeseenthatwithintheentirerangeofloading,theNOxemissionsfromtheJatrophabiodieselanditsblendsarehigherthanthatofdieselfuel.TheincreaseintheNOxemissionsisfrom2110ppmto3129ppmatfullload.Theshorterignitiondelayandtheincreasedamountofbiodieselundergoingpremixedcombustionresultsinhighercylinderpressureandhencetemperature.TherateofformationofNOxemissionsindieselenginesisprimarilyafunctionofflametemperature,whichiscloselyrelatedtothepeakcylinderpressureandhencetemperaturethehigherdensityofbiodieselcomparedtodieselfuelinconjunctionwiththeincreasedinjectionpressure,resultsinthedeliveryofahigheramou