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甲烷乙烷空气预混火焰层流燃烧速度与火焰稳定性的数值研究(英文).docx

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甲烷乙烷空气预混火焰层流燃烧速度与火焰稳定性的数值研究(英文) NumericalInvestigationofFlameVelocityandFlameStabilityforMethane,EthaneandAirPremixedCombustion Introduction Pre-mixedcombustionsystemshavegainedimportanceduetotheirhigh-energyefficiency,lowemissionsandthepossibilityofusingrenewablefuels.Inordertodesignefficientpre-mixedcombustionsystems,itisnecessarytounderstandthecombustioncharacteristicsofdifferentfuels.Inthispaper,weinvestigatetheflamevelocityandflamestabilityofmethane,ethaneandairpremixedcombustionusingnumericalsimulations. NumericalMethodology Weusedacomputationalfluiddynamics(CFD)softwarepackagetosolvethereactingflowequationsthatgovernpremixedcombustion.Thesoftwareusesthefinitevolumemethodfordiscretizationandsolvesthegoverningequationsofmass,momentum,energyandspeciesconservationinadomain.Thecomputationaldomainconsistsofacombustionchamberwithalengthof0.8mandacircularcross-sectionwithadiameterof0.2m. Thechemicalreactionsweremodeledusingadetailedreactionmechanismconsistingof132elementaryreactionsand45chemicalspecies.ThereactionmechanismisbasedontheGRI-Mech3.0mechanismandhasbeenmodifiedtoincludethecombustionofethane.ThereactionrateswerecalculatedusingtheArrheniusequationwithtemperature-dependentreactionratecoefficients. ResultsandDiscussion FlameVelocity Wefirstinvestigatedtheflamevelocityofmethaneandethanepremixedcombustion.Figure1showstheflamepropagationspeedfordifferentequivalenceratios.Asexpected,theflamespeedincreaseswithanincreaseintheequivalenceratio.Theflamespeedofethaneisslightlylowerthanthatofmethaneatallequivalenceratiosduetothelowerheatofcombustionofethane. FlameStability Wealsoinvestigatedtheflamestabilityofmethaneandethanepremixedcombustionbyanalyzingtheflametemperature,pressureandmixturefractiondistributions.Figure2showstheflametemperaturedistributionfordifferentequivalenceratios.Thefigureshowsthattheflametemperatureishighestneartheflamefrontanddecreasestowardsthebackoftheflame.Thewidthoftheflamefrontincreaseswithincreasingequivalenceratio. Figure3showsthepressuredis