Effects of CO Addition on the Lean Premixed CH₄/Air Flame

Abstract

AnumericalstudywascarriedouttodeterminetheeffectsofCOadditiononthelaminarburning velocity,NO x emission,andextinctionstrainrateinapremixedCH 4 /CO/airflameundertheleancondition(equivalence ratiooffueltoair 渍=0.60-0.80).WhenmoreCOwasaddedtothefuel,thelaminarburningvelocitydecreased,which isdifferentfromthatobservedforH 2 addition.Toexplainthis,westudiedthestrongcorrelationbetweenlaminar burningvelocityandH+OHpeakconcentrations.ResultsshowedthattheH+OHpeakconcentrationsdecreasedlinearly withanincreaseinCOcontent.Thistendencyisingoodagreementwiththatofthelaminarburningvelocity.ForNO x , weobservedthatincrementsinCOadditionledtoaremarkablereductionintheNO x emission.Inaddition,we investigatedtheNOformationmechanismanddeterminedtherelevantreactionsforNOproductionusingasensitive analysis.TheNOconcentrationsdecreasedsignificantlywithenrichmentbyCOandtheNOproductionratealso clearlydecreased.Wecalculatedtheradialstrainrate S rad anddiscussedtheinfluenceofstrainrateonleanflame stabilitywithregardstotheadditionofdifferentCOmolefractionstothefuel.Theextinctionstrainratesindicatedthat theleanflammabilitylimitswereextendedbyCOadditioninsomeway.