Laminar combustion characteristics of methane/methanol/air mixtures: Experimental and kinetic investigations

Abstract

Methanol has been studied to solve the problems of insufficient combustion and unstable operation of natural gas engines. To explore the influence of methanol addition on natural gas/air mixture, the laminar combustion characteristics of stoichiometric methane/methanol/air mixture with methanol volume fractions of 0–100% are measured in a constant volume combustion chamber under the initial pressures of 1–4 bar and initial temperatures of 353–393 K. The experimental results show that the laminar combustion characteristics are linearly enhanced by methanol addition. When the methanol volume fraction varies from 0% to 100% at 393 K and 4 bar, the change rates are 11.7%, 120.4%, - 28.1% and 61.7% for combustion peak pressure, maximum pressure rise rate, combustion duration and laminar burning velocity (LBV) respectively. At high pressure, the influence of methanol addition is enhanced. Chemical kinetics analysis shows that CH2OH, the intermediate product of methanol oxidation, generates HO2 through R134: CH2OH + O2<=>CH2O + HO2, which contributes from 14% to 56% to the generation of HO2, so that HO2 replaces part of the O2 to participate the reaction with H, resulting in the transformation of part of R1: H + O2<=>OH + O to R10: HO2+H<=>2OH, thereby generating more OH and promoting the reaction.