An Experimental and Analytical Investigation of the High-Temperature Oxidation Mechanisms of Hydrocarbon Fuels

Abstract

An experimental and analytical investigation of the oxidation of methane and ethane behind shock waves has been carried out. Mixtures of methane/oxygen and ethane/oxygen dilute in argon were shock-heated by both incident and reflected waves. The progress of the reaction was followed by monitoring infrared emission from CO₂, CO and H₂O and the density gradient. The experimental data were expressed in terms of reaction times which were correlated with initial fuel and oxygen concentrations and temperature. To determine oxidation mechanisms for methane and ethane, measured reaction times were compared with calculated reaction times obtained from an analytical study of the two reactions. In the analytical study the time rates of change of species concentration and thermodynamic properties during reaction were calculated by numerically integrating the coupled reaction kinetic, state and gas dynamic equations. A 14-step mechanism for the high-temperature oxidation of methane was suggested which gave good agreement between calculated and measured reaction times. A simplified 11-step mechanism for the high-temperature oxidation of ethane was proposed. In the proposed mechanism ethane reacts only via the decomposition reaction, forming two methyl radicals. The methyl radicals react via the reactions of the methane mechanism. Using the simplified mechanism, reasonable agreement between calculated and measured reaction times was obtained.