The effect of higher alkanes on the ignition of methane-oxygen-argon mixtures in shock waves

Ignition delay times and product distribution were observed in mixtures of methane-oxygen-argon to which different amounts of ethane, propane, butane and pentane were added. All produced appreciable reduction in ignition delay time, which at low additive concentrations could be correlated in terms of the thermal effects. However, chemical analysis of quenched reacting mixtures and kinetic model calculations indicated that the additive influence was chemical and not thermal. An explanation is advanced for the thermal correlation and its breakdown.