Laminar burning velocities and weak flammability limits under engine-like conditions

Abstract

Laminar burning velocities and weak flammability limits have been measured at high temperatures and pressures achieved simultaneously by the use of an adiabatic compression machine. For methane the measured burning velocity compares well with extrapolations from less severe conditions. For the other hydrocarbon fuels such a comparison was not possible but the relative values of the burning velocities mirror those for flames burning in air at atmospheric pressure and room temperature. For methane, 2-methylpentane, methylcyclopentane, hex-1-enc, and toluene the weak flammability limits were all found to be close to the half-stoicheiometric mixture, as at atmospheric pressure and ambient temperature. In contrast, for hydrogen and ethylene the weak limits are at stoicheiometries of 0.13 and 0.35. For three gasolines of widely different composition, the weak limits were all found to be near to an air-to-fuel ratio (W/W) of 30, which is substantially leaner than the practical operating limit in gasoline engines of current design.