Numerical Analysis of the Autoignition of Methanol, Ethanol, N-Heptane and N-Octane Sprays with Detailed Chemistry

Abstract

Abstract The autoignition process of fuel sprays has relevance to compression-ignition engines. The present study focusses on a detailed description of the processes involved. In particular, variable liquid and gas properties, detailed transport in the gas phase, and detailed reaction mechanisms are considered. The model uses a simplified geometry and assumes a uniform spray. Results of numerical calculations of the autoignition of methanol, ethanol, n-heptane, and n-octane are presented, where special attention is focussed on differences in liquid properties. It appears that the vaporization rate is dominated by the ratio MF/φ, the molecular weight of the fuel over the molar ratio of oxygen to fuel, and by the latent heat of vaporization, Lv. For the fuel methanol. both MF/φand Lv are largest, so that in spite of the high volatility of methanol. both spray lifetime and ignition delay are largest for a methanol spray compared to ethanol, n-heplane and n-octane. Ignition delay increases with initial drople...