Abstract
Direct numerical simulations of autoignition have been conducted to clarify turbulent combustion mechanisms in homogeneous charge compression ignition engines. Methane-air mixtures at high pressure, 51.3 atm, with spatial inhomogeneity of temperature are investigated by considering a detailed kinetic mechanism. For the case with smaller temperature fluctuations, autoignition occurs in almost whole domain. On the other hand, for the case with larger temperature fluctuations, autoignition occurs at high temperature region and flame propagates from the ignition kernel. The early autoignition and the flame propagation with increasing pressure inhibit the drastic rise of the heat release rate and shorten the ignition delay time due to the increased pressure.
