Prediction of ignition timing and combustion process in gasoline HCCI engines by means of zero-dimensional chemical kinetics calculation in consideration of combustion characteristic time

Abstract

In this study, investigation was conducted on prediction of ignition timing and combustion process in a gasoline homogeneous charge compression ignition (HCCI) engine by means of one-dimensional engine cycle simulation and zero-dimensional chemical kinetics calculation. In-cylinder gas thermal states, air-fuel ratio and EGR ratio at intake valve closing time were obtained by means of cycle simulation and applied to initial conditions for chemical kinetics calculation. A detailed kinetic model (101 species and 592 reactions) obtained from the elementary reaction schemes for iso-octane and n-heptane was modified for zero-dimensional calculation with regular gasoline of octane number 91, and validated by engine experiments. The combustion characteristic timescale model by Kong et al. was applied to zero-dimensional chemical kinetics calculation for considering the influence both of the chemical reaction and turbulent mixing. As a result, ignition timing and combustion processes were predicted reasonably at various supercharging pressure and engine speeds. Copyright © 2008 by the Japan Society of Mechanical Engineers.