Comparison of Kinetic Mechanisms for Numerical Simulation of Methanol Combustion in DICI Heavy-Duty Engine

Abstract

The combustion process in a homogeneous charge compression ignition (HCCI) engine is mainly governed by ignition wave propagation. The in-cylinder pressure, heat release rate, and the emission characteristics are thus largely driven by the chemical kinetics of the fuel. As a result, CFD simulation of such combustion process is very sensitive to the employed reaction mechanism, which model the real chemical kinetics of the fuel. In order to perform engine simulation with a range of operating conditions and cylinder-piston geometry for the design and optimization purpose, it is essential to have a chemical kinetic mechanism that is both accurate and computational inexpensive. In this paper, we report on the evaluation of several chemical kinetic mechanisms for methanol combustion, including large mechanisms and skeletal/reduced mechanisms. These mechanisms are evaluated in terms of homogeneous ignition delay time, laminar flame speed, and multi-phase simulations of HCCI heavy-duty engine. The results are compared with experimental data and evaluated in terms of the accuracy and computational cost. It was found that scattering of ignition delay time predicted from different chemical kinetic mechanisms reported in the literature under homogeneous mixture ignition conditions give rise to a high sensitivity of the engine in-cylinder pressure prediction to the selected mechanism. (Less)