Development of a three-dimensional knock simulation method incorporating a high-accuracy flame propagation model

Abstract

Combustion in internal combustion (IC) engines involves very complicated phenomena (including flame propagation and knock), which are strongly affected by engine speed, load, and turbulence intensity in the combustion chamber. The aim of this study was to develop a flame propagation model and a knock prediction technique applicable to various engine operating conditions, including engine speed and in-cylinder turbulence intensity. A new flame propagation model, the universal coherent flamelet model (UCFM) has been developed that improves the coherent flamelet model (CFM) by considering flame growth both in terms of the turbulent flame kernel and laminar flame kernel. A knock prediction model was developed by implementing the Livengood-Wu integral as the autoignition model in the flame propagation model. The combined model allows evaluation of both where and when autoignition occurs in a real shape combustion chamber. A comparison of the measured and calculated time for the occurrence of knock shows good agreement for various operating conditions. The three-dimensional calculation results indicate the general tendency for the location where autoignition occurs in the combustion chamber and the effect of the spark plug position on the occurrence of knock.