Study on Validation of Turbulent Entrainment Combustion Model for Spark-Ignition Engines

A turbulent entrainment combustion model is considered to be reasonable for the combustion in spark-ignition engines. It is important to study the validation of this model for different combustion chamber shapes of the engines under various operating conditions. Nevertheless, the verification of this model has not been performed sufficiently. Based on some investigators' work of the turbulent eddy structure and turbulent characteristics in the cylinder of spark- ignition engine, a turbulent entrainment combustion model for spark- ignition engines is developed, and numerical simulation of combustion process is carried out in this study. The model is examined under various operating conditions of engine speed, loads, air- fuel ratio and spark timing for three shapes of combustion chambers: HRCC in head (compression ratio is 10), May process (compression ratio is 10 and 12 respectively) and Bowl- in- piston (compression ratio is 10). The four empirical coefficients for each combustion chamber in the model are determined, and the comparison between the predictions and measurements is done. It verifies that the four empirical coefficients are fixed for the same shape of combustion chambers (regardless of different compression ratio) under various operating conditions, and that the four coefficients vary with the shapes of combustion chambers. The calculation results of mass fraction burned, the pressure diagrams, mean indicated pressure, the maximum pressure etc. are in good agreement with the experimental data, thus the model is considered to be valid for predicting the combustion of spark-ignition engines.