Modelling Methodology of a Spark-Ignition Engine and Experimental Validation: Part I: Single-Zone Combustion Model

This paper describes a general procedure for defining a fuel heat release function to be used in a single-zone combustion model of a spark-ignition engine using crank-angle resolved analysis of the pressure. The combustion model parameters to identify are the combustion angles and the Vibe function coefficients. Furthermore, the cylinder wall temperature is identified using the cylinder pressure during the closed-valve period of the compression stroke, and the heat transfer correlation (Woschni's correlation) is tuned according to the difference between the fuel heat release and the net heat release. The fuel heat release is determined with the polytropic index first law model. This heat addition due to combustion is verified by reference to the fuel consumption and combustion efficiency. Combustion efficiency is determined from the exhaust gas composition.

In this way, the combustion parameters are identified and the heat transfer correlation is verified for an engine at different loads and engine speeds. The experimental data used are the crank-angle resolved cylinder pressure and the measurements in a typical engine dynamometer test: engine speed, load, fuel consumption, AFR and air charge conditions.

Finally a full comparison of experimental cylinder pressures and single-zone model results is made with the conclusion being reached that the combustion parameters were correctly identified.