Evaluation of empirical heat transfer models for HCCI combustion in a CFR engine

The heat transfer from the bulk gases to the combustion chamber walls has a strong effect on the combustion and emission formation process in an HCCI engine. In this work, the empirical heat transfer models of Annand, Woschni, Hohenberg, Bargende, Chang et al. and Hensel et al. are evaluated at various engine operating conditions. The modelled heat flux is compared to the measured heat flux in a CFR engine with a thermopile sensor. The shape of the heat flux trace, the maximum heat flux and the total heat loss are evaluated and different model calibration procedures are investigated. It is found that all models require calibration and need to be recalibrated if the fuel type and certain engine settings are changed. A better model fit can be obtained if different model coefficients are applied for the compression and the expansion phase.