Investigations on semi-empirical heat transfer models for heat flux of HCCI engine fueled with natural gas

Homogeneous charge compression ignition (HCCI) has attracted lots of attention due to the high thermal efficiency, lower NO x, and Soot exhaust emissions. Heat transfer from the gases to the combustion chamber walls has effective impact on the combustion process and the formation of engine-out emissions in HCCI engine. In this study for the first time a zero-dimensional single-zone model coupled with detailed chemical kinetics was used to evaluate the semi-empirical heat transfer models of Annand, Woschni, Hohenberg along with Assanis and Hensel to calculate heat flux in an HCCI engine fueled with natural gas. For this purpose, the 3D-CFD model coupled with detailed chemical kinetics was firstly validated by using experimental data, and then the 3D derived model was used as a base model for evaluating zero-dimensional model. Furthermore, the response surface model (RSM) was employed for investigating the effect of input parameters of engine including intake pressure (1, 1.25, and 1.5bar), equivalence ratio (0.3, 0.5, and 0.7), and engine speed (800, 1100, and 1400rpm) on the output parameters i.e., in-cylinder pressure and heat flux. In most cases were assessed, the zero-dimensional simulation results indicated that Annand technique provided the best model for heat flux simulation. Besides, the model of Hohenberg overpredict the heat flux in comparison with the calculated values derived from the 3D model, while Assanis and Hensel models underpredict the heat flux compared with the evaluated value of the 3D model. Furthermore, Woschni’s model cannot be used to model the heat flux in HCCI engine.