A quasi-dimensional combustion model for SI engines fuelled by hydrogen enriched compressed natural Gas

HCNG is short for hydrogen enriched natural gas. Compared to traditional gasoline, diesel or even natural gas engines HCNG fuelled engines have several advantages on environment protection and energy security and in order to make full extent of the new fuel, several modifications have to be made in the corresponding engine and the control strategy. So there is a need to develop a predictive model to simulate the engine's performance without really running the engine, which could speed up the development of HCNG engines. This paper dose such a job. At first the paper presents the fundamentals of the quasi-dimensional model. The equations of the two-zone thermodynamic model and turbulent entrainment combustion model are both introduced. The methods of calculating the related parameters such as theoretical adiabatic flame temperature, laminar burning velocity of HCNG mixture under various hydrogen blending ratios are also given. And after briefly introducing the approaches used to deal with the properties of the working fluid and the combustion geometry some predicted results are compared with that experimentally obtained in order to testify the applicability of the model. The second part of the paper at first describes the experimental testing rig. Then the quasi-dimensional combustion model is used to simulate engine operation under twelve operating conditions and the results of the prediction, such as in-cylinder pressure, mass fraction burned and etc are compared with those obtained by running the engine. It turns out that the prediction results are in good agreement with the experimental ones for all hydrogen blending ratios used, which confirms the applicability of the proposed model. © 2008 SAE International.