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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.

Hydrogen enriched compressed natural gas (HCNG) is thought to be a potential alternative to common hydrocarbon fuels for SI engine applications. Experimental researches focusing on how to use this kind of fuel to its full extent have been conducted for over ten years and are still on their way. From a review of these researches it is found that one of the biggest obstacles of efficiently and economically conducting such experiments is how to mix desired amount of hydrogen with natural gas. Most of the previous experiments use pre-bottled hydrogen/ NG mixtures (by mixing and storing desired amount of hydrogen and NG in high pressure steel cylinders before the tests) which are quite costly and unsafe, due to high pressure operation. More importantly, the blending ratio cannot be varied by that approach. By comparison, this paper presents an on-line hydrogen-natural gas mixing system through which the hydrogen/ NG blending ratio can be easily varied during the tests.