Study of spark ignition engine emissions fueled by blended hydrogen and methane

Nowadays, considering vast natural gas reserves in the world and also the general approach to reduce environmental contaminants, the use of the natural gas as the clean fuel has been increased in many countries. Various schemes have been offered to use the natural gas in internal combustion engines. Blending the natural gas with other fuels in order to profit their different advantages is one of plans. Due to their unique characteristics, one of blends is hydrogen and methane. In this paper, a semi-dimensional, two-zone model has been used to study the performance of the hydrogen-methane fueled spark ignition engine. The in-cylinder mixture chemical composition included 11 chemical species, which were determined by the chemical equilibrium assumption. The extended Zeldovich mechanism was used to model the nitrogen oxides concentration. In addition, in order to predict the carbon monoxide concentration, a two-stage chemical kinetic mechanism was utilized. The model validation was done by comparing the results with literature experimental studies. A good agreement between results showed that the model had a good accuracy in predicting the performance of the engine. Engine emissions were compared and thoroughly discussed in different hydrogen-methane compositions and also equivalence ratios.