Heat release and combustion characteristic parameters of a direct injection engine fueled with natural gas/hydrogen blends

A study on heat release and combustion characteristic parameters of a direct injection spark ignited engine fueled with natural gas/hydrogen blends was carried out. The results showed that the brake effective thermal efficiency increased with the increase of hydrogen fraction at low and medium loads. High thermal efficiency was achieved at high loads and didn't vary with the variation of hydrogen fraction. With the increase of hydrogen fraction the phase of the heat release curve advanced, rapid combustion duration decreased and heat release rate increased. This phenomenon was more obvious at the low speed operating mode, revealing relatively high enhancement of burning velocity of mixtures by hydrogen addition in the case of weak air motion in cylinder. The maximum mean gas temperature, pressure rise rate and heat release rate increased with the increase of hydrogen fraction.