Experimental study on the effects of methane-hydrogen jet as direct injected fuel in marine diesel engine

Hydrogen as a carbon-free fuel can significantly reduce greenhouse gases if used in the diesel engine. Introducing hydrogen with methane as a premixed fuel leads to abnormal combustion and knocking. Hence, the current study investigates a direct injection of methane-hydrogen to be combusted as a diffusive combustion. This research studied the effect of different injection pressures on the characteristics of the methane-hydrogen jet. Also, studied the combustion of methane/hydrogen jets as the primary fuel in a diesel engine (fuel-compositions: 80/20, 70/30, and 50/50 v/v% of methane/hydrogen). The combustion of the methane-hydrogen blends was observed by capturing direct images and shadowgraphs for the in-cylinder combustion using high-speed cameras, besides measuring the in-cylinder pressure and the exhaust gas emissions. The results revealed that the penetration length of the methane-hydrogen blend jet was slightly shorter than the methane by 5%. The methane-hydrogen penetration length increased by 8% when the pressure ratio was increased by 50%. The hydrogen usage increased the in-cylinder pressure and the indicated mean effective pressure by 7.5% and 11%, respectively. Moreover, hydrogen usage decreased CO₂ and hydrocarbon emissions by 23% and 60%, respectively. Conversely, the fuel blend containing 50% hydrogen increased the nitrogen dioxide emissions by 50% compared to methane.