Experimental investigation on methane inert gas dilution effect on marine gas diesel engine performance and emissions

The behavior of a dual-fuel compression engine on a marine scale was investigated using a Rapid Expansion-Compression Machine (RCEM) fueled by gas oil emulsion and methane-inert gases dilution. The methane-inert gas blend was utilized as the primary injected fuel, with a pilot dose of diesel fuel acting as an ignitor. The findings demonstrate enhancements in the case of gas dilution besides the gas oil emulsion. Integrating inert gases with methane fuel improves flame penetration and increases the combustion duration. Blending inert gases with methane boosts the heat release rate of the combustion, leading to an increase in in-cylinder pressure peak by 3% for all tested fuels. In the case of gas oil (GO) emulsion, 95% reduction in NOx emissions compared to GO was reached. Using a methane-nitrogen mixture with 17.5% nitrogen gas reduces NOx emissions to 62% of the gas oil fuel emissions. Generally, diluting the methane with inert gas has the same effect as water-Gas Oil emulsion on combustion enhancement and emission reduction. This experimental study suggests using the Methane–Nitrogen combination as a direct-injected fuel with 17.5 percentage nitrogen gas.