AKSU, C., Kawahara, N., Tsuboi, K., Nanba, S. et al., "Effect of Hydrogen Concentration on Engine Performance, Exhaust Emissions and Operation Range of PREMIER Combustion in a Dual Fuel Gas Engine Using Methane-Hydrogen Mixtures," SAE Technical Paper 2015-01-1792, 2015, doi:10.4271/2015-01-1792.
A single cylinder, supercharged dual fuel gas engine with micro-pilot fuel injection is operated using methane only and methane-hydrogen mixtures. Methane only experiments were performed at various equivalence ratios and equivalence ratio of 0.56 is decided as the optimum operating condition based on engine performance, exhaust emissions and operation stability. Methane-hydrogen experiments were performed at equivalence ratio of 0.56 and 2.6 kJ/cycle energy supply rate. Results show that indicated mean effective pressure is maintained regardless of hydrogen content of the gaseous fuel while thermal efficiency is improved and presence of hydrogen reduces cyclic variations. Increasing the fraction of hydrogen in the fuel mixture replaces hydrocarbon fuels and reduces carbon monoxide and hydrocarbon emissions. Mixtures with higher hydrogen content undergo faster heat release from flame propagation, approach knocking limit faster and are less knock resistant. 40% methane - 60% hydrogen mixture is prone to premature autoignition and superknocking, and is the critical concentration limit for methane-hydrogen mixtures.