Simulation of combustion in spark-ignition engine fuelled with natural gas-hydrogen blends combined with EGR

A numerical simulation of the influence of different hydrogen fractions, excess air ratios and EGR mass fractions in a spark-ignition engine was conducted. Good agreement between the calculated and measured incylinder pressure traces as well as pollutant formation trends was obtained. The simulation results show that NO concentration has an exponential relationship with temperature and increases sharply as hydrogen is added. EGR introduction strongly influences the gas temperature and NO concentration in the cylinder. The difference in temperature will lead to even greater difference in NO concentration. Thus, EGR can effectively decrease NO concentration. NO concentration reaches its peak value at the excess air ratio of 1.1 regardless of EGR mass fraction. The study shows that natural gas-hydrogen blend combined with EGR can realize a stable combustion and low NO emission in a spark-ignition engine.