Experimental study for optimizing EGR strategy in an ammonia-diesel dual-fuel engine under different altitudes

Ammonia has emerged as a promising alternative fuel for internal combustion engines, showing significant potential for development. In order to investigate the ability of Exhaust Gas Recirculation (EGR) to improve the emission performance of Ammonia-Diesel Dual-Fuel (ADDF) engines. This study selected a four-cylinder diesel engine with a displacement of 3.0 L and use the EGR strategy to optimize the emissions of an ADDF engine at various altitudes. The research was conducted under different altitudes (0 m, 1000 m, and 2000 m) with a test condition of 1400 r/min at 50 % load. The results indicate that as the EGR rate increased, the in-cylinder pressure and heat release rate of the ADDF engine decreased, the in-cylinder temperature rose, and both combustion center and the combustion duration were prolonged. There was a noticeable reduced in NOx and NH3 emissions, and the reduced becomes more pronounced with altitude increased. However, an increased in EGR leads to higher CO2 concentrations, but the total CO2 mass emissions remain constant. Finally, the response surface methodology was utilized for optimization experiments, and the results show that with the increased in altitude, the ammonia substitution rate can be increased while the EGR rate should be decreased.