The impact of ignition and activation energy distribution on the combustion and emission characteristics of diesel-ammonia-natural gas engines

Abstract

To enhance the performance and reduce emissions of ammonia-diesel engines, natural gas is employed as a partial substitute for diesel fuel. This substitution accelerates the combustion rate of ammonia fuel, resulting in improved engine efficiency and decreased emissions. This study investigates how variations in ignition energy (diesel quantity) and activation energy (natural gas quantity) distribution ratios affect engine combustion and emission characteristics through simulation. The study established six groups of operating conditions, with ignition energy ranging from 24 mg to 4 mg. The findings indicate that substituting part of the ignition energy with activation energy enhances the combustion efficiency of ammonia, increases the engine's indicated thermal efficiency and reduces ammonia slip. The optimal operating condition identified in this study is D16/N8, yielding a thermal efficiency of 51.0 %. Compared to the case without natural gas addition, NOx emissions increased, while other pollutants showed significant reductions. In particular, N₂O emissions decreased by 97 %, greenhouse gas (GHG) emissions dropped by 57.2 %, ammonia slip was nearly eliminated, and unburned losses were minimal. The findings of this research offer valuable insights for further enhancing efficiency and reducing emissions in ammonia-diesel dual-fuel engines.