Optimizations of energy fraction and injection strategy in the ammonia-diesel dual-fuel engine

Abstract

Fuel consumption and emissions are growing concerns, driving the need for cleaner alternative fuels in engine research. Ammonia is a competitive alternative fuel. To enhance the effective utilization and provide a new direction for the marine application of ammonia, an ammonia-diesel dual-fuel engine model with the pre-combustion chamber structure was designed. Numerical simulations were carried out in this paper, considering variations in diesel energy fraction, ammonia injection timing, diesel injection pressure, and diesel injection timing. The findings indicate that an appropriate amount of pilot diesel accelerates jet flame formation, improving combustion efficiency. Advancing ammonia injection timing improves mixture homogeneity but increases ammonia slip, while delaying ammonia injection timing leads to mixture stratification. Locally rich areas in the mixture improve combustion efficiency. The timing and pressure of diesel injection significantly impact both combustion efficiency and emissions. Advancing diesel injection timing improves power output but increases NOX emissions. Increasing diesel injection pressure improves combustion efficiency, but excessive pressure leads to deterioration. Overall, this study provides valuable insights into the potential use of ammonia as a sustainable fuel for marine low-speed engines, selecting the optimal energy fraction and injection strategy to achieve efficient and environmentally friendly combustion.