A Numerical Study of the Effect of Multi-Injection Strategy on NOx Reduction in DI Diesel Engines

Diesel engines are becoming more and more popular as a power source for transportation and industry utility because of their better fuel efficiency over gasoline engines. At the same time, more and more stringent emission regulations on internal combustion engines have been used by governments all over the world. NOx emission control has become one of the biggest challenges in the design of Diesel engines. Previous experiments and simulations have shown that the multi-fuel-injection strategy can potentially reduce NOx emission in Diesel engines. In this study, more detailed numerical simulations have been conducted for up to 5 split fuel injections as compared to the conventional single fuel injection strategy to explore the effect of multi-fuel-injection on NOx reduction. KIVA-3V release 2, a multi-dimensional computational code employing combustion model, turbulence model, spray model and NOx production model, has been used in the numerical simulation. The combinations of multi-fuel-injection strategy with EGR (Exhaust Gas Recirculation) technique and multi-hole injectors are investigated as well. The results of this investigation have demonstrated that the use of the multi-fuel-injection strategy can effectively reduce the NOx emission in Diesel engines. Combined with other NOx reduction techniques, multi-fuel-injection strategy is a very promising way to make modern Diesel engines comply with the ever-stringent emission targets.