ABSTRACT
Using ammonia/diesel premixed-charge compression ignition (PCCI) mode is an effective method to achieve efficient and clean utilization of ammonia in engines. The optimization of the spatial and temporal distribution of in-cylinder high-reactivity fuel at low loads is the key to improving ammonia/diesel PCCI combustion. In this study, based on a heavy-duty single-cylinder engine, the effects of diesel double-injection strategy on the combustion process and emissions with the use of ammonia/diesel PCCI combustion under the low loads was investigated. Combining three-dimensional simulations, the mechanisms of how diesel second injection ratio (DSIR) and diesel first injection timing (DFIT) regulation affect the concentration and reactivity distribution of the mixture was revealed. Compared to diesel single-injection, using DSIR can significantly improve the spatial distribution of high-reactivity fuel and reactive free radicals, which accelerated the in-cylinder combustion. The experiment results showed that through the coordinated optimization of DSIR ratios and DFIT, a gross indicated thermal efficiency of 49.3% could be achieved, and the GHG emissions could be further reduced by 10% based on the optimal point of diesel single-injection.
