喷射正时及掺氨比对氨/柴油低速机性能影响研究

For large-bore low speed two-stroke ammonia/diesel dual fuel marine engines,a three-dimensional numerical simulation model was established in CONVERGE,and the diesel,liquid ammonia spray and the engine model were verified based on the experimental data.The high-pressure direct injection mode was used to analyze the in-cylinder combustion of the engine under different liquid ammonia injection timing and ammonia energy fraction,and to summarize the effects of its performance and emission.The results show that the engine adopts high-pressure direct injection mode,the in-cylinder combustion is basically divided into three stages,with the advance of liquid ammonia injection timing,the combustion duration is shortened,the power output,the indicated average effective pressure and the indicated thermal efficiency are increased,the NOX emission increases and exceeds the Tier III standard;with the increase of ammonia energy fraction,the combustion duration is extended,the power output,the indicated average effective pressure and the thermal indicated efficiency are reduced,and NOX emissions are reduced,which gradually meet the Tier III standard.Therefore,coupled injection timing and ammonia energy fraction are required to ensure both engine performance and NOX emissions.