二次喷射比率及天然气替代率对柴油转子发动机燃烧过程的影响

Effect of Natural Gas Replacement Rate and Secondary Injection Ratio on Combustion Process of Diesel Rotary Engine

针对直喷式柴油转子发动机缸内工作过程,基于Fluent软件以及耦合正庚烷简化机理建立了柴油转子发动机的动态仿真模型,并利用实验数据验证了模型的可靠性.在此基础上,对比分析了二次喷油比例及天然气替代率对燃烧过程的影响.研究结果表明:纯柴油工况下,预主喷射比例设置为6/4时缸内压力最高,同时获得了较少的CO和碳烟生成量.保持当量比为0.9,天然气替代率的增加使得缸内混合气的初期燃烧速度减缓而后期燃烧速度逐渐提高;采用6/4的预主喷射比例、掺混50%,天然气可以在保持动力性的同时,大大降低CO、碳烟的生成量,并较好地控制NO生成量.

Based on the Fluent software,a dynamic simulation model of a direct injection diesel rotary engine coupled with a reduced reaction mechanism of n-heptane was established.The reliability of the model was verified by the experimental data.On the basis of it,the influence of secondary injection ratio and natural gas replacement rate on combustion process was compared and analyzed.The results show that under the pure diesel condition,the cylinder pressure was highest when the pre-main injection ratio was 6/4,and at the same time,less CO and soot generation were obtained.By maintaining the equivalent ratio of 0.9,the increase of natural gas replacement rate initially slowed down and then gradually increased the burning speed of the in-cylinder mixture.With the 6/4 premain injection ratio and 50%, natural gas replacement rate,better dynamic performance was maintained,and at the same time,the amounts of CO and soot production were greatly reduced and NO production was better restricted.