基于低温燃烧的全工况EGR率控制策略优化

Optimization of EGR Rate Control Strategy under Entire Working Conditions Based on Low Temperature Combustion

针对燃烧模式切换过程中EGR存在大跨度阶跃情况,拟采用小分阶EGR阶跃控制策略的过渡切换模式来探究切换过程的平顺性。为了获得不同工况下的最优EGR率,研究了低温燃烧下EGR率对燃烧和排放的影响,并在不同的转速和负荷条件下探究了EGR率的作用规律。结果表明:不同转速下的EGR率对燃烧和排放影响的差异比较小;负荷改变对EGR率的作用效果有明显的影响;根据负荷和指示平均有效压力将低温燃烧的工况分为3个区间,给出了不同区间的最佳EGR率,为燃烧模式切换过渡过程中利用分阶EGR方法来控制燃烧参数和稳定排放奠定了先期基础;同时,根据低温燃烧的不同负荷条件,提出了基于负荷的全工况下EGR的优化控制策略。

For the large step span of EGR during the switch of combustion mode,the transition mode of smallstep EGR step control strategy was proposed to explore the smoothness of switching process.In order to obtain the optimal EGR rate under different working conditions,the effects of EGR rate on combustion and emission under low temperature combustion were studied and the laws of EGR rate under different speeds and loads were analyzed.The results show that the effect of EGR rate has little influence on combustion and emission at different speeds.The effect of load change on EGR rate is obvious.According to the load and IMEP,the working condition of low temperature combustion is divided into three sections,and the optimal EGR rate of each section is proposed,which lays an early foundation for controlling combustion parameters and stabilizing emissions by using step-by-step EGR method in the switching process of combustion mode.At the same time,the optimal control strategy of EGR under entire working conditions is proposed according to different loads of low temperature combustion.