瞬态EGR对柴油机低温燃烧切换平顺性影响

针对传统燃烧(CDC)与低温燃烧(LTC)双模式柴油机在燃烧模式切换过程中出现的平均指示压力(IMEP)波动、发动机工作平顺性差的问题,基于自主设计开发的单缸柴油机,进行了燃烧模式切换过程瞬态废气再循环(EGR)影响研究.研究表明:燃烧模式切换过程中EGR率变化与燃油喷射变化不同步是造成IMEP波动的主要原因,在1100 r/min、等IMEP为0.6 MPa的LTC负荷上限CDC-LTC的直接切换过程中,EGR响应滞后约22个循环,造成IMEP波动率达到12.82%;采用EGR预控制可以实现EGR与喷油控制的优化匹配,IMEP波动率下降至3.17%,有效改善了切换过程中发动机平顺性.

Effect of Transient EGR on Smoothness of Low Temperature Combustion Mode Switching of Diesel Engine

The combustion mode switching between the conventional diesel combustion(CDC)and the low temperature combustion(LTC)was studied in a self-designed single-cylinder diesel engine.The study focuses on transient exhaust gas recirculation(EGR)control in order to minimize the instabilities in the indicated mean effective pressure(IMEP).Results show that the deviation of the response speed between EGR and fuel injection is the main cause of IMEP fluctuations.At 1100 r/min,the direct switching of CDC-LTC is performed when the upper load IMEP of the LTC reaches 0.6MPa.During the switching process,the EGR response is delayed by 22 cycles,causing an IMEP fluctuation rate of 12.82%.Optimal matching of EGR and fuel injection control can be achieved through EGR pre-control,which can reduce the IMEP fluctuation rate to 3.17%and effectively improve the engine smoothness during the switching process.