基于缸内压力振荡的冷EGR对汽油机爆震特性的影响

基于内燃机缸内压力波动方程研究了冷废气再循环(EGR)对汽油机爆震特性的影响.由KIVA-3V燃烧程序的三维流场推导出内燃机缸内压力波动方程,并分别从均值压力和波动压力角度来讨论冷EGR对汽油机爆震的影响规律.分析了不同冷EGR率下燃烧室温度、均值压力和波动压力等燃烧特性.结果表明:随着冷EGR率的增加,缸内燃烧温度、压力升高率大大降低,燃烧持续期明显增加;同时,缸内压力波动幅值明显降低而均值压力变化不大,可见引入适当的冷EGR率对汽油机高频压力振荡有很好的抑制作用.最后,对缸内压力波动进行频谱特性分析,探讨了燃烧室空腔共鸣和发动机爆震之间的关系.

Impact of Cooled EGR on SI Engine Knocking Characteristics Based on In-Cylinder Pressure Oscillations

Impact of cooled exhaust gas recirculation （EGR） on spark-ignited （SI） engine knocking characteristicswas researched based on pressure wave equation of internal combustion engines. A pressure wave equation was de-rived from the three-dimensional flow field of KIVA-3V program, and the impact pattern of cooled EGR on SI engineknock was discussed in terms of mean pressure and oscillating pressure. Calculated results of in-cylinder temperature,mean pressure and oscillating pressure under different cooled EGR ratios were analyzed, and it is found that with theincrease of cooled EGR ratio, combustion temperature and rate of pressure rise decrease rapidly, and combustionduration increases obviously. Meanwhile, the amplitude of in-cylinder pressure oscillation decreases significantlywithout obvious variation in mean pressure, which indicates that the application of appropriate cooled EGR ratio hasa good inhibition effect on high-frequency pressure oscillations. Finally, spectrum analysis of in-cylinder pressureoscillations was carried out in order to investigate the relations between cavity resonance of combustion chamber andengine knock.