不同转速下循环波动对SI发动机爆震燃烧影响的大涡模拟研究  

Large eddy simulation study on the effect of cycle-to-cycle variation of SI engine knocking combustion at different rotational speeds

作　　者：潘明章 李振义 莫海俊[1] 叶年业 官维[1] 满兴家 PAN Mingzhang;LI Zhenyi;MO Haijun;YE Nianye;GUAN Wei;MAN Xingjia(School of Mechanical Engineering,Guangxi University,Nanning 530004,China;SAIC-GM-Wuling Automobile,Liuzhou 545007,China)

机构地区：[1]广西大学机械工程学院,南宁530004 [2]上汽通用五菱汽车股份有限公司,广西柳州545007

出　　处：《重庆理工大学学报(自然科学)》2025年第3期177-185,共9页Journal of Chongqing University of Technology:Natural Science

基　　金：中央高校基本科研业务费资助项目(自然科学类)(300102383503);广西重点研发计划项目(桂科AB22080084)。

摘　　要：小型强化汽油机具有强劲的动力性和优秀的燃油经济性,但存在爆震问题,基于大涡数值模拟耦合G方程模型,以点燃式发动机爆震燃烧为研究对象,分析了不同转速下SI发动机循环波动特性与末端气体自燃及爆震的关系,结果表明:在火花点火时刻固定的情况下,转速的提高会降低主火焰在曲轴转角时间内的传播速度,转速为4000 r/min循环的50%燃油质量分数点平均比3000 r/min循环延迟4°,从而使爆震起始时刻推迟;同时发现燃烧初期不同的火焰发展速度是造成循环间爆震强度及末端自燃时刻差异的主要原因,前期火焰传播速度较快的循环更容易对末端气体产生挤压作用从而促进自燃点的形成;此外,研究发现多个自燃核点、缸内压力与化学反应之间的耦合作用引发了较高的爆震强度,且第一个自燃点产生的压力波峰值往往最高,随后的自燃点由于没有充足的混合气参与化学反应,其压力波强度相对较低。Small reinforced gasoline engines achieve impressive power performances and excellent fuel economy,it suffers severe knocking problems.Our study is based on large eddy numerical simulation coupled with the G-equation model.We take knock combustion of spark ignition engines as the research object.The relationship between the cyclic fluctuation characteristics of SI engines and end gas spontaneous combustion and knock generation at different speeds is analyzed.Our results show,under the fixed spark ignition timing,the increase in rotational speed reduces the propagation speed of the main flame within the crankshaft corner time.The average fuel mass fraction point of 50% at a speed of 4000r/min is delayed by 4°compared to 3000r/min,resulting in a delay in the onset of knocking.Meanwhile,our findings show the different flame development rates in the early stages of combustion are the main reasons for the variations in knock intensity and end point auto-ignition time between cycles.Cycles with faster flame propagation speeds in the early stages are more likely to exert compression on the end gas,thereby promoting the formation of auto-ignition points.Moreover,the coupling effect between multiple auto-ignition nuclei,cylinder pressure,and chemical reactions leads to higher knock intensity.The pressure wave peak generated by the first auto-ignition point is often the highest while the pressure wave intensity of subsequent auto-ignition points is relatively low due to insufficient mixture participation in chemical reactions.

关 键 词：汽油发动机 循环波动 发动机爆震 发动机转速 大涡模拟 末端自燃 

分 类 号：TK411[动力工程及工程热物理—动力机械及工程]