准均质充气压缩点燃系统燃烧特性研究

Research on Combustion Characteristics of Quasi-Homogeneous Charge Compression Ignition Combustion System

准均质充气压缩点燃 (QHCCI)燃烧系统是在柴油机上实现稀薄预混合气燃烧的有效方法 ,建立了一个燃烧过程准维数学模型 ,结合试验结果 ,对 QHCCI系统的燃烧特性进行了研究。内容包括引燃柴油喷射定时对系统燃烧性能的影响 ,引燃柴油喷射量对系统的影响 ,以及发动机工作粗暴的特性。模拟结果与试验结果一致 ,并发现QHCCI燃烧系统的放热律曲线一般呈双峰 ,引起爆震的原因主要是引燃柴油喷射量大或喷射早造成上止点附近的大量剧烈燃烧造成的。

The quasi-homogeneous charge compression ignition (QHCCI) combustion system is an effective way to burn lean pre-mixture in diesel engine. A quasi-dimensional mathematical model is established to study the characteristics of QHCCI system in combustion. Based on the mathematical model together with the test results, the influences of pilot quantity and pilot injection timing on combustion, and the characteristic of hard combustion are investigated. The simulation results obtained by using the presented mathematical model are in good agreement with the test results. The results show that the heat release rate curve of the QHCCI system may usually have two peaks. It is also found that excessive pilot diesel and too early injection timing of pilot diesel, which result in large amount of heat release in a very short period near the top dead center, may be the main reasons for the knocking.