当量比分层压燃的火焰发展特性与控制机制

Flame Development Characteristics and Control Mechanism of Equivalent Ratio Stratified Compression Combustion

针对柴油机当量比分层充量压缩着火的可控性问题,基于OpenFOAM平台构建了一维分层充量自燃及火焰发展的理论模型,在压力为6MPa、温度为850 K工况条件下,研究了当量比分层压缩燃烧过程的基本特征和控制机制,以及当量比分层策略对燃烧过程的调控作用.结果表明:当量比分层压燃早期的组分扩散对化学反应影响较大,中期主要受化学反应和压力波耦合后的共同控制,而后期化学反应和压力波解耦,主要受化学反应控制,压力波影响较小;小负荷工况(整体当量比为0.3)下通过组织合理的充量分层可以使50%放热对应的时间从1.312 ms缩短到0.685 ms,燃烧速度提高近1倍,而大负荷工况(整体当量比为0.7)下可以通过部分分层策略将50%放热对应的时间从0.357 ms延长到0.477 ms.

Based on the OpenFOAM platform,a theoretical model of one-dimensional stratified controllable compression ignition was constructed,and the basic characteristics and control mechanism of equivalent ratio stratified compression combustion process were studied at the pressure of 6MPa and the temperature of 850 K.The results show that the equivalent ratio has a greater influence on the chemical reaction than the diffusion of components in the early stage of compression ignition,and it is mainly controlled by the coupling of chemical reaction and pressure wave in the middle stage.While in the later stage,the decoupling of chemical reaction and pressure wave is mainly controlled by chemical reaction,and the influence of pressure wave is less.Under lower load(the equivalent ratio is 0.3),the combustion rate can be nearly doubled by proper organization of charge stratification and the time of 50%heat release is reduced from 1.312 ms to 0.685 ms.While under the higher load(the equivalent ratio is 0.7),the combustion rate can be prolonged by partial stratification strategy,and the time of 50%heat release is increased from 0.357 ms to 0.477 ms.