汽油均质压燃燃烧的自由离子生成机理研究

Study on Flame Ionization Mechanism of HCCI Combustion Fueled with Gasoline Fuel

将Warnatz离子生成机理耦合到异辛烷详细化学反应动力学模型中,研究了汽油均质压燃(HCCI)燃烧中H3O+、CHO+、e等离子或CH、O自由基的生成过程.采用了化学反应路径分析的方法研究了自由离子的生成过程.基于一台改造的双缸汽油机,试验研究了不同进气温度下,汽油HCCI燃烧的离子电流信号特性,并基于上述方法,对不同进气温度下离子电流变化特性的机理进行了分析.结果表明:通过化学反应路径分析能够得到某反应时刻混合气中各组分的生成情况及燃烧离子来源情况.不同进气温度下的缸内温度对CH自由基的生成起着关键作用;H3O+离子浓度的降低是离子电流幅值下降的直接原因.离子电流信号差分峰值相位、H3O+浓度差分峰值相位与放热率峰值相位之间均存在一定的相位差.

By coupling Warnatz’s ion formation mechanism with detailed iso-octane oxidation mechanism,a chemical kinetics model was set up to investigate the formation process of free ions in HCCI combustion flame fueled with gasoline fuel.A method that analyzes the formation process of free ions through chemical reaction path was presented.Experiments on the ion current signal characteristic of HCCI combustion at different intake temperatures were conducted on a modified two-cylinder engine.The mechanism of ion current variation characteristics was analyzed.Results show that species formation characteristic in the mixture and source of free ions can be obtained through chemical reaction path analysis at certain reaction timing.In-cylinder temperatures under different intake temperatures dominate the formation of CH radical.Decreasing in H3O＋ concentration leads to decrease in ion current amplitude.Results also show that differential peak phase of ion current signal or H3O＋ concentration slightly postpones to the peak phase of heat release rate.