空燃比对离子电流信号的影响机理

在一台高压定容燃烧弹上,以甲烷为燃料,研究了空燃比对离子电流信号的影响.结果表明,当过量空气系数为0.90时,离子电流信号峰值最大,峰值时刻最为提前.通过建立甲烷预混离子反应机理模型,对离子形成过程、浓度及分布情况进行了数值模拟,结果表明,化学电离发生在火焰前锋面,最主要的离子产物为H3O~+,热电离发生在焰后高温区,最主要的离子产物为NO~+.化学反应路径分析表明,当过量空气系数为0.90时,H3O~+和NO~+的净生成速率最大,浓度最高,化学电离峰和热电离峰值最大.

Effect Mechanism of Air/Fuel Ratio on Ion Current Signal

The effect of air/fuel ratio on ion current signal was studied with methane as the fuel in a high pressure constant combustion vessel. The results show that the peak value of ion current signal is the highest and the peak timing is also the most advanced when the excess air ratio is 0.90. The ion formation process, concentration, and distribution were numerically simulated with the established methane ionization mechanism model. The simulation results show that chemical ionization occurs in the flame front and the main ion product is H3O+ while thermal ionization occurs in the high temperature post flame area. The main ion product is NO+. Chemical reaction path analysis results indicate that when the excess air ratio is 0.90, and the neat production rate and concentration of H3O+ and NO+ are the highest, which results in the highest value of chemical ionization peak and thermal ionization peak.