面向离子电流检测的火焰内电子输运机理研究

Electron Transport Mechanism in Flame for Ion Current Detection

离子电流检测技术有望解决未来点燃式发动机缸内实时诊断及精准反馈难题.业内对阳离子在离子电流形成中的作用已有较多研究,但对电子所扮演角色还缺乏系统分析及原理认知.本研究基于所构建的电子输运动力学平衡假设估计方法,估计了电子在火焰内的迁移率及扩散系数等关键参数.进而构建了定容燃烧弹离子电流形成机理模型,分析了不同外电场配置下火焰内电子的输运机制.得出结论在1 kV的低电压下,火焰内电子以双极扩散的方式运动;而在20 kV的高电压下,电子以单极扩散的形式,越过火焰锋面区域并到达探针附近.

Ion current detection technology is expected to solve the problems of real-time diagnosis and accurate feedback in the cylinder of spark ignition engine in the future.There have been many researches on the role of cations in ion current formation,but there is still a lack of systematic analysis of the role of electrons and knowledge of its principle.In this study,the key parameters,such as electron mobility and diffusion coefficient in flame,were estimated based on the proposed method of mechanical equilibrium hypothesis.Then the formation mechanism model of ion current in constant volume combustion chamber(CVCC)was constructed.The transport mechanism of electrons in flame under different external electric field configurations was analyzed.It is concluded that the electrons in flame move in the ambipolar diffusion mode at the voltage of 1 kV.At the voltage of 20kV,electrons spread across the flame front region in a form of unipolar diffusion and reach the probe.