杂质对尾流化学动力学和电子密度的影响

Effects of Impurities on Wake Chemical Kinetics and Electron Density

本文研究杂质对尾流化学动力学与电子密度的影响。这种影响是通过把杂质(Na、H_2O、F_2、C_2F_4)加入到空气尾流中,进行数值模拟计算而获得的。化学体系是由26种粒子,35个化学反应组成的。为了独立地判断各类化学反应(杂质)的作用,把复杂的化学体系分解为由简到繁的九个化学子体系,它们是:Air、Air-Na、Air-F_2、Air-C_2F_4、Air-C_2F_4-F_2、Air-H_2O-Na、Air-F_2-Na、Air-C_2F_4-Na、Air-C_2F_4-F_2-Na。计算结果表明,杂质对尾流电离起着明显的影响,特别是Na,它能使纯空气尾流电子密度增加1～3个量级。另外也表明,与Air-F_2子体系一样,Air-C_2F_4子体系的电子衰减的主要机理是F_2、F对电子的吸附反应,该反应产生大量F^-离子,同时清除了尾流中大部分电子。

The present paper studies the effects of impurities on wake chemical kinetics and wake ionization.Such effects are examined through computation of wake flows composed of H2O. F2. C2F4 and Na-containing species added to the air constituents. A 26 species, 36 reactions chemical system is considered. An exact finite difference method for solving the axisymmetric boundary layer equations for chemical nonequilibrium wake flow is employed for both laminar and turbulent flows region.In order to ascertain a variety of effects separately, nine different chemical subsystems of increasing complexity are treated. These are pure air, air-Na, air-F2, air-C2F4. air-F2-C2Fa, air-H2O-Na, air -F2-Na, air-C2F4-Na and air-C2F4-F2-Na. Calculated results demonstrate that impurities exert significant influences on wake ionization.Especially sodium can enhance electron concentration of pure air by 1-3 order of magnitude and that as with the air-F2 subsystem, eletron decay mechanism of air-C2F4 chemical subsystem is the electron attachment reactions of fluoren molecules, fluoren atoms which results in production of negetive F ions and removes most of electron.