低频交流电场对甲烷/空气预混火焰影响的机理研究

Mechanism Analysis on the Effect of Low-Frequency AC Electric Field on CH_4/Air Premixed Flame

为了明确低频交流电场对火焰的作用机理,在常温、初始压力0.3MPa下,施加电压有效值为5kV、频率f=40,60,80,100Hz的电场对甲烷/空气混合气的燃烧特性进行研究,建立了预混甲烷/空气火焰离子反应模型,对燃烧过程各粒子的浓度变化进行模拟,将实验与模拟结果综合进行了分析。结果表明:加载低频交流电场后,预混球形火焰在横向发生明显形变,随着频率的增大,平均火焰传播速度S_L和压力峰值Pmax均逐渐减小;模拟计算表明随着频率的增大,双离子风发展程度ξ_(eff)逐渐减小,平均火焰传播速度增大率ΔS_L和压力峰值增大率ΔPmax与双离子风发展程度ξ_(eff)的线性拟合相关系数分别为0.995 82和0.919 96,ξ_(eff)与电场对火焰的促进作用密切相关;电场下火焰前锋面粒子间的碰撞作用程度与火焰的宏观拉伸形变之间存在着直接联系,基于碰撞作用的双离子风效应是低频交流电场对预混火焰的主要促进因素。

The alternating electric field can promote flame combustion, and research shows that the promotion effect of low frequency AC electric field on premixed flame is mainly based on the collision between particles in the flame. In order to further explore the effect mechanism of the particles in the flame under electric field, premixed methane/air flame ionization model was established to obtain the concentration distribution of the particles in the combustion process and calculate the developing degree of bi ionic wind. Simulation results were compared with the experimental data. The results showed that the spherically flame was horizontally stretched obviously when low frequency AC field was applied. As the frequency increases, the average flame propagation velocity SL and pressure peak P decrease gradually. Simulation results also showed that the developing degree of bi ionic wind ΔSL decreases with the frequency, and the correlation coefficients of linear fitting of the average flame propagation velocity ASL and the pressure peak increase rate 2xP with the developing degree of bi ionic wind ξeff are 0. 995 82 and 0. 919 96, respectively. The parameter is closely related to the promotion of flame by the electric field. There is a direct relati and the macroscopic stretch of the fl based on the particles collision is the premixed flame. onship between the co ame under the applied primary promotion of llisi elec ons of particles in the flame front tric field. The bi ionic wind effect low frequency AC electric field on