交流电场气动效应对球形传播火焰影响的数值研究

Numerical Simulation for AC Electric Field Aerodynamic Effect on Spherically Expanding Flame

为了验证电场对球形传播火焰的影响机理,通过采用给球形传播火焰锋面组分添加交变动量源项的方法,模拟了交流电场作用下火焰锋面受力产生的气动效应,以预测电场对球形传播火焰影响的机理。在N-S方程中通过为火焰锋面添加以流动时间t函数形式的水平方向动量源项并采用Fluent软件,来模拟交流电场对甲烷-空气球形传播火焰的拉伸影响,模拟时过量空气系数为1.6,体积力有效值恒为30 750N/cm^3,交变频率分别为10Hz、100Hz和1 000Hz。模拟结果表明：在交流电场下,低频时电场对火焰的拉伸作用较为明显,在此阶段气动效应是电场对火焰形变产生影响的主要因素;高频时没有发现火焰出现明显的拉伸现象,可以推断此时气动效应不是电场对火焰影响的主要因素;气动效应的界定频率的数量级可以通过数值模拟来估计,约在10^2~10^3 Hz左右。

To verify the mechanism of electric field acting on spherically expanding flame, by adding alternating momentum source items to flame surface, the aerodynamic effect under an AC electric field is simulated to predict the mechanism that electric field affects spherically expanding flame. CFD software Fluent is used to simulate the stretch effect resulting from AC electric field acting on methane/air premixed flame. A horizontal momentum source term consisting of flowing time is added into N-S equation, and excess air coefficient is taken as 1.6, volume force as 30 750 N/cm^3, and AC frequency as 10 Hz, 100 Hz and 1 000 Hz, respectively. The results show that for low frequency AC field, stretch effect on the flame is more obvious, aerodynamic effect gets the primary reason of flame deformation in this stages for high frequency AC field, stretch effect on flame surface has not been found. Thus the magnitude of effective frequency is estimated within 10^2-10^3 Hz.