正流注传播动力学特性随气压湿度的变化

为了解流注传播电场测量中大气参数的影响,利用“三电极系统”研究了不同气压湿度条件下正流注的传播电场和传播速度。利用两个光电倍增管检测流注在平行极板间的传播,获得了流注传播电场的概率分布及平均传播速度,得到了无外加脉冲电压时流注传播的“稳态电场”与相对空气密度、湿度间的经验公式,并和其它研究者提出的公式进行了比较。研究表明:流注传播的“起始电场”和“稳态电场”随着外加脉冲电压的减小而增大,随着气压和湿度降低而减小;电场强度相同时,流注平均传播速度随着气压和湿度的增大而减小,其数量级为105m/s。

Variation of Propagation Dynamics of Positive Streamer with Pressure and Humidity

The propagation field and velocity of positive streamer are investigated under different pressures and humidity conditions through a three-electrode system.Two photomultipliers are directed to the cathode and earthed anode respectively to detect the streamer propagation in parallel plate electrodes.Once a voltage pulse is applied on the needle located in the hole at the center of earthed anode,streamer propagated upward to the cathode.The propagation probability is represented by the ratio of the number of streamers arriving at the cathode to the total number of produced streamers.The average propagation velocity is obtained by the gap distance divided by the time interval between two signals received by the photomultipliers.As the field between the plates rose,the streamer propagation probability increases,following an approximately normal distribution.The electric fields corresponding to 2.5% and 97.5% are termed as "threshold" field and "stability" field,respectively.Both increase as pulse voltage amplitude is declined and decrease as pressure and humidity decreases.The intrinsic "threshold" and "stability" fields required for the streamer propagation are determined through the extrapolation of experimental data.And an empirical equation for the intrinsic "stability" field is given as functions of relative air density and humidity.The results are compared with those calculated with the equations previously proposed by other investigators.The average propagation velocity decreases with the augment of pressure and humidity under constant electric field,which is at the order of 105m/s.