棒-板电极直流负电晕放电脉冲过程中的电子特性研究

Simulation of Characteristics of Electrons During a Pulse Cycle in Bar-Plate DC Negative Corona Discharge

为了揭示负电晕放电过程的电子特性,本文对棒-板间距3.3mm,施加电压-5.0kV,大气压强1.0atm(1atm=101 325Pa),环境温度300K时的空气(N_2:O_2=4:1)负电晕放电微观过程进行数值计算,该过程主要通过求解改进的电子连续性方程、电子平均能量方程、重粒子连续性方程和泊松方程实现,计算结果表明单次脉冲的波形特性和实验结果符合较好。文中选取单次脉冲持续周期内的6个典型时间点对负电晕放电过程中的电子特性进行详细描述,结果表明:电子温度的最大值出现在场致电离区,随着放电时间的发展由阴极向阳极移动,温度值也随之减小。电子密度在阴极鞘内近似为0,在阴极鞘外层具有最大值,随着放电时间的增加,电子分布区域由阴极向阳极扩展,并且棒-板间隙内的电子密度逐渐增加。R_1和R_2分别为与N_2和O_2有关的碰撞电离反应,是电子增殖的主要过程,在整个放电过程中R_1和R_2的反应速率几乎保持一致;R_(17)是涉及N_2、N_2^+和电子的三体复合反应,在电子消散过程中占绝对优势。

In order to explore the characteristics of electron in DC negative corona discharge,microscopic process of negative corona discharge in air is simulated in this paper.The numerical computation is established with a bar-plate electrode configuration with an inter-electrode gap of 3.3mm,the negative DC voltage applied to the bar is 5.0 kV,the pressure in air discharge is fixed at 1.0atm,and the gas temperature is assumed to be a constant(300K).And the solution of the microscopic mechanism for corona discharge is to convert the electron conservation equation,electron mean energy conservation,heavy species multi-component diffusion transport equation,and the Poisson's equation into the appropriate system of partial differential equations,which are then normalized and solved using discrete numerical difference equations.Using individual discharge current waveform,the effectiveness of this developed model is validated by experimental results.Based on this simulation model,characteristics of electrons at 6 representative time points during a pulse are discussed emphatically.The obtained results show that,the maximum number of electron temperature appears in field ionization layer which moves towards the anode as time progresses,and its value decreases gradually.Within a pulse process,the electron density in the cathode sheath region almost keeps zero,however,it increase sharply to its maximum value at the cathode sheath outer layer.The electron density distribution move towards the anode,and the density of space increase gradually with time progresses.Among all reactions,R_1 and R_2 which are electron collision reaction associated respectively with N_2 and O_2 regarded as the main process of electron proliferation,besides,reaction rates of R_1 and R_2 almost keep the same curve.R_(17) is a recombination reaction of N_2,N_2 and e,which play a dominant role in the dissipation process of electron.The obtained results will provide valuable insights to the physical mechanism of negative corona discharge in air.The obtained results will provide valuable insights into the physical mechanism of positive corona discharge in air.