棒—板电极直流负电晕放电特里切尔脉冲的微观过程分析

Numerical simulation of Trichel pulse characteristics in bar-plate DC negative corona discharge

本文基于流体动力学理论改进出一种新的棒-板电极负电晕放电混合数值模型,模型中加入了27种主要碰撞反应,并考虑了光电离和二次电子发射过程.对棒-板间距3.3mm,施加电压-5.0kV情况下进行数值计算,得到负电晕放电的特里切尔脉冲.重点分析了单个特里切尔脉冲持续过程中5个关键时刻的微观特征量发展规律,丰富并量化描述了特里切尔脉冲的微观过程,主要结论如下:随着放电时间的发展,电场集中分布区域向阳极移动且幅值变小,这对电子崩的发展非常不利.大部分放电区域都是电中性的,只有在阴极鞘和阳极鞘附近有带正电的等离子体特性,带负电的离子云随着放电时间的发展缓慢向阳极发散式移动.整个特里切尔脉冲持续过程中,阴极鞘内电子密度几乎为0;特里切尔脉冲前期,阴极鞘附近电子密度迅速增加至最大值并保持基本不变;随着放电时间的增加,放电间隙内电子密度整体增加,并且向阳极发展.在特里切尔脉冲后期,电子的产生主要来自于N2和O2的碰撞电离,电子的消失则主要由N+2的复合决定,O+4和O-2分别是数量最多的正离子和负离子.

An improved multi-component two-dimensional hybrid model is presented for the simulation of Trichel pulse corona discharge. The model is based on the plasma hydrodynamics and chemical models, including 12 species and 27 reactions. In addition, the photoionization and secondary electron emission effects are taken into account. Simulation is carded out on a bar-plate electrode configuration with an inter-electrode gap of 3.3 mm, the positive potential applied to the bar being 5.0 kV, the pressure in air discharge being fixed at 1.0 atm, and the gas temperature assumed to be a constant （300 K）. In this paper, some key microscopic characteristics such as electric field distribution, net charge density distribution, electron density distribution at 5 different instants during a Trichel pulse are analyzed emphatically. Further more, the electron generation and disappearing rates, positive and negative ion distribution characteristics along the axis of symmetry are also investigated in detail in the later Trichel pulse cycle. The results can give valuable insights into the physical mechanism of negative corona discharge.