基于FEM-FCT算法的SF_6/N_2混合气体中棒-板间隙电晕放电特性的仿真研究

Corona Discharge Simulations of Rod-Plate Gap in SF_6/N_2 Gas Mixtures Using FEM-FCT Method

为研究棒-板间隙中SF6/N2混合气体流注电晕放电特性,采用二维流体力学模型,基于不固定网格剖分,利用有限元-通量校正传输(FEM-FCT)法求解含带电粒子的连续方程,并耦合泊松电场研究空间电荷对场域的畸变作用。实现了50%～50%SF6/N2混合气体二维流注电晕放电过程的仿真,考虑了带电粒子及中性气体分子的电离、吸附、复合、扩散等过程。并首次综合考虑SF6/N2混合气体中空间光电离与阴极光发射在流注放电过程中的作用。研究了棒头半径和间隙距离与流注电晕放电的关系以及SF6含量对混合气体放电的影响。仿真结果表明当间隙距离不变(d=4mm),逐渐减小棒头半径或棒头半径不变(r=1mm),间隙距离逐渐减小时,都可使流注电晕放电从相对稳定过渡到不稳定,进而放电会持续向前发展;50%～50%SF6/N2混合气体发展为不稳定放电的电压高于纯SF6气体和10%～90%SF6/N2混合气体。

The fluid method is used to analyze streamer corona discharge mechanism in rod-plate gap in SF6/N2 gas mixtures which is the most promising substitute for SF6. The finite element method-flux corrected transport technique （FEM-FCT） based on the unstructured mesh is used to solve the continuity equations for electrons, positive ions, and negative ions. The finite element method （FEM） is used to solve Poisson electric field distortion by space charge. Two-dimension simulations of cylindrically symmetric streamer corona discharge process in rod-plate gap with different gap distances and different rod tip radius in 50%450% SF6/N2 gas mixtures is achieved. The effects of photoemission and photoionization as well as ionization, attachment, recombination, electron diffusion is taken into account. The densities of different particles and the electric field distributions are described in the development process of streamer corona. The simulations when the gap distance is constant, the streamer corona discharge becomes relatively stable with rod tip radius Increasing; when rod tip radius is constant, streamer corona discharge becomes unstable with the gap distance decreasing, and the discharge will continue. The instable corona discharge voltage of 10%~90% SF6/N2 gas mixtures and SF6 is lower than 50%4 50% SF6/IN2 gas mixture.