基于PIC/MCC法爆炸性气体环境下的微尺度放电特性

Micro-scale Discharge Characteristics in Explosive Gas Environment Based on PIC/MCC Method

为了研究爆炸环境下微间隙放电的微观特性,以国际标准IEC火花试验装置为研究对象,建立了瓦斯与空气混合气体环境下,以钨丝为阳极和镉盘为阴极的二维平行板放电仿真模型。采用粒子法(PIC/MCC)进行仿真,研究了平行板极间电压为295 V、极距为5μm的微间隙放电动态过程;从微观层面分析了爆炸性气体环境下微尺度放电机制,同时讨论了极距和瓦斯体积分数等因素在放电过程中对微观粒子的影响,进而揭示这些因素对放电电压和电流特性的影响。最终的仿真结果表明:极距在5μm时微间隙放电的主要机制是场致发射,而并非是以碰撞电离及电子雪崩为主要特征的气体放电,放电过程中CH类离子粒子数并未有明显变化而电子数量变化较为明显;当极距为15μm时,微间隙放电的主要机制是气体发生雪崩式电离,混合气体中的甲烷体积分数会影响放电结果:甲烷体积分数在3.5%~13.5%范围内时,体积分数每增加5%,放电中阳极吸收电流就会增加10 mA,在微观上表现为随着混合气体中甲烷体积分数的不断增加,CH类离子产生的速率也会有所提高,且甲烷气体在放电过程中贡献程度也在不断增加。并搭建了爆炸环境下微间隙放电试验平台,进一步从实验方面验证了改变极间距离时微观粒子的变化所表现出的宏观特性。

In order to study the micro-characteristics of the micro-gap discharge in an explosive environment, taking the international standard IEC spark test device as the research object, we established a simulation model of two-dimensional parallel plate discharge in a gas and air mixed gas environment with a tungsten wire as the anode and a cadmium disc as the cathode. The particle method(PIC-MCC) was used for simulation to study the dynamic process of micro-gap discharge with a voltage between parallel plates of 295 V and a pole pitch of 5 μm. The micro-scale discharge mechanism in an explosive gas environment was analyzed at the micro level, and the electrode was discussed. The influence of factors such as distance and gas concentration on microscopic particles during the discharge process reveals the influence of these factors on the discharge voltage and current characteristics. The final simulation results show that the main mechanism of micro-gap discharge when the pole distance is 5 μm is field emission, rather than gas discharge characterized by impact ionization and electron avalanche. The number of CH ion particles during the discharge process negligibly changes. When the pole distance is 15 μm, the main mechanism of micro-gap discharge is gas avalanche ionization. The methane concentration in the mixed gas will affect the discharge result as follows: when the methane concentration is in the range of 3.5%~13.5%, the anode absorption current during discharge will increase by 10 mA with every 5% increment in the concentration. At the microscopic level, as the methane concentration in the mixed gas continues to increase, the rate of CH ion generation will also increase, and the methane gas will increase. The contribution of the discharge process is also increasing.Moreover, a micro-gap discharge test platform in an explosive environment is built to further verify the macroscopic characteristics of the change of the microscopic particles when the distance between the electrodes is changed.