基于分形理论的微间隙空气放电  

Micro gap air discharge based on fractal theory

作　　者：赵大帅 孙志[1] 孙兴 孙怀得 韩柏[1] Zhao Da-Shuai;Sun Zhi;Sun Xing;Sun Huai-De;Han Bai(School of Electrical and Electronic Engineering,State Key Laboratory Breeding Base of Dielectrics Engineering,Harbin University of Science and Technology,Harbin 150080,China)

机构地区：[1]哈尔滨理工大学电气与电子工程学院,电介质工程国家重点实验室培育基地,哈尔滨150080

出　　处：《物理学报》2021年第20期193-205,共13页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51607048);哈尔滨理工大学大学生创新训练项目(批准号:202010214166)资助的课题。

摘　　要：微间隙放电是放电间距和电极尺寸均在亚毫米及以下量级的气体放电形式.为研究微米间隙放电起始路径及放电过程中粒子密度的变化机理与规律,本文搭建了大气压下微间隙空气放电实验及放电图像采集装置,采用COMSOL仿真软件对微间隙空气放电过程中的电子密度、空间电荷分布进行模拟,并使用MATLAB软件计算微间隙放电的分形维数与概率发展指数.实验研究在大气压室温下、间隙距离为50—150μm时,针尖施加正极性直流电压的空气放电现象.实验发现,放电通道存在曲折段,放电过程中分叉数比长间隙情况少,原因为放电机制以汤森理论为主,流注理论为辅,存在弱流注形式,放电通道呈曲折和分支状,但分叉数较少,曲折度较低.使用COMSOL模拟得出,在阴极形成鞘层,阴极电场畸变为原来的3—8倍,放电过程中电子密度最高达到2.17×10^(21) m^(–3).使用分形理论仿真来模拟微间隙放电,发现分形维数与电压和间隙距离成正比;当概率发展指数h=1.18—1.3时,模拟放电过程的分形维数与实验较接近.本工作为进一步探索亚微米-纳米间隙的放电情况打下了基础.Micro-gap discharge is a form of gas discharge in which the discharge gap is on the order of sub-millimeters orless.To study the initial path of micro-gap discharge and the mechanism and law of particle density change during discharge,in this paper a micro-gap discharge experiment and discharge image acquisition device under atmospheric pressure is built and the COMSOL simulation software is used to simulate the electron density and space charge in the process of micro-gap air discharge.Furthermore,the MATLAB software is used to calculate the fractal dimension and probability development index of micro-gap discharge.The air discharge phenomena produced by applying positive DC voltage to needle tip at atmospheric pressure and room temperature with gap distance ranging from 50μm to 150μm are studied.It is found experimentally that there are twists and turns in the discharge channel,and the number of bifurcations in the discharge process with a short gap is less than that with a long gap.Observation of the micro-gap air discharge process with a gap of 100μm under atmospheric pressure shows that the discharge process is divided into the following three processes:needle tip corona,corona breakdown streamer,and spark discharge channel.Based on the analyses of these experimental results,it can be concluded that the discharge mechanism follows Thomson’s theory,supplemented by the streamer theory.The cathode secondary electron emission(including positive ions colliding with the cathode and photoelectron emission)and the space charge distortion electric field form a secondary electron avalanche to maintain the discharge together.The seed electrons formed by a small amount of space photoionization also form an electron avalanche under the action of the space charge distortion electric field.There are tortuous sections in the discharge channel,but the number of branches is small and the degree of tortuosity is low.Therefore,there are weak streamer forms.The discharge channel is tortuous and branched,but the number of bi

关 键 词：微间隙放电 分形 空间电荷 概率发展指数 

分 类 号：O461[理学—电子物理学]