Numerical Simulation Of Vacuum Arc

From arc coating to electric propulsion systems,from automotive spark plugs to nuclear fusion devices,vacuum arcs plays an important role in the development of modern society.As a discharge phenomenon under extreme conditions,vacuum arc is not easy to obtain its properties from experiments.In order to overcome this problem,the study applied plasma discharge theory and numerical simulation method to simulate the vacuum arc.In recent years,there has been a method of numerical simulation analysis of parallel single element electrodes,which can predict the failure mode and service life of specific devices.However,with the development of electrode structure and materials,the methods applied to parallel and single element electrodes had not met the needs of modern society.The purpose of the study was to further extend the simulation of vacuum arc to the case of complex boundary,multi-element particles and three-dimensional.The study focused on the model construction and numerical calculation of the above extended functions,and analyzed the simulation results to summarize the influence of different boundary and electrode element composition on the vacuum arc phenomenon.In order to achieve the above functions,a vacuum arc simulation framework was constructed.The simulation methods used in the framework are Particle-In-Cell method and Direct Simulation Monte Carlo method.In the simulation process,the finite difference method was used to solve the Poisson equation of electromagnetic field,and an effective treatment scheme was proposed to solve the boundary electric field of complex electrode shape.The collision between particles was fully considered,and the collision process of particles was realized by using Coulomb collision and binary collision theory.The emission models of field electron emission,thermal emission,secondary electron emission and sputtering were established by the particle emission equation,and the model processing method in the emission area of rough surface was introduced.This paper introduces the construction of equivalent circuit of vacuum arc generator,and analyzes the current feedback of vacuum arc to external circuit.Aiming at the complex boundary problems,the intersection grid technology and the finite difference technology were combined to make full use of the simplicity and practicability of the finite difference on the basis of the curved boundary launching conditions.Aiming at the simulation process of vacuum arc under multielement electrode,the problem of energy distribution in particle emission was mainly considered.Aiming at the problem of three-dimensional simulation,the launch area of three-dimensional space rectangular coordinate system was studied,and the threedimensional solution program was compiled,and several particle emission methods of different launch areas were emphatically studied.In order to ensure the correctness of the models and algorithms,the model and solver were verified for each chapter.According to the simulation program,the electrode design innovation was carried out,and the simulation of the new electrode in the process of vacuum arc discharge was carried out.The arc shape and track were described by observing the particle motion path and particle distribution density,and the particle motion trend and ionization rate were analyzed;the electrode surface damage was analyzed by counting the boundary coordinates and number of particle removal;the V-A characteristic curve of vacuum arc was obtained by recording the charge removal amount and potential difference between electrodes at different times,which was used to analyze the continuity and stability of arc.According to the calculated results,it was found that different boundary and electrode materials have certain influence on particle trajectory,density,charge and energy distribution,arc formation and extinction process.