Numerical investigation of the formation of Trichel pulses in a needle-plane geometry

This paper presents a numerical investigation of the formation of the Trichel pulses in negative dc corona discharge for a needle-plane configuration in atmospheric air. A 2D axisymmetric model of the problem considering three charged species and consisting of a hyperboloid needle with a tip radius of 35 μm and needle-plane spacing of 6 mm over the voltage range of −3.5 kV to −12 kV has been studied. A commercial finite element package COMSOL was used for simultaneously solving three convection-diffusion equations along with Poisson's equation. In order to obtain a better understanding of the processes which lead to the pulse formation, a close look is taken at one of the pulses. The distributions of the major charged species and the timeline of peak-values of charged species densities and electric field are presented. Through tracing the evolution of the locations of the peak densities of the charged species some new insights have been provided. The configuration of the model was chosen so that the simulation results could be compared with the experimental data published by Lama and Gallo. The numerical results were in acceptable agreement with the experimental values. Some explanations are given for the discrepancies between experimental and simulation results. It is also shown, that as the frequency of the pulses increases with voltage, the transition from Trichel pulse discharge to glow discharge initiates and full glow discharge is reached at −12 kV.