Parametric Study of the Characteristics of Trichel Pulses from Negative Needle to Plane Coronas

Abstract

A 2D axisymmetric model of the problem considering three charged species is used to study the impact of the needle tip radius, the needle to plane spacing, and the photoionization on the negative corona discharge in atmospheric air. The commercial software COMSOL is used to simultaneously solving three convection-diffusion equations, Poisson’s equations and the three-exponential Helmholtz equations. The Trichel pulse frequency, corona current, electron density and the distribution of electric field will be discussed. The simulation results suggest that the peak electric field is closely related to the needle tip radius, thus the characteristics of the corona pulse are significantly affected by the needle tip radius. The Trichel pulse frequency and the time averaged corona current are both inversely proportional to the needle tip radius. However, the Trichel pulse can not be realized with needle tip radius equal to or larger than 0.1 mm. The electric field is weakened by the increase of the needle to plane spacing, resulting in a decrease of the Trichel pulse frequency and the corona current. The numerical results are in acceptable agreement with the experimental values. The effect of photoionization is fairly small in negative corona discharge. The peak of the first pulse current could be slightly weakened by photoionization, but the peak and the start time of current pulses are unaffected by photoionization.