Numerical investigation of stability of low-current needle-to-plane negative corona discharges in air

TL;DR

This study investigates the stability conditions of negative corona discharges in air within a needle-to-plane setup, revealing how pulsed and pulseless modes occur over various voltages and aligning modeling results with experimental observations.

Contribution

It provides a comprehensive analysis of the conditions leading to pulsed and pulseless negative corona discharges in a needle-to-plane geometry, expanding understanding of their stability and transition mechanisms.

Findings

Stable negative corona exists immediately after ignition.

Discharges transition from pulseless to pulsed modes with increasing voltage.

Modeling results align with experimental current-voltage data.

Abstract

Negative DC corona discharges are known for their self-pulsing regime: the Trichel pulses. In some works, pulsed regimes, stochastic or periodic, have been observed immediately upon the inception of the discharge, while in other works the discharge was found to be ignited in a stedy-state (pulseless) mode, with the Trichel pulses developing at higher voltages. Recent theoretical and modelling work showed that the stationary negative corona between concentric cylinders in atmospheric-pressure air is stable immediately after the ignition. The pulseless mode was found also in the modelling of the needle-to-plane geometry, however in a quite narrow voltage range. This work studies conditions for a pulseless negative corona discharge in a needle-to-plane geometry to occur over a wide range of voltages, which will facilitate its unambiguous observation in the experiment. After the negative corona loses stability, the current evolution shows, after a small region of quasi-harmonic oscillations, pulses. These can be of small amplitude or regular Trichel pulses, which develop via standing-wave or ionization-wave mechanisms. Modelling results agree with available experimental data, both for the current-voltage characteristics and the stability limit of the pulseless negative corona discharge. An insight is given into stochastic Trichel pulses, which have been observed in experiments under certain conditions.