Characteristics of Negative Corona Discharge in Air at Various Gaps

The length of the air gap in a negative corona discharge, which affects many corresponding parameters in the discharge process, is of vital importance for the physical investigations. A hydrodynamic drift-diffusion approximation model considering photoionization utilizing the finite-element method has been used in needle-to-plane air gaps. Trichel pulses, pulse frequency, electron, and electric field distribution, and surface current density distribution on the anode plate were presented to study the effect of the gap length. An approximate exponential relationship was found to exist between the corona current and the gap length, and also a linear function was found between the pulse frequency and the gap length. The analysis shows that the characteristics of the Trichel pulse are strongly dominated by the length of the air gap.