The influence of oxygen concentration on the hollow cathode discharge in He/O₂ mixed gas

Abstract

Hollow cathode discharge in He/O2 mixed gas is simulated using a two-dimensional fluid model for the first time. The model contains 15 particles and 66 reactions. The evolutions of discharge current, electric field, charged and reactive particles with different oxygen concentrations are obtained. The primary mechanisms of generation and loss for particles under different oxygen concentrations are discussed. The results show that the added O2 in helium has both positive and negative effects on the discharge. The discharge does not monotonically change with the increasing oxygen concentration. When the oxygen concentration is low, oxygen admixture could enhance the discharge, that is, the discharge current, radial electric field, electron density, O+ 2 density, O density, and the O(1D) density increase with the increase of oxygen concentration. When the oxygen concentration is high, it will weaken discharge, that is, the discharge current, radial electric field, electron density, O+ 2 density, O density, and the O(1D) density decrease with the increase of oxygen concentration. The main reactive particles in discharge are O and O(1D). These densities are much higher than the density of charged particles. The optimal oxygen concentration for O and O(1D) is 0.5% and 0.4%, and the corresponding maximum density is 4.34×1013 cm-3 and 1.50×1013 cm-3. The generation and loss rates for these particles at different oxygen concentrations are calculated, which contributes to the change in particle densities.

Arc stability and ablation characteristics in O2, N2, and air environments

“…The arc extinguishing characteristics under the different gas environments and pressures are analyzed in depth. The main reason for the significant decrease in the arc breaking distance of the oxygen with the increase in gas pressures is that oxygen is an electronegative gas with a strong ability to adsorb electrons [23][24][25][26]. The concentration of oxygen increases as the gas pressure rises, when the gas pressure of the oxygen environment is higher (i.e., the oxygen concentration is larger), the oxygen has a stronger adsorption capacity for electrons, which leads to a rapid decrease in the electron number density in the arc channel and a faster arc extinction.…”