Abstract
In this paper, a modified COMSOL Multiphysics model with artificial stability is adopted, and the boundary condition developed in the previous paper are applied to the calculation of the photoionization rate. The main processes involved in air discharge were simulated by 39 plasma chemical reactions composed of 12 kinds of particles. The characteristics of low-temperature sub-atmospheric pressure air discharge under unipolar square wave pulse voltage with 13kV applied amplitude, 25 kHz-50 kHz frequency and a duty cycle of 50%-75% are discussed. The results show that: When the duty cycle increases, the average density of electron, N2+, N4+, O2+, O4+, and N2O2+ show an increasing trend, and the average electron temperature changes little; When the frequency increases, the average electron density, the average density of N4+ and O4+ show a downward trend, the average density of N2+, O2+, N2O2+ change little; The average electron temperature shows an increasing trend, but the duration of high electron temperature becomes shorter. When discussing a single period, it is found that the potential difference between the electrode and the plasma determines the direction of the electric field in the space. For the photoionization reaction, even if its influence on the negative streamer is not important, it still needs to be considered in the simulation. The effect of temperature on discharge is also taken as the research emphasis, it includes the following aspects: Firstly, at low temperature, the collision reaction and attachment reaction rates are increased, while the recombination reaction rate is almost unaffected; Secondly, low temperature results in the decrease of secondary electron emission coefficient, which indirectly increases the electric field gradient and the peak value of electric field; Finally, at low temperature, the mobility of carriers, including electrons, positive and negative ions, is increased, but the streamer velocity is decreased.
Highlights
As one of the main forms of gas discharge, streamer discharge has always been a fundamental issue that has attracted much attention in electrical engineering
With the further development of China’s aviation industry, under the premise of satisfying safe operation, studying the air discharge characteristics of aircraft in a low temperature sub-atmospheric environment has become a common issue between aviation and high voltage engineering
Lymberopoulos and Economou [14], [15] used a fluid model to study the development process of argon discharge between parallel plates, and the results show that the number of metastable argon atoms in the discharge process is small, they have a greater impact on the discharge process
Summary
As one of the main forms of gas discharge, streamer discharge has always been a fundamental issue that has attracted much attention in electrical engineering. Passchier and Goedheer [13] used a one-dimensional fluid method to simulate the air discharge process between parallel plates by using the particle migration-diffusion approximation, but the model assumes that the electron energy distribution function is in thermal equilibrium. In the radio frequency discharge model, it is assumed that the electron energy is distributed in a Maxwellian mode and the chemical reaction process between particles in the air is not considered. The establishment of this model is of great significance for studying the electron temperature, electron density, streamer radius and other microscopic parameters during air discharge at low temperature and sub-atmospheric pressure. It is necessary to calculate the accurate electron energy distribution function according to the Boltzmann equation to obtain the plasma chemical reaction rate and transport coefficient.
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