The role of low air pressure in the variation of negative corona-generated space charge in a rod to plane electrode

The corona-generated space charge may vary in different air pressures, and the quantitative law between the corona-generated space charge density and air pressure has never been investigated. This work utilised computational approaches to explore the role of air pressure in the variation of negative corona-generated space charge. A negative fluid model in which the air pressure could be varied was built up to calculate the charged-particle density and electric field under different applied voltages. The continuity equations were solved by flux corrected transport algorithm and the Poisson equation was computed by the successive over relaxation method. The variations of important parameters due to air pressure were analysed. The particles densities of electrons, positive ions and negative ions at standard and low atmosphere pressures were computed, which increased markedly due to the decrease of atmosphere pressure. At fixed applied voltages, the exponential decay law between the maximal values of electron/positive ion densities at the head of the streamer and air pressure could be obtained. The quantitative law between the maximal values of electron/positive ion densities at the head of the streamer and the applied voltage, relative air density was also achieved.