Streamer Propagation in Air in Non-Axially Symmetric Electric Field

Development of non-axial streamer discharges in air between disc-electrodes is studied. Discharge inception and propagation between edges of two flat discs is treated with so-called drift-diffusion model accounting for transport, generation and losses of electrons and two generic types of ions (positive and negative) under the influence of the electric field. To simulate propagation of a streamer channel, generation of secondary electrons at the streamer head due to photoionization is included. Partial differential equations constituting the model are solved utilizing custom developed stabilized finite element procedure implemented in commercial software. The results of the performed simulations show that discharge inception takes place in the regions of enhanced electrostatic fields at the curved edges of both electrodes and two streamers propagate in air gap towards each other. Quantitative analysis of the dynamics of charge carriers' densities, generated space charges and magnitudes of the electric fields during streamer initiation and propagation is presented. The effect of space charges and their influence on the streamer propagation path is discussed.