3D PIC-MCC simulations of positive streamers in air gaps

Abstract

Simulation of positive streamer evolution is important for understanding the microscopic physical process in discharges. Simulations described in this paper are done using a 3D Particle-In-Cell, Monte-Carlo-Collision code with photoionization. Three phases of a positive streamer evolution, identified as initiation, propagation, and branching are studied during simulations. A homogeneous electric field is applied between parallel-flat electrodes forming a millimeter air gap to make simulations and analysis more simple and general. Free electrons created by the photoionization process determine initiation, propagation, and branching of the streamers. Electron avalanches form a positive streamer tip, when the space charge of ions at the positive tip dominates the local electric field. The propagation of the positive tip toward a cathode is the result of combinations of the positive tip and secondary avalanches ahead of it. A curved feather-like channel is formed without obvious branches when the electric field between electrodes is 50 kV/cm. However, a channel is formed with obvious branches when the electric field increases up to 60 kV/cm. In contrast to the branches around a sharp needle electrode, branches near the flat anode are formed at a certain distance away from it. Simulated parameters of the streamer such as diameter, maximum electric field, propagation velocity, and electron density at the streamer tip are in a good agreement with those published earlier.

Comparison of six simulation codes for positive streamers in air

“…Besides fluid models, particle-in-cell (PIC) codes can also be used to simulate streamer discharges, see e.g. [43][44][45][46][47]. In PIC codes, the velocity distribution function f t…”

Positive and negative streamer propagation in volume dielectric barrier discharges with planar and porous electrodes

“…Several models have been developed to investigate the underlying mechanisms and characteristics during positive streamer propagation in N 2 –O 2 mixtures, including particle, fluid, and hybrid models. [ 14‐19 ] All these models emphasize that the evolution of positive streamer discharges mainly depends on the presence of nonlocal photoionization around the streamer head in N 2 –O 2 mixtures. Furthermore, the streamer branching profile largely depends on the concentration of photoelectrons.…”

Current pulse characteristic analysis of typical void and point partial discharge based on PIC‐MCC method

“…In this way, electron avalanche is generated as Townsend discharge theory described, the growing process of electron and nitrogen motion trail in the void is shown in Fig. 5 [15,16].…”