Evolution of positive streamers in air over non-planar dielectrics: experiments and simulations

Abstract

We study positive streamers in air propagating along polycarbonate dielectric plates with and without small-scale surface profiles. The streamer development was documented using light-sensitive high-speed cameras and a photo-multiplier tube, and the experimental results were compared with 2D fluid streamer simulations. Two profiles were tested, one with 0.5 mm deep semi-circular corrugations and one with 0.5 mm deep rectangular corrugations. A non-profiled surface was used as a reference. Both experiments and simulations show that the surface profiles lead to significantly slower surface streamers, and also reduce their length. The rectangular-cut profile obstructs the surface streamer more than the semi-circular profile. We find quantitative agreement between simulations and experiments. For the surface with rectangular grooves, the simulations also reveal a complex propagation mechanism where new positive streamers re-ignite inside the surface profile corrugations. The results are of importance for technological applications involving streamers and solid dielectrics.

3D fluid modeling of positive streamer discharges in air with stochastic photoionization

“…where equation (39c) is the Poisson equation for the electric field E = −∇Φ where Φ is the electrostatic potential and ρ is the space charge density. This model has been implemented into the chombo-discharge 1 code, which we have used for streamer simulations in the past [26][27][28][64][65][66].…”

“…That is, the valid region of levels l − 1 and l + 1 are separated by at least one grid cell on level l, and boxes are disjoint (non-overlapping) on each level. As in previous publications relating to non-equilibrium gas discharges [26][27][28][64][65][66] we use the Chombo [67] library for handling the AMR infrastructure. Algorithmic details that are not specific to the Îto-KMC model are found in references [26-28, 64, 67].…”

Surface Flashover over a Profiled Cylinder in Air

“…If the use of sheds or barriers is not feasible, one less-explored alternative is to use small-scale profiles on dielectric surfaces to suppress discharge development along the surface. It was shown in previous work by the authors that streamers are inhibited by surface profiles that are of a similar spatial scale as the streamer front, which is a few hundred microns in atmospheric air [8,9]. Rectangular-cut trenches were strongly inhibiting, in both simulations and experiments.…”

“…Polyoxymethylene (POM) cylinders with 25 % glass fibre (ϵ r = 4.3) with 30 mm diameter were tested in the setup. Profiles were machined on the cylinder surface, with similar dimensions as the rectangular-cut profiles in previous work [9,10]. A non-profiled cylinder was used as a reference.…”

“…High-speed intensified images of the flashover process were taken in the Fig. 2b setup using the imaging setup described in [9]. The images were post-processed by adjusting brightness, contrast and color look-up table, and by overlaying an illuminated picture of the setup.…”