Two-dimensional particle-in cell/Monte Carlo simulations of a packed-bed dielectric barrier discharge in air at atmospheric pressure

Abstract

The plasma behavior in a parallel-plate dielectric barrier discharge (DBD) is simulated by a two-dimensional particle-in-cell/Monte Carlo collision model, comparing for the first time an unpacked (empty) DBD with a packed bed DBD, i.e., a DBD filled with dielectric spheres in the gas gap. The calculations are performed in air, at atmospheric pressure. The discharge is powered by a pulse with a voltage amplitude of −20 kV. When comparing the packed and unpacked DBD reactors with the same dielectric barriers, it is clear that the presence of the dielectric packing leads to a transition in discharge behavior from a combination of negative streamers and unlimited surface streamers on the bottom dielectric surface to a combination of predominant positive streamers and limited surface discharges on the dielectric surfaces of the beads and plates. Furthermore, in the packed bed DBD, the electric field is locally enhanced inside the dielectric material, near the contact points between the beads and the plates, and therefore also in the plasma between the packing beads and between a bead and the dielectric wall, leading to values of $4\times {10}^{8}$ V m ^−1 , which is much higher than the electric field in the empty DBD reactor, i.e., in the order of $2\times {10}^{7}$ V m ^−1 , thus resulting in stronger and faster development of the plasma, and also in a higher electron density. The locally enhanced electric field and the electron density in the case of a packed bed DBD are also examined and discussed for three different dielectric constants, i.e., ${\epsilon }_{r}=22$ (ZrO _2 ), ${\epsilon }_{r}=9$ (Al _2 O _3 ) and ${\epsilon }_{r}=4$ (SiO _2 ). The enhanced electric field is stronger and the electron density is higher for a larger dielectric constant, because the dielectric material is more effectively polarized. These simulations are very important, because of the increasing interest in packed bed DBDs for environmental applications.

Keywords

• streamer
• dielectric-barrier discharge
• packed bed dielectric-barrier discharge
• particle-in-cell
• atmospheric pressure discharge