Impact of different packing beads methods for streamer generation and propagation in packed-bed dielectric barrier discharge

The combination of plasma and catalyst can better promote the gas reaction for plasma catalysis. We used a two-dimensional particle-in-cell/Monte Carlo collision model to study the relationship between plasma behavior and dielectric beads with five different packing beads methods in a packed-bed dielectric barrier discharge in nitrogen gas at atmospheric pressure. The electron density, electric field, excitation rate, and ionization rate are calculated with different packing beads methods. As a result, either a change of the bead size or removing one bead can induce distinct features for plasma formation and streamer propagation. The electric field is enhanced near the beads and plates, resulting in a large tangential component to the dielectric surface, which gives rise to surface ionization waves (SIWs). The plasma streamer is generated between bead 1 and 2, then propagates to bead 4 and develops itself by surface SIWs along the bead 4 surface, yielding highest and uniform plasma density there with five packing beads. A positive streamer is generated after removing bead 2, and a volume discharge is developed for removing bead 4, asymmetric SIWs are induced with a smaller size of bead 4 while it becomes almost symmetric with a larger size of bead 4 for removing bead 5. The uniform and maximum ionization rate take place on the bead 4 surface, indicating the importance of bead 4 for packing. Moreover, the SIWs and positive streamers give rise to the highest plasma concentration due to the maximum ionization rate on the surfaces of the beads.