The effects of different pellet shapes on streamer dynamics in patterned dielectric barrier discharges

Abstract Dielectric barrier discharges (DBDs) are frequently used for gas conversion for environmental protection by removing harmful components from gas streams and converting them into value added products. DBD operation is typically combined with catalysts placed on spherical dielectric beads in the plasma volume to enhance conversion rates and energy efficiency. However, the presence of such pellets blocks the gas flow and their random arrangement leads to unstable discharges. In this work, we use an advanced plasma source, the patterned DBD, where dielectric pellets are immersed into an electrode at fixed and controllable positions to enhance plasma stability and control. Based on experiments and simulations we study the effects of the pellet shape and the driving voltage on the spatio-temporally resolved dynamics of volume and surface streamers, that ultimately determine the generation of reactive species, plasma-catalyst coupling, and conversion rates/efficiencies via electron heating. The pellet shape is found to influence the streamer speed and the generation of energetic electrons. Via their effects on the effective capacitance of the pellet, shapes with a flatter plasma facing apex are polarized more strongly by approaching volume streamers. This results in a stronger local enhancement of the electric field at the apex, higher volume streamer speed, and more electron heating at this position. Depending on the surface topology maximum electron impact excitation of the background gas is observed at different locations along the pellet’s surface. Changing the polarity of the rectangular driving voltage waveform provides control of the direction of positive/negative streamer propagation and selectivity towards anode or cathode directed streamer movement.