Streamer propagation characteristics of nanosecond pulsed discharge plasma on fluidized particles surface: experimental investigation and numerical simulation

Plasma fluidized-bed contributes to strengthening the interaction between active species in plasma and fluidized powder particles, resulting in higher active species utilization efficiency and superior powders processing/modification performance. However, the plasma streamer dynamics on the fluidized powder particles are still unclear due to the intricacy of plasma fluidized-bed. In this work, the time-resolved evolution behavior of plasma streamers on fluidized powder particles surfaces has been explored in plasma fluidized-bed system based on a simplified pin-cylinder configuration. The results reveal that the entire streamer propagation process includes volume discharge and surface discharge. The maximum electron density generated by surface discharge is one order of magnitude higher than that produced by volume discharge, indicating that surface discharge plays a dominant role in powder particles modification. The presence of fluidized particle will cause streamer branching, and the main streamer splits into two independent sub-streamers for propagation in a 'parabola-like' shape. Compared with large-size fluidized particles (1000 mu m), streamer wraps a larger area on micron-size fluidized particles (200 mu m), with a 78% increase in the coverage area, which is favorable to the modification of powder particles. Furthermore, the evolution of active species on fluidized particle surface is analyzed. The active species (N, O, O2 -) are mainly distributed around the north pole, and N2 + is mainly distributed between 25 degrees and 50 degrees of the particles. With the decrease of fluidized particle size, the polarization effect between particles is significantly enhanced, and the maxima of the number densities of active species increase. These findings help to get a better understanding of the interaction between plasma and fluidized particles in fluidized systems.