Discharge modes and characteristics optimization of nanosecond pulsed discharge in packed bed reactor

Abstract In this study, comparisons of spatiotemporal resolved images, optical emission spectroscopy technology, and electrical characteristics diagnosis were used to investigate the conversion and optimization of the discharge modes in a packed bed reactor (PBR) in which dielectric materials with different dielectric constants were employed under different peak voltages. The effects of the peak voltages and dielectric materials on the production of reactive species, such as N 2 ( C 3 Π u ) and N 2 + ( B 2 Σ u + ) , were also studied for plasma applications. The results show that, when a polytetrafluoroethylene (PTFE) column is employed, with an increase in the peak voltages, the form and modes of the discharge both change. First, the discharge channel becomes ‘wider’ and the discharge volume becomes larger, which results in more reactive species. Second, the discharge mode changes from surface discharge to diffuse discharge during the falling edge of the voltage pulse. When the dielectric constant of the dielectric material is increased, the intensity of the surface streamer decreases during its shorter propagation path because of more electron collision losses. Moreover, a different discharge mode, called ‘local discharge’, was observed at the contact point. Under the same experimental conditions, the numbers of nitrogen molecules distributed at different vibrational levels and the reactive species produced in the alumina PBR were fewer than those in the PTFE PBR.