Simulation of pulsed positive streamer discharges in air at high temperatures

Two-dimensional simulations of an atmospheric-pressure streamer discharge at high gas temperatures were performed in humid air at initial gas temperatures, T ₀, in the range 300 K-600 K with the same electrode and applied voltage conditions as those used in Ono and Kamakura (2016 Plasma Sources Sci. Technol. 25 044007). The simulation was validated by comparing its results to experimentally obtained discharge currents, primary streamer velocities, and secondary streamer diameters and lengths. This paper discusses the mechanisms underlying the temperature effects in terms of the behaviour of the charged particles in the primary and secondary streamers. At T ₀ = 300 K, the main decay processes in the primary streamer are the electron recombination reactions with cluster ions and electron three-body electron attachment with O₂ and H₂O, while the main decay process in the secondary streamer is the two-body electron attachment to O₂. Although, at T ₀ = 600 K, the main decay processes in both streamers are still recombination and two- and three-body electron attachment reactions, the rates of these reactions decrease owing to the increase in the gas temperature, which leads to the increased conductivity of streamer discharge channels at high gas temperatures.