Simulation of thermal and chemical relaxation in a post-discharge air corona reactor

Abstract

In a DC point-to-plane corona discharge reactor, the mono filamentary streamers cross the inter electrode gap with a natural repetition frequency of some tens of kHz. The discharge phase (including the primary and the secondary streamers development) lasts only some hundred of nanoseconds while the post-discharge phases occurring between two successive discharge phases last some tens of microseconds. From the point of view of chemical activation, the discharge phases create radical and excited species located inside the very thin discharge filaments while during the post-discharge phases these radical and excited species induce a chemical kinetics that diffuse in a part of the reactor volume. From the point of view of hydrodynamics activation, the discharge phases induce thermal shock waves and the storage of vibrational energy which relaxes into thermal form only during the post-discharge phase. Furthermore, the glow corona discharges that persist during the post-discharge phases induce the so called electrical wind. In the present work, the post-discharge phase is simulated in a bi-dimensional geometry using the commercial FLUENT software. The discharges effects (radical and excited species creation and thermal relaxation) are involved through chemical and energy source terms calculated from a complete 2Drz streamer model already developed.