Study On The Secondary Discharge Modes Of Pulsed Dielectric Barrier Discharge And The NO Removal From N₂/NO Mixture

In recent years, pulsed dielectric-barrier discharges (DBDs) at atmospheric pressure have attracted considerable attention because of their big discharge current and high plasma-chemical and electrical efficiency. Pulsed DBDs take full advantage of the charges accumulated on the dielectric surface and thus two discharges are generated per single voltage pulse. The first discharge is ignited by the applied voltage and occurs at the rising edge or during the pulse top. The secondary discharge is induced by the charges accumulated on the dielectric surface during the first discharge, and it appears at the falling flank of the applied voltage pulse and has opposite polarity. Though pulsed DBDs have been widely investigated, most of these studies are focused on the effect of discharge parameters on the behaviors of the two discharges ignoring the discharge modes. In this paper, we study in detailed the secondary discharge modes of pulsed DBD by using a one-dimensional fluid model. Simulation results show that different from the first discharge occurring at the rising edge, the secondary discharge depends sensitively on the discharge parameters when the pulse width is small. Under our simulation conditions, two different modes are observed:glow mode and sub-normal glow mode. The secondary discharge mode of a pulsed DBD is mainly determined by the electron density distribution right before the secondary discharge is ignited. If the spatial distribution of electron density is uniform before the secondary discharge starts, this secondary discharge will operates at glow discharge mode. However, when under certain parameters the charged particles resulting from the first discharge do not loss completely and lead to a high electron density region in the vicinity of the instantaneous cathode, the spatial structure of the secondary will be changed and operates at sub-normal glow mode. The smaller the pulse width, the wider the gas gap, the shorter the rise and fall times of applied voltage pulse or the bigger the electrical permittivity, the more likely the secondary discharge operates at sub-normal glow mode.Removing NOX with non-thermal plasma generated by the dielectric-barrier discharges has become one of the most promising denitration technologies due to its excellent characteristics of low operation expenses, high removal efficiency, etc. Though many studies on removal NO from N2/NO mixture by a dielectric-barrier discharge have been carried out in the past years, in most studies the dielectric-barrier discharges are driven a sinusoidal voltage. Little work is done on NO removal by a pulsed DBD, especially the theoretical simulation work. In this paper, based on one-dimension fluid mode, we study the removal of NO from N2/NO mixture by pulsed dielectric-barrier discharge at atmospheric pressure. The NO removal mechanism and the dependences of NO removal rate on the discharge parameters are investigated and discussed. Simulation results show that NO is removed mainly through the reaction N+NOâ†'N2+O and thus N atom is main active species that remove the NO from N2/NO mixture. The density of N atom produced by pulsed DBD in N2/NO is determined by the discharge parameters. The bigger the voltage amplitude, the shorter the rising and falling time, the thinner the dielectric layer, or the smaller the discharge gap, the higher the nitric oxide removal rate. When keeping other parameters unchanged, there is an optimal voltage pulse width which results in the maximum NO removal rate.