The Study Of Pulsed Dielectric Barrier Discharge In Nitrogen At Atmospheric Pressure

Compared with the conventional sinusoidal discharge, the pulsed dielectric-barrier discharge (DBD) at atmospheric pressure not only possesses higher efficiency of energy transfer, lower gas temperature, larger discharge current density and higher active particle concentrations, but also it can effectively control the glow-to-arc transition, resulting in a stable plasma. Due to these significant advantages, the pulsed discharge has attracted considerable attention in recent years. But so far, the majority of studies of the pulsed dielectric-barrier discharge at atmospheric pressure are limited to the discharges in inert gases and their mixtures. Little is known concerning the characteristics of pulse-excited atmospheric DBD in molecular gases. In fact, from an application standpoint, molecular gases which are much less expensive and more efficient in promoting plasma reactivity are sometimes more desirable. In this paper, we study the characteristics of pulsed dielectric barrier discharge in atmospheric nitrogen using a one-dimensional self-consistent fluid model. The studies finished include (1) the electric characteristics of the discharge, the spatial structures of the discharge, and the effect of the parameters on the discharge behaviors;(2) the discharge modes of pulsed DBD in N2, the transition conditions between Townsend and glow modes, and the multi-peak discharge mode.The simulation results show that, similar to the typical pulsed DBD at atmospheric pressure, in the pulsed discharge in N2, two discharges are ignited for every voltage pulse:one is at the rising edge or at the top of the voltage pulse and a second discharge at the falling edge. Different from the sinusoidal DBD in nitrogen, the pulsed nitrogen discharge operates the glow mode over a wide parameter range. In glow mode, the density of N2-is some orders of magnitude higher than that of N4+, implying the direct ionization of N2by electron impact is the primary ionization mechanism. Under certain conditions, the discharge can transfer from glow mode to Townsend mode. In Townsend mode, the density of N2+is much lower than N4+density, indicating that the penning ionizations between two metastable molecules play a dominate role. The discharge mode depends on the voltage change rate (dV/dt) at the rising front or the falling front. As the voltage change rate is large, the discharge operates in glow mode, otherwise, in Townsend mode.The discharge behaviors change with the variation of discharge parameters. The increase of the pulse width will cause the growth of the current density of the second discharge at the falling edge. Changing the pulse repetition rates, the current amplitude of both the first discharge and the second discharge will change. Under appropriate parameters, the multi-peak discharge will occur at the rising edge or at the falling edge of the applied voltage pulse. In the multi-peak discharge, the discharge at the rising edge and the discharge at the falling edge can operate in different modes. The discharge mode at the rising edge only depends on the voltage change rate at the rising edge, and the discharge mode at the falling edge only depends on the voltage change rate at the falling edge.