Streamer polarity dependence of NOx removal by dielectric barrier discharge with a multipoint-to-plane geometry

In this paper, we experimentally investigated an effect of streamer polarit y on the reduction of NOx by using a barrier discharge plasma reactor with a multipoint-to-plane geometry. A high-frequency sine wave voltage generato r and a repetitive pulse generator, which generated narrow and high-voltage pulses were used to remove nitrogen oxide (NOx). By the optical spectrum m easurement, it is clarified that electrons with high energy, more than 10 e V, are produced in the discharge region at atmospheric pressure. The intens ity ratio of the first negative system of N-2(+) (391.4 nm, threshold energ y 18 eV) to the second positive system of N-2 (337.1 nm, threshold energy 1 1 eV) neither depends on the applied voltage nor the frequency, but it depe nds on streamer polarity. Further, it is shown that the value is higher in a positive streamer than in a negative streamer. The use of a multipoint-to -plane electrodes caused the streamer polarity interchange every half cycle of the sine wave of the applied voltage, while in a case of the parallel p lane electrodes, the positive streamer was only generated in the discharge region. The simulated gas and the exhaust gas from a diesel engine generato r were used to confirm the NOx removal performance of the reactor.