Influence of gas heating and product molecules on discharge characteristics in dry-air-fed ozonizer

Abstract

Influences of gas heating and product molecules on discharge characteristics in dry-air-fed ozonizer was investigated. Especially, the dependence of gas temperature in streamer channel on occurrence frequency of streamer discharge was investigated in detail. In the experiment, repetitive positive or negative impulse streamer was generated respectively between needle-plane electrodes in synthetic air at atmospheric pressure. The repetition rate of the applied pulse voltage was controlled from 0.1 to 7.0 kilo-pulse/sec (kpps). The temperature of streamer channel was estimated from the emission spectrum of N 2 2nd positive system band (0-0). As a result, the gas temperature increased with increasing the pulse repetition rate in both polarities. In the case of positive polarity, the gas temperature increased from 341 to 383 K in response to the increase of repetition rate (0.1 to 6.0 kpps). Eventually, sparkover occurred at 7.0 kpps due to the increase of reduced electric field (E/N) caused by gas heating. The product ozone concentration was saturated with increasing the pulse repetition.

Gas Heating and Formation of Single Linear Discharge Channel on Repetitive Branched Streamer Corona

“…Therefore we selected these experimental conditions for the investigation reported here. It should be also noted that we confirmed that the transition to SFD with an increase of dischargerepetition rate occurs under different voltage conditions (dc, ac, impulse voltage with higher V p and lower f ), different gas conditions (synthetic air and room air, and so on), and different electrode configuration (gap distance, wireplane, and so on) [8][9][10][11]. The light emission from the impulse streamer discharge was observed using an ICCD camera (I) (Andor, iStar) and an image converter camera (TRW, MODEL 1D).…”

“…Discharge sources having a higher discharge repetition rate are now needed in many practical situations in order to increase the treatment throughput. In a previous investigation [8][9][10][11], we found a certain prebreakdown phenomenon which occurs just before positive dc sparkover in the case of a short nonuniform gap in air at atmospheric pressure, namely, a transition of a branched positive streamer to a single filamentary discharge (SFD) with increasing discharge-repetition rate. However, a decrease in treatment efficiency with increasing discharge repetition rates has been extensively reported in the literature [4][5][6][7].…”

“…Therefore, the development of higher frequency pulse power sources has been proceeding [1][2][3]. As a supplementary note, this phenomenon appeared prominently when dilute CO 2 was added to atmospheric air [8][9][10][11]. It has also been reported that sparkover inside a discharge reactor sometimes causes enormous damage to the system, resulting in mechanical failure and system downtime while the damaged component is located and replaced.…”

“…Understanding of the sparkover mechanism at atmospheric pressure remains an open research problem. In a previous investigation [8][9][10][11], we found a certain prebreakdown phenomenon which occurs just before positive dc sparkover in the case of a short nonuniform gap in air at atmospheric pressure, namely, a transition of a branched positive streamer to a single filamentary discharge (SFD) with increasing discharge-repetition rate. As a supplementary note, this phenomenon appeared prominently when dilute CO 2 was added to atmospheric air [8][9][10][11].…”

“…The gap distance and V p in this experimental condition were better suited for the observation of the SFD because the transition to the SFD progresses gradually with increasing f . Based on previous experiments [8][9][10][11], we considered that the conditions used this investigation make it easier to observe and understand the formation process of nonbranched streamers owing to the gradual change with the increase of the impulse repetition rate. Therefore we selected these experimental conditions for the investigation reported here.…”