Numerical Simulation of Breakdown Process of Nitrogen Spark Switch at Atmospheric Pressure
To study the nanosecond pulsed breakdown process of nitrogen spark switch at atmospheric pressure,the discharge process in the gap is simulated using the particle-in-cell method and the transient physical images of the formation and propagation process of the streamer are obtained.The effect of the pulse voltage rise time on the discharge processes in the gap are comparatively analyzed.The results obtained are as follows.Firstly,the nanosecond pulsed breakdown process of the switch includes the formation and fast propagation of the streamer.Secondly,runaway electrons may be generated in the streamer head and the branches of the streamer channel may be formed due to the photoionization during the fast propagation stage of the streamer.Thirdly,the average propagation velocity of the streamer channel during the streamer fast propagation stage is larger than that during the streamer formation stage.Finally,for the increasing rise time of pulse voltage,the propagation velocity of streamer becomes smaller,the breakdown voltage becomes lower,and the breakdown time delay of the switch becomes longer,which is consistent with the measurement results.
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