Characteristics of N2/O2 reaction in spark gap switch: The effect of high-current pulsed arc

Compressed air is used in spark gap switches as an insulating gas. Triggered by nanosecond pulsed voltage, the streamer bridges the electrode gap in the switch. During the streamer-arc transition, the spatial distribution of the arc changes drastically. The nitrogen and oxygen in the compressed air will react with each other under high temperatures. Damaging effects in the switch are caused by arc reaction. In this paper, by adjusting the parameters of the high-energy pulse discharge circuit, the arc is produced with different current waveform in the spark gap switch, while the gaseous product is analyzed. The results show that, when current pulse-width remains constant, the amount of transferred charge is approximately linear with the production of nitrogen oxides. The proportion of NO is higher when the current pulse-width is shorter. The concentration of nitrogen oxides is determined by the chemical reaction, which relies on the dynamic change of the impulse arc. During the arcing time, there is the collision dissociation reaction in the local thermodynamic equilibrium (LTE) plasma, leading to the production of gas atoms and excitation molecules. In the boundary of the arc channel, the nitrogen oxides formation reactions mainly occur in the arc quenching period. According to the characteristics of the high-current arc, a simplified analysis of chemical kinetics on the reactions of nitrogen and oxygen is implemented to expound the effect of pulsed arc on the gas composition.