Influence of fine bubbles on generation efficiency of pulsed discharge underwater

Abstract The influence of fine bubbles introduced into water on the dielectric breakdown characteristics of discharge probability, discharge delay time, and arc probability was investigated. Fine bubbles were generated by the pressurized dissolution method. A needle-to-plate electrode was placed in the water where fine bubbles were introduced, and a pulsed voltage generated by a Blumlein line-type pulsed-forming network was applied to generate underwater plasma. The discharge onset voltage, discharge delay time, and arcing voltage decreased, and the discharge probability increased by introducing fine bubbles. The decrease in the discharge onset voltage is more significant in the case of argon fine bubbles than that of air fine bubbles. The influence of fine bubbles on the discharge onset voltage and the delay time is more significant than the longer gap length. On the other hand, the longer gap length on arcing voltage is more significant. These results suggest that the bubble at the vicinity of the electrode introduced by fine bubbles enhances the breakdown; however, the fine bubbles in the water between the electrodes do not affect much.