Polarity-dependent discharge evolution in bubbled water under repetitive pulsed fields: From bubble-mediated initiation to polarity-controlled breakdown

Liquid discharge under pulse voltage has been applied in many fields, but mechanisms governing repetitive-pulse breakdown in bubble-containing media remain incompletely understood. This study investigates bubble-mediated discharge evolution in de-ionized water using a needle-plate electrode system under repetitive pulsed voltages. Bubbles were artificially introduced to examine the discharge behavior in their presence. High-speed camera imaging and electrical measurement were used to capture the discharge dynamics. The results showed that the presence of bubbles reduced the overall insulation strength of water and affected the process of breakdown. The discharge process varied under different pulse polarities. Negative polarity pulses often led to bubble cluster discharges, while positive polarity pulses led to bush-like and tree-like discharge formations. Furthermore, the development of streamer channels and arcs was observed, especially under positive pulses, indicating complex interactions between bubbles and the discharge path. This study highlights the influence of pulse energy and voltage on discharge morphology, providing insights for future applications of liquid-phase discharge.