Bubble dynamics and insulation characteristics of C6F12O in the nonuniform electric field

The nonuniform electric field regulates bubble motion through interfacial polarization, Maxwell stress, and electrohydrodynamic effects, while bubble migration redistributes the local electric field and alters dielectric breakdown characteristics. To clarify the relationship between these phenomena in two-phase C6F12O, bubble dynamics under nonuniform electric fields were experimentally investigated, and multiphysics simulations coupling the electric, thermal, flow, and phase fields were performed to analyze bubble deflection at different field strengths. Dielectric breakdown experiments further examined the effects of heat flux, electrode gap, and electric-field uniformity on the breakdown characteristics of the two-phase medium. The results show that, as the electric field strength increases, bubbles migrate toward lower-field regions, with the deflection ratio increasing from about 8% to over 30%, together with an increase in bubble velocity. At four normalized field levels, experimental and simulated deflection ratios exhibited a Pearson correlation coefficient of 0.988 and a mean absolute difference of 2.13 percentage points, indicating good agreement. The breakdown voltage initially decreased and then approached a stable range with increasing heat flux, becoming less sensitive at higher heat fluxes. A similar trend was observed with variations in electrode gap, suggesting that bubbles within or near the critical high-field region degrade dielectric performance. Electric-field nonuniformity significantly affects liquid-phase breakdown voltage, whereas under two-phase conditions, increasing bubble presence in the electrode gap reduced the relative influence of the initial field distribution. These findings clarify the mechanisms of bubble transport and dielectric breakdown and provide guidance for optimizing C6F12O-based phase-change-cooled power equipment.