Simulation of Bubble Dynamics in Liquid under Impulse Voltage

Bubbles in liquid insulation systems have always troubled engineers and equipment managers, such as bubbles in power transformers. Since bubbles are very easy to induce discharge and even insulation breakdown, they pose a great threat to the safety of power equipment. The dynamic behavior of a bubble under the electric field has a significant impact on its discharge characteristics, but compared to a steady electric field, there are few reports on the bubble behavior under impulse electric field. In this paper, a multi-physics simulation model coupled with electric field, flow field and phase field was established to study the dynamic behavior of bubbles under the action of pulsed electric field. The simulation results showed that under the pulsed electric field, the non-conductive bubble would stretch in the electric field direction. The bubble was ellipsoidal under the lower electric field intensity, and became dumbbell-shaped under the higher electric field intensity. The degree of bubble deformation increased with the applied electric field strength and bubble radius. In addition, there was a hysteresis in the deformation of the bubble under the action of the pulsed electric field, and the analysis showed that this was caused by the characteristic time of the fluid. For conductive bubbles under the action of a pulsed electric field, it was found that even at low field strengths, the bubbles had instability, which may have a profound impact on the discharge characteristics of the liquid.