Partial discharge characteristics of bubble flow under AC non-uniform electric field in FC-72

In the present study, a test chamber filled with perfluorohexane (FC-72) is set up to investigate partial discharge (PD) in phase-cooling bubbles. Under the non-uniform electric field with needle point-to-hemisphere electrodes, thermal bubbles are generated from the needle point. The difference between PD with and without the bubbles is analyzed to identify features of the discharge in the bubbles. It is observed that the bubbles reduce the PD inception and intensify the discharge. A model of bubble motion is established to investigate bubble behavior in an electric field. Based on the observation of the flow and streamer patterns, a mechanism of PD in bubble flow is established and confirmed by phase-distribution of PDs with bubble transit time.