Breakdown in Liquids

High Field Effects and Breakdown in Liquids:

Jun Qian

Our group has been involved in simulation work relating to pulsed electrical breakdown in liquids. The goal is to probe the inherent physics and quantify the dynamics. Typical voltage pulses in the sub-microsecond (100–200 ns) range are of interest. Flux-corrected transport approaches have been utilized for the numerical implementation. Our model results adequately explain experimental observations of pre-breakdown current fluctuations in liquid water, streamer propagation and branching as well as disparities in hold-off voltage and breakdown initiation times between the anode and cathode polarities. It is shown that breakdown is initiated by field emission at the interface of pre-existing micro-bubbles. Impact ionization within the micro-bubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. Also, it has been demonstrated that polarity effects arise from the large mobility difference between electrons and ions.