Pre-breakdown phenomena and discharges in a gas-liquid system

Abstract

In this paper, we investigate pre-breakdown and breakdown phenomena in gas-liquid systems. Cavitation void formation and breakdown in bubbles immersed in liquids are studied numerically, while complete breakdown of bubbled water is studied in experiments. It is shown that taking into account the dependence of water dielectric constant on electric field strength plays the same important role for cavitation void appearance under the action of electrostriction forces as the voltage rise time. It is also shown that the initial stage of breakdown in deformed bubbles immersed in liquid strongly depends on spatial orientation of the bubbles relative to the external electric field. The effect of immersed microbubbles, distributed in bulk water, on breakdown time and voltage is studied experimentally. At the breakdown voltage, the slow 'thermal' mechanism is changed by the fast 'streamer-leader' showing a decrease in breakdown time by two orders of magnitude by introducing microbubbles (0.1% of volumetric gas content) into the water. In addition, the plasma channel is found to pass between nearby microbubbles, exhibiting some 'guidance' effect.

Experimental observations and interpretations of bubble-induced discharges under microsecond pulsed voltages in water

“…experimental conditions [8,9]. Meanwhile, vaporization and ionization development in the gas phase make it more difficult to explore the mechanisms of discharges [10][11][12]. Consequently, more detailed investigations on the ignition and propagation of different discharge modes in water are required to improve our understanding of underwater discharges.…”

Analysis of discharge regimes obtained by microsecond underwater electrical breakdown in regard to energy balance

“…For nanosecond pulses, the two stages are considered to occur simultaneously. The expansion of a bubble following the plasma ignition has been widely analyzed by cavitation theory [31][32][33][34][35]. For microsecond discharges in liquid, the cavitation bubble results from the breakdown phenomena which can be initiated by two different mechanisms: the thermal mechanism and the direct ionization (or streamer) mechanism [9,36].…”

The bubble method of water purification

“…At room temperature T = 293 K, at particle radius r = 10 μm and the concentration of freon molecules in water 1 ppm (N m = 2•10 22 m −3 ), we obtain that this mechanism dominates at E 10 6 V/m. Because such electric field strengths correspond to the breakdown electric strengths in atmospheric air and water [29,30], one can conclude that acceleration of the association process under the action of an external electric field is not a matter of principle.…”