Energy deposition characteristics of the plasma channel in a liquid-phase discharge

The deposition energy of the plasma channel in a liquid-phase discharge has significant influences on the rock-breaking effects. In this study, a deposition energy of the plasma channel test platform was constructed, comprising a charge module, a discharge module, and a measurement module. The time-history curves of the discharge voltage and current were recorded under the combination of different charge voltages and electrode spacings. Consequently, the effects of charge voltage and electrode spacing on both the breakdown voltage and the deposition energy of the plasma channel were analyzed. The results indicate that the voltage drop during the pre-breakdown phase has a significant influence on the deposition energy of the discharge plasma channel. The breakdown voltage demonstrates a nearly linear decrease as the electrode spacing increases, while it exhibits a nearly linear increase with rising charge voltage. The deposition energy shows a two-stage trend characterized by an initial increase followed by a subsequent decrease as the electrode spacing increases. This suggests that there is an optimal electrode spacing that maximizes the deposition energy. For charge voltages ranging from 6 to 9 kV, the optimal electrode spacings were found to be 15 mm, 20 mm, 25 mm, and 30 mm, respectively. These electrode spacings corresponding to energy conversion efficiencies (i.e., the maximum energy conversion efficiencies) of 49.6 %, 61.7 %, 65.9 %, and 75.1 %. Additionally, the critical electrode spacings are 30 mm, 40 mm, 55 mm, and 75 mm respectively, corresponding to energy conversion efficiencies (i.e., the minimum energy conversion efficiencies) of 35.6 %, 33.0 %, 47.1 %, and 35.5 %. In addition, the deposition energy increases as the charge voltage rises. Furthermore, while the deposition energy decreases rapidly after reaching its peak, it increases at a slower rate prior to peaking. This information aids in determining to determine the range of the optimum electrode spacing. Based on the above analyses, a formula for calculating the breakdown voltage has been proposed, along with a theoretical revised model for deposition energy in liquid-phase discharge has also been proposed. The findings provide an experimental foundation for the enhancement of the deposition energy for breaking rock in liquid-phase discharge.