Experimental study on the influence of energy conversion in the process of load coal plasma breakdown

摘要

The variation of voltage and current waveforms of loaded coal plasma breakdown was investigated thorough an independently designed triaxial loading plasma breakdown system. Furthermore, the effect of breakdown times on the energy conversion and the propagation characteristics of cracks near electrode were discussed. The results show that the loaded coal will form an internal penetrative crack under plasma breakdowns, and with breakdown times increase, the micro cracks of coal surface and the size of the smash area near the positive electrode gradually expands. The voltage and current waveforms of loaded coal differ significantly from those of unloaded coal. With the increase of breakdown times, the pre-breakdown period decreases, the plasma period increases step by step, and the number of voltage and current oscillations increases. During each discharge of the loaded coal, change trends of the deposited energy are consistent, and the deposited energy keeps small level in the pre-breakdown period, then increases rapidly in the plasma breakdown period, and finally keeps stable. In addition, with the increasing number of breakdowns, the maximum deposited energy firstly decreases and then rises, and eventually reaches a plateau. The energy conversion efficiency shows the same tendency with the deposited energy. (C) 2020 Elsevier Ltd. All rights reserved.