Pressure Characteristics of Underwater High-Voltage Pulsed Discharge Shock Waves Using Needle-Mesh Electrode

High-Voltage Fragmentation is a novel comminution technology that utilizes shock waves generated in water by nanosecond pulsed voltages with fast rise times (<500 ns) to fracture materials, offering significant advantages in energy efficiency and environmental friendliness. This study established an underwater pulsed discharge experimental platform to meet the fast-rise-time pulse parameter requirements. It analyzed the influence patterns of the needle-mesh electrode gap distance, the needle electrode tip radius of curvature, and water conductivity on shock wave pressure intensity and time-domain characteristics. The research found that the energy conversion efficiency of underwater pulsed discharge is significantly affected by the pre-breakdown process. The peak pressure, impulse, velocity, and rise slope of the shock wave exhibit a trend of initially increasing and then decreasing with increasing needle-mesh electrode gap distance and needle electrode tip radius of curvature. The maximum pressure intensity, maximum equivalent wave velocity, maximum rise slope, and shortest wavefront time occurred at a 20 mm gap distance and a needle electrode tip curvature radius of 0.45 mm. Both pressure intensity and propagation velocity initially increased and then decreased with increasing water conductivity, reaching their maxima at a water conductivity of 340 μS/cm. Water conductivity showed no significant effect on rise slope and wavefront time.