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When shock waves induced by pulsed electrical discharges in dielectric liquids are widely applied in industrial fields, it is necessary to improve the energy transfer efficiency from electrical energy to mechanical energy to improve the shock wave intensity. In order to investigate the effect of the plasma channel length created by the liquid electrical discharge on the shock wave intensity, a test stand of dielectric liquid pulsed electrical discharge is designed and constructed. The main capacitor is 3 μF, and the charging voltage is 0–30 kV. Based on the needle-needle electrode geometry with different gap distances, the intensities of shock waves corresponding to the electrical parameters, the relationship between the plasma channel length and the deposited energy, and the time-resolved observation of the plasma channel development by a high speed camera are presented and compared. The shock wave intensity is closely related to the power and energy dissipated into the plasma channel. The longer plasma channel and the quicker arc expansion can lead to a higher power and energy deposited into the plasma channel, which can activate a stronger shock wave.

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Electrohydraulic shock wave (EHSW) is seemingly one of the simplest and most common products of microsecond pulsed discharge (μsPD) in water; however, its generation process remains far less clear. To study the influence of current waveforms on the generation of an EHSW, we conducted discharge current interception experiments using a bypass branch in the circuit. The current interception time Δt is properly controlled so that the discharge current through the water gap can be terminated at a chosen time. Results show that the peak pressure Pm is first linearly increasing with Δt, and then Pm reaches a stable value. The expansion of the spark channel with increasing velocities will enhance the peak pressure. This phase can be regarded as the accelerated expansion phase (AEP) of the piston theory. The transition area of the Pm–Δt relationship of this experimental setup shows that the AEP lasts for about tm = 5 μs. After the AEP, the deposited energy will help to maintain a higher pressure in the falling edge of the pressure waves. The full width at half maximum of the waveforms finally approaches 12.5 μs in our tests. The experimental results provide evidence of the piston theory in interpreting the generation of EHSW induced by μsPD.

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