Evolution of underwater shock wave in far-field regime of electrical wire explosion system over wide range of electric pulse energy

Abstract

The parametric relationships between underwater shock waves (SWs) in far-field regime and electrically exploded wire under different charging voltages of a generator are investigated. Contributions of the vaporization and current restrike to the resulting SWs have been examined by means of electro-physical diagnostics, free-field pressure probe, and high-speed photography. In the experiment, a 6-μF pulse capacitor is adopted to provide a microsecond timescale pulsed current, exploding a 90/185-μm-diameter, 2-cm-long copper wire with the charging voltage ranging from 7.1 kV (stored energy ∼ 150 J) to 18.3 kV (∼1000 J). Experimental results indicate that as the increase of the charging voltage, the relationship between electro-physical and shock wave parameters shows a rather complex situation. When the charging voltage ranging from 7.1 kV (∼150 J) to 11.6 kV (∼400 J), the peak pressure of SWs (300 mm away from the explosion source) increases almost linearly from 1.16 ± 0.03 to 2.24 ± 0.05 MPa (90-μm wire), and 1.67 ± 0.17 to 2.87 ± 0.12 MPa (185-μm wire). Nevertheless, at a higher charging voltage between 11.6 kV (400 J) to 14.1 kV (600 J), the peak pressure stabilizes in a strange “plateau”. Until the residual energy after the explosion is sufficiently large (>600 J in this study) to induce a strong current restrike, the development of the plasma channel could further enhance the expansion of explosion products, as well as the intensity of measured SWs. In addition, high-speed photography has been applied for those explosions, providing the information of plasma channel expansion and initial SWs propagation.