Addressing the efficiency of the energy transfer to the water flow by underwater electrical wire explosion

Abstract

Experimental and hydrodynamic simulation results of submicrosecond time scale underwater electrical explosions of planar Cu and Al wire arrays are presented. A pulsed low-inductance generator having a current amplitude of up to 380 kA was used. The maximum current rise rate and maximum power achieved during wire array explosions were dI/dt≤830 A/ns and ∼10 GW, respectively. Interaction of the water flow generated during wire array explosion with the target was used to estimate the efficiency of the transfer of the energy initially stored in the generator energy to the water flow. It was shown that efficiency is in the range of 18%–24%. In addition, it was revealed that electrical explosion of the Al wire array allows almost double the energy to be transferred to the water flow due to efficient combustion of the Al wires. The latter allows one to expect a significant increase in the pressure at the front of converging strong shock waves in the case of cylindrical Al wire array underwater explosion.

Aluminum micro-particles combustion ignited by underwater electrical wire explosion

“…Thus, the time delays between the current interruptions in the wires were used to obtain the target TOF. This method showed similar results for the increase in the kinetic energy of the target [16]. The latter can be explained only by an increase in the energy delivered to the water flow due to the aluminum combustion process.…”

“…First, let us calculate the distance that the rod propagates during its acceleration, considering that the exploding wire energy is transferred to the mechanical energy of water at a ∼20 % efficiency rate [20,21]. When ∼3 kJ of the energy is deposited into the copper wire, one obtains E W = 600 J of mechanical energy transferred in the water volume V tot = 2 × 10 −6 m 3 inside the dielectric tube.…”

“…This target was accelerated by the water flow generated by the underwater electrical explosion of either a copper or aluminum planar array. These experiments were carried out using a high-current generator (stored energy of ∼4 kJ at 28 kV charging voltage) producing a current pulse with an amplitude of ∼350 kA and rise time of ∼1,000 ns at short-circuit load [16]. A 40 mm-long wire array was made of 40 wires of either copper (100 µm in diameter) or aluminum (127 µm in diameter).…”

Spectroscopy of a plasma formed in the vicinity of implosion of the shock wave generated by underwater electrical explosion of spherical wire array

“…16 This allows this approach for generating converging strong SW by underwater electrical explosion of either cylindrical of spherical wire arrays to be applied in order to obtain an extreme state of water in the vicinity of the SW implosion. 17,18 In the case of a cylindrical wire array explosion, shadow imaging of the generated SW and water light emission in the vicinity of the convergence axis were used to calculate the time-of-flight (TOF) of the SW. 19,20 These data and the $12% efficiency of the stored energy transfer to the converging water flow were used as validation parameters for comparison with the results of one dimension hydrodynamic (HD) simulations, coupled with the experimentally measured energy deposited into the wires and the EOS for water.…”

Diagnostics of a converging strong shock wave generated by underwater explosion of spherical wire array

“…The parameters of the water (pressure, temperature, and density) in the vicinity of either the convergence axis, in the case of a cylindrical SW, or the origin of the convergence, in the case of a spherical SW, were calculated using one-dimensional hydrodynamic (1D-HD) simulations coupled with the experimentally measured energy deposited into the wires and the equation of states for water. 13 The results of these simulations were considered acceptable in terms of the fitting between the simulated energy, which is transferred to the water flow and should be smaller than 12% of the experimentally measured energy deposited into the exploding wires, 14,15 and the experimentally measured and simulated time-of-flight (TOF) of the converging SW. In addition, these simulations assume longitudinal and azimuthal uniformity of the converging SW, which in the case of a 5 mm in radius cylindrical wire array explosion was obtained experimentally down to a radius of convergence r % 100 lm, resulting in a convergence ratio of at least 50.…”