Phenomenological Studies for Optimizing Subsonic Underwater Discharges

Abstract

Powerful subsonic underwater discharges are used as a tool in various industrial applications. The paper aim is to find the essential design parameters required from a pulsed power system for efficiently drive such discharges. Using different capacitor banks and electrode geometries, a large number of studies were conducted in an effort to better understand the phenomenology of the discharge. Without developing a numerical model for the underwater plasma discharge, the phenomenological studies clearly demonstrated that the maximum pressure that can be generated depends on the discharge current, on the distance between the electrodes and on the characteristic time of the discharge. The results of this work will allow the design of efficient pulsed power-driven strong pressure impulse systems.

Extraction of Mycosporine-like Amino Acids and Proteins from the Agarophyte Gelidium corneum Using Pulsed Power Techniques

“…During HVED pretreatment, average peak current I max was 12.29 ± 1.40 kA, with t char circa 3.9 µs (see sample oscillogram in Figure 1 ). The experimental arrangement was very similar to that presented by Bacqueyrisses et al in [ 39 ]; the constant values (k and 0.68 in Equation (3)) previously determined with hydrophone in [ 39 ] can be taken for the calculation of the peak pressure wave. Given the experimental setup, the amplitude of the peak pressure wave generated during an average discharge was calculated to be circa 13.61 Mpa at a distance of 45 mm (corresponding to the radius of the treatment cylinder).…”

“…As described above for the PEF treatment and at the same intervals, 0.5 mL samples were taken during HVED treatment to track molecular diffusion from the seaweed to the solution during both the application of pulses and during the maceration that followed. The amplitude of the pressure waves generated during HVED was calculated according to the Equation (3) proposed by Bacqueyrisses et al [ 39 ]. where p peak is the peak pressure (Mpa, bar), k is a constant dependent on the characteristics of the fluid (here it will take the value 28 as determined experimentally [ 39 ]), I max is the peak current (A), r the distance from the discharge (m), d the inter-electrode gap spacing (m), and t char the time (s) between the discharge and peak current with the factor 0.68 determined experimentally.…”

“…The amplitude of the pressure waves generated during HVED was calculated according to the Equation (3) proposed by Bacqueyrisses et al [ 39 ]. where p peak is the peak pressure (Mpa, bar), k is a constant dependent on the characteristics of the fluid (here it will take the value 28 as determined experimentally [ 39 ]), I max is the peak current (A), r the distance from the discharge (m), d the inter-electrode gap spacing (m), and t char the time (s) between the discharge and peak current with the factor 0.68 determined experimentally. After HVED pretreatment, the algal suspensions were transferred to beakers to macerate at room temperature for a further 2 h under magnetic agitation (400 RPM).…”

Experimental studies and simple numerical modeling of underwater electric discharges

“…As also recently demonstrated experimentally, however, subsonic underwater discharges cannot generate highly reproducible pressure impulses. 14 Efforts to improve the reproducibility by shaping the electrodes to generate and control the inter-electrode electric field distribution were not successful. 14 In such conditions, one way to obtain reproducible phenomena is by using a very thin exploding wire as a trigger for the discharge, here termed "pilot," mounted between the two underwater electrodes.…”

A Study of a 5.2-kV/100-mm Thyristor Triggered in Impact-Ionization Mode Toward Fast High-Current Applications

“…Subnanosecond impact-ionization switching and reaching high current pulses can be employed in several research domains such as: inertial fusion [9], X-pinch [10], [11] and highenergy-density physics [12]. Moreover, a number of industrial applications such as magnetic pulse forming and welding, rock fracturing [13] and mining require high current pulses in the range of hundreds of kA [14].…”