Velocity of initial propagation of positive nanosecond discharge in liquid water: dependence on high voltage amplitude and water conductivity

Abstract

This study deals with the effect of water conductivity and high voltage pulse amplitude on the initial velocity of nanosecond discharge in liquid water. As variable parameters, we used water solutions with three different conductivities (2 μS cm−1, 100 μS cm−1, 500 μS cm−1), and positive high voltage pulses with four different amplitudes (80 kV, 91 kV, 100 kV, 113 kV). The discharge reactor consists of metallic electrodes in a point–to–plane geometry, both immersed in liquid water. The discharge was generated by a commercial nanosecond pulse power generator with positive HV pulses of ∼6 ns pulse duration (FWHM) and ∼2.5 ns rise time. ICCD time-resolved imaging microscopy with high temporal resolution (∼ns) was utilized as a suitable diagnostic tool for the discharge dynamic propagation. It can be concluded that the discharge visual characteristics and behaviour are not significantly influenced by water conductivity and the length of the filaments increases with the increasing voltage amplitude and reaches the maximum value of ∼1.8 mm for 90 kV. The initial propagation velocity also depends on the voltage amplitude and increases with the voltage. The effect of water conductivity on the propagation velocity is negligible. As far as we know, this paper is the first to bring insight into the topic of the effect of water conductivity on the nanosecond discharge propagation in liquid water.