Evolutions of streamer dynamics and discharge instabilities under repetitive pulses in humid air

Abstract

The presence of water molecules in air introduces complexities to residual charge transports and energy relaxations that may provoke streamer discharge instabilities under repetitive pulses. Evolutions of pulse-periodic positive streamer dynamics were investigated in humid air. Pulse-sequence and temporally resolved diagnostics were implemented to capture discharge evolutions. The streamer development and evolutions of charged species in humid air are qualitatively analysed based on a 2D-0D combined simulation. Evolution features of streamer behaviours in humid air include the faster filamentation of the primary streamer, pronounced propagation selectivity to previous secondary streamers, more branches of both primary and secondary streamers, and accelerated secondary streamer into stagnation. The repetitively pulsed breakdown is proceeded by the progressive axial prolongation of secondary streamers with bright heads and faint tails. Nonintuitively, the withstanding capability does not illustrate dramatic differences in dry air and humid air especially at high pulse repetition frequency. High-density residing hydrated ions with high electron bound energies (impeding streamer propagation) and the enhanced thermal release to cause higher reduced electric field (facilitating streamer propagation) may contrarily affect evolutions and discharge instability developments of positive streamer in humid air.

Effects of DC bias on evolutions of repetitively pulsed streamer discharge in humid air

“…The effects of air humidity on the evolution of streamer channels under repetitive pulses in humid air have been investigated in detail in our previous work [27]. The differences between the repetitively pulsed streamer propagations in dry air and humid air are mainly reflected in three aspects.…”

“…Previous studies have shown that the residual electron density in the gap is about 10 5 cm −3 at 2 kHz repetitive pulse [34], which may have a minor effect on the subsequent discharge. The negative ions maintain a high quantity during the pulse interval (the density of O − 2 is approximately 10 9 cm −3 after 500 µs [27]) and have a significant effect on the subsequent discharge. The mobility of negative ions has been investigated in detail in [35].…”

Repetitively pulsed streamer discharge with laser-induced surface trapped electron desorption to exploit residual charges in situ

“…The experiment setup for the repetitively pulsed surface streamer discharge is schematically illustrated in figure 1 with the nanosecond pulsed laser irradiation. Electrical and optical diagnostics have been described in detail in our previous investigations [33,34]. Pulsed voltage and current are measured by a commercially available voltage probe (Northstar, PVM-5) and a wide-band current transducer (Pearson, Model 6585), respectively.…”

“…The dry air is supplemented from the air tank. However, if the humidified air is included in concerned parameters, desorbed electrons would attach to water molecules [34]. Consequently, the effect of the laser irradiation may be weakened.…”

Dynamics of the material ejection in a dipolar arc in continuous regime

“…These devices reveal particularly useful as their acquisition speed keeps increasing with years which gives a lot of new opportunities in plasma studies. The main advantages of this diagnostic tool are its good spatio-temporal resolution that allows the tracking of different plasma fast phenomena such as streamers propagation [14] and the absence of induced perturbations. However, the use of fast imaging for electric arc fault plasma analysis has been relatively limited yet, probably due to the lack of satisfying video tools capable of processing efficiently large datasets.…”