Performance recovery of plasma actuators in wet conditions

Abstract

Plasma actuators have been extensively studied for flow control applications. While these studies have been traditionally focused on characterizing their performances as flow control devices, the performance of plasma actuators under adverse conditions like light rain remains to be less explored. This paper seeks to study the effects of water adhesion from droplets directly sprayed on to a plasma actuator using thrust recovery as the performance metric. It was found in all tests that wet actuators quickly recover plasma glow, before gradually regaining performance comparable to the dry actuator. The measured thrust for the wet actuator after 5 seconds of operation recovered by 46% and 42% of the thrust of the dry actuator for 50.0-62.5 g/m2 and 125-150 g/m2 of sprayed water droplets, respectively. At 22.5 kVpp and 14 kHz, the highest thrust recovery was recorded at 84% of that of the dry actuator after 80 seconds of operation. For 17.5 kVpp and 14 kHz the wet thrust recovered by 79%, while for 22.5 kVpp and 10 kHz the wet thrust recovered by 68% of their dry counterpart in 80 seconds. For 17.5 kVpp and 14 kHz, the thrust almost fully recovered in comparison to the dry actuator after about 290 seconds of operation. These results indicate that both applied voltage and operating frequency plays a critical role in the performance recovery while the latter may have a stronger influence. Performance recovery for a wet serpentine shaped plasma actuator is also included for general applicability. The power data in all cases show that wet actuators consume more power which with time gradually approach the dry actuator power data. This because during the initial stages of operation, the rolling mean current of the wet actuator is higher than the dry actuator even though the ionization spikes of dry actuator is stronger.

Surface DBD degradation in humid air, and a hybrid surface-volume DBD for robust plasma operation at high humidity

“…For example, at RH = 75% in figure 8, the maximum number of monolayers is 4, in qualitative agreement with Monte Carlo molecular simulations [43]. This would seem to be much too thin (∼1 nm) to form an electrically-conducting water film; however, even as few as three monolayers (RH > 66%) are, surprisingly, already sufficient to exhibit significant surface electrical conductivity [9,44,45]. The thin film conductivity enhancement factor, relative to bulk water [44], is shown to be as high as 10 5 , and could be due to conduction along a polarized HOHHO − layer, by tunneling via dipole resonances [46].…”

Surface temperature characterization of dielectric barrier discharge plasma actuator in quiescent air

“…One of the main reasons for this is the concern over weather conditions such as rain. In this regard, Lilley et al reported that DBDPA is sufficiently durable even when completely wet, and that its performance gradually recovers with continuous actuation in dry air [10].…”

Distributed Compact Plasma Reactor Sterilization for Planetary Protection in Space Missions

“…Thus, this study shows the potential of the APS as a sterilization technology for applications in planetary protection with advantages of uniform spatial decontamination, low processing temperatures, low exposure times, lightweight with no moving parts, ability to decontaminate porous surfaces and compatibility with relevant materials. Additionally, it is important to note that the DBD reactors has been successfully tested and found to regain performance even when water droplets are present on the work surface [30] making it a better candidate for a broad range of practical sterilization applications. Future research on the APS is needed for detailed material compatibility studies and further evaluation of the system in sterilizing other species of interest to planetary protection.…”