Generation and Diagnostics of Ambient Air Glow Discharge in Centimeter-Order Gaps

Abstract

Re-pulsing glow discharges in gaps up to 2 cm were experimentally investigated in atmospheric pressure air. Discharge was ignited as a sequence of spark and glow discharge and sustained in a glow regime after ignition. It was confirmed that the discharge with defined parameters could be ignited without any adjustments after initiation of the discharge. The discharges were characterized by a high-speed camera, current and voltage measurements, and optical emission spectrometry (OES). Typical structure of the glow discharge consisting of cathode glow, dark faraday space, positive column, and anode glow was observed. Transition from subnormal to normal glow mode was confirmed by analysis of current and voltage waveforms. It was found by OES that the type of discharge strongly affects the ratio of produced reactive species. It was confirmed that with change of discharge from subnormal to normal glow regime, rotational temperature could vary across a wide range (from 1650 to 3500 K). The developed device allows glow discharge to be ignited with defined parameters, which makes the control of the gas temperature and ratio of reactive species possible by presetting the discharge parameters. Additionally, it was demonstrated that corona discharge or repeating spark discharges could also be generated using the developed device without additional manipulations of the experimental setup by adjusting the discharge parameters.INDEX TERMS Glow discharge, gliding arc, OES, air plasma.

Control and Stabilization of Centimeter Scale Glow Discharge in Ambient Air Using Pulse-Width Modulation

“…The perfect solution is the initiation of the discharge in larger gaps at desired parameters, avoiding discharge elongation. A recent work reported glow discharge generation at defined conditions in centimeter-order gaps (up to 2 cm) using a single power supply that did not require any adjustments after the start of the discharge [24]. In the present work, we improved the performance of the previously reported power supply and confirmed the stable operation of plasma with defined parameters in the presence of external airflow without elongation, which looks promising for gas-conversion applications.…”

“…Re-pulsing glow discharge was generated using a modified version of a generator reported in detail elsewhere [24]. The discharge was ignited between two copper rod electrodes (99.5% Cu, CU-112544, Nilaco, Japan) by supplying high voltage to the upper electrode (anode) when the lower electrode (cathode) was electrically grounded.…”

“…The term "gliding arc" was initially suggested based on the visual appearance of the discharge; however, a more detailed study revealed that this type of discharge burns in a glow regime. Therefore, in the present work, we use the more physically correct term "gliding glow" discharge instead of the frequently used "gliding arc" [22]- [24].…”

“…Additionally, air looks promising as a raw material for plasma-based nitric oxide synthesis owing to its low cost; therefore, a scalable atmospheric-pressure ambient-air plasma source is required for sustainable "green" nitrogen fixation. There are many works on the generation and diagnostics of glow discharges in various gases at atmospheric pressure using subcentimeter gaps between electrodes, but works are limited on the generation and diagnostics of glow discharges in centimeter-order gaps filled with atmospheric-pressure molecular gases, including air [24], [29]- [34].…”

“…Additionally, the presence of plasma with undesired parameters could result in the production of unwanted reactive species, which could limit the application. For example, the production of OH radicals in ambient air glow discharge dramatically increases when the discharge mode is changed from subnormal to normal glow regime [24], and in the case of gliding glow discharge, the production of OH radicals will vary depending on the plasma elongation. Another drawback is the constantly changing plasma impedance that results in problems with load matching and large values of reflected power.…”