Characteristics of an AC rotating gliding arc discharge in NH3 and air atmospheres

Abstract

Plasmas have emerged as a promising technology for the utilization of NH3 as a carbon-free fuel for direct plasmas-assisted combustion and hydrogen production. This study aims to explore the electrical and optical emission characteristics of the rotating gliding arc (RGA) discharge in NH3 and air swirling flows over a wide range of nominal power inputs. The electrical characteristics were measured using voltage–current probes, while a spectrometer was employed to assess the spectral characteristics. Additionally, a synchronized high-speed camera equipped with a dual-scope objective was utilized to capture transient phenomena of the arc in the optical emission spectrum. Both the spark-type and glow-type discharges were observed in RGA. Interestingly, the spark-type discharge frequency exhibited a non-monotonic variation with increasing nominal power inputs for both NH3 and air, while the glow-type discharge frequency displayed a monotonous upward trend. Regarding the spectral emission characteristics in NH3, a dramatic transition of the arc emission spectrum from Hα to NH2* was observed as nominal power inputs increased. The Hα and NH2* emissions that are dominated in the spark-type and glow-type discharges, respectively, and the intensity ratio of Hα and NH2* emission shows evident correlations with discharge current and electric field strength. In summary, this study represents the first investigation into the electrical and spectral characteristics of RGA in NH3.