An Experimental Study on the Characteristics of Gliding Arc Discharge in CO₂ Dissociation with an Inlet Laval Nozzle

The Gliding Arc Discharge (GAD), a kind of non-equilibrium plasma, has gathered substantial interest in the domain of CO₂ decomposition due to its high energy efficiency. Current research has demonstrated that the flow rate significantly impacts the CO₂ dissociating, but the discharge characteristic is not well understood. In this paper, experiments were carried out to compare the GAD characteristics in CO₂ dissociating between the traditional reactor and the reactor featuring an inlet Laval nozzle, in which current and voltage waveforms, high-speed optical images, and Schlieren images were recorded simultaneously. The experimental results show that in the reactor with an inlet Laval nozzle, the re-ignition voltage, discharge period, and power decreased by 75%, 39%, and 87%, respectively, and a higher probability of back-breakdown occurring at the same flow rate (4 L/min), compared to the typical GAD reactor. In addition, although the luminosity of the GAD plasma diminished, the intensified turbulence caused by the high flow rate inside the reactor through the Laval nozzle expanded the diffusion region of the hot gas. These findings highlight the multi-perspective discharge characteristics of high-flow-rate GAD, thereby enhancing comprehension of the diverse mechanisms through which high flow rate affects CO₂ conversion.