Thermal analysis of a high-power glow discharge in flowing atmospheric air by combining Rayleigh scattering thermometry and numerical simulation

Abstract

The thermal state of a glow discharge with intermediate current in the flowing atmospheric air is investigated by a combination of the Rayleigh scattering thermometry imaging and the numerical simulation. Results from simulation indicate that during the initial breakdown, the local translational temperature could reach a huge value (e.g. 6000 K) but decreases fast attributed to the strong heat transfer with surrounding cold air. In the gliding stage, the translational temperature of plasma is balanced by the input power density and the heat dissipation rate. As the gas flow rate is increased, the translational temperature in the glow plasma column diminishes. The flow affects the thermal state of plasma from two aspects. First, it promotes the elongation of the plasma column to decrease the input power density. Second, the flow enhances the local heat dissipation. As a result, the translational temperature is lowered due to flow. Using a two-temperature model, which considers the translational temperature, the vibrational temperature and their transitions, the non-thermal state of plasma is further analyzed. The gas flow is found to reduce the translational temperature and the vibrational-translational (V-T) relaxation rate, and thus prevent the thermalization of plasma column.