Net Emission Coefficients of Radiation in Air and SF6 Thermal Plasmas

Abstract

Net emission coefficients of radiation were calculated for isothermal plasmas of air and SF 6 as a function of the plasma temperature 5,000-30,000 K and the arc radius (0.01-10 cm) at various plasma pressures. Calculations take into account continuum and line radiations, special attention has also been taken to influence of molecular species in case of the air plasmas. It has been found that the molecular bands of O 2 , N 2 , N 2 ? , NO and NO ? have very strong effect on the net emission coefficients at low temperatures (below 10,000 K). In case of SF 6 , effect of PTFE admixture on the net emission coefficients was also studied. It follows from the calculations that the net emission coefficients vary very little with various admixtures of PTFE. Values of net emission coefficients if SF 6 plasma calculated for various spectral regions were compared.

Differing current and optical return stroke speeds in lightning

“…This pseudo‐pressure is valid because thermodynamic and transport properties are fundamentally only functions of T e and n h . For P opt , p s is taken as the pressure to make use of the results presented in Aubrecht and Bartlova [].…”

Radiative emission from air thermal plasmas with vapour of Cu or W

“…These coefficients largely determine axial plasma temperatures above 8 000 K. To account for a balance between emission and absorption at lower temperatures with steep gradients, the method of net emission coefficients is not valid. Furthermore, molecules at lower temperatures are not fully dissociated and play an important role which increases with the plasma pressure [9,10]. Even though the use of the net emission coefficients cannot precisely account for an absorption in the outer part of the arc with steep temperature gradient, it is widely used in complex computations of a plasma flow.…”

P1-approximation for radiative transfer: application to SF6 + Cu arc plasmas

“…Semi-empirical formulas given in [8,9] were used. The line shapes were calculated by convolution of Gaussian and Lorentzian profiles, resulting in a Voigt profile.…”