Net Emission Coefficient and Radiation Transfer Characteristics of Thermal Plasma Generated in Nitrogen-PTFE Vapor Mixture

Abstract

The radiation characteristics of thermal plasma columns filled with N2-polytetrafluoroethylene vapor mixture has been studied for the first time. The net emission coefficient is first calculated for typical mixture concentrations. The discrete ordinate method (DOM), which has proven to be an approximate method of reasonable accuracy for radiation transfer in thermal plasmas, is then used to characterize the emission and absorption behavior of cylindrical plasma columns with typical temperature distributions. Results show that the radiative power loss per unit volume at the column center is not always proportional to the local gas pressure. The DOM12-9 configuration, i.e., considering 24 directions in the $r$ -plane of the calculation point and 18 directions crossing the $r$ -plane, produces remarkably accurate results. It is likely to recover the accurate emission and absorption profile by scaling the output from the DOM5-3 configuration with a scaling factor between 0.7 and 0.8. Furthermore, the DOM5-3 configuration accurately locates the absorption layer at the edge of the plasma column. Maximum absorption takes place at a radial location whose distance to the inner radius of the absorption layer is 30% of the layer thickness despite of the very different radial temperature profiles. Under the conditions studied 35%–60% of the radiation from the central part of the column is absorbed in the surrounding cooler gas.