An Experimental Setup for IR Gas Radiative Property Measurements at Temperatures Up to 6000K: Application to CO₂ and CO₂-N₂ Mixtures

An experimental setup is developed to measure gaseous radiative properties at high temperature and is first applied to CO₂ and CO₂-N₂ mixtures. The gas mixture is heated by a microwave discharge at atmospheric pressure. In a first step, a characterization of the plasma is performed through analysis of the emission spectra in the visible and near UV ranges. This characterization is performed very close to the exit of the plasma cavity where possible departure from local equilibrium is most likely to be observed. The gas flow is shown to be stable and close to local thermodynamic equilibrium at temperatures up to 6000K. In a second step, a Fourier transform spectrometer (BOMEM DA8) with a resolution of up to 4.10⁻³ cm⁻¹ is associated with the microwave plasma source to perform emission measurements in the infrared range in order to study the infrared properties of CO₂. These measurements are carried out farther away from the exit where the gas mixture is at lower temperatures with a significant concentration of CO₂. Temperature measurements are derived from Abel inverted CO overtone emission spectra (Δv = 2) and, as preliminary results, CO₂ emission measurements in the 2.7 μm range are compared to calculations.