Chemical species and nonequilibrium temperatures for airflows in a plasma wind tunnel

The flowfield generated by the plasma wind tunnel SCIROCCO is investigated by using optical emission spectroscopy, a diagnostic nonintrusive technique that is able to identify and analyze the chemical species in the flow. The physicochemical flow conditions are characterized by nonequilibrium effects that can result in large differences between rotational translational, vibrational, and electronic temperatures. Thus, to study the freestream emission, the radiation emitted from a well-defined core volume on the plasma centerline during a test is collected by an optical system and analyzed by a spectrograph. Emission spectra are obtained over a 200-900 mu wavelength range. The experimental results are compared with the simulated spectra obtained by using the PARADE code to evaluate temperatures and concentrations of the air plasma species. Partial agreement is achieved between experimental and numerical data.