The aim of this research is to investigate the thermal nonequilibrium state of CO2-N2-Ar plasma flows generated in an arc-heated wind tunnel using spectroscopic analysis. An area intensity method that uses molecular band spectra is applied to accurately evaluate the thermal nonequilibrium state of the plasma flows. The radiation from CO2-N2-Ar arc plasma flows around a disk model is observed using spectroscopic measurements. The flow temperatures are evaluated by applying the area intensity method to the CN Violet bands dominantly observed in the measured spectra. In the freestream, the vibrational temperature is higher than the rotational temperature due to the vibrational nonequilibrium process. In the shock layer, a faster vibrational relaxation process can be observed because the vibrational temperature starts to decrease after reaching its maximum value. However, the vibrational temperature is still higher than the rotational temperature. Therefore, the vibrational nonequilibrium state is present in the shock layer. In conclusion, we clarify the thermal nonequilibrium state of CO2-N2-Ar arc plasma flows along the stagnation streamline around the disk model.

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