An infrared spectroscopic study of carbon monoxide in a supersonic nozzle

Measurements of infrared emission spectra of carbon monoxide in the first overtone band were performed in the reflected region of a shock tube and in a supersonic nozzle flow. The vibrational population estimated from the spectra at the reflected region whose temperature and pressure were 2700-3100 K and 187-200 kPa, respectively, showed the Boltzmann distribution. The measured spectra in the supersonic nozzle flows with reservoir temperature and pressure of 2300-3300 K and 520-565 kPa were similar to the simulated ones which were obtained using numerical results for translational temperature and vibrational population distribution by solving quasi-one-dimensional gas dynamic equations coupled with nonequilibrium vibrational relaxation equations. The measured vibrational energy almost agrees with the simulated one.