INFRARED MEASUREMENTS OF THE VIBRATIONAL EXCITATION AND DE-EXCITATION RATES OF N2 USING CO ADDITIVE.
CORNELL AERONAUTICAL LAB INC BUFFALO N Y AERODYNAMIC RESEARCH DEPT
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Shock wave and nozzle expansion flow studies have been made of the vibrational relaxation of N2 in a 95 N2 5 CO test gas mixture by observing the infrared optical activity of the CO. The large cross section for vibration-vibration exchange between N2 and CO permits the vibrational temperature of the N2 to be inferred from band reversal measurements of CO. Behind shock waves with equilibrium temperatures in the range of 1500K - 2100K the vibrational relaxation rates for N2 obtained by this method are shown to be in good agreement with previous measurements of the N2 vibrational relaxation rate. In nozzle expansion flows of the same test gas from reservoir temperatures of 2800K - 4000K and reservoir pressures of about 50 atm, the vibrational temperatures of N2 are found to be much closer to equilibrium values than predicted using the relaxation rates determined behind shock waves. These observations are in complete agreement with results obtained earlier in the N2 by line-reversal spectroscopy. Both N2 and CO have been observed to exhibit faster rates for vibrational de-excitation in nozzle flows than predicted using vibrational rate data obtained in the shock wave excitation environment. Author
- Fluid Mechanics
- Atomic and Molecular Physics and Spectroscopy