Experimental study and numerical modeling of vibrational oxygen temperature profiles behind a strong shock wave front

Abstract

The evolution of oxygen molecule vibrational temperature behind the front of a shock wave was studied at shock wave velocities 3 4.5 km/s and gas pressure ahead of the shock front 1 5 Torr. The results of vibrational temperature measurement con¦rmed the conception of separation of vibrational relaxation and dissociation zones behind the shock wave front at T ≤ 6500 K. It is observed that at T = 6500 10 500 K the vibrational temperature decreased in comparison with its value characterized by the achievement of vibrational translational equilibrium before the dissociation started. It is shown that the model should to be modi¦ed to describe the evolution of the oxygen vibrational temperature under the conditions of vibrational relaxation and dissociation coupling.

Experimental study of nonequilibrium dissociation of molecular oxygen

“…On the oscillograms, the temporal interval of the kinetic region behind the shock front shortens. Earlier, it was revealed [2] that in the temperature range T 0 = 3500 6500 K, there is agreement between the temperature T 1 calculated under the assumption of vibrational-translational equilibrium before the dissociation onset and the temperature T max v measured at the absorption maximum (Fig. 2).…”

“…The technique of oxygen vibrational temperature measurement behind the shock front is based on the measurement of oxygen absorption from di¨erent vibrational levels and comparison of measured absorption with detailed absorption spectra calculated for vibrational (T v ) and translational (T ) temperatures up to 10,000 K. This technique was described earlier in [2] and was employed using several wavelengths from 200 to 260 nm. The test gas was undiluted high purity oxygen (99.999%, Linde Production) with the initial pressures ranging from 1 to 2 Torr.…”

“…1, the experimental points were obtained using absorption oscillograms corresponding to three di¨erent wavelengths (220, 230 and 260 nm). The uncertainty of temperature determination was not higher than 10% [2]. Figure 1 The pro¦le of vibrational temperature Tv behind the front of shock wave in oxygen at T0 = 8620 K (temperature directly in front).…”

“…Figure 1 The pro¦le of vibrational temperature Tv behind the front of shock wave in oxygen at T0 = 8620 K (temperature directly in front). The symbols are the measured values Tv using absorption oscillograms at wavelengths 220 (1), 230 (2), and 260 nm (3); Teq is the equilibrium temperature REAL GASES AND RAREFIED FLOWS Figure 2 Maximum vibrational temperature T max v behind the shock front vs. T0: 1 ¡ temperature T1 calculated under assumption of vibrational-translational equilibrium before the dissociation onset. Signs refer to experimental data At temperatures T 0 < 6500 K, the maximum vibrational temperature T max v was attained for a time from 0.5 to 1.5 µs, while for the higher values of T 0 , this time shortened to 0.2 0.4 µs (see Fig.…”

“…The evident lack of such data has already resulted in a catastrophic increase in the number of models of thermal nonequilibrium dissociation [1]. The method of the vibrational temperature measurement behind the shock front under thermal and chemical nonequilibrium (T v = T ) was described earlier in [2]. In the present work, the pro¦les of the vibrational temperature T v and other parameters of gas §ow behind the strong shock front were used for determination of oxygen dissociation rate constants and vibrational relaxation time at temperatures up to 10,000 K. This allows the testing of some theoretical models of thermal nonequilibrium dissociation.…”