I. E. Zabelinskii

Investigation of oxygen dissociation and vibrational relaxation at temperatures 4000–10 800 K

The oxygen absorbance was studied at wavelengths 200-270 nm in Schumann-Runge system behind the front of a strong shock wave. Using these data, the vibrational temperature Tv behind the front of shock waves was measured at temperatures 4000-10,800 K in undiluted oxygen. Determination of Tv was based on the measurements of time histories of absorbance for two wavelengths behind the shock front and on the results of detail calculations of oxygen absorption spectrum. Solving the system of standard quasi-one-dimensional gas dynamics equations and using the measured vibrational temperature, the time evolution of oxygen concentration and other gas parameters in each experiment were calculated. Based on these data, the oxygen dissociation rate constants were obtained for thermal equilibrium and thermal non-equilibrium conditions. Furthermore, the oxygen vibrational relaxation time was also determined at high temperatures. Using the experimental data, various theoretical and empirical models of high-temperature dissociation were tested, including the empirical model proposed in the present work.

Measurement of the vibrational temperature of oxygen behind a shock wave front under thermal and chemical nonequilibrium conditions

In shock tube experiments the profiles of light absorption in oxygen are obtained for the wavelength interval 200–260 nm over the temperature range 4000–10800 K. Using these data, the vibrational temperature profiles are measured for oxygen molecules behind the shock front. The method of determination of the vibrational temperature of oxygen is based on comparing absorption measurements and detailed absorption spectrum calculations for oxygen in the Schumann-Runge system.

Study of the absorption characteristics of molecular oxygen in the Schumann-Runge system at high temperatures: II. Experiment and comparison with calculation

Absorption cross sections of oxygen molecules in the UV spectral range are experimentally determined in the temperature range 1600–6000 K. The absorption cross sections are measured in oxygen or in its mixtures with argon behind the shock wave front. Measurements are performed for the spectral range 190–270 nm, which pertains to the electronic transition X3Σg− → B3Σu− of the Schumann-Runge system. The absorption cross sections are also measured at temperatures 291 and 3300 K in the range 160–185 nm. The measured absorption cross sections are compared with the calculated spectra of the O2 molecule.

Shock Tube Investigation of Molecular Oxygen Dissociation at Temperatures of 4000 to 10800 K

The quantitative experimental data on the vibrational temperature of dissociating molecules are informative characteristic for the evaluation of the relationship between the rates of vibrational relaxation and dissociation and for the development of suitable theoretical models of these processes. The evident lack of such data has already resulted in a explosive increase in the number of various dissociation models [1]. The technique of the measurement of the vibrational temperature of oxygen molecules behind the wave front under thermal and chemical nonequilibrium conditions was described earlier [2]. In the present work the evolution of the vibrational temperature T v behind the strong shock front was used for determination of oxygen dissociation rate constants and vibrational relaxation time under the thermal nonequilibrium conditions. This allows the testing of some of the theoretical models of thermal nonequilibrium dissociation.

Measurement of oxygen recombination rate constants by the piezoelectric method

The piezoelectric method is used to measure pressure in a gas flow within a nozzle, measurement results are compared with calculation, and values of the oxygen atom recombination rate constant are obtained for the temperature range 1680–3250°K.

Distortion of the shock front in a shock tube with a divergent conical transition section

The profile of the leading shock front in a gas has been experimentally investigated in shock tubes of variable cross section. It is shown that the presence of a conical transition section between the high-pressure and low-pressure chambers leads to the retention of inhomogeneities on the surface of the wave front (slopes, twists, and bends) over a length of 20–30 diameters.

Investigation of 10.6 μ absorption coefficient for carbon dioxide molecules at temperatures up to 3500°K

Experimental data are used to analyze features of resonance absorption processes in the high-temperature region, where the influence of hot transitions is appreciable.

Radiation Characteristics of Air in the Ultraviolet and Vacuum Ultraviolet Regions of the Spectrum behind the Front of Strong Shock Waves

Experiments on the measurement of air emission intensity behind the front of incident shock wave were carried out in a shock tube at an initial pressure of 0.25 Torr and shock wave velocities of 6.3–8.4 km/s. The emission intensity was measured in absolute units both in the form of an integral spectral distribution in a wavelength range of 120−400 nm (panoramic spectra) and as the time evolution of emission at the individual atomic lines of nitrogen and oxygen atoms. The results of the measurements demonstrated that the emission in air behind a shock wave in the vacuum ultraviolet region of 120–200 nm had a much higher radiation flux level than the emission in a range of 200–900 nm.

Some techniques for physical experiments in a shock tube with a nozzle

The authors describe a technique for experiments in a shock tube with a nozzle: operation of the high-pressure chamber, the pumping system, measurements of velocity and pressure, and absorption measurements in the nozzles.