Effect of vibrational nonequilibrium of supersonic jets of CO2 on their gas-dynamic structure

A nonisobaric supersonic jet of vibrationally excited carbon dioxide exhausting from converging axisymmetric nozzles with the diameter ranging in a wide interval (from 0.03 to 114 mm) is studied experimentally and numerically. Numerical simulations are performed within the framework of the two-temperature approach with the use of the Landau–Teller relaxation equation for each vibrational mode of carbon dioxide molecules. The simulations reveal that the vibrational nonequilibrium of molecules affects the gas-dynamic structure of the jets in the temperature range of 300–900 K, and this effect is verified experimentally. Vibrational excitation of molecules in the experiment is ensured by means of gas heating. The effect of vibrational nonequilibrium is manifested as a reduction of the amplitude of the static pressure in wave structure cells and as a reduction of the longitudinal size and number of wave structure cells as compared to the case of an equilibrium supersonic flow. It is shown that the maximum effect of nonequilibrium is observed in jets exhausting from the nozzle with a diameter of ≅ 3 mm.