Thermochemical nonequilibrium flow analysis in low enthalpy shock-tunnel facility

A thermochemical nonequilibrium analysis was performed under the low enthalpy shock-tunnel flows. A quasi-one-dimensional flow calculation was employed by dividing the flow calculations into two parts, for the shock-tube and the Mach 6 nozzle. To describe the thermochemical nonequilibrium of the low enthalpy shock-tunnel flows, a three-temperature model is proposed. The three-temperature model treats the vibrational nonequilibrium of O(2) and NO separately from the single nonequilibrium energy mode of the previous two-temperature model. In the three-temperature model, electron-electronic energies and vibrational energy of N(2) are grouped as one energy mode, and vibrational energies of O(2), O(2)(+), and NO are grouped as another energy mode. The results for the shock-tunnel flows calculated using the three-temperature model were then compared with existing experimental data and the results obtained from one- and two-temperature models, for various operating conditions of the K1 shock-tunnel facility. The results of the thermochemical nonequilibrium analysis of the low enthalpy shock-tunnel flows suggest that the nonequilibrium characteristics of N(2) and O(2) need to be treated separately. The vibrational relaxation of O(2) is much faster than that of N(2) in low enthalpy condition, and the dissociation rate of O(2) is manly influenced by the species vibrational temperature of O(2). The proposed three-temperature model is able to describe the thermochemical nonequilibrium characteristics of N(2) and O(2) behind the incident and reflected shock waves, and the rapid vibrational freezing of N(2) in nozzle expanding flows.