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 O2 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 N2 are grouped as one energy mode, and vibrational energies of O2, O2+, 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 N2 and O2 need to be treated separately. The vibrational relaxation of O2 is much faster than that of N2 in low enthalpy condition, and the dissociation rate of O2 is manly influenced by the species vibrational temperature of O2. The proposed three-temperature model is able to describe the thermochemical nonequilibrium characteristics of N2 and O2 behind the incident and reflected shock waves, and the rapid vibrational freezing of N2 in nozzle expanding flows.