Thermochemical nonequilibrium flow analysis in low enthalpy shock-tunnel facility.

Sanghoon Lee,Gisu Park,Jong Kook Lee,Ikhyun Kim,Jae Gang Kim,Hongbing Ding

doi:10.1371/journal.pone.0240300

Abstract

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.

Highlights

Hypersonic vehicles experience thermochemical nonequilibrium phenomena, which are induced by the hypersonic speed and the high enthalpy flow environment [1]
The difference in the species vibration temperature Tv and the electron-electronic-vibrational temperature Teev in the 3-T model is obvious. These results show that, in order to describe the nonequilibrium free stream conditions at the nozzle exit, the vibrational temperatures of O2 and NO need to be separated from the electron-electronic-vibrational temperature Teev
In the 3-T model, the electron translational energy, the electronic energies of atoms and molecules, and the vibrational energy of N2 are grouped as one nonequilibrium energy mode of the electron-electronic-vibrational energy, and the vibrational energies of O2, NO, and O2+ are treated as another nonequilibrium energy mode of the species vibrational energy

Summary

Introduction

Hypersonic vehicles experience thermochemical nonequilibrium phenomena, which are induced by the hypersonic speed and the high enthalpy flow environment [1]. The Q1D calculations are employed to analyze the thermochemical nonequilibrium of the shock-tunnel flows for the numerical efficiency. In low enthalpy flow conditions, below 8 MJ/kg, the 2-T model is less accurate when analyzing thermochemical nonequilibrium flows in a shock-tunnel facility. A three-temperature (3-T) model is proposed for analyzing thermochemical nonequilibrium flows below 8 MJ/kg in a low enthalpy shock-tunnel facility. To describe the thermochemical nonequilibrium phenomena in low enthalpy shock-tunnel flows, the present work introduces a 3-T model. Calculation of the thermochemical nonequilibrium flow, including the different vibration characteristics of N2 and O2 and related chemical reactions in the low enthalpy shock-tunnel operating environment. To describe the chemical reactions in the low enthalpy shock-tunnel flows the dissociation, exchange reaction, and associative ionization of the nine chemical species were considered. The conserved variables vector Q, the corresponding total flux vector E, and the source terms vector W can be represented as follows: rs rs u w_ s

Ev u 7

Findings

Discussion and conclusions