Thermochemical nonequilibrium flow analysis in low enthalpy shock-tunnel facility

Area of Science:

• Aerospace Engineering
• Chemical Physics
• Computational Fluid Dynamics

Background:

• Accurate modeling of thermochemical nonequilibrium is crucial for understanding high-speed flows in shock-tunnels.
• Previous models, like two-temperature approaches, may not fully capture the complex energy exchange dynamics of different species.

Purpose of the Study:

• To develop and validate a novel three-temperature model for analyzing thermochemical nonequilibrium in low enthalpy shock-tunnel flows.
• To investigate the separate vibrational nonequilibrium behaviors of O2 and NO, distinct from N2.

Main Methods:

• Employed a quasi-one-dimensional flow calculation, dividing analysis into shock-tube and nozzle sections.
• Proposed a three-temperature model separating vibrational nonequilibrium of O2 and NO, grouping N2 vibrational energy with electron-electronic energies.
• Compared model results with experimental data and one- and two-temperature models across various K1 shock-tunnel facility conditions.

Main Results:

• The three-temperature model effectively describes thermochemical nonequilibrium, including vibrational relaxation and dissociation influenced by O2 vibrational temperature.
• Demonstrated that O2 vibrational relaxation is significantly faster than N2's at low enthalpies.
• The model accurately captures N2 and O2 behavior behind shock waves and rapid N2 vibrational freezing during nozzle expansion.

Conclusions:

• The proposed three-temperature model provides a more accurate representation of thermochemical nonequilibrium in low enthalpy shock-tunnel flows.
• Separate treatment of N2 and O2 nonequilibrium characteristics is essential for precise flow analysis.
• The model's ability to capture species-specific relaxation and freezing phenomena enhances predictive capabilities for hypersonic applications.