High-Temperature Air Kinetics

Chemical and vibrational nonequilibrium in high-temperature, shock-heated air strongly influences the thermodynamic state in the flow fields around hypersonic vehicles and spacecraft on atmospheric entry.

The finite rates for vibrational excitation of oxygen (O₂) and nitrogen (N₂) – called vibrational relaxation – and chemical reactions involving O₂, N₂, nitric oxide (NO), nitrogen atoms (N), and oxygen atoms (O) especially influence the equilibration of air behind a strong shock. However, previous experimental data, mostly from the 1960s, exhibit large scatter, which hinders the modeling of hypersonic flow fields.

In the Hanson Research Group, we use ultraviolet (UV) lasers to probe oxygen O₂ and NO at high temperatures. To date, we have probed reactions up to 14,000 K, a temperature that is more than twice the surface temperature of the sun! Our experimental results can improve heat transfer models for hypersonic vehicles, which can reduce the cost of these vehicles and increase the available payload weight while maintaining an appropriate factor of safety.

To learn more, check out some of our publications:

[1] J. W. Streicher, A. Krish, and R. K. Hanson, “Coupled vibration-dissociation time-histories and rate measurements in shock-heated, nondilute O₂ and O₂/Ar mixtures from 6,000-14,000 K,” Physics of Fluids 33 056107, 1–27 (2021). DOI: 10.1063/5.0048059

[2] J. W. Streicher, A. Krish, R. K. Hanson, K. M. Hanquist, R. S. Chaudhry, and I. D. Boyd, “Shock-tube measurements of coupled vibration-dissociation time-histories and rate parameters in oxygen and argon mixtures from 5,000-10,000 K,” Physics of Fluids 32 076103, 1–21 (2020). DOI: 10.1063/5.0015890

[3] J. W. Streicher, A. Krish, and R. K. Hanson, “Vibrational relaxation time measurements in shock-heated oxygen and air from 2,000-9,000 K using ultraviolet laser absorption,” Physics of Fluids 32 086101, 1–17 (2020). DOI: 10.1063/5.0012426