Thermochemical nonequilibrium modeling of oxygen in hypersonic air flows

The thermochemical nonequilibrium model for oxygen, O 2, in collisions with atmospheric gas species, is modified in the present work. The vibrational relaxation time with high temperature corrections, dissociation reaction rates, equilibrium constants for the reverse reactions, the vibrational energy loss ratio due to chemical reaction, and the collision integrals for nonequilibrium transport properties are proposed to describe the thermochemical nonequilibrium of O 2. The proposed set of thermochemical nonequilibrium parameters for O 2 successfully reproduces existing shock-tube experimental data and the flight and ground experimental data of the ELECTRE vehicle, orbital reentry experiments (OREX) flight modules, and double-cone geometry in the LENS-XX facility. In post-shock and hypersonic flow calculations, it is found that the vibrational relaxation and coupled chemical reactions calculated using the present parameters occur more slowly than using the previous parameters. The delayed nonequilibrium chemical reactions contribute to the extension of the shock stand-off distance, and drastically change the reverse reaction near the wall of the hypersonic vehicle.