Modification of chemical-kinetic parameters for 11-air species in re-entry flows

Abstract

The chemical-kinetic parameters for the two-temperature model for 11-air species are modified to increase the accuracy of the thermochemical nonequilibrium model for high temperature gases in Earth re-entry flows. In the present work, a set of modified chemical-kinetic parameters, for the vibrational relaxation time with high temperature correction, the Arrhenius rate coefficients for dissociation, the vibrational energy removal ratio due to chemical reaction, the equilibrium constant to evaluate the reverse rate coefficients, and collision integrals for high temperature gases are proposed, based on the results of recent state-to-state kinetic calculations and shock-tube experimental data. These modified chemical-kinetic parameters are utilized to reproduce the measured NO, N2, and N2+ VUV and UV spectrum of the high-enthalpy shock-tube experiments performed at the EAST facility, and the existing flight and ground experimental data from BSUV-2, the Mars-entry spacecraft model, RAM C-II, and FIRE-II. The proposed chemical-kinetic parameters more accurately reproduce the measured molecular spectra in the VUV and UV ranges, and the surface heat flux and electron number density on the surface of the re-entry modules, than the previous chemical-kinetic parameters in the Park model, except for the super orbital re-entry speed of the Fire-II experiments. In the Fire-II experimental case, the influence of the modified chemical-kinetic parameters in the present work are less effective because of the fast dissociation of the molecules.