Abstract: The high temperature gas occurs behind shock or near the wall surface of vehicle in the hypersonic flight. As the temperature exceeds 2 000 K, 4 000 K, respectively, O₂ and N₂ molecules are successively dissociated. Because of variable components at different temperatures and pressures, the dissociated air is no longer a perfect gas. In this paper, a new method is developed to calculate accurate thermal physical parameters with the dissociation degree providing the thermochemical equilibrium procedure. Based on the dissociation degree, it is concluded that few numbers of equations and the solutions are easily obtained. In addition, a set of formulas relating the parameter to the dissociation degree are set up. The thermodynamic properties of dissociated air containing four-species, O₂ molecule and N₂ molecule, O atom and N atom, are studied with the new method, and the results are consistent with those with the traditional equilibrium constant method. It is shown that this method is reliable for solving thermal physical parameters easily and directly.

Key words: junction, scaling, junction condition, convergence, equilibrium constant, dissociation degree, dissociated air, thermal physical parameter