Calculation of Reaction Profiles behind Steady State Shock Waves. II. The Dissociation of Air

Abstract

A numerical integration procedure has been used to investigate the reaction profile behind strong shock waves in air. The Mach number range from 8 to 15 was covered; the initial temperature was 300°K; and the initial pressures were 1 and 10 mm Hg. The dissociation reactions for O₂, N₂, and NO were considered along with the ``shuffle'' reactions N+O₂⇄NO+O and O+N₂⇄NO+N. No ionization reactions were included. Above M_s=10, the calculations show a pronounced transient maximum in the NO concentration. In addition, the rates of change of concentrations at constant volume of all species except O₂ change sign under certain conditions. Several additional calculations were made which included an approximate treatment of the effects of a finite rate of vibrational excitation of O₂ and N₂. These calculations suggest that even at M_s=15, the vibrational excitation reactions have only a limited effect on the reaction profile. A calculation of the reaction profile for air at high pressure diluted with a large excess of inert gas at 3000°K showed that the Zeldovich mechanism approximately describes the production of NO under these conditions even though it fails completely for undiluted air at high temperatures.