The two chemical reactions given by N2O4 + M = 2NO2 + M = 2NO + O2 + M, where M represents the inert carrier gases argon or nitrogen, were studied. The experiments were carried out in a temperature controlled shock tube and a light absorption technique permitted the time dependent concentration of the species NO2 to be determined. For shock strengths where the temperature did not exceed 400K only the first chemical reaction took place. Stronger shock waves excited both chemical reactions with temperatures up to 2100K, and for this reason, flow fields with two nonequilibrium modes could be investigated. Since the relaxation times of these two reactions were different by about three orders of magnitude, they could be experimentally uncoupled. A study of the reaction mechanisms and rate constants for both reactions was carried out. At shock strengths exciting only the first chemical reaction the complete picture of a non-equilibrium flow field with only one nonequilibrium mode could be investigated. In this situation, the shock strengths were varied from weak, fully dispersed waves to strong, partly dispersed waves. (Author).

The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values.

The high temperatures generated in gases by shock waves give rise to physical and chemical phenomena such as molecular vibrational excitation, dissociation, ionization, chemical reactions and inherently related radiation. In continuum regime, these processes start from the wave front, so that generally the gaseous media behind shock waves may be in a thermodynamic and chemical non-equilibrium state. This book presents the state of knowledge of these phenomena. Thus, the thermodynamic properties of high temperature gases, including the plasma state are described, as well as the kinetics of the various chemical phenomena cited above. Numerous results of measurement and computation of vibrational relaxation times, dissociation and reaction rate constants are given, and various ionization and radiative mechanisms and processes are presented. The coupling between these different phenomena is taken into account as well as their interaction with the flow-field. Particular points such as the case of rarefied flows and the inside of the shock wave itself are also examined. Examples of specific non-equilibrium flows are given, generally corresponding to those encountered during spatial missions or in shock tube experiments.

The problem of calculating the flow behind a normal shock front is discussed. The additional complication of finite reaction rate chemistry has been included. A numerical method and several results of flow across a shock wave with an eleven-species, thirteen reaction model of air are presented. Results of the method are discussed and compared with those of Hall, Escheroeder, and Marrone (inviscid hypersonic air flows with coupled non-equilibrium processes. IAS 30th annual meeting, Jan 1962). (Author).