Chemical reactions in high-speed flows

Abstract

Hypersonic flows are distinguished by a capacity to provoke endothermic chemical reactions in their constituent molecules. Interactions of gas-flow and chemical activity also take place in combustible (exothermic) gas mixtures, such as may be found in propulsive devices. After a brief validation of the idea that chemically active flows can be adequately treated via Euler-Prandtl theory, the paper is devoted to a discussion of some particular features of chemically active very-high-speed Euler- inviscid flows. The treatment, which is fairly self-contained, brings out some of the similarities that exist between dissociative and combustible flows by emphasizing the central part played by shock-waves across which no chemical reaction takes place; in this way the treatment is novel and helps to point out the closer-than-usual links that exist between external and propulsive flows in the hypersonic environment. A new approach to the numerical computation of supersonic two-dimensional steady reacting flow fields is outlined, as is the potential role of large activation energy asymptotics in simple dissociating flows. Some new results and suggestions for the study of high-speed combustion bring the paper to a close.