Exothermic Reactions behind a Reflected Shock

Abstract

THE use of reflected shock waves to initiate exothermic reactions in a shock tube is commonly concerned with the ignition of oxygen and simple fuel molecules. The speed of the incident shock, U_s, determines the speed of the reflected shock, U_r, and the temperature, T₅, at which the reaction takes place. If T₅ is sufficiently high, an explosion occurs almost instantaneously and the reflected shock leaves the end plate at high speed because of the release of the energy of combustion. At lower temperatures there is an induction period, τ, before reaction occurs; a combustion-driven wave then sets out after the slower non-reactive reflected shock and eventually the two waves coalesce. The use of large windows near the end plate of the shock tube has permitted streak photography of this phenomenon for carbon monoxide–oxygen¹ and hydrogen–oxygen–argon² mixtures. A typical record is depicted in Fig. 1.