Some Specific Aspects of Combustion in Supersonic H₂-Air Laminar Mixing Layers

Abstract

Development of Scramjet engines requires a detailed knowledge of the coupling between supersonic flow and chemical kinetics of combustion. In this paper we consider a stationary uniform, laminar supersonic mixing layer of hydrogen and air and investigate some conditions under which ignition occurs. More specifically, the influences of viscous dissipation effects, initial temperature and/or velocity gradients are investigated. This problem, where detailed chemistry for H₂-air is used, is solved numerically. The structure of the reactive mixing layer is shown to consist of an induction region, a thermal runawayregion, a region where both premixed and diffusion flames coexist, and a pure diffusion flame region. The exact length of the induction zone is found to depend sharply on the upstream boundary conditions and more precisely on the intensity of viscous dissipation together with amplitude and direction of transverse temperature and velocity gradients.