The flow field of a diffusion flame attached to a thick-rim injector between two coflowing streams of fuel and oxidiser is analysed in the Burke-Schumann limit of infinitely fast reaction rate. The length of the recirculation región immediately behind the injector and the velocity of the recirculating fluid are proportional to the shear stresses of the reactant streams on the wall of the injector for a range of rim thicknesses, and the structure of the flow in the wake depends then on three main non-dimensional parameters, measuring the gas thermal expansión due to the chemical heat reléase, the air-to-fuel stoichiometric ratio of the reaction, and the air-to-fuel ratio of wall shear stresses. The recirculation región shortens with increasing heat reléase, and the position of the fíame in this región depends on the other two parameters. An asymptotic analysis is carried out for very exothermic reactions, showing that the región of high temperature around the flame is confined by neatly defined boundaries and the hot fluid moves like a high-velocity jet under a favourable self-induced pressure gradient. The immediate wake is surrounded by a triple-deck región where the interacting flow leads to an adverse pressure gradient and a reduced shear stress upstream of the injector rim for sufnciently exothermic reactions. Separation of the boundary layers on the wall of the injector, however, seems to be postponed to very large valúes of the gas thermal expansión.
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