The effect of gas expansion on edge flames stabilized in narrow channels

In this paper we numerically examine the stabilization of an edge flame in a confined mixing layer. Unlike most previous theoretical studies which have assumed, for convenience, that the density is constant and independent of temperature, the present work realistically accounts for density variations and their effect on the flow field. The focus is on the effect of lateral confinement on the flame structure and standoff distance, for both adiabatic conditions and in the presence of conductive losses to the channel walls. The inability of the reactants to diffuse outwards, as they would in an unlimited mixing layer, promotes mixing and as a result the premixed flame segment extends further in the transverse direction, stands farther away from the tip of the splitter plate, and the trailing diffusion flame is much shorter. In very narrow channels the resulting flame is a planar premixed flame that consumes all the supplied reactants. Heat losses cause a drop in temperature and as a result, the premixed flame segment is limited near the channel axis, with a shorter diffusion flame trailing behind. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.