Diffusion Flame Attachment and Flame Spread Along Mixing Layers

An analysis is presented for the description of the diffusion flame attachment region to the splitter plate separating the fuel and air, which should provide the flame lift-off speed of the fuel Jet in laminar and turbulent diffusion flames.The region of flame attachment and the flow veloCity there are small enough to allow for a balance of convection and upstream diffusion, so that the complete quasi-steady Navier-Stokes equations must be used to describe the flow in this region. The problem that must be solved is posed and it is conjectured that for the typical values of the overall activation energy there is a diffusion controlled solution with a flame attached close to the splitter plate, only for values of the Jet flow veloCity below a critical value; otherwise the flame is lifted-off.For those small values of the Jet veloCity there is a second unstable solution, which may also be attached to the wake region of the plate, and a third nearly frozen solution. The transition from the nearly frozen solution to the stable attached flame solution is only possible after flame ignition by a hot source in the mixing layer and subsequent flame propagation along the local laminar mixing layers or vortex cores. The problem of flame propagation along the local laminar mixing layers is also posed.