EFFECTS OF DIFFERENTIAL DIFFUSION ON UNSTEADY DIFFUSION FLAMES

The effects of differential diffusion on unsteady diffusion flames are considered far one-dimensional geometries. A Stefan problem is obtain ed for a single planar flame separating two semi-infinite regions cont aining fuel and oxidizer. Non-unity diffusivity ratio and the stoichio metry affect strongly the flame evolution and determine the conditions to obtain a stationary flame. A fuel strip surrounded by an oxidizer is considered and its burning can represent the burning of a gas pocke t or supercritical droplet. It is demonstrated for a fuel strip that i ncreasing O/F diffusivity ratios decrease the maximum flame expansion and decrease the burning times, while increasing initial equivalence r atios will increase the maximum flame expansion and will increase the burning times. (C) 1998 Elsevier Science Ltd.