Flame Spread over Fuel Soaked Sand in an Opposed Air Stream

Flame spread over kerosene soaked sand in a quiescent, atmosphere and an opposed air stream has been examined, and the effects of the air stream on the fl arne spread mechanisms are discussed. The aspects of spreading flames, the flame spread rate, and t.he temperature d i.s t.r i buti.ons near leading flame edges were examined for various initial temperatures T. of kerosene soaked sand and free stream velocities U of the opposed i. air stream. As U increases, the flame near Lt.s leading edge approaches the sand surface. The flame spread r a t.e Vf at U=O increases considerably with T.. As U increases, Vf decreases rapidly and then graduallydecreas1?s until U becomes 275 cmls in the Li.mi ts of present e xpe r i.men ts. When U exceeds 275 cm y s, the flame spread becomes unstable and Vfdecreases rapidly. In the case of U=O, the heat transfer from the flame zone t.o the unburned region ahead of the leading flame edge seems t.o depend largely on the flame radiation. On the other hand in the case of U 0, the heat transfer t.o the unburned region seems to depend largely on t.he heat conduction through the sand layer. The stabil izat ion of the leading flame edge associated with the aerodynamic atru c tur e of the reverse flow region is found t.o be necessary for the stable flame spread