Fire Safety Science Digital Archive

The behavior of t-he reverse flow in front of the leading flame edge spreading over kerosene-soaked sand in an air stream has been examined using a few flow visualization techniques, and the role of the reverse flow in the flame spread is discussed. In a wide range of the free stream velocities U from 30 to 210 cm/s, a stable reverse flow region in front of the leading flame edge was observed clearly, and its horizontal dimension was found to be almost independent of U. As U increases, the velocity of the reverse flow increases. The reverse flow takes an important role in the stable flame spread in an opposed air stream, although it has no appreciable effect. on the flame spread rate. The reverse flow provides a slow gas stream region, through which gasified fuel as well as heat from the reaction zone would be transferred in the upstream direction.