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Flame Spread Along Free Edges of Thermally Thin Samples in Microgravity.

pdf icon Flame Spread Along Free Edges of Thermally Thin Samples in Microgravity. (432 K)
Mell, W. E.; Olson, S. L.; Kashiwagi, T.

Combustion Institute, Symposium (International) on Combustion, 28th. Proceedings. Volume 2. July 30-August 4, 2000, Edinburgh, Scotland, Combustion Institute, Pittsburgh, PA, Candel, S.; Driscoll, J. F.; Burgess, A. R.; Gore, J. P., Editor(s)(s), 2843-2849 pp, 2000.


flame spread; microgravity


The effects of imposed flow velocity on flame spread along open edges of a thermally thin cellulosic sample in microgravity are studied experimentally and theoretically. In this study, the sample is ignited at the middle of the 4 cm width sample and subsequent flame spread reaches both open edges of the sample. The differing fates of the portions of the flame are observed in the experiments and predicted by the numerical calculation, in the order of increasing the imposed flow velocity; (1) ignition but subsequent flame spread is not attained, (2) flame spreading upstream (opposed mode) without any downstream flame, and (3) the upstream flame and two separate downstream flames traveling along two open edges (concurrent mode). Generally, the edge flame spread rate for both directions is faster than the central flame spread rate for an imposed flow velocity of up to 5 cm/s due to enhanced oxygen supply from the outer free stream. For the upstream flame, oxygen supply to the edge flame is sufficient so that the edge flame spread rate is nearly independent of or decreases gradually with the imposed flow velocity. However, downstream edge spread rate increases significantly with the imposed flow velocity.