Experimental Study on Upward Flame Spread Behaviors over Thin Fabric Fuels

Experiments were conducted on cotton fabric to study the characteristics of upward flame spread including flame front, pyrolysis front, flame height, pyrolysis height. Samples of cotton fabric were 1.80 m high and 1.35m wide, with thickness of 0.44 mm, 0.42 mm, 0.28 mm and 0.30 mm. It shows that: the evolutions of flame front, pyrolysis front, burnout front conform to a non-linear relation, and the speed of upward flame spread is not constant, but inconstantly accelerated. The flame height and pyrolysis height have a relation with the thickness of the thin fuels. A linear relation between flame height, pyrolysis height and time was observed appreciably in the two former tests, a power function with power value of 1.4~1.7 in the two latter tests, which accords with the fact that the upward flame spread of the thinner cotton fabric is faster than that of the thicker ones. The correlation between flame height and pyrolysis height is consistent with the power function Hf = αHpn. In the four upward flame spread experiments, the coefficient α varies within the range of 1.4 ~1.7 and the power coefficient n is equivalent to 1 approximately. Not affected by the thickness, the correlation between flame height and pyrolysis height is a linear function approximately.