Effect of Ambient Gas on Flame Spread over a Solid Material in Microgravity

Int. J. Microgravity Sci. Appl. 2007p225
Author
S. TAKAHASHI, S. B. JEE, T. IHARA and K. WAKAI
Organization
Gifu University, San Diego State University
Abstract
The flame spread rate over a PMMA film was measured with varying ambient balance gas, N2, CO2, He and Ar, in normal gravity and microgravity. A scale analysis was also conducted to discuss how ambient flow velocity, Vg, and gas properties affect the flame behavior. With decreasing the Vg, the flame behavior moves to the microgravity-regime. However, the Vg at which the regime switches is different according to the ambient gas properties. In Ar and CO2 balances, the flame is robust even with very low Vg because of their small preheat-zone length, Lg is so large that the range of Vg where the thermal-regime is held is very narrow, which results in weak flame both in nomal gravity and microgravity. This result implies that not only the Vg but also the gas properties must be taken into account to discuss the flame spread in microgravity. The dimensionless hest loss number proposed by the present scale analysis gives good help to estimate the ‘‘critical folw velocity’’ below which the flame cannot spread.
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