Clarification of Effect of Gravity on Flame Spreadaing over Condensed Phase and Its Extinction and Proposing of Extinguishing Method in Space

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To improve our understanding of the effects of gravity on flame characteristics, we conducted an experimental investigation on small-scale pool fires under different gravity levels to normal. The drop tower facility at Hirosaki University in Japan was used to obtain an arbitrary low gravity environment. For pool fire in low gravity environments, the measurements revealed that the puffing frequency and flame height declined with decreasing gravity. The flame height showed a tendency to peak at a certain level of gravity. Moreover, the normal velocity component to the flame sheet declined with decreasing gravity. To clarify the factor of puffing occurrence factor, experiments were performed using eleven different sizes of fuel pan and three different kinds of fuels. The occurrence of the puffing phenomenon, namely the puffing- limit, was summarized by the relation between the (H/D)limit and Grashof number, and found to be inversely proportional.