Flame characteristics of small-scale pool fires under low gravity environments

The flame characteristics of pool fires such as oscillatory frequency, flame height, and so on differ depending on gravity. 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. Our measurements include analyses of oscillatory frequency and flame height under low gravity environments and flow visualization by a particle-track laser-sheet technique (PTLS) combined with a high-speed camera. These measurements revealed that the puffing frequency and flame height declined with decreasing gravity. The puffing frequency was summarized by the relationship between the Strouhal and Froude numbers. The flame height showed a tendency to peak at a certain level of gravity. The behavior of the flame height under low gravity did not correlate to the scaling prediction previously presented, while the normal velocity component to the flame sheet declined with decreasing gravity. The chemical reaction in the flame may be restricted due to decreasing oxygen supply. Consequently, the convective heat feedback to the liquid surface falls, causing the flame height to decline with decreasing gravity.