Microgravity Experiment on Flame Spread of a Fuel Droplet Array

Flame spread phenomena in a suspended fuel droplet array were experimentally investigated for n-decane and n-hexadecane in microgravity and normal gravity. Seven droplets of the same size were arranged horizontally at equal spacings. Flame spread rates were measured based on OH emission histories detected by a high-speed video camera with an image intensifier for droplet diameters of 0.50, 0.75, and 1.0 mm at ambient pressure from 0.1 to about 2.0 MPa. Results show that, as droplet spacing becomes smaller, flame spread rate increases and has a maximum value at a certain spacing in both microgravity and normal gravity. A further decrease in droplet spacing causes the spread rate to decrease due to the large latent heat of vaporization. The flame spread rate in microgravity is larger than that in normal gravity. The spacing at the flame spread limit in microgravity is more than two times as large as that in normal gravity, but the spacing at the maximum flame spread rate in microgravity is only a little larger than that in normal gravity.