Abstract
Ignition and flame spread phenomena of paper sheet in slow external air flow were observed in microgravity to prevent the effect of natural convection on the flow field. Two ignition methods, with wire heater (two-dimensional spread) and lamp heater (three dimensional spread), were examined to know the effect of flame front contour on the spread phenomena. The experimental parameters were air flow velocity (0-10 cm/ s) and oxygen concentration (21-50%). The ignition delay time and flame spread rate were measured for various experimental conditions based on the video images taken in microgravity. The experimental results showed that the flame spread rate increased with in crease in air flow velocity and oxygen concentration, which implied that the condition covered in the experiments were in the region of oxygen supply control. When oxygen concentration is high, the tendency to increase in flame spread rate for air flow velocity saturated over 5 cm/s. This revealed that it was easy for flame spread in high oxygen case to transfer from oxygen supply control to heat conduction control. Ignition delay time showed the negative dependency on oxygen concentration and weak dependency on external air flow velocity.
