High Pressure Burning of Methanol Droplets: A Comparison Between Parabolic Flight and Drop Tower Experiments

A franco-japanese collaboration program on microgravity combustion has been initiated. Part of this program is devoted to the investigation of high pressure methanol droplet vaporization and burning. Two different facilities have been used in Japan and in France both under normal gravity and reduced gravity conditions. Each facility uses the fiber suspended droplet technique. Experiments have been conducted jointly by the two teams. Reduced gravity conditions have been generated in France by the use of parabolic flights. Several experiments have been conducted in Japan at the JAMIC drop shaft. One objective of the study is to determine the pressure effects on the burning rate and burning time of methanol droplets, under both subcritical and supercritical gaseous environments. A related issue is to obtain this information under variable residual gravity levels, in order to analyze the gravity induced buoyancy effects on droplet burning phenomena Experiments with both facilities and under normal gravity and two residual gravity levels confirm the strong increase of the methanol droplet burning rates up to the critical pressure. Important quantitative differences have been however observed between the burning rate values obtained by using the two facilities, under normal gravity and reduced gravity. It appears therefore crucial to homogenize the experimental procedures in both facilities.