微小重力環境下における雰囲気温度および二酸化炭素が酸化劣化オレイン酸メチル単一液滴の燃焼挙動におよぼす影響

抄録

Effects of the ambient temperature on oxidatively degraded methyl oleate (OME) droplet combustion were studied by conducting droplet combustion experiments at high temperature (750 ℃) and room temperature. Degraded OME was prepared with the Rancimat method, where a fuel sample was kept at 100 ℃ for 24 hours. Droplet combustion experiments were conducted at atmospheric pressure in air or CO₂ rich condition under microgravity. At both high and room temperature, puffing was observed during the droplet combustion for degraded OME, which may be due to the difference of volatilities between oxidation products. At high temperature, after a bubble was formed inside the droplet, it expanded abruptly, resulting in a droplet disruption. Although the droplet disruption accompanied mass loss of the droplet, a part of the fuel was remained on the suspender and continued burning. The remained fuel also showed bubble formation and disruption periodically until the end of the droplet lifetime. On the other hand, at room temperature, ejections of fuel vapor and tiny droplets were observed intermittently. This indicates that puffing occurred on the droplet surface because the surface was heated by a Fe-Cr wire to ignite the droplet. In addition, at room temperature, puffing stopped and the droplet began to burn quiescently at the latter stage of burning, which is probably because only high-volatile components were injected by puffing and a large amount of low-volatile ones were remained in the droplet. Furthermore, effects of CO₂. on puffing were studied at room temperature. However, no effects on similarity and the beginning time of puffing were observed. This indicates that droplet was heated approximately to the limit of superheat by a Fe-Cr wire, and effects of flame temperature were negligible