N<sub>2</sub>雰囲気におけるエマルジョン燃料噴霧流の二次微粒化挙動と粒径分布（二次微粒化挙動に及ぼす雰囲気温度の影響）

Abstract

In this study, secondary atomization of emulsified fuel spray was visualized, and the effect of ambient temperature on secondary atomization in spray flow was investigated. The W/O emulsified fuel was prepared by adding 10 wt% water and 0.75 wt% emulsifying agent (sorbitan monooleate) to n-dodecane. A shadow imaging system consisting of high-speed video camera (125,000 fps) and metal halide lamp was used to visualize secondary atomization of spray droplets. As a result, it clearly showed that secondary atomization of spray droplet was caused by vapor production inside the spray droplet due to the rapid evaporation of dispersed water. When the furnace wall temperature (Tw) was 823 K, there is no significant difference between the size distribution of emulsified fuel spray and that of n-dodecane spray because the droplet temperature was too low to produce vapor inside the spray droplet, leading to decreasing secondary atomization effect. Meanwhile, at Tw = 923 K and 973 K, the size distribution of emulsified fuel spray droplets was shifted to smaller than that of n-dodecane spray droplets. This is because the droplet temperature was enough to produce vapor inside the droplet and secondary atomization was enhanced. It was indicated that ambient temperature was important in the occurrence of secondary atomization.