Combustion and Evaporation of Liquid Fuel under the Supercritical Condition at Normal Gravity and Micro Gravity

1.常重力下的高压燃烧实验(1)对于重油等多组分燃料，燃烧时间随环境压力的增加而迅速增加，当压力高于2 Mpa时，燃烧时间基本不变。这一趋势类似于单组分燃料的趋势。碳烟浓度随着环境压力的增加而迅速增加，在0.5 Mpa以上时几乎不变。(2)对于乳化燃料，在常压下观察到微爆炸的发生，在0.5 Mpa以上时没有观察到微爆。研究还发现，碳烟浓度随着环境压力的增加而增加，然后几乎保持不变。微重力作用下单组分燃料的燃烧实验从6m的高空坠落组件产生微重力场，产生的微重力有效时间约为1 S。直接拍摄的照片显示，在液滴周围形成了球形火焰。微重力下的燃烧速率常数略小于正常重力下的燃烧速率常数。微重力下乳化燃料的燃烧实验(1)正十六烷/水乳状液的等待时间比正十二烷/水乳状液的等待时间短得多。这一结果表明，微爆炸的发生在很大程度上受试验燃料沸点的影响。(2)微爆炸在正常重力条件下比微重力条件下开始发生得更早。这一结果表明，微爆炸行为受重力条件的影响。目前正在对微爆炸的机理进行更详细的研究。

1. High Pressure Combustion Experiments under Normal Gravity(1) The burning time increases rapidly as the ambient pressure increases, and it becomes almost constant at pressures above 2 MPa, for the multicomponent fuel such as the heavy oil. This tendency is similar to that for single component fuels. The soot concentration increases rapidly with increase in the ambient pressure, and it becomes almost constant at pressures above 0.5 MPa.(2) For the emulsified fuel, the occurrence of microexplosion is observed at the atmospheric pressure, and it is not observed at the pressures above 0.5 MPa. It is also found that the soot concentration increases with increase in the ambient pressure and then it becomes almost constant.2. Combustion Experiments of the Single Component Fuel under Micro GravityThe Micro gravity field was generated by dropping an assembly from a height of 6 m, which can produce an effective time of micro gravity about 1 s. The direct photograph showed that the spherical flame was formed around the droplet. The burning rate constant at the micro gravity is slightly smaller than that at the normal gravity.3. Combustion Experiments of the Emulsified Fuel under Micro Gravity(1) The waiting time, which is defined as the time period between ignition and the onset of microexplosion, is much shorter for the n-hexadecane/water emulsion than that for the n-dodecane/water emulsion. This result suggests that the onset of microexplosion is largely affected by the boiling point of the test fuel.(2) The microexplosion begins to occur earlier under the normal gravity condition than the micro gravity condition. This result suggests that the microexplosion behavior is affected by the gravity condition. More detailed studies of the mechanism of the microexplosion are being carried out.