Evaporation and Ignition of Liquid Fuels at Critical Pressure Regime.

在高压高温环境中测量了燃料液滴的点火时间。将直径为0.35 ~ 1.4mm的正庚烷、正辛烷、正癸烷和正十六烷悬浮液滴快速浸入温度高达950 ℃的电炉中。在大气压到临界压力以上的空气容器中进行了液滴的附着、燃烧炉的运动和点火的测量，在大气压下测量的小液滴的点火时间在高压下不能观察到，并且对于本研究中使用的每种燃料，液滴不点火的直径随着压力的增加而变小。点火时间随压力单调下降，即使在超临界压力下，点火时间的行为没有太大的变化。与燃烧情况不同，在点火过程中，材料的性质并没有发生剧烈的变化。这主要是因为 ...更多信息 在第二阶段的研究中，我们研究了高压环境中正癸烷和正十六烷在悬浮燃料液滴阵列中的火焰传播现象。七个相同大小的液滴以相等的间距水平排列。在0.1 ~ 2.0MPa的压力范围内，采用高速摄像机对直径为0.50、0.75和1.0mm的液滴进行了火焰传播速率的测量，结果表明：随着液滴间距的减小，火焰传播速率增大，在一定间距处有最大值。液滴间距的进一步减小导致扩散速率由于大的汽化潜热而减小。火焰传播速率随压力的增加而减小，当压力超过临界压力时，火焰传播消失。这是由于火焰直径随压力迅速减小。少

Ignition times of a fuel droplet were measured in a high-pressure high-temperature ambient. Suspended n-heptane, n-octane, n-decane, and n-hexadecane droplets with diameters of 0.35 to 1.4mm were quickly immersed in an electric furnace at temperatures up to 950. Attachment of a droplet, movement of the furnace and measurement of ignition were carried out in an air vessel with pressures from atmospheric pressure to over the critical pressure.Relatively long ignition times of small droplets measured under atmospheric pressure could not be observed at high pressures and the diameter below which a droplet does not ignite became smaller with pressure for every fuel used in this research. Ignition time decreased monotonously with pressure, and even at supercritical pressures, the ignition time behavior did not change much. Being different from the case of combustion, it is suggested that drastic change of properties did not take place in ignition processes. This is basically because the surf … More ace temperature of the droplet is much lower for droplet ignition phenomena in comparison with the droplet burning.At the second stage of the research, flame spread phenomena in a suspended fuel droplet array were investigated for n-decane and n-hexadecane in a high-pressure ambience. Seven droplets of the same size were arranged horizontally at equal spacings. Flame spread rates were measured based on OH emission histories detected by a high-speed video camera with an image intensifier for droplet diameters of 0.50,0.75, and 1.0mm at ambient pressure from 0.1 to 2.0MPa.Results showed that, as droplet spacing became smaller, flame spread rate increased and had a maximum value at a certain spacing. A further decrease in droplet spacing caused the spread rate to decrease due to the large latent heat of vaporization. Flame spread rate decreased with pressure and no flame spread was observed at the pressure over the critical pressure. This is due to the rapid decrease in flame diameter with pressure. Less