Abstract The liquid-phase processes occurring during fuel droplet combustion are important in deciding the behaviour of the overall combustion process, especially, for the multicomponent fuel droplets. Hence, understanding these processes is essential for explaining the combustion of the multicomponent fuel droplet. However, the very fast combustion of the too small fuel droplet makes experimental investigation of these processes uneasily affordable. In the present work, a high speed backlighting and shadowgraph imaging of the multicomponent fuel droplet combustion including liquid-phase dynamics are performed. Two categories of multicomponent fuels – in which diesel is the base fuel – are prepared and utilized. The first category is biodiesel/diesel and bioethanol/diesel blends, while the second category is the water-in-diesel and diesel-in-water emulsions. Specific optical setups are developed and used for tracking droplet combustion. The first setup is associated with the backlighting imaging with the resulting magnification of the droplet images being 30 times the real size. The second optical setup is used for shadowgraph imaging, with the resulting magnification being 10 times the real size. Using these setups, spatial and temporal tracking of nucleation, bubble generation, internal circulation, puffing, microexplosion, and secondary atomization during the combustion of isolated multicomponent fuel droplets are performed. Spatial and temporal tracking of the sub-droplets generated by secondary atomization, and their subsequent combustion, in addition to their overall lifetimes have also been performed. Accordingly, a comparison of the burning rate constant between the parent droplet and the resulting sub-droplets is carried out. The rate of droplet secondary atomization is higher than those obtained by relatively low imaging rate. Additionally, it is shown that during a large portion of its entire lifetime, the droplet geometry has been affected by combustion significantly.

中文翻译：

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使用放大高速背光和阴影图成像进行多组分燃料液滴燃烧研究

摘要 燃料液滴燃烧过程中发生的液相过程对于决定整个燃烧过程的行为很重要，特别是对于多组分燃料液滴。因此，了解这些过程对于解释多组分燃料液滴的燃烧至关重要。然而，太小的燃料液滴的非常快速的燃烧使得对这些过程的实验研究难以负担。在目前的工作中，包括液相动力学的多组分燃料液滴燃烧的高速背光和阴影图成像被执行。制备和使用两类多组分燃料——其中柴油是基础燃料。第一类是生物柴油/柴油和生物乙醇/柴油混合物，而第二类是柴油包水和水包柴油乳液。开发了特定的光学设置并用于跟踪液滴燃烧。第一个设置与背光成像相关联，由此产生的液滴图像放大倍数为实际尺寸的 30 倍。第二个光学装置用于阴影图成像，产生的放大倍数是实际尺寸的 10 倍。使用这些设置，在孤立的多组分燃料液滴的燃烧过程中，可以对成核、气泡产生、内部循环、膨化、微爆炸和二次雾化进行空间和时间跟踪。除了它们的总寿命外，还对二次雾化产生的子液滴及其随后的燃烧进行了空间和时间跟踪。因此，进行母液滴和所得子液滴之间的燃烧速率常数的比较。液滴二次雾化率高于相对较低的成像率。此外，研究表明，在其整个生命周期的大部分时间里，液滴的几何形状受到燃烧的显着影响。