Experimental understanding on the dynamics of micro-explosion and puffing in ternary emulsion droplets
Experimental understanding on the dynamics of micro-explosion and puffing in ternary emulsion droplets
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DOI：
10.1016/j.fuel.2018.11.112
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发表时间：
2019-03
期刊：
影响因子：
7.4
通讯作者：
Madan Mohan Avulapati;T. Megaritis;J. Xia;L. Ganippa
中科院分区：
文献类型：
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作者：
Madan Mohan Avulapati;T. Megaritis;J. Xia;L. Ganippa
利用高速背光成像技术，研究了高温环境下三元燃料乳化液液滴膨胀和微爆现象的动力学。将由柴油-生物柴油-乙醇乳状液组成的单个液滴放置在直径为75 µm的热电偶的顶端，并将其快速引入保持在500 °C的炉膛中，观察到了悬浮液滴的振荡、液滴内部发生的物理变化、蒸汽排放、膨胀、微爆炸、成片、穿孔生长、片状解体和二次液滴的旋转等有趣的特征。高分辨率图像分析显示，悬浮液滴核心内的乳状液成分分离，表现为单核或多核。确定了两种不同类型的微爆炸。因为液滴与核心的单个核相遇，导致更强的蒸汽排出，随后发生强烈的微爆炸。因为在核心具有多个核的液滴在微爆炸之前导致较弱的蒸汽排出和较慢的液滴生长。两种类型的微爆过程都产生了大量的子液滴。对于强排汽的情况，近80%的子液滴的尺寸分布在150 μm以内，相比之下，排汽较弱的情况下，这一比例为60%。在自由悬浮环境中，由膨化和微爆两个主要事件产生的子液滴进一步级联为膨胀和微爆的二次和三次事件。
Dynamics of puffing and micro-explosion phenomena occurring in ternary fuel emulsion droplets under high temperature environment were explored using high speed backlight imaging technique. A single droplet composed of diesel-biodiesel-ethanol emulsion was placed at the tip of a 75 µm gauge thermocouple and introduced rapidly into a furnace maintained at 500 °C. Several interesting features such as oscillation of suspended droplets, physical transformations occurring within the droplet, vapour expulsion, puffing, micro-explosion, sheet formation, perforations, growth of perforations, sheet disintegration and rotation of secondary droplets were observed. High resolution image analysis revealed separation of emulsion components within the core of the suspended droplet, which appeared either as a single nucleus or multiple nuclei. Two distinct types of micro-explosion were identified. For droplets encountering a single nucleus at the core resulted in a stronger vapour expulsion followed by intense micro-explosion. For droplets having multiple nuclei at the core resulted in a weaker vapour expulsion and slower growth of droplet prior to micro-explosion. Both types of micro-explosion process resulted in a number of child droplets. For the case of strong vapour expulsion nearly 80% of its child droplets have their sizes distributed within 150 μm compared to 60% for weaker vapour expulsion. The child droplets that were generated from the primary events of both puffing and micro-explosion cascaded further into secondary and tertiary events of puffing and micro-explosion in freely suspended environment.