Drop break-up in turbulent pipe flow downstream of a restriction
Drop break-up in turbulent pipe flow downstream of a restriction
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DOI：
10.1016/j.ces.2005.05.012
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发表时间：
2005-12
影响因子：
4.7
通讯作者：
S. Galinat;O. Masbernat;P. Guiraud;C. Dalmazzone
中科院分区：
文献类型：
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作者：
S. Galinat;O. Masbernat;P. Guiraud;C. Dalmazzone
这项工作解决了液滴破碎过程中引起的横截面限制在管道中。本文设计了一套带有同心孔板的垂直塔内并流分散油包水（粘度比λ <$0.5）流动实验装置。已经使用高速层析成像研究了限制下游的液滴破碎。这项工作的第一个目标是处理一个全球性的分析的破碎过程中的稀释分散。在这种情况下，研究的操作参数是孔口限制比β、流动雷诺数Re和界面张力σ。首先将破碎区域绘制在β（Re）图上，并测量了不同雷诺数下的液滴尺寸分布。据观察，限制下游的平均液滴直径线性增加作为压降的平方根的倒数的函数。这种行为与珀西和斯利彻以前所作的观察是一致的。Journal，1983，29（1），161 - 164]。此外，实验的基础上观察单滴破碎下游的孔允许识别不同的破碎机制，并确定统计量，如破碎概率，平均碎片数和子滴分布。液滴破碎概率是基于最大压降的韦伯数的单调递增函数。碎片的平均数也是韦伯数的递增函数，并且减少的平均子滴直径随着韦伯数的增加而减小。在低和中等韦伯数的子滴分布是多峰的不对称破碎过程的结果。在一个简单的全球人口平衡模型，以预测在不同的雷诺数的限制，在稀分散体的限制，在单滴破碎实验的统计分析实施。
This work addresses the drop fragmentation process induced by a cross-sectional restriction in a pipe. An experimental device of an upward co-current oil-in-water dispersed flow (viscosity ratio λ≈0.5) in a vertical column equipped with a concentric orifice has been designed. Drop break-up downstream of the restriction has been studied using a high-speed trajectography. The first objective of this work deals with a global analysis of the fragmentation process for a dilute dispersion. In this context, the operating parameters of the study are the orifice restriction ratio β, the flow Reynolds number, Re and the interfacial tension, σ. The break-up domain has been first mapped on a β(Re) graph and drop size distributions have been measured for different flow Reynolds numbers. It was observed that the mean drop diameter downstream of the restriction linearly increases as a function of the inverse of the square root of the pressure drop. This behaviour is in agreement with the observations previously made by Percy and Sleicher [A.I.Ch.E. Journal, 1983, 29(1), 161–164]. In addition, experiments based on the observation of single drop break-up downstream of the orifice have allowed the identification of different break-up mechanisms, and the determination of statistical quantities such as the break-up probability, the mean number of fragments and the daughter drop distribution. The drop break-up probability was found to be a monotonous increasing function of the Weber number based on the maximal pressure drop through the orifice. The mean number of fragments is also an increasing function of the Weber number and the reduced mean daughter drop diameter decreases as the Weber number increases. The daughter drop distributions are multimodal at low and moderate Weber numbers as a result of asymmetrical fragmentation processes. The statistical analysis of single drop break-up experiments was implemented in a simple global population balance model in order to predict the evolution of the size distribution across the restriction at different Reynolds numbers, in the limit of dilute dispersions.