Study of the effects of walls on vortex formation and liquid maldistribution with two-phase flow around a spherical particle via numerical simulation
Study of the effects of walls on vortex formation and liquid maldistribution with two-phase flow around a spherical particle via numerical simulation
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通过数值模拟研究壁对球形颗粒周围两相流涡流形成和液体分布不均的影响
DOI：
10.1016/j.powtec.2019.05.070
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发表时间：
2019-09
影响因子：
5.2
通讯作者：
Du Wei
中科院分区：
文献类型：
--
作者：
He Guangxiang;Mo Hanyang;Zhang Rongrong;Jin Haibo;Du Wei
随着对固定床反应器（FBRs）工业催化活性的日益依赖，近年来基于液膜在颗粒表面扩散行为的微尺度数值研究引起了人们的广泛关注。然而，大多数研究都是单独研究一种颗粒，而没有考虑血管壁或其他颗粒的影响。在我们之前的研究中，我们发现液体的扩散行为和流动模式与颗粒下的气体涡旋及其形状密切相关。因此，在本工作中，将气体涡旋的形成和规模以及在流动过程中气体涡旋的产生和破裂作为模拟参数。采用ANSYS FLUENT v15.0软件，在不同的工作参数下，对近壁结构和正常结构两种几何形状进行了假设和研究。结果表明，无壁面效应的气体涡旋的大小和形成都比有壁面效应的气体涡旋更大、更稳定，相应的，由于粒子附近气体迹线的等效速度，无论气液速度如何（G/L），液膜都能很好地分布在表面。而在近壁面构型中，当平面壁面靠近颗粒时，颗粒下的两个涡可能会在流动过程中破裂并合并成一个更大的涡，导致颗粒表面液体分布不均匀。气迹的速度是不相等的，甚至会引起反向流动，从而将液相困在间隙内，可以通过增加G/L速度的速率和在颗粒与平壁面之间设置更大的间隙来缓解。新发现的信息将增强对颗粒表面液体扩散行为的理解，从而适用于快堆的性能。
With the ever-increasing dependency on the activity of industrial catalysis in fixed bed reactors (FBRs), recent microscale studies based on liquid film spreading behavior on particle surfaces using numerical methods have attracted much attention. However, most studies have investigated one particle separately, and the effects of vessel walls or other particles are not considered. In our preceding study, we found that liquid spreading behavior and flow patterns are strongly related to the gas vortex and its shape under the particle. Therefore, in this work, the formation and scale of the gas vortex, as well as its generation and breakdown during the flow process, are considered as the parameters in the simulation. Two geometries named the near-wall configuration and the normal configuration were assumed and fully investigated using ANSYS FLUENT v15.0 with different operating parameters. As a result, both the size and the formation of the gas vortex without wall effects are larger and steadier than those with wall effects, and correspondingly, the liquid film is well distributed on the surface regardless of the gas and liquid (G/L) velocity because of the equivalent velocity of the gas trace near the particle. In contrast, in the near-wall configuration, when the flat wall approaches the particle, two vortexes under the particle probably break down and further merge into one larger vortex and cause liquid maldistribution on the particle surface during the development of the flow process. The velocities of the gas traces are inequivalent, even causing a reversed flow and thus trapping the liquid phase inside the interstices, which can be alleviated by increasing the rate of G/L velocity and setting a larger interstice between the particle and the flat wall. The newly uncovered information will enhance the understanding of liquid spreading behavior on particle surfaces and thus be applicable to the performance of FBRs.
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影响因子：
3.7
作者：
D. Krieg;J. A. Helwick;P. Dillon;M. McCready
通讯作者：
D. Krieg;J. A. Helwick;P. Dillon;M. McCready
影响因子：
11.4
作者：
W. P. Tritt
通讯作者：
W. P. Tritt
影响因子：
4.7
作者：
Jingyuan Sun-;Jingdai Wang;Yongrong Yang
通讯作者：
Jingyuan Sun-;Jingdai Wang;Yongrong Yang
影响因子：
5.3
作者：
R. Ben-Slimane;M. T. Hepworth
通讯作者：
R. Ben-Slimane;M. T. Hepworth
影响因子：
5.3
作者：
P. Andrigo;R. Bagatin;G. Pagani
通讯作者：
P. Andrigo;R. Bagatin;G. Pagani