Quantitative characterizations of long-period fluctuations in a large-diameter bubble column based on point-wise void fraction measurements
Quantitative characterizations of long-period fluctuations in a large-diameter bubble column based on point-wise void fraction measurements
复制标题
DOI：
10.1016/j.cej.2010.03.012
复制
发表时间：
2010-05-15
影响因子：
15.1
通讯作者：
Saito, Takayuki
中科院分区：
文献类型：
--
作者：
Higuchi, Masamori;Saito, Takayuki
长周期波动反映了鼓泡塔反应器内泡状流的大尺度结构，定量表征长周期波动对提高反应器效率至关重要。我们提出了一种新开发的方法来提取长周期波动的基础上逐点空泡率测量。新方法的有效性表明，通过在直径约400毫米和2000毫米的高度鼓泡塔的长周期波动的特性。首先，由一个单一的气泡群引起的液相运动的特性进行了描述的基础上，通过LDA测量得到的结果。大尺度液相运动的特征在于单个气泡簇（即具有相同空隙率的区域）。我们解释我们的新方法的前提下，这些结果的基础上。其次，我们表明，泡罩塔中的泡状流可以分为三个区域（即时空波动区，过渡区，和伪均匀区）的基础上的气泡直径和速度的分布模式的差异，以及从四点同时测量获得的时间序列逐点空隙率之间的差异。空间波动从柱底开始随着高度逐渐消失。最后，通过对四端光纤探针（F-TOP）测得的空泡率时间序列的分析，证明了通过波形分析可以提取出空泡率的长周期波动。特征光谱图案也随着高度而逐渐消失。所提取的长周期波动与从流动的可视化结果中获得的结果吻合得很好。(C)2010 Elsevier B. V.保留所有权利。
Quantitatively characterizing long-period fluctuations, which reflect the large-scale structure of a bubbly flow in a bubble column reactor, is essential to improving the reactor efficiency. We propose a newly developed method to extract the long-period fluctuations based on point-wise void fraction measurements. The validity of the new method is demonstrated via characterization of long-period fluctuations in a bubble column approximately 400 mm in diameter and 2000 mm in height. First, the characteristics of liquid-phase motion induced by a single bubble-swarm are described based on the results obtained via LDA measurements. The large-scale liquid-phase motion is characterized by an individual bubble cluster (i.e. a region with the same void fraction). We explain the premise of our new method based on these results. Second, we show that the bubbly flows in the bubble column can be divided into three regions (i.e. a time-spatially fluctuated region, a transition region, and a pseudo-homogenous region) based on differences in the distribution patterns of bubble diameters and velocities as well as those between time-series point-wise void fractions obtained from four-point simultaneous measurements. The spatial fluctuations fade out with height from the column bottom. Finally, analyzing the time-series point-wise void fractions measured via four-tip optical-fiber probe (F-TOP), we demonstrate that the long-period fluctuations can be extracted via waveform analysis. The characteristic spectrum pattern also fades out with height. The extracted long-period fluctuations are in good agreement with those obtained from the visualization results for the flows. (C) 2010 Elsevier B.V. All rights reserved.