Measurement technique of bubble velocity and diameter in a bubble column via single-tip optical-fiber probing with judgment of the pierced position and angle
Measurement technique of bubble velocity and diameter in a bubble column via single-tip optical-fiber probing with judgment of the pierced position and angle
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DOI：
10.1016/j.ces.2013.01.046
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发表时间：
2013-08-30
影响因子：
4.7
通讯作者：
Saito, Takayuki
中科院分区：
文献类型：
--
作者：
Mizushima, Yuki;Sakamoto, Akihiro;Saito, Takayuki
我们的目标是提高单端光纤探针（S-TOP）测量泡状流中气泡的精度。S-TOP仅使用一个楔形尖端，同时测量气泡的逐点空隙率、速度和直径。S-TOP结构非常简单，但是引起了S-TOP和气泡之间的触摸位置/角度不清楚的问题。为了解决这个问题，我们提出了一种预信号阈值方法。前信号是来自S-TOP的噪声光信号之一。首先，S-TOP信号定量分析与新开发的三维计算射线跟踪方法，模拟器可以跟踪巨大的光线段轨迹在光纤和渲染复杂的光学边界条件。此外，在模拟器中，复杂的输出信号的评估是通过计算每个射线的偏振和能量。我们发现前信号的强度指示S-TOP是否正常接触气泡的中心区域，或者不。我们将这一特性应用于实际的S-TOP测量泡状流。结果，通过S-TOP测量的弦长与来自可视化图像的气泡短轴之间的差异从42%（现有信号处理）显著改善到15%（通过该方法处理）。(C)2013爱思唯尔有限公司保留所有权利。
Our objective is to improve the accuracy of bubble measurement with single-tip optical fiber probe (S-TOP) in a bubbly flow. The S-TOP measures a point-wise void fraction and a velocity and diameter of a bubble simultaneously, by using only a single wedge-shaped tip. The S-TOP structure is very simple but raises an issue of an unclear touch position/angle between the S-TOP and a bubble. We propose a pre-signal threshold method in order to solve this issue. The pre-signal is one of the noisy optical signals from the S-TOP. First, the S-TOP signals are quantitatively analyzed with a newly developed 3D computational ray tracing method; the simulator can trace enormous ray segment trajectories in an optical fiber and render complicated optical boundary conditions. Moreover, in the simulator, evaluation of the complex output signals is achieved by computing the polarization and energy of every ray. We discovered that the intensity of the pre-signal indicates whether the S-TOP touches normally the center region of the bubble, or does not. We applied this characteristic to practical S-TOP measurement of a bubbly flow. As a result, the difference between the measured chord length via the S-TOP and the bubble minor axis from visualized images was significantly improved from 42% (existing signal process) to 15% (with processing through the method). (C) 2013 Elsevier Ltd. All rights reserved.