Error reduction, evaluation and correction for the intrusive optical four-sensor probe measurement in multi-dimensional two-phase flow
Error reduction, evaluation and correction for the intrusive optical four-sensor probe measurement in multi-dimensional two-phase flow
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DOI：
10.1016/j.ijheatmasstransfer.2006.01.054
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发表时间：
2008-02
影响因子：
5.2
通讯作者：
Xiuzhong Shen;K. Mishima;H. Nakamura
中科院分区：
文献类型：
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作者：
Xiuzhong Shen;K. Mishima;H. Nakamura
本研究的目的是增加多维两相流测量的可靠性，使用侵入式光学四传感器探头。从四传感器圆锥探头的基本原理出发，研究了减小四传感器圆锥探头制作误差的方法，并探索了四传感器圆锥探头的光纤针尖削尖控制技术和传感器装配方法。根据多传感器测头测量过程，将测量误差分为信号处理误差和流体动力学误差。分析了由阈值设置引起的空隙率信号处理误差以及由界面配对方案和阈值设置引起的界面面积浓度信号处理误差，并得出结论：在光学四传感器探针测量中，信号处理误差很小，可以忽略不计。根据气泡相对于探头的运动，将流体动力学误差分为迎面气泡误差、后退气泡误差和横向或缺失气泡误差。在IAC和空隙率由于迎面而来的气泡在四传感器探头测量的最大误差估计为10%。当气泡速度脉动强度为1且气泡尺寸接近探头间距时，传统的四探头横向气泡恢复方法对IAC的最大低估可达30%。在IAC和空隙率的最大测量误差的后退气泡的值分别为31%和38%，在低液体和高气体流速条件下，通过使用面向下和面向上的探头进行评估实验。为了克服后退气泡和横向气泡测量误差不理想的问题，提出了四传感器探头测量多维两相流中IAC和含气率的修正公式，该公式中加入了由于探头后部的阻碍而引起的逃逸气泡和由于探头之间存在有限距离而引起的横向气泡的贡献。
The objective of the present study is to increase the reliability of multi-dimensional two-phase flow measurement using an intrusive optical four-sensor probe. We investigated the error reducing ways in fabricating an optical conical four-sensor probe from its basic principles and sought for a control technique to sharpen the optical fiber tip and a sensor assembling method for a four-sensor probe. According to the measuring process by a multi-sensor probe, measurement errors were classified into signal processing errors and hydrodynamic errors. The signal processing errors in the void fraction due to the threshold setting and those in the interfacial area concentration (IAC) due to the interface-pairing scheme and the threshold setting were analyzed and concluded to be tiny and negligible in the measurement by an optical four-sensor probe. The hydrodynamic errors were classified into oncoming bubble errors, receding bubble errors and transversal or missing bubble errors according to the bubble motion relative to the probe. The maximum errors in both IAC and void fraction due to oncoming bubbles in a four-sensor probe measurement were estimated to be 10%. The maximum underestimation for IAC in the traditional transversal bubble recovering way of a four-sensor probe was reported up to 30% when the intensity of bubble velocity fluctuation equaled to 1 and the bubble size was close to the probe separations between sensor tips. The maximum measurement errors in IAC and void fraction for the receding bubbles were valued at 31% and 38%, respectively, at low liquid and high gas flow rates conditions by performing evaluation experiments using downward-facing and upward-facing probes. To overcome the unsatisfactory measurement errors for the receding and transversal bubbles, we proposed expressions for the correction of IAC and void fraction in the four-sensor probe measurement in a multi-dimensional two-phase flow by adding the contribution of escaped bubbles due to the hindrance of the probe rear parts and that of transversal bubbles due to the existence of finite distance separation between the sensor tips.