CIESC Journal ›› 2020, Vol. 71 ›› Issue (8): 3469-3479.DOI: 10.11949/0438-1157.20200300

• Fluid dynamics and transport phenomena • Previous Articles     Next Articles

Sensitive field characteristics and reconstruction algorithm improvement of ECT measurement with filling method in irregular structure

Zhao CHEN(),Meng CHEN,Jiangjiang WANG,Jiaxing CHANG,Malin LIU()   

  1. Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China
  • Received:2020-03-20 Revised:2020-05-18 Online:2020-08-05 Published:2020-08-05
  • Contact: Malin LIU

非规则结构电容层析成像填补法测量的敏感场特性及重构算法改进

陈昭(),陈猛,王江江,常家兴,刘马林()   

  1. 清华大学核能与新能源技术研究院,北京 100084
  • 通讯作者: 刘马林
  • 作者简介:陈昭(1995—),女,博士研究生,chenz-17@mails.tsinghua.edu.cn
  • 基金资助:
    国家自然科学基金项目(91634113);国家科技重大专项(ZX06901)

Abstract:

The measurement range of electrical capacitance tomography(ECT) can be extended by transforming the irregular area into regular imaging area by the filling method. First, the characteristics of the sensitive field corresponding to the filling method are analyzed, and then the effects of the sensitive field, the normalized capacitance, the dielectric constant of the filling area and the image reconstruction algorithm on the imaging of the filling method are studied. The Landweber algorithm was improved using the specific boundary conditions of the filling area, and two improved methods were proposed: the transformation matrix method and the split matrix method. The results show that the absolute value of capacitance signal is enhanced and the nonlinearity degree is increased using the filling method. The sensitive field with different background has little influence on the imaging, but the sensitive field with full filling area can enhance the annular flow imaging. The normalized capacitance matrix is benefit for image reconstruction. The reconstruction image changes to be the best when the dielectric constant of the filling material is close to the higher one of the measuring area. The split matrix method reduces the solution dimension, shortens the calculation time, and has a good overall effect on all kinds of flow pattern imaging. Finally, the reliability of the improved method is verified in the general irregular structure. The results show that the improved method can be used to measure the phase holdup distribution in the general irregular structure. It can also be used in the industrial occasions where the electrode cannot be directly installed due to high temperature and corrosion in the future, which has the general significance of improving the multiphase flow measurement method.

Key words: electrical capacitance tomography, reconstruction algorithm, irregular structure, two-phase flow, measurement

摘要:

利用填补的方式将不规则区域转为规则成像区,可拓展电容层析成像的测量范围。首先分析了填补法对应的敏感场特性,然后分别研究了敏感场、归一化电容、填充区介电常数和图像重构算法对填补法成像的影响。并利用特定的填充区边界条件对Landweber算法进行改进,提出两种改进方法:变换矩阵和拆分矩阵的Landweber图像重构方法。结果表明,填充区使电容信号绝对值增强,非线性程度增加。不同背景的敏感场对成像影响较小,但填充区充满时的敏感场可强化环状流成像。去除填充区噪声的归一化电容矩阵有利于图像重构。填充物质的介电常数与测量区高介电常数相近时成像最佳。拆分矩阵法降低了求解维度,缩短了计算时间,对各种流型成像整体效果较好,基于松弛因子改进还可进一步优化重构图像。最后,在一般非规则结构中对改进方法的可靠性进行了测试验证。研究表明,改进方法可以用于一般性不规则结构的相分布测量,未来还可以用于因高温、腐蚀等无法直接进行电极安装的工业场合中,具有改进多相流测量方法的普遍意义。

关键词: 电容层析成像, 重构算法, 非规则结构, 两相流, 测量

CLC Number: