【作者】 张建国；

【导师】 马福昌；

【作者基本信息】 太原理工大学 ， 电路与系统， 2013， 博士

【摘要】 在高纬度国家以及我国北部与中西部高寒地区,以冰水两相流为主的冰水情问题(如凌汛、冰塞及冰坝等)直接危害到国家大型水利、水电工程设施,水工建筑与设备的安全运行；严重威胁着河道流域广大地区的国家财产与人民生命安全。为了防止灾难性后果的发生,国内外学者对冰水情灾害的检测、预报与防治进行了大量研究；目前冰水情问题的研究主要依赖于人工观测、数学建模分析和室内试验研究的方式,缺乏自动化程度较高的现场冰水情检测仪器。鉴于此种现状,本论文提出一种基于电阻层析成像(Electrical Resistance Tomography,简称ERT)原理的冰-水两相流检测方法,并利用该技术实现对冰水两相物质分布及其动态变化规律的研究。具体完成了以下工作：(1)研制了用于冰水两相流参数检测的ERT系统。试验证明该ERT系统具有对冰水两相体截面成像的功能。(2)提出了一种基于数字图像处理的截面冰相含率(Ice Packing Factor,简称IPF)计算方法。试验证明利用该算法计算出的IPF值与真实IPF值之间的比对误差≤6%,显示出较好的测量精度,可用于冰水两相流IPF值的定性与定量分析。(3)研制了用于微弱阻抗信号检测的相敏解调电路和程序,实现了高信噪比条件下冰水两相流的阻抗参数的高精度测量与实部(电阻)、虚部(电容)分离。(4)制作了电压控制电流源(Voltage Controlled Current Source,简称VCCS)电路,其恒流特性好,带负载能力强,提高了ERT系统在冰水两相流测量中的适用范围。(5)利用MATLAB软件,编写了ERT系统的图像重建算法程序,程序中包含了等位线反投影算法、灵敏度系数法、截断奇异值分解法和Tikhonov正则化算法。(6)为了验证所研制的ERT系统的实际性能,搭建了冰水两相流静态试验系统,对冰水两相体中冰相分布及其动态变化进行了成像测试。试验结果表明：通过ERT系统可以获得水槽内冰柱的位置以及实时运动图像,利用像素点颜色的不同来区分重建图像中水相分布区域与冰相分布区域,对比显著且直观；将图像进行灰度及二值化处理后,利用所提出的截面冰相含率(IPF)计算公式,获得了一组IPF值,且计算值与真实值之间比对误差在6%以内,证明了该方法的实用性。本论文的研究成果,将有可能在以下领域发挥重要作用：(1)为隧洞、管道等输水设施提供新的冰水情检测技术手段,为解决国家大型水利工程的冬季安全输水问题提供技术支持。(2)为大型冰蓄冷设备提供新式冰水两相流检测传感器技术,该技术能够准确获知冰水两相流的流型、IPF等参数,为制冷设备进行冷量控制、实施防冰堵措施提供决策依据,提高其实时监控及自动化管理水平。综上所述,面向冰水两相流参数检测的电阻层析成像技术研究是一项具有重要理论研究意义及实际工程推广应用价值的工作。本课题研究过程中获得国家自然科学基金项目《基于空气、冰与水物理特性差异的冰层生消过程与力学强度连续在线检测原理研究》及山西省自然科学基金项目《电阻层析成像系统在冰水两相流参数检测中的研究》的资助。更多还原

【Abstract】 In the high latitude countries and alpine region in north and west of China, disasters mainly caused by ice-water two-phase flows such as ice flood, ice jams and ice dam greatly endanger the safety of large hydraulic facilities, hydropower equipments and people’s property along the rivers. To prevent such disasters, foreign and domestic scholars did many jobs to forecast and detect conditions of ice-water two-phase flow. According to literature, researches mainly focus on field observation manually, analysis of mathematical models, indoors experiments, which have disadvantages of being lack of automatic detecting equiments for ice-water in field. This paper puts forwards a principle of ERT (Electrical Resistance Tomography) to detect the distribution and dynamic change of ice-wtaer two-phase flow. The main job is as follows: (1) ERT system to detect ice-water two-phase flow is developed, which has the tomogrphy fuction for two-phase sections and is proved by our experiments.(2) A calculating method for IPF (Ice Packing Factor) is put forward, which is based on digital image processing. The experimental results show that the errors of IPF are less than6%. Our system can be used to measure IPF of ice-water two-phase flow both quantitively and qualitytively.(3) A digital phase-sensitive detect circiuit and its program to detect weak impedance signals are developed, by which the seperation between real part(resistance) and image part(capacitance) is achieved in the condition of high SNA for ice-water two-phase flow measurement.(4) This paper improves the character of Voltage Controlled Current Source, namely VCCS, in the field of constant current, which strengthens the load capbility and enlarges the measuring scope of ERT system for two-phase ice and water.(5) Algorithms of image reconstruction for ERT system is developed by MATLAB, which include Linear Backprojection (LBP) algorithm, Sensitivity Coefficient algorithm, Truncated Singular Value Decomposition (TSVD) algorithm and Tikhonov Regularization algorithm.(6) In order to test the actual performance of ERT system developed, a static experiment system of ice-water two-phase flow is set up, and the image construction of dynamic distribution and variation of ice and water is tested. The result shows that the location and real-time moving state of ice column can be obtained by ERT system. Pixels of different colors are used to distinguish between water phase and ice phase. The images, which are processed by gray and binary conversion, are calculated by IPF formula. The calculated result shows that the error of phase fractions are less than6%,which indicates that our system can be used in real circumstance.The research results of this paper can play an important role in the following fields:(1) It provides a new ice-water detecting technique for the channels, tunnel, pipeline, other ice-water transfer facilities, and technical support for safe operation of national large water conservancy project in winter.(2) Our new detection technology of two-phase flow can be used in large ice storage equipments, with the characters of accurately obtaining two-phase flow pattern and IPF parameters. This technology can improve the level of real-time monitoring and automation management of refrigeration equipments.This work was supported by National Science Foundation of China(Grant No.51279122) and Shanxi Province Science Foundation for Youths (Grant No.2012021013-2).更多还原