【作者】 马敏；

【导师】 王化祥；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2007， 博士

【摘要】 多相流体系在自然界和工业过程中广泛存在,多相流流动参数的准确测量对科学研究和工程技术有着重要的意义。本文以油/气/水三相管流为研究对象,研究基于低能γ射线的多相管流在线检测技术,通过直接或间接参数测量,获得被测管路中截面分相含率、分相流量等有关参数,并实时提供可视化图像。本课题主要对系统硬件结构、系统软件以及重建算法三部分进行了深入研究,主要研究工作和结果如下:1.多相流在线检测系统硬件优化设计作者通过分析在线检测多相流参数影响因素,利用Geant4软件包对射线源的选择、探测单元、系统结构进行了仿真优化,并以此为依据,进行系统硬件的优化设计。主要包括射线成像系统硬件结构设计;核辐射探测器的选择及探测装置设计;微弱信号拾取及处理单元设计;基于FPGA的数据采集子系统设计。2.信号处理单元设计本课题的研究对象为油/气/水三相流,其流动状态较复杂,而放射性射线测量本身具有随机性、统计涨落特性,并且CdZnTe半导体探测器的输出信号较弱,给准确测量造成一定困难。作者在对噪声分析的基础上,对弱信号检测、噪声处理、信号快速采集处理和数据传输等方面进行了研究,提出了一种专用的对CdZnTe探测器输出弱信号的处理方法。3.多相流在线检测系统软件开发应用Visual C++6.0编程环境设计了一套基于32位Windows平台的射线实时成像软件系统CT_SystemII。软件系统主要包括六个功能模块:标定功能模块,测量功能模块,串口通讯功能模块,算法实现与应用模块,图形显示模块,数据存储和回放模块。实现了标定和计量功能,并可实时显示管道横截面流体的相分布图像。4.重建算法研究在深入研究滤波反投影和迭代算法基础上,结合本课题研究对象的特性,提出一种基于滤波反投影的迭代算法,仿真实验表明,该算法提高了图像重建质量,并具有较好的实时性。在深入研究Lanczos方法基础上,提出一种基于双对角化的迭代算法,该算法在保证精度的前提下,提高了成像速度。最后,作者对应用核技术进行在线快速探测多相流的研究,提出了进一步改进的建议。更多还原

【Abstract】 Since the multiphase flow broadly exists in nature and industrial process, the measurements of fluid dynamics parameters are of great significance in both scientific research and engineering. The subject of this thesis is oil/gas/water multiphase flow, and online measurement of multiphase flow based on low-energyγ-ray radiation is mainly studied. Fluid dynamics parameters, like phase fraction and fraction phase flux, on each cross-section of the detecting pipeline are obtained using direct or indirect methods, and real-time images are provided.This project is mainly focused on the design of the hardware system, the image reconstruction software package and the novel reconstruction algorithms. The following researches are conducted and the corresponding results are listed below.1. Optimization of the hardware design of the multiphase flow online measurement systemBy the analysis of the factors influencing the online multiphase parameters and the simulations of sensing system by Geant4, the hardware configuration is designed. This research mainly consists of four parts: the design of the hardware system for Gamma-Ray tomography, the CdZnTe semiconductor detector arrays, the signal processing unit for the output of detectors, and the data acquisition sub-system based on FPGA.2. The Design of Signal Processing UnitThe flow state of oil/gas/water multiphase flows is relatively complex and the measurement ofγ-ray is of randomization and statistical fluctuating property in itself. Considering that the output signal of the semiconductor detectors is too weak, it can hardly be measured accurately by normal signal processing units. Based on the analysis of the measurement noise, the research on detecting the weak output signal and filtering the measurement noise and etc. is studied in the thesis. A method with respect to the weak output of the CdZnTe detectors is proposed. 3. The development of online measurement software system used in the multi-phase systemBased on 32 digit Windows platform, the real time imaging system (CT_SystemII) is designed using Visual C++ 6.0. There are six functional units: the calibration unit, the measurement unit, the serial communication unit, the algorithm implementation and application unit, the imaging visualization unit, and the data storage and replay unit. With the CT_SystemII, the calibration and measurement of flow parameters can be realized, and additionally the cross-sectional images of the phase distribution can be displayed online.4. Research on imaging reconstruction algorithmsHaving an insight into the research of the filtered back projection method and iterative method, a new iterative algorithm based on filtered back projection is proposed. This algorithm combines the filtered back projection method with iterative method, applying the results of the filtered back projection as the initial guess for iterations. Simulation results show that the proposed method can improve the quality of reconstructed images with high speed which can meet the requirements of real-time measurement. Another image reconstruction algorithm, bidiagonalization algorithm, is also proposed in the thesis. Results indicate that this algorithm can reach the satisfactory accuaracy with less time.Finally, the suggestion of the further applications of nuclear technology to the online multiphase detection device is put forward at the end of this thesis.更多还原