【作者】 谭超；

【导师】 董峰；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2006， 硕士

【摘要】 两相流是在自然界中广泛存在的流动现象,在工业生产与日常生活中起着十分重要的作用。由于两相流的流动状态复杂多变,对其流动参数的准确测量一直是工程与科研领域尚未有效解决的问题。两相流的测量方法有很多,其中的电阻层析成像技术(Electrical Resistance Tomography,简称ERT)通过测量敏感场内电导率变化,得到对象的流动特性,具有非侵入、无辐射、可视化等特点,在工业过程中有广泛的应用前景。本论文在利用ERT系统对两相流测量的基础上,对两相流的数据进行分析与特征参数提取,以实现对两相流流动特性与测量的研究,并针对现行ERT系统存在的性能问题,提出了新型ERT系统的设计方案。作者在本课题中完成的主要工作如下:1.利用数字接口板与A/D转换卡实现串行采集的ERT系统,在对系统实时性影响因素分析的基础上,提出了基于数字I/O卡与高速并行A/D转换卡的并行采集系统的设计方案。采用并行采集的方法可以减少测量信号的切换次数,进而提高系统工作速度。2.根据水平管道中气/液两相流动的特点,结合ERT系统自身的工作原理,利用各敏感电极的边界测量电压的特征值时间序列曲线,通过提取气相通过水平管道各个位置处电极的时间,并结合气相在管道内的分布,实现流型的特征提取与识别。3.在油/气/水实验装置上,使用相关ERT系统对垂直管道两相流进行动态实验,对采集到的不同截面距离下的测量数据,利用特征值相关的方法计算互相关速度,并结合漂移模型与运动波理论,分析弹状流条件下测得的互相关速度与理论运动波速的关系。更多还原

【Abstract】 Two-phase flow is one of the most common fluids in the nature, which also plays very important part in industry and daily life. Because of its complexity and variability, the real-time parameter measurement of two-phase flow becomes a difficult issue in the field of engineering and science.Many methods have been applied on measuring two-phase flow, the one with great perspective is Electrical Resistance Tomography (ERT) which can obtain the flow characteristic of two-phase flow by measuring the change of the conductivity in the sensing field that established by injecting exciting current into measured cross-section. The characteristic of this technique is non-intrusive, non-radiant, visualization and etc.The main achievements made in this thesis are as follows:1. The serial data-acquisition ERT system is designed with interface card and A/D transition card. Basing on the analysis of real-time performance of ERT system, the scheme of parallel data-acquisition system has been proposed. This new system uses digital I/O card and high speed A/D transition card to decrease the switch time of measured signal and to improve system performance.2. Combining the flow characteristic of gas/liquid two-phase flow in horizontal pipe with the operating principle of ERT system, the feature time of gas phase passing through each position of the measured cross-section is drawn from the time series of feature value of the measured boundary voltage from each sensing electrode. Along with the distribution of gas phase in pipe, these two parameters can be used for feature extraction and recognition of flow regime.3. The dual-plane ERT system has been adopted for the vertical two-phase flow real-time experiments on oil/gas/water three-phase flow facility. Many groups of experiments have been made with different separation of two sensing planes. The cross-correlation velocity is detained by correlating the feature value of measured data, and associating with drift-flux model and kinematic theory, the relation between the cross-correlation velocity and the kinematic propagation is investigated.更多还原