【作者】 张志强；

【导师】 董峰；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2012， 博士

【摘要】 两/多相流体的流动过程不仅是日常生活和自然界的常见现象，而且广泛存在于能源、石油、化工、冶金、制冷、宇航、医药、食品等现代工业过程中。其流动参数的测量，对于国民经济发展、资源的合理有效的利用有重大而深远的意义。然而，在两/多相流的流动过程中，由于相间流动特性差异、相间界面复杂多变，使得多相流参数的精确测量一直是科学研究和工业过程中的热点和难点。因此，课题的研究从多相流可视化测量的角度出发，对多相流的可视化测量手段，特别是层析成像技术进行了研究和分析，开发新型可视化测试传感器用于多相流的过程参数的测量和分析。主要完成的工作如下：1、基于FPGA技术及CompcatPCI技术，设计并成功搭建了一套数字化电阻层析成像系统。该系统采用工业标准CompactPCI总线协议，具有稳定性强，传输速度快，可扩展性强等优点。基于FPGA技术实现了数字解调等数字信号处理方法，提高了电阻层析成像系统的数据采集速度。成像实验测试结果证明，该数字化电阻层析成像系统具有1300幅/秒以上的采集速度，60分贝以上的信噪比和良好的成像性能，能够满足导电物质为连续相的大多数工况的检测要求。2、基于电容法测量原理，提出了一种基于多段电极的轴向步进法激励模式。仿真结果证明，在该模式下，系统测试得到的数据进行简单的处理后，其特征能够直接进行流型识别，不同液位层流的数据也具有明显的特征。该方法主要考察两相流体容性信息在由局部测量到全局测量过程中的信息响应特征。3、基于电容法测量原理，开发了可应用于环形流通区域中两相流的可视化测量的环域局部聚焦成像传感器。传感器的灵敏度分析和仿真成像结果表明，该传感器具有良好的灵敏度；通过传感器的测量数据，无需进行复杂的成像算法，可直接进行环域两相流分布的成像，提供了一种针对环域流通工况下两相流的可视化测试方法。4、利用Wire-Mesh传感器和超快X射线成像传感器进行了垂直上升管道气液两相流的泡状流和弹状流的实验。对试验数据进行处理分析，提取出截面相含率的径向分布，气相速度的径向分布和气泡大小分布等特征。实验分析结果证明，利用Wire-Mesh传感器和超快X射线成像传感器，在测量流体流动瞬时过程，具有较高的空间分辨率和时间分辨率，提供了一种测量快速流动两相流瞬态参数测量的可行性方法。通过该两种传感器图像数据提取的气相含率径向分布具有很高的一致性，偏差在4%以内；利用相关算法能够计算出气相速度径向分布；在得到气相截面含率和气相速度后，可以进行气泡大小计算，最终得到气泡大小分布情况，结果显示，在测量气泡大小分布时，在泡状流流型下，两种传感器能够得到非常一致的结果。更多还原

【Abstract】 The two/multi phase flow process is not only frequently encountered in natureand human being life, but also occurs widely in the energy, petroleum, chemical,metallurgical, refrigeration, aerospace, pharmaceutical, food and other modernindustrial processes. Measuring the process parameters of the two/multi phase flow isnot only very important to the development of the national economy, but also of greatsignificance to human resources being efficiently used. However, because of thedifferent flow characteristics and complicated instantaneous change interface betweentwo phases, precise measurement of the process parameters of two phase flow hasalways been a hotspot and difficult point in scientific research and industryapplication. Therefore, the purpose of this research is, on the basis of the conceptionof visualization measurement of multiphase flow, to investigate and analyze the mainvisualization measurement methods, especially tomography techniques, and todevelop new visualization measurement sensors for measuring and analyzingmultiphase flow. The research has been conducted by four steps as follows:1. New digital electrical resistance tomography system based on FPGA andCompactPCI industry standard bus has been built. By using the CompactPCI industrystandard bus protocol, the new system has the advantages of excellent operationalstability, high-speed data transportation, good extended performance, etc. Because ofthe application of FPGA chips, the digital demodulation and other signal digitalmodules have easily been realized, hence the speed of the data acquisition system hasbeen improved substantially. The imaging experiment result showed that the systemhad a high data acquisition speed which was above1300frames per second, a signalto noise ratio which was above60dB and an outstanding image reconstructionperformance. The new system could meet the measurement needs of most industrialprocesses with continuous conductive materials.2. The axial step exciting method of segmented electrodes based on thecapacitance measurement principle has been developed. The simulation experimentsproved that the characteristics of the processed dataset obtained by the excitingmethod could directly identify the flow pattern. In addition, the data characteristics ofstratified flows with different liquid levels proved to be very obvious. The method is mainly used to investigate the response of the capacitance materials whenmeasurement fields are extended from the local to the global.3. Based on the electrical capacitance measurement principle, an annular fieldfocusing capacitance sensor has been developed. The sensor has been used for thevisualization of two phase flows in the annular flow field. The performance analysisof the sensor showed good sensitivity. The imaging simulation proved that the signalof the sensors could be used to obtain images of the two phase distribution in theannular flow field directly without any complicated imaging reconstruction algorithm.To sum up, a visualization method for the two phase flow in an annular pipe has beenestablished.4. Based on the combination of the Wire-Mesh and ultra fast X-ray tomographysensors, the co-current vertical gas-liquid flow experiments, especially the bubbly andslug flow measurement experiments, have been executed. After processing andanalyzing the tomography data, the radial cross-section gas fraction and velocity aswell as the bubble size distribution of the two phase flows have been extracted andcalculated. The experiment results showed that, because of the high space and timeresolution of the sensors, the combination of the wire-mesh sensor and ultra fast X-raytomography sensor could provide an effective method for measuring the dynamicparameters of the high-speed transient two-phase flow. The maximum deviation of thegas fraction profiles was4%, which indicated very good agreement. The gas phasevelocity radial profile could be evaluated by using the cross-correlation of the gasfraction from the two sensors. With the gas fraction and velocity data, the bubblescould be identified and the bubble size, bubble equivalent diameter and bubble sizedistribution could be extracted. When measuring bubbly flow using the two sensors,the bubble size distributions indicated good agreement.更多还原