Study on Visualization of Fluid Phenomena Using Neutron Radiography Technique

本研究项目作为京都大学研究堆研究所和密歇根大学凤凰纪念实验室的联合研究项目，于1990财年启动，1992财年完成。该项目的目的是探讨中子射线成像技术应用于流动可视化的可行性。特别是作为中子应用技术之一的电子成像技术，由于能产生实时的流动图像，在金属管道中流体现象的可视化方面具有优势。因此，本研究将电子成像和图像处理技术应用于金属管道、喷嘴或多孔介质中流体现象的可视化和测量。实验中使用的测试样品为矩形管道和圆管中的空气-水流动、圆管中的沸腾两相流、水层厚度与灰度的校准样品、中子射线照相的ASTM标准样品、多孔介质中的木质金属和喷气发动机的燃料喷嘴。中子射线照相实验使用的设备如下：京都大学研究堆（KUR）、密歇根大学福特核反应堆（FNR）、日本原子能研究所JRR-3和NSRR。实验结果表明，电子成像和图像处理技术可用于气液两相流中空隙率的测量。利用图像处理技术，测量了窄矩形管和圆管中空气-水流动的空隙率。将图像处理得到的结果与传统探针法和理论方程得到的结果进行了比较，在测量误差范围内比较良好。但是，有人指出，为了获得良好的定量结果，需要对图像进行一些校正。因此，对几种图像校正的效果也进行了定量研究。研究结果表明，中子射线成像技术与图像处理技术相结合，不仅可以用于流体流动的可视化，还可以用于空隙率的测量。在本研究项目中，还论证了中子照相设备特性的差异。少

This research project started in FY 1990 as a joint research project between the research reactor Institute of Kyoto University and the Phoenix Memorial Laboratory of the University of Michigan, and finished in FY 1992. The purpose of the project is to investigate the feasibility of application of neutron radiography techniques to flow visualization. Particularly, electronic imaging which is one of application techniques of neutron has an advantage in visualizing fluid phenomena in a metallic duct, because it produces real-time images of the flow. Thus, in this study, electronic imaging and image processing techniques were applied to visualization and measurement of fluid phenomena in a metallic duct, nozzle or porous media.The test samples used in the experiments were air-water flows in rectangular ducts and round tubes, boiling two-phase flow in a round tube, a calibration sample for water-layer thickness vs gray level, ASTM standard sample for neutron radiography, wood metal in poro … More us media and a fuel nozzle of a jet-engine. The following facilities were used for neutron radiography experiment : Kyoto University Research Reactor (KUR), Ford Nuclear Reactor (FNR) of the University of Michigan, JRR-3 and NSRR of the Japan Atomic Energy Research Institute.From these experiments, it was revealed that electronic imaging and image processing techniques can be applied to measurement of void fraction of gas-liquid two-phase flow in addition to flow visualization. Using image processing technique, void fraction was measured for air-water flow in narrow rectangular ducts and round tubes. The results obtained by image processing were compared with the results obtained by the conventional probe method and the theoretical equation, and the comparison was good within measurement errors. It was pointed out, however, that some image corrections were needed to obtain good quantitative results. Therefore, the effect of several image corrections was also investigated quantitatively.As a result from this research project, it was revealed that neutron radiography can be applied not only to visualization of flow but also to the measurement of void fraction if combined with image processing technique. The difference of the characteristics of neutron radiography facilities was also demonstrated in this research project. Less