Study on Visualization of Fluid Phenomena Using Neutron Radiography Technique

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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