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"A Study on Instability Phenomena in Liquid Metal Natural Convection under a Magnetic Field."

“磁场下液态金属自然对流不稳定现象的研究”。

基本信息

批准号：
06808048
负责人：
TAKENAKA Nobuyuki
金额：
$ 1.28万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06808048/
关键词：
LIQUID METAL MAGNETIC FIELD FUSION REACTOR BLANKET FLOW VISUALIZATION NEUTRON RADIOGRAPHY TRACER METHOD DYE INJECTION METHOD 不安定現象自然対流可視化

项目摘要

A use of liquid metals as the blanket material in a magnetic confined fusion nuclear reactor has many advantages on the high heat transfer characteristics and the tritium breeding in the blanket designs. However, the MHD pressure drop in the blanket is high due to the high electrical conductivity of the liquid metals and extremely high pump power is required when the blanket is cooled by a sigle phase liquid metal flow. To avoid the high pump power, many conceptual designs on the blanket have been proposed. There are many problems which have not been solved on thermal hydraulcs of liquid metals under magnetic fields, especially flow characteristics have not been clarified since liquid metals are opaque to optical rays. It has been generally reported that the heat transfer is suppressed by the applied magnetic fields as the flow is suppressed by Lorents force. While, a few papers reported that large temperature fluctuation was occured and the heat transfer was augmentated in natural and … More forced convections by the applied magnetic field. These phenomena have not been clarified yet since the flow visualization is difficult.This study was started to clarify the heat transfer augmentation mechanism, which has not been well understood generally, by visualizing the flow using neutron radiography. Neutron radiography is suitable to visualize the liquid metal flows by a tracer and a dye-injection method.In this report, the liquid metal flow visualizations in natural convection and under a magnetic field were carried out and following results were obtained.1) It was shown that the flow of lead-bismuth eutectics was visualized by a tracer and a dye-injection method.2) Lead-bismuth-gas two-phase flow in a container under a horizontal magnetic field was visualized and the void fraction and the flow field measurements were carried out. The applied magnetic field up to 2500 gauss affected the void fraction distribution a little but suppressed the flow. It was shown that flow phenomena in a liquid metal in the presence of a magnetic field was visualized bu nentron radiography.3) Flow vector fields in lead-bismuth in a container could be obtained by a tracer method using a correlation method when the tracer sizes was closed to the image element size in the image processing. Less

采用液态金属作为磁约束聚变反应堆包层材料，在包层设计中具有高传热特性和氚增殖等诸多优点。然而，由于液态金属的高导电性，毯层中的MHD压降很高，并且当毯层被单相液态金属流冷却时，需要极高的泵功率。为了避免高泵功率，人们提出了许多关于毯层的概念设计。在磁场作用下液态金属的热工学研究中，有许多问题尚未得到解决，特别是由于液态金属对光线不透明，其流动特性尚未明确。一般报道，在流体流动受到洛伦特力的抑制的同时，外加磁场也抑制了传热。然而，也有少数论文报道了在自然对流和外加磁场更多的强迫对流中发生较大的温度波动和强化换热。由于流动可视化的困难，这些现象尚未得到澄清。本研究的目的是通过中子射线成像技术对流动进行可视化观察，以阐明传热增强机制，这一机制目前还没有得到很好的理解。中子射线照相适合于用示踪剂和染料注入法观察液态金属的流动。在本报告中，对自然对流和磁场作用下的液态金属流动进行了可视化，得到了以下结果：1)用示踪剂和染料注入法对铅铋共晶的流动进行了可视化。2)观察了水平磁场作用下容器内铅-铋-气两相流动，并进行了空隙率和流场测量。2500高斯的外加磁场对孔隙率分布影响不大，但对流动有抑制作用。结果表明，在磁场作用下液态金属的流动现象可以用中子射线照相法直观地观察到。3)在图像处理中，当示踪剂尺寸与图像元素尺寸接近时，示踪剂方法可采用相关法获得容器内铅铋的流矢量场。少