Thermal-Flow Modeling of Fluidized-Bed combustor/Reactor (Real-Time Radiographic Quantitative Flow Visualizaiton of High Temperature Fluidized-Bed Model)

为了建立高温流化床热工水力学的理论基础，利用中子和X射线照相系统进行了实验研究。实验温度范围为室温至约450 ℃。在室温实验中，利用中子照相技术定量测量了床层中的空隙率及其波动特性、床层物料流动与传热的相互关系、床层中气泡的行为（包括气泡上升速度和气泡尺寸）、床层中二元混合物的行为、固体颗粒和气泡周围的流场。在实验数据的基础上，利用漂移流模型对气泡上升速度和含气率进行了关联。考虑管束排列方式对气泡尺寸的影响，气泡尺寸与实验值有较好的关联性，分离行为也是流化床设计的重要因素。然后用中子照相法对二元混合物流化床进行了可视化。利用X射线照相系统进行了高温实验研究。得到了最小流化速度、气泡运动、含气率分布和脉动特性。在高温下，在床层的整个区域中观察到气泡，而在室温下，只有有限的部分被气泡搅动。其他特征参数也通过漂移通量模型进行了很好的关联。

Aiming to construct fundamental basis of the thermal hydraulics in gas-fluidized bed operated at high temperature, experimental investigations have been conducted using the neutron and X-ray radiography systems. The experimental temperature range was from room temperature to about 450 degree C. For the room temperature experiment, the neutron radiography was used for quantitative measurement of void fraction and its fluctuation characteristics, interrelationship between the flow of bed materials and the heat transfer, bubble behavior in the bed including bubble rise velocity and bubble size, behavior of binary mixture in the bed, flow field around solid particles and bubbles. On the basis of the experimental data, the bubble rise velocity and the void fraction have been well correlated by the use of drift-fiux model. The observed bubble size was also well correlated taking into account the effect of tube bank arrangement.Segregation behavior is also an important factor for the design of fluidized bed. Then the fluidized-bed with binary mixture was visualized using neutron radiography. The dynamic behavior was well visualized and the qualitative and quantitative information useful in understanding the segregation were obtained.High temperature experiment was conducted using X-ray radiography system. Theh the minimum fluidization velocity, bubble movement, void fraction distribution and the fluctuation characteristics were obtained. At high temperature, bubbles were observed in the whole area of the bed, while only a limited part was agitated by the bubbles at room temperature. The other characteristics parameters were well correlated by means of drift-flux model as well.