Fluidization characteristics of magnetic particles and determination of stable fluidization zone in magnetically fluidized bed

To determine and calculate the stable fluidization zone in a magnetically fluidized bed, the fluidization characteristics of magnetic particles are investigated. Four kinds of magnetic particles with different average diameters, ranging from 231 to 512 μm, are fluidized in the presence of magnetic fields with specified values of the intensity in the range of zero to 7330 A/m, and the particle fluidization curves are plotted. For marking the stable fluidization zone in the curves, the minimum bubbling velocities of particles are measured by the pressure-drop fluctuation. Based on the fluidization curves, the influences of the average particle diameter and magnetic field intensity on the zone are analyzed and discussed. A correlation to determine the stable fluidization zone is derived from the experimental data, using three dimensionless numbers, i. e., the ratio of magnetic potential to gravity potential, the Reynolds number and the Archimedes number. Compared with available data reported, it is shown that the correlation is more simplified to predict relative parameters for the bed operating in the state of stable fluidization under reasonable conditions.

1000 MW汽轮发电机组润滑油管线压力脉动分析

某压水堆核电厂汽轮发电机润滑油管线存在压力脉动和异常振动。通过系统工况分析的方法对影响润滑油管线压力的主要因素进行了分析和验证;并采用角动量守恒分析方法对额定工况下主油泵出口止回阀的最小稳定介质流速进行了计算,对阀门在低流速下的流动特性及阻力系数的变化进行了分析。结果表明:旋启式止回阀阀瓣在低流速下不完全开启,受上游流体扰动影响失稳振荡,进而造成阀门阻力系数的变化是汽轮发电机润滑油管线压力脉动的原因;因此,需要在系统设计和设备选型阶段提出止回阀稳定在全开状态下的最小流速要求,在确定最小流速的基础上核算相应的流量系数的改进方案。分析方法适用于解决因止回阀选型及管道布置引起的系统压力脉动。