颗粒团影响循环流化床内气固流场的PIV测试

PIV Measurement on the Effect of Clusters on the Gas-solid Flow Pattern in a Circulating Fluidized Bed Riser

利用自行构建的可用于循环流化床内流动特性测试的PIV系统对一台高4m截面200mm×200mm的冷态循环流化床进行了PIV测试研究。采用适合于较高粒子浓度的互相关处理MQD方法来处理PIV图像,获得了循环流化床内颗粒团运动对流场内颗粒速度的动态影响。结果表明:(1)颗粒团可能出现在流场截面内的各个位置,形状和速度都随时间的变化而变化;(2)颗粒团对床内的气固流动行为有较大的影响。只要有颗粒团出现,无论它的流动方向与主流颗粒的流动方向异同,气流和分散固粒都受到它的驱动向不同方向运动;(3)在颗粒团增长过程中,随着时间的增加,流场截面内颗粒平均速度虽然有波动,但总的变化趋势是增加的。

A special PIV (Particle Image Velocimetry) has been constructed for measurements on the effect of clusters on the gas-solid flow pattern in a circulating fluidized bed riser with 4m in height and 200 mm × 200 mm in cross-section. The velocity vector flow fields of particles varying with the time are obtained from the captured images by using the MQD cross-correlation arithmetic which may be used to high-density particles. The main effects of cluster on the velocity field of the solid particles in the circulating fluidized bed riser are obtained as following: (l) the clusters may appear in the different position along the cross-section in the flow field, and their shape and velocity vary with time; (2) the clusters have a strong effects on the gas-solid flow pattern. The particles near in the clusters are driven to move in different direction by the moved clusters; (3) with growing of the clusters, the average velocity of the particles in the related flow field increases in fluctuation.