Abstract

Particle clusters play a significant role in gas-solid flow systems. Cluster motions are experimentally studied in a multistage circulating fluidized bed. Cluster characteristics including spatial distribution, breakup process, and size are discussed. Dynamic parameters (frequency, duration, and time fraction) are also obtained to characterize cluster behavior by employing the digital image analysis method. The results show that cluster motions gradually weaken along radial and axial directions in the enlarged section. Cluster breakup tends to increase in the enlarged section due to gas turbulence and cluster collision. Cluster frequency, duration, and time fraction decrease with the increasing gas velocity but increase with the increasing solid mass flux. Compared with the conventional riser, cluster size reduces in the enlarged section. Furthermore, the analysis results from cluster dynamic parameters indicate that cluster motions are restricted under the low solid loading.

摘要

粒子簇在气固流动系统中发挥着重要作用。在多级循环流化床中对簇运动进行了实验研究。讨论了包括空间分布、分解过程和大小在内的集群特征。通过采用数字图像分析方法，还获得了动态参数（频率、持续时间和时间分数）来表征集群行为。结果表明，在放大剖面中，团簇运动沿径向和轴向方向逐渐减弱。由于气体湍流和团簇碰撞，团簇破裂在扩大部分趋于增加。簇频率、持续时间和时间分数随着气体速度的增加而减小，但随着固体质量通量的增加而增加。与传统立管相比，扩大部分的簇尺寸减小。