Experiential investigation of cluster velocity and slip velocity in the CFB riser

Cluster velocity and slip velocity are the important features of cluster hydrodynamics and the statistical analysis was carried out based on the moving direct of the clusters in this work. Lagrange approach was employed to compute the velocity of the clusters which were captured by a high speed camera in a thin 2D fluidized bed. The experimental research results show that cluster velocity can be accurately computed by the Lagrange method. The velocity of the up-moving clusters is slightly greater than that of down-moving cluster. Cluster velocity increases with increasing the gas velocity and most of cluster velocity ranges from -2 to 2 m/s. The smaller clusters have greater cluster velocity and the larger cluster have smaller cluster velocity. Most of the down-moving clusters are present in the near wall region, and the down-moving clusters are about 60-70% of the total clusters. The x-component of cluster velocity is low, ranging from 0.3 to 0.6 m/s. Cluster slip velocity reveals the interaction between the cluster and its surrounding gas, and is an essential parameter of the structure-based model in the gas-solid fluidized bed. The distribution of cluster slip velocity is wider than that of cluster velocity, and they have the similar various trends. A small amount of slip velocity is negative, about 20-30%, for the up-moving clusters, while all of slip velocity is positive for down-moving clusters. (C) 2020 Published by Elsevier B.V.