基于DEM模拟气固循环流化床提升管内颗粒聚团特性

采用CFD-DEM的方法对气固循环流化床提升管内的气固流动特性进行模拟，建立了基于图像处理的分析颗粒聚团的方法，重点研究了颗粒聚团在床层内的整体分布以及颗粒聚团的特性，包括颗粒聚团的倾角、球形度以及长短轴比的概率密度分布以及它们在床层内的轴向和径向上的分布特性。研究结果表明，聚团在床层内的分布较宽，较小的聚团居多，边壁区域附近易形成较大的聚团。聚团的数目沿床层高度方向先增加后减少。聚团倾向于以偏离球形聚团、较大的倾角形式存在，其长短轴比值在2～4之间。

DEM simulation of particle clustering characteristics in gas-solid CFB risers

Gas-solid flow in CFB riser was simulated by a combined approach of computational fluid dynamics (CFD) and discrete element method (DEM). A new cluster analysis method based on image calibration and processing technique was developed to obtain overall, axial and radial distributions of clusters in fluidized beds as well as cluster characteristics in terms of inclination angle, degree of sphericity, and aspect ratio of long over short axis. The clusters showed a wide distribution with mainly small clusters and large clusters formed in the regions near the wall. Along the height direction of the riser, the amount of clusters first increased and then gradually decreased. In addition, clusters were most likely to exist in the form of non-spherical aggregates with large inclination angle and aspect ratio between 2 and 4.