基于CFD-DEM法的矩形喷动床与柱锥形喷动床颗粒喷动特性模拟

Simulation of Particle Behaviors in Rectangular and Cylindrical Spouted Beds Based on CFD-DEM Method

为进一步了解矩形喷动床的优缺点,采用离散元气固耦合法(CFD-DEM)对矩形喷动床中小麦颗粒的喷动特性及混合过程进行数值模拟,并通过分析单颗粒循环时间、混合指数、床层压降、颗粒速度等与传统柱锥形喷动床进行对比.结果表明:u s=1.1 u ms时,矩形喷动床的平均单颗粒循环时间为1.9 s,柱锥形喷动床的单颗粒循环时间为1.7 s,相差较小.两种喷动床的颗粒混合时间均为2.8 s.相比柱锥形喷动床,矩形喷动床内的压力略大,尤其在喷动床棱角处气体压力较大,从而导致矩形喷动床在棱角处的颗粒运动随机性较差.因此,矩形喷动床与柱锥形喷动床的喷动特性总体上具有较好的一致性,但矩形喷动床在结构设计时要尽可能改善棱角处颗粒运动问题.

To further understand the advantages and disadvantages of rectangular spouted bed,the coupling method CFD(computational fluid dynamics)-DEM(discrete element method)was used to simulate the spouting and mixing process of wheat particles in a rectangular spouted bed.The cycle time of single particles,mixed index,bed pressure drop and particle velocity were analyzed,and compared with those in a conical-cylindrical spouted bed.The results indicated that the average circulation time of a single particle was 1.9 s in the rectangular spouted bed and 1.7 s in the conical-cylindrical spouted bed at u s=1.1 u ms.The mixing time of particles in the rectangular and conical-cylindrical spouted beds were both 2.8 s.The pressure in the rectangular spouted bed was a little higher than that in the conical-cylindrical spouted bed,especially in the corner of the rectangular spouted bed,whcih led to bad random motion of particles in the corner of the rectangular spouted bed.Therefore,although the spouting behavior and mixing process of particles were basically the same,the random motion at the corner of the rectangular spouted bed should be taken into account in structural design.