异质柱形颗粒与球形颗粒混合流动特性的CFD-DEM数值模拟分析

Simulation study on characteristics of cylinder-shaped particles and sphere-shaped particles flow

针对成型生物质颗粒与流化介质在气固流化床中的混合流动过程,采用数值模拟对该过程进行描述和分析。应用Fortran语言编程,构建复杂组分的三维气固两相流模型,在介观尺度下对流化床中异质异形颗粒的混合流动模拟问题进行研究。在欧拉和拉格朗日框架下,分别采用不同方法构造柱形颗粒:在CFD模型中,采用虚拟小球法描述柱形颗粒,引入体积分数改进曳力系数公式;在DEM部分,采用球元叠加法构造柱形颗粒,引入软球模型计算颗粒间的碰撞力。基于上述方法,模拟表观气速分别为1.0 m/s和2.0 m/s时的柱形生物质与石英砂混合流动的物理过程,并将模拟结果与试验结果进行对比。研究结果表明:该方法能较好地模拟在鼓泡床状态下异质柱形颗粒与球形颗粒混合流动的过程。

A numerical simulation method was used to describe and analyze the mixing flow of biomass particle and quartz sands in gas-solid fluidized bed. Three-dimensional gas-solid flow models were constructed to simulate the mixed flow of heterogeneous particles in mesoscopic scale. The integrated model was built in an Eulerian-Lagrangian approach and the constructed methods of cylinder-shaped particles were different when it came to different numerical methods. Each cylinder-shaped particle was constructed as an agglomerate of fictitious small particles in CFD part, while in DEM method, cylinder-shaped particles were built by multi-sphere method, in which small sphere element merged with each other. Soft sphere model was used to get the connect force between particles. The total connect force of cylinder-shaped particle was calculated as the sum of the small sphere particles＇ forces. Two models with different superficial gas velocities（1.0 m/s and 2.0 m/s） were built and the results of simulation were compared with the experimental results. The results show that the present work provides an effective approach to simulation the flow of two component particles.