不同进气方式的流化床内颗粒混合特性的数值模拟

Numerical Simulation on Particle Mixing Characteristics in a Fluidized Bed Under Different Intake Modes

为了从微观角度分析不同进气方式的流化床内颗粒的运动机制,利用计算流体力学与离散单元法相结合的方法,采用Gidaspow曳力模型实现气固两相间的耦合,对不同进气方式的流化床进行数值模拟,采用Lacey混合指数等对颗粒的混合状态进行定性和定量分析,并探讨了气体速度参量对混合特性的影响。结果表明:喷动流化床内颗粒混合特性受喷口气速和流化气速的综合作用;存在喷动气的工况,其最终混合状态比均匀进气的工况好;在存在喷动气的前提下,引入流化气会导致床体的死区变小,且流化气速越高,死区越小;在特定的模拟工况下,存在一个最佳流化气速,使得颗粒混合质量最好。

To analyze the movement mechanism of particles in a fluidized bed under different intake modes from micro perspectives, numerical simulations were conducted on the motion state in the fluidized bed using computational fluid dynamics and discrete element method, while the Gidaspow drag force model was adopted to achieve the coupling of gas-solid two phases. The mixing state of the particles was qualitatively and quantitatively analyzed by the Lacey mixing index, and the influence of velocity parameters on the mixing characteristics was discussed. Results show that the particle mixing effectiveness in the spouted fluidized bed is affected by the velocity of both the spout and background gas;the final mixing state with spout gas is better than that with uniform gas intake;introducing the background gas in the presence of spout gas will make the dead zone become smaller, and the larger the background gas velocity is, the smaller the dead zone will be. In particular simulation conditions, there exists an optimal background gas velocity, when the particles are mixed most adequately in the bed.