青刀豆一般采用流化床装置进行速冻.为了解决其床层堵塞和聚集不良的问题,进一步提高青刀豆的混合效率,课题组建立了三维混合脉动流化床模型,将计算流体力学与离散单元法(computational fluid dynamics-discrete element method,CFD-DEM)相结合,探究1,2,4 和8Hz4 种不同频率的脉动进口风速下青刀豆颗粒的流化混合情况.仿真结果表明:脉动流化床对于青刀豆颗粒混合具有一定改善作用,青刀豆颗粒的轴向混合强于径向混合,4 Hz时颗粒混合标准偏差值最小;当进口风速的频率接近颗粒的自主振动频率时,床层膨胀最明显,出现类似"共振"的现象;2 Hz时颗粒径向、轴向混合效果最佳,频率过大或过小对于流态化增强效果不明显.
Numerical Simulation of Mixing Characteristics of Green Bean Particles in Pulsating Fluidized Bed
Fluidized bed is used to realize the quick freeze of green beans.In order to solve the problems of bed blockage and poor aggregation,and further improve the mixing efficiency of green beans,a three-dimensional mixed pulsating fluidized bed model was established.The fluidized mixing of green bean particles was explored under four different frequencies of pulsating inlet wind speeds at 1,2,4,and 8 Hz,based on computational fluid dynamics-discrete element method(CFD-DEM).The simulation results show that pulsating fluidized bed can improve the mixing of green beans to a certain extend.Particle axial mixing is stronger than radial mixing,and the particle mixing standard deviation value is minimum at 4 Hz.When the inlet wind frequency is similar to the natural vibration frequency of the particles,bed expansion is the most obvious and appears the phenomenon of"resonance".The radial and axial mixing effect of particles is optimal at 2 Hz.Excessive or insufficient frequency has little effect on enhancing fluidization.
particle mixinggreen beans3D mixed pulsating fluidized bedCFD-DEM(Computational Fluid Dynamics-Discrete Element Method)vibration frequency
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