Simulation Research On Flow Characteristics Of Fluidized Bed And Cyclone Separator Based On OpenFOMA

The fluidized bed has strong heat and mass transfer characteristics.As a gas-solid separation device with simple structure and mature technology,the cyclone separator and fluidized are widely used in power,petrochemical and other industrial applications.With the development of CFD(computation fluid dynamic)technology,CFD is widely used in the research of gas-solid two-phase flow systems.Using mathematical models to model and calculate physical problems is the core of CFD technology.Using CFD technology to carry out accurate mathematical modeling of fluidized bed and cyclone separator,and then realize accurate simulation of them.It is of great significance to the industrial application of fluidized bed and cyclone separators.The main research contents of this paper are as follows:Firstly,the drag coefficient characteristics of Symal OBrien drag force model,Gidapow drag force model and modified Symal Obrien drag force model considering the effect of particle agglomeration are summarized and analyzed.The drag force model is selected according to the particle concentration partition,and the improved partition drag force model is proposed.The drag coefficient characteristic curve of the partitioned zone drag force model is consistent with the drag coefficient characteristic curve obtained by the direct numerical simulation of DNS.Secondly,the fluidized bed simulation results verify the zone drag force model.The simulation results of fluidized bed flow characteristics show that: The bed expansion rate and pressure drop obtained by the zoned drag model are in good agreement with the experimental results,and the errors of the bed expansion rate and pressure drop simulated by the zoned drag model are smaller than those of other drag models;The zoned drag model can capture the initial flow structure of the fluidized bed,the formation of bubbles to the breaking stage,and the "ringcore" structure circulating in the fluidized bed.Finally,the flow characteristics of the cyclone separator are numerically simulated based on the method of large eddy simulation coupled with MP-PIC.The turbulence model of the gas phase adopts large eddy simulation,the particle phase adopts the MP-PIC method,and the mutual coupling between the particle phase and the gas phase in the cyclone separator is considered.The flow characteristics of the cyclone separator are analyzed with axial velocity,tangential velocity,static pressure distribution,rotation center offset,and particle flow characteristics.The results show that the prediction results of the inlet and outlet pressure drop by the large eddy simulation coupled with the MP-PIC method are consistent with the experimental value,which verifies the applicability of the large eddy simulation coupled with the MP-PIC method.The tangential velocity and axial velocity of the cyclone separator present "M"-shaped and inverted "V"-shaped distributions respectively;the static pressure has a large drop gradient along the radial direction;the influence of the inlet wind speed on the tangential velocity,axial velocity and pressure distribution is analyzed.The coordinate position and eccentricity of the center of rotation on the cross section prove that the internal flow field of the cyclone separator has a certain asymmetry;the velocity vector diagram of the particles shows the flow law of the particles;the residence time of the particles on the top of the cyclone shows the "top ash ring" phenomenon of the separator.