Numerical Study On Gas-Solid Flow Based On TFM-DEM Hybrid Model

This thesis aims at the gas-solid two-phase TFM-DEM hybrid mode, and takes gas-solid flow process in the coal beneficiation fluidized bed(CBFB) and the furnace of fluidized bed, respectively, as objects of research. The selection of parameters and sub-model in the hybrid model is investigated and the correlation of the concentration and velocity distribution of the two solid phase, namely TFM phase and DEM phase, isexplored.In the gas-solid flow of the coal beneficiation fluidized bed, different diameters of coal/gangue particles are investigated and the existence of effective particle diameter in this apparatus is validated. The coal back mixing phenomenon due to the drag effect of the rising bubble in the bed is captured from the particle level, and the time to reach balance in different diameters of coal/gangue particle is compared. Based on the experimental data, different parameters and sub-model in the hybrid model are investigated, including the gas-solid drag model(Syamlal O’Brien model, Wen-Yu model and Gidaspow model), boundary condition at the wallsides(gas/solid free slip and none slip) and the multi-phases in diameter and density in terms of the TFM phase.In the cold gas-solid flow in the furnace of fluidized bed, the solid particles investigated are composed of two different diameters. After the verification of the experimental data, the correlation of instantaneous and time-averaged velocity and concentration distribution of TFM phase and DEM phase in specific area is studied. As for the velocity distribution, the differences of the axial and radial velocity between the particles of different sizes are discussed. And the influence of particle diameter, area selected and the ratio of DEM phase/TFM phase on the correlation of velocity, both instantaneous and time-averaged, are studied; In terms of the concentration distribution, consistency and uniformity of the concentration distribution in specific area of two phases(TFM and DEM) is investigated. The parameter-ratio of concentration in grid level is introduced to cast light on the relationship of the concentration distribution of the two phases: the mean value of the ratio of concentration reflects the consistency and the standard deviation means uniformity. As it is discussed in the velocity distribution, the impact of the particle diameter, area selected and ratio of DEM phase/TFM phase on the correlation of concentration distribution are in the scope of this investigation.The thesis also is engaged in the automation of the pre-and-post processing of the hybrid model, including the DEM phase particle initiation, DEM phase data batch importing, DEM data(velocity and position) extraction in specific area and the comparison with the TFM phase as well, which not only provide the follow-up researchers with great convenience in the aspects of initial configuration and data visualization in hybrid model, but the referable ideas in post-processing as well.