| The solid fluidization technology is used widely as an important fluid-solid physical operation. Fluidized bed is the typical technology of multi-phase fluidization. Because the multi-phase behavior is the chaos and nonlinear processes, the further information can be achieved by analyzing the variety of parameters in fluidized bed, such as pressure drop, local phase concentration, particle velocity, granular temperature, bubble size, and so on. The computational fluid dynamics (CFD) method has been interested over the past years by many researchers, because it can obtain the data which is difficult for experiment, optimize experimental apparatus, modify and testify numerical models, reduce experimental charge, and so on.The best perforated ratio of distributor was determined using CFD code FLUENT 6.2 combining experimental data measured in our lab, firstly. Then the parameters of local solid concentration, bed pressure drop, et al, were measured at the condition of the best perforated ratio, and they were compared with the simulation data to select the suite numerical models, modify and validate models.Firstly, the parameters of bed pressure drop, distributor pressure drop, the instantaneous evolution of bubbles and profile of radial solid holdups adopted three perforated ratios of distributors (φ=0.46, 0.86, 1.10%) were simulated. The results were shown that the distributor pressure drop decreased with increasing perforated ratios and decreasing the superficial gas velocity. The global solid holdup was decreased from the wall to center region, and it had parabolic concentration profile under pressure–driven force for different perforated ratios of distributors investigated. The fluctuation of pressure drop increased and fluidization quality decreased with increasing perforated ratios of distributors. The distributor of perforated ratio 0.46% was adopted in the present work by considering the parameters above.Secondly, appropriate setting of geometrical model, grid, time step, particle restitution coefficient and other boundary condition (UG was above 0.04 m·s-1) were obtained to decrease calculation error by investigating the parameters effects on the calculation results. At the condition of above, Syamlal-O'Brien,Gidaspow and Wen and Yu drag models were investigated. The most appropriate drag model in this work was Syamlal-O'Brien by investigating the effect on the profile of solid concentration, gas-solid velocities and pressure drop. In this work, a model used to modify Syamlal-O'Brien drag model based on the experimental conditions, was established, and the discrepancy between the simulation results and experimental data was decreased.Thirdly, fluidized behaviors of acoustic fluidized bed were investigated. By analyzing the particle vibration velocity and solid momentum caused by sound assistance, an acoustic model was also established and the original solid momentum equation was modified. Under modifications for drag model and momentum equation conditions, the radial particle volume fraction, axial root-mean-square (RMS) of bed pressure drop, granular temperature, and particle velocity in gas–solid acoustic fluidized bed were simulated using CFD code FLUENT 6.2. The numerical simulation results were validated by experimental measurements. It was showed that simulation values were in reasonable agreement with the experimental data in certain errors and the acoustic model established in this work can describe correctly the fluid dynamic behaviors. However, it also has discrepancy with the literatures results, so the acoustic model established in this work is needed to be investigated and modified further. |
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