气固流化床内射流特性的研究

Jetting characteristics, i.e., jet formation, jet development, bubble size, transient gas velocity field, transient voidage and spectral power density of pressure signals, have been investigated numerically in a gassolid fluidized bed by using a new model proposed by Brandani and Zhang. Simulation is carried out for a twodimensional fluidized bed of size 1.6m ×0.3m equipped with a jet of 0.01m width in the central bottom of the bed. Sand belonging to Geldart B Group is selected as solid material, whose diameter and density are 500mm and 2660kg/m3, respectively. Transient results show that there exist obviously axialasymmetric behaviors for the jet above the nozzle, the bubble after the jet collapse as well as the gas velocity field and the voidage profile in the whole bed. The spectral power density of pressure signals, however, keeps almost equal at the axisymmetric positions in the jetting fluidized bed. The conclusions mentioned above imply that the simulated results in the half bed can represent the characteristics in the whole jetting fluidized bed for a stable operation in the commercial process. It is obviously different between the transient characteristics in the half bed and those in the whole bed.