基于含晕气泡曳力模型的鼓泡床流化行为分析

Gas-solid bubbling fluidization system exhibits non-equilibrium, non-linear, and multiscale characteristics. In order to study the complex flow behavior inside the fluidized bed with clouded bubbles, this paper conducts numerical simulations on a three-dimensional bubbling fluidized bed using the clouded bubble-based multi-scale drag model. The variations of particle velocity and concentration at different positions are obtained. The time fluctuation sequences of particle concentration are processed by wavelet transformations. The particle fluctuation and bubble oscillation at the axial and radial positions are compared. The results indicate that the clouded bubble-based multiscale drag model can provide good predictions of flow behaviors in the bed. A core-annulus flow pattern where the particles rise in the center and fall along the walls is shown in the bed. Compared to the fluctuation of particle velocity, the fluctuation of particle volume fraction appears a higher frequency, which becomes more difficult to discern. The wavelet analysis reveals that the fluctuation intensities of both particle phase and bubble phase increase with bed height but gradually weaken towards the wall. The stronger fragmentation and aggregation behaviors of bubbles in a bubbling fluidized bed with Geldart A particles results in more uniform distribution of bubbles in the radial direction and smaller radial difference of energy fraction. Furthermore, increasing the inlet gas velocity enhances the non-uniformity of particle radial distribution and the energy fraction of particle and bubble fluctuation signals.