Kinetic Theory Based CFD Simulation and Experiments of Dynamic Characteristics In Gas-Solid Fluidized Bed

A two-dimensional Eulerian-Eulerian model integrating the kinetic theory of granular flow is used to simulate the bubble and particle dynamic characteristics in a gas-solid fluidized bed. Experiments of pressure fluctuation and acoustic energy (AE) signals in the fluidized bed are measured to validate the CFD simulation. The simulated results show that the Syamlal-O’Brien drag model predicts more reasonable results than the Gidaspow drag model. The power spectrum of pressure and voidage fluctuation is analyzed to associate with bubble motion. As the bed height increases, the simulated and experimental main frequency of pressure fluctuation first stays constant and then rises sharply, while the simulated main frequency and amplitude of voidage fluctuation both increase. The bubblelike granular temperature calculated from turbulent energy of solid phase has the same variation tendency compared to the experimental AE energy generated by particle impact on the wall. According to this variation tendency, the fluidized bed can be divided into stagnant zone, main circulation zone and freeboard. The computed vertical turbulent energy of particles is stronger in wall region and dense region of the fluidized bed. Based on the cascade theory of turbulence, the vertical turbulent energy spectrum of particles is divided into energy-containing range, inertial range and dissipation range. In inertial range at high frequency, the Levy-Kolmogorov law is obeyed. The flatness factors of particle fluctuation velocity and 8 scales wavelet decomposition coefficients of particle fluctuation velocity are calculated to investigate the intensity of intermittence caused by coherent structures in the flow field. The intermittence in dissipation range is much stronger than that in energy-containing and inertial range, and reinforces rapidly as the radial distance and bed height increase.