Influence of collisional parameters for rough particles on simulation of a gas-fluidized bed using a two-fluid model

Abstract

Three physically realistic collisional parameters, the friction coefficient and the normal and tangential restitution coefficients, are used to characterize the rough particle collisions. The corresponding kinetic theory model and boundary conditions are incorporated into a two-fluid model to investigate the influence of these collisional parameters on the numerical simulation of a gas–solid bubbling fluidized bed. The simulated results reveal that coefficients of friction and normal restitution play important roles in the formation of heterogeneous structures in the bubbling bed, but their inherent effects on particle motion and bed expansion are quite different. In addition, the time-averaged gas–solid flow fields for different friction coefficients vary significantly, but those for different normal restitution coefficients exhibit very similar patterns. To achieve a better agreement with the experimental data, adjusting the friction coefficient is more effective than refining the normal restitution coefficient. The tangential restitution coefficient has relatively weak but non-monotonic effects on particle motion and bed expansion, and the flow fields for different tangential coefficients remain almost the same. Distinct effects of particle–particle and particle–wall collisions are also studied. For the overall fluidization behavior in a small-scale bubbling bed, the most crucial parameter is the friction coefficient for particle–wall collisions, followed by the normal restitution coefficient of particle–particle collision.