FROM DISCRETE PARTICLE MODEL TO A CONTINUOUS MODEL OF GELDART A PARTICLES

摘要

Areliable description of dense gas-solid two-phase flows of Geldart A particles in gas-fluidized beds at life-size scale is of great practical importance in process industries.The classical two-fluid model,based on the kinetic theory of granular flows (KTGF),provides a very promising theoretical framework for predicting large-scale gas-solid two-phase flows.However,thus far the two fluid model has not been successful in describing gas-solid flows of Geldart A particles.As the kinetic theory was originally developed for cohesiveless particles,it is essential to check if the theory can still work for Geldart A particles,which are slightly cohesive.In this research,a soft-sphere discrete particle model (DPM) is used to study the detailed particle-particle interactions in periodic boundary domains,where interparticle van der Waals forces are taken into account,with no gas phase present.In our simulations,we (1) compare the results for both the hard-sphere and the soft-sphere discrete particle model for cohesiveless particles,with the theoretical predictions obtained from the kinetic theory of granular flows,and (2) study the effect of the cohesive forces in the soft-sphere model and explore a way to modify the current kinetic theory according to the soft-sphere DPM simulation results.The information obtained from these simulations can be further incorporated into the KTGF based two-fluid model.