关键词: 提升管, 离散单元法, 计算流体力学, 不均匀性

Abstract: The gas-solids flow behavior in a two-dimensional riser was numerically simulated by combining computational fluid dynamics (CFD)and discrete element method (DEM).In particular,gas turbulence was investigated by standard k-ε two-equation model,and van der Waals force and rolling friction between particles were also considered.In the present study,the flow behavior of particles and gas was analyzed,distribution of particle concentration,velocity,granular temperature and gas velocity were obtained,and the effect of operating conditions on solids flow was also studied.The results indicated that particles flow showed significant non-uniformity in the riser,clustering was observed near the wall.The typical core-annulus flow structure with a dense phase near the wall and a dilute phase in the center was formed.In the vertical direction,it was divided into a dilute region in the upper zone and a dense region near the bottom in the riser.The results showed a certain amount of some backmixing of both particle and gas phase.Furthermore,it was demonstrated that particle velocity increased and particle concentration decreased with increasing superficial gas velocity,and particles had more non-uniform distributions.Larger solids mass flux led to more non-uniform solids distributions and higher particle concentration,while particle velocity was insensitive to change of solids mass flux.Simulated results were in qualitative agreement with experimental observations.

Key words: riser, discrete element method, computational fluid dynamics, heterogeneity