Effect of secondary flow on gas-solid flow regimes in lifting elbows

The influence of the elbow lifting angle, airflow velocity and solid mass flow rate on particle flow regimes in lifting elbows has been characterized by an Euler-Lagrange four-way coupling method. The computational fluid dynamics (CFD) and discrete element method (DEM) were used for modeling in this paper. The effect of particle-wall collisions on particle motion was considered by adopting a modified Hertz-Mindlin (no slip) model. An orthogonal design method, to significantly reduce the number of the schemes, was used in this paper to discriminate the significant effects of three independent variables on pressure drops in the lifting elbow. The effect of the secondary flow on pressure drops, volume fractions and solid concentrations is discussed in the results section. The results indicated that the pressure drop increased gradually with increasing airflow velocity and solid mass flow rate; however, there was an optimal lifting angle at which the pressure drop was the smallest. For a 90 degrees elbow, the maximum collision region of the particles on the inner wall of the elbow depended only on the ratio of the radius of curvature to the diameter of the pipe and was independent of the air-flow velocity and particle concentration. (C) 2019 Elsevier B.V. All rights reserved.