| Popis: |
Discharge behavior of powders is crucial for pharmaceuticals and other industrial branches. However, for small particle sizes, the influence of the surrounding fluid can lead to unsteady and unexpected mass flow rates. For detailed insight during powder discharge, a CFD-DEM study was carried out for a cohesive lactose powder. Firstly, calibration of DEM parameters was conducted with nanoindentation, free fall experiments, friction tests and angle of repose measurements. Further validation was achieved by shear tests and powder rheometry. Subsequently, experimental and numerical discharge procedures were performed for a wedge-shaped silo with varying configurations. Bed expansion inside the silo led to a vacuum in the hopper, which reduced the discharge rate. The mass flow rate in experiments and CFD-DEM simulations showed only low sensitivity to hopper angle variation. For flat hopper angles, relative air flow extended horizontally to stagnant zones, which acted as a permeable hopper and reduced the air impairment. |
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