A wedge-shaped planar mass-flow hopper system was modelled using stress-field theory as found in the literature, The authors present governing equations for stress and velocity fields under a radial- flow assumption i...A wedge-shaped planar mass-flow hopper system was modelled using stress-field theory as found in the literature, The authors present governing equations for stress and velocity fields under a radial- flow assumption in a converging hopper. The velocity in the silo above the hopper is modelled as plug flow, Two set-ups are modelled, one where powder layers in the hopper are assumed to be flat, and the second in which the layers are heaped at some characteristic angle, The ejection times and residence-time distributions are calculated and presented for a range of heap angles. For realistic heap angles, the spread of the residence-time distribution decreases with increasing heap angle; in one case, the spread is halved to a well-defined limit. At this limit （the critical heap angle） the geometry of the hopper can be optimised to minimise the spread of the residence-time distribution, and hence to minimise predicted mixing in the system. We present examples of curves for a variety of parameters that minimise the predicted mixing in the hopper-silo system.展开更多
文摘A wedge-shaped planar mass-flow hopper system was modelled using stress-field theory as found in the literature, The authors present governing equations for stress and velocity fields under a radial- flow assumption in a converging hopper. The velocity in the silo above the hopper is modelled as plug flow, Two set-ups are modelled, one where powder layers in the hopper are assumed to be flat, and the second in which the layers are heaped at some characteristic angle, The ejection times and residence-time distributions are calculated and presented for a range of heap angles. For realistic heap angles, the spread of the residence-time distribution decreases with increasing heap angle; in one case, the spread is halved to a well-defined limit. At this limit （the critical heap angle） the geometry of the hopper can be optimised to minimise the spread of the residence-time distribution, and hence to minimise predicted mixing in the system. We present examples of curves for a variety of parameters that minimise the predicted mixing in the hopper-silo system.
