On the Relationship between Torque and Flow Structure in Powder Mixers

Abstract

This work establishes the link between direct measurement of powder flow in a horizontal mixer and shaft torque. Three agitator designs were used: one featured six long flat blades, one a long flat blade and the third, four series of short paddles. With the single long flat blade agitator, the amount of powder moved by the blade was related to the torque. The relationship between torque and nondimensional mean tangential velocity was demonstrated using phase diagrams. These remained unchanged with increase of agitator speed. The fluctuations of the torque with the long flat blade agitator were logically related to those for the single blade. The torque on the short-paddle agitator exhibited larger fluctuations which were strongly affected by the level of fill and the agitator speed. Powder cohesion had a significant influence on the mean and standard deviation of the instantaneous torque. Instantaneous torque measurement may be seen as a valuable method for process control.