EVALUATION OF THE TSI SMALL-SCALE POWDER DISPERSER

The TSI small-scale powder disperser was evaluated to study the effect s of total flow rate, capillary flow rate, and particle shape, size, a nd density on dispersion efficiency and internal losses. Dry powders, including carbon fibers, talc, alumina, and polystyrene microspheres, were used to represent materials with different physical properties. P olystyrene microspheres in the size range of 3-97 mu m were used to st udy the effects of particle size on performance. Results indicated tha t, for the same operating conditions, dispersion efficiencies for carb on fibers and polystyrene spheres were higher than talc and alumina. D ispersion efficiency increased as the total flow rate increased and re ached a constant value when the low rate was >8 l min(-1). Also the di spersion efficiency decreased as particle sizes increased at a given o perating conditions. As for the internal losses in the disperser, part icles were deposited primarily at the expansion zone of the venturi tu be. Adjustment of the capillary tube location to increase the capillar y Row rate did not result in any noticeable change in the efficiency, while poor alignment of the tube resulted in a significant loss as com pared with a proper alignment. Along with these data, computer simulat ions of the flow field and theoretical predictions of the lift force a s a result of high flow shear at the venturi throat were successfully used to interpret particle deposition in the TSI small-scale powder di sperser.