Abstract
The mixing vessel with an unsteady speed impeller, which has been developed by ULCAM Ltd. JAPAN, was applied to laminar liquid mixing. The unsteady speed was generated by using the combination of three non-circle cams. The impeller revolved on its own axis. In unsteady speed mixing with planetary motion, the shaft with the impeller revolved around the vessel center. The mixing performances of the unsteady speed impeller were compared with those of a conventional impeller with steady speed. Two-blade, four-blade, six-blade and pitched-blade (up-pumping and down-pumping) paddle and Rushton turbine impellers and Maxblend® were used as the conventional impellers. The mixing time and the flow pattern were measured by the flow visualization with the decolorization method in which the reaction of sodium thiosulfate and iodine solution occurred. Because the center of the vortices, doughnut rings, above and below the impeller was moved by the unsteady motion, the doughnut rings disappeared soon. In unsteady speed mixing with planetary motion, the doughnut rings were not generated and the mixing time decreased.
