Evaluation of Distributive Mixing Performance of Fin Type Screw for a Single Screw Extruder

In this study, the distributive mixing performance of Dulmage screw (DS), which is a type of fin mixing screw for a single screw extruder, was evaluated experimentally and numerically and the distributive mixing mechanism was investigated. The performance of DS increased basically with increase of the screw rotation speed, but the performance decreased under certain extrusion conditions. In the fin section, the positions of pigment changed by the circulation flow inside the fin groove and the degree of the change depended on the screw rotation speed. On the other hand, in the torpedo section, the flow velocity of pigment in the circumferential direction showed distribution in the radial direction. Thus, the distances moved by each pigment in the torpedo section were different. Moreover, the size of these differences determined whether or not splits occurred in the distribution of pigment on the fin inflow surface in the next stage. Especially, the DS distributive mixing performance tended to increase when a lot of pigment was distributed on the flight surface. From these results, it became clear that the performance depends on the amount of pigment that is distributed in the radial direction on the fin outlet surface.