Abstract:

For comprehensive description of differential rotors’ sections, one united geometrical design model is developed using relative motion method by introducing minus-plus transition coefficient for design sectional profiles of both co-rotational and counter-rotational twin rotors. From which, different types of novel rotors’ sectional profiles can be established by varying differential ratio and screw head number as well as other structural parameters. As an example, the model is used to form one mixing part constituted from double screw rotors of the same diameter and the different screw pitches with differential ratio of 3:1 either in co- or in counter-rotation. Polyflow software is used in finite element analysis numerical simulation of high density polyethylene melt in flow mixing for both coupling directions. It is shown that double differential counter-rotors exhibit uniform, longer residence time and smaller range of residence time distribution showing better distributive mixing capability in contrast with stronger extensional mixing and shear function showing better dispersive mixing capability for double differential co-rotors.

Key words: mixing, numerical simulation, sectional profiles, united geometrical design, twin rotors in differential screw coupling