Abstract: Numerical simulation of melt flow between differential twin screw rotors and unequal barrel holes was carried out using Polyflow software. 88 % of the mixing index for 3∶1 differential rotors was ranged between 0.5 and 1, indicating a strong extensional flow field. The mixing behaviors of both counter-rotation and co-rotation were equally good. In the co-rotation cavity, the high-speed zone was wider, degree of in-uniformity was higher, viscosity-thinning more obvious, which was favorable for material exchange. In the counter-rotation cavity, pressure and shear rate were larger, which was favorable for establishing higher pressure.

Key words: differential twin rotors with unequal diameters, mixing index, segregation scale, trace particle, numerical simulation