Statistical research on the mixing properties of wave based screws by numerical simulations

Abstract Research based on numerical simulation with the CFD software ANSYS POLYFLOW is conducted on the mixing properties for the wave screw elements, as well as barrier screw elements, by using statistical tools. Then, the investigation is conducted in detail on the relationship between pressure, maximum shear rate, mixing index and other flow field characteristics of the two above screws under the same simulation conditions. It is found that polymer melt flow in the wave screw possesses various advantages compared with the normal barrier screw, such as acquiring larger pressure, stronger shearing and stretching action, better mixing and efficiency, which mainly result from the periodic depth change design in the screw groove. On the other hand, the increased wave bulge in the wave screw lessens the space for the polymer melt to be conveyed forward, which can greatly reduce the original function of the secondary flight. Also, the convergent and divergent zones in the wave screw groove produce a much stronger stress favoring the shear and elongation rates, and also lead to a sharp increase of the axial force load on the wave screw. Consequently, for the optimization of the wave screw configuration it is suggested to reduce the axial force without decreasing the effect of the excellent distributive and dispersive mixing.