Improving Mixing by Changing Topology Through Intermeshed Perturbation Rings in A Co-Rotating Non-Twin Screw Channel

Abstract

A new kind of perturbation ring element (PRE) is first proposed to introduce a repetitive topology of splitting and recombination across the intermeshing zones of a co-rotating non-twin screw elements (NTSE) with a speed ratio of 2. A numerical simulation is performed using finite element method (FEM) along with the mesh superposition technique (MST). Post-treatment codes are successfully developed where fourth-order Runge–Kutta scheme is used to achieve particle tracking. For the tracer particle groups released initially from the upper and bottom intermeshing regions, mixing is characterized in terms of the evolution of tracer particles, mixing variance index, and residence time distribution (RTD). The numerical results revealed for a given output, the larger the screw speed, the larger the dividing ratio, and the better distributive mixing is. PRE achieved the best distributive mixing owing to the changing of flow topology. In TSE there are Komogorov-Arnold-Moser (KAM) tubes in which the tracer particles are confined to prevent better mixing from occurring.