Three-dimensional Finite Element Solution of the Flow in Single and Twin-Screw Extruders

Abstract

This work is aimed at the numerical modeling of the flow inside single and twin-screw extruders. Numerical solutions are obtained using a recently developed immersed boundary finite element method capable of solving the flow in the presence of complex non-stationary solid boundaries. The method is first validated against the solution obtained on a body-conforming grid for a single screw extruder and then applied to a twin-screw mixer. The time dependent single screw problem can also be solved in a rotating reference frame for which a steady state solution can be obtained. This allows the evaluation of time integration errors of the moving immersed interface algorithm. For instance the flow is considered isothermal and the material behaves as a Generalized Newtonian fluid. Because the viscosity depends on the shear rate, solutions will be shown for various rotation velocities of the screw and compared with solutions obtained on body-conforming grids. The method is shown to give very accurate results and can be used for a more in-depth investigation of the material behavior in extruders.

A Global Model for Starve-Fed Nonconventional Single-Screw Extrusion of Thermoplastics

“…20 A review on global modeling of screw processing has been presented by Teixeira et al 21 and Wilczynski et al 22 The main goal of this paper is to develop an integrated computer model for starve-fed nonconventional single-screw extrusion to predict the extent of filling, the pressure and temperature profiles, as well as the locations of melting. The Maddock mixing section has been used in the study.…”

Three-dimensional Numerical Study of the Mixing Behaviour of Twin-screw Elements

“…The IB finite element method was validated against solutions on body conforming meshes in a previous work (Ilinca and Hétu 2010b) and therefore is not revisited here. Two different configurations are studied containing either conveying or mixing elements and the mixing behavior of each of them is analyzed.…”

“…Our recently proposed approach (Ilinca and Hétu, 2011) achieves the level of accuracy of cut cell dynamic node addition techniques with none of their drawbacks (increased CPU time and costly dynamic data structures). This approach was extended to moving fluid/solid interfaces (Ilinca and Hétu, 2010a) and to single and twin-screw extruders (Ilinca and Hétu, 2010b). For problems involving convective transport, the proposed IB method was shown to predict adequately the flow structures produced by the continuous repositioning of the solid surfaces.…”

A computer model for starve‐fed single‐screw extrusion of polymer blends

“…[1][2][3] Flood fed single-screw extrusion is generally well understood, and the literature is very rich here. [16][17][18][19] Wilczyński et al [15,20,21] first developed a mathematical model of fusion of polymers in starve fed single-screw extruders, and subsequently a composite model of the process, first for conventional screws, and later for non-conventional screws. [7][8][9][10] Starve fed extrusion process is much less known.…”