Numerical Simulation of Hydrodynamics and Mixing Characteristics of High-Viscosity Non-Newtonian Fluid in Twin-Shaft Kneaders

The hydrodynamics of high-viscosity non-Newtonian fluid in three different twin-shaft kneaders were simulated by the finite element method (FEM) and mesh superposition technique (MST). The particle tracing technology is used to explore the mixing process and mechanism. The elongational flow and shear flow coexist in the kneaders, and the shear flow is dominant close to the wall, while the elongational flow is dominant far away from the wall. The twin-shaft kneader where the distance of the adjacent disc is the closest (Asymmetric-Disc kneader) results in the highest shear rate and power consumption. There are strong compression and stretching effects in the overlapping zone, which promote the mixing process. The static kneading rods can significantly enhance the reorientation of particles and increase the stretch length and mixing efficiency while the power consumption increases slightly. Considering the mixing ability and power consumption, the mixing ability of the three kneaders is ranked as Static-Rod kneader > Asymmetric-Disc kneader > Open-Window kneader.