CFD SIMULATION OF 3D FLOW FIELD IN THE HIGH-SHEAR FIBER KNEADER

摘要

A novel kind of high-shear fiber kneader, designed by Tianjin University of Science and Technology, has the abilities of extruding, shearing and mixing to pulp fibers, and it can effectively remove shives of high yield pulps (HYP). At the same time, mechanically modifying the cellulose fibers to some extent is one of its functions. This paper tried to explore the flow principle of pulp in the high-shear fiber kneader and the mechanism to pulp fibers by analyzing the 3D flow field in the kneader with the computational fluid dynamics (CFD) simulation system. The geometric model of the high-shear fiber kneader was established with Pro/E software, and the generation of its computational grid as well as the definition of the boundary type was processed by GAMBIT. Moreover, standard ε . k two-equation viscosity model was selected for the discrete analysis. The main parameters were calculated including temperature field, pressure field and velocity field. The temperature distribution of the flow field showed that the temperature in the area near the extruding exit increased markedly. The pressure distribution of flow field exhibited that the pressure inside the kneader decreased along axis from inlet to exit gradually. The velocity distribution of flow field demonstrated that the velocity on the inner surface of the barrel wall was zero. From the trace picture of pulp fluid between the single screw and barrel wall, it could be found that there was no countercurrent and plug flow of pulp, but a part of pulp running slower than the rest. The simulation results provided a reliable and visible theoretical basis for the further optimization of the equipment structure and process parameters by analyzing the 3D flow field.