A STUDY OF THE FLUID FLOW THROUGH THE RECTANGULAR TAPERED TUBE DISTRIBUTOR BASED ON CFD

摘要

The rectangular tapered tube distributor with manifold is one of the key parts of a hydraulic headbox. The height of the rectangular tapered tube is determined with Baines formula and the height curve is simplified and replaced with a straight line because of the limit of manufacture. To test the influence of the simplified structure on flow behaviour, a computational fluid dynamic (CFD) method is adopted to analyse the flow behaviour in the rectangular tapered tube distributor. As the computational results have shown, the pressure distribution in the tapered tube and the mass flow rate out of the manifold tubes are obviously influenced by the length of the taper, the length of the transitive tube and the direction of inlet flow. The pressure distribution in the rectangular tapered tube distributor and the mass flow rate out of the manifold tubes, when the stock enters paralleled with the back wall, are more uniform than those when the stock enters paralleled with the front wall. The longer the transitive tube and the taper are, the more uniform the both are. The oblique flow from tapered tube to manifold causes strong vortex at the inlet of manifold, which results in a speed gradient and lasts a large extension in the manifold. The results show that the simplified tapered distributor designed with the Baines formula cannot offer uniform pressure distribution in the taper and uniform mass flow rate out of the manifold tubes to meet the high speed paper machine.