Case Study of the Hydraulic Design of a Suction Chamber: CFD Calculation and Its Traps

For a large sewage pumping station a suction chamber is designed to deliver fluid free of rotation and with an equal velocity field distribution to the inlet of the pump impeller. Tight geometrical constraints have been incorporated in a new design for the pump suction layout. During the first step in the design process the suction layout of successively placed bend, diffuser, bend and suction chamber have been designed. This design step is validated by means of three-dimensional flow analysis. From the CFD analysis different performance parameters are computed and the geometry is fine-tuned. Finally a scaled down air test is executed to verify and analyze the performance of the design. The design, CFD analysis and scaled down air test of the suction chamber will be described in this paper. It will be shown that flow patterns will not in all cases be correctly predicted from CFD analysis and that in many cases validated experience is needed to give the designer full confidence in the performance of the design.