EXPERIMENTAL INVESTIGATION AND NUMERICAL SIMULATION OF TWO CENTRIFUGAL PUMPS OPERATING UNDER VARIABLE GAS/LIQUID TWO-PHASE FLOW CONDITIONS

摘要

This paper reports on a research project which was carried outrnby the Technical University of Braunschweig in cooperationrnwith the University of Magdeburg, Germany. The project is focusedrnon two centrifugal pumps, one scaled down from the other,rnhaving the same low specific speed number. The pumps arernoperating under variable two-phase flow conditions. Flow structuresrnwithin the pump impeller and the overall pump performancernare investigated by numerical simulation andrnexperiments.rnOne impeller blade of the pump is equipped with eight miniaturernpressure transducers. A telemetric system is mounted onrnthe shaft for transmitting the data from the rotating impeller. Byrnintegrating the blade pressure along the radius, blade momentumrnand power can be calculated. Using this additional information,rnhydraulic losses, impeller disc friction, and volumetricrnlosses can be distinguished from each other for various gas fractions.rnThese results improve the understanding of the physicalrnmechanism which is responsible for the performance drop ofrnpumps while operating under two-phase flow conditions.rnThe experimental results are used for validating the numericalrnsimulations. The single-phase flow (water) was first calculatedrnusing the CFD-code CFX-TASCFlow?. For calculating the twophasernflow, the CFD-code PHOENICS? with the implementedrnEulerian multiphase flow model IPSA (Inter Phase Slip Algorithm)rnwas applied.rnThe numerical results are compared to the experimental datarnand show good consistence for various gas void fractions.