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 out by the Technical University of Braunschweig in cooperation with the University of Magdeburg, Germany. The project is focused on two centrifugal pumps, one scaled down from the other, having the same low specific speed number. The pumps are operating under variable two-phase flow conditions. Flow structures within the pump impeller and the overall pump performance are investigated by numerical simulation and experiments. One impeller blade of the pump is equipped with eight miniature pressure transducers. A telemetric system is mounted on the shaft for transmitting the data from the rotating impeller. By integrating the blade pressure along the radius, blade momentum and power can be calculated. Using this additional information, hydraulic losses, impeller disc friction, and volumetric losses can be distinguished from each other for various gas fractions. These results improve the understanding of the physical mechanism which is responsible for the performance drop of pumps while operating under two-phase flow conditions. The experimental results are used for validating the numerical simulations. The single-phase flow (water) was first calculated using the CFD-code CFX-TASCFlow. For calculating the twophase flow, the CFD-code PHOENICS with the implemented Eulerian multiphase flow model IPSA (Inter Phase Slip Algorithm) was applied. The numerical results are compared to the experimental data and show good consistence for various gas void fractions.