Potential Flow Analysis of the Forces on a Laboratory Centrifugal Pump Impeller

Two dimensional potential flow was used to determine the pressure field in a laboratory centrifugal pump. The impeller and volute were modeled simultaneously, using the finite element technique. Simulation of impeller rotation was accomplished by generating steady state solutions with the impeller in 10 different angular orientations within the volute. As a result, the interaction between the impeller and volute developed naturally as a result of the solution. Model results showed that blade pressure profiles were asymmetric, even at design flow. These asymmetries were even more pronounced at off design flow rates. The causes of these asymmetries were examined in terms of the interaction between the impeller, and the tongue and discharge regions of the volute. In addition, the blade pressure profiles were integrated to determine the impeller unbalance force. The forces were calculated at design and off design flow rates. The frequency content of the forces was also examined. Fluctuating components of force, due to impeller orientation, were found to be on the order of 30% of the static force. Finally, a comparison was made between the computationally determined forces and measured forces reported in previous studies.