Computational Study of the Noise Radiation in a Centrifugal Pump When Flow Rate Changes

The noise radiation is of importance for the performance of centrifugal pumps. Aiming at exploring noise radiation patterns of a typical centrifugal pump at different flow rates, a three-dimensional unsteady hydro/aero acoustic model with Large Eddy Simulation (LES) closure is developed. Specifically, the Ffowcs Williams-Hawkings model (FW-H) is employed to predict noise generation by the impeller and volute. The simulated flow fields reveal that the interactions of the blades with the volute induces Root Mean Square (RMS) pressure and further leads to noise radiation. Moreover, it is found that the profiles of Total Sound Pressure Level (TSPL) regarding the directivity field for the impeller-generated noise demonstrate a typical dipole characteristic behavior, whereas strictly the volute-generated noise exhibits an apparently asymmetric behavior. Additionally, the design operation (Here, 1Q represents the design operation) generates the lowest TSPL vis-a-vis the off-design operations for all the flow rates studied. In general, as the flow rates decrease from 1Q to 0.25Q, TSPL initially increases significantly before 0.75Q and then levels off afterwards. A similar trend appears for cases having the larger flow rates (1Q~1.25Q). The TSPL deviates with the radiation directivity and the maximum is about 50%. It is also found that TSPL by the volute and the blades can reach ~87 dB and ~70 dB at most respectively. The study may offer apriori guidance for the experimental set up and the actual design layout.