Pressure instabilities in a vaned centrifugal pump

This article reports the acoustic and fluid-dynamical analyses of large-scale instabilities in a vaned centrifugal pump. The unsteady pressure fields at full/part load were measured by dynamic piezoresistive transducers placed at the impeller discharge and on an instrumented diffuser vane. To spectrally characterize the inception and the evolution of the unsteady phenomena, spectral analyses of the pressure signals were carried out both in frequency and time-frequency domains. Numerical analyses were carried out on the same pump with the help of the commercial code CFX. All the computations were performed using the unsteady 'transient' model with a time step corresponding to about 1 degrees of the impeller rotation. The turbulence was modelled by the detached eddy simulation model. Numerical pressure signals were compared with the experimental ones to verify the development of the same pressure instabilities. The unsteady numerical flow fields were analysed to study the fluid-dynamical evolution of the instabilities and investigate their origin.