PRESSURE INSTABILITIES IN A VANED CENTRIFUGAL PUMP

The paper reports on 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 piezo-resistive 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 one degree of the impeller rotation. The turbulence was modelled by the DES model. Numerical pressure signals were compared with the experimental ones to verify the development of the same pressure instabilities. The unsteady numerical flow fields was analysed to study the fluid-dynamical evolution of the instabilities and to investigate their origin.