Analysis of Unsteady Impeller Diffuser Interaction in a Centrifugal Pump

The paper reports on acoustic and aerodynamic experiments conducted on a seven–blade centrifugal pump as part of an ongoing investigation into the flow field instabilities and the noise generated by these instabilities in centrifugal turbomachinery. The test model is a low-pressure stage of a two-stage pump-tur¬bine used as a pump. It was fitted with two diffusers with twenty-two adjustable guide-diffuser vanes and a return channel with eleven continuous vanes. The diffuser was designed and built to permit pressure measurement both in the adjustable guide-diffuser vanes and in the continuous vanes surfaces. In order to establish a link between the flow field structure at part load and acoustic radiation, mean flow velocity was meas¬ured in the vaneless part of the diffuser and piezoelectric trans-ducers, placed flush with the wall, were used to measure the pressure level inside the blade channels.