Identification of Cavitation Instabilities on a Three-Bladed Inducer by Means of Strain Gages

The present paper reports the experimental characterization of the cavitation induced flow instabilities of a high head three-bladed inducer at design condition detected simultaneously by means of piezoelectric pressures transducers located at different axial and azimuthal stations on the casing of the pump and through strain gages mounted on the pressure side of each blade. The purpose of this experimental campaign is a deeper insight of the phenomena associate to the flow instabilities obtained by the simultaneous analysis performed in the stationary and rotating frames. Both the sensors set-ups proved to be able to detect the main flow instabilities such as synchronous and sub-synchronous rotating cavitation, cavitation surge and tip vortex instability. Moreover, the simultaneous analysis of the results supported by high speed movie has allowed for assessing the mutual relations between the instabilities.