Detecting cavitation inception in external gear pumps by means of vibro-acoustic measurements

The present work investigates cavitation in external gear machines by means of a dedicated experimental campaign. Four different pump prototypes have been designed and manufactured to perform this research, one of them specifically built up to not be affected by such a phenomenon. Vibro-acoustic measurements performed by a hydrophone and a high-frequency accelerometer are put in comparison with measurements of inlet and outlet pressure ripple, in order to enlighten their capability to follow the development of the phenomenon. Waterfall spectra are investigated and later Root Mean Square (RMS) values of the filtered signals are shown with respect to the cavitation number and compared with efficiency measurements. Results demonstrate that vibro-acoustic measurements associated to a dedicated signal processing procedure represent a powerful tool to detect cavitation inception in gear pumps. In addition, effect of oil temperature is investigated, showing its contribution in spreading the phenomenon on a wider speed range.