Using hydrophone measurements to monitor incipient cavitation in variable displacement pendulum-slider pumps

The present work proposes an experimental methodology for monitoring the inception and the subsequent development of cavitation and aeration in variable displacement pendulum-slider pumps. These two phenomena may affect volumetric machines when the working condition requires high values of working speed and specific displacement, often causing undesired broadband noise. Since these pumps find their most common application in automotive auxiliary systems and powertrain lubricating circuits, the abnormal noise caused by this phenomenon is often unacceptable. Based on these considerations, an experimental cavitation detection method based on hydrophone measurements is proposed and assessed through direct comparison with a non-cavitating machine. Cavitation is promoted by increasing the pump working speed, as it happens in actual automotive applications. The effective presence of cavitation is further checked with the help of durability tests and efficiency measurements, made possible by the capability to control the pump working eccentricity. Measurements are repeated for different values of both specific flow rate and oil temperature, showing that these operational parameters have a consistent interaction in the definition of the inception of the phenomenon and its intensity.