Diagnostic Process by Using Vibrational Sensors for Monitoring Cavitation Phenomena in a Getoror Pump Used for Automotive Applications

A full experimental investigation on a Gerotor pump used for the lubrication of engines is described in this paper. These pumps, as well known, are widely used on engines for all hydraulic circuits and, for this reason, often they work in some conditions (such as at high speeds and pressure value) which are very challenging. In this paper one of the most unwanted phenomena that often occurs during the pump operation has been investigated: the cavitation. The cavitation can be triggered by many multiple factors such as the sloshing in the tank (translational and rotational motions), high percentage of gas dissolved in the fluid and pressure too low at the pump suction port. Therefore, the characterization of a Gerotor pump in cavitation condition is really interesting. In order to replay the cavitating conditions a pump has been installed on a dedicated test bench of the Department of Industrial Engineering of the university of Naples “Federico II”. The pump has been forced to cavitate by placing calibrated orifices on the suction side of the pump. Many decreasing diameters have been located in an aluminum connection block, to measure all the working parameters like the flow-rate, pressure (at the suction and delivery ports), pump speeds and pressure ripple. Cavitating and no-cavitating conditions have been investigated by using an accelerometer sensor in proximity of the pump suction chamber with the aim of monitoring the phenomena in terms of vibration amplitude. As afore mentioned, the pump under investigation has been studied in all operative conditions with and without cavitation phenomena by using a non-intrusive sensor like accelerometer in order to monitoring if cavitation is present. More precisely, the accelerometer sensor has been located close to the pump suction chamber and the vibrations have been acquired contemporarily with pressure signals (intake and outgoing discharge) and properly triggered with tachometer signal by using a multichannel acquisition system (Siemens™). A spectral vibration analysis has been used as diagnostic tool for accurately detecting pump degradation. The results coming from the analysis have shown that in presence of cavitation phenomena the non-intrusive monitoring technique represent a good diagnostic method for assessing pump operability.