Evaluation of Air/Cavitation Interaction Inside a Vane Pump

Generally, in a positive displacement pump, cavitation can occur when the fluid pressure falls under the vapour pressure at the operating conditions. This phenomena leads to the generation of vapour bubble dispersed inside the flow. In fluid power application, cavitation is mostly detrimental because the vapour bubbles could be transported by the fluid toward the high pressure zones inside the pump causing their implosion and hence shock waves. When these shock waves are sufficiently close to the pump walls their physical action on the walls appears as a surface mechanic erosion. Direct detection of cavitation is quite impossible because of the difficulties in positioning experimental sensors inside the fluid power components. To overcome this problem a valid alternative approach could be represented by the Computational Fluid Dynamic (CFD) tools. In this paper the CFD analysis of a vane pump is presented. All the 3D simulations were performed using Fluent V12. In particular, the pump analysis was focused on the generation and evolution of the cavitation phenomena inside the machine to identify the locations where this phenomena can occur. Moreover, the influence of incondensable gas dissolved inside the fluid operator on both pump performance and cavitation evolution was evaluated. Significant results were obtained about the influence of expansion/compression of non-condensable gas on the cavitation evolution. The adopted approach is generic in nature, and the obtained results can be easily use to optimise other pump designs as well.