Estimations of leakages through gaps at ‘transition’ contacts using computational fluid dynamics and photoimaging of core-flow cavitation features in Gerotor pumps

Abstract

Chambers in the Gerotor pump units are separated by metal-to-metal geometrically form-closed higher pair active contacts in the lobes of star and ring components. With rotation when the chamber volumes expand and contract, the active contacts move on lobe profiles and are subjected to deformations due to contact stress caused by fluid pressure and transmitted torque. Evidently at two transition active contacts, which separate the high-pressure chambers from the low-pressure chambers, gaps are generated due to contact deformations. However, it is for a short period of time during operation and mostly not at the same time in the two transition contacts. From our experimental visual investigation by photoimaging technique on flow processes, we have visualized that at some angular positions of the star–ring, cavitation occurs inside the chamber. In an earlier work, in the estimation of gaps in transition contacts, we have first evaluated the stresses, deformations at all ideally form-closed active contacts in our chosen Gerotor pump using static structural analysis in the Ansys^® environment. In the present work, to investigate the flow characteristics, including the formation of cavitations in the Gerotor pump, numerical analysis using the computational fluid dynamics tool in the Ansys^® environment has been carried out. We analyze the flow process for the different angular positions of a star. Results obtained by the numerical analysis have good agreement with the flow patterns visualized experimentally.