Modelling and Validation of Tooth Tip Leakages in Gerotor Pumps

Abstract

Gerotor pumps are commonly used as charge pumps in hydrostatic transmission systems as well as in fuel injection and automotive lubrication systems. For high pressure applications, Gerotors suffer from internal leakages which are one of the main sources of volumetric loss. The curvature of typical gear profiles for Gerotors prevents the usage of simple analytical relations to describe this leakage flow. In this paper, a non-dimensional functional relationship is developed between geometric and flow parameters to model this leakage flow. A set of CFD simulations are conducted on the tooth tip geometry to establish this relationship. Then, an experimental setup is designed to reproduce the flow conditions at tooth tip of Gerotor. Experiments are conducted for a range of geometric and flow parameters and results from experiments are used to validate the proposed non-dimensional model. The tooth tip leakage model developed and validated in this work is valuable for pump designers in determining the impact of gear geometry and clearances on volumetric performance of the pump. Moreover, the model can be readily used in any lumped parameter based simulation tool permitting a fast and accurate prediction of the tooth tip leakage flow and hence the volumetric efficiency of the unit.