Modelling of a Gerotor pump including the evaluation of the micro-movements of the external gear

Abstract

Gerotor pumps are positive displacement pumps used in many applications thanks to their compact size and low cost. On the other side the efficiency of the machine is not so brilliant. In order to study design modifications to decrease energy consumption, a lumped parameter model is a useful tool since it allows predicting and enhancing pump performance. This type of model can be used, once complete, to analyse various phenomena such as cavitation, the chambers’ pressure transient, the flow and pressure ripple, the leakages, and the noise emissions. This work presents a lumped parameter model for the analysis of a Gerotor pump, including the evaluation of the micro movements of the external gear. These micro-movements potentially affect the gap geometry at the internal gear tooth tips and have an impact on the pump’s performance. We modelled the behaviour of the external gear as a journal bearing under dynamic load and then we compared various methods to solve the problem and to find the most suitable method to be coupled with the lumped parameters model of the pump. We incorporated the methods into our global model and evaluated their performance in terms of accuracy and required computational times. The results obtained and the impact on the teeth gaps geometry are finally compared and discussed.