CFD Analysis of Cavitation in Flow through a Gerotor Pump and the Prediction of Erosion Zone due to Cavitation

A Gerotor pump is a positive displacement pump consisting of inner and outer rotors, with the axis of inner rotor offset from axis of outer rotor. Both rotors rotate about their respective axes. The volume between the rotors changes dynamically, due to which suction and compression occurs. Due to their high-speed rotations, a Gerotor pump may be subjected to erosion due to cavitation. This paper details about the Computational Fluid Dynamics (CFD) based methodology that has been used to capture cavitation bubbles, which might form during the operation of Gerotor pump and to identify the erosion zone which might be occur due to cavitation bubble getting burst near the surface layers of the gears. A full scale (3D) transient CFD model of a Gerotor pump has been developed using commercial CFD code ANSYS FLUENT. The most challenging part of this CFD flow modeling is to create a dynamic volume mesh that perfectly represents the dynamically changing rotor fluid volume of the Gerotor pump. Two different approaches have been used to model this dynamic mesh analysis in the Ansys Fluent tool – one method by using the traditional UDF script and, another method by using Python automation script. This CFD methodology includes complex geometry of the Gerotor along with moving fluid volume between two rotors. The complex flow through Gerotor has been successfully modeled using dynamic mesh & Volume of Fluid (VOF) model for entire 8 rotations. This paper helps an engineer to choose an easy and quick alternative method to model a complex flow through a Gerotor, understanding the flow physics and helps the engineers to improve the design by reducing erosion & increasing its life cycle.