Numerical analysis of the lubricating gap at bushes lateral sides in external spur gear

This paper focuses on the evaluation of the flow field in the lateral clearance of external gear pumps using CFD. The main aim of this work is to provide useful information about the net flow entering or exiting a tooth space volume as a function of the pressure at the boundaries (adjacent tooth space volumes and drain). Results provided in this research can be easily adopted in lumped parameter models often used for the simulation of the flow through a hydraulic pump. The paper provides many details concerning the mathematical model and the approach used to perform the simulations, considering previous works done in this field. In particular, some of the simplifying hypotheses made in these works have been further investigated, for example it is pointed out that the sliding relative velocity between the surfaces has a superimposed effect to the flow field generated by the gradient pressure. For the analysis a numerical model developed in C++ has been used that takes advantage of an open-source library (OpenFOAM®).The calculation of the flow field has been achieved solving the Laplace equation in a bi-dimensional domain, instead of the complete Reynolds equation. Details regarding the approach used for setting the boundary conditions and for the evaluation of the net flow are discussed in the paper. Furthermore, results are presented also in terms of comparison with the standard lumped parameter approach based on the Poiseuille equations