Numerical Analysis of the Effect of Geometric Variations on the Mass Flow Distribution for an Under-Race Lubrication System

Operating conditions of modern aero-engines place a significant demand on oil for the lubrication and cooling of roller bearings. The supply of the required lubricant is often achieved by a system consisting of an oil jet targeted onto a feed geometry machined into the shaft. This cavity leads the oil through a number of equispaced feed holes in the inner race of the bearing, allowing direct lubrication and cooling of the components. This lubrication technique is commonly known as under-race lubrication. Achieving uniformity is of crucial importance for efficient lubrication and cooling. This study explores the effect of key geometric parameters of the shaft cavity on the oil flow distribution for different operating conditions. The analysis is perfomed using Implicit Incompressible Smoothed Particles Hydrodynamics (I-ISPH) simulations, focusing on the variation of groove length, groove depth, groove taper, hole diameter and hole axial distance. The analysis of the results reveals that groove characteristics have a limited impact, while hole diameter and axial distance significantly influence the oil distribution. An investigation of the film thickness inside the cavity is performed, and its correlation with the oil mass flow through the feed holes is discussed.