Investigation of Air Flow in Turbomachinery Bearings Using a Computational Fluid Dynamics Approach

A CFD model was created in the commercially available ANSYS Fluent software. It simulates a geometric configuration of a class of bearings which is ubiquitous in the field of turbomachinery and is based on actual flight hardware. This model is transient and fully three dimensional. Additionally, it accounts for motion of the geometric configuration based on a detailed kinematic analysis, which includes the definition of contact angle of the bearing and the resulting misalignment of the rolling elements’ rotational axes with the rotation axis of the shaft. This misalignment leads to a natural pumping action of the bearing, and the resulting air flow is modeled using Unsteady Reynolds-Averaged Navier Stokes (URANS) based k-ω SST turbulence model. Different combinations of the inflow boundary conditions were simulated in this study. The results indicate that the natural pumping action of the bearing is affected by the upstream conditions. They further show that the tangential component of the velocity is predominant for the flow inside the bearing, and it is one order of magnitude more than the other two components. Finally, it is observed that bearings without a protruding shaft aspirate 3.6 times more air, by volume, than bearings with a shaft extending through them.