Theory and experiment of foil bearing limiting load capacity based on Coulomb friction effect

The foil structural finite element model of bump-type gas foil journal bearing was developed in consideration of Coulomb friction in foil structure. The compressible gas lubricated Reynolds equation and the film thickness equation were solved together by using finite element method and finite difference method. The Coulomb friction effect on bearing limiting load capacity were studied when the journal eccentricity reached the limit. The test bed was established to test the limiting load capacity for two bump-type gas foil journal bearings with different roughness of bearing housing cylindrical hole surface by using temperature method. The numerical and experimental results were compared, indicating that the bearing limiting load capacities with roughness of bearing housing cylindrical hole surface 0.4 μm at speed 10000 r/min and 20000 r/min are 15.5 N and 42.3 N respectively, while the bearing limiting load capacities with roughness 1.6 μm are 10.9 N and 29.6 N respectively. The bearing limiting load capacity decreases with the increasing of roughness of bearing housing cylindrical hole surface due to the enhanced stiffness of bump foil caused by Coulomb friction force in foil structure, and the trend of numerical results agrees well with the experimental results.