Thrust Bump Air Foil Bearings with Variable Axial Load: Theoretical Predictions and Experiments

Abstract

Thrust air foil bearings are critical components in high-efficiency turbomachinery, such as two-stage compressors subjected to large and irregular axial forces. In this article, a model of thrust bump foil bearings that predicts deflection with variable axial load is developed assuming no tilting effect of the thrust collar. To predict the air clearance, deflection of the elastic foundation was used in the air film height equation. Combined Dirichlet and Neumann-type boundary conditions were used for static load performance predictions.

To verify the theoretical model, tests were performed with three different thrust air foil bearings with outer radii of 45, 50, and 55 mm. The rotating speed ranged from 10,000 to 25,000 rpm. From the test results, the model using nonlinear stiffness was in better agreement with the experimental results than the model using linear stiffness.

KEY WORDS:

• Thrust Air Foil Bearing
• Bump Foil
• Axial Load
• Nonlinear Stiffness

ACKNOWLEDGEMENTS

This work was performed by the Korea Institute of Science and Technology (KIST) and supported by a grant from the KIST project “R&D on Power Generation and Energy Storage Technology for Tri-Gen System” and a Korea Energy Management Corporation (KEMCO) project, “The Development of a High-Speed Motor System.” The authors thank KIST and KEMCO for their support.

Review led by Alan Lepeck