(An) experimental study on the performance of air foil thrust bearing for application to turbomachinery

Abstract

Air foil bearings are very attractive bearing system for turbomachinery because they have several advantages over conventional bearings in terms of oil-free environment, low power loss, long life and no maintenance. However, most of the developed machines using air foil bearings are limited to small and high speed rotors of 60,000 ~ 120,000 RPM, since the increase in power of turbomachinery requires lower rotor speed and greater loading in bearings, which makes it difficult to use air foil bearings for large machines. Nevertheless, the industrial sector gradually demands oil-free turbo machines to be applied in the new fields in relation to the advantages of energy saving, low vibration, low noise, and environment-friendly system. In this paper, the performance of an air-lubricated foil thrust bearing for application to a 75kW turbo machine has been investigated by an experimental approach. A simplified numerical elastohydrodynamic procedure is introduced and employed for optimal design of the bearing geometry under given design parameters. The effects of various operating conditions on bearing performance have been numerically predicted with the optimized geometry to assess the bearing’s behavior in the turbo machine. A rotor-bearing dynamic simulator was developed for the purpose of evaluating the performance of air foil thrust bearings under realistic dynamic environment. The test rig was equipped to provide a quantitative analysis of power loss by measuring temperatures and flow rate of cooling air. The objectives of the experimental study are to evaluate the performance of the bearing in terms of power loss, load capacity and axial movement by axial load. The results have been presented by applying uncertainty analysis with 95% confidence level considering uncertainties related to current experimental approach. According to the tests of the air foil thrust bearing designed by current method, the maximum load capacity is located between 800 N ~ 1000 N at 26...