Challenges in Validating a Thermo-Hydrodynamic Gas Foil Bearing Model

Abstract

Gas foil bearings (GFBs) are suitable for high speed and temperature applications where conventional lubricated bearing solution are not feasible. This requires the prediction of bearing temperatures and thus a thermal model considering the heat generation and heat flow paths in the bearing. The effects of two different bump foil stiffness (Iordanoff, I., 1999, “Analysis of an Aerodynamic Compliant Foil Thrust Bearing: Method for a Rapid Design,” ASME J. Tribol., 121(4), pp. 816–822; Le Lez, S., Arghir, M., and Frene, J., 2007, “A New Bump-Type Foil Bearing Structure Analytical Model,” ASME J. Eng. Gas Turbines Power, 129(4), pp. 1047–1057.) and heat transfer models (a simplified and a detailed one) are presented in respect to measured temperatures from literature (Radil, K., and Zeszotek, M., 2004, “An Experimental Investigation Into the Temperature Profile of a Compliant Foil Air Bearing,” Tribol. Trans., 47(4), pp. 470–479; Sim, K., and Kim, T. H., 2012, “Thermohydrodynamic Analysis of Bump-Type Gas Foil Bearings Using Bump Thermal Contact and Inlet Flow Mixing Models,” Tribol. Int., 48, pp. 137–148). The comparison is drawn over a wide range of operational conditions as well as measuring positions, which in such detail has not been shown before. While good agreement is found for some of the conditions and positions, only reasonable agreement is found for others. The deviations and difficulties in validating a thermal model against experiments are highlighted in a discussion about various temperature influencing parameters, especially concerning the change of clearance during operation. In conclusion, it is found that the models are able to predict temperatures reasonably well, but require delicate fine-tuning to achieve these results. Finally, the impact of temperature distribution on the maximum load capacity is evaluated by comparing predictions between an isothermal model and one including thermal effects.