Journal Design Considerations for Turbomachine Shafts Supported on Foil Air Bearings~©

摘要

Foil air bearings can offer substantial improvements over traditional rolling element bearings in many applications, and arernattractive as a replacement to enable the development of advanced Oil-Free Turbomachinery. In the course of rigorousrntesting of foil journal bearings at NASA Glenn Research Center, shaft failure was repeatedly encountered at high ambientrntemperature and rotational speed, with moderate radial load. The cause of failure is determined to be excessive non-uniformrnshaft growth which increases localized viscous heating in the gas film, and eventually leading to a high speed rub andrndestruction of the bearing and journal. Centrifugal loading of imbalance correction weights and axial temperature gradientsrnwithin the journal due to the hydrodynamic nature of the foil bearings, determined by experiment and finite element analysis,rnare shown to be responsible for the non-uniform growth. Qualitative journal design guidance is given to aid in failurernprevention.