Auxiliary Bearings for Turbine Engine Magnetic Bearing Systems

Magnetic bearing systems are an innovative approach to aircraft gas-turbine engine rotor support, with the potential to operate at high temperatues and speeds, to improve significantly engine specific fuel consumption, power/weight ratio, rotordynamics control and reliability, and to reduce maintenance by elimination of oil lubrication systems. Magnetic bearings require auxiliary ball and roller bearings to carry high transient maneuver loads thta exceed the magnetic bearing capacity and to support the rotor when the magnetic bearings fail or are turned off. Commercial hybrid-ceramic auxiliary ball bearings have performed best but have failed at high-speed touch-downs in recent magnetic bearing rotor testing. Special solid-lubricated self-contained ceramic bearings patented by Tribology Systems, Inc. (TSI), have already achieved considerable analysis and test experience under operating conditions very similar to that whihc auxiliary magnetic back-up bearings are subjected to, including rapid acceleration to high speeds and successful long-life operation under high transient shock loads. TSI was selected competitively to suppoy auxiliary bearing analysis and prototypes for United Technologies' magnetic bearing rotor testing this year. Starting with the above analysis and test experience, auxiliary ball and roller bearings for Army magnetic bearing gas-turbine engines will be analyzed with TSI's advanced bearing computer codes in coordination with the latest rotor dynamics and magnetic bearing control technology on Phase I. The resulting most promising bearing configurations will be made and tested at an engine manufacturer in Phase II.