A High-Speed Fuel Lubricated Hybrid Thrust Bearing for Limited-Life Turbine Engines

The feasibility of operating a mainshaft thrust bearing at high speeds with jet fuel mist as the coolant and lubricant has been demonstrated in both rig and engine testing. A split-inner ring hybrid thrust bearing ( silicon nitride balls ) was successfully operated to 1.67 x 10⁶ DN at maximum Hertzian contact stresses up to 322,000 psi. The bearing configuration also included BG-42 inner and outer rings and a Dupont polyimide Vespel separator. The incorporation of a fuel lubrication system for limited-life turbine engines has many advantages, including;

• Lower cost ( elimination of oil system related hardware ).
• Enhanced long-term storage reliability
• Increased cold start reliability.

The bearing has been subjected to a variety of hostile tests, including;

• Snap accelerations from -65 deg F cold soak
• Extended operation at similar thrust and radial loadings
• Operators at high thrust levels thrust levels

This paper describes the development history, including rig and engine testing, as well as the analytical challenges overcome in designing the hybrid configuration.