High-Temperature Hybrid Foil Bearing for Unmanned Aerial System Gas Turbines

Small unmanned aerial systems (UAS) are a critical element in current military operations, and their use will increase substantially in the future. The propulsion system is a key design constraint in any UAS, and current small gas turbines for these vehicles are limited by the conventional oil-lubricated rolling element bearings used to suspend their high-speed rotating assemblies. Foil bearings offer a potentially attractive alternative, but despite their very successful commercial application to aircraft air cycle machines, they have not been widely used in gas turbine systems due to limitations with high-temperature operation, cost, and a variety of other issues. The objective of the proposed project is to develop a new hybrid foil bearing concept that has the potential to address the key issues inhibiting broad application of foil bearings to small gas turbines. In Phase I, we will work with a small turbine engine manufacturer to define the ideal requirements for such a bearing, develop a design, fabricate a prototype, and test it in an existing room-temperature test rig. In Phase II, we will further develop the novel foil bearing concept, develop a high-temperature test rig, and retrofit a hybrid foil journal bearing to an existing small gas turbine.