Innovative Bearing Concepts For High Speed Rotating Machines

System testing of an F/A-18 ACM with direct drop in replacement foil bearings was conducted demonstrating that MiTis 4th generation compliant foil bearings operating under normal conditions experienced lower temperatures than the OEM bearings and with lower turbine pressure and flow required to reach the same speed condition. In a dust environment, MiTis compliant foil bearings appeared unaffected by dust ingestion operating reliably with minimal signs of wear or damage after testing. This test series clearly shows that advancements made to foil bearing technology over the past two decades offer benefits in temperature margins, load carrying capacity and tolerance to debris.Subsequent testing to determine off gases revealed that the major compounds appear to be a mixture of carbon dioxide CO2, sulfur dioxide SO2 and fluorocarbons of varying molecular weight/boiling point. Given the demonstrated suitability for use as replacement bearings additional qualification testing is warranted to verify minimal to no harmful off gas products even during high speed engagements and to demonstrate operability under vibration conditions.Success in qualification testing will lead to expanded application of replacement foil bearings in other air cycle machines.