The Emergence of Compliant Foil Bearing and Seal Technologies in Support of 21^st Century Compressors and Turbine Engines

For energy independence to become a reality, whether through the more effective use of US natural resources such as natural gas or through the continued development of the hydrogen economy, efficient and reliable large-scale compressors are needed to enhance the existing pipeline infrastructure that moves energy storing gases from production sites to end user locations. Oil-free, non-contacting seal and bearing technologies are critical to the successful development of new high efficiency and power dense compressors. Similarly with increasing emphasis on energy conservation, power and propulsion gas turbine engines will require advanced low leakage seals and may take advantage of efficiencies offered by compliant foil gas bearings. When properly applied these oil-free, non contacting technologies will have a positive impact on the operating efficiency and life of compressor and gas turbine engine systems. The overall objective of this paper is to present recent advances in compliant foil bearings and seals that make them attractive for a wide array of systems. The paper documents the design approach that includes analytical trade off studies to establish overall requirements followed by an experimental program to demonstrate the ability of the identified foil technology to meet the machine requirements. A summary of advancements in foil bearing load carrying capacity, size scaling from 6 mm to 150 mm in diameter, the ability to operate under shock loads greater than 40 g as well as under steady side loads with two different gases and finally the ability to operate at temperatures greater than 750 C will be presented. Data will also be presented showing the application of foil bearings to several different machines. Similarly, results from design, fabrication and testing of compliant foil radial and axial face seals will be discussed. Data from axial face seals testing at differential pressures, surface velocities, and normal loads greater than 675 kPa, 350 m/s, and 1100 N respectively will be presented to demonstrate non-contacting performance. Results of subcomponent testing will also be presented to demonstrate the capability of the face seal to accommodate axial excursions of up to 3.8 mm. Compliant foil radial seal testing in sizes ranging from approximately 60 to 215 mm in diameter under differential pressures to 690 kPa and surface velocities to 340 m/s will be presented and compared to prediction. The culmination of the work presented supports the application of compliant foil bearings and seals in a wide array of advanced machinery.