Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications

Abstract

A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-stop cycles are performed on the bearing at a temperature of 425°C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.

Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications

“…It is notable that factors such as low-friction tribological coatings, effective thermal management, and highly smooth and flat surfaces have all been found to affect load capacity performance in foil thrust bearings [34], consistent with the physical interpretation of the load capacity coefficient as defined. As a result, a particular bearing design can exhibit a wide range of load capacity coefficients.…”

“…It is notable that these two bearings were only about 50% and 67% populated with top foils, however. In a more recent study with a fully populated bearing running at speeds from 25-40 krpm, Dykas [34] reports load capacities corresponding to a coefficient of 0.125 with a commercially available bearing. However, even this more recent data is obtained from a bearing design several years old, and the authors are not aware of sufficient details on the load capacities of state-of-the-art foil thrust bearings in the open literature to report currently achievable coefficients.…”

A Foil Thrust Bearing Test Rig for Evaluation of High Temperature Performance and Durability

“…However, the post-deposition grinding of the PS304 surface results in an undesirably large surface roughness of R a = 0.2 -0.8μm (8-32 μin), mostly due to the coating porosity (2). Because gas film thicknesses are generally in the 10-30 μm range, the roughness of the as-ground PS304 has been shown to result in reduced load capacity in foil bearings (6,7). As the coating is subjected to start-stop cycles with periods of sliding contact, the surface finish improves to R a =0.1 or smaller, with a corresponding increase in load capacity.…”

Development and Application of Integrated Aerodynamic Protuberant Foil Journal and Thrust Bearing in Turboexpander

“…Lee et al applied foil thrust bearing in automotive turbochargers with 24 mm diameter shaft at speed of 123000 rpm (round per minute) [20]. Dykas et al adopted foil thrust bearing in micro turbomachinery with inner diameter of 50.8 mm and outer diameter of 101.6 mm with load capacity of 125 N 2 International Journal of Rotating Machinery around 23000 rpm [21]. Kim et al evaluated the foil bearing performance in a 120 kW gas turbine generator with rated speed of 15800 rpm and generator weight of 84.2 N and turbine weight of 175.0 N [22].…”