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N. Prechavut, H.P. Berg
Capable of high-speed and high-temperature operation, together with an "oil-free" technology concept, gas foil bearings are a perfect solution for a novel light weight (small scale) turbo machinery. While the gas film geometry and the pressure build-up are similar to other gas lubricated bearings, and as it has been well formulated in the hydrodynamic lubrication theory, the compliant structure of the foil bearings have a variety of forms and characteristics. The cantilever-type of foil bearings are one sort of foil bearings that uses a pattern of small cantilever beams as support structure which is very robust and eases the manufacturing process. The aim of this paper is to present a measurement method and results of structural stiffness and damping characteristics of exemplary 50 mm tree-lobes radial foil bearings. Static structural test result shows that the bearing has a wide range of linear stiffness in the bearing's center area. The ramp of cartridge inner surface contour causes a cross coupling effect which may cause instability by a large rotor orbit. Increasing in bearing preload result in slightly increasing in static stiffness. In dynamic excitation test, the result shows that the dynamic stiffness is about three times higher than the static one. With a simple model of dry friction, the result shows that the dry friction coefficient is in a range of 0.4 to 0.7. The result also shows that the dynamic stiffness is more sensitive to vibration amplitude than frequency. While the damping decreases significantly with exciting frequency, especially at the vicinity of the rigid body resonance. The result evidence that the magnitude of displacement has a great effect on damping. As displacement amplitude decreases, the bearing is better in damping.
Deutscher Luft- und Raumfahrtkongress 2015, Rostock
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2015
21,0 x 29,7 cm, 10 Seiten
Stichworte zum Inhalt:
foil bearings, structural stiffness