NDLI: Bump-Type Foil Bearing Structural Stiffness: Experiments and Predictions

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Rubio, Dario Andres, Luis San
Copyright Year	2004
Abstract	Gas foil bearings (FB) satisfy many of the requirements noted for novel oil-free turbomachinery. However, FB design remains largely empirical, in spite of successful commercial applications. The mechanical structural characteristics of foil bearings, namely stiffness and damping, have been largely ignored in the archival literature. Four commercial bump-type foil bearings were acquired to measure their load capacity under conditions of no shaft rotation. The test bearings contain a single Teflon coated foil supported on 25 bumps. The nominal radial clearance is 0.036 mm for a 38 mm journal. A simple test set up was assembled to measure the FB deflections resulting from static loads. The tests were conducted with three shafts of increasing diameter to induce a degree of preload into the FB structure. Static measurements show nonlinear FB deflections, varying with the orientation of the load relative to the foil spot weld. Loading and unloading tests evidence hysteresis. The FB structural stiffness increases as the bumps-foil radial deflection increases (hardening effect). The assembly preload results in notable stiffness changes, in particular for small radial loads. A simple analytical model assembles individual bump stiffnesses and renders predictions for the FB structural stiffness as a function of the bump geometry and material, dry-friction coefficient, load orientation, clearance and preload. The model predicts well the test data, including the hardening effect. The uncertainty in the actual clearance (gap) upon assembly of a shaft into a FB affects most the predictions.
Sponsorship	International Gas Turbine Institute
Starting Page	671
Ending Page	679
Page Count	9
File Format	PDF
ISBN	0791841715
DOI	10.1115/GT2004-53611
e-ISBN	0791837394
Volume Number	Volume 6: Turbo Expo 2004
Conference Proceedings	ASME Turbo Expo 2004: Power for Land, Sea, and Air
Language	English
Publisher Date	2004-06-14
Publisher Place	Vienna, Austria
Access Restriction	Subscribed
Subject Keyword	Damping Uncertainty Deflection Bearings Clearances (engineering) Turbomachinery Rotation Foil bearings Stress Dry friction Design Geometry Hardening Stiffness Manufacturing
Content Type	Text
Resource Type	Article

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