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Structures and Materials Division Research and Technology Directorate NASA Glenn Research Center

Tribology and mechanical Components Branch
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Oil-Free Turbomachinery - Foil Bearings
Foil bearings are self-acting hydrodynamic bearings that use ambient air as the lubricant. They operate at high speeds (no diameter x speed (DN) limit) with a broad temperature range and tolerate misalignment and distortion.Analytical methods provide the opportunity to evaluate, refine, and optimize new designs in advance of hardware fabrication.

Foil bearing diagram

A journal foil bearing will support about one pound
  • per square inch of projected area, LxD
  • 200 to 1200 °F. per inch of bearing diameter, D
  • per thousand rpm, N
    Load = Dj(LxD)xDxN
Large Diameter foil bearings and journal bearing shafts
Above: Large Diameter foil bearings and journal bearing shafts

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Enabling Technologies
Finite element model of oil-free turbocharger rotor
Analytical Modeling

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Oil-free PM304 lubricant
Tribological Coatings

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Foil bearing operating at high temperature
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Last Updated: April 21, 2009