Finite Element Approach to the Prediction of Foil Bearing Rotor Dynamic Coefficients

A finite element perturbation approach to the prediction of foil bearing stiffness and damping coefficients is presented. The fluid lubricant is modeled as a simple barotropic fluid which is described by the Reynolds equation. The structural model includes membrane, bending, and elastic foundation effects in a general geometry. The equivalent viscous damping of the Coulomb friction caused by the foil relative motion is included in the structural calculation. Bearing stiffness and damping coefficients are predicted for an air-lubricated foil bearing with a corrugated sub-foil. The effects of the bearing number, bearing compliance, sub-foil Coulomb friction, and foil membrane stiffness on the bearing dynamic coefficients are discussed.

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