Prediction of rotor dynamic coefficients in gas lubricated foil journal bearings with corrugated sub-foils

A finite element foil bearing model that incorporates radial and circumferential deflections of a corrugated sub-foil into the prediction of rotor dynamic coefficients is presented. The corrugated sub-foil is treated as a continuous structure that supports the top-foil. Radial and circumferential deflections are coupled in the sub-foil model. The Coulomb friction between the top-foil, sub-foil, and the bearing shell is modeled as an equivalent viscous friction. The foil deflections, the film thickness, and gas pressure are then perturbed to calculate the rotor dynamic coefficients. The results are presented demonstrating the effects of frequency, orbit size, and friction coefficient on the rotor dynamic coefficients and the energy dissipation rate.