The purpose of this study is to explore the limiting stiffness coefficients of a foil journal bearing with the texture bump profile of top foil. The limiting stiffness coefficients are evaluated based on simplified compressible Reynolds equation for large bearing numbers with high speeds of foil journal bearing. A limiting pressure gradient solution for a texture bump of top foil bearing is analyzed. The analytical model accounts for the top foil texture bump profile and bottom foil bump compliance. Results of linearized nondimensional stiffness coefficients obtained using infinitesimal perturbation method are compared for various top foil texture bump profiles. The influence of top foil texture bump extent and height on the limiting stiffness coefficients of a foil journal bearing are investigated.
This work involves model‐based identification of rotor crack. A Laval rotor with a transverse surface crack and disc unbalance is studied. Viscous damping, disc eccentricity and additive stiffness due to crack are the parameters considered for identification. The linear system equations of motion together with the switching crack excitation function are used for developing the identification algorithm. Furthermore, the algorithm is extended for a novel attempt of estimating the coefficients of switching crack excitation function, which constitute the crack excitation force. This estimation could be used to provide valuable information on the actual opening/closing profile of the switching crack. The proposed algorithms are illustrated through numerical examples. They are tested against measurement noise and found to be reasonably robust.
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