Vibrations Analysis of a Rotor Supported by Tilting-Pad Journal Bearings with Considering of Geometric Nonlinearity

Vibrations of a continuous rotor with uniform circular cross section supported by two tilting-pad journal bearings (TPJB) at both ends are analyzed. Since the shaft is slender, shear deformation is neglected, but, gyroscopic effect is considered (Rayleigh beam theory). In addition, geometric nonlinearity due to large deformation of the rotor is considered. Based on short bearing assumption, an analytical model of a TPJB with laminar and turbulence flow has been derived. Galerkin method is applied to discretize differential equations of motion. On mode (the first mode) is used for discretization. By solving discrete rotor-bearing system equations, the response is obtained. For further investigation, responses of rotor-bearing system in different situations are presented. Comparing the responses of the linear and nonlinear rotor with two TPJB at both ends shows that the nonlinear rotor has less amplitude than linear rotor and nonlinear rotor is closer to reality. In addition, nonlinear model has a larger natural frequency in comparison to the linear rotor. Using turbulence flow makes the bearing stiffer and have less amplitude than laminar flow. Reducing viscosity of lubricant leads to increase of amplitude of response and shows that higher viscosity make the bearing stiffer.