| In this study, a finite element dynamic model of rotor-disk-bearing system was developed using Timoshenko beam theory to incorporate shear deformation and rotary inertia. Each shaft element includes unbalance and gyroscopic effects as well as structural damping. The hydrodynamic bearing system was modeled, damping and stiffness parameters were obtained, using standard Reynolds equation solution for short bearing with half film pressure profile and Sommerfeld static eccentricity. The Reynolds equation was then solved for the case of dynamic loading for which a closed loop interaction between the shaft center position and bearing equations was derived. Lastly, the whole bearing system of equations was solved using finite series solution in rotating coordinate system that rotates at fluid circumferential velocity. With this solution the study included the effects of fluid inertia as well as dynamic eccentricity or shaft position. The study showed that bearing displacements have much slower decay rate and clearer effect of disk unbalance when dynamic eccentricity and fluid inertia are included in the closed loop rotor-bearing system. |
