Effect of support sinusoidal motions on the vibration of an on-board rotor-bearing system

International audienceIn generator and pump rotors installed in power plants, the rotating mass unbalance and the different motions of the rotor support are among the main sources of flexural vibrations. This work aims to observe the dynamic behavior of an on-board rotor subject to rigid support movements. The modeling takes into account six types of support deterministic motions (rotational and translational motions) when the kinetic and strain energies in addition to the virtual work of the rotating flexible rotor components are calculated. The finite element method is applied using the Timoshenko beam theory. The proposed on-board rotor model considers the rotary inertia, the gyroscopic inertia, the shear deformation of shaft as well as the geometric asymmetry of shaft and/or rigid disk of the rotor. By computing the Rayleigh damping coefficients, the effect of rotor internal damping is included in the study. The Lagrange's equations are used to obtain the differential equations of the rotor in bending relative to the rigid support which forms a noninertial reference frame. The equations of motion exhibit periodic parametric coefficients due to the asymmetry of the rotor and time-varying parametric coefficients due to the support rotations. In the presented applications, the rotor mounted on rigid/elastic linear bearings is excited by a rotating mass unbalance combined with sinusoidal oscillations of the rigid support. The dynamic behavior of the rotor is analyzed by means of rotor orbits and fast Fourier transforms (FFTs)