Dynamic behavior of a flexible rotor system with squeeze film damper considering oil-film inertia under base motions

Under parametric excitations and external forces induced by base motions, dynamic behavior of an on-board rotor system supported by squeeze film damper (SFD) considering fluid inertia was investigated. Based on perturbation method, oil-film pressure and three-dimensional velocities were represented by first-order functions of the Reynolds number. Using finite difference and numerical integration, an oil-film inertia SFD model was established to calculate pressure distribution and oil-film forces. Excited by time-varying base motions, dynamic responses and bifurcation behavior of SFD-rotor system were analyzed by Newmark-HHT method. The results indicate that when the journal whirls at a large eccentricity ratio, the pressure distribution is sensitive to oil-film inertia, reducing radial force while increasing tangential force. For high rotating speed and large eccentricity, the inertia effect dampens resonant amplitude. Under base transverse rotations, the journal's whirling orbits deviate from the bearing's center, and sub-harmonic frequencies appear with fundamental frequency. Under base harmonic translation, the journal's motion is transformed from periodic to quasi-periodic, and the stability is gradually deteriorated with harmonic frequency. Overall, a flexible approach is established to calculate dynamic behavior of SFD-rotor system considering oil-film inertia under base motions, which provides technical support for dynamic design of on-board rotor systems in gas turbines.