Fengguang Xiang

Inertial loads induced by base motion excitation introduce significant complexities in equilibrium point determination and linearization of systems incorporating squeeze film dampers (SFDs). The coupled effects of base motion excitation and SFD characteristics on periodic stability have received limited attention in previous investigations. This study investigates the dynamic characteristics and periodic stability of a rotor system with SFD subjected to base motion excitation. A finite element model of the rotor-SFD-support system under non-inertial motion is established. The periodic responses are solved using the harmonic balance method with alternating frequency/time technique (HB-AFT) and the arc-length continuation algorithm incorporating the predictor–corrector method, while system stability is analyzed using Floquet theory and the Newmark method. A systematic parametric study is conducted to investigate the effects of base motion parameters, mass unbalance, and SFD parameters on the system’s periodic response. Results demonstrate that base pitching motion enhances system stability, suppresses bistable responses and jump phenomena, and reduces unstable vibration regions. However, under specific parameter combinations, pitching motion can trigger secondary Hopf bifurcations, leading to quasi-periodic and chaotic motions, among other complex nonlinear behaviors. This research provides theoretical foundations for stability-oriented design optimization of rotor systems with SFDs under base motion excitation.

When operating at high speed, aeroengines mounted on the aircrafts also perform complicated maneuvering flights along with the aircrafts. The engine rotor systems will undergo forced motions excited by base movements and mass unbalance, which may lead to severe vibrations. Squeeze film damper (SFD) is generally used for vibration damping in aeroengine, but it also introduces structural nonlinearity like bistable jump. Moreover, the reliability of SFD is also affected by base excitations. Therefore, it is necessary to investigate the nonlinear dynamic behavior of rotor-SFD-support system excited by base motions. Taking a muti-disk rotor shaft supported by two SFDs with squirrel cages as the research object to simulate a gas generator in a turboshaft engine, the steady-state responses of the rotor system were calculated by multidimensional harmonic balance combined with alternating frequency/time domain method (MHB-AFT). The effects of base harmonic rotations and mass unbalance on steady-state responses of rotor system were investigated. The results indicate that the time-varying parametric excitations of base motions have strong effects on amplitude–frequency response of transverse displacement of rotor system. The critical speeds and resonant amplitudes of responses change with the magnitude and frequency of several base harmonic rotations. The variation of the frequency of base harmonic motion has the most significant impact on the amplitude–frequency response of transverse displacement of rotor system. The increase of base harmonic frequency will lead to multiple local peaks in the response curves, especially in the case of base harmonic rolling motion. In addition, the combination of base harmonic rotation around pitching and yawing axes results in significantly different response characteristics. Therefore, the influence of base harmonic motions should be considered during the structural design and damping optimization of SFDs.