A comprehensive study on natural characteristics and dynamic responses of a dual-rotor system with inter-shaft bearing under non-random uncertainty

Aeroengines are usually designed with a dual-rotor configuration for the rotating part. A dualrotor system has coupling characteristics introduced by an inter-shaft bearing, and the rotating direction of the rotors has critical influences on the performance. It becomes more complicated when the inevitable uncertainties of the dual-frequency excited dynamical system are considered. This paper delivers a comprehensive study of the natural characteristics and dynamic responses of a dual-rotor system with an inter-shaft bearing considering the non-random parametric uncertainties under co- and counter-rotating conditions. To this end, the finite element modeling and the deterministic solutions of a dual-rotor system are established. Then, the polynomial surrogate function is constructed for the desired natural characteristics and dynamic responses under non-random uncertainty. The polar interpolation technique is implemented to compute uncertain shaft orbits, overcoming difficulties in the traditional frequency-sense measure. Intensive case studies for different interval uncertain parameters are carried out and the results are comparatively discussed. It is found that the mass unbalance uncertainties only affect the respective modes excited by the rotor where the unbalance is located. The shaft stiffness has global uncertainty effects on the Campbell diagram, mode shapes, time history, shaft orbit and responses. Uncertainties in the inter-shaft bearing stiffness and speed ratio generally influence higher-order modes. The results of the present work gain insights into the modal characteristics and dynamical behaviors of the dual-rotor system under complex parametric uncertainties.