The prediction of the non-linear dynamics of a squeeze-film damped aero-engine rotor housed in a flexible support structure

This paper shows how the non-linear dynamics of a rotor running in unsupported squeeze-film dampers (SFDs) housed in a flexible support structure can be efficiently modelled using an integrated analytical technique and a standard model for the SFDs. A test rig that reproduces, to a limited extent, the essential dynamic features of an aero-engine gas turbine is considered and the aim of the analysis is to assess the ability to predict and interpret the observed non-linear vibrations as indicated by amplitude-speed plots, frequency spectra, orbital motion plots and Poincaré maps. The solution process starts with the application of a fast harmonic balance method that uses receptance functions to determine periodic solutions. A modal-based approach is then used for the analysis of the stability and bifurcation of these solutions, as well as the analysis of aperiodic motion. The simulation correctly predicts the overall performance, including subharmonic motion, combination frequencies and subcritical superharmonic resonances.