The vibration of an aero-engine rotor incorporating two squeeze-film dampers

Virtually all previous research on the squeeze-flint damping of rotor assemblies has considered the use of only one damper. However, many aero-engine rotor assemblies have at feast two dampers and the interplay between them is an important factor in the overall vibration performance of the rotor. The purpose of this paper is to report results on a test facility which simulates the rotor of an aero-engine of the size used to power an executive jet. It draws general conclusions on the application of two squeeze-film dampers (SFDs) to such a rotor, while in the process qualitatively validating a suggested theoretical model of the SFD. The test facility is a three bearing rigid rotor assembly incorporating two sprung bearing supports, each in series with a weakly sealed squeeze-film damper. A range of practical configurations with different SFD static misalignments is studied. Non-linear jump phenomena and subharmonic resonances are demonstrated both experimentally and theoretically for a range of rotor unbalance. The paper is concerned with predicting and measuring rotor-centre responses and vibration orbits and drawing conclusions that are relevant to the designer. It forms a complement to a previous paper (1) in which spectrum analyses of vibration signatures were made.