Bifurcations of a flexible rotor response in squeeze-film dampers without centering springs

Squeeze-film dampers are often utilized in high-speed rotating machinery to provide additional external damping to the rotor-bearing system for the purpose of reducing the synchronous response of the rotor especially while traversing critical speeds, or to eliminate rotor instability problems. The application of these dampers are widely found in aircraft gas turbine engines that are usually mounted on rolling element bearings, which are known to provide almost negligible damping to the system. Although the squeeze-film damper is an inherently stable machine element, its operation at certain parameters may give rise to undesirable non-synchronous vibration. The effects of the design and operating parameters, namely the bearing parameter, B, gravity parameter, W, and mass ratio, α, on the bifurcations in the response of a flexible rotor supported by squeeze-film dampers without centering springs were examined using direct numerical integration. Specifically, the effects of these parameters on the onset speed of bifurcation and the extent of non-synchronous response of the rotor within the range of speed parameter, Ω, between 0.5 and 5.0 were determined.