Fluid Forces as an Additional Source of Vibration in a Rotor-Stator Rub System (Part I)

The effects of the hydrodynamic forces as an additional source of vibration in a rotor-stator rubbing system are discussed in this paper. The full governing equations of the coupled lateral and torsional vibrations of a rotor in recurrent rubbing contact with a fixed stator are established based on Energy Principle. The hydrodynamic forces simulating the fluid resistance to the rotor motion are introduced into the system and yield a strong coupled nonlinear rotor system equation. A significant effect of the fluid mass and some of the nonlinear interaction effects appeared in a derived equation. The rotor system is simulated for rubs detection purposes in an inviscid fluid medium. The motion of the unsteady fluid-rotor interaction is analyzed under unbalance and shock-impact of the rotating system using frequency spectrum and Wavelet Synchrosqueezing techniques. The results revealed that the fluid is responsible for decreasing the magnitude rubbing contact and the strong attenuation of the signal's frequency spectrum. The system's response has shown that the fluctuating hydrodynamic forces are among the causes of the system disturbance. For validation purposes, the study could further be a subject of experimentation for rotor condition monitoring strategies to provide insight into fluid forces' influences in a rubbing system.