Experimental Validation of Theoretical Models for the Linear and Nonlinear Vibrations of Immersed Rotors

M. MOREIRA ； A. TISSOT ； J. ANTUNES

《International Journal of Rotating Machinery》 2002卷 (2002/12) Pp. 87-98

https://doi.org/10.1155/S1023621X0200009X

摘要

Vibration of rotating shafts has been studied for different gap geometries, ranging from bearing configurations to pump systems. This paper deals with the rotor-flow dynamics of immersed shafts under moderate confinement - clearance gap about δ=H/R=0.1 (where H is the average gap and R is the rotor radius). Following simplified assumptions, analytical models for the linearized forces, for both centered and eccentric immersed rotors have been developed as well as a theoretical nonlinear model which fully describes the nonlinear flow terms. These models were supported by encouraging results from preliminary experiments. In the present paper, we discuss some recent and representative results of an extensive series of tests performed on a small-scale model, in order to assert the validity of our theoretical models. From the overall experimental programma, the following conclusions emerged: (1) The linearized bulk-flow model is adequate, provided the dissipative effects are duly accounted for using an empirical friction coefficient to empirically model the turbulent stresses. Such predictions are quite accurate if the system is working at low rotor eccentricities and far from the instability boundaries. (2) However, for large rotor eccentricities and for dynamic regimes near the linear instability, the fully nonlinear model leads to better predictions. Obviously, these effects are instrumental to obtaining reasonable predictions for all post-stable motion regimes. (3) When discrepancies arise, the nonlinear model was usually found to be conservative.

關鍵字

Rotor vibrations ； Nonlinear dynamics ； Flow-structure interaction ； Experimental identification