scholarly journals Stability of rigid rotors supported by air foil bearings: Comparison of two fundamental approaches

2016 ◽  
Vol 381 ◽  
pp. 179-191 ◽  
Author(s):  
Jon S. Larsen ◽  
Ilmar F. Santos ◽  
Sebastian von Osmanski
Keyword(s):  
Foil Bearings ◽  
Rigid Rotors

Stability analysis of rigid rotors supported by gas foil bearings coupled with electromagnetic actuators

2019 ◽  
Vol 234 (2) ◽  
pp. 427-443 ◽  
Author(s):  
Kamal Kumar Basumatary ◽  
Gaurav Kumar ◽  
Karuna Kalita ◽  
Sashindra K Kakoty
Keyword(s):  
Stability Analysis ◽  
Equations Of Motion ◽  
Electromagnetic Actuator ◽  
Electromagnetic Actuators ◽  
Foil Bearings ◽  
Damping Characteristics ◽  
Foil Bearing ◽  
Model Combining ◽  
The Stability ◽  
Rigid Rotors

Rotors supported on gas foil bearings have low damping characteristics, which limits its application. A possible solution could be an integration of a gas foil bearing with an electromagnetic actuator. This paper discusses the effect of electromagnetic actuators on the stability of a rotor supported on gas foil bearings. A coupled dynamic model combining the dynamics of gas foil bearing and electromagnetic actuator has been developed. The fluid film forces from the gas foil bearings and the electromagnetic forces from the electromagnetic actuators are integrated into the equations of motion of the rotor. The sub-synchronous vibration present in case of conventional gas foil bearings is reduced and the stability band of the rotor is increased due to the implementation of electromagnetic actuator.

Experimental Analysis of the Unbalance Response of Rigid Rotors Supported on Aerodynamic Foil Bearings

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Franck Balducchi ◽  
Mihai Arghir ◽  
Romain Gauthier
Keyword(s):  
Vibration Spectrum ◽  
Rotation Speed ◽  
Nonlinear Behavior ◽  
Structural Damping ◽  
Foil Bearings ◽  
Unbalance Response ◽  
Theoretical Predictions ◽  
Air Film ◽  
Rigid Rotors ◽  
Cubic Stiffness

The paper presents the experimental unbalance response of two slightly different rigid rotors supported by aerodynamic foil bearings. Impulse (Pelton) turbines manufactured directly in the mass of the rotors (on the outer surface) entrain both rotors at rotation speeds comprised between 50 krpm and 100 krpm. The displacements in the two foil bearings are measured during coast down and are depicted as waterfall plots. They show typical nonlinear behavior, i.e., subsynchronous vibrations accompanying the synchronous component. The measurements clearly show that the subsynchronous components bifurcate or jump at typical rotation speeds (mostly rational fractions of the rotation speed). The nonlinear behavior of the rigid rotor supported on foil bearings is also emphasized by varying the added unbalance: with increasing unbalance the vibration spectrum becomes gradually more diverse as new subsynchronous vibrations appear. The experimental results are compared with very simplified theoretical predictions based on the assumption that the air film in the two bearings is infinitely stiff compared to the foil structure. The latter is characterized by a cubic stiffness and a structural damping coefficient. The comparisons show only a rough qualitative agreement.

Experimental Analysis of the Unbalance Response of Rigid Rotors Supported on Aerodynamic Foil Bearings

2014 ◽  
Author(s):  
Franck Balducchi ◽  
Mihai Arghir ◽  
Sylvain Gaudillere
Keyword(s):  
Theoretical Models ◽  
Structural Damping ◽  
Foil Bearings ◽  
Unbalance Response ◽  
Linear Behavior ◽  
Non Linear ◽  
Theoretical Predictions ◽  
Air Film ◽  
Rigid Rotors ◽  
Cubic Stiffness

The paper presents the experimental unbalance response of two slightly different rigid rotors supported by two identical aerodynamic foil bearings. Impulse (Pelton) turbines manufactured directly on the outer surface entrain both rotors at rotation speeds comprised between 50 krpm and 100 krpm. The displacements in the two foil bearings are measured during coast down and are depicted as waterfall plots. They show typical non-linear behavior, i.e. subsynchronous vibrations accompanying the synchronous component. The measurements show clearly that the subsynchronous components bifurcate at typical rotation speeds (mostly rational fractions of the rotation speed). The non-linear behavior of the rigid rotor supported on foil bearings is also underlined by varying the added unbalance: with increasing unbalance the vibration spectrum becomes gradually richer as new subsynchronous vibrations appear. The experimental results are compared with very simplified theoretical predictions based on the assumption that the air film in the two bearings is infinitely stiff compared to the foil structure. This latter is characterized by a cubic stiffness and a structural damping coefficient. The comparisons show only a rough qualitative agreement and enlighten the actual limits of foil bearings theoretical models.

Feasibility investigation of a compressor rotor supported by gas foil bearings with inhomogeneous bump foils

2021 ◽  
pp. 135065012110046
Author(s):  
Hao Li ◽  
Haipeng Geng ◽  
Bo Wang ◽  
Wei Zheng
Keyword(s):  
Critical Speed ◽  
Rotor System ◽  
Experimental Result ◽  
Test Results ◽  
Rotating Speed ◽  
Foil Bearings ◽  
Dynamic Coefficients ◽  
High Order Harmonic ◽  
Compressor Rotor ◽  
Operating Points

In this paper, a rotordynamic experiment on a compressor rotor system is presented and the feasibility of gas foil bearings with inhomogeneous bump foils is verified. A push–pull device is designed to obtain the stiffness curve and the nominal clearance of foil bearings. Operating points and dynamic coefficients of the rotor system at each rotating speed are predicted. In rotordynamic analysis, an alternative model of the impeller is proposed and the critical speed is predicted by employing the finite element method, in which the dynamic coefficients of inhomogeneous foil bearings are taken into account. Compared with the experimental result, the accuracy of the prediction for the critical speed is verified to be about 14% error. Two sets of foil bearings with 22 and 41 μm nominal clearance are manufactured and tested. Test results indicate that the vibration amplitude can be greatly reduced by diminishing the bearing clearance. When foil bearings with 22 μm clearance are used, the high-order harmonic frequencies of rotor vibration are significantly inhibited, and the amplitude of the rotating frequency is obviously restricted. Thus, the foil bearing with inhomogeneous bump foils tested in this paper can meet the speed requirement of the compressor when the nominal clearance is set at 22 μm.

scholarly journals Automatic two-plane balancing for rigid rotors

2008 ◽  
Vol 43 (6) ◽  
pp. 527-541 ◽  
Author(s):  
D.J. Rodrigues ◽  
A.R. Champneys ◽  
M.I. Friswell ◽  
R.E. Wilson
Keyword(s):  
Rigid Rotors
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