Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors

2004 ◽  
Vol 126 (4) ◽  
pp. 848-854 ◽  
Author(s):  
Ilmar F. Santos ◽  
Rodrigo Nicoletti ◽  
Alexandre Scalabrin
Keyword(s):  
Load Condition ◽  
Squeeze Film ◽  
Design Solution ◽  
Maximum Speed ◽  
Stability Margins ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
The Stability

In this paper the complete set of modified Reynolds’ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a maximum speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high maximum continuous speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e., using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.

Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors

2003 ◽  
Author(s):  
Ilmar F. Santos ◽  
Rodrigo Nicoletti ◽  
Alexandre Scalabrin
Keyword(s):  
Load Condition ◽  
Squeeze Film ◽  
Design Solution ◽  
Maximum Speed ◽  
Stability Margins ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Tilting Pad Bearings ◽  
The Stability

In this paper the complete set of modified Reynolds’ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld number, as it would be the case of conventional hydrodynamic bearings, but they are also dependent on the excitation frequencies and gains of the control loop. Stiffness as well as damping coefficients can be strongly influenced by the choice of the control strategy, servo valve dynamics and geometry of the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a maximum speed of 10,200 rpm, are analyzed. In the original compressor design, the bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high maximum continuous speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically investigated in the present paper, i.e. using actively lubricated bearings. By choosing a suitable set of control gains, it is possible not only to increase the stability of the rotor-bearing system, but also enlarge its operational frequency range.

Experiments on the Dynamic Behavior of a Supercritical Rotor

1982 ◽  
Vol 104 (2) ◽  
pp. 364-369
Author(s):  
M. Botman ◽  
M. A. Samaha
Keyword(s):  
Strain Energy ◽  
Squeeze Film ◽  
Maximum Speed ◽  
Stability Behavior ◽  
Squeeze Film Dampers ◽  
Rolling Element ◽  
Speed Range ◽  
In Series ◽  
The Stability ◽  
Desirable Effect

Tests have been performed on supercritical rotors to determine the sensitivity to unbalance and the suitability of balancing techniques. Results are presented for a rotor with an overhanging disk and supported on two rolling element bearings in series with squeeze-film dampers. The rotor has two flexural modes with high relative strain energy in the speed range up to 55,000 rpm. After completion of the balancing exercise the rotor could be run to maximum speed and was found to be stable and free from half-frequency whirl instability, depending on the oil inlet pressure of the dampers. Pressurization of the dampers and increasing the clearance of the dampers had a very desirable effect on the stability behavior and the unbalance response.

Subharmonic and Quasi-Periodic Motions of an Eccentric Squeeze Film Damper-Mounted Rigid Rotor

1994 ◽  
Vol 116 (3) ◽  
pp. 357-363 ◽  
Author(s):  
J. Y. Zhao ◽  
I. W. Linnett ◽  
L. J. McLean
Keyword(s):  
Numerical Integration ◽  
Least Square ◽  
Harmonic Series ◽  
Squeeze Film ◽  
Maximum Speed ◽  
Rigid Rotor ◽  
Squeeze Film Damper ◽  
Squeeze Film Dampers ◽  
The Stability ◽  
Nonsynchronous Vibrations

When a squeeze-film damper is operated eccentrically, the nonlinear damper forces are no longer radially symmetric and subharmonic and quasi-periodic vibrations may be excited by the rotor unbalance. In this study, the unbalance response of a rigid rotor, supported on an eccentric squeeze film damper, is first approximated by a harmonic series whose coefficients are determined by the collocation method, together with a nonlinear least-square regression. The stability of the resulting periodic solution is then examined using the Floquet transition matrix method. For sufficiently large values of the unbalance and the damper static radial misalignment, it is shown that the approximate harmonic motion loses its stability and bifurcates into a stable subharmonic motion and a quasi-periodic motion at speeds above twice the system critical speed. This analytical finding is verified by a numerical integration in forms of the Poincare´ map, the rotor trajectory, the bifurcation diagram, and the power spectrum. It is suggested that stability analysis and numerical integration should always be incorporated into an approximate analytical method to achieve an adequate approximation. The results of this study show that the introduction of squeeze-film dampers may give rise to the undesirable nonsynchronous vibrations, which limits the maximum speed at which dampers should be used.

Imbalance Response of a Rotor Supported on Flexure Pivot Tilting Pad Journal Bearings in Series With Integral Squeeze Film Dampers

2001 ◽  
Author(s):  
Luis San Andrés ◽  
Oscar De Santiago
Keyword(s):  
Peak Amplitude ◽  
Squeeze Film ◽  
Critical Speeds ◽  
Rotor Imbalance ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
In Series ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearings

Measurements of the imbalance responses of a massive 45 kg rotor supported on series (flexure pivot) tilting pad bearings and integral squeeze film dampers (SFDs) are presented. The rotor-bearing configuration is of interest in compressor applications where often oil lubricated dampers are introduced in series with fluid film bearings to relocate critical speeds, enhance the overall system damping, and reduce the risks of rotordynamic instabilities due to seals and impellers, for example. Coast-down experiments from 9,000 rpm are conducted for increasing levels of rotor imbalance, and equivalent system damping coefficients identified from the peak amplitude of rotor response while traversing cylindrical mode critical speeds. The tests performed with locked (inactive) and active SFDs demonstrate the effectiveness of the flexible damped support in reducing the system critical speed and improving the overall rotor response with reduced transmitted forces to ground. The SFDs allow safe rotor operation with values of imbalance twice as large as the maximum sustained by the rotor supported on tilting pad bearings alone. The experiments reveal a linear relationship between the peak amplitude of vibration at the critical speeds and the imbalance displacement, even for rotor motions larger than 50% of the tilting pad bearing and damper clearances. The tests also show little cross-coupling effects with the shaft centerline moving along a nearly vertical path. The rotor-bearing system remained stable in the entire range of operation and without the appearance of subsynchronous vibration or non-linear damper jump response.

Imbalance Response of a Rotor Supported on Flexure Pivot Tilting Pad Journal Bearings in Series With Integral Squeeze Film Dampers

2003 ◽  
Vol 125 (4) ◽  
pp. 1026-1032 ◽  
Author(s):  
L. San Andre´s ◽  
O. De Santiago
Keyword(s):  
Peak Amplitude ◽  
Squeeze Film ◽  
Critical Speeds ◽  
Rotor Imbalance ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
In Series ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearings

Measurements of the imbalance responses of a massive 45 kg rotor supported on series (flexure pivot) tilting pad bearings and integral squeeze film dampers (SFDs) are presented. The rotor-bearing configuration is of interest in compressor applications where often oil lubricated dampers are introduced in series with fluid film bearings to relocate critical speeds, enhance the overall system damping, and reduce the risks of rotordynamic instabilities due to seals and impellers, for example. Coast-down experiments from 9000 rpm are conducted for increasing levels of rotor imbalance, and equivalent system damping coefficients identified from the peak amplitude of rotor response while traversing cylindrical mode critical speeds. The tests performed with locked (inactive) and active SFDs demonstrate the effectiveness of the flexible damped support in reducing the system critical speed and improving the overall rotor response with reduced transmitted forces to ground. The SFDs allow safe rotor operation with values of imbalance twice as large as the maximum sustained by the rotor supported on tilting pad bearings alone. The experiments reveal a linear relationship between the peak amplitude of vibration at the critical speeds and the imbalance displacement, even for rotor motions larger than 50% of the tilting pad bearing and damper clearances. The tests also show little cross-coupling effects with the shaft centerline moving along a nearly vertical path. The rotor-bearing system remained stable in the entire range of operation and without the appearance of subsynchronous vibration or nonlinear damper jump response.

scholarly journals Analytical and Experimental Investigation of the Stability of the Rotor-Bearing System of a New Small Turbocharger

1987 ◽  
Author(s):  
H. R. Born
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stability ◽  
Squeeze Film ◽  
Test Results ◽  
Flow Capacity ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
The Stability ◽  
Turbine Design ◽  
Bearing System

This paper presents an overview of the development of a reliable bearing system for a new line of small turbochargers where the bearing system has to be compatible with a new compressor and turbine design. The first part demonstrates how the increased weight of the turbine, due to a 40 % increase in flow capacity, influences the dynamic stability of the rotor-bearing system. The second part shows how stability can be improved by optimizing important floating ring parameters and by applying different bearing designs, such as profiled bore bearings supported on squeeze film dampers. Test results and stability analyses are included as well as the criteria which led to the decision to choose a squeeze film backed symmetrical 3-lobe bearing for this new turbocharger design.

scholarly journals A computational fluid dynamics investigation of the segmented integral squeeze film damper

2019 ◽  
Vol 254 ◽  
pp. 08005 ◽  
Author(s):  
Petr Ferfecki ◽  
Jaroslav Zapoměl ◽  
Marek Gebauer ◽  
Václav Polreich ◽  
Jiří Křenek
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Ansys Cfx ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Vibration Attenuation ◽  
Tilting Pad Journal Bearing

Rotor vibration attenuation is achieved with damping devices which work on different, often mutually coupled, physical principles. Squeeze film dampers are damping devices that have been widely used in rotordynamic applications. A new concept of a 5-segmented integral squeeze film damper, in which a flexure pivot tilting pad journal bearing is integrated, was investigated. The damper is studied for the eccentric position between the outer and inner ring of the squeeze film land. The ANSYS CFX software was used for solving the pressure and velocity distribution. The development of the complex three-dimensional computational fluid dynamics model of the squeeze film damper, learning more about the effect of the forces in the damper, and the knowledge about the behaviour of the flow are the principal contributions of this article.

Stability of Rotor-Bearing Systems With Generalized Support Flexibility and Damping and Aerodynamic Cross-Coupling

1975 ◽  
Vol 97 (3) ◽  
pp. 461-469 ◽  
Author(s):  
R. E. Warner ◽  
A. I. Soler
Keyword(s):  
Cross Coupling ◽  
Frequency Dependent ◽  
Oil Film ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Single Mass ◽  
Tilting Pad Bearings

This paper examines stability of the flexible single mass rotor, acted on by motion induced forces due to aero-dynamic cross-coupling and supported most generally by oil film tilting pad bearings which are in turn mounted on flexible, damped supports. Plotted results include the frequency dependent spring and damping coefficients for the 4-pad tilting pad bearing, damping coefficients for the 360-deg squeeze bearing and stability plots of rotor-bearing systems including aerodynamic cross-coupling, the 4-pad tilting pad bearing and the 150-deg partial arc bearing with various support arrangements.

Compliant Hybrid Gas Bearing Using Integral Hermetically Sealed Squeeze Film Dampers

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Bugra Ertas
Keyword(s):  
Squeeze Film ◽  
Force Coefficients ◽  
Overall Design ◽  
Single Piece ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Support Force ◽  
Bearing Design ◽  
Gas Bearing ◽  
Gaining Insight

AbstractThis paper focuses on an integral gas-film lubricated bearing concept developed to enable the oil-free operation of super-critical carbon dioxide (sCO2) turbomachinery. The externally pressurized tilting pad bearing concept possesses a flexible bearing support with an integral hermetically sealed squeeze film damper. Unlike the past concepts using modular hermetic squeeze film dampers presented, the bearing design in this work utilizes advanced manufacturing methods to yield an integral single piece design in efforts to reduce space envelope, cost, and improve overall design reliability. The paper advances a detailed description of the bearing design and identification of bearing support force coefficients. Nonrotating benchtop tests show the influence of vibration amplitude, frequency, and damper cavity pressurization on force coefficients for two different viscosity fluids. Results indicate an increase in stiffness and a decrease in damping when increasing the frequency of excitation. Damper cavity pressurization was shown to eliminate squeeze film cavitation for the vibration amplitudes and frequency range in the study. Additionally, the paper advances a transient fluid–structure interaction (FSI) analysis aimed at gaining insight on the interaction of flexible elements bounding a hermetic fluid volume experiencing sinusoidal vibratory motion. The analysis considers an idealized damper model with and without a vibration transmission post while varying diaphragm modulus of elasticity for three excitation frequencies. Computational results were able to capture the increase in stiffness and the decrease in damping and show that the flexibility of the bounding elements influence the damper cavity volume change and phase ultimately affecting dynamic cavity pressures and force coefficients.

Analysis and Experimental Investigation of the Stability of Intershaft Squeeze Film Dampers—Part 2: Control of Instability

1978 ◽  
Vol 100 (3) ◽  
pp. 558-562 ◽  
Author(s):  
D. H. Hibner ◽  
P. N. Bansal ◽  
D. F. Buono
Keyword(s):  
Experimental Investigation ◽  
Stability Analysis ◽  
Shear Deformation ◽  
System Stability ◽  
Squeeze Film ◽  
Viscous Damper ◽  
Test Rig ◽  
Squeeze Film Dampers ◽  
Stability Maps ◽  
The Stability

The results of an analytical and experimental investigation showing the existence of an intershaft viscous damper instability were presented in reference [1]. In the present investigation, a more comprehensive stability analysis is used to study the stability of the test rig which incorporates a modified intershaft bearing support. The analysis is applicable to large multi-mass, rotor-bearing systems and includes the effects of gyroscopic moments, shear deformation, bearing support flexibility, and damping. The results of the stability analysis are presented in the form of system stability maps which clearly indicate the effectiveness of the modification in improving the instability onset speed of the system. Also presented are the results of an experimental investigation which substantiate the analytical predictions.

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