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.

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.

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.

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.

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.

The Control of Engine Vibration Using Squeeze Film Dampers

1983 ◽  
Vol 105 (3) ◽  
pp. 525-529 ◽  
Author(s):  
R. Holmes
Keyword(s):  
Experimental Work ◽  
Squeeze Film ◽  
Vibration Isolator ◽  
Squeeze Film Damper ◽  
Engine Vibration ◽  
Transmitted Force ◽  
Squeeze Film Dampers ◽  
Jump Phenomena ◽  
Theoretical Predictions ◽  
In Series

This paper describes the following roles of a squeeze-film damper when used in gas turbine applications as a means of reducing vibration and transmitted force due to unbalance: (a) as an element in parallel with a soft spring in a vibration isolator; and (b) as an element in series with the stiffness of the engine pedestal. The effects of cavitation on performance are elucidated, and the dangers of jump phenomena and subsynchronous response are discussed. Experimental work is described in which both roles of the squeeze-film damper are investigated and the results are compared with theoretical predictions.

The Effect of Bistable Jump on the Reliability of Squeeze Film Damper

1991 ◽  
Author(s):  
Zhu Changsheng
Keyword(s):  
High Speed ◽  
Operating Time ◽  
Squeeze Film ◽  
Jump Phenomenon ◽  
Rotor Vibration ◽  
Squeeze Film Damper ◽  
Operation Speed ◽  
Squeeze Film Dampers ◽  
Speed Range ◽  
Pass Through

Abstract Based on lots of data from an experiment of a high-speed rotor supported on squeeze film dampers, this paper analyses that how the bistable jump affects the reliability of squeeze film dampers, if the rotor system has to frequently pass through the bistable oparation speed range. It is shown that the change of the rotor vibration amplitudes caused by times of passed through bistable operation speed range is more significant than that caused by steady operating time. The users must pay much attention to the bistable jump phenomenon in the successful application of squeeze film dampers.

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.

scholarly journals Stability Analysis of a Gear Pair System Supported by Squeeze-Film Dampers

2001 ◽  
Vol 7 (2) ◽  
pp. 143-151 ◽  
Author(s):  
T. N. Shiau ◽  
J. R. Chang ◽  
S. T. Choi
Keyword(s):  
Steady State ◽  
Stability Analysis ◽  
Harmonic Balance Method ◽  
Squeeze Film ◽  
Hybrid Technique ◽  
Gear Pair ◽  
Mesh Stiffness ◽  
Gear Mesh ◽  
Squeeze Film Dampers ◽  
The Stability

This paper examines the stability of the steady-state periodic response of a gear pair system supported by squeeze-film dampers. The steady-state response of the system is obtained by using the hybrid technique of Harmonic Balance Method and Time Collocation. The Fioquet-Liapunov theory is used to perform the stability analysis of the first variation equations with periodic coefficients, which is generated by the perturbation technique. The stability charts on gear mesh stiffness, spin ratio, disk unbalance, gravity, and squeeze-film damper are used to perform parameter studies. The numerical results show that the unstable region always occurs when the spin ratio is near the second coupled mode of the gear pair system. Furthermore, the mesh stiffness has a significant influence on the coupled critical speeds. Therefore, it plays an important role in determining the spin ratio stability range.

scholarly journals The Control of Engine Vibration Using Squeeze-Film Dampers

1982 ◽  
Author(s):  
R. Holmes
Keyword(s):  
Experimental Work ◽  
Squeeze Film ◽  
Vibration Isolator ◽  
Squeeze Film Damper ◽  
Engine Vibration ◽  
Transmitted Force ◽  
Squeeze Film Dampers ◽  
Jump Phenomena ◽  
Theoretical Predictions ◽  
In Series

This paper describes the following roles of a squeeze-film damper when used in gas turbine applications as a means of reducing vibration and transmitted force due to unbalance. (a) as an element in parallel with a soft spring in a vibration isolator and (b) as an element in series with the stiffness of the engine pedestal. The effects of cavitation on performance are elucidated and the dangers of jump phenomena and subsynchronous response are discussed. Experimental work is described in which both roles of the squeeze-film damper are investigated and the results are compared with theoretical predictions.

Sign in / Sign up

Export Citation Format

Share Document