The Vibration of an Aero-Engine Rotor Incorporating Two Squeeze-Film Dampers

1996 ◽  
Vol 210 (1) ◽  
pp. 39-51 ◽  
Author(s):  
R Holmes ◽  
J E H Sykes
Keyword(s):  
Test Facility ◽  
Squeeze Film ◽  
Squeeze Film Dampers ◽  
Aero Engine ◽  
In Series ◽  
Rotor Assembly ◽  
Vibration Signatures ◽  
Vibration Performance ◽  
Subharmonic Resonances ◽  
Engine Rotor

Virtually all previous research on the squeeze-film damping of rotor assemblies has considered the use of only one damper. However, many aero-engine rotor assemblies have at least two dampers and the interplay between them is an important factor in the overall vibration performance of the rotor. The purpose of this paper is to report results on a test facility which simulates the rotor of an aero-engine of the size used to power an executive jet. It draws general conclusions on the application of two squeeze-film dampers (SFDs) to such a rotor, while in the process qualitatively validating a suggested theoretical model of the SFD. The test facility is a three bearing rigid rotor assembly incorporating two sprung bearing supports, each in series with a weakly sealed squeeze-film damper. A range of practical configurations with different SFD static misalignments is studied. Non-linear jump phenomena and subharmonic resonances are demonstrated both experimentally and theoretically for a range of rotor unbalance. The paper is concerned with predicting and measuring rotor-centre responses and vibration orbits and drawing conclusions that are relevant to the designer. It forms a complement to a previous paper (1) in which spectrum analyses of vibration signatures were made.

Non-Linear Phenomena in Aero-Engine Rotor Vibration

1989 ◽  
Vol 203 (1) ◽  
pp. 25-34 ◽  
Author(s):  
R Holmes ◽  
M M Dede
Keyword(s):  
Frequency Response ◽  
Test Facility ◽  
Medium Size ◽  
Rotor Vibration ◽  
Jet Engine ◽  
Aero Engine ◽  
Non Linear ◽  
Rotor Assembly ◽  
Twin Rotor ◽  
Engine Rotor

This paper describes a test facility which reproduces the essential features of a twin-rotor assembly for a medium-size jet engine. Its purpose is to investigate phenomena experienced in an actual engine, which relate to system non-linearities. These phenomena include subharmonics, combination oscillations and jumps in frequency response. All such phenomena manifested themselves in the test facility and explanations are given as to their cause and possible elimination.

Experimental Evaluation of a Metal Mesh Bearing Damper

2000 ◽  
Vol 122 (2) ◽  
pp. 326-329 ◽  
Author(s):  
Mark Zarzour ◽  
John Vance
Keyword(s):  
Elevated Temperatures ◽  
Test Facility ◽  
Squeeze Film ◽  
Gas Generator ◽  
Metal Mesh ◽  
Previous Investigator ◽  
Spreadsheet Program ◽  
Squirrel Cage ◽  
Power Turbine ◽  
Squeeze Film Dampers

Metal mesh is a commercially available material used in many applications including seals, heat shields, filters, gaskets, aircraft engine mounts, and vibration absorbers. This material has been tested by the authors as a bearing damper in a rotordynamic test rig. The test facility was originally used to support the design of a turboprop engine, developing squirrel cages and squeeze film dampers for both the gas generator and power turbine rotors. To design the metal mesh damper, static stiffness and dynamic rap test measurements were first made on metal mesh samples in a specially designed nonrotating test fixture. These property tests were performed on samples of various densities and press fits. One sample was also tested in an Instron machine as an ancillary and redundant way to determine the stiffness. Using the stiffness test results and equations derived by a previous investigator, a spreadsheet program was written and used to size metal mesh donuts that have the radial stiffness value required to replace the squirrel cage in the power turbine. The squirrel cage and squeeze film bearing damper developed for the power turbine rotor was then replaced by a metal mesh donut sized by the computer code. Coast down tests were conducted through the first critical speed of the power turbine. The results of the metal mesh tests are compared with those obtained from previous testing with the squeeze film damper and show that the metal mesh damper has the same damping as the squeeze film at room temperature but does not lose its damping at elevated temperatures up to 103°C. Experiments were run under several different conditions, including balanced rotor, unbalanced rotor, heated metal mesh, and wet (with oil) metal mesh. The creep, or sag, of the metal mesh supporting the rotor weight was also measured over a period of several weeks and found to be very small. Based on these tests, metal mesh dampers appear to be a viable and attractive substitute for squeeze film dampers in gas turbine engines. The advantages shown by these tests include less variation of damping with temperature, ability to handle large rotor unbalance, and the ability (if required) to operate effectively in an oil free environment. Additional testing is required to determine the endurance properties, the effect of high impact or maneuver loads, and the ability to sustain blade loss loads (which squeeze films cannot handle). [S0742-4795(00)01002-4]

Experimental Evaluation of a Metal Mesh Bearing Damper

1999 ◽  
Author(s):  
Mark Zarzour ◽  
John Vance
Keyword(s):  
Elevated Temperatures ◽  
Test Facility ◽  
Squeeze Film ◽  
Gas Generator ◽  
Metal Mesh ◽  
Previous Investigator ◽  
Spreadsheet Program ◽  
Squirrel Cage ◽  
Power Turbine ◽  
Squeeze Film Dampers

Metal mesh is a commercially available material used in many applications including seals, heat shields, filters, gaskets, aircraft engine mounts, and vibration absorbers. This material has been tested by the authors as a bearing damper in a rotordynamic test rig. The test facility was originally used to support the design of a turboprop engine, developing squirrel cages and squeeze film dampers for both the gas generator and power turbine rotors. To design the metal mesh damper, static stiffness and dynamic rap test measurements were first made on metal mesh samples in a specially designed nonrotating test fixture. These property tests were performed on samples of various densities and press fits. One sample was also tested in an Instron machine as an ancillary and redundant way to determine the stiffness. Using the stiffness test results and equations derived by a previous investigator, a spreadsheet program was written and used to size metal mesh donuts that have the radial stiffness value required to replace the squirrel cage in the power turbine. The squirrel cage and squeeze film bearing damper developed for the power turbine rotor was then replaced by a metal mesh donut sized by the computer code. Coast down tests were conducted through the first critical speed of the power turbine. The results of the metal mesh tests are compared with those obtained from previous testing with the squeeze film damper and Show that the metal mesh damper has the same damping as the squeeze film at room temperature but does not lose its damping at elevated temperatures up to 103 °C. Experiments were run under several different conditions, including balanced rotor, unbalanced rotor, heated metal mesh, and wet (with oil) metal mesh. The creep, or sag, of the metal mesh supporting the rotor weight was also measured over a period of several weeks and found to be very small. Based on these tests, metal mesh dampers appear to be a viable and attractive substitute for squeeze film dampers in gas turbine engines. The advantages shown by these tests include less variation of damping with temperature, ability to handle large rotor unbalance, and the ability (if required) to operate effectively in an oil free environment. Additional testing is required to determine the endurance properties, the effect of high impact or maneuver loads, and the ability to sustain blade loss loads (which squeeze films cannot handle).

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.

Vibration Control of a Rotor System Utilizing a Bearing Housing With Controllable Spring Nonlinearity

1994 ◽  
Author(s):  
Baojiang Liu ◽  
Litang Yan ◽  
Qihan Li ◽  
Zigen Zhu
Keyword(s):  
Vibration Control ◽  
Nonlinear Vibration ◽  
Dynamic Behaviour ◽  
Rotor System ◽  
Experimental Results ◽  
Squeeze Film ◽  
Solution Curve ◽  
Operating Process ◽  
Squeeze Film Dampers ◽  
Vibration Performance

On the basis of characteristics of vibration in the rotor system with spring nonlinearity, a new method for vibration control has been developed. In the method, the spring characteristics of a bearing housing are controlled to be of softening nonlinearity when the rotor supported on it is accelerated and to be of hardening one when it is decelerated. So vibratory amplitudes of the rotor system always vary along the smallest solution curve in the whole operating process. A model of vibration of the rotor system supported on the controllable hearing housing is derived. Its dynamic behaviour is predicted and verified by experiments. Both theoretical and experimental results show that not only vibratory amplitudes and transmitted forces are suppressed significantly but also nonlinear vibration performance of the rotor supported on squeeze film dampers, such as “lock up” at rotor pin-pin critical speeds and asynchronous vibration, can be avoided.

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.

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.

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.

Experimental Analysis of Damper Behavior of Squeeze Film Dampers for Gas Turbine Engines

1985 ◽  
Vol 107 (1) ◽  
pp. 165-169
Author(s):  
S. C. Kaushal ◽  
V. A. Kumar ◽  
K. Lakshmikantan
Keyword(s):  
Gas Turbine ◽  
Excitation Frequency ◽  
Squeeze Film ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Turbine Engine ◽  
Evaluation Of Performance ◽  
Squeeze Film Dampers ◽  
Overall Performance ◽  
Rotor Assembly

This paper discusses the experimental evaluation of performance of squeeze film dampers without centralizing retaining springs. Rotor amplitudes in the damper plane and damping coefficient have been considered to assess the system performance. Tests were conducted on two damper configurations that were to go in the rotor assembly of a certain gas turbine engine. Land width and film thickness were varied, and experiments were conducted for different values of excitation frequency, oil supply pressure, and unbalance. The test program showed that the parameters are to be individually optimized to obtain better overall performance in the damper systems without centralizing springs. The damper configurations subjected to severe dynamic conditions due to unbalance on overhung mass were also experimentally analyzed.

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