Response of a Squeeze Film Damper-Elastic Structure System to Multiple and Consecutive Impact Loads

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung
Keyword(s):  
Transient Response ◽  
Damping Ratio ◽  
Test System ◽  
Elastic Structure ◽  
Squeeze Film ◽  
Radial Clearance ◽  
System Response ◽  
Fluid Inertia ◽  
Squeeze Film Dampers ◽  
Structural Isolation

Squeeze film dampers (SFDs) are common in aircraft gas turbine engines, customized to provide a desired level of damping while also ensuring structural isolation. This paper presents measurements obtained in a test rig composed of a massive cartridge, an elastic structure, and an open-ends SFD with length L = 25.4 mm, diameter D = 127 mm, and radial clearance c = 0.267 mm. ISO VG 2 oil at room temperature lubricates the thin film. The measurements quantify the system transient response to sudden loads for motions departing from various static eccentricity displacements, es/c = 0–0.6. The batch of tests include recording the system response to (a) one single impact, (b) two (and three) impacts with an elapsed time of 30 ms in between, and (c) two or more consecutive impacts, without any delay, each with a load magnitude at 50% of the preceding impact. The load actions intend to reproduce, for example, a hard landing on an uneven surface or plunging motions from sudden contacts in a machine tool. The test system transient responses due to one or more impacts, each 30 ms apart, show the peak amplitude of motion (ZMAX) is proportional to the magnitude of applied load (FMAX). The identified system damping ratio (ξ) is proportional to the peak dynamic displacement as a linear system would show. Predictions of transient response from a physical SFD model accounting for fluid inertia correlate best with the experimental results as they produce greatly reduced peak dynamic motions when compared to predictions from a purely viscous SFD model. For the responses due to consecutive impacts, one after the other with no delay, the system motion does not decay immediately but builds to produce larger motion amplitudes than in the earlier cases. Eventually, as expected, after several oscillations, the system comes to rest. For an identical damper having a smaller clearance cs = 0.213 mm (0.8c), its damping ratio (ξs) is ∼1.3 to ∼1.7 times greater than the damping ratio for the damper with a larger film clearance (ξ). Hence, the experimentally derived (ξs/ξ) scales with (c/cs)2. The finding demonstrates the importance of manufacturing precisely the components in a damper to produce an accurate clearance.

Response of a Squeeze Film Damper-Elastic Structure System to Multiple and Consecutive Impact Loads

2016 ◽  
Author(s):  
Luis San Andrés ◽  
Sung-Hwa Jeung
Keyword(s):  
Transient Response ◽  
Damping Ratio ◽  
Test System ◽  
Elastic Structure ◽  
Squeeze Film ◽  
Radial Clearance ◽  
System Response ◽  
Fluid Inertia ◽  
Squeeze Film Dampers ◽  
Structural Isolation

Squeeze Film Dampers (SFDs) are common in aircraft gas turbine engines, customized to provide a desired level of damping while also ensuring structural isolation. This paper presents measurements obtained in a test rig composed of a massive cartridge, an elastic structure, and an open ends SFD with length L=25.4 mm, diameter D=127 mm, and radial clearance c=0.267 mm. ISO VG 2 oil at room temperature lubricates the thin film. The measurements quantify the system transient response to sudden loads for motions departing from various static eccentricity displacements, es/c=0 to 0.6. The batch of tests include recording the system response to (a) one single impact, (b) two (and three) impacts with an elapsed time of 30 ms in between, and (c) two or more consecutive impacts, without any delay, each with a load magnitude at 50% of the preceding impact. The load actions intend to reproduce, for example, a hard landing on an uneven surface or plunging motions from sudden contacts in a machine tool. The test system transient responses due to one or more impacts, each 30 ms apart, show the peak amplitude of motion (ZMAX) is proportional to the magnitude of applied load (FMAX). The identified system damping ratio (ξ) is proportional to the peak dynamic displacement as a linear system would show. Predictions of transient response from a physical SFD model accounting for fluid inertia correlate best with the experimental results as they produce greatly reduced peak dynamic motions when compared to predictions from a purely viscous SFD model. For the responses due to consecutive impacts, one after the other with no delay, the system motion does not decay immediately but builds to produce larger motion amplitudes than in the earlier cases. Eventually, as expected, after several oscillations the system comes to rest. For an identical damper having a smaller clearance cs=0.213 mm (0.8c), its damping ratio (ξs) is ∼1.3 to ∼1.7 times greater than the damping ratio for the damper with a larger film clearance (ξ). Hence, the experimentally derived (ξs/ξ) scales with (c/cs)2. The finding demonstrates the importance of manufacturing precisely the components in a damper to produce an accurate clearance.

Identification of Squeeze Film Damper Force Coefficients From Multiple-Frequency, Non-Circular Journal Motions

2009 ◽  
Author(s):  
Adolfo Delgado ◽  
Luis San Andre´s
Keyword(s):  
High Speed ◽  
Test System ◽  
Forced Response ◽  
Supported Housing ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Feed Pressure ◽  
Squeeze Film Dampers ◽  
In Series ◽  
Structural Isolation

In rotor-bearing systems, squeeze film dampers (SFDs) provide structural isolation, reduce amplitudes of rotor response to imbalance, and in some instances, increase the system threshold speed of instability. SFDs are typically installed at the bearing supports, either in series or in parallel. In multi-spool engines, SFDs are located in the interface between rotating shafts. These intershaft dampers must ameliorate complex rotor motions of various whirl frequencies arising from the low speed and the high speed rotors. The paper presents experiments to characterize the forced response of an open ends SFD subject to dynamic loads with multiple frequencies, as in a jet engine intershaft damper. The test rig comprises of a stationary journal and a flexibly supported housing that holds the test damper and instrumentation. The open ends SFD is 127 mm in diameter, 25.4 mm film land length, and radial clearance of 0.125 mm. The damper is lubricated with ISO VG 2 oil at room temperature (24 °C, feed pressure 31 kPa). In the experiments, two orthogonally positioned shakers deliver forces to the test damper that produce controlled amplitude motions with two whirl frequencies, one fixed and the other one varying over a specified range that includes the test system natural frequency. The test data collected, forces and motions versus time, are converted into the frequency domain for parameter identification. The identified viscous damping coefficients are strong functions of the amplitude of journal motion, lying within predictions from classical formulas for circular centered orbits and small amplitude motions about an eccentric journal position. The damper inertia coefficients agree well with predictions derived from a fluid flow model that includes the effect of the feed groove.

Identification of Squeeze Film Damper Force Coefficients From Multiple-Frequency Noncircular Journal Motions

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Adolfo Delgado ◽  
Luis San Andrés
Keyword(s):  
High Speed ◽  
Test System ◽  
Forced Response ◽  
Supported Housing ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Feed Pressure ◽  
Squeeze Film Dampers ◽  
In Series ◽  
Structural Isolation

In rotor-bearing systems, squeeze film dampers (SFDs) provide structural isolation, reduce amplitudes of rotor response to imbalance, and in some instances, increase the system threshold speed of instability. SFDs are typically installed at the bearing supports, either in series or in parallel. In multispool engines, SFDs are located in the interface between rotating shafts. These intershaft dampers must ameliorate complex rotor motions of various whirl frequencies arising from the low speed and the high speed rotors. The paper presents experiments to characterize the forced response of an open ends SFD subject to dynamic loads with multiple frequencies, as in a jet engine intershaft damper. The test rig comprises of a stationary journal and a flexibly supported housing that holds the test damper and instrumentation. The open ends SFD is 127 mm in diameter, 25.4 mm film land length, and has a radial clearance of 0.125 mm. The damper is lubricated with ISO VG 2 oil at room temperature (24°C, feed pressure 31 kPa). In the experiments, two orthogonally positioned shakers deliver forces to the test damper that produce controlled amplitude motions with two whirl frequencies, one fixed and the other one varying over a specified range that includes the test system natural frequency. The test data collected, forces and motions versus time, are converted into the frequency domain for parameter identification. The identified viscous damping coefficients are strong functions of the amplitude of journal motion, lying within predictions from classical formulas for circular centered orbits and small amplitude motions about an eccentric journal position. The damper inertia coefficients agree well with predictions derived from a fluid flow model that includes the effect of the feed groove.

Experimental Pressures and Film Forces in a Squeeze Film Damper

1993 ◽  
Vol 115 (1) ◽  
pp. 134-140 ◽  
Author(s):  
G. L. Arauz ◽  
L. A. San Andres
Keyword(s):  
Tangential Force ◽  
Radial Force ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Fluid Inertia ◽  
Damping Force ◽  
Inertia Effects ◽  
Squeeze Film Dampers ◽  
Tangential Forces ◽  
Lubricant Viscosity

The effect of whirl frequency and lubricant viscosity on the dynamic pressures and force response of an open end and a partially sealed squeeze film dampers (SFD) with a radial clearance of 0.38 mm is determined experimentally. The experiments are carried out in a damper test rig executing circular centered orbits and for whirl frequencies ranging from 33 to 83 Hz. The experimental results show that the sealed SFD configuration produces larger tangential forces than the open end SFD. The tangential (damping) force increases linearly with increasing whirl frequency. For this radial clearance fluid inertia effects in the damper are found to be negligible since the squeeze film Reynolds number is less than 1.20. Cavitation was observed in both damper configurations at high frequencies and high lubricant viscosities. This condition limited the rate of increment of the damping (tangential) force with increasing frequency and reduced the radial force when lubricant viscosity increased.

Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1983 ◽  
Vol 105 (3) ◽  
pp. 606-614 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.

Dynamic Analysis of a Coupled Dual-Rotor With Squeeze Film Damper Considering Sudden Unbalance

2021 ◽  
Author(s):  
Ying Cui ◽  
Yuxi Huang ◽  
Guogang Yang ◽  
Yongliang Wang ◽  
Han Zhang
Keyword(s):  
Steady State ◽  
Transient Response ◽  
Rotor System ◽  
Lubricating Oil ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Oil Viscosity ◽  
Squeeze Film Damper ◽  
Damping Effect ◽  
Bistable State

Abstract A nonlinear multi-degree-of-freedom dynamic model of a coupled dual-rotor system with an intershaft bearing and uncentralized squeeze film damper is established by using finite element method. Based on the model, the critical speed characteristic diagram and vibration modes of the system were calculated. The steady-state unbalance response is obtained by using Newmark-β algorithm. The numerical results show the effect of SFD position in the dual-rotor system on response amplitude. It is found that with the decrease of radial clearance and the increase of length-diameter ratio and lubricating oil viscosity, the damping effect of SFD is enhanced and the bistable state phenomenon can be suppressed. The transient response of the system in case of sudden unbalance occurring at the fan was simulated by applying a step function. It is demonstrated that the SFD can effectively reduce the duration and maximum amplitude of the transient process, but at certain speeds, the SFD will increase the amplitude after the system returns to steady state, the damping effect on the transient response is also enhanced with the increase of length-diameter and the decrease of radial clearance, and with the increase of the sudden unbalance value, the response is more likely to stabilized at the high amplitude state of the bistable state.

scholarly journals Squeeze-Film Damper Technology: Part 1 — Prediction of Finite Length Damper Performance

1983 ◽  
Author(s):  
J. W. Lund ◽  
A. J. Smalley ◽  
J. A. Tecza ◽  
J. F. Walton
Keyword(s):  
Finite Length ◽  
Gas Turbines ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Strongly Coupled ◽  
Squeeze Film Damper ◽  
Rotor Systems ◽  
Squeeze Film Dampers ◽  
Calculation Results

Squeeze-film dampers are commonly used in gas turbine engines and have been applied successfully in a great many new designs, and also as retrofits to older engines. Of the mechanical components in gas turbines, squeeze-film dampers are the least understood. Their behavior is nonlinear and strongly coupled to the dynamics of the rotor systems on which they are installed. The design of these dampers is still largely empirical, although they have been the subject of a large number of past investigations. To describe recent analytical and experimental work in squeeze-film damper technology, two papers are planned. This abstract outlines the first paper, Part 1, which concerns itself with squeeze-film damper analysis. This paper will describe an analysis method and boundary conditions which have been developed recently for modelling dampers, and in particular, will cover the treatment of finite length, feed and drain holes and fluid inertia effects, the latter having been shown recently to be of great importance in predicting rotor system behavior. A computer program that solves the Reynolds equation for the above conditions will be described and sample calculation results presented.

Dynamic Response of Squeeze Film Dampers Operating With Bubbly Mixtures

2002 ◽  
Author(s):  
Luis San Andre´s ◽  
Oscar C. De Santiago
Keyword(s):  
Load Transfer ◽  
Transfer Functions ◽  
Dynamic Performance ◽  
Air Entrainment ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Performance Impact ◽  
Air Content ◽  
Squeeze Film Dampers ◽  
Oil Mixtures

Squeeze film dampers (SFDs) aid to attenuate vibrations in compressors and turbines while traversing critical speeds. In actual applications, gas ingestion from the environment may lead to the formation of a foamy lubricant that degrades the rotor/bearing system dynamic performance. Impact and imbalance response tests conducted on a rigid rotor supported on SFDs, and aimed to emulate the pervasive effect of air ingestion into the damper film lands, are reported. Two types of squeeze film damper support the test rotor, one is a conventional cylindrical design with a squirrel cage type elastic support, and the other is a compact four-pad damper with integral wire EDM elastic supports. Both dampers have identical diameter and radial clearance. Controlled (air in oil) mixtures ranging from pure oil to all air conditions are supplied to the SFDs, and measurements of the transient rotor response to calibrated impact loads are conducted. System damping coefficients, identified from acceleration/load transfer functions, decrease steadily as the air content in the mixture increases. However, measurements of the rotor synchronous imbalance response conducted with a lubricant bubbly mixture (50% air volume) show little difference with test results obtained with pure lubricant supplied to the dampers. The experimental results show that air entrainment is process and device dependent, and that small amounts of lubricant enable the effective action of SFDs when the rotor traverses a critical speed.

Application of computational fluid dynamics for thermohydrodynamic analysis of high-speed squeeze-film dampers

2019 ◽  
Vol 43 (3) ◽  
pp. 306-321 ◽  
Author(s):  
Maxime Perreault ◽  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Base Line ◽  
Squeeze Film Dampers ◽  
Shaft Deflection ◽  
Whirl Speed

In high-speed turbomachinery, the presence of rotor vibrations, which produce undesirable noise or shaft deflection and losses in performance, has brought up the need for the application of a proper mechanism to attenuate the vibration amplitudes. Squeeze-film dampers (SFDs) are a widely employed solution to the steady-state vibrations in high-speed turbomachinery. SFDs contain a thin film of lubricant that is susceptible to changes in temperature. For this reason, the analysis of thermohydrodynamic (THD) effects on the SFD damping properties is essential. This paper develops a computational fluid dynamics (CFD) model to analyze the THD effects in SFDs, and enabling the application of CFD analysis to be a base-line for validating the accuracy of analytical THD SFD models. Specifically, the CFD results are compared against numerical simulations at different operating conditions, including eccentricity ratios and journal whirl speeds. The comparisons demonstrate the effective application of CFD for THD analysis of SFDs. Additionally, the effect of the lubricant THDs on the viscosity, maximum and mass-averaged temperature, as well as heat generation rates inside the SFD lubricant are analyzed. The temperature of the lubricant is seen to rise with increasing whirl speed, eccentricity ratios, damper radial clearance, and shaft radii.

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