Estimation of the Linearized Damping Coefficients of a Squeeze-Film Vibration Isolator

1987 ◽  
Vol 201 (3) ◽  
pp. 181-191 ◽  
Author(s):  
R Stanway ◽  
R Firoozian ◽  
J E Mottershead
Keyword(s):  
Single Frequency ◽  
Squeeze Film ◽  
Experimental Facility ◽  
Vibration Isolator ◽  
New Approach ◽  
Filtering Algorithm ◽  
Damping Coefficients ◽  
Performance Predictions ◽  
Frequency Excitation ◽  
Extract Information

In this paper the authors present experimental confirmation of the feasibility of a new approach to the estimation of the four damping coefficients associated with a squeeze-film vibration isolator. The design and construction of the experimental facility is described in detail. A time-domain filtering algorithm is applied to process the displacement responses to single-frequency excitation and thus extract information on the linearized dynamics of the squeeze-film. The estimated coefficients are validated by comparing performance predictions with those obtained from spectrum analysis and from short-bearing theory. The significance of the results is discussed and suggestions are made for further work in this area.

Identification of Force Coefficients in a Squeeze Film Damper With a Mechanical End Seal: Centered Circular Orbit Tests

2006 ◽  
Author(s):  
Luis San Andre´s ◽  
Adolfo Delgado
Keyword(s):  
Dry Friction ◽  
Companion Paper ◽  
Single Frequency ◽  
Squeeze Film ◽  
Mechanical Seal ◽  
Damping Force ◽  
Force Coefficients ◽  
Damping Coefficients ◽  
The Individual ◽  
Aircraft Application

The damping capability of squeeze film dampers (SFDs) relies on adequate end sealing to prevent air ingestion and entrapment. The paper presents the parameter identification, procedure and damping coefficients, of a test SFD featuring a mechanical seal that effectively eliminates lubricant side leakage. The test damper reproduces an aircraft application intended to contain the lubricant in the film lands for extended periods of time. The test damper journal is 2.54 cm in length and 12.7 cm in diameter, with a nominal clearance of 0.127 mm. The SFD feed end is flooded with oil, while the discharge end contains a recirculation groove and four orifice ports. In a companion paper (ASME GT2006-90782), single frequency - unidirectional load excitation tests were conducted, without and with lubricant in the squeeze film lands, to determine the seal dry-friction force and viscous damping force coefficients. Presently, tests with single frequency excitation loads rendering circular centered orbits excitations are conducted to identify the SFD force coefficients. The identified parameters include the overall system damping and the individual contributions from the squeeze film, dry friction and structural damping. The identified system damping coefficients are frequency and motion amplitude dependent due to the dry friction interaction at the mechanical seal interface. Identified squeeze film force coefficients, damping and added mass, are in good agreement with predictions based on the full film, short length damper model.

The Damping Characteristics of Vibration Isolators Used in Gas Turbines

1977 ◽  
Vol 19 (6) ◽  
pp. 271-277 ◽  
Author(s):  
R. Holmes
Keyword(s):  
Gas Turbines ◽  
Journal Bearing ◽  
Nonlinear Damping ◽  
Common Type ◽  
Squeeze Film ◽  
Vibration Isolator ◽  
Vibration Isolators ◽  
Damping Coefficients ◽  
Damping Characteristics ◽  
Linear Damping

The linear and nonlinear damping performance of a common type of gas-turbine vibration isolator, consisting of a squeeze-film journal bearing in parallel with a linear retainer spring, is computed and used to prescribe limits to the use of linear damping coefficients.

Damping and Inertia Coefficients for Two End Sealed Squeeze Film Dampers With a Central Groove: Measurements and Predictions

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Luis San Andrés ◽  
Sanjeev Seshagiri
Keyword(s):  
Gas Turbines ◽  
Short Length ◽  
System Stability ◽  
Single Frequency ◽  
Squeeze Film ◽  
Test Results ◽  
Piston Rings ◽  
Damping Coefficients ◽  
Squeeze Film Dampers ◽  
San Andres

Aircraft engine rotors, invariably supported on rolling element bearings with little damping, are particularly sensitive to rotor imbalance and sudden maneuver loads. Most engines incorporate squeeze film dampers (SFDs) as a means to dissipate mechanical energy from rotor motions and to ensure system stability. The paper experimentally quantifies the dynamic forced performance of two end sealed SFDs with dimensions and an operating envelope akin to those in actual jet engine applications. The current experimental results complement and extend prior research conducted with open ends SFDs (San Andrés, 2012, “Damping and Inertia Coefficients for Two Open Ends Squeeze Film Dampers With a Central Groove: Measurements and Predictions,” ASME J. Eng. Gas Turbines Power, 134, p. 102506). In the tests, two journals make for two SFD configurations, both with a diameter D = 127 mm and nominal radial film clearance c = 0.127 mm. One short length damper has film lands with extent L = 12.7 mm, while the other has 25.4 mm ( = 2L) land lengths. A central groove of length LG = L and depth at ¾ L separates the film lands. A light viscosity lubricant is supplied into the central groove via three orifices, 120 deg apart, and then flows through the film lands whose ends are sealed with tight piston rings. The oil pushes through the piston rings to discharge at ambient pressure. In the tests, a static load device pulls the damper structure to increasing eccentricities (maximum 0.38c) and external shakers exert single-frequency loads 50–250 Hz, inducing circular orbits with amplitudes equaling ∼5% of the film clearance. The lubricant feed and groove pressures and flow rates through the top and bottom film lands are recorded to determine the flow resistances through the film lands and the end seals. Measured dynamic pressures in the central groove are as large as those in the film lands, thus demonstrating a strong flow interaction, further intensified by the piston ring end seals which are effective in preventing side leakage. Dynamic pressures and reaction loads are substantially higher than those recorded with the open ends dampers. Comparisons to test results for two identical damper configurations but open ended (San Andrés, 2012, “Damping and Inertia Coefficients for Two Open Ends Squeeze Film Dampers With a Central Groove: Measurements and Predictions,” ASME J. Eng. Gas Turbines Power, 134, p. 102506) demonstrate at least a threefold increase in direct damping coefficients and no less than a double increment in added mass coefficients. Predictions from a physics-based model that includes the central groove, the lubricant feed holes, and the end seals' flow conductances are in agreement with the test results for the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the measurements, while the added masses are under-predicted by ∼25%.

Transient Response of a Short-Length (L/D = 0.2) Open-Ends Elastically Supported Squeeze Film Damper: Centered and Largely Off-Centered Whirl Motions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Luis San Andrés ◽  
Sean Den ◽  
Sung-Hwa Jeung
Keyword(s):  
Dynamic Load ◽  
Short Length ◽  
Single Frequency ◽  
Squeeze Film ◽  
Test Rig ◽  
Sweep Frequency ◽  
Transient Events ◽  
Frequency Excitation ◽  
Static Eccentricity ◽  
Sine Sweep

Commonly employed in air breathing (gas turbine) engines, squeeze film dampers (SFDs) reduce the amplitude of rotor vibration while traversing system critical speeds or in transient events such as during a maneuver load, a hard landing, a blade loss, or an engine startup/shutdown sequence that could instantaneously shift a damper journal eccentricity (es) to near its clearance (c). Experiments investigate the dynamic force performance of an open ends, short-length (L/D = 0.2) SFD test rig with radial clearance c = 267 μm and undergoing centered (es/c = 0) to largely off-centered (es/c → 1) whirl orbit motions induced by both a large static load plus a dynamic load. Four rods, symmetrically arranged to resemble a squirrel cage, elastically support the SFD test rig. A hydraulic load system displaces the test damper structure into static eccentricity (es/c). One of two types of dynamic load with amplitude FX = FY excite the SFD: a single-frequency, stepping from low frequency to high frequency discretely; or a sine-sweep frequency growing linearly with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c = 0.0, 0.95, and 0.99, the dynamic load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evolving rapidly at ∼33 Hz/s. Measurements of SFD displacements characterize the behavior of the SFD rig during its transient response which crosses two system natural frequencies. For motions departing from a largely off-centered condition (es → c), the dynamic load forces the damper to whirl with highly elliptical orbits, in particular while crossing a resonance (damped natural frequency). Moreover, the dynamic motions departing from es ∼ c are smaller in amplitude than those arising from a centered condition (es/c = 0). The larger damping produced by a very small squeeze film thickness explains the difference in response amplitude. At a largely off-centered condition (es/c = 0.99) and a low excitation frequency (f < 40 Hz), intermittent contact between the damper journal and its housing occurs as evidenced by a large magnitude recorded dynamic pressure (on the order of MPa). For whirl motions around various static eccentricity positions, es/c = 0.0–0.75, the dynamic load covers a frequency range from 10 Hz to 100 Hz using either a single-frequency excitation or a sine-sweep frequency excitation with a slow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimental procedure builds complex stiffness in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around small to large static eccentricities, es/c = 0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic loads coincide with those extracted from single-frequency dynamic load tests over the same frequency range. Short-length SFD theory predictions for damping coefficients agree with the experimental results. Predicted added mass or inertia coefficients, like the model, fall short of the target experimental magnitudes. The test results give practitioners the credence to certify the ability of a SFD to control rotor response amplitude during typical transient events.

scholarly journals Nonlinear Identification of a Squeeze-Film Damper

1988 ◽  
Vol 110 (3) ◽  
pp. 486-491 ◽  
Author(s):  
R. Stanway ◽  
J. E. Mottershead ◽  
R. Firoozian
Keyword(s):  
Nonlinear Filtering ◽  
Velocity Model ◽  
Squeeze Film ◽  
Experimental Facility ◽  
Vibration Damper ◽  
Nonlinear Identification ◽  
Squeeze Film Damper ◽  
Filtering Algorithm ◽  
Representative Selection ◽  
Selection Of

In this paper the authors describe an experimental study to identify the damping laws associated with a squeeze-film vibration damper. This is achieved by using a nonlinear filtering algorithm to process displacement responses of the damper ring to synchronous excitation and thus to estimate the parameters in an nth-power velocity model. The experimental facility is described in detail and a representative selection of results is included. The identified models are validated through the prediction of damper-ring orbits and comparison with observed responses.

Transient Response of a Short-Length (L/D=0.2) Open-Ends Elastically Supported Squeeze Film Damper: Centered and Largely Off-Centered Whirl Motions

2016 ◽  
Author(s):  
Luis San Andrés ◽  
Sean Den ◽  
Sung-Hwa Jeung
Keyword(s):  
Dynamic Load ◽  
Short Length ◽  
Single Frequency ◽  
Squeeze Film ◽  
Test Rig ◽  
Sweep Frequency ◽  
Transient Events ◽  
Frequency Excitation ◽  
Static Eccentricity ◽  
Sine Sweep

Commonly employed in air breathing (gas turbine) engines, squeeze film dampers (SFDs) reduce the amplitude of rotor vibration while traversing system critical speeds or in transient events such as during a maneuver load, a hard landing, a blade loss, or an engine startup/shutdown sequence that could instantaneously shift a damper journal eccentricity (es) to near its clearance (c). Experiments investigate the dynamic force performance of an open ends, short-length (L/D=0.2) SFD test rig with radial clearance c=267 μm and undergoing centered (es/c=0) to largely off-centered (es/c → 1) whirl orbit motions induced by both a large static load plus a dynamic load. Four rods, symmetrically arranged to resemble a squirrel cage, elastically support the SFD test rig. A hydraulic load system displaces the test damper structure into static eccentricity (es/c). One of two types of dynamic load with amplitude FX=FY excite the SFD: a single-frequency, stepping from low frequency to high frequency discretely; or a sine-sweep frequency growing linearly with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c=0.0, 0.95, and 0.99 the dynamic load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evolving rapidly at ∼33 Hz/s. Measurements of SFD displacements characterize the behavior of the SFD rig during its transient response which crosses two system natural frequencies. For motions departing from a largely off-centered condition (es → c), the dynamic load forces the damper to whirl with highly elliptical orbits, in particular while crossing a resonance (damped natural frequency). Moreover, the dynamic motions departing from es∼c are smaller in amplitude than those arising from a centered condition (es/c=0). The larger damping produced by a very small squeeze film thickness explains the difference in response amplitude. At a largely off-centered condition (es/c=0.99) and a low excitation frequency (f < 40 Hz), intermittent contact between the damper journal and its housing occurs as evidenced by a large magnitude recorded dynamic pressure (on the order of MPa). For whirl motions around various static eccentricity positions, es/c=0.0–0.75, the dynamic load covers a frequency range from 10 Hz to 100 Hz using either a single-frequency excitation or a sine-sweep frequency excitation with a slow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimental procedure builds complex stiffnesses in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around small to large static eccentricities, es/c=0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic loads coincide with those extracted from single-frequency dynamic load tests over the same frequency range. Short-length SFD theory predictions for damping coefficients agree with the experimental results. Predicted added mass or inertia coefficients, like the model, fall short of the target experimental magnitudes. The test results give practitioners the credence to certify the ability of a SFD to control rotor response amplitude during typical transient events.

Damping and Inertia Coefficients for Two End Sealed Squeeze Film Dampers With a Central Groove: Measurements and Predictions

2013 ◽  
Author(s):  
Luis San Andrés ◽  
Sanjeev Seshagiri
Keyword(s):  
Ambient Pressure ◽  
Mechanical Energy ◽  
Short Length ◽  
System Stability ◽  
Single Frequency ◽  
Squeeze Film ◽  
Test Results ◽  
Piston Rings ◽  
Damping Coefficients ◽  
Squeeze Film Dampers

Aircraft engine rotors, invariably supported on rolling element bearings with little damping, are particularly sensitive to rotor imbalance and sudden maneuver loads. Most engines incorporate Squeeze Film Dampers (SFDs) as means to dissipate mechanical energy from rotor motions and to ensure system stability. The paper quantifies experimentally the dynamic forced performance of two end sealed SFDs with dimensions and operating envelope akin to those in actual jet engine applications. The current experimental results complement and extend prior research conducted with open ends SFDs [21]. In the tests, two journals make for two SFD configurations, both with diameter D = 127 mm and nominal radial film clearance c = 0.127 mm. One short length damper has film lands with extent L = 12.7 mm, while the other has 25.4 mm (= 2L) land lengths. A central groove with length LG = L and depth at ¾ L separates the film lands. A light viscosity lubricant is supplied into the central groove via 3 orifices, 120° apart, and then flows through the film lands whose ends are sealed with tight piston rings. The oil pushes through the piston rings to discharge at ambient pressure. In the tests, a static load device pulls the damper structure to increasing eccentricities (max. 0.38c) and external shakers exert single-frequency loads, 50 Hz–250 Hz, inducing circular orbits with amplitudes equaling ∼5% of the film clearance. The lubricant feed and groove pressures and flow rates through the top and bottom film lands are recorded to determine the flow resistances through the film lands and the end seals. Measured dynamic pressures in the central groove are as large as those in the film lands thus demonstrating a strong flow interaction, further intensified by the piston ring end seals which are effective in preventing side leakage. Dynamic pressures and reaction loads are substantially higher than those recorded with the open ends dampers. Comparisons to test results for two identical damper configurations but open ended [21] demonstrate at least a thrice increase in direct damping coefficients and no less than a twice increment in added mass coefficients. Predictions from a physics based model that includes the central groove, the lubricant feed holes and the end seals’ flow conductances are in agreement with the test results for the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the measurements while the added masses are under predicted by ∼25%.

Ball bearing turbocharger vibration management: application on high speed balancer

2020 ◽  
Vol 21 (6) ◽  
pp. 619
Author(s):  
Kostandin Gjika ◽  
Antoine Costeux ◽  
Gerry LaRue ◽  
John Wilson
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Ball Bearing ◽  
Squeeze Film ◽  
Design And Technology ◽  
Squeeze Film Damper ◽  
Damping Coefficients ◽  
Bearing Loads ◽  
Stiffness And Damping

Today's modern internal combustion engines are increasingly focused on downsizing, high fuel efficiency and low emissions, which requires appropriate design and technology of turbocharger bearing systems. Automotive turbochargers operate faster and with strong engine excitation; vibration management is becoming a challenge and manufacturers are increasingly focusing on the design of low vibration and high-performance balancing technology. This paper discusses the synchronous vibration management of the ball bearing cartridge turbocharger on high-speed balancer and it is a continuation of papers [1–3]. In a first step, the synchronous rotordynamics behavior is identified. A prediction code is developed to calculate the static and dynamic performance of “ball bearing cartridge-squeeze film damper”. The dynamic behavior of balls is modeled by a spring with stiffness calculated from Tedric Harris formulas and the damping is considered null. The squeeze film damper model is derived from the Osborne Reynolds equation for incompressible and synchronous fluid loading; the stiffness and damping coefficients are calculated assuming that the bearing is infinitely short, and the oil film pressure is modeled as a cavitated π film model. The stiffness and damping coefficients are integrated on a rotordynamics code and the bearing loads are calculated by converging with the bearing eccentricity ratio. In a second step, a finite element structural dynamics model is built for the system “turbocharger housing-high speed balancer fixture” and validated by experimental frequency response functions. In the last step, the rotating dynamic bearing loads on the squeeze film damper are coupled with transfer functions and the vibration on the housings is predicted. The vibration response under single and multi-plane unbalances correlates very well with test data from turbocharger unbalance masters. The prediction model allows a thorough understanding of ball bearing turbocharger vibration on a high speed balancer, thus optimizing the dynamic behavior of the “turbocharger-high speed balancer” structural system for better rotordynamics performance identification and selection of the appropriate balancing process at the development stage of the turbocharger.

Two-Frequency Oscillation With Combined Coulomb and Viscous Frictions

2002 ◽  
Vol 124 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Gong Cheng ◽  
Jean W. Zu
Keyword(s):  
Steady State ◽  
Dry Friction ◽  
Single Frequency ◽  
Friction Oscillator ◽  
One Stop ◽  
Frequency Excitation ◽  
Stop Motion ◽  
The One ◽  
Coulomb Dry Friction ◽  
Mass Spring

In this paper, a mass-spring-friction oscillator subjected to two harmonic disturbing forces with different frequencies is studied for the first time. The friction in the system has combined Coulomb dry friction and viscous damping. Two kinds of steady-state vibrations of the system—non-stop and one-stop motions—are considered. The existence conditions for each steady-state motion are provided. Using analytical analysis, the steady-state responses are derived for the two-frequency oscillating system undergoing both the non-stop and one-stop motions. The focus of the paper is to study the influence of the Coulomb dry friction in combination with the two frequency excitations on the dynamic behavior of the system. From the numerical simulations, it is found that near the resonance, the dynamic response due to the two-frequency excitation demonstrates characteristics significantly different from those due to a single frequency excitation. Furthermore, the one-stop motion demonstrates peculiar characteristics, different from those in the non-stop motion.

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