scholarly journals Closure to “Discussion of ‘Effect of a Circumferential Feeding Groove on the Dynamic Force Response of a Short Squeeze Film Damper’” (1994, ASME J. Tribol., 116, p. 376)

1994 ◽  
Vol 116 (2) ◽  
pp. 376-377
Author(s):  
G. L. Arauz ◽  
L. San Andres
Keyword(s):  
Squeeze Film ◽  
Dynamic Force ◽  
Force Response ◽  
Squeeze Film Damper

Effect of a Circumferential Feeding Groove on the Dynamic Force Response of a Short Squeeze Film Damper

1994 ◽  
Vol 116 (2) ◽  
pp. 369-376 ◽  
Author(s):  
G. L. Arauz ◽  
L. San Andres
Keyword(s):  
Flow Model ◽  
Dynamic Pressure ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Force Response ◽  
Squeeze Film Damper ◽  
Circumferential Groove ◽  
Damping Characteristics ◽  
Radial Forces ◽  
Lubricant Viscosity

The effect of a circumferential feeding groove on the dynamic force response of a short length, open end squeeze film damper is studied experimentally. Damper configurations with increasing groove depths and journal orbit radii were tested for several conditions of whirl frequency and lubricant viscosity. Significant levels of dynamic pressure were measured at the circumferential groove, and relatively large tangential (damping) forces are produced at the groove which contribute considerably to the damping characteristics of the SFD test articles. Radial forces of substantial magnitude are determined at the groove and at the thin film land where the squeeze film Reynolds number is typically less than 1. The circumferential groove is thought to induce an inertia like effect into the film land. The experimental results correlate well with the predictions from a groove volume-circumferential flow model developed.

Experimental Study on the Effect of a Circumferential Feeding Groove on the Dynamic Force Response of a Sealed Squeeze Film Damper

1996 ◽  
Vol 118 (4) ◽  
pp. 900-905 ◽  
Author(s):  
G. L. Arauz ◽  
Luis San Andres
Keyword(s):  
Piston Ring ◽  
Dynamic Pressure ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Force Response ◽  
Flow Conditions ◽  
Squeeze Film Damper ◽  
Circumferential Groove ◽  
Damping Characteristics ◽  
Radial Forces

The influence of a circumferential feeding groove on the dynamic force response of a sealed squeeze film damper is determined experimentally. The damper is sealed by means of a serrated piston ring located at the discharge end of the damper. Damper configurations with two different groove depths and journal orbit radii were tested at increasing whirl frequencies. Large levels of dynamic pressure were measured at the circumferential groove, and relatively large tangential (damping) forces are produced at the groove which contribute considerably to the damping characteristics of the test damper. Radial forces were also determined at the feeding groove and at the film land for uncavitated flow conditions.

scholarly journals Dynamic Force Response of an Open Ended Squeeze Film Damper

1991 ◽  
Author(s):  
L. A. San Andres ◽  
G. Meng ◽  
S. Yoon
Keyword(s):  
Pressure Field ◽  
Tangential Force ◽  
Radial Force ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Flow Conditions ◽  
Squeeze Film Damper ◽  
Inertial Flow ◽  
Experimental Pressure ◽  
Lubricant Viscosity

The effects of whirl frequency and lubricant viscosity on the experimental pressure field and film forces in an open ended squeeze film damper test rig are presented. The measurements refer to circular centered journal motion of amplitude equal to one half the damper clearance (ε=0.5). The whirl frequency varied between 16Hz to 85Hz, while the lubricant temperature increased from 25°C to 45°C. The damper operated with levels of external pressurization which supressed lubricant cavitation. The experimental results show conclusivey that the radial film force is purely an inertial effect, i.e. it depends solely on the fluid density and the second power of the whirl frequency. The tangential film force shows a variation which depends on the viscous and inertial flow conditions in the squeeze film region. Correlation of experimental forces with conventional SFD models shows the radial force to be π times larger than the theoretical prediction, while the tangential force correlates well for low whirl frequencies and large lubricant viscosities.

Experimental Measurement of the Dynamic Force Response of a Squeeze-Film Bearing Damper

1975 ◽  
Vol 97 (4) ◽  
pp. 1282-1290 ◽  
Author(s):  
John M. Vance ◽  
Alan J. Kirton
Keyword(s):  
Pressure Distribution ◽  
Taylor Vortex ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Force Response ◽  
Cyclic Flow ◽  
Pressure Distributions ◽  
Taylor Vortex Flow ◽  
Force Components ◽  
Annular Clearance

An experimental study of the hydrodynamic force response of a squeeze-film bearing damper with end seals was carried out. Measurements of the pressure distribution about a journal constrained to move in a circular orbit were made for the journal orbit centered in the annular clearance and offset from the center of the annular clearance. The effects of cyclic flow in a radial inlet were studied for the case of the journal orbit centered in the annular clearance. For the off-center case the pressure distribution around the damper was measured for four different combinations of eccentricity, radial velocity, and angular velocity of the line of centers, chosen in such a way as to allow calculation of the four bearing coefficients defined by Tondl. The experimentally determined pressure distributions were numerically integrated to determine the force components of the squeeze film. The results are compared to the “long bearing” and the “short bearing” solutions of Reynolds’ equation. For the centered case, good agreement was found with the shape of the “long bearing” solution. Higher-than-predicted pressures and forces for light viscosity oil are explained by showing that this case is operating in the Taylor vortex flow regime. Similar calculations indicate that turbine dampers can also operate with vortex or turbulent flow.

Experimental force response of a grooved squeeze film damper

1997 ◽  
Vol 30 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Grigory L. Arauz ◽  
Luis San Andres
Keyword(s):  
Squeeze Film ◽  
Force Response ◽  
Squeeze Film Damper

Analysis of Short Squeeze Film Dampers With a Central Groove

1992 ◽  
Vol 114 (4) ◽  
pp. 659-664 ◽  
Author(s):  
Luis A. San Andres
Keyword(s):  
Squeeze Film ◽  
Inertia Force ◽  
Dynamic Force ◽  
Fluid Inertia ◽  
Dynamic Flow ◽  
Low Frequencies ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Squeeze Film Dampers ◽  
Combined Action

A novel analysis for the dynamic force response of a squeeze film damper with a central feeding groove considers the dynamic flow interaction between the squeeze film lands and the feeding groove. For small amplitude centered motions and based on the short bearing model, corrected values for the damping and inertia force coefficients are determined. Correlations with existing experimental evidence is excellent. Analytical results show that the grooved-damper behaves at low frequencies as a single land damper. Dynamic force coefficients are determined to be frequency dependent. Analytical predictions show that the combined action of fluid inertia and groove volume—liquid compressibility affects the force coefficients for dynamic excitation at large frequencies.

On the Effect of the Gap of End Seals on Force Coefficients of a Test Integral Squeeze Film Damper: Experiments and Predictions

2020 ◽  
Author(s):  
Luis San Andrés ◽  
Xueliang Lu ◽  
Bonjin Koo ◽  
Scott Tran
Keyword(s):  
Theory And Practice ◽  
Squeeze Film ◽  
Test Element ◽  
Inlet Temperature ◽  
Dynamic Force ◽  
Virtual Mass ◽  
Squeeze Film Damper ◽  
Force Coefficients ◽  
Rotor Bearing ◽  
Bearing System

Abstract An integral squeeze film damper (ISFD) offers the advantages of a lower number of parts, a shorter axial span, a lighter weight, a split manufacturing and high precision on its film clearance construction. An ISFD does not only add damping to reduce shaft vibration amplitudes and to enhance the stability of a rotor-bearing system but also can be used to tune a rotor-bearing system natural frequency, and thus increasing the operational safety margin between the running shaft speed and the system critical speed. In spite of the numerous commercial applications, the archival literature is scant as per the experimental quantification of force coefficients for ISFDs. This paper details the results of an experimental and analytical endeavor to quantify and to predict the dynamic force coefficients of an ISFD, hence bridging the gap between theory and practice. With an axial length of 76 mm, the test damper element has four arcuate film lands, 73° in arc extent at a diameter of 157 mm, and each with a clearance (c) equaling to 0.353 mm. As is customary, the damper has its axial ends sealed with end plates produced by a set of installed shims giving an axial gap (d) equal to 1.5c, 1.21c, and 0.8c. A baseline configuration, namely open ends, is also tested without the end seals in place. In the test rig, the ISFD and its housing are flexibly mounted while the rotor is rigid and stationary (no spinning). The lubricant is an ISO VG46 oil supplied at a low pressure, 1 to 2 bar(g) and ∼ 47 °C inlet temperature, typical of compressor applications. The test procedure applies static loads on the ISFD and records the bearing static offset or eccentricity to verify the structure stiffness, and meanwhile, individual hydraulic shakers deliver dynamic loads along two orthogonal directions to produce motions over a set frequency range, 10 Hz to 160 Hz. The ISFD produces direct damping and inertia that increase with the journal static eccentricity albeit at a lower rate than predictions from a computational squeeze film flow model that includes lubricant compressibility. The end seals are effective in significantly raising the damping coefficient while reducing the oil through flow rate. The damper with the tightest sealed ends (d = 0.8c) shows nearly 20 times more damping that the open ends ISFD albeit also revealing a significant stiffness hardening (negative virtual mass) as the excitation frequency increases. On the contrary, the open ends ISFD and the sealed ends configurations with gaps d = 1.21c and 1.5c produce a (positive) virtual mass that exceeds the test element physical mass and thus softens the test element direct dynamic stiffness. For the configurations with loose end seals (d = 1.21c or larger to open ends), the model predicts well the damping coefficients but under predicts the added masses by 50% or more. Note this virtual mass coefficient, largely ignored in practice, can make the test element either extremely stiff as with the sealed damper configuration with the smallest gap d = 0.8c, or very soft as with the ISFD with end seals gap = 1.21c or 1.5c. Hence, designers are cautioned not to pursue overly tight end sealed dampers as the mineral lubricant, nearly incompressible though always having a small amount of entrapped gas, may behave distinctly when confined to a squeezed film volume and having no adequate routes to escape or flow through.

Theoretical and Experimental Comparisons for Damping Coefficients of a Short-Length Open-End Squeeze Film Damper

1996 ◽  
Vol 118 (4) ◽  
pp. 810-815 ◽  
Author(s):  
L. A. San Andres
Keyword(s):  
High Speed ◽  
Mechanical Energy ◽  
Short Length ◽  
Fluid Film ◽  
Squeeze Film ◽  
Absolute Pressure ◽  
Dynamic Force ◽  
Fluid Inertia ◽  
Squeeze Film Damper ◽  
Damping Coefficients

Squeeze film dampers (SFD) provide load isolation and attenuate rotor vibrations in high speed turbomachinery. Operating parameters such as whirl frequency, amplitude of journal motion, and value of external pressure supply determine the SFD dynamic force response and its dissipation of mechanical energy. Measurements of pressure fields and fluid film forces in a fully submerged open-end squeeze film damper are presented for tests with rotor speeds to 5000 cpm and low supply pressures. The damper has a clearance of 381 µm (0.015 in.) and the journal describes circular centered orbits of amplitudes ranging from 30 to 50 percent of the bearing clearance. Experimental film pressures depict a vapor cavitation (close to zero absolute pressure) zone increasing in extent as the whirl frequency increases. Estimated fluid film forces from the measured pressure profiles are found to be proportional to whirl speed and lubricant viscosity. Test cross-coupled damping coefficients (Crt) are smaller than predicted values based on the short-length bearing model with a π film cavitation assumption. The direct damping coefficients (Ctt) are larger than theoretical values, especially at low frequencies where the dynamic cavitation region has not grown to half the circumferential flow extent. The experiments demonstrate the viscous character of the fluid film forces in a SFD test apparatus where fluid inertia effects are minimal (squeeze film Reynolds number less than one). On the other hand, the extent of the cavitation zone appears to be dominant on the generation of fluid film forces.

Dynamic Force Response of an Open-Ended Squeeze Film Damper

1993 ◽  
Vol 115 (2) ◽  
pp. 341-346 ◽  
Author(s):  
L. A. San Andres ◽  
G. Meng ◽  
S. Yoon
Keyword(s):  
Pressure Field ◽  
Tangential Force ◽  
Radial Force ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Flow Conditions ◽  
Squeeze Film Damper ◽  
Inertial Flow ◽  
Experimental Pressure ◽  
Lubricant Viscosity

The effects of whirl frequency and lubricant viscosity on the experimental pressure field and film forces in an open-ended squeeze film damper test rig are presented. The measurements refer to circular centered journal motion of amplitude equal to one half the damper clearance (ε = 0.5). The whirl frequency varied between 16 Hz and 85 Hz, while the lubricant temperature increased from 25°C to 45°C. The damper operated with levels of external pressurization that supressed lubricant cavitation. The experimental results show conclusively that the radial film force is purely an inertial effect, i.e., it depends solely on the fluid density and the second power of the whirl frequency. The tangential film force shows a variation that depends on the viscous and inertial flow conditions in the squeeze film region. Correlation of experimental forces with conventional SFD models shows the radial force to be π times larger than the theoretical prediction, while the tangential force correlates well for low whirl frequencies and large lubricant viscosities.

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