GT2012- 68212 1 ASME GT2012-68212 Luis San Andrés Mast-Childs Professor, Fellow ASME Texas A&M University Supported by Pratt & Whitney Engines (UTC) 2012 ASME Turbo Expo Conference, June 11-15 ,2012, Copenhagen, DK accepted for journal publication DAMPING AND INERTIA COEFFICIENTS FOR TWO OPEN ENDS SFDs WITH A CENTRAL GROOVE: MEASUREMENTS AND PREDICTIONS
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GT2012-68212 1 ASME GT2012-68212 Luis San Andrés Mast-Childs Professor, Fellow ASME Texas A&M University Supported by Pratt & Whitney Engines (UTC) 2012.
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GT2012-68212
1
ASME GT2012-68212
Luis San Andrés Mast-Childs Professor, Fellow ASME
Texas A&M University
Supported by Pratt & Whitney Engines (UTC)
2012 ASME Turbo Expo Conference, June 11-15 ,2012, Copenhagen, DK
accepted for journal publication
DAMPING AND INERTIA COEFFICIENTSFOR TWO OPEN ENDS
SFDs WITH A CENTRAL GROOVE: MEASUREMENTS AND PREDICTIONS
GT2012-68212
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In aircraft gas turbines and compressors, squeeze film
dampers aid to attenuate rotor vibrations and to provide
mechanical isolation.
SFD operation & design
SFD with dowel pin
X
Y
X
Y
Too little damping may not be enough to reduce vibrations.
Too much damping may lock damper & degrades system rotordynamic
performance
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SFD with a central groove
Conventional knowledge regards a groove is indifferent to the kinematics of journal motion, thus effectively isolating the adjacent film lands.
Test coefficients are ~ isotropic, but predicted are
unequal, CXX > CYY
Test coefficients are ~ 4-6 larger than simplified
formulas
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MYY (test data)
MYY (prediction)
MXX (test data)
MXX (prediction) Predictions match well the
test data.
Static eccentricity ratio (es / cB)
Iner
tia
Co
effi
cien
ts (
Sh
ort
SF
D)
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Short SFD, dη = 2.8cB
0
10
20
30
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Inertia coefficients increase moderately with static
eccentricity.
Predicted MXX > MYY
circular orbits r/c = 0.1
Inertia coefficients Short SFD
Test coefficients are ~ 20-30 larger than simplified
formulas
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CYY (test data)
CYY (prediction)
CXX (test data)
CXX (prediction)
Static eccentricity ratio (es / cA)
Dam
pin
g C
oef
fici
ents
(L
on
g S
FD
) 10Long SFD, dη = 1.6cA
0
2
4
6
8
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Damping coefficients increase more rapidly for the
long damper.
The test and predicted coefficients are not very
sensitive to static eccentricity (es).
Predicted coefficients agree well with test data.
circular orbits r/c = 0.1
Damping coefficients Long SFD
Test coefficients are ~ 3-4 larger than simplified
formulas
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MYY (test data)
MXX (prediction)
MXX (test data)
MYY (prediction)
Inertia coefficients are underpredicted
Static eccentricity ratio (es / cA)
Iner
tia
Co
effi
cien
ts (
Lo
ng
SF
D)
12
Long SFD, dη = 1.6cA
0
4
6
8
10
0.0 0.1 0.2 0.3 0.4 0.5 0.6
2
Coefficients grow moer rapidly with static
eccentricity than in short damper.
Tests and predicted force coefficients are not
sensitive to static eccentricity (es)
circular orbits r/c = 0.1
Inertia coefficients Long SFD
Test coefficients are ~ 8-10 larger than simplified
formulas
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ConclusionsFor both dampers and most test conditions: cross-
coupled damping and inertia force coefficients are small.
Long damper has ~ 7 times more damping than short length damper. Inertia coefficients are two times larger.
SFD force coefficients are more a function of static eccentricity than amplitude of whirl. Coefficients change little with ellipticity of orbit.
•Predictions from modern predictive tool agree well with the test force coefficients.
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Conclusions
More work conducted with both dampers (short and long) with
• SEALED ends (piston rings)
• with larger clearances (2c)
• 0-1-2 orifices plugged (3-2-1 holes active)
will be reported at a later date.
Current damper installation has NO central groove.
• Central grove is NOT a zone of constant pressure: dynamic pressures as large as in film lands.
• Classical theory predicts too low damping & inertias: 1/7 of test values
& update
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Thanks to • Pratt & Whitney Engines
• students Sanjeev Seshaghiri, Paola Mahecha, Shraddha Sangelkar, Adolfo Delgado,
Sung-Hwa Jeung, Sara Froneberger, Logan Havel, James Law.
Acknowledgments
Learn more at http://rotorlab.tamu.edu
Questions (?)
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• Della Pietra and Adilleta, 2002, The Squeeze Film Damper over Four Decades of Investigations. Part I: Characteristics and Operating Features, Shock Vib. Dig, (2002), 34(1), pp. 3-26, Part II: Rotordynamic Analyses with Rigid and Flexible Rotors, Shock Vib. Dig., (2002), 34(2), pp. 97-126.
• Zeidan, F., L. San Andrés, and J. Vance, 1996, "Design and Application of Squeeze Film Dampers in Rotating Machinery," Proceedings of the 25th Turbomachinery Symposium, Turbomachinery Laboratory, Texas A&M University, September, pp. 169-188.
• Zeidan, F., 1995, "Application of Squeeze Film Dampers", Turbomachinery International, Vol. 11, September/October, pp. 50-53.
• Vance, J., 1988, "Rotordynamics of Turbomachinery," John Wiley and Sons, New York
Parameter identification: • Tiwari, R., Lees, A.W., Friswell, M.I. 2004. “Identification of Dynamic Bearing Parameters: A
Review,” The Shock and Vibration Digest, 36, pp. 99-124.
Relevant Past Work
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TAMU references2011 San Andrés, L., and Delgado, A., “A Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals
Operating Eccentrically,” ASME Paper GT2011-45274
2010 Delgado, A., and San Andrés, L., 2010, “A Model for Improved Prediction of Force Coefficients in Grooved Squeeze Film Dampers and Grooved Oil Seal Rings”, ASME Journal of Tribology Vol. 132
Delgado, D., and San Andrés, L., 2010, “Identification of Squeeze Film Damper Force Coefficients from Multiple-Frequency, Non-Circular Journal Motions,” ASME J. Eng. Gas Turbines Power, Vol. 132 (April), p. 042501 (ASME Paper No. GT2009-59175)
2009 Delgado, A., and San Andrés, L., 2009, “Nonlinear Identification of Mechanical Parameters on a Squeeze Film Damper with Integral Mechanical Seal,” ASME Journal of Engineering for Gas Turbines and Power, Vol. 131 (4), pp. 042504 (ASME Paper GT2008-50528)
2003 San Andrés, L., and S. Diaz, 2003, “Flow Visualization and Forces from a Squeeze Film Damper with Natural Air Entrainment,” ASME Journal of Tribology, Vol. 125, 2, pp. 325-333
2001 Diaz, S., and L. San Andrés, 2001, "Air Entrainment Versus Lubricant Vaporization in Squeeze Film Dampers: An Experimental Assessment of their Fundamental Differences,” ASME Journal of Gas Turbines and Power, Vol. 123 (4), pp. 871-877
2000 Tao, L., S. Diaz, L. San Andrés, and K.R. Rajagopal, 2000, "Analysis of Squeeze Film Dampers Operating with Bubbly Lubricants" ASME Journal of Tribology, Vol. 122, 1, pp. 205-210
1997 Arauz, G., and L. San Andrés, 1997 "Experimental Force Response of a Grooved Squeeze Film Damper," Tribology International, Vol. 30, 1, pp. 77-86
1996 San Andrés, L., 1996, "Theoretical and Experimental Comparisons for Damping Coefficients of a Short Length Open-End Squeeze Film Damper," ASME Journal of Engineering for Gas Turbines and Power, Vol. 118, 4, pp. 810-815
SFDs
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Select effective groove depth
Predictions overlaid with test data to estimate effective groove depth