The paper presents the experimental unbalance response of two slightly different rigid rotors supported by aerodynamic foil bearings. Impulse (Pelton) turbines manufactured directly in the mass of the rotors (on the outer surface) entrain both rotors at rotation speeds comprised between 50 krpm and 100 krpm. The displacements in the two foil bearings are measured during coast down and are depicted as waterfall plots. They show typical nonlinear behavior, i.e., subsynchronous vibrations accompanying the synchronous component. The measurements clearly show that the subsynchronous components bifurcate or jump at typical rotation speeds (mostly rational fractions of the rotation speed). The nonlinear behavior of the rigid rotor supported on foil bearings is also emphasized by varying the added unbalance: with increasing unbalance the vibration spectrum becomes gradually more diverse as new subsynchronous vibrations appear. The experimental results are compared with very simplified theoretical predictions based on the assumption that the air film in the two bearings is infinitely stiff compared to the foil structure. The latter is characterized by a cubic stiffness and a structural damping coefficient. The comparisons show only a rough qualitative agreement.

References

References
1.
Blok
,
H.
, and
van Rossum
,
J.
,
1953
, “
The Foil Bearing—A New Departure in Hydrodynamic Lubrication
,”
Lubr. Eng.
,
9
(
16
), pp.
316
320
.
2.
Agrawal
,
G. L.
,
1997
, “
Foil Air/Gas Bearing Technology—An Overview
,”
ASME
Paper No. 97-GT-347.
3.
Treece
,
B.
,
Vessa
,
P.
, and
McKeirnan
,
R.
,
2002
, “
Microturbine Recuperator Manufacturing and Operating Experience
,”
ASME
Paper No. GT2002-30404.
4.
Chen
,
H. M.
,
Howarth
,
R.
,
Geren
,
B.
,
Theilacker
,
J. C.
, and
Soyars
,
W. M.
,
2000
, “
Application of Foil Bearings to Helium Turbocompressor
,”
30th Turbomachinery Symposium
, Texas A&M University, Houston, TX.
5.
DellaCorte
,
C.
,
Radil
,
K. C.
,
Bruckner
,
R. J.
, and
Howard
,
S. A.
,
2008
, “
Design, Fabrication and Performance of Open Source Generation I and II Compliant Hydrodynamic Gas Foil Bearing
,”
Tribol. Trans.
,
51
(
13
), pp.
254
264
.
6.
Heshmat
,
H.
,
1994
, “
Advancements in the Performance of Aerodynamic Foil Journal Bearings: High Speed and Load Capacity
,”
ASME J. Tribol.
,
116
(
12
), pp.
287
295
.
7.
Heshmat
,
H.
,
2000
, “
Operation of Foil Bearing Beyond the Bending Critical Mode
,”
ASME J. Tribol.
,
122
(
11
), pp.
192
198
.
8.
Walton
,
J. F.
,
Heshmat
,
H.
, and
Tomaszewski
,
M. J.
,
2004
, “
Testing of a Small Turbomachinery/Turbojet Size Simulator Rotor Supported on Foil Bearings
,”
ASME
Paper No. GT2004-53647.
9.
Lee
,
Y. B.
,
Kim
,
T. H.
,
Kim
,
C. H.
,
Lee
,
N. S.
, and
Choi
,
D. H.
,
2004
, “
Unbalance Response of a Super-Critical Rotor Supported by Foil Bearings—Comparison With Test Results
,”
STLE Tribol. Trans.
,
47
(
11
), pp.
54
60
.
10.
Lee
,
Y. B.
,
Kim
,
T. H.
,
Kim
,
C. H.
,
Lee
,
N. S.
, and
Choi
,
D. H.
,
2004
, “
Dynamic Characteristics of a Flexible Rotor System Supported by Viscoelastic Foil Bearings (VEFB)
,”
Tribol. Int.
,
37
(
9
), pp.
679
687
.
11.
Lee
,
Y. B.
,
Kim
,
T. H.
, and
Kim
,
C. H.
,
2003
, “
Suppression of Subsynchronous Vibrations Due to Aerodynamic Response to Surge in a Two-Stage Centrifugal Compressor With Air Foil Bearings
,”
Tribol. Trans.
,
46
(
13
), pp.
428
434
.
12.
Sim
,
K.
,
Lee
,
Y.
, and
Kim
,
T. H.
,
2013
, “
Effects of Mechanical Preload and Bearing Clearance on Rotordynamic Performance of Lobed Gas Foil Bearings for Oil-Free Turbochargers
,”
Tribol. Trans.
,
56
(
12
), pp.
224
235
.
13.
San Andrés
,
L.
,
Rubio
,
D.
, and
Kim
,
T. H.
,
2007
, “
Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions
,”
ASME J. Eng. Gas Turbines Power
,
129
(
13
), pp.
850
857
.
14.
San Andrès
,
L.
, and
Kim
,
T. H.
,
2007
, “
Issues on Instability and Forced Nonlinearity in Gas Foil Bearing Supported Rotors
,”
AIAA
Paper No. 2007-5094.
15.
San Andrés
,
L.
, and
Kim
,
T. H.
,
2008
, “
Forced Nonlinear Response of Gas Foil Bearing Supported Rotors
,”
Tribol. Int.
,
41
(
8
), pp.
704
715
.
16.
San Andrés
,
L.
, and
Ryu
,
K.
,
2011
, “
On the Nonlinear Dynamics of Rotor‐Foil Bearing Systems: Effects of Shaft Acceleration, Mass Imbalance and Bearing Mechanical Energy Dissipation
,”
ASME
Paper No. GT2011‐45763.
17.
Pham
,
H. M.
, and
Bonello
,
P.
,
2013
, “
Efficient Techniques for the Computation of the Nonlinear Dynamics of a Foil-Air Bearing Rotor System
,”
ASME
Paper No. GT2013-94389.
18.
Pham
,
H. M.
, and
Bonello
,
P.
,
2014
, “
Nonlinear Dynamic Analysis of a Turbocharger on Foil-Air Bearings With Focus on Stability and Self-Excited Vibrations
,”
ASME
Paper No. GT2014-25176.
19.
Rudloff
,
L.
,
Arghir
,
M.
,
Bonneau
,
O.
,
Guingo
,
S.
,
Chemla
,
G.
, and
Renard
,
E.
,
2012
, “
Experimental Analysis of the Dynamic Characteristics of A Hybrid Aerostatic Bearing
,”
ASME J. Eng. Gas Turbines Power
,
134
(
18
), p.
082503
.
20.
Balducchi
,
F.
,
2013
, “
Analyse Expérimentale des Butées et des Paliers à Feuilles
,” Thèse de Doctorat, Université de Poitiers, Poitiers, France.
21.
Kar
,
R.
, and
Vance
,
J.
,
2007
, “
Subsynchronous Vibrations is Rotating Machinery—Methodologies to Identify Potential Instability
,”
ASME
Paper No. GT2007-27048.
22.
Constantinescu
,
V. N.
,
1969
,
Gas Lubrication
,
ASME Press
, New York.
23.
ISO,
2003
, “
Mechanical Vibration—Balance Quality Requirements for Rotors in a Constant (Rigid) State—Part 1: Specification and Verification of Balance Tolerances
,” International Organization for Standardization, Geneva, Switzerland, ISO Standard No. ISO 1940-1:2003(E).
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