Gas bearings in oil-free microturbomachinery for gas process applications and power generation (<400 kW) must be reliable and inexpensive, ensuring low drag power and thermal stability. Bump-type foil bearings (BFBs) and overleaf-type foil bearings are in use in specialized applications, though their development time (design and prototyping), exotic materials, and excessive manufacturing cost still prevent their widespread usage. Metal mesh foil bearings (MMFBs), on the other hand, are an inexpensive alternative that use common materials and no restrictions on intellectual property. Laboratory testing shows that prototype MMFBs perform similarly as typical BFBs, but offer significantly larger damping to dissipate mechanical energy due to rotor vibrations. This paper details a one-to-one comparison of the static and dynamic forced performance characteristics of a MMFB against a BFB of similar size and showcases the advantages and disadvantages of MMFBs. The bearings for comparison are a generation I BFB and a MMFB, both with a slenderness ratio L/D = 1.04. Measurements of rotor lift-off speed and drag friction at start-up and airborne conditions were conducted for rotor speeds to 70 krpm and under identical specific loads (W/LD = 0.06 to 0.26 bar). Static load versus bearing elastic deflection tests evidence a typical hardening nonlinearity with mechanical hysteresis, the MMFB showing two to three times more material damping than the BFB. The MMFB exhibits larger drag torques during rotor start-up, and shut-down tests though bearing lift-off happens at lower rotor speeds (∼15 krpm). As the rotor becomes airborne, both bearings offer very low drag friction coefficients, ∼0.03 for the MMFB and ∼0.04 for the BFB in the speed range 20–40 krpm. With the bearings floating on a journal spinning at 50 krpm, the MMFB dynamic direct force coefficients show little frequency dependency, while the BFB stiffness and damping increases with frequency (200–400 Hz). The BFB has a much larger stiffness and viscous damping coefficients than the MMFB. However, the MMFB material loss factor is at least twice as large as that in the BFB. The experiments show that the MMFB, when compared to the BFB, has a lower drag power and earlier lift-off speed and with dynamic force coefficients having a lesser dependency on whirl frequency excitation.

References

References
1.
Valco
,
M. J.
, and
DellaCorte
,
C.
, 2002, “
Emerging Oil-Free Turbomachinery Technology for Military Propulsion and Power Applications
,”
Proc. 23rd Army Sciences Conf.
, Orlando, FL, Dec. 2–5.
2.
Barnett
,
M. A.
, and
Silver
,
A.
, 1970, “
Application of Air Bearings to High-Speed Turbomachinery
,” SAE Paper No. 700720.
3.
Peng
,
Z.-C.
, and
Khonsari
,
M. M.
, 2004, “
Hydrodynamic Analysis of Compliant Foil Bearings With Compressible Air Flow
,”
ASME J. Tribol.
,
126
(
3
), pp.
542
546
.
4.
Lee
,
Y. B.
,
Park
,
D. J.
, and
Kim
,
C. H.
, 2008, “
Stability and Efficiency of Oil-Free Turbocharger With Foil Bearings for SUV
,” SAE Paper No. 08SFI-0083.
5.
Howard
,
S. A.
,
Bruckner
,
R. J.
,
DellaCorte
,
C.
, and
Radil
,
K. C.
, 2008, “
Preliminary Analysis for an Optimized Oil-Free Rotorcraft Engine Concept
,” NASA Paper No. NASA/TM-2008-215064, ARL-TR-4398.
6.
Walser
,
M. L.
, 2010, “
Carbon Footprint
,” Encyclopedia of Earth, accessed Oct. 25, 2011, http://www.eoearth.org/article/Carbon_footprinthttp://www.eoearth.org/article/Carbon_footprint
7.
San Andrés
,
L.
, and
Kim
,
T. H.
, 2008, “
Forced Nonlinear Response of Gas Foil Bearing Supported Rotors
,”
Tribol. Int.
,
41
, pp.
704
715
.
8.
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.
9.
San Andrés
,
L.
, and
Chirathadam
,
T. A.
, 2011, “
Metal Mesh Foil Bearing: Effect of Motion Amplitude, Rotor Speed, Static Load, and Excitation Frequency on Force Coefficients
,”
ASME J. Eng. Gas Turbines Power
,
133
(
12
), p.
122503
.
10.
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 Bearings
,”
Tribol. Trans.
,
51
, pp.
254
264
.
11.
DellaCorte
,
C.
, and
Valco
,
M.
, 2000, “
Load Capacity Estimation of Foil Air Journal Bearing for Oil-Free Turbomachinery Applications
,”
Tribol Trans.
,
43
(
4
), pp.
795
801
.
12.
DellaCorte
,
C.
, 2010, “
Stiffness and Damping Coefficient Estimation of Compliant Surface Gas Bearings for Oil-Free Turbomachinery
,”
Proc. of STLE/ASME 2010 Int. J. Tribol. Conference
, San Francisco, CA, Oct. 17–20, Paper No. IJTC2010-41232.
13.
Bruckner
,
R. J.
, and
Puleo
,
B. J.
, 2008, “
Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperatures
,” ASME Paper No. GT2008-50174.
14.
Howard
,
S. A.
,
DellaCorte
,
C.
,
Valco
,
M. J.
,
Prahl
,
J. M.
, and
Heshmat
,
H.
, 2001, “
Steady-State Stiffness of Foil Air Journal Bearings at Elevated Temperatures
,”
Tribol. Trans.
,
44
(
3
), pp.
489
493
.
15.
Howard
,
S.
,
DellaCorte
,
C.
,
Valco
,
M. J.
,
Prahl
,
J. M.
, and
Heshmat
,
H.
, 2001, “
Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing
,”
Tribol. Trans.
,
44
(
4
), pp.
657
663
.
16.
San Andrés
,
L.
,
Kim
,
T. H.
,
Chirathadam
,
T. A.
, and
Ryu
,
K.
, 2010, “
Measurements of Drag Torque, Lift-Off Journal Speed and Temperature in a Metal Mesh Foil Bearing
,”
ASME J. Eng. Gas Turbines Power
,
132
(
11
), p.
112503
.
17.
DellaCorte
,
C.
, 1997, “
A New Foil Air Bearing Test Rig for Use to 700 C and 70,000 rpm
,” NASA Paper No. NASA TM-107405.
18.
Heshmat
,
H.
, 1994, “
Advancements in the Performance of Aerodynamic Foil Journal Bearings: High Speed and Load Capacity
,”
ASME J. Tribol.
,
116
, pp.
287
295
.
19.
San Andrés
,
L.
, and
Chirathadam
,
T. A.
, 2011, “
Identification of Rotordynamic Force Coefficients of a Metal Mesh Foil Bearing Using Impact Load Excitations
,”
ASME J. Eng. Gas Turbines Power
,
133
(
11
), p.
112501
.
20.
Radil
,
K. C.
, and
DellaCorte
,
C.
, 2009, “
A Three-Dimensional Foil Bearing Performance Map Applied to Oil-Free Turbomachinery
,” NASA Paper No. NASA APRL-TR-4473.
21.
Bruckner
,
R. J.
,
DellaCorte
,
C.
, and
Dykas
,
B. D.
, 2006, “
An Analytic Approach to the Foil Gas Bearing Performance Map
,”
Proc. of STLE/ASME 2006 International Joint Tribology Conf.
, San Antonio, Texas, Oct. 23–25, Paper No. IJTC2006-12364.
22.
San Andrés
,
L.
,
Chirathadam
,
T. A.
, and
Kim
,
T. H.
, 2010, “
Measurement of Structural Stiffness and Damping Coefficients in a Metal Mesh Foil Bearing
,”
ASME J. Eng. Gas Turbines Power
,
132
(
3
), p.
032503
.
23.
Lee
,
Y.-B.
,
Park
,
D.-J.
, and
Kim
,
C.-H.
, 2006, “
Numerical Analysis for Bump Foil Journal Bearing Considering Top Foil Effect and Experimental Investigation
,”
7th IFToMM-Conference on Rotor Dynamics
, Vienna, Austria, Sept. 25–28, Paper No. 229.
24.
Rudloff
,
L.
,
Arghir
,
M.
,
Bonneau
,
O.
, and
Matta
,
P.
, 2011, “
Experimental Analyses of a First Generation Foil Bearing: Startup Torque and Dynamic Coefficients
,”
ASME J. Eng. Gas Turbines Power
,
133
, p.
092501
.
25.
Rubio
,
D.
, and
San Andrés
,
L.
, 2006, “
Bump-Type Foil Bearing Structural Stiffness: Experiments and Predictions
,”
ASME J. Eng. Gas Turbines Power
,
128
(
3
), pp.
653
660
.
26.
Lee
,
Y.-B.
,
Kim
,
C. H.
,
Kim
,
T. H.
, and
Kim
,
T. Y.
, 2011, “
Effects of Mesh Density on Static Load Performance of Metal Mesh Gas Foil Bearings
,” ASME Paper No. GT2011-46589.
27.
San Andrés
,
L.
,
Camero
,
J.
,
Muller
,
S.
,
Chirathadam
,
T. A.
, and
Ryu
,
K.
, 2010, “
Measurements of Drag Torque, Lift Off Speed, and Structural Parameters in 1st Generation Floating Gas Foil Bearing
,”
Proc. 8th IFToMM Int. Conf. on Rotordynamics
, Seoul, Korea, Sept. 12–15.
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