The dynamic characteristics of a hybrid aerostatic bearing are experimentally investigated on a test rig consisting of a rigid rotor driven by an impulse turbine. The rotor is horizontally mounted and is supported by two identical aerostatic bearings. Both the impulse turbine and the aerostatic hybrid bearings are fed with air. The feeding pressures in the bearings can be as high as 7 bars and rotation speeds can reach 60 krpm so the dynamic load on the rotor is much larger than the static load engendered by its weight. Excitations are applied either via an impact hammer or via unbalancing masses. The measuring instruments record the bearing feeding pressures, the rotation speed, the impact force, the displacements of the two bearings, and the bearing housing accelerations. The experimental data together with the equations of motion of the rotor enables the identification of the dynamic coefficients of the bearings. A second identification procedure using the same impact hammer is also possible as force transducers are mounted between the bearing housing and its support. The dynamic coefficients of the bearings can then be obtained from the equation of motion of its housing. Unbalance response provide a convenient way for verifying the accuracy of the identified dynamic coefficients. Therefore these coefficients are injected in the equations of motion of a four degrees of freedom rigid rotor and the theoretical results are compared with values measured on the test rig. Comparisons show that predictions are acceptable but become less accurate at high rotation speeds where large dynamic forces are needed for exciting the corresponding synchronous frequencies.

References

References
1.
Constantinescu
,
V. N.
, 1969,
Gas Lubrication
,
The American Society of Mechanical Engineering
,
New York
(translated from Romanian, Lubrificatia cu gaze, Editura Academiei, 1963).
2.
Rieger
,
N. F.
, 1967,
Design of Gas Bearings
,
Mechanical Technology
, Inc., notes supplemented to the RPI-MTI course on gas bearing design.
3.
Powell
,
J. W.
, 1970,
Design of Aerostatic Bearings
,
The Machinery Publishing Co
.,
Brighton, UK
.
4.
Gross
,
W. A.
,
Match
,
L. A.
,
Castelli
,
V.
,
Eshel
,
A.
,
Vohr
,
J. H.
, and
Wildmann
,
M.
, 1980,
Fluid Film Lubrication
,
Wiley
,
New York
.
5.
Diaz
,
S.
,
Beets
,
T.
,
Dunn
,
G.
, and
San Andrés
,
L.
, 1999, “
High Speed Test Rig for Identification of Gas Journal Bearing Performance: Design, Constraints and Fabrication
,” TRC-RD-1-99.
6.
Zhu
,
X.
, and
San Andrés
,
L.
, 2005, “
Experimental Response of a Rotor Supported on Rayleigh Step Gas Bearings
,” ASME Paper GT 2005-68296.
7.
Wilde
,
D. A.
, and
San Andrés
,
L.
, 2006, “
Experimental Response of Simple Gas Hybrid Bearings for Oil-Free Turbomachinery
,”
ASME J. Eng. Gas Turbines Power
,
128
, pp.
626
633
.
8.
Ryu
,
K.
, and
San Andrés
,
L.
, 2006, “
Measurements of Rotordynamic Response of a Rotor Supported on Hybrid Flexure Pivot Tilting Pad Gas Bearings
,” Paper IJTC 2006-12371,
ASME/STLE International Joint Tribology Conference
,
San Antonio
,
TX
, October 2006.
9.
Zhu
,
S.
, and
San Andrés
,
L.
, 2007, “
Rotordynamic Performance of Flexure Pivot Hydrostatic Gas Bearings for Oil-Free Turbomachinery
,”
ASME J. Eng. Gas Turbines Power
,
129
(
4
), pp.
1020
1027
.
10.
Belforte
,
G.
,
Raparelli
,
T.
,
Viktorov
,
V.
,
Trivella
,
A.
, and
Colombo
,
F.
, 2006, “
An Experimental Study of High Speed Rotors Supported by Air Bearings; Test Rig and First Experimental Results
,”
Tribol. Int.
,
39
, pp.
834
845
.
11.
Belforte
,
G.
,
Raparelli
,
T.
,
Viktorov
,
V.
,
Trivella
,
A.
, and
Colombo
,
F.
, 2006, “
Study of A High Speed Electrospindle With Air Bearings
,”
European Conference on Tribology, ECOTRIB 2007
, June 12–15, Vol.
2
, pp.
969
982
,
Ljubliana, Slovenia
.
12.
Colombo
,
F.
, and
Trivella
,
A.
, 2008, “
Air Bearing Testing
,”
Int. J. Fluid Power
,
9
(
3
), pp.
45
53
.
13.
De Santiago
,
O. C.
, 2002, “
Identification of Bearing Supports’ Force Coefficients From Rotor Responses Due to Imbalances and Impact Loads
,” PhD dissertation, Texas A&M University.
14.
Bonneau
,
O.
,
Frêne
,
J.
, and
Arghir
,
M.
, 2008, “
A New Test Rig for Measuring the Dynamic Characteristics of Labyrinth Seals and Hybrid Bearings at Very High Reynolds Numbers
,”
35th Leeds-Lyon Symposium on Tribology
, 9–12 September,
Leeds
,
England
.
15.
Murphy
,
B. T.
, and
Wagner
,
M. N.
, 1991, “
Measurement of Rotordynamic Coefficients for a Hydrostatic Radial Bearing
,”
ASME J. Tribol.
,
113
(
2
), pp.
518
252
.
You do not currently have access to this content.