Experimental results indicating negative direct static stiffness of highly eccentric straight gas annular seals were very recently presented by Childs and Arthur (2013, “Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios,” ASME Paper No. GT2013-94201). This instability occurred at zero rotation speed and at high eccentricities. Up to then only gas annular seals with zero rotation speed, operating in centered position and with choked exit section were known as being susceptible of developing negative direct static stiffness. The seals and the working conditions presented by Childs and Arthur (2013, “Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios,” ASME Paper No. GT2013-94201) had clearly no choked exit section. The present work advances a theoretical explanation of results reported by Childs and Arthur (2013, “Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios,” ASME Paper No. GT2013-94201). The analysis is based on the numerical solution of the bulk flow equations of the flow in the annular seal. Theoretical results show a negative static stiffness at high eccentricities and zero rotation speeds. Other seal geometries and working conditions were tested and showed that the decrease of the direct static stiffness at high eccentricities and zero rotation speeds is a characteristic of all straight annular seals whether the fluid is compressible or not. Nevertheless with increasing rotation speed, the static stiffness becomes again positive and may increase with increasing eccentricity. The negative static stiffness is then limited to very specific working conditions: high eccentricities and zero rotation speed.

References

References
1.
Childs
,
D. W.
,
1993
,
Turbomachinery Rotordynamics
,
Wiley
,
New York
.
2.
Childs
,
D. W.
, and
Arthur
,
S. P.
,
2013
, “
Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios
,”
ASME
Paper No. GT2013-94201. 10.1115/GT2013-94201
3.
Arghir
,
M.
,
Defaye
,
C.
, and
Frêne
,
J.
,
2007
, “
The Lomakin Effect in Anular Gas Seals Under Choked Flow Conditions
,”
ASME J. Eng. Gas Turbines Power
,
129
(
14
), pp.
1028
1034
.10.1115/1.2434344
4.
Hassini
,
M. A.
, and
Arghir
,
M.
,
2013
, “
Phase Change and Choked Flow Effects on Rotordynamic Coefficients of Cryogenic Annular Seals
,”
ASME J. Tribol.
,
135
(
4
), p.
042201
.10.1115/1.4024376
5.
Massey
,
I.
,
1985
, “
Subsynchronous Vibration Problems in High-Speed Multistage Centrifugal Pumps
,”
14th Turbomachinery Symposium
, Texas A&M University, Houston, TX, Oct. 22–24, pp.
11
16
.
6.
Valantas
,
R.
, and
Bolleter
,
U.
,
1988
, “
Solutions to Abrasive Wear-Related Rotordynamic Instability Problems in Prudhoe Bay Injection Pumps
,”
Fifth International Pump Users Symposium
, Texas A&M University, Houston, May 10–12, pp.
3
10
.
7.
Black
,
H.
, and
Jenssen
,
D.
,
1969
, “
Dynamic Hybrid Bearing Characteristics of Annular Controlled Leakage Seals
,”
Proc. Inst. Mech. Eng., Part 3N
,
184
(
14
), pp.
92
100
.10.1243/PIME_CONF_1969_184_427_02
8.
Marquette
,
O.
,
Childs
,
D. W.
, and
San Andrés
,
L.
,
1997
, “
Eccentricity Effects on the Rotordynamic Coefficients of Plain Annular Seals: Theory Versus Experiment
,”
ASME J. Tribol.
,
119
(
3
), pp.
443
448
.10.1115/1.2833515
9.
Constantinescu
,
V. N.
,
1995
,
Laminar Viscous Flow
,
Springer-Verlag
, New York, pp.
403
412
.
10.
Launder
,
B. E.
, and
Leschziner
,
M.
,
1978
, “
Flow in Finite-Width, Journal Bearings Including Inertia Effects
,”
ASME J. Lubr. Technol.
,
100
(
13
), pp.
330
338
.10.1115/1.3453181
11.
San Andrés
,
L.
,
1991
, “
Analysis of Variable Fluid Properties, Turbulent Annular Seals
,”
ASME J. Tribol.
,
113
(
14
), pp.
694
702
.10.1115/1.2920681
12.
Hirs
,
G.
,
1973
, “
A Bulk Flow Theory for Turbulence in Lubricant Films
,”
ASME J. Lubr. Technol.
,
95
(
12
), pp.
137
146
.10.1115/1.3451752
13.
Colebrook
,
C. F.
,
1939
, “
Turbulent Flow in Pipes, With Particular Reference to the Transition Between the Smooth and Rough Pipe Laws
,”
J. Inst. Civ. Eng.
,
11
(
14
), pp.
133
156
.10.1680/ijoti.1939.13150
14.
Zirkelback
,
N.
, and
San Andrés
,
L.
,
1998
, “
Bulk-Flow Model for the Transition to Turbulence Regime in Annular Seals
,”
STLE Tribol. Trans.
,
39
(
14
), pp.
835
845
.10.1080/10402009608983602
15.
Arghir
,
M.
, and
Frêne
,
J.
,
2001
, “
A Triangle Based Finite Volume Method for the Integration of Lubrication's Incompressible Bulk Flow Equation
,”
ASME J. Tribol.
,
123
(
11
), pp.
118
124
.10.1115/1.1326444
16.
Arghir
,
M.
, and
Frêne
,
J.
,
2001
, “
Numerical Solution of Lubrication's Compressible Bulk-Flow Equations: Applications to Annular Seals Analysis
,”
ASME
Paper No. 2001-GT-0117. 10.1115/2001-GT-0117
17.
Kerr
,
B. G.
,
2001
, “
Experimental and Theoretical Rotordynamic Coefficients and Leakage of Straight Smooth Annular Gas Seals
,” Master's thesis, Texas A&M University, College Station, TX.
18.
Alexander
,
C. R.
,
Childs
,
D. W.
, and
Yang
,
Z.
,
1995
, “
Theory Versus Experiment for the Rotordynamic Characteristics of a Smooth Annular Gas Seal at Eccentric Positions
,”
ASME J. Tribol.
,
117
(
1
), pp.
148
152
.10.1115/1.2830591
You do not currently have access to this content.