Annular gas seals for compressors and turbines are designed to operate in a nominally centered position in which the rotor and stator are at concentric condition, but due to the rotor–stator misalignment or flexible rotor deflection, many seals usually are suffering from high eccentricity. The centering force (represented by static stiffness) of an annular gas seal at eccentricity plays a pronounced effect on the rotordynamic and static stability behavior of rotating machines. The paper deals with the leakage and static stability behavior of a fully partitioned pocket damper seal (FPDS) at high eccentricity ratios. The present work introduces a novel mesh generation method for the full 360 deg mesh of annular gas seals with eccentric rotor, based on the mesh deformation technique. The leakage flow rates, static fluid-induced response forces, and static stiffness coefficients were solved for the FPDS at high eccentricity ratios, using the steady Reynolds-averaged Navier–Stokes solution approach. The calculations were performed at typical operating conditions including seven rotor eccentricity ratios up to 0.9 for four rotational speeds (0 rpm, 7000 rpm, 11,000 rpm, and 15,000 rpm) including the nonrotating condition, three pressure ratios (0.17, 0.35, and 0.50) including the choked exit flow condition, two inlet preswirl velocities (0 m/s, 60 m/s). The numerical method was validated by comparisons to the experiment data of static stiffness coefficients at choked exit flow conditions. The static direct and cross-coupling stiffness coefficients are in reasonable agreement with the experiment data. An interesting observation stemming from these numerical results is that the FPDS has a positive direct stiffness as long as it operates at subsonic exit flow conditions; no matter the eccentricity ratio and rotational speed are high or low. For the choked exit condition, the FPDS shows negative direct stiffness at low eccentricity ratio and then crosses over to positive value at the crossover eccentricity ratio (0.5–0.7) following a trend indicative of a parabola. Therefore, the negative static direct stiffness is limited to the specific operating conditions: choked exit flow condition and low eccentricity ratio less than the crossover eccentricity ratio, where the pocket damper seal (PDS) would be statically unstable.

References

1.
Chupp
,
R. E.
,
Hendricks
,
R. C.
,
Lattime
,
S. B.
, and
Steinetz
,
B. M.
,
2006
, “
Sealing in Turbomachinery
,”
J. Propul. Power
,
22
(
2
), pp.
313
349
.
2.
Muszynska
,
A.
,
2005
,
Rotor Dynamics
,
CRC Press
,
Boca Raton, FL
, pp.
214
222
.
3.
Vance
,
J. M.
,
2010
,
Machinery Vibration and Rotordynamics
,
Wiley
,
New York
, pp.
271
278
.
4.
Childs
,
D. W.
, and
Vance
,
J. M.
,
1997
, “
Annular Gas Seals and the Rotordynamics of Compressors and Turbines
,”
26th Turbomachinery Symposium
, Houston, TX, Sept. 14–18, pp.
201
220.
http://turbolab.tamu.edu/proc/turboproc/T26/Vol26021.pdf
5.
Vance
,
J.
, and
Schultz
,
R.
,
1993
, “
A New Damper Seal for Turbomachinery
,” 14th Biennial ASME Conference on Vibration and Noise, Albuquerque, NM, Sept. 19–22, pp. 139–148.
6.
Richards
,
R. L.
,
Vance
,
J. M.
,
Paquette
,
D. J.
, and
Zeidan
,
F. Y.
,
1995
, “
Using a Damper Seal to Eliminate Subsynchronous Vibrations in Three Back-to-Back Compressors
,”
24th Turbomachinery Symposium
, College Station, TX, Sept. 26–28, pp.
370
376
.http://turbolab.tamu.edu/proc/turboproc/T24/T2459-71.pdf
7.
Vance
,
J. M.
, and
Li
,
J.
,
1996
, “
Test Results of a New Damper Seal for Vibration Reduction in Turbomachinery
,”
ASME J. Eng. Gas Turbines Power
,
118
(4), pp.
843
846
.
8.
Ransom
,
D. L.
,
1997
, “
Identification of Dynamic Force Coefficients of a Labyrinth and Gas Damper Seal Using Impact Load Excitations
,”
Ph.D. thesis
, Texas A&M University, College Station, TX.http://oaktrust.library.tamu.edu/handle/1969.1/ETD-TAMU-1997-THESIS-R37
9.
Laos
,
H. E.
,
1999
, “
Rotordynamic Effect of Pocket Damper Seals
,” Ph.D. dissertation, Texas A&M University, College Station, TX.
10.
Ertas
,
B. H.
,
Gamal
,
A. M.
, and
Vance
,
J. M.
,
2006
, “
Rotordynamic Force Coefficients of Pocket Damper Seals
,”
ASME J. Turbomach.
,
128
(4), pp.
725
737
.
11.
Ertas
,
B. H.
,
Delgado
,
A.
, and
Vannini
,
G.
,
2012
, “
Rotordynamic Force Coefficients for Three Types of Annular Gas Seals With Inlet Preswirl and High Differential Pressure Ratio
,”
ASME J. Eng. Gas Turbines Power
,
134
(
4
), p.
042503
.
12.
Li
,
Z.
,
Li
,
J.
, and
Feng
,
Z.
,
2015
, “
Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals—Part I: Effects of Pressure Ratio, Rotational Speed, and Inlet Preswirl
,”
ASME J. Eng. Gas Turbines Power
,
137
(
3
), p.
032503
.
13.
Li
,
Z.
,
Li
,
J.
, and
Feng
,
Z.
,
2016
, “
Numerical Comparison of Rotordynamic Characteristics for a Fully Partitioned Pocket Damper Seal and a Labyrinth Seal With High Positive and Negative Inlet Preswirl
,”
ASME J. Eng. Gas Turbines Power
,
138
(
4
), p.
042505
.
14.
Ertas
,
B. H.
, and
Vance
,
J. M.
,
2007
, “
Rotordynamic Force Coefficients for a New Pocket Damper Seals
,”
ASME J. Tribol.
,
129
(2), pp.
365
374
.
15.
Li
,
Z.
,
Li
,
J.
, and
Feng
,
Z.
,
2015
, “
Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals—Part II: Effects of Partition Wall Type, Partition Wall Number, and Cavity Depth
,”
ASME J. Eng. Gas Turbines Power
,
137
(
3
), p.
032504
.
16.
Vannini
,
G.
,
Cioncoini
,
S.
,
Vescovo
,
G.
, and
Rovini
,
M.
,
2014
, “
Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
,”
ASME J. Eng. Gas Turbines Power
,
136
(
10
), p.
022501
.
17.
Gamal
,
A. M.
,
2007
, “
Leakage and Rotordynamic Effects of Pocket Damper Seals and See-Through Labyrinth Seals
,”
Ph.D. dissertation
, Mechanical Engineering Department, Texas A&M University, College Station, TX.http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.475.6673&rep=rep1&type=pdf
18.
Armendariz
,
R. A.
,
2002
, “
Rotordynamic Analysis of a Pocket Damper Seal Using Circular Orbits of Large Amplitude
,” Ph.D. dissertation, Mechanical Engineering Department, Texas A&M University, College Station, TX.
19.
Li
,
J.
,
San Andre´s
,
L.
, and
Vance
,
J. M.
,
1999
, “
A Bulk-Flow Analysis of Multiple-Pocket Gas Damper Seals
,”
ASME J. Eng. Gas Turbines Power
,
121
(
2
), pp.
355
362
.
20.
Li
,
Z.
,
Li
,
J.
, and
Yan
,
X.
,
2013
, “
Multiple Frequencies Elliptical Whirling Orbit Model and Transient RANS Solution Approach to Rotordynamic Coefficients of Annual Gas Seals Prediction
,”
ASME J. Vib. Acoust.
,
135
(
3
), p.
031005
.
21.
Li
,
Z.
,
Li
,
J.
, and
Feng
,
Z.
,
2016
, “
Comparison of Rotordynamic Characteristics Predictions for Annular Gas Seals Using the Transient Computational Fluid Dynamic Method Based on Different Single-Frequency and Multi-frequency Rotor Whirling Models
,”
ASME J. Tribol.
,
138
(
1
), p.
011701
.
22.
Childs
,
D. W.
, and
Arthur
,
S. P.
,
2013
, “
Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios
,”
ASME
Paper No. GT2013-94201.
23.
Arghir
,
M.
,
Defaye
,
C.
, and
Frêne
,
J.
,
2007
, “
The Lomakin Effect in Annular Gas Seals Under Choked Flow Conditions
,”
ASME J. Eng. Gas Turbines Power
,
129
(
14
), pp.
1028
1034
.
24.
Arghir
,
M.
, and
Mariot
,
A.
,
2015
, “
About the Negative Direct Static Stiffness of Highly Eccentric Straight Annular Seals
,”
ASME J. Eng. Gas Turbines Power
,
137
(
8
), p.
082508
.
25.
Gamal
,
A. M.
,
2003
, “
Analytical and Experimental Evaluation of the Leakage and Stiffness Characteristics of High Pressure Pocket Damper Seals
,”
M.S. thesis
, Mechanical Engineering Department, Texas A&M University, College Station, TX.http://oaktrust.library.tamu.edu/handle/1969.1/16
26.
Ertas
,
B. H.
,
2005
, “
Rotordynamic Force Coefficients of Pocket Damper Seals
,”
Ph.D. Dissertation
, Texas A&M University, College Station, TX, May 2005.http://oaktrust.library.tamu.edu/handle/1969.1/2592
27.
ANSYS,
2006
, ANSYS CFX-Solver Theory Guide. Release 11.0,
ANSYS Inc.
,
Canonsburg, PA
.
28.
Childs
,
D. W.
,
1993
,
Turbomachinery Rotordynamics: Phenomena, Modeling and Analysis
,
Wiley
,
New York
, p.
292
.
You do not currently have access to this content.