In noncontact annular labyrinth seals used in turbomachinery, fluid prerotation in the direction of shaft rotation effectively increases fluid velocity in the circumferential direction and generates fluid forces with potential destabilizing effects to be exerted on the rotor. Swirl brakes are typically employed to reduce the fluid prerotation at the inlet of the seal. The inlet flow separates as it follows the swirl brakes, and the ratio between tangential component of the velocity at the seal, and the velocity of the rotor surface varies consequently. Effective swirl brakes can significantly suppress the destabilizing fluid forces as it is effectively reducing the tangential velocity. The literature shows that leakage rate can also be reduced by using swirl brakes with “negative-swirl.” In this study, a labyrinth seal with inlet swirl brakes is selected from the literature and considered the baseline design. The seal performance is evaluated using ANSYS-cfx. The design of experiments (DOEs) approach is used to investigate the effects of various design variables on the seal performance. The design space consists of the swirl brake's length, width, curvature at the ends, the tilt angle, as well as the number of swirl brakes in the circumferential direction. Simple random sampling method with Euclidean distances for the design matrix is used to generate the design points. Steady-state computational fluid dynamics simulations are then performed for each design point to analyze the performance of the swirl brakes. Quadratic polynomial fitting is used to evaluate the sensitivity of the average circumferential velocity with respect to the design variables, which gives a qualitative estimation for the performance of the swirl brakes. These results assist in creating a better understanding of which design variables are critical and more effective in reduction of the destabilizing forces acting on the rotor, and thus will support the swirl brake design for annular pressure seals.

References

References
1.
Benckert
,
H.
, and
Wachter
,
J.
, 1980, “
Flow Induced Spring Constants of Labyrinth Seals
,”
The Second International Conference on Vibrations Rotating Machinery
, Cambridge, UK, Sept. 1–4, pp.
53
63
.
2.
Benckert
,
H.
, and
Wachter
,
J.
,
1980
, “
Flow Induced Spring Coefficients of Labyrinth Seals for Applications in Rotor Dynamics
,”
The Rotordynamic Instability Problems in High-Performance Turbomachinery Workshop
, College Station, TX, May 12–14, pp. 189–212.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800021216.pdf
3.
Childs
,
D.
, and
Hale
,
K.
,
1994
, “
A Test Apparatus and Facility to Identify the Rotordynamic Coefficients of High-Speed Hydrostatic Bearings
,”
ASME J.Tribol.
,
116
(
2
), pp.
337
344
.
4.
Franchek
,
N. M.
, and
Childs
,
D. W.
,
1994
, “
Experimental Test-Results for 4 High-Speed, High-Pressure, Orifice-Compensated Hybrid Bearings
,”
ASME J. Tribol.
,
116
(
1
), pp.
147
153
.
5.
Moore
,
J.
,
Walker
,
S.
, and
Kuzdal
,
M.
, 2002, “
Rotordynamic Stability Measurement During Full-Load, Full-Pressure Testing of a 6000 Psi Reinjection Centrifugal Compressor
,”
31st Turbomachinery Symposium
, Houston, TX, pp. 29–38.http://oaktrust.library.tamu.edu/handle/1969.1/163317
6.
Weatherwax
,
M.
, and
Childs
,
D. W.
,
2003
, “
Theory Versus Experiment for the Rotordynamic Characteristics of a High Pressure Honeycomb Annular Gas Seal at Eccentric Positions
,”
ASME J. Tribol.
,
125
(
2
), pp.
422
429
.
7.
Picardo
,
A.
, and
Childs
,
D. W.
,
2005
, “
Rotordynamic Coefficients for a Tooth-on-Stator Labyrinth Seal at 70 Bar Supply Pressures: Measurements Versus Theory and Comparisons to a Hole-Pattern Stator Seal
,”
ASME J. Eng. Gas Turbines Power
,
127
(
4
), pp.
843
855
.
8.
Gans
,
B.
,
2007
, “
Reverse-Swirl Brakes Retrofitting With Brush Seals
,”
Turbomach. Int.
, pp.
48
49
.
9.
Brown
,
P. D.
, and
Childs
,
D. W.
,
2012
, “
Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl
,”
ASME J. Eng. Gas Turbines Power
,
134
(
12
), p.
122503
.
10.
Migliorini
,
P. J.
,
Untaroiu
,
A.
,
Wood
,
H. G.
, and
Allaire
,
P. E.
,
2012
, “
A Computational Fluid Dynamics/Bulk-Flow Hybrid Method for Determining Rotordynamic Coefficients of Annular Gas Seals
,”
ASME J. Tribol.
,
134
(
2
), p.
022202
.
11.
Untaroiu
,
A.
,
Hayrapetian
,
V.
,
Untaroiu
,
C. D.
,
Wood
,
H. G.
,
Schiavello
,
B.
, and
McGuire
,
J.
,
2013
, “
On the Dynamic Properties of Pump Liquid Seals
,”
ASME J. Fluid Eng.
,
135
(
5
), p.
051104
.
12.
Mehta
,
N. J.
, and
Childs
,
D. W.
,
2013
, “
Measured Comparison of Leakage and Rotordynamic Characteristics for a Slanted-Tooth and a Straight-Tooth Labyrinth Seal
,”
ASME J. Eng. Gas Turbines Power
,
136
(
1
), p.
012501
.
13.
Migliorini
,
P. J.
,
Untaroiu
,
A.
,
Witt
,
W. C.
,
Morgan
,
N. R.
, and
Wood
,
H. G.
,
2014
, “
Hybrid Analysis of Gas Annular Seals With Energy Equation
,”
ASME J. Tribol.
,
136
(
3
), p.
031704
.
14.
Childs
,
D. W.
,
Mclean
,
J. E.
,
Zhang
,
M.
, and
Arthur
,
S. P.
,
2015
, “
Rotordynamic Performance of a Negative-Swirl Brake for a Tooth-on-Stator Labyrinth Seal
,”
ASME J. Eng. Gas Turbines Power
,
138
(
6
), p.
062505
.
15.
Untaroiu
,
A.
,
Liu
,
C.
,
Migliorini
,
P. J.
,
Wood
,
H. G.
, and
Untaroiu
,
C. D.
,
2014
, “
Hole-Pattern Seals Performance Evaluation Using Computational Fluid Dynamics and Design of Experiment Techniques
,”
ASME J. Eng. Gas Turbines Power
,
136
(
10
), p.
102501
.
16.
Untaroiu
,
A.
,
Untaroiu
,
C. D.
,
Wood
,
H. G.
, and
Allaire
,
P. E.
,
2012
, “
Numerical Modeling of Fluid-Induced Rotordynamic Forces in Seals With Large Aspect Ratios
,”
ASME J. Eng. Gas Turbines Power
,
135
(
1
), p.
012501
.
17.
Morgan
,
N. R.
,
Wood
,
H. G.
, and
Untaroiu
,
A.
,
2015
, “
Numerical Optimization of Leakage by Multifactor Regression of Trapezoidal Groove Geometries for a Balance Drum Labyrinth Seal
,”
ASME
Paper No. GT2015-43794.
18.
Migliorini
,
P. J.
,
Untaroiu
,
A.
, and
Wood
,
H. G.
,
2014
, “
A Numerical Study on the Influence of Hole Depth on the Static and Dynamic Performance of Hole-Pattern Seals
,”
ASME J. Tribol.
,
137
(
1
), p.
011702
.
19.
Jin
,
H. X.
, and
Untaroiu
,
A.
,
2016
, “
Elliptical Shape Hole-Pattern Seals Performance Evaluation Using Design of Experiments Technique
,”
ASME
Paper No. FEDSM2016-7687.
You do not currently have access to this content.