Among the various types of seals used in gas turbine secondary air system to guarantee sufficient confinement of the main gas path, honeycomb seals perform well in terms of enhanced stability and reduced leakage flow. Due to the large amount of honeycomb cells typically employed in real seals, it is generally convenient to treat the sealing effect of the honeycomb pack as an increased distributed friction factor on the plain top surface. That is why, this analysis is focused on a simple configuration composed by a honeycomb facing a flat plate. In order to evaluate the sealing performance of such honeycomb packs, an experimental campaign was carried out on a stationary test rig where the effects of shaft rotation are neglected. The test rig was designed to analyze different honeycomb geometries so that a large experimental database could be created to correlate the influence of each investigated parameter. Honeycomb seals were varied in terms of hexagonal cell dimension and depth in a range that represents well actual honeycomb packs employed in industrial compressors. For each geometry, seven different clearances were tested. This work reports the findings of such experimental campaign whose results were analyzed in order to guide actual seals design and effective estimates of shaft loads. Static pressure measurements reveal that the effects of investigated geometrical parameters on friction factor correlate well with a corrected Mach number based on the cell depth. The presence of acoustic effects in the seals was further investigated by means of hot wire anemometry. Acoustic forcing due to flow cavity interaction was found to be characterized by a constant Strouhal number based on cell geometry. Numerical simulations helped in the identification of system eigenmodes and eigenfrequencies providing an explanation to the friction factor enhancement triggered at a certain flow speed. Finally, the generated dataset was tested comparing the predicted leakage flow with experimental data of actual seals (with high pressure and high rotational speed) showing a very good agreement.

References

References
1.
Childs
,
D. W.
, and
Vance
,
J. M.
,
1997
, “
Annular Gas Seals and Rotordynamics of Compressors and Turbines
,”
26th Turbomachinery Symposium
, Turbomachinery Laboratory,
Texas A&M University
,
College Station, TX
, Sept. 14–16, pp.
201
220
.
2.
Childs
,
D. W.
,
Elrod
,
D.
, and
Hale
,
K.
,
1989
, “
Annular Honeycomb Seals: Test Results for Leakage and Rotordynamic Coefficients; Comparisons to Labyrinth and Smooth Configurations
,”
ASME J. Tribol.
,
111
(
2
), pp.
293
300
.
3.
Childs
,
D. W.
, and
Kleynhans
,
G. F.
,
1992
, “
Experimental Rotordynamic and Leakage Results For Short (l/d = 1/6) Honeycomb and Smooth Annular Pressure Seals
,”
5th International Conference on Vibrations in Rotating Machinery
,
Bath, UK
, Sept. 7–10, Vol.
111
, pp.
305
311
.
4.
Al-Qutub
,
A. M.
,
Elrod
,
D.
, and
Coleman
,
H. W.
,
2000
, “
A New Friction Factor Model and Entrance Loss Coefficient for Honeycomb Annular Gas Seals
,”
ASME J. Tribol.
,
122
(
3
), pp.
622
627
.
5.
He
,
L.
,
Yuan
,
X.
,
Jin
,
Y.
, and
Zhu
,
Z.
,
2001
, “
Experimental Investigation of the Sealing Performance of Honeycomb Seals
,”
Chin. J. Aeronaut.
,
14
(
1
), pp.
13
17
.
6.
Childs
,
D. W.
, and
D'Souza
,
R. J.
,
2002
, “
A Comparison of Rotordynamic-Coefficient Predictions for Annular Honeycomb Gas Seals Using Three Different Friction-Factor Models
,”
ASME J. Tribol.
,
124
(
3
), pp.
524
529
.
7.
Childs
,
D. W.
, and
Ha
,
T. W.
,
1994
, “
Annular Honeycomb-Stator Turbulent Gas Seal Analysis Using New Friction-Factor Model Based on Flat Plate Tests
,”
ASME J. Tribol.
,
116
(
2
), pp.
352
360
.
8.
Kleynhans
,
G. F.
,
1996
, “
A Two-Control-Volume Bulk-Flow Rotordynamic Analysis for Smooth-Rotor/Honeycomb-Stator Gas Annular Seals
,” Ph.D. thesis, Texas A&M University, College Station, TX.
9.
Chochua
,
G.
,
Shyy
,
W.
, and
Moore
,
J.
,
2002
, “
Computational Modeling for Honeycomb-Stator Gas Annular Seal
,”
Int. J. Heat Mass Transfer
,
45
(
9
), pp.
1849
1863
.
10.
Childs
,
D. W.
, and
Wade
,
J.
,
2004
, “
Rotordynamic-Coefficient and Leakage Characteristics for Hole-Pattern-Stator Annular Gas Seals—Measurements Versus Predictions
,”
ASME J. Tribol.
,
126
(
2
), pp.
326
333
.
11.
Childs
,
D. W.
,
Smalley
,
A. J.
,
Camatti
,
M.
,
Hollingsworth
,
J. R.
,
Vannini
,
G.
, and
Carter
,
J. J.
,
2006
, “
Dynamic Characteristics of the Diverging Taper Honeycomb-Stator Seal
,”
ASME J. Turbomach.
,
128
(
4
), pp.
717
724
.
12.
Childs
,
D. W.
, and
Sprowl
,
T. B.
,
2007
, “
A Study of the Effects of Inlet Preswirl on the Dynamic Coefficients of a Straight-Bore Honeycomb Gas Damper Seal
,”
ASME J. Eng. Gas Turbines Power
,
129
(
1
), pp.
220
229
.
13.
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
.
14.
Keith
,
G. M.
,
Ha
,
T. W.
,
Bhattacharjee
,
P.
,
Childs
,
D. W.
,
Nielsen
,
K. K.
, and
Platt
,
J. P.
,
2009
, “
Friction Factor Jump in Honeycomb Seals Explained by Flow-Acoustic Interactions
,”
ASME
Paper No. GT2009-60337.
15.
Massini
,
D.
,
Facchini
,
B.
,
Micio
,
M.
,
Bianchini
,
C.
,
Ceccherini
,
A.
, and
Innocenti
,
L.
,
2014
, “
Analysis of Flat Plate Honeycomb Seals Aerodynamic Losses: Effects of Clearance
,”
Energy Procedia
,
45
, pp.
502
511
.
16.
Bianchini
,
C.
,
Micio
,
M.
,
Maiuolo
,
F.
, and
Facchini
,
B.
,
2013
, “
Numerical Investigation to Support the Design of a Flat Plate Honeycomb Seal Test Rig
,”
ASME
Paper No. GT2013-95612.
17.
ASME, 1985, “Measurement Uncertainty,”
Instrument and Apparatus
(Performance Test Code, Vol. ANSI/ASME PTC 19.1-1985), American Society of Mechanical Engineers, New York.
18.
Kline
,
S. J.
, and
McClintock
,
F. A.
,
1953
, “
Describing Uncertainties in Single Sample Experiments
,”
Mech. Eng.
,
75
(
1
), pp.
3
8
.
19.
Childs
,
D. W.
, and
Ha
,
T. W.
,
1992
, “
Friction Factor Data for Flat-Plate Tests of Smooth and Honeycomb Surfaces
,”
ASME J. Tribol.
,
114
(
4
), pp.
722
730
.
20.
Nakiboglu
,
G.
,
2012
, “
Aeroacoustics of Corrugated Pipes
,” Ph.D. thesis, Eindhoven University of Technology, Eindhoven, The Netherlands.
21.
Temkin
,
S.
,
2001
,
Elements of Acoustics
,
Wiley
,
New York
.
22.
Gloerfelt
,
X.
,
2009
,
Cavity Noise
(VKI Lectures: Aerodynamic Noise From Wall-Bounded Flows), von Karman Institute, Rhode-St-Genese, Belgium.
23.
Khanal
,
B.
,
Knowles
,
K.
, and
Saddington
,
A. J.
,
2011
, “
Computational Study of Flowfield Characteristics in Cavities With Stores
,”
Aeronaut. J.
,
1173
(
115
), pp.
669
681
.
24.
Hassan
,
M. E.
,
Labraga
,
L.
, and
Keirsbulck
,
L.
,
2007
, “
Aero-Acoustic Oscillations Inside Large Deep Cavities
,”
Australasian Fluid Mechanics Conference
,
Queensland
,
Australia
, Dec. 3–7, pp. 421–428.
25.
Rayleigh
,
J. W. S. B.
,
1896
,
The Theory of Sound
, Vol.
2
,
Macmillan
,
London
.
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