This paper experimentally studies the leakage and rotordynamic performance of a long-smooth seal with air–oil mixtures. Tests are performed with inlet gas-volume-fraction gas volume fraction (GVF) = 0%, 2%, 4%, 6%, and 10%, rotor speed ω = 5, 7.5, 10, and 15 krpm, inlet temperature Ti = 39.4 °C, exit pressure Pe = 6.9 bars, and pressure drop (PD) = 31, 37.9, and 48.3 bars. Test results show that adding air into the oil flow does not change the seal's mass flow leakage m˙ discernibly but significantly impacts the seal's rotordynamic characteristics. For all PDs and speeds, K increases as inlet GVF increases from zero to 10% except for 6% ≤ inlet GVF ≤ 10% when PD = 48.3 bars, where K decreases as inlet GVF increases. The K increment will increase a pump rotor's natural frequency and critical speed. Increasing the rotor's natural frequency would also increase the onset speed of instability (OSI) and improve the stability of the rotor. Adding air into the oil flow has little impact on cross-coupled stiffness k, direct damping C, and effective damping Ceff. Ceff = C − k/ω + mqω, where mq is the cross-coupled virtual-mass. Test results are compared to predictions from San Andrés's (San Andrés, 2011, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503.) bulk-flow model, which assumes that the liquid–gas mixture is isothermal and homogenous. The model reasonably predicts m˙, C, and Ceff. All predicted K values are positive, while measured K values are negative for some test cases. Predicted k values are close to measurements when ω = 5 krpm and are larger than measurements when 7.5 ≤ ω ≤ 15 krpm.

References

References
1.
Childs
,
D.
,
1983
, “
Finite-Length Solutions for Rotordynamic Coefficients of Turbulent Annular Seals
,”
ASME J. Tribol.
,
105
(
3
), pp.
437
444
.
2.
Marquette
,
O. R.
,
Childs
,
D. W.
, and
San Andres
,
L.
,
1997
, “
Eccentricity Effects on the Rotordynamic Coefficients of Plain Annular Seals: Theory Versus Experiment
,”
ASME J. Tribol.
,
119
(
3
), pp.
443
447
.
3.
Iwatsubo
,
T.
, and
Nishino
,
T.
,
1994
, “
An Experimental Study on the Static and Dynamic Characteristics of Pump Annular Seals With Two Phase Flow
,”
Rotordynamic Instability Problems in High-Performance Turbomachinery
, NASA Glenn Research Center, Cleveland, OH, Report No.
94N34179
.https://ntrs.nasa.gov/search.jsp?R=19940029673
4.
Arghir
,
M.
,
Zerarka
,
A.
, and
Pineau
,
G.
,
2011
, “
Rotordynamic Analysis of Textured Annular Seals With Multiphase (Bubbly) Flow
,”
Incas Bull.
,
3
(
3
), pp.
3
13
.
5.
Kleynhans
,
G.
, and
Childs
,
D.
,
1997
, “
The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals
,”
ASME J. Eng. Gas Turbines Power
,
119
(
4
), pp.
949
956
.
6.
San Andrés
,
L.
,
2011
, “
Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals
,”
ASME J. Eng. Gas Turbines Power
,
134
(
2
), p.
022503
.
7.
San Andrés
,
L.
,
Lu
,
X.
, and
Liu
,
Q.
,
2015
, “
Measurements of Flowrate and Force Coefficients in a Short Length Annular Seal Supplied With a Liquid/Gas Mixture (Stationary Journal)
,”
Tribol. Trans.
,
59
(
4
), pp.
758
767
.
8.
San Andrés
,
L.
, and
Lu
,
X.
,
2017
, “
Leakage, Drag Power, and Rotordynamic Force Coefficients of an Air in Oil (Wet) Annular Seal
,”
ASME J. Eng. Gas Turbines Power
,
140
(
1
), p.
012505
.
9.
Zhang
,
M.
,
McLean
,
J.
, and
Childs
,
D.
,
2017
, “
Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal With Two-Phase, Mainly-Air Mixtures
,”
ASME J. Eng. Gas Turbines Power
,
139
(
12
), p.
122504
.
10.
Childs
,
D.
,
McLean
,
J.
,
Zhang
,
M.
, and
Arthur
,
S.
,
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
.
11.
Tao
,
L.
,
Diaz
,
S.
,
San Andrés
,
L.
, and
Rajagopal
,
K. R.
,
1999
, “
Analysis of Squeeze Film Dampers Operating With Bubbly Lubricants
,”
ASME J. Tribol.
,
122
(
1
), pp.
205
210
.
12.
Fourar
,
M.
, and
Bories
,
S.
,
1995
, “
Experimental Study of Air-Water Two-Phase Flow Through a Fracture (Narrow Channel)
,”
Int. J. Multiphase Flow
,
21
(
4
), pp.
621
637
.
13.
Cornish
,
R. J.
,
1933
, “
Flow of Water Through Fine Clearances With Relative Motion of the Boundaries
,”
Proc. R. Soc. London. Ser. A
,
140
(
840
), pp.
227
240
.
14.
Yamada
,
Y.
,
1962
, “
Resistance of a Flow Through an Annulus With an Inner Rotating Cylinder
,”
Bull. JSME
,
5
(
18
), pp.
302
310
.
15.
Patel
,
V. C.
, and
Head
,
M. R.
,
1969
, “
Some Observations on Skin Friction and Velocity Profiles in Fully Developed Pipe and Channel Flows
,”
J. Fluid Mech.
,
38
(
1
), pp.
181
201
.
You do not currently have access to this content.