Abstract

A simple nonlinear model to describe labyrinth seal flutter has been developed to assess the aeromechanic stability of straight-through labyrinth seals subjected to large gap variations. The model solves the one-dimensional integral mass, momentum, and energy equations of the seal for a prescribed motion numerically until a periodic state is reached. The model accounts for the effect, previously neglected, of high clearance variations on the stability. The results show that when the vibration amplitudes are small, the work-per-cycle coincides with the prediction of the Corral and Vega model (2018, “Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models. Part I: Theoretical Background,” ASME J. Turbomach., 140(10), p. 121006) and Corral et al. (2021, “Higher-Order Conceptual Model for Seal Flutter,” ASME J. Turbomach., 143(7), p. 071006), but for large vibration amplitudes nonlinearities alter the stability limit. In realistic cases, when the discharge time of the seal is much longer than the vibration period, the nonlinear effects are significant and tend to increase the unstable range of operating conditions. Furthermore, seals supported either on the high-pressure or low-pressure sides, stable for small vibration amplitudes, can destabilize when the vibration amplitude increases. The linear stability, though close in many situations to the nonlinear threshold, is not conservative, and attention must be paid to nonlinear effects.

References

1.
Hodkinson
,
B.
,
1939
, “
Estimation of the Leakage Through a Labyrinth Gland
,”
Proc. Inst. Mech. Eng.
,
141
(
1
), pp.
283
288
.
2.
Alford
,
J.
,
1964
, “
Protection of Labyrinth Seals From Flexural Vibration
,”
ASME J. Eng. Gas Turbines Power
,
86
(
2
), pp.
141
147
.
3.
Alford
,
J.
,
1967
, “
Protecting Turbomachinery From Unstable and Oscillatory Flows
,”
ASME J. Eng. Gas Turbines Power
,
89
(
4
), pp.
513
528
.
4.
Alford
,
J. S.
,
1971
, “
Labyrinth Seal Designs Have Benefitted From Development and Service Experience
,”
National Air Transportation Meeting
,
Atlanta, GA
,
May 10–13
,
In SAE Technical Paper, SAE International
.
5.
Lewis
,
D.
,
Platt
,
C.
, and
Smith
,
E.
,
1979
, “
Aeroelastic Instability in F100 Labyrinth Air Seals
,”
AIAA J. Aircr.
,
16
(
7
), pp.
484
490
.
6.
Ehrich
,
F.
,
1968
, “
Aeroelastic Instability in Labyrinth Seals
,”
ASME J. Eng. Gas Turbines Power
,
90
(
4
), pp.
369
374
.
7.
Abbot
,
D. R.
,
1981
, “
Advances in Labyrinth Seal Aeroelastic Instability Prediction and Prevention
,”
ASME J. Eng. Gas Turbines Power
,
103
(
2
), pp.
308
312
.
8.
Corral
,
R.
, and
Vega
,
A.
,
2018
, “
Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models. Part I: Theoretical Background
,”
ASME J. Turbomach.
,
140
(
10
), p.
121006
.
9.
Vega
,
A.
, and
Corral
,
R.
,
2018
, “
Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models. Part II: Physical Interpretation
,”
ASME J. Turbomach.
,
140
(
10
), p.
121007
.
10.
Corral
,
R.
,
Vega
,
A.
, and
Greco
,
M.
,
2020
, “
Conceptual Flutter Analysis of Stepped Seals
,”
ASME J. Eng. Gas Turbines Power
,
142
(
7
), p.
071001
.
11.
Corral
,
R.
,
Greco
,
M.
, and
Vega
,
A.
,
2019
, “
Tip-Shroud Labyrinth Seal Impact on the Flutter Stability of Turbine Rotor Blades
,”
ASME J. Turbomach.
,
141
(
10
), p.
101006
.
12.
Corral
,
R.
,
Greco
,
M.
, and
Vega
,
A.
,
2021
, “
Higher-Order Conceptual Model for Seal Flutter
,”
ASME J. Turbomach.
,
143
(
7
), p.
071006
.
13.
Corral
,
R.
,
Greco
,
M.
, and
Vega
,
A.
,
2022
, “
Effective Clearance and Differential Gapping Impact on Seal Flutter Modelling and Validation
,”
ASME J. Turbomach.
,
144
(
7
), p.
071010
.
14.
Greco
,
M.
, and
Corral
,
R.
,
2021
, “
Numerical Validation of an Analytical Seal Flutter Model
,”
J. Global Power Propul. Soc.
,
5
, pp.
191
201
.
You do not currently have access to this content.