Rotor-fluid interactions can cause self-excited shaft vibrations of high density turbomachinery. Often the amplitude of the vibrations reaches unacceptably high amplitudes and the scheduled power or running speed cannot be achieved. One of the most important sources of excitation is the flow through labyrinth seals. For a reliable design it is necessary to predict these forces exactly, including not only stiffness but also damping coefficients. As the forces in labyrinth gas seals are rather small only minimal experimental data is available for the comparison and validation of calculations. Meanwhile a new and easy-to-handle identification procedure enables the investigation of numerous seal geometrys. The paper presents dynamic coefficients obtained with a stepped labyrinth and the comparison with other seal concepts. [S0742-4795(00)00903-0]

Issue Section:
Gas Turbines: Structures and Dynamics
Keywords:
gas turbines, vibration control, seals (stoppers), damping, stability
Topics:
Damping, Excitation, Flow (Dynamics), Pressure, Rotors, Stability, Stiffness, Vibration, Whirls, Magnetic bearings, Fluids, Stators
1.
Thomas
,
H.-J.
,
1958
, “
Instabile Eigenschwingungen von Turbinenla¨ufern, angefacht durch die Spaltstro¨mungen in den Stopfbuchsen und Beschaufelungen
,”
Bull. de AIM
71
, pp.
1039
–
1063
.
2.
Alford
,
J. S.
,
1965
, “
Protecting Turbomachinery From Self-Excited Rotor Whirl
,”
ASME J. Eng. Gas Turbines Power
,
87
, pp.
333
–
344
.
3.
Childs, D. W., 1993, Turbomachinery Rotordynamics, Wiley, New York.
4.
Wagner, N. G., and Steff, K., 1996, “Dynamic Labyrinth Coefficients From a High-Pressure Full-Scale Test Rig Using Magnetic Bearings,” NASA Conference Publication to be published, proceedings of a workshop held at Texas A&M University, College Station, TX, May 6–8, 1996.
5.
Childs
,
D. W.
,
Nelson
,
C. E.
,
Nicks
,
C.
,
Scharrer
,
J.
,
Elrod
,
D.
, and
Hale
,
K.
,
1986
, “
Theory Versus Experiment for the Rotordynamic Coefficients of Annular Gas Seals: Part 1–Test Facility and Apparatus
,”
ASME J. Tribol.
,
108
, pp.
426
–
432
.
6.
Hawkins
,
L.
,
Childs
,
D.
, and
Hale
,
K.
,
1989
, “
Experimental Results for Labyrinth Gas Seals with Honeycomb Stators: Comparison to Smooth-Stator Seals an Theoretical Predictions
,”
ASME J. Tribol.
,
111
, pp.
161
–
168
.
7.
Yu, Z., and Childs, D., 1996, “A Comparison of Rotordynamic Coefficients and Leakage Characteristics for Hole-Pattern Gas Damper Seals and Honeycomb Seal,” NASA Conference Publication to be published, proceedings of a workshop held at Texas A&M University, College Station, TX, May 6–8, 1996.
8.
Wright, D. V., 1983, “Labyrinth Seal Forces on a Whirling Rotor, ASME Applied Mechanics Division,” Proceedings of a Symposium on Rotor Dynamical Instability, Vol. 55, Adams, M. L., Jr., ed., ASME, New York, pp. 19–31.
9.
Millsaps, K. T., and Martinez-Sanches, M., 1993, “Rotordynamic Forces in Labyrinth Seals: Theory and Experiment,” NASA Conference Publication 3239, proceedings of a workshop held at Texas A&M University, College Station, TX, pp. 179–207.
10.
Matros, M., Neumer, T., and Nordmann, R., 1994, “Identification of Rotordynamic Coefficients of Centrifugal Pump Components Using Magnetic Bearings,” Preprints of the Fifth International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC-5), May 8–11, 1994, Kaanapali, Hawaii, USA, pp. 55–72.
11.
Wagner, N. G., and Pietruszka, W. D., 1988, “Identification of Rotordynamic Parameters on a Test Stand With Magnetic Bearings,” Magnetic Bearings Proceedings of the First International Symposium, ETH Zu¨rich, Schweitzer, G., ed., Springer Verlag, New York, pp. 289–299.
12.
Kwanka, K., and Mair, R., 1995, “Identification of Gas Seal Dynamic Coefficients Based on the Stability Behavior of a Rotor,” Proceedings of the 1st European Conference of Turbomachinery—Fluid Dynamic and Thermodynamic Aspects, March 1–3, Erlangen-Nu¨rnberg, Germany, VDI-Report 1186, pp. 297–309.
13.
Ulbrich, H., 1988, “New Test Techniques Using Magnetic Bearings,” Magnetic Bearings Proceedings of the First International Symposium, ETH Zu¨rich, Schweitzer, G., ed., Springer Verlag, New York, pp. 281–288.
14.
Kwanka, K., and Nagel, M., 1996, “Experimental Rotordynamic Coefficients of Short Labyrinth Gas Seals,” NASA Conference Publication to be published, proceedings of a workshop held at Texas A&M University, College Station, TX, May 6–8, 1996, pp. 135–144.
15.
Kwanka, K., 1997, “Rotordynamic Impact of Swirl Brakes on Labyrinth Seals with Smooth or Honeycomb Stators,” ASME Paper 97-GT-232.
16.
Kwanka, K., 1995, “Variation of Fluid Flow Forces in Seals With Rotor Bending,” DE-Vol. 84-2, 1995 Design Eng. Technical Conf., Vol. 3-Part B, ASME, New York, pp. 1277–1282.
17.
Kwanka, K., 1998, “Influence of Labyrinth Seal Geometry on Rotordynamic Coefficients,” Proceedings of the Fifth International Conference on Rotor Dynamics (IFToMM), Irretier, H., and Nordmann, R., ed., Vieweg Verlag, pp. 241–251.
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