The flow through labyrinth seals of turbomachinery generates forces which can cause self-excited vibrations of the rotor above the stability limit. The stability limit is reached at a specific rotating speed or power. The continuous growth of power density and rotating speed necessitates an exact prediction of the stability limit of turbomachinery. Usually the seal forces are described with dynamic coefficients. A new, easy-to-handle identification procedure uses the stability behavior of a flexible rotor to determine the dynamic coefficients. Systematic measurements with a great number of labyrinth seal geometries lead to reasonable results and demonstrate the accuracy and sensitivity of the procedure. A comparison of the various methods used to minimize the excitation indicates which seal is more stable and will thus improve the dynamic behavior of the rotor.

Issue Section:
Gas Turbines: Structures and Dynamics
Keywords:
stability, seals (stoppers), gas turbines, rotors, vibration control, machine bearings, damping
Topics:
Brakes, Damping, Rotors, Stability, Stiffness, Excitation, Whirls, Flow (Dynamics), Honeycomb structures, Bearings, Vibration
1.
Childs, D. W., 1993, Turbomachinery Rotordynamics, John Wiley and Sons, New York.
2.
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, May 6–8.
3.
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
.
4.
Hawkins
,
L.
,
Childs
,
D.
, and
Hale
,
K.
,
1989
, “
Experimental Results for Labyrinth Gas Seals With Honeycomb Stators: Comparison to Smooth-Stator Seals and Theoretical Predictions
,”
ASME J. Tribol.
,
111
, pp.
161
–
168
.
5.
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, May 6–8.
6.
Wright, D. V., 1983, “Labyrinth Seal Forces on a Whirling Rotor,” ASME Applied Mechanics Division, Proceedings of the Symposium on Rotor Dynamical Instability, Vol. 55, M. L. Adams, Jr., ed., ASME, New York, pp. 19–31.
7.
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, pp. 179–207.
8.
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, Kaanapali, HI, pp. 55–72.
9.
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, G. Schweitzer, ed., Springer-Verlag, Berlin, pp. 289–299.
10.
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, Mar. 1–3, Erlangen-Nu¨rnberg, Germany, VDI-Report 1186, pp. 297–309.
11.
Ulbrich, H., 1988, “New Test Techniques Using Magnetic Bearings,” Magnetic Bearings Proceedings of the First International Symposium, ETH Zu¨rich, G. Schweitzer, ed., Springer-Verlag, Berlin, pp. 281–288.
12.
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, DE-Vol. 84-2, ASME, New York, pp. 1277–1282.
13.
Leie, B., and Thomas, H.-J., 1980, “Self-Excited Rotor Whirl Due to Tip-Seal Leakage Forces,” NASA Conference Publication 2133, proceedings of a workshop held at Texas A&M University, pp. 303–316.
14.
Benckert, H., and Wachter, J., 1980, “Flow Induced Spring Coefficients of Labyrinth Seals for Application in Rotordynamics,” NASA Conference Publication 2133, proceedings of a workshop held at Texas A&M University, pp. 1–17.
15.
Childs
,
D.
, and
Ramsey
,
C.
,
1991
, “
Seal-Rotordynamic-Coefficient Test Results for a Model SSME ATD-HPFTP Turbine Interstage Seal With and Without a Swirl Brake
,”
ASME J. Tribol.
,
113
, pp.
198
–
203
.
16.
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, May 6–8.
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 by ASME
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