Satisfactory means for evaluating the vibration behavior of gas turbine installations where it is impractical to obtain a satisfactory model of the support structure and where it has natural frequencies in the operating range are not yet available. This paper investigates the feasibility of identifying the modal parameters of a flexibly supported rigid casing to predict the unbalance response of the contained rotor. Assumed known are the location of the principal axes of inertia of the casing. Numerical experiments demonstrate that the identification procedure works well even with a measurement accuracy of only two significant digits. Thus, the procedure is expected to be practically feasible, though no sensitivity studies have yet been carried out to determine the limitations imposed by the assumed location of the principal axes.

Issue Section:
Gas Turbines: Structures and Dynamics
Keywords:
vibrations, modal analysis, parameter estimation, gas turbines, rotors, bending, numerical analysis
Topics:
Degrees of freedom, Gas turbines, Rotors, Vibration, Mode shapes, Inertia (Mechanics), Errors
1.
Cottin
,
N.
,
Felgenhauer
,
H. P.
, and
Natke
,
H. G.
,
1984
, “
On the Parameter Identification of Elastomechanical Systems Using Input and Output Residuals
,”
Arch. Appl. Mech.
,
54
(
5
), pp.
378
–
387
.
2.
Leuridan, J. M., Brown, D. L., and Allenmang, R. J., 1983, “Direct System Parameter Identification of Mechanical Structures With Application to Modal Analysis,” 8th International Seminar on Modal Analysis, Katholieke Universiteit Leuven, Leuven, pp. 201–208.
3.
Lees, A. W., 1988, “The Least Square Method Applied to Identify Rotor/Foundation Parameters,” Proc. Intl Conference on Vibrations in Rotating Machinery, IMechE, Edinburgh, IMechE, London, pp. 209–215.
4.
Cheli, F., Dedini, F. G., and Vania, A., 1992, “Supporting Structure Effect on Rotating Machinery Vibration,” Proc. Intl Conference on Vibrations in Rotating Machinery, IMechE, Bath, IMechE, London, pp. 543–548.
5.
Feng
,
N. S.
, and
Hahn
,
E. J.
,
1995
, “
Including Foundation Effects on the Vibration Behavior of Rotating Machinery
,”
Mech. Syst. Signal Process.
,
9
(
3
), pp.
243
–
256
.
6.
Feng, N. S., and Hahn, E. J., 1996, “Experimental Identification of the Foundation Dynamic Stiffness Parameters of Rotor-Bearing-Foundation Systems,” Proceedings of the 6th International Symposium on Transport Phenomenon and Dynamics of Rotating Machinery, Honolulu, Pacific Center of Thermal-Fluids Engineering, Honolulu, HI, 1, pp. 48–57.
7.
Feng, N. S., and Hahn, E. J., 1996, “Turbomachinery Foundation Identification Using Foundation Modal Parameters,” Proceedings ISMA-21 Noise and Vibration Engineering Conference, III, Katholieke Universiteit Leuven, Leuven, pp. 1503–1513.
8.
IMSL, 1995, STAT/LIBRARY, IMSL Inc., Version 3.0.
9.
Meriam, J. L., 1975, Dynamics, SI Version, 2nd Ed., John Wiley and Sons, New York.
Copyright © 2003
 by ASME
You do not currently have access to this content.