0
Research Papers: Nuclear Power

Misalignment in Combi-Bearing: A Cause of Parametric Instability in Vertical Rotor Systems

[+] Author and Article Information
Jean-Claude Luneno

e-mail: jean-claude.luneno@ltu.se

Jan-Olov Aidanpää

e-mail: jan-olov.aidanpaa@ltu.se
Division of Mechanics of Solid Materials,
Luleå University of Technology,
SE 971 87 Luleå, Sweden

Rolf Gustavsson

Vattenfall Research and Development AB,
814 26 Älvkarleby, Sweden
e-mail: rolf.gustavsson@vattenfall.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received April 27, 2012; final manuscript received October 19, 2012; published online February 21, 2013. Assoc. Editor: Patrick S. Keogh.

J. Eng. Gas Turbines Power 135(3), 032501 (Feb 21, 2013) (8 pages) Paper No: GTP-12-1107; doi: 10.1115/1.4007882 History: Received April 27, 2012; Revised October 19, 2012

The dynamic characteristics of the combi-bearing (combined thrust-journal bearing) in vertical rotor systems were analytically modeled and experimentally verified in the authors’ previous publications. An angular misalignment, which may be caused by a possible manufacturing or assembling error, is introduced in the combi-bearing’s rotating collar. A new model of the defective combi-bearing has been derived. The derived model shows that the angular misalignment in the combi-bearing’s rotating collar generates an asymmetry in the rotor system at the combi-bearing’s location. The rotor system’s stiffness in its two translational X and Y directions differ at the combi-bearing’s location. Constant parameters and/or coefficients in rotating asymmetric structures appear to change with time when observed in the stationary frame. These time dependent parameters (coefficients) are the source of the so-called parametric instability in rotating systems. If the collar angular misalignment is located in the X-Z plane all rotor motions in this plane at the contact point between the combi-bearing and the rotor will be coupled. A parametric instability is observed within certain ranges of the rotor speed, depending on the magnitude of the angular misalignment.

FIGURES IN THIS ARTICLE
<>
Copyright © 2013 by ASME
Topics: Bearings , Rotors
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

(a) Schematic view (right) of a vertical hydropower unit together with a discretized rotor (left), and (b) the symmetry plane of a vertical rotor model with a misaligned collar

Grahic Jump Location
Fig. 2

(a) The X-Z symmetry plane of the combi-bearing, and (b) an upper view of the thrust bearing without misalignment

Grahic Jump Location
Fig. 3

(a) Translation in the X, Z directions and rotation about the Y-axis, (b) insertion of angular misalignments α and β in the X-Z plane, and (c) free body diagram

Grahic Jump Location
Fig. 4

Real part of the rotor system’s eigenvalues in the rotating frame. The blue color is for α=β=1 deg and the red color is for α=β=5 deg. (b), (c) The magnifications of the regions of interest in (a).

Grahic Jump Location
Fig. 5

Real part of the rotor system’s eigenvalues in the rotating frame. The blue color represents β=1 deg, α=-1 deg, and the red color represents β=5 deg, α=-5 deg. (b), (c) The magnifications of the regions of interest in (a).

Grahic Jump Location
Fig. 6

Imaginary part of the eigenvalues in the rotating frame

Grahic Jump Location
Fig. 7

Rotor time-response in the vertical Z direction at node 2: (a) α=β and N = 1355 rpm, (b) α=-β and N = 2600 rpm

Grahic Jump Location
Fig. 8

Rotor steady-state response at node 2: (a) α=β, and (b) (α=-β)

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In