0
research-article

Influence of rotor suspension anisotropy on oil film instability

[+] Author and Article Information
Francesco Sorge

DIID, Polytechnic School, University of Palermo Viale delle Scienze, 90128 - Palermo, Italy
francesco.sorge@unipa.it

1Corresponding author.

ASME doi:10.1115/1.4038946 History: Received April 24, 2017; Revised December 15, 2017

Abstract

A crucial problem of turbomachinery is the oil film instability on increasing the angular speed, which is correlated with the asymmetry of the bearing stiffness matrix and resembles the hysteretic instability somehow. As a beneficial effect is exerted on the latter by the anisotropy of the support stiffness, some favorable effects have been recently found by the author also for the former, whence a systematic analysis has been undertaken. The instability thresholds may be detected by the usual conventional methods, but a detailed analysis may be carried out by closed-form procedures in the hypothesis of symmetry of the rotor-shaft-support system, which condition approaches the real working of turbomachines quite often. Altogether, the results point out an improvement of the rotor stability for low Sommerfeld numbers by softening and locking the support stiffness in the vertical and horizontal directions respectively. Nonetheless, the partial support release on one plane implies lower instability thresholds for large Sommerfeld numbers, but this drawback may be obviated by a sort of "two-mode" stiffness management, with some vertical flexibility for heavy loads and full blocking for light loads. Otherwise, it is possible to combine the anisotropic supports with journal bearing types that offer favorable stability behavior in the range of large Sommerfeld numbers. Basing on approximate but realistic models, the present analysis elucidates the changes of the rotor-shaft unstable trend on varying the external stiffness of the supports and gives tools for a rapid calculation of the expected instability thresholds.

Copyright (c) 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

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