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International Journal of Rotating Machinery
Volume 2006 (2006), Article ID 93621, 11 pages
http://dx.doi.org/10.1155/IJRM/2006/93621

Rotordynamics of Turbine Labyrinth Seals with Rotor Axial Shifting

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA

Received 18 September 2005; Accepted 29 December 2005

Copyright © 2006 Jinxiang Xi and David L. Rhode. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Rotors in high-performance steam turbines experience a significant axial shifting during starting and stopping processes due to thermal expansion, for example. This axial shifting could significantly alter the flow pattern and the flow-induced rotordynamic forces in labyrinth seals, which in turn, can considerably affect the rotor-seal system performance. This paper investigates the influence of the rotor axial shifting on leakage rate as well as rotordynamic forces in high-low labyrinth seals over a range of seal clearances and inlet swirl velocities. A well-established CFD-perturbation model was employed to predict the rotordynamic coefficients. A surprisingly large effect was detected for rotordynamic characteristics due to rotor shifting. It was also found that a less destabilizing effect arose from rotor axial shifting in the leakage flow direction, whereas a more destabilizing effect arose from shifting against the leakage flow direction. Further, a tentative explanation was proposed for the large sensitivities of dynamic forces to rotor axial shifting.