Calculation of Rotor Dynamic Coefficients for Labyrinth SealsReport as inadecuate

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International Journal of Rotating Machinery - Volume 4 1998, Issue 4, Pages 257-269

Baker and Botts, Dallas, TX 75201-2980, USA

Mechanical, Aerospace, and Nuclear Engineering,Rotating Machinery and Controls Laboratory, University of Virginia, Charlottesville, VA 22903-2441, USA

Received 13 November 1997; Revised 29 January 1998

Copyright © 1998 Hindawi Publishing Corporation. 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.


A single control volume, Iwatsubo based bulk flow method for the calculation of these coefficients is developed and implemented. The method herein uses a unique iterativetechnique to first identify the mass flow rate based on pressure drops across the individualteeth, which is then used in the governing sets of continuity and momentum equations. Themethod is applicable to different teeth geometries and arrangements. A parametric analysisof the effect of mass flow rate on rotor dynamic coefficients is performed and suggests that asmall variation in mass flow rate does not significantly detract from the accuracy of thepredicted dynamic coefficients; the mass flow rate calculation implemented in this paper issufficiently accurate. Furthermore, the inclusion of some tangential momentum parametershas been previously proposed to improve the accuracy of the Iwatsubo method. However,from the current analysis the inclusion of such parameters is also shown to have little effecton the rotor dynamic coefficients and does not lead to improved correlation withexperimental data. Comparisons to experimental data suggest that the method herein isreasonable for use as a design tool to predict the trends and actual values of cross-coupledstiffness, the most important seal parameter in rotor dynamic analyses. The method is alsoshown to be useful in predicting the order of magnitude of principal stiffness and dampingcoefficients.

Author: B. P. Williams and R. D. Flack



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