Masters Theses

Date of Award

12-2005

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Ahmed D. Vakili

Committee Members

Basil Antar, Louis Deken

Abstract

A numerical experiment has been conducted to study and evaluate the structural behavior of newly designed labyrinth seals. Structural analysis was performed to understand, evaluate and compare new seals with a baseline straight seal that is typical of commonly used seals in steam turbines. New configurations of labyrinth seal knives were developed for use in steam turbines [17]. The main objective of this study is to develop a better understanding of selected various labyrinth seals that may be configured to minimize the steam leakage and reduce seal interactions with the shaft. Computational fluid dynamic modeling of the various configurations, from a related study, and preliminary structural analysis led new designs to incorporate curvature into knife geometries including a sharp flat free-edge. Two-dimensional linear elastic static structural analysis was performed on a baseline straight labyrinth seal knife and seven different new configurations incorporating flexible geometries like curved seals, using finite element analysis software ANSYS®. Structural behavior of all new seals was evaluated in comparison with the results obtained for the baseline straight seal knife. Results show that the new geometries are more flexible than the straight seal knife, within the elastic limit of the same material. Of the seven geometries of new curved knives, two (C4 and C5) had higher load bearing capacity than all the others and one of them exceeded the load bearing capacity of the straight knife. The two high performing configurations, CS1 and CS2, have very thin knives compared to the other configurations. These two were found to be the most flexible among all the seven new configurations, considered. The maximum deformation and load bearing capacity of all the seven knives were correlated against a single non-dimensional geometrical parameter that appears to govern such variations and, therefore, define the improved designs.

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