Bibliographic Metadata

An analytical Pressure and flow model for leaf seals / by Gregor Franz Nicht
AuthorNicht, Gregor Franz
CensorWillinger, Reinhard
PublishedWien, 2018
DescriptionX, 71, iv Blätter : Illustrationen, Diagramme
Institutional NoteTechnische Universität Wien, Diplomarbeit, 2018
Zusammenfassung in deutscher Sprache
Document typeThesis (Diplom)
Keywords (DE)Lamellendichtung / Druckverteilung / Leckage
Keywords (EN)leaf seal / pressure distribution / leakage
URNurn:nbn:at:at-ubtuw:1-110955 Persistent Identifier (URN)
 The work is publicly available
An analytical Pressure and flow model for leaf seals [6.3 mb]
Abstract (German)

Lamellendichtungen sind eine fortschrittliche Dichtungsbauart für Turbomaschinen. Diese Dichtungen bestehen aus in Umfangsrichtung angeordneten Metallblättchen, welche in einem Gehäuse befestigt sind. Während des Betriebes soll die Dichtung berührungslos arbeiten damit weder Reibung noch Verschleiss auftritt. Die statische Druckverteilung an der Lamellenoberfläche hat darauf einen entscheidenden Einfluß. Die höhere Steifigkeit der Lamellen in axialer Richtung im Vergleich zu den Borsten von Bürstendichtungen ermöglicht den Einsatz bei größeren

Abstract (English)

Leafs seals are an advanced sealing technology to separate high and low pressure parts in turbomachinery, consisting of small metal sheet elements arranged in a housing around the shaft. During operation the seal should be non-contacting to minimize wear and friction. The static pressure on the surface of a single leaf appears to be the main parameter. The higher axial stiffness in comparison to brush seals allows greater differences in pressure and a hang-up effect can be averted. Assessing the discharge behavior of the sealing is important, because leakage is resulting in less efficient turbomachinery. In this thesis a new approach for an analytical calculation of the pressure distribution inside the seal is presented. It is based on a leakage flow model inside the side plate gaps. Furthermore the flow is assumed to be laminar and incompressible using simple pipe flow correlations with specified hydraulic diameters. The complete seal geometry is parameterized. The results in pressure distribution, leakage flow and static pressure on a single leaf (Lift Up, Blow Down) are compared with data published in literature. A good qualitative match was found, so in a second step, variations of the seal design were calculated. The influence of upstream and downstream side plate gap width ratios, heights of rotor side plate gap, numbers of leaves for constant rotor diameter and interleaf gap width gradients are investigated. For validation of the model, the results are compared as far as possible to published data. Also calculations are made for patented designs using leaves with non-rectangular cross-section to estimate, if further and more detailed research is reasonable. The static pressure distribution derived is used for a deflection calculation of the leaves using Euler-Bernoulli beam theory. The analytical model provides a simple approach for the investigation of leaf seals regarding pressure distribution and seal-leakage with qualitative good results.

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