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Space Saving Stress Relieving Feature for Finger Seals

IP.com Disclosure Number: IPCOM000210387D
Publication Date: 2011-Sep-01
Document File: 7 page(s) / 272K

Publishing Venue

The IP.com Prior Art Database

Related People

Nathan Gibson: INVENTOR [+2]

Abstract

Finger seals are used to seal fluid leak paths or to control fluid flow between two disparate pressure regions around a rotating shaft, primarily in gas turbine engines. The seals have long and thin “fingers” inclined in the direction of rotation of the shaft. The gaps between the “fingers” allow them to flex in such a way that the fingers of one layer block the fingers of the other layer, thus stopping movement of fluids between two regions. This flexing induces stress, especially at the root of the fingers, and hence reduces the life of the seal. A keyhole feature is usually provided at the root of the fingers to relieve stress; however, the feature is of limited use when inter-finger space is limited. To overcome this limitation, the authors of this paper propose a stress-relieving feature, which occupies less space than the keyhole feature.

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Space Saving Stress Relieving Feature for Finger Seals

Nathan Gibson

111 S 34th St., M.S. 503-120, Phoenix, Arizona, 85034, United States

and

Dan Meserve

1300 W Warner Rd., Tempe, Arizona, 85284, United States

ABSTRACT

Finger seals are used to seal fluid leak paths or to control fluid flow between two disparate pressure regions around a rotating shaft, primarily in gas turbine engines. The seals have long and thin "fingers" inclined in the direction of rotation of the shaft. The gaps between the "fingers" allow them to flex in such a way that the fingers of one layer block the fingers of the other layer, thus stopping movement of fluids between two regions. This flexing induces stress, especially at the root of the fingers, and hence reduces the life of the seal. A keyhole feature is usually provided at the root of the fingers to relieve stress; however, the feature is of limited use when inter-finger space is limited. To overcome this limitation, the authors of this paper propose a stress-relieving feature, which occupies less space than the keyhole feature.

1. Introduction

Finger seals are an advanced seal design that make use of multiple metal laminates that have long thin 'fingers' extending from the portion of the seal attached to one feature (the mount feature) towards another feature (the contact feature). An example of a typical seal installation is shown in


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Figure 1.

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Figure 1: Example of Installed Finger Seal

Source: US Patent 6,196,550, Issued to Honeywell International

Mount

Feature

Laminates

Finger

Seal

Contact

Feature


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The long, flexible shape of the fingers enables them to flex and bend to maintain sealing with the contact feature when there is relative motion between the two features. The highest, and therefore the limiting, stress in a finger seal occurs at the root of the finger nearest to the mount feature. A picture of a laminate showing the long flexible fingers and the root of the finger that is a stress riser is shown in Figure
2.

Finger root,

stress riser

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Flexible fingers

Figure 2: Laminate of Finger Seal

Source: US Patent 6,196,550, Issued to Honeywell International

Repeated flexing of the finger can cause fatigue or yielding at the location of this stress riser. It is possible that, in some applications, the fatigue at this point will become the limiting factor on seal life. It is desirable to modify the finger profile such that the stress at the root of the finger is lower.

Previous finger seals have made use of a keyhole shaped base that creates a more gradual curve at the root of the finger to reduce stress. This keyhole significantly reduces stress at the finger root. Arrangements to reduce stress are discussed in the following patents:

Patent US 20030025274 A1 on Laminated finger seal with stress reduction...