Seal for a joint or juncture – Process of dynamic sealing – Close proximity seal
Reexamination Certificate
1998-05-19
2001-01-16
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Process of dynamic sealing
Close proximity seal
C277S350000, C277S355000, C277S412000, C277S420000, C277S421000
Reexamination Certificate
active
06173958
ABSTRACT:
TECHNICAL FIELD
The present invention relates to seals for turbine applications and particularly relates to woven seals and hybrid cloth-brush seals for sealing between relatively moving parts in gas turbines.
BACKGROUND
Sealing is oftentimes essential when there are two relatively movable mechanical members in close proximity to one another. The members may have substantial relative motion, such as a turbine shaft against a lubricating oil reservoir, or a rotatable turbine stage relative to fixed support structure and having to withstand a pressure differential across the stage. Alternatively, there could be small vibratory pulsing motion between the members, along with thermal growth, as in sealing between a combustor and a transition piece. The resultant dynamic mismatch at typical combustor junctions requires an effective seal to contain the combustion products and a pressure differential and to allow for the dimensional growth.
More particularly, a plurality of combustors are conventionally disposed in an annular array about the axis of a turbine. Hot gases of combustion flow from each combustor through a transition piece into the first-stage nozzle. Because the transition pieces and the first-stage nozzle are formed of different materials and are subjected to different temperatures during operation, they experience different degrees of thermal growth. Thus, both the transition pieces and the first-stage nozzle support elements move radially, circumferentially and axially relative to one another as a result of thermal growth. Dynamic pulsing between these parts also occurs. This time variable mismatch at the junction of the transition pieces and the first-stage nozzle support elements requires an effective seal to contain the combustion products and the pressure differential across the space, while accommodating these dimensional changes. More particularly, the sealing devices have to conform to surfaces that have time varying characteristics, including whirl, wobble and surface undulations introduced due to wear, and must be capable of operating under high temperature conditions.
A substantial number of seals have been employed in turbine applications in the past. For example, labyrinth seals are often employed between relatively rotating parts. Labyrinth seals, however, have limitations in that they do not easily conform to vibratory movement or rotating surfaces, particularly if there are imperfections in the surfaces. Labyrinth seals hove not demonstrated usefulness in non-rotary applications. Brush seals have been used in many environments, including turbines. Brush seals generally conform better to surface non-uniformities and seal better than labyrinth seals. However, they are severely limited by handling and fabrication difficulties. For example, the very fine bristle wires are not bound together before assembly and it is a formidable task to lay out a predetermined layer of bristles to the required thickness to form a bristle pack suitable to form the resulting seal. The brush seals are, thus, very expensive.
DISCLOSURE OF THE INVENTION
According to an aspect of the present invention, there is provided a cloth seal comprised of a plurality of layers of woven material, such as metal, polymer or ceramic material, which are superposed over one another, bound together along an edge in a suitable frame and from which the layers project to seal with an adjacent part. Because of the flexible nature of the layered woven material, it can conform to the surfaces of the adjacent part and form an effective seal. For example, in a seal formed between a transition piece and a first-stage nozzle element, the layers of material may be disposed in a frame and suitably secured thereto, for example, by clamping the frame, welding the material to the frame, or the like. The layers of material would project from the frame to the transition piece. As well known, the transition piece moves in a pulsed fashion having both longitudinal and transverse movements. With the free edge of the layers engaging the transition piece, an effective seal is formed between these high and low-pressure areas. The woven material along its sealing edge may have free bristles projecting from the weave, i.e., the transversely extending bristles may be spaced back from the tips of the longitudinally extending bristles whereby the latter form free bristles along the sealing edge of the woven material.
In an alternate form hereof, there is provided a hybrid woven material in combination with brush seals. For example, layers of the woven material may be interspersed with discrete bristles or brushes whereby a combination brush and woven material seal is formed.
In a further alternative form of the present invention, there is provided a dual stiffness cloth brush seal for sealing between a combustion liner and transition piece. The seal comprises a pack of long, woven metal/polymer/ceramic cloth strips having stiff bristle fibers extending in one direction and a softer, more pliable plurality of fibers extending in the orthogonal direction. The stiff bristles may be bent at an angle, for example, on the order of 10 to 30°. In use, the cloth end, i.e., the more compliant longitudinal weave, may be wrapped around the outside of the combustion liner and a metal ribbon may overlie the seal, securing it to the liner. The bristles project outwardly at the desired angle for engagement at their ends with the inside surface of the transition piece, forming a seal.
In a further embodiment of the present invention, the seal hereof may be used for shaft sealing applications where high-pressure differentials have to be tolerated. For example, the woven seal may be clamped in a backing plate, with the bristles extending radially toward and into engagement with the rotatable shaft. By providing a curved surface on the downstream low-pressure side of the seal, the wear of the bristles on the shaft can be accommodated as they bear along the curved surface. That is, as the bristles wear, the bristles bend such that the tips continue to engage the curved surface of the shaft and continue to afford a sealing function. Thus, for high pressure differentials across a sealing interface, the bristles afford a superior sealing mechanism that does not lose its effectiveness with use, particularly when the seal material, i.e., the bristles, are worn.
In a still further embodiment of the present invention, there is provided a hybrid labyrinth-brush seal particularly for sealing between a shaft and a fixed member. As well known, shaft sealing using labyrinth seals alone results in leakage past the sealing fins. Excessive wear also occurs should the labyrinth seal fins contact one another. In accordance with the present invention, a brush seal or a woven cloth with bristles extending therefrom may be clamped in a slot between the labyrinth seals. Thus, with one of the labyrinth seals serving as a backing for the brush seal, the brushes engage the rotating shaft, affording improved sealing with the brush seal, higher structural integrity and added sealing with the labyrinth. Furthermore, this type of seal can be retrofitted into existing labyrinth seals.
These forms of woven material seals or hybrid woven material/brush seals may accommodate reasonable shape variations, while offering superior sealing. They can be formed of high-temperature resistant materials and offer substantial structural integrity by tying in the fibers or bristles into a weave, yet allowing for conformity to different surface movements and undulations that other types of seals, for example, labyrinth seals, would not be able to accommodate.
In a preferred embodiment according to the present invention, there is provided a seal comprising first and second relatively moving parts, a plurality of layers of a woven material substantially overlying one another with overlying marginal portions freely engaging the first part to form a seal therewith and means for securing the layers of woven material to the second part, with the woven material of the layers thereof projecting f
Bagepalli Bharat S.
Cromer Robert H.
Dinc Osman S.
Maynard James
Beres John L.
General Electric Co.
Knight Anthony
Nixon & Vanderhye
LandOfFree
Hybrid labyrinth and cloth-brush seals for turbine applications does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hybrid labyrinth and cloth-brush seals for turbine applications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hybrid labyrinth and cloth-brush seals for turbine applications will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2477353