Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Between blade edge and static part
Reexamination Certificate
2002-04-04
2004-01-27
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Bearing, seal, or liner between runner portion and static part
Between blade edge and static part
C415S139000, C415S191000, C277S377000
Reexamination Certificate
active
06682300
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on and hereby claims priority to United Kingdom Application No. GB0108398.9, filed Apr. 4, 2001, the contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The invention relates to a seal element for sealing a gap which may be formed between spaced-apart first and second components of a turbo machinery, in particular a combustion turbine. The invention also relates to a combustion turbine having a seal element.
BACKGROUND OF THE INVENTION
In industrial plants, particularly thermo-mechanical machines and chemical plants, in which different fluids are used, it may be necessary to keep those fluids separate from one another within the plants. For example, in thermal combustion power plants, flow regions of hot combustion gases have to be separated sealingly from flow regions of cooling gases of lower temperature. In gas turbine plants with high turbine inlet temperatures, for example of more than 1000.degree.C., thermal expansions of the individual components of the gas turbine plant occur, so that adjacent components are sometimes spaced from one another through the use of a gap in order to avoid high thermal stresses and the formation of cracks. Such gaps may constitute connections between flow regions of hot gases and flow regions of cold gases. It is advantageous to seal off the gap to reduce the inflow of cold gas into the flow region of hot gases so as not to thereby lower the temperature in the flow region of hot gases.
U.S. Pat. No. 3,341,172 and U.S. Pat. No. 2,991,045, each of which describes a gas turbine with an outer casing and a two-part inner casing, accordingly specify a sealing element that has a cross-section in the shape of an elongate C for sealing a gap between the two inner casings. An annular gap, through which cooling fluid is guided, is formed between the inner casing and the outer casing. The hot gas for driving the gas turbine flows within the inner casing.
U.S. Pat. No. 4,537,024 describes a gas turbine plant, in which components of a nozzle structure are sealed through the use of axial and radial sealing elements. The sealing elements are intended to prevent hot gas which flows through the nozzle structure from infiltrating into turbine regions outside the hot-gas duct. A sealing element can have approximately the shape of a squashed eight as seen in cross-section.
U.S. Pat. No. 5,975,844 describes in an assembly including two mutually thermally movable components each having a component groove located one opposite the other, a sealing element. This sealing element is directed along a main line for sealing a gap between the components. It comprises a first end, a second end opposite the first end and a middle region, in a cross-section substantially perpendicular to the main line, along a centre line, whereby the middle region is disposed between the ends and the sealing element having a toothed first surface.
U.S. Pat. No. 5,657,998 relates to a gas-path leakage seal for generally sealing a gas-path leakage-gap between spaced-apart first and second members of a gas turbine, in particular first and second segments of a gas turbine combustor casing. This seal comprises a generally imperforate foil-layer assemblage consisting essentially of materials selected from the group consisting of metals, ceramics, and polymers. This foil-layer is impervious to gas and it is disposed in the gas-part leakage-gap. The foil-layer assemblage having a first foil-layer with a lengthwise direction. The gas leakage seal further comprises a cloth-layer assemblage covering and contacting generally the entire first foil-assemblage outer surface and consisting essential of materials selected from the group consisting of metals, ceramics and polymers. Preferably the cloth-layer assemblage has two layers each have a thickness of about 10-25 microns. The cloth-layers each are woven cloth-layers and each comprises a high temperature, nickel-based super-alloy, such as Inconel X-750. The seal assemblage is either fixed in grooves of adjacent parts of a gas turbine, or introduced in a U-shape flange of a combustor, or used in a twin-seal installation or in a multi-seal installation. In either case the seal fully lies within the leakage-gap, and provides a sealing effect either by contacting a surface within the gap, being inserted in a groove or contacts another seal assemblage. In comparison to a conventional metal rigid seal this seal with two foil-assemblages reduces the gas-path leakage from 2.4% to generally 1.0% according to U.S. Pat No. 5,657,998.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a gas-path leakage seal element, in particular for a turbo machinery like a combustion turbine. It is a further object of the invention to provide a combustion turbine with a seal element. With the forgoing and other objects in view there is provided in accordance with the invention, a seal element for sealing a gas-path leakage-gap between spaced apart first and second components in particular of a turbo machinery. The first and second components having opposing inner and outer surfaces situated outside the leakage-gap. The seal element comprises a generally gas impervious sealing member and a layer comprising ceramic fibres, which layer at least partially covers the sealing element and defining a sealing surface for contacting outside the gap so that outer surfaces of set first and second components.
By virtue of the layer of ceramic fibres which form a flexible and deformable sealing portion a good sealing performance can be assured. The ceramic fibres can be used up to temperatures of about 1200 C. or even more. The seal element is therefore useable for sealing components of a turbo machinery, furnaces, burners or the like, which are exposed to hot gases. The sealing member improves the stiffness of the sealing element which ensures that the seal element does not break in parts and fall through the gap. Furthermore positioning the seal element outside the gap on the outer surfaces of the components has the advantage that the components itself do not have to be manufactured with grooves, recesses or the like and do not need to be thickened in the area of the gap for heat conducting purposes.
In accordance with another feature the layer comprises a ceramic fibre fabric, a ceramic fibre tape, a ceramic fibre sleeving or a ceramic fibre mat. The layer preferably itself is an object manufactured separately from the sealing member. It is put in contact with the sealing member for covering at least a portion of the sealing member after its own manufacturing. So it preferably provides a loose contact with the sealing member and is removable from the sealing member. In the latter case it could easily be replaced during maintenance of the turbo machinery by a new layer. In an embodiment in which the layer is provided as a sleeving the sealing member is introduced into the sleeving and so all surfaces of the sealing member is covered by the layer of ceramic fibres. It is also possible to provide a ceramic fibre layer tightly bounded to the sealing member.
In accordance with again another feature the sealing member essentially consists of a metal. Suitable metals are those who withstand high temperatures, for example high temperature steels like chromium steels or high temperature alloys on the basis of nickel or cobalt. The sealing member is preferable, flat and in particular is formed as sheet metal. It may comprise one or more flat members. The metal gives the sealing members on the one hand side a sufficient mechanical stiffness and on the other side sufficient elasticity so not to break in several portions when exposed to mechanical loads, e.g. pressure or force.
In accordance with a further feature said layer comprises ceramic fibres essentially consisting of a material like Zirconia (ZrO
2
), Silica (SiO
2
) or Alumina (Al
2
O
3
). It is understood that those ceramic materials could be combined and also be stabilised by other materials like Yttria (Y
2
O
3
). For example the
McAleenan J. M.
Siemens Aktiengesellschaft
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