Patent Application
20120122045
Priority is claimed to Swiss Application No. CH 01877/10, filed Nov. 9, 2010, the entire disclosure of which is hereby incorporated by reference herein.
The present invention relates to a seal arrangement for a silo combustor and to a silo combustor incorporating such a seal arrangement.
A silo-type combustor usually comprises a combustion chamber, which is supplied with a fuel from above and compressed air, and a hot gas casing through which the hot combustion products are supplied from the combustion chamber to a turbine. The hot gases expand through the turbine.
The compressed air is supplied to the combustion chamber through an annular channel, which surrounds the combustor casing. The flow of hot gases and the flow of compressed air are therefore in opposing directions. The compressed air has further the function of cooling the combustor chamber casing and the hot gas casing.
The lower part of the combustion chamber is called the combustor inner liner (CIL). The combustor inner liner and the hot gas casing have an overlap, where the tip of the combustor inner liner is located inside of the upper part of the hot gas casing. In order to avoid mechanical contact and resulting fretting a gap is provided between the combustor inner liner and the hot gas casing. As the compressed air is at a higher pressure than the hot gases flowing through the combustor inner liner and the hot gas casing, the pressure difference would cause leakage of compressed air from the annular channel into the hot gas flow, thus reducing the amount of air available for combustion. A seal is therefore provided in the gap to prevent any leakage.
The seal consists of a set of segments, which may or may not overlap. One seal design is called a belt seal. In this seal arrangement the segments are assembled circumferentially around the casing, whereby the individual segments are assembled with overlap and tightened by a spring. Their connection allows some movement relative to each other, and therefore they form a flexible structure, which accommodates the possible deformation of the combustor inner liner and the hot gas casing due to thermal expansion. Hooks welded onto the hot gas casing hold the belt seal segments. The interfaces between the seal segments are circumferentially located on the hot gas casing at the same positions as the hooks.
The belt seal structure accommodates a deformation of the combustor casing due to thermal expansion and a resulting variation in the radial gap between the combustor inner liner and the hot gas casing. The overlapping sections of the belt seal substantially prevent leakage past the seal in the axial direction. There are however still small gaps between the segments, which lead to leakages in the radial direction. The amount of leakage air is small and has no appreciable impact on the combustion air supply. These leakages can however, due to vortex formation, cause ingestion of hot gas into the gap between the combustor inner liner and the hot gas casing. This results in local overheating. This overheating may occur on the combustor inner liner as well as on the hot gas casing, in the same position where the holding hooks and the interface between the segments is located. These hot spots lead to increased oxidation and a reduced life of the combustor inner liner and of the hot gas casing.
An embodiment of the present invention provides a seal arrangement for a silo combustor. A first casing and a second casing each form a passageway for a gas, an end portion of the first casing being disposed radially inside an end portion of the second casing such that the first and the second casing form an overlapping region having a radial gap. A segmented seal has at least two adjacent segments disposed in the overlapping region so as to seal the radial gap, wherein the first casing includes at least one opening disposed in a region between the at least two adjacent segments.
The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:
a,3b,3c side views of a seal arrangement according to the invention, and
a,4b a cross section of a prior art seal arrangement.
An embodiment of the present invention provides an improved seal arrangement for a silo combustor to reduce the local overheating associated with the ingestion of hot gas into the overlapping region between the combustor inner liner and the hot gas casing.
According to an embodiment of the invention a seal arrangement for a silo combustor comprises a first casing forming a passageway for a gas and a second casing forming a passageway for a gas, whereby an end portion of the first casing is positioned radially inside of and overlapped by an end portion of the second casing, whereby a segmented seal is positioned to seal a radial gap between the casings in the overlapping portion. The first casing is provided with at least one opening in the region between two adjacent segments of the segmented seal.
Cool air, which leaks through a gap between adjacent segments of the segmented seal, will not cause a problem, if it can be directed appropriately without inducing ingestion of hot gas into the overlapping region of the first and second casing. An embodiment of the invention provides at least one opening in the first casing, air which leaks through a radial gap between two adjacent seal segments can flow radially through the opening in the first casing into the passageway for hot gases. As the leakage air flows directly into the hot gas path, vortex formation in the overlapping region of the first and second casing is minimized. Therefore local overheating of the first and second casings is prevented. Furthermore the provision of the opening allows the leakage air to flow into and mix with the axially flowing hot gas. This provides additional cooling of the casings.
According to one embodiment of the invention a silo combustor comprises a seal arrangement. The first casing is in this embodiment a combustor inner liner and the second casing is a hot gas casing.
In an embodiment, the at least one opening in the wall of the combustor inner liner in the region between two adjacent segments of the segmented seal enables compressed air, which leaks though gaps between the seal segments, to flow radially into the hot gas flow in the combustor.
The above and other embodiments, features and advantages of the invention will become more apparent from the following description of certain preferred embodiments thereof, when taken in conjunction with the accompanying drawings.
Referring to
The compressed air for combustion is supplied through an annular channel 4, which surrounds the combustor casing 5, and upper part of casing 6. The flow of hot gases 7 and the flow of compressed air 8 are therefore in opposing directions, as can be seen in
A first casing 5 of the combustor is called the combustor inner liner, which forms a lower part of the combustion chamber 3. A second casing 6 of the combustor is called a hot gas casing, which forms a passageway for supplying hot combustion gases to the turbine 2. The combustor inner liner 5 and the hot gas casing 6 have an overlap, where an end portion 19 of the combustor inner liner 5 is located inside of the upper part of the hot gas casing 6. A radial gap 9 is provided between the combustor inner liner 5 and the hot gas casing 6 in the overlapping region 10. This gap 9 is provided in order to avoid mechanical contact and resulting fretting between the combustor inner liner 5 and the hot gas casing 6. This mechanical contact would arise though deformation of the casings 5,6 due to thermal expansion.
The combustor inner liner 5 and the hot gas casing 6 are radially surrounded by the annular channel 4, which supplies compressed air to the combustor 12. As the compressed air in the channel 4 is at a higher pressure than the hot gases flowing through the combustor inner liner 5 and the hot gas casing 6, the pressure difference causes a leakage of compressed air into the hot gas flow 7, thus reducing the amount of air available for combustion. A segmented seal 11 is therefore provided in the radial gap 9 formed between the end portion of the combustor inner liner 5 and the end or upper portion of the hot gas casing 6 to minimize any leakage and to accommodate deformation of the casings 5, 6.
According to one embodiment of the invention a seal arrangement 1 for sealing this radial gap is shown schematically in
The seal arrangement 1 accommodates a deformation of the combustor casing 5, 6 due to thermal expansion and a resulting variation in the radial gap between the combustor inner liner 5 and the hot gas casing 6. The overlapping sections of the seal 11 substantially prevent leakage past the segmented seal 11 in the axial direction. There are however still small gaps at the interface 17 between adjacent segments 13, 14, which lead to leakages in the radial direction as depicted by arrow 16 in
In
Referring now to back to
The segmented seal 11 is made up of a plurality of segments which surround the combustor inner liner 5 in the circumferential direction, whereby at least one opening 20 in the combustor inner liner 5 is respectively provided in the region of, and preferably directly opposite, each interface 17 between adjacent seal segments. The at least one opening 20 may be in the form of a plurality of holes 21 extending radially through the combustor inner liner 5. The leaking compressed air would in this case be directed radially into the axially flowing hot gases 7, thereby increasing turbulence and mixing and thus cooling of the hot gases flowing through the combustor inner liner 5. The holes 21 may however have an axial and/or circumferential component, which would encourage film cooling of the combustor inner liner.
Alternatively the opening is in the form of a slot extending in the axial direction.
The holes 21 or slot should not extend further in the axial direction than the width of the segmented seal 11 in the axial direction.
The cross-sectional area of the at least one opening 20 is preferably designed such that the mass flow through the opening 20 is equal to the leakage flow rate through the interface 17 between two adjacent seal segments opposite the opening 20.
The invention is applicable to all seal arrangements whereby a conduit is made from two sections with an axially overlapping portion, whereby a seal is required to seal a radial gap between the two sections at the overlapping portion. Particularly, the description when referring to a combustor inner liner and hot gas casing is not limited thereto, but to a first and second casing accordingly forming a passageway.
The preceding description of the embodiments according to the present invention serves only an illustrative purpose and should not be considered to limit the scope of the invention. Particularly, in view of the preferred embodiments, different changes and modifications in the form and details can be made without departing from the scope of the invention. Accordingly the disclosure of the current invention should not be limiting. The disclosure of the current invention should instead serve to clarify the scope of the invention which is set forth in the following claims.
While the invention has been described with reference to particular embodiments thereof, it will be understood by those having ordinary skill the art that various changes may be made therein without departing from the scope and spirit of the invention. Further, the present invention is not limited to the embodiments described herein; reference should be had to the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01877/10 | Nov 2010 | CH | national |
