The present invention relates to the field of combustion chambers, in particular in gas turbines. More particularly, the invention relates to cooling the walls of such combustion chambers between two shrouds.
The combustion chamber 51 mainly comprises an outer wall 51a and an inner wall 51b mechanically linked respectively with the outer portion 56a and the inner portion 56b of the combustion chamber casing 56. More precisely, the outer wall 51a of the combustion chamber is connected to the outer portion 56a of the combustion chamber casing 56 by means of a plurality of flexible connection tabs 61 fixed on the outer wall 51a of the combustion chamber 51 by fasteners 57 of the nut-and-bolt type. Similarly, the inner wall 51b of the combustion chamber is connected to the inner portion 56b of the combustion chamber casing via a plurality of flexible tabs 62 held on the inner wall of the combustion chamber by fasteners 58, and on the inner portion of the combustion chamber casing by fasteners 59.
As shown in
Typically, in an aeroengine gas turbine, the combustion chamber receives both fuel which is injected via one or more injection systems 55, and also compressed air which acts as an oxidizer. The fuel and the air are mixed together at the upstream end of the combustion chamber 54 in order to achieve combustion.
The air which is used for burning the fuel in the combustion chamber comes from a fraction of a stream of compressed air F delivered into a diffusion duct 71 by a compressor device (not shown). The remaining fraction of the compressed air stream forms a bypass stream 63, 64 which flows in the annular space 72 defined between the combustion chamber 51 and its casing 56. The bypass air stream serves to dilute the combustion gas by being reinjected into the combustion chamber, and also serves to cool the walls.
In order to withstand the high temperatures that exist inside the combustion chamber, its walls are made of a thermostructural composite material that withstands high temperatures better than a conventional metal structure. Nevertheless, even when made out of such a material, the walls of the combustion chamber still need to be cooled. For this purpose, the combustion chamber has a plurality of perforations 53 made through the inner and outer walls so that the bypass air stream 63 or 64 flowing in the annular space 72 penetrates into the combustion chamber. Consequently, the film of air flowing along the walls of the combustion chamber, and also the multiple streams penetrating via the perforations serve to reduce the temperature of the material constituting the combustion chamber in a significant manner.
Nevertheless, with the type of connection shown in
The present invention seeks to remedy the above-mentioned drawbacks and to provide a sealing ring which allows a cooling air stream to flow in the zone where the combustion chamber is connected to the casing.
These objects are achieved by a ring for fixing on the end of a combustion chamber, the ring being formed by a sleeve which is fixed around the end of a wall of the combustion chamber via a plurality of orifices for receiving fasteners, wherein the sleeve has at least one recess in its face facing the wall of the combustion chamber, thereby reducing the area of the sleeve that presses against the wall of the combustion chamber, and co-operating with said wall to form an open cavity in which a stream of cooling air can flow.
Thus, by means of the ring of the present invention, a stream of cooling air can flow to the end of the wall of the combustion chamber without any need to modify the system for connecting the combustion chamber to the casing. The wall of the combustion chamber can be provided with perforations all the way to its end. This increases the lifetime of the combustion chamber.
In a particular aspect of the invention, the ring includes an annular shoulder defining the end of the cavity formed between the ring and the wall of the combustion chamber.
Thus, the annular shoulder forms a spoiler and contributes to directing the stream of bypass air flowing in the cavity towards the wall of the combustion chamber.
In another aspect of the invention, the area of the sleeve pressing against the wall of the combustion chamber further includes contact portions formed around the orifices, said contact portions defining a plurality of recesses uniformly distributed over the face of the sleeve that faces the wall of the combustion chamber.
The ring then forms a plurality of cavities between itself and the wall of the combustion chamber, thus making it possible to calibrate more finely the flow rate of the cooling air stream.
According to a characteristic of the invention, the contact portions are of a thickness greater than the thickness of the annular shoulder so as to allow a fraction of the cooling air stream which flows in the cavity(ies) formed by the sealing ring to constitute a leakage flow. Thus, the outer shroud of the high pressure nozzle receives a portion of the cooling air stream, and the rate at which air enters into the combustion chamber can be controlled.
The ring of the invention may be made out of a thermostructural composite material or out of a metal alloy.
In a particular embodiment of the ring, it further comprises a flange extending the sleeve, the flange extending beyond the end of the combustion chamber.
The present invention also provides a combustion chamber including at least one ring as defined above, the ring being fixed to the end of one of the walls of the combustion chamber by fasteners.
Because of the structure of the ring of the present invention, the combustion chamber may have a plurality of perforations in the ring connection zone, these perforations being fed with a stream of cooling air which flows in the cavity(ies) formed between the sealing ring and the wall of the combustion chamber.
In a particular embodiment, the combustion chamber further comprises a gasket between the ring and the wall of the combustion chamber to obstruct any leakage outlet from the ring. The gasket may be held in the bottom of the open cavity or it may be placed at the end of the ring, in which case the gasket is held at the end of the ring by a piece of foil fixed with the ring on the combustion chamber.
The foil may comprise a single piece or a plurality of sectors held on the wall of the combustion chamber by the fasteners.
In another particular embodiment, each fastener includes a washer of thickness greater than that of the open cavity formed between the wall of the combustion chamber and the ring so as to allow a fraction of the cooling air stream flowing in the cavity(ies) formed beneath the ring to constitute a leakage flow.
In an embodiment of the combustion chamber, it has a step formed at the end of its wall so as to allow a fraction of the cooling air stream flowing in the cavity(ies) formed by the ring to constitute a leakage flow.
The leakage flow serves to cool the outer shroud of the high pressure nozzle, which can consequently be cooled by an additional film of cool air. In addition, the rate at which air enters into the combustion chamber can be controlled.
The present invention also provides a combustion chamber including first and second rings as described above, the first ring being fixed to the end of the outer wall of the combustion chamber and the second ring being fixed to the end of the inner wall of the combustion chamber.
Both walls of the combustion chamber are thus provided with respective rings of the invention such that the lifetime of the end of the combustion chamber is increased.
The walls of the combustion chamber may be made out of a thermostructural composite material, out of an optionally porous metal material, or indeed out of a metal-matrix composite material.
Other characteristics and advantages of the invention appear from the following description of particular embodiments of the invention, given by way of non-limiting example, and with reference to the accompanying drawings, in which:
The present invention is described with reference to a ring for providing sealing between a combustion chamber and a nozzle. Nevertheless, the person skilled in the art will have no difficulty in applying the invention to a ring for connecting flexible connection tabs to the combustion chamber as described in French patent applications FR 01/07361 and FR 01/07363 in the name of the present Applicant. In general, the present invention applies to any type of ring which covers a portion of a wall of a structure that needs to be cooled by a flowing air stream.
The sleeve 1a is extended by a collar 1b which extends outwards from the combustion chamber in such a manner as to cover the space between the end of the combustion chamber and the beginning of the high pressure nozzle 52 in order to make contact with a strip gasket 67 placed on the nozzle.
More particularly, the inside face of the sleeve 1a is machined over a large fraction in order to form a recess 3. The fraction of the inside surface of the sleeve which is not machined forms an annular shoulder 2. The sleeve 1a is thicker at its annular shoulder 2. In the zone for connecting the flexible tabs 61 to the wall 51a of the combustion chamber, as shown in
As shown in
In addition, when the combustion chamber is provided not only with the perforations 53 of the kind typically formed away from the connection zone, but also with additional perorations 70 beneath the ring, a continuous cooling film 10 can be maintained all the way to the end of the wall inside the combustion chamber. The annular shoulder 2 acts as a spoiler at the end of the cavity 6 serving to force the cooling air stream 63 into the perforations 70. Furthermore, by selecting an inclined angle for the bore direction of the additional perforations 70, holes that open out almost in the end of the combustion chamber wall can be fed with the cooling stream. The cooling film 10 then advantageously constitutes a cooling film for the inner shroud of the high pressure nozzle 52.
A second embodiment of the sealing ring of the present invention is described below with reference to
The recesses 103 are machined between the orifices 105 for passing the fasteners 157 so as to leave not only an annular shoulder 102, but also contact areas 104 around each orifice 105. This embodiment makes it possible to avoid using washers that are needed for positioning the ring in the first embodiment. Consequently, with this second embodiment of the sealing ring of the invention, the cooling air stream 63 can likewise flow within the cavities 106 to the end of the combustion chamber and can feed the perforations 70 made in the connection zone, while also simplifying the technology for mounting the ring.
In an embodiment of the invention, a gasket is used to obstruct leaks that exist between the ring and the wall of the combustion chamber at the outlets from the cavities, which leaks are due to manufacturing tolerances for the parts and/or to fitting the ring on the combustion chamber. For this purpose, and as shown in
In a variant, sealing between the ring and the wall of the combustion chamber may be provided downstream from the shoulder, i.e. outside the cavity. In this case, and as shown in
In another embodiment of a combustion chamber having a sealing ring of the present invention, a portion of the cooling air stream which flows in the cavity(ies) formed by the sealing ring is allowed to leak out. Thus, as shown in
In a particular embodiment of the combustion chamber as shown in
Assemblies including a leakage flow exiting the sealing ring as shown in
Furthermore, whichever embodiment is being used to provide a leakage flow exiting the sealing ring, the spoiler that is formed by the shoulder serves not only to force the cooling air stream to flow into the perforations, but also to co-operate with the wall to calibrate the leakage flow so as to create a cooling film for the outer shroud of the high pressure nozzle. Such calibration enables the rate at which air flows into the combustion chamber to be controlled.
The sealing ring of the present invention can be made out of a thermostructural composite material such as carbon and silicon carbide (C/SiC) or silicon carbide and silicon carbide (SiC/SiC), or it can be made out of a metal alloy. The walls of the combustion chamber can also be made out of a thermostructural composite material such as C/SiC or SiC/SiC, or else out of an optionally porous metal material, or indeed out of a metal matrix composite material.
The cavity(ies) of the ring of the present invention enable cooling to be maximized by multiple perforations in the walls of the combustion chamber underlying the ring. Computations performed on a combustion chamber fitted with the sealing ring of the invention have shown that temperature can be reduced by about 400° C. in the connection zone.
As a consequence, the lifetime of the end of the combustion chamber is increased and a cooling film can be generated for the inner shroud of the high pressure nozzle, and possibly also for the outer shroud. The present invention thus provides a solution for cooling the walls of the combustion chamber which allows the combustion chamber to be connected directly to the casing via its walls while nevertheless providing sealing between the combustion gas stream and the bypass stream which is used to provide a stream of cooling air.
Number | Date | Country | Kind |
---|---|---|---|
02 07291 | Jun 2002 | FR | national |
Number | Name | Date | Kind |
---|---|---|---|
4458481 | Ernst | Jul 1984 | A |
4944151 | Hovnanian | Jul 1990 | A |
5470198 | Harrogate et al. | Nov 1995 | A |
5701733 | Lewis et al. | Dec 1997 | A |
6131384 | Ebel | Oct 2000 | A |
6644034 | Ariyoshi et al. | Nov 2003 | B2 |
6647729 | Calvez et al. | Nov 2003 | B2 |
6668559 | Calvez et al. | Dec 2003 | B2 |
6675585 | Calvez et al. | Jan 2004 | B2 |
6679062 | Conete et al. | Jan 2004 | B2 |
6708495 | Calvez et al. | Mar 2004 | B2 |
6732532 | Camy et al. | May 2004 | B2 |
6775985 | Mitchell et al. | Aug 2004 | B2 |
20020184888 | Calvez et al. | Dec 2002 | A1 |
20020184892 | Calvez et al. | Dec 2002 | A1 |
20030000223 | Conete et al. | Jan 2003 | A1 |
20040118127 | Mitchell et al. | Jun 2004 | A1 |
Number | Date | Country |
---|---|---|
2 785 664 | May 2000 | FR |
2 102 897 | Feb 1983 | GB |
Number | Date | Country | |
---|---|---|---|
20040032089 A1 | Feb 2004 | US |