Patent Application
20130152603
The present invention relates to a combustion chamber for an aircraft engine in which an injection system is attached. The present invention also relates to a method for attaching an injection system in a combustion chamber of an aircraft engine and an aircraft engine comprising a combustion chamber according to the invention.
The combustion chambers in turbojet engines generally comprise an internal wall and an external wall, the upstream ends of which are connected via an annular base in such manner as to define a base of the combustion chamber. Injection systems, which are normally distributed about the periphery of the combustion chamber base, deliver a mixture of air and fuel that is ignited to supply combustion gases. Each combustion system comprises a venturi in which the air and the fuel are mixed. Each injection system also includes a bowl, located downstream of the venturi, the function of which is to explode the jet air/fuel mixture exiting the venturi. In addition, a baffle protects the chamber base from the flames in the combustion chamber.
A cylindrical retaining ring 17 is then placed around the two half-rings 13 so as to prevent the two half-rings 13 from separating from one another radially. Weld beads 18 join retaining ring 17 permanently to the two half-rings 13.
However, the applicant has discovered that with such an attachment system the nozzle of the fuel injector that is inserted in the injection system suffers significant wear and the service life thereof is shortened.
Documents EP1873454, EP1731839 and EP1873458 also describe combustion chambers in which the nozzle of the injector has a shortened service life and subject to substantial wear.
The object of the invention is to address the drawbacks of the prior art, at least in part, by suggesting a combustion chamber that is more resistant to wear and has a longer service life.
To do this, the invention suggests the use of an attachment system for the first and the second collars that prevent any movement of the injection system relative to the baffle. In fact, the applicant has discovered that vibrating action of the first and second collars if they are allowed to move between the two retaining lips of half-rings 13 amplifies the phenomenon of wear on the fuel injector and thereby shortens the service life of the combustion chamber.
More precisely, a first aspect of the invention relates to an aircraft engine combustion chamber including at least:
the combustion chamber further comprising:
Thus, in the combustion chamber according to the invention, the injection system is attached to the baffle by clamping means that prevent any axial movement of the second collar relative to the first collar, such that the injection system is unable to vibrate with respect to the chamber base. Consequently, the wear on the injector nozzle that is inserted in the injection system is reduced.
The combustion chamber according to the invention may also have one or more of the features listed in the following, either individually or in any technically possible combination thereof.
According to one embodiment, the clamping means comprise two jaws, one of the jaws bearing axially against the first collar, and the other jaw bearing axially against the second collar, the two jaws clamping the two collars axially between them, and the attachment means holding the two jaws clamped on either side of the two collars.
The two jaws advantageously extend circumferentially around the two collars.
According to a preferred embodiment, the clamping means comprise:
the attachment means holding together the retaining bushing and the retained bushing such that the retaining ring and the retained ring hold the first and second collars clamped against one another so that no relative axial movement is between the two is possible.
Thus, according to preferred embodiment, the retaining bushing is split into a plurality of bushing sections to enable it to be inserted downstream of the first collar. In fact, if the retaining bushing were constructed from a single part, it could not be mounted downstream of the first collar.
In this document, the terms “downstream” and “upstream” refer to the direction of the flow of combustion gases inside the cylindrical portion.
The retained peripheral skirt of the retained bushing, which is located upstream of the first and second collars, is constructed from a single part, and this enables the sections of the bushing that constitute the retaining bushing to be held together.
The retained peripheral skirt and the retaining peripheral skirt thus make it possible to limit the radial movements of the first and second collars.
The retained ring is positioned such that it bears axially against the second collar, and the retaining ring is positioned such that it bears axially against the first collar, so that the first and the second collars are clamped axially between these two rings. These two rings thus prevent all axial movement of the second collar relative to the first collar.
The portions of the bushing that constituent the retaining bushing are advantageously two half-bushings, such that the retaining bushing is divided into two half-bushings. Each element of the retaining bushing is also split into the same number of sections as the retaining bushing.
Consequently, when the retaining bushing is split into two sections, the retaining ring is also split into two sections, as is the retaining peripheral skirt.
The tubular portion is advantageously cylindrical.
Besides a lateral wall, the tubular portion advantageously has a shoulder that projects radially from said lateral wall, an annular channel that is defined between the first collar and the shoulder, the retaining ring being inserted inside the annular channel.
The lateral wall extends parallel to the reference axis.
The annular channel is advantageously delimited transversely by the first collar, with projects radially from the lateral wall, and by a shoulder of the lateral. The first collar thus forms the upstream wall of the annular channel, while the shoulder of the lateral wall forms the downstream wall of the annular channel. The retaining ring, which is inserted in the annular channel, bears axially against the first collar.
The attachment means advantageously include:
According to different embodiments:
According to different embodiments:
The retaining peripheral skirt advantageously has a height h1 that is lower than height h2 of the assembly formed by the first collar and the second collar. In this way, when the retaining bushing and the retained bushing are placed on either side of the two collars, they may be pressed flat against the two collars, yet the retaining peripheral skirt is not blocked by the retained ring.
More generally, the retaining bushing and the retained bushing are conformed so as to slot into one another, each one bearing axially against one of the collars.
A second aspect of the invention relates to an aircraft engine that comprises a combustion chamber according to the first aspect of the invention.
A third aspect of the invention relates to a method for attaching an injection system in a combustion chamber of an aircraft engine, wherein the combustion chamber includes a baffle comprising at least one tubular portion, the tubular portion extending in the direction of a reference axis, the tubular portion having a first upstream end surrounded by a first radially projecting collar, the injection system comprising at least one bowl that in turn comprises a cylindrical portion inserted into the tubular portion, the cylindrical portion comprising a second upstream end exiting the first upstream end of the tubular portion, the second upstream end of the cylindrical portion being surrounded by a second radially projecting collar, the second collar bearing axially against the first collar, and wherein the attachment method comprises the following steps:
Step (a) may be advantageously broken down as follows:
Each section of bushing advantageously comprises at least one attachment lug, wherein each attachment lug cooperates with the retaining peripheral skirt to define a peripheral channel into which the retained peripheral skirt is inserted.
Step (b) is advantageously a step of welding each attachment lug to the retained bushing.
Other features and advantages of the invention will become evident from reading the following detailed description in conjunction with the accompanying drawing, in which:
a are 7c are perspective views of the various steps of a method according to an embodiment of the invention;
For the sake of clarity, the same reference signs are used to identify identical or similar elements in all of the figures.
Internal and external chamber walls 24 and 26 connected by a chamber base 2 at the upstream ends thereof. A plurality of injection systems 1, typically fourteen to twenty-two, arranged at regular angular intervals (a single injection system is shown in
As may be seen in greater detail in
Baffle 4 comprises a plate 5 and a tubular portion 6. Tubular portion 6 has a rotational symmetry about a reference axis Y, and more precisely it has a cylindrical shape about reference axis Y. The function of plate 5 is to protect the base of chamber 2 from the flames in the combustion chamber. Tubular portion 6 is inserted in an orifice 3 of chamber base 2. Tubular portion 6 includes a shoulder 30 that bears axially against a downstream wall 31 of the chamber base. Baffle 4 is soldered onto chamber base 2. Tubular portion 6 has a lateral wall 33 that extends in the direction of reference axis Y. Lateral wall 33 is cylindrical about reference axis Y. Tubular portion 6 has a first upstream end 9 that is surrounded by a first radially projecting collar 10 of lateral wall 33 of tubular portion 6. Tubular portion 6 also has a radially projecting shoulder 34 of lateral wall 33. First collar 10 and shoulder 34 together define an annular channel 35 that has a rotational symmetry about reference axis Y.
Bowl 7 comprises a cylindrical portion 8 that has a rotational symmetry about reference axis Y. Cylindrical portion 8 also has a lateral wall 36 that extends in the direction of reference axis Y. Cylindrical portion 8 has a second upstream end 11 that is surrounded by a second radially projecting collar 12 of lateral wall 36 of cylindrical portion 7. Cylindrical portion 8 is inserted into tubular portion 6 in such manner that second upstream end 11 of cylindrical portion exits the first upstream end 9 of tubular portion 6.
Second collar 12 bears axially against first collar 10.
The system for attaching the injection system to the baffle according to one embodiment of the invention will now be described in greater detail with reference to
The attachment system according to the invention comprises clamping means. According to one embodiment, these clamping means include a retaining bushing 37 and a retained bushing 38.
Retaining bushing 37 comprises a retaining ring 39 that extends transversely to reference axis Y. Retaining ring 39 has a rotational symmetry about reference axis Y. Retaining ring 39 is inserted radially into annular channel 35 and bears axially against first collar 10.
Retaining bushing 37 also comprises a retaining peripheral skirt 40 that is joined to retaining ring 39. Retaining peripheral skirt 40 is arranged about the periphery of retaining ring 39 and projects axially from retaining ring 39. Retaining peripheral skirt 40 has a cylindrical symmetry about reference axis Y.
Retaining bushing 37 is split into multiple sections, shown here as two half-rings, to enable them to be inserted in annular channel 35. However, it would also be conceivable to split retaining bushing 37 into more than two sections without exceeding the boundaries of the invention.
Retaining bushing 37 also comprises at least two attachment lugs 41, each bushing section having at least one of the attachment lugs 41. According to a preferred embodiment, the retaining bushing comprises four attachment lugs 41 distributed about the periphery of retaining bushing 37. Each attachment lug 41 is connected to retaining peripheral skirt 40. Together with retaining peripheral skirt 40, attachment lugs 41 define a peripheral channel 42. Peripheral channel 42 extends around reference axis Y.
Retained bushing 38 includes a retained ring 43 that bears axially against second collar 12, and a retained peripheral skirt 44 projecting axially from second collar 12. Retained peripheral skirt 44 is arranged on the periphery of retained ring 43.
Retaining bushing 37 and retained bushing 38 are conformed such that they are able to slot into one another while retaining bushing 37 bears axially against first collar 10 and retained bushing 38 bears axially against second collar 12.
For this purpose, retaining peripheral skirt 40 has a height h1 that is lower than height h2 of the assembly formed by the first collar and the second collar that bear against one another.
Retained peripheral skirt 44 also has a height h3 that is lower than height h4 of peripheral channel 42.
The attachment system according to the invention further comprises attachment means.
In this embodiment, the attachment means comprise weld beads or weld spots 45 that join each attachment lug 41 to retained bushing 38 in such manner that retaining bushing 37 and retained bushing 38 axially clamp first and second collars 10 and 12 between them. The attachment means advantageously have four weld spots.
Each attachment lug has an upstream surface 55. Retained ring 43 has an upstream surface 54. In order to facilitate the welding of each attachment lug to the retained bushing, attachment lugs 41 and the retained bushing are dimensioned such that when retaining ring 39 is pressed flush against first collar 10 and retained ring 43 is pressed flush against second collar 12, the upstream surface 55 of each attachment lug 41 is aligned axially with the upstream surface 54 of retained ring 43.
In addition, each attachment lug 41 has a chamfered zone 57 at the intersection between the upstream surface 55 thereof and a second, lateral surface 58 of peripheral channel 42. This chamfered zone 57 is preferably bevelled.
In the same way, retained bushing 38 has a chamfered zone 56 between the upstream surface 54 thereof and the external surface 59 of retained peripheral skirt 44. This chamfered zone 56 is also preferably bevelled, such that, when retained peripheral skirt 44 is inserted in peripheral channel 42 chamfered zones 56 and 57 combine to form an annular groove 60. Weld bead 45 is preferably deposited in this annular groove 60.
Additionally, retained peripheral skirt 40 preferably has a radial dimension that is adjusted with respect to the radial dimension of annular channel 42, such that retained peripheral skirt 40 is able to enter the peripheral channel, and when retained peripheral skirt 40 is inserted in the annular channel it is at least almost completely unable to move radially.
Thus, according to the invention first collar 10 and second collar 12 are axially pressed flush against one another. There is no axial freeplay at all between retaining bushing 37, retained bushing 38 and the two collars 10 and 12, such that injection system 1 is axially immobilised relative to baffle 4.
The invention thus enables wear on the injector nozzle to be reduced. In order to further reduce wear on the injector nozzle, the invention described in this document is preferably combined with means that enable the sliding cross piece to be immobilised axially with respect to spiral structure 19.
To this end,
To this end, sliding cross piece 20 comprises a platform 46 contained inside a cavity 28 of the spiral structure. This cavity 28 is delimited by a base 47, a closure cup 48 and a lateral wall 49. Platform 46 bears axially against base 47 of cavity 28. The immobilisation means preferably include a washer 50 that bears axially against platform 46, and spring means 51 that are restrained axially between washer 50 and closure cup 48. These spring means 51 exert a force on platform 46 that is sufficient to prevent any vibration by the sliding cross piece inside cavity 28 while still allowing the sliding cross piece to move radially and thus withstand differential expansions.
These spring means 51 advantageously comprise a corrugated metal strip in the form of a ring.
The immobilisation means are described in greater detail in the document FR 1056125.
A method for attaching the injection system inside the combustion chamber described with reference to
a shows a perspective view of a chamber base 2, to which a baffle 4 is soldered. Baffle 4 comprises a plate 5 and a tubular portion 6. A bowl 7 has a cylindrical portion 8. Cylindrical portion 8 is inserted in tubular portion 6 as was described with reference to
In a first step, shown in
In a second step, shown in
In a third step, the two half-rings 52 and retained bushing 38 are clamped axially, using a pair or pincers or pliers for example, in such manner that they are clamped axially from both sides by the assembly consisting of first and second collars 10 and 12.
In a fourth step, attachment lugs 41 are welded to retained bushing 38. The two half-rings 52 and retained bushing 38 are thus joined together around first collar and second collar in such a position that the two collars are immobilised axially between the two half-rings 52 and retained bushing 38.
Of course, the invention is not limited to the embodiments described with reference to the figures, and variants might be conceivable without exceeding the boundaries of the invention. In particular, the geometry of the combustion chamber might be varied, as it could also be changed for any of the elements that make up the injection system. The clamping and attachment means might also have other forms.
For the purposes of an example,
Retaining bushing 37′ is split into several bushing sections, as in the embodiment described with reference to
Retained bushing 38′ comprises a retained ring 43′ and a retained peripheral skirt 44′. Retained peripheral skirt 44′ and peripheral channel 42′ are dimensioned in such manner that retained peripheral skirt 44′ is able to be inserted in peripheral channel 42′ without interfering with the axial bracing of retaining ring 39′ against second collar 12 and axial bracing of retained ring 43′ against first collar 10. In the same way, the internal retaining skirt is dimensioned such that it is able to surround the two collars 10 and 12 without interfering with the axial bracing of retaining ring 39′ against second collar 12 and the axial bracing of retained ring 43′ against first collar 10.
Retaining bushing 37′ and retained bushing 38′ axially clamp the two collars between themselves and prevent all axial movement thereof. Retaining bushing 37′ and retained bushing 38′ are joined in this position by a weld bead 45′ that may be continuous or discontinuous.
External retaining skirt 53 has an upstream end that is substantially aligned with retained ring 43′ so as to facilitate the welding of these two elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1056831 | Aug 2010 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR11/51909 | 8/12/2011 | WO | 00 | 2/26/2013 |
