Turbine distributor

Abstract

This document describes a turbine distributor comprising: an inner and an outer shell; a plurality of blades arranged between the shells; a pocket (20) formed in an outer platform (16) of the outer shell, between two circumferentially adjacent blades (12), the pocket (20) having a bottom (22) and stiffeners (26) projecting from the bottom (22); a plate covering the pocket (20) at a radial distance from the stiffeners (26); and studs (28) projecting from the bottom (22) on which the plate rests. Abstract figure: Figure 3

Description

Title of the invention: Turbine distributor technical field

[0001] This disclosure relates to the design of a turbine distributor and more particularly to the maintenance of such a distributor. Previous technique

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products, the integration and use of which in civil aviation result in moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] In this context, engine efficiency is constantly being improved, which sometimes impacts the temperature of the gases or structural elements downstream of the combustion chamber. Controlling turbine temperatures is essential for reasons of mechanical strength and to control expansion deformations.

[0005] French patent document FR 3 080 406 A1 describes a turbine distributor in which the blades are hollow and adapted to receive a flow of air cooling the blades, drawn from the compressor. To prevent the internal cavity of the blade from becoming blocked, blocking elements such as pins or hoops are provided at the blade tip.

[0006] To improve the cooling of the turbine distributors, it may be necessary to further complicate their design, but in general, a complex design often leads to additional difficulties during engine manufacturing or maintenance operations.

[0007] The present application therefore aims to propose a design which allows better control of the temperature rise of the distributor without presenting disadvantages during maintenance. Summary

[0008] To this end, the present document relates to a turbine distributor forming a ring around an axis and comprising: an inner shell comprising a plurality of inner platforms arranged circumferentially around the axis and an outer shell comprising a plurality of outer platforms arranged circumferentially around the axis; a plurality of blades arranged radially between the inner shell and the outer shell; a pocket formed in an outer platform between two circumferentially adjacent blades, the pocket having a bottom and stiffeners extending in projection from the bottom; a sheet covering the pocket radially at a distance from the stiffeners; and studs extending in projection from the bottom and on which the sheet rests.

[0009] The pocket allows for a more refined structure and therefore faster heat dissipation. It also allows the circulation of a flow of cold air, for example, drawn from an upstream portion of the engine. The stiffeners mechanically reinforce the distributor structure to compensate for the loss of rigidity due to the presence of the pocket. The pocket is covered with a sheet metal plate that may need replacing during the engine's lifespan: the plate or its brazed connection to the distributor may be damaged. To anticipate damage during plate removal and positioning inaccuracies during the installation of a new plate, the studs are designed to serve both as a reference point for the operator removing the plate (for example, with an electrode desoldering process) and as a stop during the installation of a new plate.

[0010] According to an advantageous embodiment, the stiffeners project from the bottom of a first height and the supports project from the bottom of a second height, the second height being at least three times greater than the first height. This safety factor of three times ensures a minimum clearance above the stiffeners so that the pocket remains sufficiently spacious relative to the stiffeners: stiffeners that are too large compared to the total height of the pocket would impede air circulation and / or reduce the efficiency of heat exchange between the platform and the air.

[0011] According to an advantageous embodiment, the pocket comprises through openings for fluid circulation and the sheet comprises through orifices in fluid communication with the through openings of the pocket, the studs comprising upstream studs in the vicinity of the through orifices and circumferentially offset from the through orifices, and downstream studs in the vicinity of the Through-holes are circumferentially offset from the through-holes. The "neighborhood" here refers to a distance between the studs and the orifices, or vents respectively, that is less than 20% of the axial length of the bag. These offsets prevent the studs from obstructing the proper flow of air (and therefore heat dissipation) when air enters or exits the bag at the vents and orifices.

[0012] According to an advantageous embodiment, the bottom of the pocket is delimited by a contour formed by an upstream edge, a downstream edge, and two lateral edges, the pads being arranged at a distance from all the edges and at a distance from a median line equidistant from the lateral edges. The airflow may experience boundary layer effects in the vicinity of the lateral edges, and the airflow may have a non-uniform flow rate over the entire cross-section of the pocket, with, in particular, a higher flow rate along a median line, which has more orifices and vents than the rest of the pocket. The arrangement of the pads set back from the lateral edges avoids an aerodynamic blocking effect, and the arrangement of the pads set back from the median line prevents the line of highest flow rate from encountering obstacles.

[0013] According to an advantageous embodiment, the pads have a circular or elliptical cross-section. These cross-sections are aerodynamic and therefore allow air to flow easily around the pads. In particular, the orientations of the ellipses can be aligned with the velocity field lines of the airflow in the pocket.

[0014] According to an advantageous embodiment, the distributor comprises three pairs of studs, including two upstream studs, two central studs, and two downstream studs. This arrangement ensures a constant radial height from upstream to downstream for the ladle (and therefore well-controlled cooling), particularly when the sheet metal is curved (viewed in a longitudinal plane). Without this arrangement, deformations of the sheet metal could damage the ladle.

[0015] According to an advantageous embodiment, the bottom of the pocket is delimited by a contour formed by an upstream edge, a downstream edge, and two lateral edges. The stiffeners extend parallel to the upstream and / or downstream edge, from one lateral edge to the other. The central supports are arranged between two adjacent stiffeners, the upstream supports are arranged between the upstream edge and a stiffener, and the downstream supports are arranged between the downstream edge and a stiffener. Thus, by offsetting the supports relative to the stiffeners, the latter are not subjected to mechanical stresses.

[0016] According to an advantageous embodiment, the studs are formed from the material of the external platform that includes the pocket. Alternatively, the studs are attached to the external platform that includes the pocket and are made of a harder material than the material constituting the external platform that includes the pocket. According to one variant, studs are attached to the external platform and are made of the same material as the external platform. According to another variant, one or more studs are made from a single piece of material (i.e., monoblocs, formed with the platform) and one or more other studs are attached to the pocket (for example by welding, or removable fixing).

[0017] The invention also relates to a method of replacing a distributor plate, for a distributor according to one of the embodiments described above, the method comprising removing the distributor plate by means of a desoldering operation, placing a replacement plate in contact with the studs and brazing the replacement plate to the external platform which includes the pocket.

[0018] As mentioned above, the presence of the pads prevents too much material from being removed during desoldering, and then allows the new sheet metal to be positioned correctly.

[0019] The cooling benefit obtained by the design proposed by the invention is therefore not accompanied by any disadvantages related to its maintenance. Brief description of the drawings

[0020] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0021] [Fig-1] is an isometric view of a distributor segment according to the present disclosure;

[0022] [Fig.2] is a front view as well as a cross-section of the sheet metal;

[0023] [Fig.3] is an isometric view of a pocket with the stiffeners and studs, the sheet metal being illustrated in transparency;

[0024] [Fig.4] is a front view of the pocket;

[0025] [Fig.5] is a cross-section of the external platform and sheet metal. Description of the implementation methods

[0026] Figure 1 shows a turbine distributor 10. The distributor 10 can be a high-pressure or low-pressure turbine distributor. The distributor 10 is formed as a ring around an axis A, with an inner ferrule 2 and an outer ferrule 4. The distributor 10 is mainly composed of an annular row of blades 12 extending substantially in a radial direction R, between the inner ferrule 2 and the outer ferrule 4.

[0027] The ferrules 2, 4 can be formed from several angular sectors assembled together (see right-hand side of [Fig. 1]), or they can be a single piece and extend 360° around a rotation axis A of a turbomachine. As illustrated on the left-hand side of [Fig. 1], the ferrule sectors 2, 4 comprise an inner platform 14, an outer platform 16, and one or more blades 12. Thus, the entire assembly of blades 12 and platforms 14, 16 can be formed in one piece, obtained from material by casting or plastic deformation.

[0028] The blades 12 and the platforms 14, 16 define a gas stream. Upstream of the distributor, the gas flows mainly in the axial direction A. Downstream of the distributor 10, the gas flow is deflected and its velocity therefore has a tangential component, enabling the rotation of the turbine (not shown) located downstream of the distributor 10.

[0029] Each blade 12 can be hollow and can have an internal cavity 13 which can extend over the entire radial height of the blade 12. This cavity 13 is in fluidic connection with a cold air source and it thus makes it possible to control the temperature rise in the blade 12.

[0030] At the level of the external platform 16, the inter-blade spaces in a circumferential direction, identified by the arrow T, accommodate a pocket (20 in [Fig. 3] and subsequent figures). [Fig. 1] shows plates 18 covering these pockets.

[0031] A sheet metal plate 18 is shown in detail in [Fig. 2], in front view and in cross-section. The sheet metal plate 18 is in the form of a plate or a cover, with an upper surface 18.1 (also visible in [Fig. 1]) and a lower surface 18.2 facing the pocket (number 20 in [Fig. 3]). The thickness of the sheet metal plate 18 can be constant, and the sheet metal plate 18 can be curved to follow the curvature of the external platform 16. The contour 18.3 of the sheet metal plate 18 can include an upstream edge and a downstream edge, both substantially straight (in the front view, but curved to follow the curvature around the axis of the turbomachine, marked A in [Fig. 1]). The contour 18.3 also includes lateral edges which essentially follow the shape of the extrados and intrados profiles of the blades 12. Thus, the sheet 18 occupies all the space between two circumferentially adjacent blades 12.

[0032] The contour 18.3 is intended to be brazed onto the external platform 16. It may happen that the sheet 18 or the brazing bonding it to the platform 16 deteriorates, the sheet 18 thus having to be replaced.

[0033] The sheet 18 also includes orifices 18.4 allowing air to circulate into or out of the pocket. The orifices 18.4 may be regularly distributed in a circumferential direction and / or may be arranged in an upstream portion of the sheet 18.

[0034] Figure 3 shows a pocket 20 formed in the outer platform 16, covered by a sheet metal 18 shown in transparency. This pocket 20 is blind in the sense that it opens radially outwards from the platform 16, but not inwards. The pocket 20 can occupy a large part of the space between two adjacent blades (or between two cavities 13). A "large part" can be understood like the entire inter-blade space except for a slight border allowing brazing of sheet 18 (see "B" on [Fig.5]).

[0035] The pocket 20 has a bottom 22 which can be provided with openings 24 for supplying or expelling a flow of air into / from the pocket 20. The openings 24 can be distributed regularly circumferentially and / or can be arranged in a downstream part of the pocket 20. Advantageously, the openings 24 are arranged opposite the orifices 18.4 of the sheet 18, that is to say that some are arranged near a downstream end of the pocket and others are arranged near an upstream end.

[0036] From the bottom 22 extend stiffeners 26. These can be parallel to each other and / or parallel to one of the sides of the pocket 20. In the illustrated example, the stiffeners 26 are mainly circumferential.

[0037] The pocket 20 also accommodates studs 28. These studs 28 have the dual function of keeping the sheet 18 away from the bottom 22, to ensure that the pocket 20 retains a certain volume under all circumstances (thermal and mechanical stresses), but also of serving as a reference point for the operator during a maintenance operation and in particular during an operation of unsoldering the sheet 18 and repositioning a replacement sheet 18.

[0038] The pads 28 can be integral with the platform 16 or attached to it. When attached, the pads 28 can be made of a material different from that of the platform 16, and in particular a harder material. Thus, even when the plate 18 is damaged, the pads remain intact and the distance between the bottom 22 and the plate 18 remains unchanged.

[0039] The studs 28 can be distributed over the entire surface of the base 22. In the illustrated example, 6 studs are shown, grouped into 3 pairs of studs, the studs in each pair sharing the same axial position. A smaller or larger number of studs 28 is possible.

[0040] Figure 4 shows a top view of the pocket 20, with the upstream end at the bottom of the figure and the downstream end at the top. The bottom 22 of the pocket 20 is delimited by a contour comprising an upstream edge 22.1, two lateral edges 22.2, 22.3, and a downstream edge 22.4. In the illustrated version, the upstream edges 22.1 and downstream edges 22.4 are substantially parallel and are oriented in the circumferential direction. The lateral edges 22.2, 22.3 follow the contours of the cavities 13 of the blades 12.

[0041] The plate 18 and the base 22 have a substantially identical outline, except that the plate 18 is slightly larger. The plate 18 can thus cover the entire pocket 20 and be brazed to the platform 16, radially above, opposite the pocket 20.

[0042] Figure 4 also shows the studs, including a pair of upstream studs 28.1, a pair of central studs 28.2 and a pair of downstream studs 28.3. The upstream studs 28.1 are arranged between the upstream edge 22.1 and a stiffener 26, the central studs 28.2 are arranged between two successive stiffeners 26 and the downstream studs 28.3 are arranged between a stiffener 26 and the downstream edge 22.4. Other distributions or a different number of studs are naturally conceivable but this distribution and this number are particularly suitable for properly supporting the sheet 18 of Figure 2.

[0043] The studs 28.1, 28.2, 28.3 are located at a distance from the edges 22.1, 22.2, 22.3, 22.4 of the bottom and from a median line 30. This median line 30 is the average distance between the lateral edges 22.2, 22.3. Depending on the arrangement of the orifices 18.4 and the vents 24, and particularly when these are regularly distributed from one lateral edge to the other, the median line 30 is the line along which the airflow has the greatest speed, due to edge effects. It is therefore advisable to keep the studs 28 away from this line. Similarly, it is advantageous to keep the studs 28 away from the lateral edges to avoid aerodynamic obstruction.

[0044] It is also visible in [Fig. 4] that the pads 28 have a circular cross-section (they are cylinders with a fillet connecting to the bottom 22). Other cross-sections are possible, such as an elliptical cross-section or a cross-section with an intrados and an extrados. In this case, the pads are oriented to maximize the flow between the vents 24 and the orifices 18.4. It is also possible, when the pads are attached to the platform, to provide pads with controlled orientation in order to regulate the flow in the pocket 20. A suitable mechanism (such as a VSV synchronizing ring) could be considered. It is also possible to provide heat dissipation elements (for example, fins that can be parallel to the bottom 22) on the pads 28 in order to increase the contact area between the platform 16 and the airflow circulating in the pocket.

[0045] Figure 5 shows a cross-section of the pocket 20. It shows the stiffeners 26, the studs 28, the orifices and openings 18.4, 24, and a blade 12. The areas marked B are the brazing areas of the sheet 18 to the platform 16. Figure 5 also shows the heights H1 and H2 of the stiffeners 26 and studs 28, respectively. In the illustrated example, the stiffeners and studs are all the same height. However, other designs are possible, particularly with a height that increases or decreases from upstream to downstream.

[0046] The invention also relates to a maintenance method. In this method, a sheet metal part needs to be replaced. The maintenance method includes removing the sheet metal from the platform, for example, by means of a desoldering process using electrodes. The operator can use the pads 28 as indicators of the limit of the material to be desoldered. A new sheet metal part can then be placed in contact with the pads 28.

[0047] In an alternative not shown, the sheet metal 18 may have blind holes intended to accommodate the head of the studs 28. This solution allows the sheet metal to be centered during its installation, or even to serve as a keying device.

[0048] In an alternative not shown, the studs are either integral with the sheet metal or attached to the sheet metal. They can then rest on the bottom 22 of the pocket 20. In this case, the bottom 22 of the pocket 20 may have wells receiving the heads of the studs.

Claims

Demands

1. Turbine distributor (10) forming a ring (10) around an axis (A) and comprising: an inner shell (2) comprising a plurality of inner platforms (14) arranged circumferentially around the axis (A) and an outer shell (4) comprising a plurality of outer platforms (16) arranged circumferentially around the axis (A); a plurality of blades (12) arranged radially between the inner shell (2) and the outer shell (4); a pocket (20) formed in an outer platform (16) between two circumferentially adjacent blades (12), the pocket (20) having a bottom (22) and stiffeners (26) projecting from the bottom (22); a plate (18) covering the pocket (20) radially at a distance from the stiffeners (26);and studs (28) projecting out from the bottom (22) and on which rests the plate (18), the pocket (20) comprising through openings (24) for fluid circulation and the plate comprising through orifices (18.4) in fluid communication with the through openings (24) of the pocket (20), the studs (28) comprising upstream studs (28.1) arranged in the vicinity of the through orifices (18.4) and circumferentially offset from the through orifices (18.4), and downstream studs (28.3) arranged in the vicinity of the through openings (24) and circumferentially offset from the through openings (24)...;

2. Distributor (10) according to claim 1, characterized in that the stiffeners (26) extend in projection from the bottom (22) of a first height (H1) and the studs (28) extend in projection from the bottom (22) of a second height (H2), the second height (H2) being at least three times greater than the first height (H1).

3. Distributor (10) according to any one of claims 1 to 2, characterized in that the bottom (22) of the pocket (20) is delimited by a contour (22.1, 22.2, 22.3, 22.4) formed of an upstream edge (22.1), a downstream edge (22.4) and two lateral edges (22.2, 22.3), the pads (28) being arranged at a distance from all the edges (22.1, 22.2, 22.3, 22.4) and at a distance from a median line (30) equidistant from the lateral edges (22.2, 22.3).

4. Distributor (10) according to any one of claims 1 to 3, characterized in that the studs (28) have a circular or elliptical cross-section.

5. Distributor (10) according to any one of claims 1 to 4, characterized in that it comprises three pairs of studs (28), of which two upstream studs (28.1), two central studs (28.2) and two downstream studs (28.3).

6. Distributor (10) according to the preceding claim, characterized in that the bottom (22) of the pocket (20) is delimited by a contour formed of an upstream edge (22.1), a downstream edge (22.4) and two lateral edges (22.2, 22.3), the stiffeners (26) extending parallel to the upstream edge (22.1) and / or the downstream edge (22.4), from one lateral edge (22.2) to the other lateral edge (22.3), the central studs (28.2) being arranged between two adjacent stiffeners (26), the upstream studs (28.1) being arranged between the upstream edge (22.1) and a stiffener (26), and the downstream studs (28.3) being arranged between the downstream edge (22.4) and a stiffener (26).

7. Dispenser (10) according to any one of claims 1 to 6, characterized in that the pads (28) are made of material with the external platform (16) which includes the pocket (20).

8. Dispenser (10) according to any one of claims 1 to 6, characterized in that the studs (28) are attached to the external platform (16) which includes the pocket (20) and are made of a harder material than the material constituting the external platform (16) which includes the pocket (20).

9. Method of replacing a distributor plate (18), for a distributor (10) according to any one of claims 1 to 8, the method comprising removing the distributor plate (18) by means of a desoldering operation, placing a replacement plate (18) in contact with the studs (28) and brazing the replacement plate (18) to the external platform (16) which includes the pocket (20).