Sector of a guide vanes assembly for a turbine of an aircraft turbomachine

Abstract

Sector (6) of a guide vanes assembly for a turbine of an aircraft turbomachine, the sector (6) comprising an outer platform (7) and an inner platform (8) which are coaxial along an axis (X), the sector (6) further comprising at least one blade (9) which connects the outer and inner platforms (7, 8) together, characterized in that the blade (9) is variable-pitch about an axis of rotation (Y) of the blade (9), the blade (9) comprising an aerodynamic body (11) delimited radially by a head and a root, the head being placed with a first functional clearance in an opening of the outer platform (7), the root being placed with a second functional clearance in a cavity of the inner platform (8), the axis of rotation (Y) of the blade (9) being located downstream of the head and the root.

Description

[0001]

[0002] Technical field of the invention

[0003] The present invention relates to a sector of a distributor for a turbine of an aircraft turbomachine, and more generally to a distributor comprising such sectors.

[0004] Technical background

[0005] Conventionally, a turbomachine turbine comprises at least one stage comprising a fixed bladed distributor and a moving bladed wheel.

[0006] More specifically, the distributor comprises an outer crown and an inner crown coaxial along an X axis, the outer and inner crowns being connected to each other by an annular row of blades.

[0007] Such a distributor is usually sectorized and comprises an annular row of sectors placed end to end around the X axis, each sector comprising, for example, two or three fixed-pitch blades.

[0008] The sectorization of the distributor necessarily implies the presence of a misalignment, however small, between the sectors around the X axis. This misalignment can for example be observed by the presence of steps between two successive sectors, at the level of the crowns.

[0009] Such misalignment means that the nozzle flow section is not uniform around the X axis, to the detriment of the turbomachine's efficiency. In addition, the steps created by this misalignment generate disturbances within the flow, which also have a negative impact on the turbomachine's efficiency.

[0010] To correct or minimize this misalignment, various machining operations can be performed after the distributor has been assembled. However, such operations are complex to implement and significantly increase the manufacturing time of the distributor, to the detriment of productivity. It is worth noting that the aforementioned machining operations are only permitted during the manufacturing of the engine, i.e. before it is put into service.

[0011] Furthermore, engine manufacturers note that the optimal passage section depends on many parameters (e.g. external environment, number of engine operating hours, etc.), and that it would be profitable to be able to adjust this passage section throughout the engine's lifetime, which is not currently possible.

[0012] The objective of the present invention is therefore to provide a simple, effective and economical solution making it possible to respond at least partially to the aforementioned problems.

[0013] The prior art also includes document US2009 / 067978A1.

[0014] Summary of the invention

[0015] The invention thus proposes a sector of a distributor for a turbine of an aircraft turbomachine, the sector comprising an external platform and an internal platform coaxial along an axis X, the sector further comprising at least one blade which connects the external and internal platforms together, characterized in that the blade has variable pitch around an axis of rotation Y of the blade, the blade comprising an aerodynamic body delimited radially by a head and a root, the head being placed with a first functional clearance in an opening of the external platform, the root being placed with a second functional clearance in a cavity of the internal platform, the axis of rotation Y of the blade being located downstream of the head and the root.

[0016] The installation of variable-pitch blades on the distributor allows the passage section of the distributor to be adjusted by adjusting the pitch of the different blades.

[0017] Such an adjustment thus makes it possible to homogenize the passage section of the distributor, to the benefit of the efficiency of the turbine, and more generally of the turbomachine.

[0018] Such adjustment can be carried out throughout the engine's service life, for example during engine assembly or during engine maintenance.

[0019] Such positioning of the Y rotation axis generally makes it possible to optimize the passage section of the distributor.

[0020] The sector according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other:

[0021] - the blade is guided in rotation around its axis of rotation Y via a cylindrical portion of the blade which is inserted into an orifice of the external platform and a spherical portion of the blade which is inserted into a housing of the internal platform;

[0022] - the pitch of the blade is adjusted via a control element which is integral with the blade and which is arranged outside the external platform, the control element being guided by a guide device placed between the control element and the external platform;

[0023] - the control element is fixed on an external face of the blade head;

[0024] - the guide device comprises a frame in which are housed carrier balls and / or a self-lubricating pad;

[0025] - the root of the blade is held radially in the cavity via several pins, each pin being partly housed in a hole in the root and partly housed in a groove in the cavity;

[0026] - the sector comprises several blades which each connect the external and internal platforms, each of the blades being variable in pitch around its Y axis of rotation.

[0027] The present invention also relates to a distributor for a turbine of an aircraft turbomachine, the distributor comprising a plurality of sectors as described previously, the sectors being placed end to end around the X axis. The present invention also relates to a turbine of an aircraft turbomachine comprising a distributor as described previously.

[0028] The present invention further relates to an aircraft turbomachine comprising a distributor as described above or a turbine as described above.

[0029] The present invention finally relates to a method for mounting or maintaining a distributor as described previously, the method comprising at least the step consisting of: a1) adjusting the timing of the blades of the sectors, so as to homogenize the passage section of the distributor which is defined between the external and internal platforms of the sectors.

[0030] Brief description of the figures

[0031] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0032] [Fig.1] Figure 1 is a partial axial half-sectional view of a turbomachine comprising a distributor according to the invention;

[0033] [Fig.2] Figure 2 is a detailed perspective view of a sector of the distributor illustrated in Figure 1;

[0034] [Fig.3] Figure 3 is a detailed and perspective view of the external and internal platforms of the sector illustrated in Figure 2;

[0035] [Fig. 4] Figure 4 is a first detailed and perspective view of a blade of the sector illustrated in Figure 2;

[0036] [Fig.5] Figure 5 is a second detail and perspective view of a blade of the sector illustrated in Figure 2;

[0037] [Fig.6] Figure 6 is a perspective view illustrating a first step of a method of mounting the sector illustrated in Figure 2;

[0038] [Fig.7] Figure 7 is a detail and perspective view of the first step; [Fig.8] Figure 8 is a perspective view illustrating a second step of the method of mounting the sector illustrated in Figure 2;

[0039] [Fig.9] Figure 9 is a perspective view illustrating a third step of the method of mounting the sector illustrated in Figure 2;

[0040] [Fig.10] Figure 10 is a perspective view illustrating a fourth step of the method of mounting the sector illustrated in Figure 2;

[0041] [Fig.11] Figure 11 is a perspective view illustrating a fifth step of the method of mounting the sector illustrated in Figure 2;

[0042] [Fig.12] Figure 12 is a first detailed and perspective view of the fifth stage;

[0043] [Fig.13] Figure 13 is a second detailed and perspective view of the fifth stage;

[0044] [Fig.14] Figure 14 is a top view illustrating a step of a method of mounting or maintaining a distributor according to the invention;

[0045] [Fig.15] Figure 15 is a front view of the step illustrated in Figure 14.

[0046] Detailed description of the invention

[0047] In Figure 1 is partially represented an aircraft turbomachine 1, the turbomachine 1 being for example a turbojet, a turboprop or a turboshaft engine.

[0048] The turbomachine 1 conventionally comprises from upstream to downstream, depending on the direction of gas flow, at least one compressor, a combustion chamber 2 and at least one turbine 3.

[0049] According to the embodiment illustrated in Figure 1, the turbomachine 1 comprises a high-pressure turbine 3 arranged directly downstream of the combustion chamber 2 and a low-pressure turbine (not shown) arranged downstream of the high-pressure turbine 3. The high-pressure turbine 3 comprises a single high-pressure stage comprising a distributor 4 and a movable wheel 5. The distributor 4 is arranged directly downstream of the combustion chamber 2 and the wheel 5 is arranged directly downstream of the distributor 4. The wheel 5 is movable in rotation about a longitudinal axis X of the turbomachine 1.

[0050] The distributor 4 is annular and sectorized, and thus comprises a plurality of sectors 6 placed end to end around the X axis. The distributor 4 and the sectors 6 of the distributor 4 are also defined along the X axis.

[0051] Each sector 6 comprises an external platform 7 and an internal platform 8 coaxial along the X axis. The sector 6 further comprises at least one blade 9 which connects the external and internal platforms 7, 8 together.

[0052] According to the invention, said at least one blade 9 of the sector 6 has variable pitch around an axis of rotation Y of the blade 9. The blade 9 comprises an aerodynamic body 11 delimited radially by a head 12 and a root 13. The head 12 is placed with a first functional clearance in an opening 14 of the external platform 7. The root 13 is placed with a second functional clearance in a cavity 15 of the internal platform 8. The axis of rotation Y of the blade 9 is located downstream of the head 12 and the root 13.

[0053] A sector 6 can obviously comprise several blades 9 (for example two or three) which each connect the external and internal platforms 7, 8, each of the blades 9 being variable in pitch around its axis of rotation Y.

[0054] The installation of variable-pitch blades on the distributor allows the passage section of the distributor to be adjusted by adjusting the pitch of the different blades.

[0055] Such an adjustment thus makes it possible to homogenize the passage section of the distributor, to the benefit of the efficiency of the turbine, and more generally of the turbomachine.

[0056] Such adjustment can be carried out throughout the engine's service life, for example during engine assembly or during engine maintenance.

[0057] Such positioning of the Y rotation axis generally makes it possible to optimize the passage section of the distributor.

[0058] The illustrated example is in no way limiting, the distributor 4 (or the sector 6) according to the invention could be installed in the low pressure turbine of the turbomachine 1.

[0059] By convention in this application, "axial" or "axially" means any direction parallel to the X axis, and "radial" or "radially" means any direction perpendicular to the X axis.

[0060] Further, by convention in this application, the terms "internal" and "external" are defined radially relative to the X-axis.

[0061] The external and internal platforms 7, 8 delimit a vein 10 in which the gases resulting from the combustion of the air / fuel mixture flow.

[0062] By convention, in the present application, the terms “upstream” and “downstream” are defined in relation to the direction of flow of the gases in the turbomachine 1.

[0063] As illustrated in the figures, the external and internal platforms 7, 8 are each in the form of an arc of a circle around the axis X. Each sector 6 comprises two variable-pitch blades 9, each of the blades 9 being adjustable around its axis of rotation Y. The axis of rotation Y of a blade is substantially radial. The pitch of a blade 9 is generally quantified via a pitch angle. The adjustment of the pitch of the blades 9 may be independent or common, and in other words the blades 9 may be adjusted independently of each other, or in a common manner. The adjustment of the pitch of the blades 9 may be manual or automatic. In the case of automatic adjustment, the distributor 4 comprises a control device comprising for example one or more actuators and one or more mechanisms, the mechanism(s) connecting the actuator(s) to the blades 9.The blade pitch adjustment 9 is carried out when the engine is stopped, for example during assembly or maintenance.

[0064] As indicated above, each blade 9 comprises an aerodynamic body 11 delimited radially by a head 12 and a root 13. The head 12 is placed with a first functional clearance in an opening 14 of the external platform 7 and the root 13 is placed with a second functional clearance in a cavity 15 of the internal platform 8. The first and second functional clearances are positive and dimensioned to allow the adjustment of the pitch over a predetermined range (for example plus or minus five degrees relative to a reference position).

[0065] As indicated above, the axis of rotation Y of each blade 9 is located downstream of its head 12 and its root 13.

[0066] As illustrated in Figures 4 and 5, the body 11 of each blade 9 is delimited transversely by a leading edge 16 and a trailing edge 17, the leading edge 16 being arranged upstream of the trailing edge 17 in the direction of flow of the gases around the blade 9. The leading and trailing edges 16, 17 are connected to each other by a lower surface face 18 and an upper surface face 19 of the body 11, these lower and upper surfaces 18, 19 being curved, and respectively concave and convex.

[0067] The head 12 of each blade 9 has a contour or profile similar to that of the body 11, with reduced dimensional characteristics. The head 12 extends radially in the extension of the body 11 and is surrounded by a shoulder 20. Each opening 14 of the external platform 7 is through and has a contour or profile similar to that of the head 12, with increased dimensional characteristics.

[0068] The root 13 of each blade 9 has a contour or profile similar to that of the body 11, with reduced dimensional characteristics. The root 13 extends radially in the extension of the body 11 and is surrounded by a shoulder 21. Each cavity 15 of the internal platform 8 is blind and has a contour or profile similar to that of the root 13, with increased dimensional characteristics.

[0069] As illustrated in the figures and in particular figures 4, 5, 11 and 14, to cope with the high temperatures of the surrounding space, each blade 9 is hollow and comprises two interior chambers 22 separated by a partition 23. These chambers 22 are supplied by an air flow which bypasses the combustion chamber 2, the air flow being evacuated from the chambers 22 by perforations 24 made in the body 11 of the blade 9, so as to join the gas flow circulating in the vein 10. To optimize the distribution of the air flow, a perforated jacket 25 is mounted in each of the chambers 22 (figure 14).

[0070] Advantageously, each blade 9 is guided in rotation around its axis of rotation Y via a cylindrical portion 26 of the blade 9 which is inserted into an orifice 27 of the external platform 7 and a spherical portion 28 of the blade 9 which is inserted into a housing 29 of the internal platform 8. The cylindrical and spherical portions 26, 28 define the axis of rotation Y of the blade 9.

[0071] The spherical part ensures guidance while providing additional degrees of freedom which are necessary to cope with the deformations caused by thermal expansion, so as to avoid seizure in rotation of the blade 9.

[0072] As illustrated in Figures 4 and 5, the cylindrical portion 26 is located directly downstream of the head 12 and projects outwardly from the body 11. The spherical portion 28 is located directly downstream of the foot 13 and projects inwardly from the body 11.

[0073] A bearing may be inserted between the cylindrical portion 26 and the orifice 27, so as to optimize the rotational guidance of the blade 9. In the same way, a bearing may be inserted between the spherical portion 28 and the housing 29. Advantageously, the setting of each blade 9 is adjusted via a control element 30 which is integral with the blade 9 and which is arranged outside the external platform 7. The control element 30 is guided by a guide device 31 placed between the control element 30 and the external platform 7.

[0074] Advantageously, the guide device 31 comprises a frame 34 in which are housed carrier balls 35 and / or a self-lubricating pad. A self-lubricating pad is for example made of sintered metal (for example bronze) and comprises pores incorporating lubricant (for example oil).

[0075] As illustrated in the figures, the control element 30 is in the form of a collar 30 whose contour or profile is similar to that of the head 12 (or of the opening 14). The collar 30 is fixed on a free external face 32 of the head 12 of the blade 9, for example by brazing. The collar 30 is perforated to allow the supply of air to the interior chambers 22. The collar 30 comprises a finger 33 which can serve as a handle when the adjustment is manual and independent, or as a connecting interface when the adjustment is common and carried out by a control device.

[0076] As illustrated in the figures, the guide device 31 borders the opening 14 and comprises a frame 34 in which carrier balls 35 are housed. The carrier balls 35 are distributed regularly in the frame 34, so as to guide the collar 30 uniformly. The guide device 31 is attached to the external platform 7, and interposed between the collar 30 and the external platform 7. The fixing of the collar 30 ensures the radial retention of the blade 9 relative to the external platform 7. Advantageously, the root 13 of each blade 9 is held radially in the corresponding cavity 15 via several pins 36, each pin 36 being partly housed in a hole 37 of the root 13 and partly housed in a groove 38 of the cavity 15.

[0077] As illustrated in the figures and in particular figures 11 to 13, the root 13 of each blade 9 is held radially in the corresponding cavity 15 via three distributed pins 36, namely a first pin 36 at the leading edge 16, a second pin 36 at the intrados face 18, and a third pin 36 at the extrados face 19. The pins 36 are inserted through the interior chambers 22 and fixed to the blade 9, for example by brazing. The grooves 38 made in the cavity 15 are oblong and sized to allow the adjustment of the timing over a predetermined range (for example plus or minus five degrees relative to a reference position). As illustrated in FIG. 1, the external platform 7 of each sector 6 comprises an upstream sealing system 39 configured to come into axial support with an external wall 40 of the combustion chamber 2, and a downstream sealing system 41 configured to come into axial support with a turbine casing 42.The internal platform 8 of each sector 6 comprises an upstream sealing system 43 configured to come into axial support with an internal wall 44 of the combustion chamber 2, and two fixing lugs 45 configured to be secured to a casing 46 surrounding the combustion chamber 2.

[0078] The distributor 4 also comprises one or more sealing plates (not shown) between two sectors 6 directly adjacent to the external and internal platforms 7, 8, so as to minimize inter-sector leaks.

[0079] For reasons of clarity, the different sealing systems 39, 41, 43 are not shown in Figures 2 to 15.

[0080] The blades 9 or the external and internal platforms 7, 8 of a sector 6 have complex shapes, these parts can for example be manufactured via an additive manufacturing process (for example by selective powder bed fusion) or via a lost wax casting process.

[0081] A sector 6 as illustrated in the figures and as previously described is mounted by a mounting method comprising the steps of: a) attaching a guide device 31 to the external platform 7, for each of the blades 9; (figures 6 and 7) b) jointly placing the head 12 of the blade 9 in an opening 14 of the external platform 7 and the associated cylindrical portion 26 in an orifice 27 of the external platform 7, for each of the blades 9; (figure 8) c) fixing a collar 30 on the external face 32 of the head 12 of the blade 9, for each of the blades 9; (figure 9) d) jointly placing the roots 13 of the blades 9 in the cavities 15 of the internal platform 8 and the associated spherical portions 28 in the housings 29 of the internal platform 8; (figure 10) e) insert each of the three pins 36 into a hole 37 in the foot 13 of the blade 9 and into an associated groove 38, for each of the blades 9;(figures 11-13) f) fix the three pins 36 to the blade 9, for each of the blades 9; g) mount the upstream and downstream sealing systems 39, 41 on the external platform 7, and the upstream sealing system 43 on the internal platform 8. Step a) can be carried out by brazing or welding the frame 34 to the external platform 7.;

[0082] Step c) can be carried out by brazing or welding the collar 30 onto the head 12 of the blade 9.

[0083] In step e), the pins 36 are inserted through the interior chambers 22. Step f) can be carried out by brazing or welding the pins 36 to the interior surfaces defining the chambers 22, the brazing or welding being carried out in the interior chambers 22.

[0084] The distributor 4 as described above is mounted by a mounting method comprising at least the step of: a1) adjusting the timing of the blades 9 of the sectors 6, so as to homogenize the passage section of the distributor 4 which is defined between the external and internal platforms 7, 8 of the sectors 6 (figures 14 and 15).

[0085] Prior to step a1), the sectors 6 of the distributor 4 can be placed end to end around the X axis.

[0086] As illustrated in Figure 14 by the arrows, during step a1), the finger 33 of each blade 9 is actuated in a tangential or circumferential direction (in one direction or the other), so as to adjust the setting of the blade 9.

[0087] The distributor 4 as described above is maintained by a maintenance method comprising at least the step of: a1) adjusting the timing of the blades 9 of the sectors 6, so as to homogenize the passage section of the distributor 4 which is defined between the external and internal platforms 7, 8 of the sectors 6 (figures 14 and 15).

[0088] As illustrated in Figure 14 by the arrows, during step a1), the finger 33 of each blade 9 is actuated in a tangential or circumferential direction (in one direction or the other), so as to adjust the setting of the blade 9.

[0089] For the sake of clarity, only one sector 6 of the distributor 4 is shown in Figures 14 and 15.

Claims

CLAIMS 1. Sector (6) of a distributor (4) for a turbine (3) of an aircraft turbomachine (1), the sector (6) comprising an external platform (7) and an internal platform (8) coaxial along an axis (X), the sector (6) further comprising at least one blade (9) which connects the external and internal platforms (7, 8) together, characterized in that the blade (9) has variable pitch around an axis of rotation (Y) of the blade (9), the blade (9) comprising an aerodynamic body (11) delimited radially by a head (12) and a root (13), the head (12) being placed with a first functional clearance in an opening (14) of the external platform (7), the root (13) being placed with a second functional clearance in a cavity (15) of the internal platform (8), the axis of rotation (Y) of the blade (9) being located downstream of the head (12) and the root (13).

2. Sector (6) according to claim 1, characterized in that the blade (9) is guided in rotation around its axis of rotation (Y) via a cylindrical portion (26) of the blade (9) which is inserted into an orifice (27) of the external platform (7) and a spherical portion (28) of the blade (9) which is inserted into a housing (29) of the internal platform (8).

3. Sector (6) according to one of the preceding claims, characterized in that the setting of the blade (9) is adjusted via a control element (30) which is integral with the blade (9) and which is arranged outside the external platform (7), the control element (30) being guided by a guide device (31) placed between the control element (30) and the external platform (7).

4. Sector (6) according to claim 3, characterized in that the control element (30) is fixed on an external face (32) of the head (12) of the blade (9).

5. Sector (6) according to one of claims 3 or 4, characterized in that the guide device (31) comprises a frame (34) in which are housed carrier balls (35) and / or a self-lubricating pad.

6. Sector (6) according to one of the preceding claims, characterized in that the root (13) of the blade (9) is held radially in the cavity (15) via several pins (36), each pin (36) being partly housed in a hole (37) of the root (13) and partly housed in a groove (38) of the cavity (15).

7. Sector (6) according to one of the preceding claims, characterized in that the sector (6) comprises several blades (9) which each connect the external and internal platforms (7, 8), each of the blades (9) being variable-pitch around its axis of rotation (Y).

8. Distributor (4) for a turbine (3) of an aircraft turbomachine (1), the distributor (4) comprising a plurality of sectors (6) according to one of claims 1 to 7, the sectors (6) being placed end to end around the axis (X).

9. Turbine (3) of an aircraft turbomachine (1) comprising a distributor (4) according to claim 8.

10. Aircraft turbomachine (1) comprising a distributor (4) according to claim 8 or a turbine (3) according to claim 9.

11. Method for mounting or maintaining a distributor (4) according to claim 8, the method comprising at least the step of: a1) adjusting the timing of the blades (9) of the sectors (6), so as to homogenize the passage section of the distributor (4) which is defined between the external and internal platforms (7, 8) of the sectors (6).

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