Sector of turbine stator for turbine of aircraft turbomachine

Abstract

Sector (6) for a turbine stator of a turbine of an aircraft turbomachine, the sector (6) comprising an outer platform (7) and an inner platform (8) coaxial along an axis (X), the sector (6) further comprising at least one blade (9) connecting the outer and inner platforms (7, 8) together, characterized in that the blade (9) has a variable pitch about an axis of rotation (Y) of the blade (9), the blade (9) comprises an aerodynamic body (11) delimited radially by a head and a root, the head being arranged with a first functional gap in the opening of the outer platform (7) and the root being arranged with a second functional gap in the cavity of the inner platform (8), the axis of rotation (Y) of the blade (9) being located downstream of the head and root.

Description

Field of the Invention

[0001] The present invention relates to a sector of a turbine stator for a turbine of an aircraft, and more particularly to a turbine stator including such a sector. Background Art

[0002] Generally, a turbine of a turbine engine includes at least one stage, and at least one stage includes a stationary turbine stator having blades and a moving wheel having blades.

[0003] More specifically, the turbine stator includes an outer ring and an inner ring coaxial along an axis X, and the outer ring and the inner ring are connected to each other by an annular row of blades.

[0004] Such a turbine stator is generally sectorized and includes an annular row of sectors arranged end to end around the axis X, and each sector includes, for example, two or three fixed pitch blades.

[0005] The sectorization of the turbine stator necessarily means that there is misalignment (however small) between the sectors around the axis X. Such misalignment can be observed, for example, as a step between two consecutive sectors at the ring.

[0006] Such misalignment means that the channel cross-section of the turbine stator is non-uniform around the axis X, thereby reducing the efficiency of the turbine engine. In addition, the steps generated by this misalignment create disturbances in the flow, which also have a negative impact on the efficiency of the turbine engine.

[0007] To correct or minimize such misalignment, various machining operations can be performed once the turbine stator is installed.

[0008] However, such operations are complex to perform and greatly increase the manufacturing time of the turbine stator, which is not conducive to productivity. It should be noted that the above machining operations are only allowed during the manufacturing process of the engine (in other words, before the engine is put into use).

[0009] In addition, engine manufacturers have noticed that the optimal channel cross-section depends on many parameters (such as the external environment, the number of hours the engine has been running, etc.), and it would be beneficial to be able to adjust this channel cross-section throughout the life of the engine, but this is currently not possible.

[0010] Therefore, an object of the present invention is to provide a simple, effective and economical solution to at least some of the above problems.

[0011] The prior art also includes the document US2009 / 067978A1. Summary of the Invention

[0012] Accordingly, the present invention proposes a sector of a turbine stator for a turbine of an aircraft, the sector comprising an outer platform and an inner platform coaxial along an axis X, the sector further comprising at least one blade connecting the outer platform and the inner platform,

[0013] characterized in that the blade has a variable pitch about a rotational axis Y of the blade, the blade comprising an aerodynamic body radially delimited by a head and a root, the head being arranged in an opening of the outer platform with a first functional clearance, the root being arranged in a cavity of the inner platform with a second functional clearance, and the rotational axis Y of the blade being located downstream of the head and the root.

[0014] By assembling the variable pitch blades to the turbine stator, it is possible to adjust the passage cross-section of the turbine stator by adjusting the pitch of each blade.

[0015] This adjustment enables the passage cross-section of the turbine stator to be homogenized, which is beneficial to the efficiency of the turbine and, more generally, to the efficiency of the turbine engine.

[0016] This adjustment can be carried out at any time during the life of the engine, for example during engine assembly or during engine use.

[0017] Positioning the rotational axis Y in this way generally optimizes the passage cross-section of the turbine stator.

[0018] The sector according to the present invention may comprise one or more of the following features, which may be adopted independently of one another or in combination with one another:

[0019] - The blade is guided to rotate about the rotational axis Y of the blade via a cylindrical portion of the blade inserted into an orifice of the outer platform and a spherical portion of the blade inserted into a housing of the inner platform;

[0020] - The pitch of the blade is adjusted via a control element, the control element being integral with the blade and arranged outside the outer platform, and the control element being guided by a guiding device arranged between the control element and the outer platform;

[0021] - The control element is attached to the outer surface of the head of the blade;

[0022] - The guiding device comprises an armature in which bearing balls and / or self-lubricating pads are accommodated;

[0023] - The root of the blade is radially held in the cavity by a plurality of pins, each pin being partially accommodated in a hole in the root and partially accommodated in a groove in the cavity;

[0024] - The sector comprises a plurality of blades, each blade of the plurality of blades connecting the outer platform and the inner platform, and each blade of the blades having a variable pitch about the rotational axis Y of the blade.

[0025] The present invention also relates to a turbine stator for a turbine of an aircraft turbine, the turbine stator comprising a plurality of sectors as described above, the sectors being arranged end to end about an axis X.

[0026] The present invention also relates to a turbine of an aircraft turbine, the turbine comprising a turbine stator as described above.

[0027] Furthermore, the present invention relates to an aircraft turbine, the aircraft turbine comprising a turbine stator as described above or a turbine as described above.

[0028] Finally, the present invention relates to a method for installing or maintaining a turbine stator as described above, the method comprising at least the following steps:

[0029] a1) Adjusting the pitch of the blades of the sectors so as to equalize the cross-section of the channels of the turbine stator, the channels being defined between the outer platform and the inner platform of the sectors. Description of the Drawings

[0030] The present invention will be better understood and other details, features and advantages thereof will become more apparent by reading the following description given by way of non-limiting example with reference to the accompanying drawings, in which:

[0031] Figure 1 Figure 1 is a partial axial half-section view of a turbine comprising a turbine stator according to the present invention;

[0032] Figure 2 Figure 2 is Figure 1 a detailed perspective view of a sector of the turbine stator shown;

[0033] Figure 3 Figure 3 is Figure 2 a detailed perspective view of the outer platform and the inner platform of the sector shown;

[0034] Figure 4 Figure 4 is Figure 2 a first detail and perspective view of the blades of the sector shown;

[0035] Figure 5 Figure 5 is Figure 2 a second detail and perspective view of the blades of the sector shown;

[0036] Figure 6 Figure 6 is a perspective view showing a first step of a method for installing Figure 2 the sector shown;

[0037] Figure 7 Figure 7 ​​​​​​​​​​​​​​is a detailed perspective view of the first step;

[0038] Figure 8 Figure 8 is a perspective view of the second step showing a method for installing the Figure 2 sector shown;

[0039] Figure 9 Figure 9 is a perspective view of the third step showing a method for installing the Figure 2 sector shown;

[0040] Figure 10 Figure 10 is a perspective view of the fourth step showing a method for installing the Figure 2 sector shown;

[0041] Figure 11 Figure 11 is a perspective view of the fifth step showing a method for installing the Figure 2 sector shown;

[0042] Figure 12 Figure 12 is the first detail and perspective view of the fifth step;

[0043] Figure 13 Figure 13 is the second detail and perspective view of the fifth step;

[0044] Figure 14 Figure 14 is a top view showing the steps of a method for installing or maintaining a turbine stator according to the present invention;

[0045] Figure 15 Figure 15 is Figure 14 the front view of the step shown. DETAILED DESCRIPTION

[0046] Figure 1 shows a part of an aircraft turbine 1, which is, for example, a turbojet engine, a turboprop engine or a turboshaft engine.

[0047] The turbine 1 generally includes at least one compressor, a combustion chamber 2 and at least one turbine 3 from upstream to downstream in the air flow direction.

[0048] In Figure 1 ​​​​​​​​​​​​​​​​In the embodiment shown, the turbine 1 includes a high-pressure turbine 3 arranged immediately 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 includes a single high-pressure stage, and the single high-pressure stage includes a turbine stator 4 and a moving wheel 5. The turbine stator 4 is located immediately downstream of the combustion chamber 2, and the wheel 5 is located immediately downstream of the turbine stator 4. The wheel 5 can rotate about the longitudinal axis X of the turbine 1.

[0049] The turbine stator 4 is annular and sectorized, and thus includes a plurality of sectors 6 arranged end to end about the axis X. The turbine stator 4 and the sectors 6 of the turbine stator 4 are also defined along the axis X. Each sector 6 includes an outer platform 7 and an inner platform 8 coaxial along the axis X. The sector 6 also includes at least one vane 9 connecting the outer platform 7 and the inner platform 8.

[0050] According to the invention, the at least one vane 9 of the sector 6 has a variable pitch about the rotation axis Y of the vane 9. The vane 9 includes an aerodynamic body 11 radially bounded by a head 12 and a root 13. The head 12 is arranged in an opening 14 of the outer platform 7 with a first functional clearance. The root 13 is arranged in a cavity 15 of the inner platform 8 with a second functional clearance. The rotation axis Y of the vane 9 is located downstream of the head 12 and the root 13.

[0051] Of course, the sector 6 can include a plurality of vanes 9 (for example, two or three), each vane 9 connecting the outer platform 7 and the inner platform 8, and each vane 9 having a variable pitch about its rotation axis Y.

[0052] By assembling variable-pitch vanes to the turbine stator, it is possible to adjust the channel cross-section of the turbine stator by adjusting the pitch of each vane.

[0053] This adjustment enables the channel cross-section of the turbine stator to be homogenized, which is beneficial to the efficiency of the turbine and, more generally, to the efficiency of the turbine 1.

[0054] This adjustment can be carried out at any time during the life of the motor, for example, during the assembly of the motor or during the use of the motor.

[0055] This positioning of the rotation axis Y generally enables the channel cross-section of the turbine stator to be optimized.

[0056] The example shown is in no way limiting, and the turbine stator 4 (or sector 6) according to the invention can be installed in the low-pressure turbine of the turbine 1.

[0057] In accordance with the convention in this application, "axial" or "axially" refers to any direction parallel to the axis X, and "radial" or "radially" refers to any direction perpendicular to the axis X.

[0058] In addition, in accordance with the convention in the present application, the terms "inner" and "outer" are defined radially with respect to the axis X.

[0059] The outer platform 7 and the inner platform 8 define a duct 10 into which the gases resulting from the combustion of the air / fuel mixture flow. In accordance with the convention, in the present application, the terms "upstream" and "downstream" are defined with respect to the direction of flow of the gases in the turbine 1.

[0060] As shown in the figure, the outer platform 7 and the inner platform 8 each have the form of an arc around the axis X. Each sector 6 includes two variable pitch blades 9, each blade 9 being adjustable about its axis of rotation Y. The axis of rotation Y of the blade is substantially radial. The pitch of the blade 9 is generally quantified by the pitch angle. The adjustment of the pitch of the blade 9 can be independent or common, in other words, the blades 9 can be adjusted independently of each other or jointly. The pitch of the blade 9 can be adjusted manually or automatically. In the case of automatic adjustment, the turbine stator 4 includes control means which include, for example, one or more actuators and one or more mechanisms which connect the one or more actuators to the blade 9. The pitch of the blade 9 is adjusted when the engine is in the stopped state, for example during installation or maintenance.

[0061] As described above, each blade 9 includes an aerodynamic body 11 radially delimited by a head 12 and a root 13. The head 12 is arranged in the opening 14 of the outer platform 7 with a first functional clearance, and the root 13 is arranged in the cavity 15 of the inner platform 8 with a second functional clearance. The first functional clearance and the second functional clearance are positive, and the dimensions of the first functional clearance and the second functional clearance are designed such that the pitch can be adjusted within a predetermined range (for example, plus or minus five degrees with respect to a reference position).

[0062] As described above, the axis of rotation Y of each blade 9 is located downstream of its head 12 and root 13.

[0063] As Figure 4 and Figure 5 shown, the body 11 of each blade 9 is laterally delimited 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 edge 16 and the trailing edge 17 are connected to each other by the pressure side 18 and the suction side 19 of the body 11, the pressure side 18 and the suction side 19 being curved and concave and convex respectively.

[0064] The head 12 of each blade 9 has a shape or profile similar to that of the body 11, with reduced dimensional characteristics. The head 12 extends radially in a straight line with the body 11 and is surrounded by a shoulder 20. Each opening 14 in the outer platform 7 is continuous and has a shape or profile similar to that of the head 12, with increased dimensional characteristics.

[0065] The root 13 of each blade 9 has an outer shape or profile similar to that of the main body 11, with reduced dimensional characteristics. The root 13 extends radially in a straight line with the main body 11 and is surrounded by a shoulder 21. Each cavity 15 of the inner platform 8 is blind and has an outer shape or profile similar to that of the root 13, with increased dimensional characteristics.

[0066] As shown, in particular Figure 4 、 Figure 5 、 Figure 11 and Figure 14 shown, in order to cope with the high temperature in the surrounding space, each blade 9 is hollow and includes two inner chambers 22 separated by a partition 23. These chambers 22 are supplied with an air flow that bypasses the combustion chamber 2, and this air flow discharges from the chambers 22 through perforations 24 formed in the main body 11 of the blade 9 to join the gas flow flowing in the duct 10. In order to optimize the air flow distribution, a perforated sheath 25 ( Figure 14 ) is assembled in each chamber 22.

[0067] Advantageously, each blade 9 is guided to rotate about the rotation axis Y of the blade via a cylindrical portion 26 inserted into an orifice 27 of the outer platform 7 of the blade 9 and a spherical portion 28 inserted into a housing 29 of the inner platform 8 of the blade 9. The cylindrical portion 26 and the spherical portion 28 define the rotation axis Y of the blade 9.

[0068] The spherical portion ensures the guidance while providing the additional degrees of freedom required to cope with the deformation caused by thermal expansion, so as to prevent the blade 9 from getting stuck during rotation.

[0069] As Figure 4 and Figure 5 shown, the cylindrical portion 26 is located immediately downstream of the head 12 and protrudes outward from the main body 11. The spherical portion 28 is located immediately downstream of the root 13 and protrudes inward from the main body 11.

[0070] A bearing can be inserted between the cylindrical portion 26 and the orifice 27 to optimize the rotational guidance of the blade 9. Similarly, a bearing can be inserted between the spherical portion 28 and the housing 29. Advantageously, the pitch of each blade 9 is adjusted by a control element 30 that is integral with the blade 9 and is arranged outside the outer platform 7. The control element 30 is guided by a guiding device 31 arranged between the control element 30 and the outer platform 7.

[0071] Advantageously, the guiding device 31 includes an armature 34, in which bearing balls 35 and / or self-lubricating pads are accommodated. The self-lubricating pads are made of, for example, sintered metal (such as bronze) and include pores doped with a lubricant (such as oil).

[0072] As shown in the figure, the control element 30 is in the form of a flange 30, the outer shape or contour of which is similar to the outer shape or contour of the head 12 (or the opening 14). The flange 30 is attached, for example, by brazing to the free outer surface 32 of the head 12 of the vane 9. The flange 30 is perforated to enable air to be supplied to the inner cavity 22. The flange 30 includes fingers 33 which can be used as a handle when the adjustment is manual and independent, and can be used as a connection interface when the adjustment is common and carried out by a control device.

[0073] As shown in the figure, the guiding device 31 is adjacent to the opening 14 and includes an armature 34 in which bearing balls 35 are received. The bearing balls 35 are evenly distributed in the armature 34 so as to guide the flange 30 in a uniform manner. The guiding device 31 is attached to the outer platform 7 and is inserted between the flange 30 and the outer platform 7. Attaching the flange 30 ensures that the vane 9 is radially held relative to the outer platform 7.

[0074] Advantageously, the root 13 of each vane 9 is radially held in the corresponding cavity 15 by a plurality of pins 36, each pin 36 being partially received in a hole 37 in the root 13 and partially received in a groove 38 in the cavity 15.

[0075] As shown in the figure, in particular as Figures 11 to 13 shown, the root 13 of each vane 9 is radially held in the corresponding cavity 15 by three distributed pins 36 (i.e., a first pin 36 at the leading edge 16, a second pin 36 at the pressure side 18, and a third pin 36 at the suction side 19). The pins 36 are inserted through the inner cavity 22 and are attached to the vane 9, for example, by brazing. The groove 38 formed in the cavity 15 is elliptical, and the size of the groove 38 is designed such that the pitch can be adjusted within a predetermined range (e.g., plus or minus five degrees relative to a reference position). As Figure 1 shown, the outer platform 7 of each sector 6 includes an upstream sealing system 39 and a downstream sealing system 41, the upstream sealing system 39 being configured to axially abut the outer wall 40 of the combustion chamber 2, and the downstream sealing system 41 being configured to axially abut the turbine housing 42. The inner platform 8 of each sector 6 includes an upstream sealing system 43 and two attachment lugs 45, the upstream sealing system 43 being configured to axially abut the inner wall 44 of the combustion chamber 2, and the two attachment lugs 45 being configured to be fixed to the housing 46 surrounding the combustion chamber 2.

[0076] The turbine stator 4 further includes one or more sealing plates (not shown) between two directly adjacent sectors 6 at the outer platform 7 and the inner platform 8 to minimize leakage between the sectors.

[0077] For clarity, the various sealing systems 39, 41 and 43 are not shown in Figures 2 to 15 the figure.

[0078] The outer platform 7 and the inner platform 8 of the vane 9 or the sector 6 have complex shapes, and these components can be manufactured, for example, using an additive manufacturing method (such as selective melting on a powder bed) or using a lost wax casting method. The sector 6 as shown and described above is installed by an installation method including the following steps:

[0079] a) For each vane 9, bring the guiding device 31 to the outer platform 7; ( Figure 6 and Figure 7 )

[0080] b) For each vane 9, arrange the head 12 of the vane 9 together in the opening 14 of the outer platform 7 and arrange the associated cylindrical part 26 in the orifice 27 of the outer platform 7; ( Figure 8 )

[0081] c) For each vane 9, attach the flange 30 to the outer surface 32 of the head 12 of the vane 9; ( Figure 9 )

[0082] d) Arrange the root 13 of the vane 9 together in the cavity 15 of the inner platform 8 and arrange the associated spherical part 28 in the housing 29 of the inner platform 8; ( Figure 10 )

[0083] e) For each vane 9, insert each of the three pins 36 into the hole 37 in the root 13 of the vane 9 and into the associated groove 38; ( Figures 11 to 13 )

[0084] f) For each vane 9, attach the three pins 36 to the vane 9;

[0085] g) Install the upstream sealing system 39 and the downstream sealing system 41 on the outer platform 7, and install the upstream sealing system 43 on the inner platform 8.

[0086] Step a) can be carried out by brazing or welding the armature 34 to the outer platform 7.

[0087] Step c) can be carried out by brazing or welding the flange 30 to the head 12 of the vane 9.

[0088] In step e), the pin 36 is inserted through the inner chamber 22.

[0089] Step f) can be carried out by brazing or welding the pin 36 to the inner surface defining the chamber 22, and the brazing or welding is carried out in the inner chamber 22.

[0090] The turbine stator 4 as described above is installed by an installation method including at least the following steps:

[0091] a1) Adjust the pitch of the blades 9 of sector 6 to equalize the cross-section of the channels of the turbine stator 4, which channels are defined between the outer platform 7 and the inner platform 8 of sector 6( Figure 14 and Figure 15 ).

[0092] Prior to step a1), the sectors 6 of the turbine stator 4 may be arranged end-to-end about the axis X.

[0093] As Figure 14 shown by the arrow in, in step a1), the fingers 33 of each blade 9 are actuated in a tangential or circumferential direction (in either direction) to adjust the pitch of the blade 9.

[0094] The turbine stator 4 as described above is maintained by a maintenance method comprising at least the following steps:

[0095] a1) Adjust the pitch of the blades 9 of sector 6 to equalize the cross-section of the channels of the turbine stator 4, which channels are defined between the outer platform 7 and the inner platform 8 of sector 6( Figure 14 and Figure 15 ).

[0096] As Figure 14 shown by the arrow in, in step a1), the fingers 33 of each blade 9 are actuated in a tangential or circumferential direction (in either direction) to adjust the pitch of the blade 9.

[0097] For the sake of clarity, Figure 14 and Figure 15 only one sector 6 of the turbine stator 4 is shown.

Claims

1. A sector (6) of a turbine stator (4) of a turbine (3) for an aircraft turbine (1), the sector (6) comprising an outer platform (7) and an inner platform (8) coaxial along an axis (X), the sector (6) further comprising at least one blade (9) connecting the outer platform and the inner platform (7, 8). Characterized in that, the blade (9) has a variable pitch about the axis of rotation (Y) of the blade (9), the blade (9) comprising an aerodynamic body (11) radially delimited by a head (12) and a root (13), the head (12) being arranged in an opening (14) in the outer platform (7) with a first functional clearance, the root (13) being arranged in a cavity (15) in the inner platform (8) with a second functional clearance, and the axis of rotation (Y) of the blade (9) being located downstream of the head (12) and the root (13).

2. The sector (6) according to claim 1, Characterized in that, the blade (9) is guided to rotate about the axis of rotation (Y) of the blade via a cylindrical part (26) of the blade (9) inserted into an orifice (27) of the outer platform (7) and a spherical part (28) of the blade (9) inserted into a housing (29) of the inner platform (8).

3. The sector (6) according to any one of the preceding claims, Characterized in that, the pitch of the blade (9) is adjusted via a control element (30), the control element being integral with the blade (9) and arranged outside the outer platform (7), and the control element (30) being guided by a guiding device (31) arranged between the control element (30) and the outer platform (7).

4. The sector (6) according to claim 3, Characterized in that, the control element (30) is attached to the outer surface (32) of the head (12) of the blade (9).

5. The sector (6) according to claim 3 or 4, Characterized in that, the guiding device (31) comprises an armature (34) in which bearing balls (35) and / or self-lubricating pads are received.

6. The sector (6) according to any one of the preceding claims, Characterized in that, the root (13) of the blade (9) is radially held in the cavity (15) by a plurality of pins (36), each pin (36) being partially received in a hole (37) in the root (13) and partially received in a groove (38) in the cavity (15).

7. The sector (6) according to any one of the preceding claims, Characterized in that, the sector (6) comprises a plurality of blades (9), each blade of the plurality of blades connecting the outer platform and the inner platform (7, 8), and each blade (9) having a variable pitch about the axis of rotation (Y) of the blade.

8. A turbine stator (4) for a turbine (3) of an aircraft turbine (1), the turbine stator (4) comprising a plurality of sectors (6) according to any one of claims 1 to 7, the sectors (6) being arranged end-to-end around the axis (X).

9. A turbine (3) of an aircraft turbine (1), the turbine comprising a turbine stator (4) according to claim 8.

10. An aircraft turbine (1), the aircraft turbine comprising a turbine stator (4) according to claim 8 or a turbine (3) according to claim 9.

11. A method for installing or maintaining a turbine stator (4), the turbine stator being the turbine stator according to claim 8, the method at least comprising the following steps: a1) Adjusting the pitch of the blades (9) of the sectors (6) to equalize the cross-section of the channels of the turbine stator (4), the channels being defined between the outer platform and the inner platforms (7, 8) of the sectors (6).

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