VARIABLE PITCHING TURBONE STAGE FOR AN AIRCRAFT TURBOMACHINE
The solution of incorporating flat surfaces on the second cylindrical pivots addresses the interference issue in variable-pitch blade assembly, enhancing assembly efficiency and reducing costs and environmental footprint.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2024-05-06
- Publication Date
- 2026-05-15
AI Technical Summary
The mounting of annular parts around the second cylindrical pivots in variable-pitch blades is complicated by interference, leading to wear and damage, which affects the operability and performance of the turbomachine.
The second cylindrical pivots are designed with flat surfaces oriented parallel to the longitudinal axis, providing sufficient mounting clearance to prevent interference between the pivots and annular parts, facilitating secure and efficient assembly.
This design ensures secure and efficient assembly of the annular parts, reducing assembly time and costs while minimizing part damage and environmental impact.
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Abstract
Description
Title of the invention: VARIABLE PITCH BATTERY STAGE FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention
[0001] The present invention relates to the field of aircraft turbomachinery and, in particular, to a variable-pitch blade stage of such turbomachinery. Technical background
[0002] In an aircraft turbomachine, a variable-pitch blade stage is mounted, for example, between the rotating wheels of a compressor. These blades can be arranged in an annular row in one or more stages of the turbomachine. The annular row of variable-pitch blades extends around a longitudinal axis that may be substantially parallel to an axis of the turbomachine.
[0003] These blades (also called rectifier blades or the English acronym VSV for "Variable Sator Varies") are carried by an external annular housing and are adjustable in position around their axes of rotation (or otherwise called pitching axis) to optimize the flow of gases in the turbomachine engine.
[0004] Each blade comprises a blade having a first cylindrical pivot at its radially external end and a second cylindrical pivot at its radially internal end. These first and second cylindrical pivots define a pitching axis (or, in other words, an axis of rotation) of the blade. The second cylindrical pivot is mounted in a corresponding housing of a ring (or, in other words, an annular ferrule).
[0005] The angular pitch of these blades is intended to adapt the geometry of a turbomachine compressor to its operating point. The angular pitch also optimizes the compressor efficiency as a function of aircraft speed and optimizes the turbomachine's pumping margin to reduce fuel consumption during different phases of flight.
[0006] Each of these blades is movable in rotation around its axis of adjustment between a first "open" or "fully open" position in which each blade extends substantially parallel to a longitudinal axis of the turbomachine, and a second "closed" or "quasi-closed" position in which the blades are inclined with respect to the axis of the turbomachine and thus reduce the cross-section of the air passage through the blade stage.
[0007] The pitch axis of these blades is generally perpendicular to the longitudinal axis of the turbomachine. Under certain aerodynamic conditions, this pitch axis may be inclined with respect to a plane perpendicular to the longitudinal axis.
[0008] Fig. 1 schematically illustrates a part of the stage 1 of variable pitch blades comprising the second cylindrical pivot 24 which is mounted in the corresponding housing 40 of the ring 4. This ring 4 is formed by the assembly of two annular parts, respectively upstream 42 and downstream 44, which are applied axially to each other so that the second cylindrical pivot 24 is interposed between these annular parts 42, 44. The pitch axis D of this blade 2 (and consequently the second cylindrical pivot 24) is inclined with respect to an axis P (or a plane) perpendicular to the longitudinal axis of the turbomachine.
[0009] Generally, the ring is mounted around the second cylindrical pivot of each of the variable-pitch blades. However, the inclination of the pitch axis D relative to the perpendicular axis P can complicate the mounting of the annular parts around the second cylindrical pivots. Indeed, in this configuration, mounting interference between the second cylindrical pivots and the annular parts of the ring could occur.
[0010] "Interference" means wear friction generated on an external cylindrical surface of the second pivot and / or on an internal surface of the ring mounting housing during the mounting of the ring around the second cylindrical pivots.
[0011] Figures 2a and 2b schematically illustrate the interferences I generated during the mounting of the annular parts 42, 44 around the second cylindrical pivot 24. Figures 3a and 3b schematically illustrate the second cylindrical pivot 24 mounted in the mounting housing 40 of the ring.
[0012] In this example of Figures 1 to 3b, the blade pitch axis D is therefore inclined with respect to the perpendicular axis P. The mounting housing 40 for the second cylindrical pivot 24 is open onto the upstream annular part 42 and closes onto the downstream annular part 44 along a first axial section plane AA ([Fig. 2a] and [Fig. 3a]). This mounting housing 40 for the second cylindrical pivot 24 closes onto the upstream annular part 42 and is open onto the downstream annular part 44 along a second axial section plane BB ([Fig. 2b] and [Fig. 3b]). The first axial section plane is located above the second axial section plane in Figures 1 to 3b. These interferences may make mounting the second blade pivot impossible, and they may also limit the operability and performance of the variable-pitch blades and, more generally, of the turbomachine.
[0013] In this context, it is interesting to overcome the disadvantages of the prior art, by proposing a secure solution that limits mounting interference between a ring and a cylindrical pivot of a variable pitch blade. Summary of the invention
[0014] The present invention proposes a simple, effective and economical solution to at least some of the aforementioned problems.
[0015] To this end, the invention relates to a variable-pitch blade stage for an aircraft turbomachine, this stage comprising: - an annular row of variable-pitch blades extending around a longitudinal axis X, each blade comprising a blade having a first cylindrical pivot at its radially external end and a second cylindrical pivot at its radially internal end, the first and second cylindrical pivots defining a pitch axis D of the blade, and - a ring which extends around the longitudinal axis X and which has mounting housings for said second cylindrical pivots, this ring being formed by the assembly of two annular pieces, respectively upstream and downstream, which are applied axially to each other so that the second cylindrical pivots are interposed between the two annular pieces, said housings having first parts formed in the upstream annular piece and second parts formed in the downstream annular piece.
[0016] According to the invention, said second cylindrical pivots have flats which are oriented parallel to said longitudinal axis X, said flats being configured for mounting the second cylindrical pivots between the two annular pieces.
[0017] Thus, this solution makes it possible to achieve the aforementioned objective. Indeed, the flat surfaces according to the invention allow for the formation of flat surfaces on the second cylindrical pivots, so as to create sufficient mounting clearance between these second cylindrical pivots and the two annular parts. This mounting clearance prevents interference and therefore any contact between the second cylindrical pivots and the two annular parts. In this way, the mounting of the two annular parts around the second cylindrical pivots is secure and facilitated, without damage to the two annular parts and / or the second cylindrical pivots. Furthermore, the flat surfaces can be easily produced, for example, by milling, turning, or grinding.
[0018] By improving the precision and ease of assembly of the two annular parts around the second cylindrical pivots, the flats according to the invention can help reduce the assembly time of the variable-pitch blade stage and production and assembly costs, by minimizing scrap from parts worn by interference during assembly operations. This also helps to reduce the Applicant's environmental footprint.
[0019] The invention therefore has the advantage of being based on a simple design, offering very high reliability (in particular a secure and simple mounting of the second cylindrical pivots between the two annular pieces), and little penalizing in terms of cost and size.
[0020] The blade stage according to the invention may comprise one or more of the following features, taken individually or in combination with each other:
[0021] - each of the second cylindrical pivots includes at least one of the flats;
[0022] - each of the second cylindrical pivots comprises two substantially flat surfaces diametrically opposed with respect to the alignment axis D;
[0023] - each flat surface extends over at least part of an external cylindrical surface of the second cylindrical pivot;
[0024] - each flat surface extends over at least eighty percent of a length of the second cylindrical pivot, measured along the alignment axis D;
[0025] - the second cylindrical pivots are formed in one piece with the blades of the variable pitch blades;
[0026] - the second cylindrical pivots comprise fingers formed in one piece with the blades of the vanes, as well as cylindrical bushings attached to the fingers, the flats being formed on these bushings;
[0027] - the housings are cylindrical and gaps are provided between the flats and the housing;
[0028] - the alignment axes D are inclined with respect to axes P perpendicular to the axis longitudinal X, with angles greater than or equal to five degrees;
[0029] — the first pivots are non-cylindrical or substantially cylindrical;
[0030] — the second pivots are non-cylindrical or substantially cylindrical.
[0031] The present invention may also relate to an aircraft turbomachine comprising at least one stage of variable-pitch blades according to one of the features described above.
[0032] The turbomachine can be a turbojet, a turbomotor or a turboprop.
[0033] The variable pitch blade stage can be located in a low pressure or high pressure compressor of the turbomachine. Brief description of the figures
[0034] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:
[0035] [Fig. 1] is a partial schematic axial cross-sectional view of a variable-pitch blade stage according to the prior art and comprising a cylindrical pivot of the variable-pitch blade mounted in a ring,
[0036] [Fig.2a] is a schematic view along an axial section plane AA during the mounting of the ring around the cylindrical pivot of [Fig.l],
[0037] [Fig.2b] is a schematic view along another axial section plane BB during the mounting of the ring around the cylindrical pivot of [Fig.l],
[0038] [Fig.3a] is a schematic view along the axial cutting plane AA after the ring has been mounted around the cylindrical pivot of [Fig.2a],
[0039] [Fig.3b] is a schematic view along section plane BB after the ring has been mounted around the cylindrical pivot of [Fig.2b],
[0040] [Fig.4] is a schematic axial and partial cross-sectional view of an aircraft turbomachine comprising at least one stage of variable-pitch blades according to the invention,
[0041] [Fig.5] is a schematic axial cross-sectional view of the variable pitch blade stage of [Fig.4],
[0042] [Fig. 6a] is a schematic view along the axial cutting plane AA during the mounting of a ring of the stage of [Fig. 4] around a first example of a cylindrical pivot having flats,
[0043] [Fig.6b] is a schematic view along the axial cutting plane AA after the ring has been mounted around the cylindrical pivot of [Fig.6a],
[0044] [Fig.7] is a schematic view along the axial section plane AA after mounting the ring of the stage of [Fig.5] mounted around a second example of a cylindrical pivot having flats formed on a cylindrical sleeve attached to the cylindrical pivot.
[0045] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention
[0046] By convention in this application, the terms "inside" and "outside," and "internal" and "external," are defined radially with respect to a longitudinal axis (which may correspond to a longitudinal X-axis of a turbomachine). Thus, a cylinder extending along this longitudinal axis has an inner face facing the engine axis and an outer surface opposite its inner surface. "Axial" or "axially" means any direction parallel to this longitudinal axis, and "transversely" or "transverse" means any direction perpendicular to this longitudinal axis. Similarly, the terms "upstream" and "downstream" are defined with respect to the direction of airflow in the turbomachine, which is represented by an arrow F.
[0047] Figures 1, 2a, 2b, 3a and 3b have been described in the technical background of this application and illustrate an example of a variable pitch blade stage according to the prior art.
[0048] The invention applies in a non-limiting way to an aircraft turbomachine 100, such as a turbojet, a turbomotor or a turboprop.
[0049] Fig. 4 partially illustrates an example of this turbomachine 100.
[0050] The turbomachine 100 can extend along a longitudinal X axis.
[0051] The turbomachine 100 may include, from upstream to downstream, a blower, at least a compressor (such as a low pressure compressor 10 and a high pressure compressor 12), a combustion chamber 14, at least one turbine 16 (such as a high pressure turbine and a low pressure turbine), and possibly a gas exhaust nozzle.
[0052] The turbomachine 100 may include at least one stage 1 of variable-pitch blades 2 (or, in other words, blades fixed with respect to the X-axis). In particular, the low-pressure compressor 10 and / or the high-pressure compressor 12 may include at least one or more stages 1 of variable-pitch blades 2. The angular orientation of the blades 2 can thus be adjusted to optimize the gas flow in the compressor.
[0053] Stage 1 may include an annular row of movable blades 3 (with respect to the X-axis) carried by a turbomachine rotor. The annular row of movable blades 3 may be arranged upstream of the annular row of variable-pitch blades 2.
[0054] Stage 1 according to the invention is described in a non-limiting manner with reference to Figures 4 to 7.
[0055] Figure 5 partially illustrates a non-limiting example of the low-pressure compressor 10 (or possibly the high-pressure compressor 12) comprising stage 1. This stage 1 comprises: - the annular row of 2 variable-pitch blades extending around the longitudinal axis X, and - a ring 4 which extends around the longitudinal axis X.
[0056] The blades 2 can be carried by an annular housing 5 of the turbomachine stator. Thus, the blades 2 can extend between the housing 5, which is arranged radially outwards (with respect to the X axis), and the ring 4, which is arranged radially inwards.
[0057] Each blade 2 comprises a blade 20 having a first cylindrical pivot 22 at its radially external end and a second cylindrical pivot 24 at its radially internal end (with respect to the X axis).
[0058] The radially external end of the blade 20 can correspond (or can be connected) to a heel of the blade 2. The first pivot 22 can be located on the heel of the blades 2.
[0059] The radially inner end of the blade 20 can correspond to (or can be connected to) a blade root. The second pivot 24 can be located on the blade root 2.
[0060] The first pivots 22 may be non-cylindrical or substantially cylindrical. The second pivots 24 may be non-cylindrical or substantially cylindrical.
[0061] The first 22 and second 24 cylindrical pivots define a pitching axis D of the blade 2.
[0062] The alignment axes D can be inclined with respect to axes perpendicular P to the X axis, with angles a. These angles a can each be greater than or equal to five degrees (i.e. 5°).
[0063] Each first cylindrical pivot 22 can be engaged in a first housing 50 of a chimney 52 of the housing 5, and can be centered and guided in rotation in this chimney 52 by cylindrical rings 54 mounted around the first cylindrical pivot 22.
[0064] Each first cylindrical pivot 22 may have a radially external end 220 which is fixed, for example, by means of a nut 222 to a control lever 60. Each lever 60 connects the first cylindrical pivots 22 to a control ring 6 which also extends around the axis X and outside the housing 5. An angular displacement of the control ring 6 around the axis X results in a rotation of the levers 60 around the shim axis D and in the rotation of the blades 2 around this axis D.
[0065] The second cylindrical pivots 24 can be formed from a single piece (i.e. from a single piece of material) with the blades 20 of the variable-setting vanes 2.
[0066] The second cylindrical pivots 24 can be engaged in second housings 40 of the ring 4.
[0067] The second cylindrical pivots 24 may include fingers 242 formed in one piece with the blades 20 of the vanes 2.
[0068] The second cylindrical pivots 24 may include cylindrical bushings 244 attached to the fingers 242.
[0069] The ring 4 therefore includes the second housings 40 for mounting the second cylindrical pivots 24.
[0070] The second housings 40 can be cylindrical or substantially cylindrical.
[0071] The ring 4 is formed by the assembly of two annular pieces, respectively upstream 42 and downstream 44, which are applied axially to each other so that the second cylindrical pivots 24 are interposed between the two annular pieces 42, 44.
[0072] The second housings 40 comprise first parts formed in the upstream annular piece 42 and second parts formed in the downstream annular piece 44. According to the section plane AA or BB, these first and second parts of the second housings 40 can be open or closed on the upstream annular piece 42 or downstream annular piece 44. For example, Figures 6a, 6b and 7 illustrate first parts of the second housings closing on the upstream annular piece 42 and second parts of these second housings 40 opening on the downstream annular piece 44.
[0073] One of the features of the invention is that the second cylindrical pivots 22 have flats 240. These flats 240 are oriented parallel to the X axis and configured to facilitate their assembly between the two annular pieces 42, 44.
[0074] The flats 240 can be formed directly on the fingers 242 of the second cylindrical pivots 24 ([Fig.6a] and [Fig.6b]) in particular when the bushings 244 are not mounted around the second cylindrical pivots 24. Alternatively, the flats 240 can be formed on the bushings 244 ([Fig.5] and [Fig.7]) when they are mounted around the fingers 242 in the second housings 40.
[0075] Each of the second cylindrical pivots 24 can include at least one flat 240.
[0076] Each of the second cylindrical pivots 24 can include two flats 240 diametrically opposed with respect to the alignment axis D.
[0077] The flat or each flat 240 can extend over at least a part of an external cylindrical surface of the second cylindrical pivot 24.
[0078] The flat or each flat 240 can extend over at least eighty percent (i.e. 80%) of a length of the second cylindrical pivot 24, measured along the alignment axis D. Advantageously, the flat or each flat 240 can extend over the entire length of the second cylindrical pivot 24.
[0079] Stage 1 may include mounting gaps J between the flats 240 and the second housings 40.
[0080] The present invention will now describe the various non-limiting possibilities of arrangement of the flats 240 on the second cylindrical pivots 24 with reference to figures 6a, 6b and 7.
[0081] Figures 6a and 6b schematically and partially illustrate a first example of an embodiment of stage 1 according to the invention and described above in particular with reference to figures 4 and 5.
[0082] Stage 1 according to the first example thus comprises the annular row of blades 2, the ring 4, and the second cylindrical pivots 24 with the flats 240 oriented parallel to the X-axis. These flats 240 are formed directly on the second cylindrical pivots 24. In particular, the flats 240 can be formed directly on the fingers 242 of the second cylindrical pivots in the absence of bushings 244 mounted around these second cylindrical pivots 24. Furthermore, the second cylindrical pivot 24 has two flats 240 diametrically opposed with respect to the alignment axis D. In addition, gaps J are provided between the flats 240 and the two annular pieces 42, 44 at the level of the second housing 40.
[0083] On [Fig.6a], the arrow indicates the direction of assembly of the annular parts 42, 44 with each other.
[0084] Fig. 7 schematically and partially illustrates a second example of the embodiment of stage 1 according to the invention.
[0085] Stage 1 of the second example differs from that of the first example by the presence of bushings 244 attached to the fingers 242 of the second cylindrical pivots 24, and the flats 240 being formed on these bushings 244.
Claims
Demands
1. A variable-pitch turbine blade stage (1) for an aircraft turbomachine (100), said stage (1) comprising: - an annular row of variable-pitch turbine blades (2) extending about a longitudinal axis (X), each blade (2) having a blade (20) having a first cylindrical pivot (22) at its radially external end and a second cylindrical pivot (24) at its radially internal end, the first and second cylindrical pivots (22, 24) defining a pitch axis (D) of the blade (2), and - a ring (4) extending about the longitudinal axis (X) and having mounting housings (40) for said second cylindrical pivots (24), this ring (4) being formed by the assembly of two annular pieces, respectively upstream (42) and downstream (44), which are axially applied to each other such that the second cylindrical pivots (24) are intercalated between the two annular pieces (42, 44),said housings (40) comprising first parts formed in the upstream annular piece (42) and second parts formed in the downstream annular piece (44), characterized in that said second cylindrical pivots (24) comprise flats (240) which are oriented parallel to said longitudinal axis (X), said flats (240) being configured for mounting the second cylindrical pivots (24) between the two annular pieces (42, 44).
2. Blade stage according to claim 1, characterized in that each of the second cylindrical pivots (24) comprises at least one of the flats (240).
3. Blade stage according to claim 1 or 2, characterized in that each of the second cylindrical pivots (24) comprises two flats (240) substantially diametrically opposed with respect to the alignment axis (D).
4. Blade stage according to any one of the preceding claims, characterized in that each flat (240) extends over at least a part of an external cylindrical surface (24a) of the second cylindrical pivot (24).
5. A blade stage according to any one of the preceding claims, characterized in that each flat (240) extends over at least eighty percent of a length of the second cylindrical pivot (24), measured along the shimming axis (D).
6. Blade stage according to any one of the preceding claims, characterized in that the second cylindrical pivots (24) are formed in one piece with the blades (20) of the variable pitch blades (2).
7. Blade stage according to any one of the preceding claims, characterized in that the second cylindrical pivots (24) comprise fingers (242) formed in one piece with the blades (20) of the blades (2), as well as cylindrical bushings (244) attached to the fingers (242), the flats (240) being formed on these bushings (244).
8. Blade stage according to any one of the preceding claims, characterized in that the housings (40) are cylindrical and gaps (J) are provided between the flats (240) and the housings (40).
9. Blade stage according to any one of the preceding claims, characterized in that the pitch axes (D) are inclined with respect to axes (P) perpendicular to the longitudinal axis (X), with angles (a) greater than or equal to five degrees.
10. Aircraft turbomachine (100) comprising at least one stage (1) of variable-pitch blades according to any one of the preceding claims.