Conical guide assembly for the pivoting of an adjustable blade

Abstract

Conical guide assembly for the pivoting of a blade with adjustable orientation The guide assembly (1) comprises a fixed blade with variable angular orientation (15) of a turbomachine, free to pivot about a radial axis Y and comprising a blade (17) extended radially in the lower part by a guide pivot (20) conical or frustoconical of revolution, with a tapered end (24) directed towards the inside an inner ring (25) of stator, comprising a cavity (27) open towards the outside, of conical or frustoconical shape of revolution complementary to that of the guide pivot, in which the guide pivot is engaged. In normal operating conditions, the guide pivot is preferably at a distance from the wall (28) of the cavity, a free space (29) extending all around, between the guide pivot and the wall of the cavity. Figure to be published with the abstract: Figure 2

Description

Title of the invention: Conical guide assembly for the pivoting of a blade with adjustable orientation TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of aircraft turbomachine compressors.

[0002] The present invention relates to a blade with variable angular orientation for a turbomachine compressor and relates more particularly to an assembly for guiding the pivoting of this blade.

[0003] It also relates to a turbomachine compressor and an associated turbomachine comprising such an assembly for guiding the pivoting of a blade with variable angular orientation. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] Aircraft turbomachines often have variable angle blades, also called adjustable angle blades, variable angle blades, variable pitch blades, pivoting blades or VSV blades (Variable Bleed Valves in English). These blades can pivot around their axis, in order to adjust their angular position (their angle of attack or angle of incidence) relative to the airflow passing through them and thus optimize the airflow in the turbomachine.

[0005] We thus often find stator stages of fixed blades with variable pitch, in the upstream part of high pressure compressors and low pressure compressors of turbomachines, interposed between the moving blade wheels of the rotor stages.

[0006] Such blades are fixed, that is to say they do not rotate around the longitudinal axis of the turbomachine like the blades of the rotor stages, but can be pivoted on themselves during operation of the engine, which makes it possible to optimize their action in real time, depending on the engine speed and the flight conditions and thus to improve the performance of the turbomachine.

[0007] For this purpose, these blades are conventionally extended at their outer end by a radial rod which passes through an opening in the outer casing. Control rods are fixed laterally to the free ends of these radial rods and are connected by their other end to a rotating crown located outside the casing. A servo system, electric, pneumatic or hydraulic, automatically controls the rotation of the crown according to the operating conditions, which causes the pivoting of the rods and thus the modification of the angular position (incidence) of the variable-pitch blades.

[0008] On the internal side, these blades conventionally comprise a guide pivot which radially extends the inner end of the blade. In current technology, this pivot is a cylindrical rod which engages, pivoting, in the central bore of a complementary cylindrical sleeve. This sleeve is fixedly mounted in a recess of an inner ring of the internal casing. Such a guide assembly is for example described in patent FR 2 890 707 B1.

[0009] These prior guide assemblies require several parts to make the connection between the pivot of the blade and the inner ring. Depending on the device used, a bushing and other parts are required, often made in several parts to allow their assembly in the recess of the ring, or screws to retain the pivot and / or assemble the different parts of the inner ring.

[0010] This multiplication of the number of parts has the consequence of increasing the space around the guide pivot and especially the mass of the engine, which is particularly unfavorable in the aeronautical field. In addition, the time required to assemble the assembly is also increased.

[0011] Furthermore, the pivoting of the blade generates friction between the surfaces in contact of the pivot and the bushing, which cause wear over time. Little by little, this wear increases the clearances in the system and causes misalignment of the pivots and more generally of the associated blades, causing a deregulation of the assembly which influences the precision of the adjustment of the angular orientation of the blades and affects the overall performance of the engine.

[0012] An objective of the invention is to propose an alternative guide assembly for the pivoting of variable-pitch blades, usable in a turbomachine compressor, which is at the same time less bulky, lighter, quicker to install and less sensitive to wear. Summary of the invention

[0013] A first aspect of the invention relates to an assembly for guiding the pivoting of a fixed blade with variable angular orientation of an X-axis turbomachine.

[0014] This guide assembly includes: • a fixed blade with variable angular orientation, free to pivot around a radial axis Y perpendicular to and intersecting the axis X, said blade comprising a blade extended radially in the inner part by a guide pivot; and • an inner stator ring, comprising a hollow housing, open towards the outside, in which the blade guide pivot is engaged.

[0015] This guide assembly is characterized in that: • the guide pivot is in the shape of a cone or truncated cone of revolution, with a radial axis Y and with a tapered end directed inwards, • the hollow housing is a conical or truncated cone-shaped cavity of re- evolution, with radial axis Y and a shape complementary to that of the guide pivot, said cavity being delimited by a wall.

[0016] A cone or truncated cone of revolution is a cone or truncated cone with a circular base.

[0017] The expression "tapered end" means that said end gradually tapers towards the tip. This refers to the pointed part of the cone of revolution or the narrowest part of the truncated cone.

[0018] The characteristic that the cavity is of a shape "complementary" to that of the guide pivot means that its shape and dimensions are such that the pivot could be fitted therein to complete it (even if a portion of the cavity would remain empty in the case of a frustoconical pivot in a conical cavity). This means that the wall of the cavity is substantially parallel to the side wall of the pivot or that the angle of the conical or frustoconical cavity is substantially equal to the angle of the apex of the cone or truncated cone formed by the guide pivot.

[0019] A “free space” is an empty volume, that is to say unoccupied.

[0020] The guide assembly according to the invention advantageously comprises fewer parts than those of the prior art. It is thus lighter, less bulky and quicker to assemble. In addition, its assembly by simple engagement of the guide pivot in an open cavity opposite is greatly facilitated.

[0021] Advantageously, in a normal operating situation, the guide pivot is preferably located at a distance from the wall of the cavity in which it is engaged, a free space extending all around the guide pivot, between the guide pivot and the wall of the cavity.

[0022] Thus, since in a normal operating situation the guide pivot is not in contact with the walls of the cavity in which it is engaged, no friction occurs in the guide assembly when the blade pivots on itself. No wear is therefore generated at this level. The guide assembly according to the invention is therefore much less sensitive to wear than those of the prior art.

[0023] Advantageously, the guide pivot may have, at the top of the cone or truncated cone, an angle α of between 10° and 60°.

[0024] Such angular values ​​make it possible to achieve in a particularly satisfactory manner both pivot guidance in a normal operating situation and a safety function in an abnormal operating situation as will be explained below.

[0025] Advantageously, the guide pivot can be integral with the blade, i.e. made from a single piece with the latter. The guide assembly thus comprises fewer parts to be assembled, which makes assembly simpler and faster.

[0026] Alternatively, it may be an independent part, added and fixed to the pale by any appropriate means.

[0027] Advantageously, the wall of the cavity is a single piece, i.e. a single piece for the entire cavity or a single piece over 360°. The cavity is therefore not formed by assembling several cavity portions but is entirely made in the same part of the inner ring, which advantageously limits the number of parts to be used and reduces the assembly time. In addition, the size and weight are also reduced by eliminating the fixing elements.

[0028] Such a configuration is made possible by the particularly advantageous arrangement of the guide assembly according to the invention. Indeed, the conical or truncated pivot of the blade is simply engaged in the cavity of the inner ring, without support or contact between the two parts. Their shapes being complementary, this engagement is done by simply introducing the pivot into the cavity through its opposite opening.

[0029] On the contrary, in prior devices with a cylindrical pivot, the cylindrical pivot must be retained in the housing. The pivot or the socket in which it is engaged then has a shape preventing their removal, which requires opening the housing to be able to mount them.

[0030] A second aspect of the invention relates to a stator stage of an X-axis turbomachine, comprising an inner stator ring and a plurality of fixed blades with variable angular orientation distributed radially around said inner stator ring, which comprises a guide assembly as described previously for each of the fixed blades with variable angular orientation.

[0031] A third aspect of the invention relates to a turbomachine compressor comprising at least one guide assembly as described previously.

[0032] Advantageously, said guide assembly is located in the upstream part of the compressor.

[0033] A fourth aspect of the invention relates to an aircraft turbomachine comprising at least one compressor as described above.

[0034] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0035] The figures are presented for information purposes only and in no way limit the invention.

[0036] [Fig.l] is a sectional view of a portion of a testing machine according to an example of the invention.

[0037] [Fig.2], [Fig.3], [Fig.4] and [Fig.5] are schematic side views of a first example of a guide assembly according to the invention with a conical pivot, respectively at room temperature, expanded at high temperature, with an inclination of the blade and with a lateral offset of the blade.

[0038] [Fig.6] is a schematic side view of a second example of a set of guide according to the invention with truncated conical pivot and conical cavity.

[0039] [Fig.7] is a schematic side view of a third example of a set of guide according to the invention with truncated pivot and truncated cavity. DETAILED DESCRIPTION

[0040] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0041] In the present application, the terms "upstream" and "downstream" are defined with respect to the normal flow direction of gas (from upstream to downstream) through a turbomachine.

[0042] The term "axis of the turbomachine" also refers to the longitudinal axis of the turbomachine, corresponding to the axis of rotation of the rotor of this turbomachine. This axis is referred to as X in the figures. The axial direction corresponds to the direction of this X axis and a radial direction is a direction perpendicular to the X axis and intersecting this axis. For example, the Y axis has a radial direction in normal operating conditions.

[0043] Unless otherwise specified, the adjectives "interior", "internal", "exterior", "external" are used in the present application with reference to a radial direction, so that the interior part of an element is, in a radial direction, closer to the X axis than the exterior part of the same element.

[0044] Furthermore, the expressions "top", "bottom", "upper", "lower" are defined with respect to the orientation of the parts as shown in the figures. It is obvious that this orientation will not necessarily be retained in use.

[0045] Furthermore, the expressions “variable or adjustable (angular) pitch blade”, “variable or adjustable (angular) orientation blade” or “pivoting blade” are synonymous.

[0046] Finally, the expression “ambient temperature” will be understood as designating a temperature substantially equal to 20°C.

[0047] The figures show examples of guide assembly 1 according to the invention. This guide assembly 1 can be installed in an aircraft turbomachine 2.

[0048] An example of a turbomachine 2 has been shown schematically in [Fig. 1]. It is a double-flow turbojet of which only the upper part has been shown.

[0049] This turbomachine 2 with axis X conventionally comprises, from upstream to downstream, a fan 3, a low pressure compressor 4, a high pressure compressor 5, a combustion chamber 6 and a turbine 7.

[0050] Compressors 4 and 5 each comprise a succession of rotor stages 8 and of alternating stator stages 9, which are arranged between an external casing 10 and an internal casing 11.

[0051] Each rotor stage 8 is formed of a crown of moving blades 12 which, in operation, rotate around the longitudinal axis X of the turbomachine.

[0052] On the contrary, each stator stage 9 is formed of a crown of fixed blades 13, which, in operation, do not rotate around the longitudinal axis X of the turbomachine.

[0053] In the upstream part 14 of each of these compressors 4, 5, the fixed blades 13 of the stator stages 9 are preferably fixed blades with variable angular orientation 15, which can pivot radially on themselves to adjust their angular position.

[0054] A guide assembly 1 is advantageously installed for each of these fixed blades with variable angular orientation 15 in order to guide the pivoting of each of these blades.

[0055] Several examples of such a fixed blade with variable angular orientation 15 and its guide assembly 1 have been shown in FIGS. 2 to 7.

[0056] The adjustable orientation blade 15 comprises a body 16 forming a curved blade 17 which extends in a substantially radial general direction.

[0057] In order to be able to adjust its orientation, the blade 15 is mounted free to rotate around a radial Y axis, perpendicular and intersecting the X axis. It is thus capable of pivoting around the Y axis, which modifies the angular position of the blade 17 which can consequently adopt any angular position which can be obtained by a rotation from 0 to 360°.

[0058] For this, the blade 15 comprises a rod 18 of axis Y, preferably cylindrical, which starts from the external end 19 of the blade 17 and extends radially outwards (the top in the figures).

[0059] This rod 18 passes through an opening in the external casing 10 and its end is engaged with a control device (not shown because it is not part of the invention) capable of causing the blade 17 to pivot.

[0060] On the inner side, the blade 17 is extended by a guide pivot 20 of axis Y, which starts from the inner end 21 of the blade 17 and extends radially inwards (downwards). This guide pivot 20 can advantageously be made in one piece with the inner end 21 of the blade 17 and thus be in one piece with the blade 17, but can also be attached and fixed to it.

[0061] Depending on the variants, the guide pivot 20 may be in the shape of a cone of revolution as shown in Figures 2 to 5, or in the shape of a truncated cone of revolution as shown in Figures 6 and 7. It comprises a side wall 22 and possibly an inner wall 23 in the case of a truncated cone. In all cases, it has an inwardly directed tapered end 24, of angle a at the apex of the cone or truncated cone (shown in Figures 2 and 7).

[0062] At each stator stage 9, the fixed blades 13 are arranged radially around an inner stator ring 25 belonging to the inner casing 11.

[0063] In the case of a guide assembly 1 according to the invention, the inner ring 25 comprises a hollow housing 26, open towards the outside, which is located opposite the internal end 21 of the blade 17 and in which the guide pivot 20 is engaged.

[0064] This hollow housing 26 is a cavity 27 delimited by a wall 28. This cavity 27 is of conical shape of revolution when the guide pivot 20 is in the shape of a cone of revolution as shown in Figures 2 to 5. When the guide pivot 20 is in the shape of a truncated cone of revolution, the cavity 27 can be of conical shape of revolution as in [Fig.6] or truncated cone of revolution as in [Fig.7].

[0065] In all cases, the cavity 27 is oriented along the radial axis Y and has a shape complementary to that of the guide pivot 20 which can thus engage therein. As shown in Figures 2 and 7, the cavity 27 has substantially the same angle α as that of the top of the guide pivot 20.

[0066] When the guide pivot 20 is engaged in the cavity 27, it remains at a distance from the wall 28 of the cavity 27, its side wall 22 and its possible inner wall 23 not being in contact with the wall 28 of the cavity 27 in a normal operating situation. A free space 29, that is to say unoccupied, thus extends all around the guide pivot 20, between the wall(s) 22, 23 of the guide pivot 20 and the wall 28 of the cavity 27.

[0067] The distance which exists between the side wall 22 of the guide pivot 20 and the wall 28 of the cavity 27, in a normal operating situation, has been symbolized by the reference D in FIGS. 2, 3, 6 and 7.

[0068] In the normal operating situation shown in Figures 2, 3, 6 and 7, the guide pivot 20 is centered in the cavity 27. The guide pivot 20 and the cavity 27 are coaxial. The distance D is non-zero and the free space 29 surrounds the guide pivot 20. The inner end 21 of the blade 17 is also distant from the outer wall 30 of the inner ring 25.

[0069] The blade 15 can thus freely pivot around the Y axis to modify the angular orientation of the blade 17, since there is no contact between the pivot 20 and the cavity 27, nor between the internal end 21 of the blade 17 and the external wall 30 of the internal ring 25. There is thus no friction at this level and therefore no wear.

[0070] When the turbomachine is in operation, the temperature inside the compressors 4, 5 increases. It can for example reach 300 to 400°C in the high-pressure compressor 5. Under these conditions and as shown in [Fig. 3], the parts can expand, mainly in their radial direction, which modifies their relative spacing.

[0071] As a result, the value of the distance D between the wall 22 of the guide pivot 20 and the wall 28 of the cavity 27 decreases compared to the situation at ambient temperature shown in [Fig. 2]. However, it nevertheless remains non-zero, the wall or walls 22, 23 of the guide pivot 20 not touching the wall 28 of the cavity 27. The inner end 21 of the blade 17 is also not in contact with the outer wall 30 of the inner ring 25. The blade 15 can thus continue to pivot freely about the Y axis to adjust the angular position of the blade 17.

[0072] Depending on the intended applications, the operating temperature and the materials used, a person skilled in the art will easily choose a suitable value for the distance D to guarantee this absence of contact after expansion during operation.

[0073] Advantageously, the distance D chosen is however not too great so that the passage of air under the blade 17 and around the pivot 20 remains limited in operation so as not to disturb the flow of air in the vein.

[0074] The guide assembly 1 according to the invention does not hold the lower part of the blade 15 but simply guides its pivoting. It also provides a safety function in the event of an abnormal situation, for example those shown in Figures 4 and 5.

[0075] Indeed, when the blade 15 pivots, friction occurs between the parts of the upper (external) pivot connection which hold the blade 15 in place. Over time, this friction generates wear on the parts, in particular the cylindrical pin through which the rod 18 passes. The rod 18, which is less well held, can then tilt or shift laterally, which leads to an inclination of the blade 17 as shown in [Fig. 4] or to a lateral offset of the blade 17 as shown in [Fig. 5].

[0076] In both cases, the side wall 22 of the pivot 20 then abuts against the wall 28 of the cavity 27, thus preventing the continuation of the tilting or offset movement. By this contact between the pivot 20 and the cavity 27, the abnormal movement is stopped before the inner end 21 of the blade 17 touches the outer wall 30 of the inner ring 25 and especially before the blade 17 comes into contact with the blades of the moving vanes 12 of the adjacent rotor stage 8, which would cause significant damage to the compressor. The guide assembly 1 according to the invention thus constitutes an effective safety system which prevents the occurrence of potentially serious incidents.

[0077] Furthermore, since the inner end 21 of the blade 17 does not touch the outer wall 30 of the inner ring 25, the blade 15 can continue to pivot despite everything, with friction of the side wall 22 of the pivot 20 against the wall 28 of the cavity 27. The system can therefore continue to operate until the next maintenance operation where the worn parts of the upper pivot link will be replaced to return to a normal operating situation.

Claims

Claims

1. Guide assembly (1) for the pivoting of a fixed blade with variable angular orientation (15) of a compressor (4, 5) of an aircraft turbomachine (2) with an X axis, said guide assembly comprising: - a fixed blade with variable angular orientation (15), capable of pivoting around a radial axis Y perpendicular and intersecting the X axis, said blade comprising a blade (17) extended radially in the inner part by a guide pivot (20);and - an inner stator ring (25), comprising a hollow housing (26), open towards the outside, in which the guide pivot (20) of the blade (15) is engaged, - guide assembly characterized in that: - the guide pivot (20) is in the shape of a cone or truncated cone of revolution, with a radial axis Y and with a tapered end (24) directed towards the inside, - the hollow housing (26) is a cavity (27) of conical or truncated cone shape of revolution, with a radial axis Y and a shape complementary to that of the guide pivot (20), said cavity being delimited by a wall (28).;

2. Guide assembly (1) according to the preceding claim, characterized in that, in a normal operating situation, the guide pivot (20) is located at a distance from the wall (28) of the cavity (27) in which it is engaged, a free space (29) extending all around the guide pivot (20), between the guide pivot (20) and the wall (28) of the cavity (27).

3. Guide assembly (1) according to one of the preceding claims, characterized in that the guide pivot (20) has, at the top of the cone or truncated cone, an angle a of between 10° and 60°.

4. Guide assembly (1) according to one of the preceding claims, characterized in that the guide pivot (20) is in one piece with the blade (17).

5. Guide assembly (1) according to one of the preceding claims, characterized in that the wall (28) of the cavity (27) is in one piece.

6. Stator stage (9) of a turbomachine (2) with an X axis, comprising an inner stator ring (25) and a plurality of fixed blades with orientation variable angular orientation (15) distributed radially around said inner ring (25) of stator, characterized in that it comprises a guide assembly (1) according to one of claims 1 to 5 for each of the fixed blades with variable angular orientation (15).

7. Compressor (4, 5) of a turbomachine (2) comprising at least one guide assembly (1) according to one of claims 1 to 5.

8. Compressor (4, 5) according to claim 7 characterized in that said guide assembly (1) is located in the upstream part (14) of the compressor (4, 5).

9. Aircraft turbomachine (2) comprising at least one compressor (4, 5) according to claim 7 or 8.

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