FR3108369A1 - RECTIFIER FOR AIRCRAFT TURBOMACHINE, INCLUDING A VARIABLE TIMING ANGLE SWIVEL LIMITER - Google Patents

Abstract

The invention relates to a rectifier (24) for an aircraft turbomachine, comprising an outer annular structure (30), an inner annular structure (40), and a plurality of blades (26) with variable pitch angle comprising a head (50) as well as a foot (60) together defining an axis of rotation (76) of the vane. According to the invention, the rectifier comprises, associated with at least one of the blades (26) with variable pitch angle, a limiter (80) for the pivoting of this blade about its axis of rotation (76), the limiter comprising : - at least one stop member (96a, 96b) provided on a first element (60) among the head and the root of the blade; and - at least one complementary stop member (102a, 102b) provided on the outer / inner annular structure (40) which cooperates with said first element (60). Figure for the abstract: Figure 3.

Description

AIRCRAFT TURBOMACHINE RECTIFIER, INCLUDING VARIABLE PITCH ANGLE BLADE SWING LIMITER

The present invention relates to the field of aircraft turbine engines. It relates more particularly to the vanes with variable pitch angle arranged within the rectifiers fitted to turbomachine compressors.

The invention applies to any type of turbomachine, in particular turbojets.

STATE OF THE PRIOR ART

In certain aircraft turbomachine modules, such as compressors, there is provided an alternation of rotating bladed wheels corresponding to rotor wheels, and fixed bladed wheels corresponding to rectifiers.

The particularity of some straighteners lies in their incorporation of variable pitch angle vanes. Controlling the pitch angle of these blades, also called controlling the incidence of the blades, makes it possible to modify the gas flow characteristics according to the operating regimes of the turbomachine.

The incidence of the blades is controlled using known control means, for example those mentioned in documents FR 2 941 018 A1 and FR 2 890 707 A1.

However, in the event of a malfunction of the control means, the vanes with variable pitch angle may find themselves free to rotate around their axes of rotation with respect to the inner and outer rings on which these vanes are pivotally mounted. The blades are then subjected to the pressure forces of the gases flowing through the stator, which leads them towards a substantially axial orientation, corresponding to a so-called “feathering” position.

In this feathering position, the stator vanes risk coming into contact with the vanes of the revolving wheels which are directly adjacent to them, with possible damage to these vanes as a result.

To respond at least partially to the drawback mentioned above, the invention firstly relates to a rectifier for an aircraft turbomachine, comprising an outer annular structure, an inner annular structure, as well as a plurality of vanes with variable pitch angle arranged between the outer and inner annular structures, each vane comprising a tip cooperating with a tip guide housing provided on the outer annular structure, as well as a root cooperating with a root guide housing provided on the inner annular structure, the head and the root together defining an axis of rotation of the blade around which this blade is designed to pivot in order to vary its pitch angle.

According to the invention, the stator comprises, associated with at least one of the vanes with variable pitch angle, a pivot limiter for this vane around its axis of rotation, the limiter comprising:
- at least one abutment member provided on a first element among the head and the root of the blade; And
- At least one complementary abutment member provided on the outer/inner annular structure which cooperates with said first element.

In addition, the limiter is designed so that the coming into contact of the abutment member, with the complementary abutment member, blocks the pivoting of this blade around its axis of rotation.

The invention thus provides a blade pivot limiter based on a simple, reliable design, and capable of avoiding the risk of the blade concerned coming into contact with the blades of the directly adjacent rotating wheels. For example, the abutment member and the complementary abutment member are arranged so as to come into contact before the blade reaches its feathering position, in which it has maximum axial bulk.

The invention also has at least one of the following optional characteristics, taken individually or in combination.

The limiter preferably comprises:
- A first and a second abutment member provided on said first element; And

- a first and a second complementary abutment member provided on the outer/inner annular structure which cooperates with said first element,
and the limiter is designed so that:
- the coming into contact of the first abutment member, with the first complementary abutment member, blocks the pivoting of this blade around its axis of rotation according to a first direction of rotation; And
- The coming into contact of the second abutment member, with the second complementary abutment member, blocks the pivoting of this blade around its axis of rotation according to a second direction of rotation, opposite to the first direction.

According to a preferred embodiment, said first element comprises a slot, the bottom of which forms each abutment member. This solution is particularly simple to implement and inexpensive.

Furthermore, at least one lug forming each complementary abutment member extends inside the head/foot guide housing of the outer/inner annular structure which cooperates with said first element. This lug can thus easily cooperate with the aforementioned slot, so as to form the pivoting limiter of the blade with variable pitch angle.

Alternatively, the slot could be located at the level of the head/foot guide housing of the outer/inner annular structure, and said at least lug would then be arranged projecting from the first element.

Preferably, the bottom of the slot is flat or substantially flat, and/or the lug has a vertex from which extend two opposite flat or substantially flat edges, respectively forming the first and second complementary abutment members.

Preferably, the outer/inner annular structure which cooperates with said first element of the blade, comprises an upstream ring and a downstream ring fixed one on the other, and respectively defining an upstream part and a downstream part of the housing of foot / head guidance of this vane. This design in two axial parts of the annular structure concerned facilitates the mounting of the blades on this same annular structure. Nevertheless, other designs remain possible for the annular structure, in particular with a single ring, without departing from the scope of the invention.

Preferably, said first element is the root of the blade. Alternatively, the limiter could be located on the blade head. According to yet another alternative, two pivot limiters could respectively equip the head and the root of the blade.

Preferably, said first element comprises two sections succeeding each other along the axis of rotation of the blade, among which a first section equipped with each abutment member, and a second section of smaller diameter located at one end of the blade. 'dawn.

Preferably, all of the characteristics described above apply in an identical or analogous manner to several vanes with variable pitch angle of the same stator, and even more preferably, to each of the vanes of this stator.

The invention also relates to a compressor comprising at least one such rectifier, the compressor preferably being a low-pressure compressor.

Finally, the invention also relates to an aircraft turbine engine comprising at least one such compressor.

Other advantages and characteristics of the invention will appear in the non-limiting detailed description below.

This description will be made with regard to the appended drawings, among which:

shows a schematic side view of a turbojet engine according to the invention;

represents a schematic side view of part of the low or high pressure compressor fitted to the turbojet engine shown in the preceding figure;

shows a partial view in axial section of the cooperation between a root of a blade of the stator shown in the previous figure, and an internal annular structure of this stator;

shows a partial sectional view taken along the line IV-IV of Figure 3;

shows a perspective view of part of the blade shown in Figures 3 and 4;

depicts a perspective view of a portion of the rectifier inner annular structure shown in Figures 3 and 4;

shows a perspective view of an assembly between the rectifier parts shown in Figures 5 and 6; And

shows a sectional view similar to that of FIG. 4, diagramming a case of failure of the control mechanism for the pitch angle of the vane of the rectifier.

DETAILED DISCUSSION OF PREFERRED EMBODIMENTS

Referring to Figure 1, there is shown a turbofan engine 1 and double body. The turbojet engine 1 conventionally comprises a gas generator 2, on either side of which are arranged a low pressure compressor 4, and a low pressure turbine 12. The gas generator 2 comprises a high pressure compressor 6, a combustion 8 and a high-pressure turbine 10. Subsequently, the terms “upstream” and “downstream” are considered according to a main direction of gas flow through the turbojet, this direction being shown schematically by the arrow 14.

The low pressure compressor 4 and the low pressure turbine 12 form a low pressure body, and are connected to each other by a low pressure shaft 11 centered on a central longitudinal axis 3 of the turbojet. Similarly, the high pressure compressor 6 and the high pressure turbine 10 form a high pressure body, and are connected to each other by a high pressure shaft 13 centered on the axis 3 and arranged around the low shaft pressure 11.

The turbojet 1 also comprises, at the front of the gas generator 2 and of the low pressure compressor 4, a fan 15 which is here arranged directly at the rear of an air inlet cone of the engine. Nevertheless, depending on the design of the turbojet engine and its application, the fan 15 may be optional.

When such a fan 15 is provided, it is rotatable along the axis 3, and surrounded by a fan casing 9. This fan 15 may not be driven directly by the low pressure shaft 11, but driven indirectly by this same shaft via a reducer 20, which allows it to rotate with a slower speed.

In addition, conventionally, the turbojet engine 1 defines a primary stream 16 intended to be traversed by a primary flow, as well as a secondary stream 18 intended to be traversed by a secondary flow located radially outwards with respect to the primary flow. .

Referring to Figure 2, there is shown a part of the low pressure compressor 4, formed by the alternation of bladed wheels 22 rotating along the longitudinal central axis 3 of the turbojet, and rectifiers 24. The association of a wheel rotary 22 and a rectifier 24 forms a compressor stage. It is noted that the invention can be implemented on any one of the rectifiers 24 of the high and low pressure compressors, but that it preferentially relates to the stages of the low pressure compressor 4, and even more preferentially the stage most upstream, called the first stage of the low pressure compressor.

Each rectifier 24 firstly comprises an outer annular structure 30, centered on the axis 3 and corresponding to an axial part of the outer casing 32 of the compressor. This outer annular structure 30 of the rectifier 24 is preferably made in one piece, and it has an inner surface 36 of outer radial delimitation of the primary stream 16.

The rectifier 24 also comprises an inner annular structure 40, centered on the axis 3 and having an outer surface 42 of inner radial delimitation of the primary stream 16. This inner annular structure 40 can be made in one piece, or preferably by assembling several components, as will be detailed later.

Between the two annular structures 30, 40 of the stator 24, the latter has a plurality of vanes 26 with variable pitch angle, distributed circumferentially around the axis 3 so as to form an annular row of vanes 26. Each of the blades 26 comprises a central part 28 in the form of an aerodynamic blade, located in the primary stream 16 delimited by the two annular structures 30, 40. Each blade 26 also comprises a head 50 and a root 60, arranged on either side of the aerodynamic blade 28.

The head 50, also called the control pivot, is arranged in a head guide housing 52 provided on the outer annular structure 30. This housing 52 opens radially inwards into the primary vein 16. The head 50 passes through the structure 30 so that its radially outer end cooperates with a blade pitch angle control mechanism. This mechanism 70 has a classic design known to those skilled in the art. It comprises for example a control ring 72 arranged to move in rotation around the annular structure 30, as well as a control lever 74 connecting the end of the head 50 to this control ring 72. Usually, each blade 26 of the stator 24 is connected to the same control ring 74, by a dedicated lever 74.

By controlled rotation around the axis 3, the control ring 72 simultaneously drives all the control levers 74, which in turn cause the pivoting of each of the blades 26 according to an axis of rotation 76 which is specific to them. This axis of rotation 76 is defined by the head 50 and the foot 60. The control of the angle of pitch of the blades, or the control in incidence or in orientation of the blades 26, makes it possible to modify the flow characteristics of the gases. depending on the operating speeds of the turbojet engine.

The head 50, at its end opposite to that cooperating with the control lever 74, defines a platform 56 participating in the outer radial delimitation of the primary vein 16.

Furthermore, the foot 60, also called the guide pivot, is arranged in a foot guide housing 62 provided on the inner annular structure 40. This housing 62 opens radially outwards in the primary vein 16. As indicated above, the foot 60 participates with the head 50 in the definition of the axis of rotation 76 of the blade 26, axis around which this blade is capable of pivoting to vary its pitch angle.

The foot 60, at its radially inner end, defines a platform 66 participating in the inner radial delimitation of the primary vein 16.

With reference now to Figures 3 to 7, one of the particularities of the invention will be described, residing in the implementation of a pivot limiter 80 associated with each vane 26 of the rectifier. This limiter 80, the design of which is identical or similar for each blade 26, is preferably made at the root 60 of each of these blades. In this respect, it is noted that the foot 60 comprises two sections succeeding one another along the axis of rotation 76 of the blade. It is first of all a first section 60a equipped with part of the blade pivoting limiter. This first section 60a, the one located radially most outward in relation to the axis 3 and defining the platform 66, has a generally cylindrical shape of circular section. It is received in a first section 62a of the foot guide housing 62 of the inner annular structure 40, this first housing section 62a having a shape complementary to that of the first foot section 60a.

There is then a second foot section 60b, located radially the most inward in relation to the axis 3, and also having a generally cylindrical shape of circular section. It is received in a second section 62b of the foot guide housing 62 of the inner annular structure 40, this second foot housing section 62b having a shape complementary to that of the second foot section 60b.

It is noted that the second root section 60b, namely that which is at the end of the blade 26, has a smaller diameter than that of the first root section 60a. A break in section 82 is thus observed on foot 60, facing a shoulder 84 marking the separation between the two foot housing sections 62a, 62b.

Preferably, the radial play with respect to the axis of rotation 76 is higher at the level of the first sections 60a, 62a than at the level of the second sections 60b, 62b, so that the rotational guidance of the root of the blade s 'performed primarily by the cooperation between the two second sections 60b, 62b. In addition, the second foot guide section 62b corresponds to an internal orifice of a sleeve 86 belonging to the internal annular structure 40. This sleeve 86 is housed radially in a ring 90 of the structure 40, being locked in rotation there. by a blocking system 89.

On the other hand, the first guide section 62a preferably corresponds to an orifice made directly in the ring 90.

On the first foot section 60a, the limiter 80 comprises a slot 92 extending perpendicularly to the axis of rotation 76, being open radially outwards in relation to this same axis 76. Its bottom 96 is flat or substantially plane, and parallel to the axis of rotation 76. It is divided into two adjacent surfaces, respectively forming a first abutment member 96a and a second abutment member 96b, forming an integral part of the limiter 80.

In addition, the limiter 80 is equipped with a lug 98 extending radially towards the inside of the first guide section 62a, from the radial wall delimiting this first section. The lug 98, located at a distance from the shoulder 84, has a rounded top 100 on either side of which extend two opposite edges 102a, 102b inclined relative to each other. The two opposite edges are flat or substantially flat, and they respectively form a first complementary abutment member 102a, as well as a second complementary abutment member 102b.

The lug 98 is thus housed in the slot 92, and in normal operating configuration, the blade can be pivoted in incidence around its axis of rotation 76, without the abutment members 96a, 96b coming into contact with the complementary abutment members 102a, 102b. In this respect, FIG. 4 represents the angle A1 of possible angular movement for the blade 26, compatible with the setting law applied to this blade during the operation of the turbojet engine. This angle A1 can be of the order of 90 to 150°.

When the blade pitch angle control mechanism 70 is damaged, for example following a breakage of the control lever 74, the blade 26 becomes free to rotate about its axis 76. The primary flow passing through it applies pressure forces on it which cause it to pivot towards its feathering position. Nevertheless, thanks to the limiter 80, this feathering position is never reached since the pivoting of the blade 26 is stopped by the coming into contact of the first abutment member 96a with the first complementary abutment member 102a, or , in the direction of rotation of the blade, by contact of the second abutment member 96b with the second complementary abutment member 102b. The design is carried out so that the contacts likely to occur, in the event of failure, are preferentially planar contacts.

Figure 8 shows a case of malfunction in which the blade 26 pivots freely in a second direction of rotation S2 around the axis 76, until the contact of the second abutment member 96b with the second complementary abutment member 102b. Similarly, depending on the position of the blade at the time of the malfunction of the control mechanism, this blade 26 could pivot freely in a first direction of rotation S1 opposite to the second direction S2, until it comes into contact with the first stop member 96a with the first complementary abutment member 102a.

Finally, with more particular reference to Figures 3, 4, 6 and 7, the ring 90 of the inner annular structure 40 is preferably made in two axial parts fixed to one another, using fixing means conventional, such as bolts. This is an upstream ring 90b and a downstream ring 90a, respectively defining an upstream part 62'' and a downstream part 62' of each of the foot guide housings 62. This embodiment in two parts 90a, 90b facilitates the assembly of the blade 26 on the ring 90, by offering an easy insertion of the lugs 98 in the corresponding slots 96. The insertion of the sleeves 86 is also facilitated. Preferably, the segmentation between the two rings 90a, 90b is made in such a way that the upstream parts 62'' and the downstream parts 62' each represent a half-housing of one of the foot guide housings 62.

In addition, between the downstream parts 62' of the housings 62, the downstream ring 90a has solid portions pierced with orifices 106 for the passage of the fastening elements of the two rings. A similar design, but not shown, is provided on the upstream ring 90b.

Of course, various modifications can be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples and the scope of which is delimited by the appended claims.

Claims (10)

Straightener (24) for an aircraft turbomachine, comprising an outer annular structure (30), an inner annular structure (40), as well as a plurality of vanes (26) with variable pitch angle arranged between the outer annular structures and interior (30, 40), each vane (26) comprising a head (50) cooperating with a head guide housing (52) provided on the outer annular structure (30), as well as a root (60) cooperating with a root guide housing (62) provided on the inner annular structure (40), the tip and the root together defining an axis of rotation (76) of the blade around which this blade is adapted to pivot in order to vary its angle gap,
characterized in that the stator comprises, associated with at least one of the vanes (26) with variable pitch angle, a limiter (80) for pivoting this vane around its axis of rotation (76), the limiter comprising:
- at least one abutment member (96a, 96b) provided on a first element (60) among the head and the root of the blade; And
- at least one complementary abutment member (102a, 102b) provided on the outer/inner annular structure (40) which cooperates with said first element (60),
and in that the limiter (80) is designed so that the coming into contact of the abutment member (96a, 96b), with the complementary abutment member (102a, 102b), blocks the pivoting of this blade (26) around its axis of rotation (76). Rectifier according to Claim 1, characterized in that the limiter comprises:
- a first and a second abutment member (96a, 96b) provided on said first element (60); And
- a first and a second complementary abutment member (102a, 102b) provided on the outer/inner annular structure (40) which cooperates with said first element (60),
and in that the limiter (80) is designed so that:
- the coming into contact of the first abutment member (96a), with the first complementary abutment member (102a), blocks the pivoting of this blade around its axis of rotation (76) according to a first direction of rotation (S1) ; And
- the coming into contact of the second abutment member (96b), with the second complementary abutment member (102b), blocks the pivoting of this blade around its axis of rotation (76) according to a second direction of rotation (S2) , opposite to the first direction (S1). Rectifier according to Claim 1 or Claim 2, characterized in that the said first element (60) includes a slot (92), the bottom (96) of which forms each abutment member (96a, 96b). Straightener according to Claim 3, characterized in that at least one lug (98) forming each complementary abutment member (102a, 102b) extends inside the head/foot guide housing (62) of the outer/inner annular structure (40) which cooperates with said first element (60). Rectifier according to Claim 4 combined with Claim 2, characterized in that the bottom (96) of the slot (92) is flat or substantially flat, and/or in that the lug (98) has an apex (100) from which extend two opposite edges (102a, 102b) which are flat or substantially flat, respectively forming the first and second complementary abutment members. Straightener according to any one of the preceding claims, characterized in that the outer/inner annular structure (40) which cooperates with the said first element (60) of the blade, comprises an upstream ring (90b) and a downstream ring (90b ) fixed one on the other, and respectively defining an upstream part (62'') and a downstream part (62') of the foot/head guide housing (62) of this blade. Straightener according to any one of the preceding claims, characterized in that the said first element is the root (60) of the blade. Straightener according to any one of the preceding claims, characterized in that the said first element (60) comprises two sections (60a, 60b) succeeding one another along the axis of rotation (76) of the blade, among which a first section (60a) equipped with each abutment member (96a, 96b), and a second section (60b) of smaller diameter located at one end of the blade. Aircraft turbomachine compressor (4) comprising at least one rectifier (24) according to any one of the preceding claims, the compressor preferably being a low-pressure compressor (4). Aircraft turbomachine (1) comprising at least one compressor (4) according to the preceding claim.