FR3052494A1 - VARIABLE TIMING RECTIFIER STAGE FOR TURBOMACHINE COMPRESSOR COMPRISING A SEAL ON EXTERNAL HOUSING AND / OR INTERNAL RING - Google Patents

Abstract

The main object of the invention is a variable-pitch rectifier stage for a radial symmetry axis compressor, comprising a row of variable-pitch vanes (11), each having pivots at its radially outer and inner ends. external and internal engaged in housings of an outer casing and an inner ring (7), each variable-pitch blade (11) defining external and internal sets, respectively between the outer casing and the outer end of the blade, and between the inner ring (7) and the inner end of the blade, characterized in that at least one seal (4) forming a gas circulation barrier at least the lower surface (I ) to the extrados (E) of a blade is fixed at the level of the external clearance on the outer casing vis-à-vis the outer end of said blade and / or at the internal clearance on the inner ring (7) vis-à-vis the inner end of said blade.

Description

VARIABLE-SETTING RECTIFIER STAGE FOR TURBOMACHINE COMPRESSOR COMPRISING A SEAL ON EXTERNAL HOUSING AND / OR INTERNAL RING

DESCRIPTION

TECHNICAL AREA

The present invention relates to the field of turbomachines, and more particularly to the field of variable-pitch rectifier stages for a turbomachine compressor. The invention applies to all types of land or aeronautical turbomachines, and in particular to aircraft turbomachines such as turbojets and turboprops. More preferably, it applies to a double-body and dual-flow turbojet engine. The invention thus relates more precisely to a variable-pitch rectifier stage for a turbomachine compressor, as well as a compressor and an associated turbomachine.

STATE OF THE PRIOR ART

A turbomachine compressor, in particular a high-pressure compressor, can consist of a plurality of compression stages each formed of an annular row of blades mounted on a shaft of the turbomachine and a plurality of rectifier stages. , in particular a plurality of variable-pitch rectifier stages (also referred to as "VSV rectifier stages" for "Variable Stator Vane" in English), mounted on an outer annular casing of the turbomachine.

Each VSV rectifier stage comprises an annular row of variable-pitch vanes carried by a stator casing and adjustable in position around their axes to optimize the flow of gases in the engine of the turbomachine. In particular, VSV blades can be staggered depending on the operating speed of the engine. The VSV blades can thus, by adapting to the arrival angle of the gas, a significant gain margin pumping and a significant gain compressor efficiency.

Each blade VSV is movable in rotation about its axis between an "open" or "full open" position in which each blade extends substantially parallel to the longitudinal axis of the turbomachine, and a "closed" position. or "quasi-closing" in which the vanes are inclined with respect to the axis of the turbomachine and thus reduce the section of passage of air through the VSV rectifier stage. When the turbomachine is at low speed or at idle speed, the VSV blades are brought into their closed position, and when the turbomachine is in full throttle, for example for takeoff, the VSV blades are brought into their position. opening.

In the present art, a vane VSV comprises a substantially cylindrical axial pivot at each of its ends, these pivots defining the axis of rotation of the blade. The radially external pivot called control pivot is engaged in the housing of a substantially radial or inclined chimney of an outer casing of the turbomachine and is connected by a lever to a control ring actuated by a jack, an electric motor or the like . The rotation of the control ring is transmitted by the levers to the outer pivots of the blades and rotates about their axes.

The radially inner pivot called the guide pin is engaged in a substantially radial or inclined housing of an inner ring mounted on an annular ring carrying blocks of abradable material.

The outer casing and the inner ring of the turbomachine delimit between them the annular flow vein of the compressor gases.

FIG. 1 very schematically shows, in section, an example of such a variable-setting rectifier stage 10 according to the prior art, and FIG. 2 is an enlarged partial view in perspective of the zone A of FIG. The VSV rectifier stage 10 comprises an annular row of variable-pitch vanes 11, each having a radially outer pin 8 and a radially inner pin 9, substantially cylindrical and respectively engaged in housings of an outer casing 6 and an inner ring 7 of the turbomachine. These blades 11 have a lower face I and an extrados face E which are connected to their upstream and downstream ends forming BA leading edges and LF leakage of the air flowing in the compressor.

Since the setting of such a VSV rectifier stage 10 varies, and the inner and outer shrouds are respectively formed by substantially cylindrical internal 9 and outer 8 pivots, it is appropriate to leave an internal clearance J1 between the blade 11 and the inner ring. 7, and an external clearance J2 between the blade 11 and the outer casing 6, in particular to prevent any contact between these elements. The extent and amplitude of such games are variable depending on the engine of the turbomachine. Nevertheless, the existence of such games J1 and J2 influences the flow of gases around the blades 11. In particular, the difference in static pressure between the intrados I and the extrados E of the blade 11 generates a migration of gas flow through internal J1 and external J2 games. This phenomenon then generates significant performance losses for the compressor of the turbomachine.

Solutions have already been proposed in the prior art to overcome these difficulties. However, these solutions have the disadvantage of impacting the geometry of the variable-pitch vanes, for example by providing local thickening of the variable-pitch vanes.

STATEMENT OF THE INVENTION

There is thus still a need to propose a solution making it possible to prevent, or at least reduce as significantly as possible, the flow of gas capable of circulating through the internal and external sets of variable-pitch vanes from a rectifier stage to turbomachine compressor variable timing, in order to significantly improve the performance of the compressor, without impacting the geometry of the variable-pitch vanes. The object of the invention is to remedy at least partially the needs mentioned above and the drawbacks relating to the embodiments of the prior art. The object of the invention is therefore, according to one of its aspects, a variable-pitch rectifier stage for a radial symmetry axis compressor, in particular a high-pressure compressor, comprising an annular row of variable-pitch vanes, each variable-pitch blade having at its radially outer and radially inner ends respectively a substantially cylindrical outer pivot and internal pivot, the outer pivot and the inner pivot being respectively engaged in housings of an outer casing and an inner ring the variable-pitch rectifier stage, each variable-pitch blade defining an external clearance and an internal clearance, respectively between the outer casing and the outer end of the variable-pitch blade, and between the inner ring and the internal end of the variable-pitch blade, characterized in that at least one seal, in particular a brush seal (or "seal br osse "for more concision), forming obstacle gas circulation at least from the lower surface to the upper surface of a blade variable pitch is fixed at the outer play on the outer casing vis-à-vis the external end of said variable-pitch blade and / or at the internal clearance on the inner ring vis-à-vis the inner end of said variable-pitch blade.

Thanks to the invention, it may be possible to significantly and effectively reduce the flow rate of the gas through an internal clearance between the inner ring and a VSV blade, and / or an external clearance between the outer casing and a VSV blade, VSV rectifier stage. The invention can thus allow control of the internal and external clearances of a vane VSV by placing one or more seals forming a gas circulation obstacle. It can thus significantly improve the aerodynamic performance of the compressor, the margin pumping, and therefore the operability of the turbomachine.

In addition, at partial or intermediate speed, the fact of having such a seal in the aerodynamic vein can be likened to a vortex generator and can provide a gain vis-à-vis the operability low speed engine. The variable-pitch rectifier stage according to the invention may further comprise one or more of the following characteristics taken separately or in any possible technical combination.

Said at least one seal may advantageously extend respectively on the outer casing and / or on the inner ring in a direction forming an angle with the radial axis of symmetry between 0 and 35 °.

Furthermore, at least one seal forming an obstacle for the circulation of gases at least from the intrados to the extrados of a variable-pitch blade can be fixed at the level of the external clearance on the outer casing vis-à- screw of the outer end of said variable-pitch blade, and said at least one seal may extend on the outer casing in a direction forming an angle with the axis of radial symmetry between 15 and 35 °.

In addition, at least one seal forming an obstacle for the circulation of gases at least from the intrados to the extrados of a variable-pitch blade can be fixed at the level of the internal clearance on the inner ring vis-à-vis -vis the inner end of said variable-pitch blade, and said at least one seal can extend on the inner ring in a direction forming an angle with the axis of radial symmetry between Oet 25 ° .

In addition, said at least one seal may particularly extend respectively on the outer casing and / or on the inner ring substantially along the radial axis of symmetry. The thickness of said at least one seal, corresponding to the largest transverse dimension of said at least one seal, is preferably less than the thickness of said variable-pitch vane, corresponding to the largest transverse dimension of said variable pitch blade.

The seal may extend over at least the major part of the external clearance and / or internal clearance of said variable-pitch vane, more preferably over three-quarters, or even substantially all of the external clearance and / or internal game. In particular, the seal may have a radial and / or axial dimension respectively substantially equal to the radial and / or axial dimension of the external and / or internal clearance.

The seal may be a brush seal, and in particular a wire brush seal or, preferably, a carbon fiber or ceramic brush seal.

The length of the bristles of the brush seal can in particular be defined according to the dimensions of the external clearance and / or the dimensions of the internal clearance and / or of the differential pressure.

The seal may extend from the outer casing and / or the inner ring of the variable-pitch rectifier stage substantially in contact with the variable-pitch blade. By "substantially in contact" is meant that the end of the seal, including the bristles of the brush seal, can come to touch or flush with the inner end and / or outer end of the variable-pitch blade. In particular, the seal may make it possible to form an obstacle substantially closing the flow of gas from the lower surface to the upper surface, in the internal clearance between the inner ring and the variable-pitch blade and / or in the external clearance between the outer casing and the variable-pitch blade.

The seal may have an outer contour whose shape at least partially matches the shape of the airfoil of said variable-pitch blade. Another subject of the invention is, according to another of its aspects, a turbomachine compressor, in particular a high-pressure compressor, characterized in that it comprises at least one rectifying variable-setting stage as defined above. The invention finally relates, in another of its aspects, a turbomachine, characterized in that it comprises a compressor as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood on reading the following detailed description of an example of non-limiting implementation thereof, as well as on the examination of the figures, diagrammatic and partial. of the accompanying drawing, in which: - Figure 1 shows, in section, an example of a variable-setting rectifier stage according to the prior art, - Figure 2 is an enlarged partial view in perspective of the area; 1, FIGS. 3A and 3B illustrate, in an enlarged view and in perspective, an example of a variable-pitch blade of a variable-pitch rectifying stage according to the invention, respectively before and after being put in place. a brush seal in the internal clearance of the blade, and - Figures 4A and 4B illustrate, very schematically in section, an example of implementation of a brush seal at the internal or external clearance of a variable-pitch blade of a variable-pitch rectifier stage according to the i nvention, respectively during a partial regime operation and during a high speed operation.

In all of these figures, identical references may designate identical or similar elements.

In addition, the different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF A PARTICULAR EMBODIMENT

Throughout the description, it is noted that the upstream and downstream terms are to be considered with respect to a main direction of normal gas flow (from upstream to downstream) for a turbomachine. Furthermore, the T-axis of the turbomachine is the axis of radial symmetry of the turbomachine. The axial direction corresponds to the direction of the axis T of the turbomachine, and a radial direction is a direction perpendicular to this axis T. In addition, unless otherwise stated, the adjectives and adverbs axial, radial, axially and radially are used in reference to the aforementioned axial and radial directions. Moreover, unless otherwise stated, the internal and external adjectives are used with reference to a radial direction so that the part or the internal (ie radially internal) face of an element is closer to the axis of the turbomachine than the part or the external (ie radially external) face of the same element.

Figures 1 and 2 have already been described previously in relation to the state of the prior art.

FIGS. 3A and 3B show, in an enlarged view and in perspective similar to that of FIG. 2, an example of a variable-pitch blade 11 of a variable-setting rectifier stage 10 according to the invention, respectively before and after placing a brush seal 4 in the internal clearance J1 of the blade 11.

Indeed, as explained above, the setting of the variable-pitch rectifier stage 10 according to the invention being scalable according to the speed of the engine of the turbomachine, internal J1 and external J2 games exist respectively at the inner and outer ends. of the variable pitch blade 11. These internal J1 and external J2 sets may have different openings depending on the engine speed of the turbomachine. For example, in case of acceleration, it is possible that the internal clearance J1, at the foot of the blade 11, closes while the external clearance J2, at the head of the blade 11, opens. These differences in the behavior of the internal clearance J1 and external clearance J2 as a function of the engine speed of the turbomachine involve situations where the recirculation of the gases around the blade 11 is important, and therefore where the aerodynamic impact in terms of performance and performance operability is important. The example of FIGS. 3A and 3B is relative to the internal clearance J1 located at the bottom of the blade 11 of the variable-pitch rectifier stage 10 according to the invention. Of course, the principle of setting up a brush seal 4 at the internal clearance J1 is also valid for the establishment of a brush seal 4 at the external clearance J2 at the blade head 11 of the variable-pitch rectifier stage 10 according to the invention.

As can be seen in FIG. 3A, in the absence of a brush seal 4 in the internal clearance J1 of the blade 11, a gas migration phenomenon according to the arrow FA, from the intrados I of FIG. dawn 11 (ie from the concave face of the blade 11) to the extrados E of the blade 11 (ie from the convex face of the blade 11), occurs due to a static pressure difference between the intrados I and the extrados E of the dawn 11.

According to the invention, as can be seen in FIG. 3B, the inner ring 7 comprises a brush seal 4 forming an obstacle for the circulation of gases from the intrados I towards the extrados E of the dawn 11, the brush seal 4 being positioned at the internal clearance Jl of the blade 11.

In this way, the migration of the gas flow from the intrados I to the extrados E of the blade 11 is non-existent, or as small as represented by the arrow FB, which makes it possible to significantly improve the performance of the turbomachine .

Indeed, as can be seen in FIG. 3B, the brush seal 4 advantageously extends over most of the internal clearance J1 of the variable pitch blade 11, and in particular over substantially the entire internal clearance. D1 of dawn 11.

FIGS. 4A and 4B illustrate, very schematically and in cross-section, an example of setting up a brush seal 4 at the internal clearance J1 or external clearance J2 of a variable-pitch blade 11 of a rectifying step variable 10 according to the invention, respectively during a partial or intermediate mode operation, and during operation at high speed.

As can be seen in FIG. 4A, the brush seal 4 advantageously extends on the outer casing 6 or on the inner ring 7 in a direction D forming an angle α with the radial axis of symmetry T. In this example, but in no way limiting, the angle a is substantially zero so that the brush seal 4 extends substantially along the axis of radial symmetry T.

In addition, as can be seen in these figures 4A and 4B, the brush seal 4 may have an outer contour 13 whose shape at least partially matches the shape of the airfoil 14 of the variable-pitch blade 11. the brush seal 4 may have a substantially linear shape.

The brush seal 4 can be fixed on the outer casing 6 opposite the outer end of the variable-pitch blade 11 and / or on the inner ring 7 facing the internal end of the variable-pitch blade 11, by any type of means known per se.

Advantageously, as shown in FIG. 4A, the thickness ej of the brush seal 4, corresponding to the largest transverse dimension of the brush seal 4, is smaller than the thickness e ee of the variable pitch blade 11, corresponding to the largest transverse dimension of the variable pitch blade 11.

Preferably, this thickness ej of the brush seal 4 is chosen to be as small as possible in order to limit the impact at intermediate speed as in the representation of FIG. 4A. However, this thickness ej of the brush seal 4 is also chosen to be sufficient to ensure an acceptable seal, ie to eliminate secondary flows. An optimization of the thickness ej of the brush seal 4 can thus be achieved depending on the aerodynamic conditions.

Thanks to the invention, it can thus be seen that in the case of high-speed operation, as represented in FIG. 4B, the internal clearance J1 or the external clearance J2 is practically eliminated, which makes it possible to obtain performance gains and significant returns.

In the case of a partial regime operation, as shown in FIG. 4A, the internal clearance J1 or external clearance J2 is still present but the additional losses are moderate because of the presence of the brush seal 4.

It should also be noted that the brush seal 4 can be positioned angularly on the outer casing 6 or on the inner ring 7 opposite the variable-pitch blade 11, the latter being positioned according to a "zero" setting to improve the efficiency at very high speed and flow capacity, or positioned according to an intermediate timing according to the seal to be assured and / or the weighting associated with the performance of the regime.

The brush seal may be selected for example from metal brush seals and / or preferably carbon fiber or ceramic brush seals.

Of course, the invention is not limited to the embodiment which has just been described. Various modifications may be made by the skilled person.

Claims (11)

1. Variable-setting rectifying stage (10) for a radial symmetry axis compressor (T), comprising an annular row of variable-pitch vanes (11), each variable-pitch blade (11) having at its ends radially external and radially inner, respectively an outer pivot (8) and an inner pivot (9) substantially cylindrical, the outer pivot (8) and the inner pivot (9) being respectively engaged in housings of an outer casing (6) and an inner ring (7) of the variable-pitch rectifier stage (10), each variable-pitch blade (11) defining an external clearance (J2) and an internal clearance (J1) respectively between the outer casing ( 6) and the outer end of the variable-pitch blade (11), and between the inner ring (7) and the inner end of the variable-pitch blade (11), characterized in that at least a seal (4) forming an obstacle for the circulation of gases at least from the intrados (I) to the extrados (E) a variable pitch blade (11) is fixed at the external clearance (J2) on the outer casing (6) vis-à-vis the outer end of said variable-pitch blade (11) and / or at the internal clearance (Jl) on the inner ring (7) vis-à-vis the inner end of said variable-pitch blade (11). 2. Rectifier stage according to claim 1, characterized in that said at least one seal (4) extends respectively on the outer casing (6) and / or on the inner ring (7) in one direction ( D) forming an angle (a) with the radial axis of symmetry (T) between 0 and 35 °. 3. Rectifier stage according to claim 1 or 2, characterized in that at least one seal (4) forming an obstacle for the circulation of gases at least from the intrados (I) to the extrados (E) of a variable pitch blade (11) is fixed at the external clearance (J2) on the outer casing (6) opposite the outer end of said variable pitch blade (11), and in that said at least one seal (4) extends on the outer casing (6) in a direction (D) forming an angle (a) with the radial axis of symmetry (T) between 15 and 35 °. 4. Rectifier stage according to one of the preceding claims, characterized in that at least one seal (4) forming an obstacle for the circulation of gases at least from the intrados (I) to the extrados (E) d a variable pitch blade (11) is fixed at the internal clearance (Jl) on the inner ring (7) opposite the inner end of said variable pitch blade (11), and said at least one seal extends over the inner ring (7) in a direction (D) forming an angle (a) with the radial axis of symmetry (T) between 0 and 25 °. 5. Rectifier stage according to any one of the preceding claims, characterized in that the thickness (ej) of said at least one seal (4) corresponding to the largest transverse dimension of said at least one seal is less than the thickness (ea) of said variable pitch blade (11) corresponding to the largest transverse dimension of said variable pitch blade (11). Rectifier stage according to one of the preceding claims, characterized in that the said at least one seal (4) extends over at least the major part of the external clearance (J2) and / or the internal clearance ( Jl) of said variable pitch blade (11). 7. Stage rectifier according to any one of the preceding claims, characterized in that said at least one seal (4) has an outer contour (13) whose shape at least partially conforms to the shape of the airfoil (14) said variable pitch blade (11). 8. Rectifier stage according to any one of the preceding claims, characterized in that said at least one seal (4) is a brush seal (4). 9. Stage rectifier according to claim 8, characterized in that said at least one seal (4) is carbon fiber or ceramic. 10. A turbomachine compressor, particularly a high-pressure compressor, characterized in that it comprises at least one variable-pitch rectifier stage (10) according to any one of the preceding claims. 11. Turbomachine, characterized in that it comprises a compressor according to claim 10.