EP2795068B1 - Turbomachine compressor guide vanes assembly - Google Patents

Description

The present invention relates to rectifiers for compressors, in particular high pressure compressors, intended for turbomachines, such as aircraft turbojets.

Generally, compressors for turbojet engines comprise a plurality of successive stages aligned along the longitudinal axis of the engine and composed alternately of mobile stages, forming the rotor of the compressor and the blades of which accelerate the gas flow by deflecting it with respect to said axis, and fixed stages, forming the stator and the blades of which partially transform the speed of the flow into pressure and straighten the latter in the direction of the next mobile stage.

The last stage (s) of the stator of the high pressure compressor are sectorized rectifiers which mainly form, after successive assembly of the sectors one after the other in an outer receiving casing, two concentric outer and inner shells, respectively, between which are arranged. the blades of the blading through which the then primary gas flow passes in a double-flow turbine engine. The outer shell is provided with an attachment means such as peripheral hooking flanges (of bent shape) front and rear according to the direction of flow, for connection with the outer casing of the stator of the compressor, while the shell internal externally carries abradable devices in conjunction with sealing devices of the rotor concerned.

In a turbojet, the rectifiers are parts working both statically (aerodynamic forces and mechanical forces passing through the outer casing) and dynamically (for example, significant vibratory phenomena during certain transient phases of engine operation), so that they are dimensioned beforehand on the basis of a so-called Haig curve which makes it possible to determine their mechanical resistance and their fatigue strength. Thus, from this curve, for a given static stress at a point of the part in question, the maximum admissible dynamic stress at this point is determined. We know, moreover from experience, that it is necessary to have the greatest possible maximum dynamic stress in order to be able to accept greater vibratory responses on the motor.

In the case of conventional fixed straighteners, the zone of maximum static stress and the zone of dynamic stress are located at the same location of the straightener, namely at the rear of the cylindrical outer shell formed by the assembled sectors. Thus, the allowable dynamic stress is greatly reduced due to the fact that the maximum static stress is located at the same location, which limits the operating possibilities of the rectifier and the fatigue resistance of the latter, in particular at sustained vibratory regimes.

A solution to optimize the dynamic stress is taught by the patent FR 2 945 331 of the applicant, which solution consists in providing a horseshoe-shaped bore in the cylindrical wall of the upper shell, between the rear edge and the trailing edge of at least some of the blades welded to the wall, so as " locally soften the shell. This makes it possible to considerably reduce the static stresses in the connecting radius of the angled rear flange to then increase the maximum dynamic stress and push back the fatigue limit of the dynamic rectifier.

If such a solution is validated when a sufficient space exists between the trailing edge of the blades and the rear peripheral edge of the outer shell for drilling there, on the other hand, when this space is insufficient, it cannot be practiced since this would require drilling also through the rear flange to pass through the wall of the shell. Such a solution would lead to weakening the rectifier too much and would therefore prove to be unsuitable for this type of rectifier.

The documents DE 10 2009 037620 A1 , EP 1 811 131 A2 and US 6 425 738 B1 disclose other prior art rectifiers.

The object of the present invention is to remedy this drawback.

For this purpose, the sectorized compressor rectifier for a turbomachine is of the type comprising assembled sectors forming two outer and inner concentric shells, between which are arranged blades with their leading and trailing edges respectively close to the front and rear transverse faces of the blades. ferrules according to the gas flow circulating in the compressor, and the outer shell of which is provided on the outside with a means of attachment with an outer casing for receiving said sectors.

According to the invention, such a rectifier is remarkable in that said attachment means comprises the characteristics according to claim 1.

Thus, by the axial offset of the attachment means to the right of the blades, the static stress, namely the aerodynamic forces and the forces of the casing, is no longer concentrated and located in the rear or downstream part of the outer shell, but at the level of the blades, and is therefore dissociated from the dynamic stress always localized at the level of the rear part of the external shroud of the rectifier. By dissociating these stresses which no longer overlap, by the offset of the attachment means of the shell relative to the casing, the rear part of the outer shell is less stressed since it is thus freed from the static stress, and n ' is more subject to dynamic stress. Consequently, this rear part can work with a maximum admissible dynamic stress, increased and, therefore, at higher vibratory speeds without risk of degradation thereof. In this way, the vibratory capacity of the rectifier, that is to say its capacity to withstand a given aerodynamic excitation, is improved.

Said means of attachment to the outer casing comprises, with respect to the direction of the flow passing through the blades, a front peripheral rim located at the level of the upstream transverse face of the outer shell of said sectors, and a rear peripheral rim offset from the downstream transverse face of the outer shell and located, in projection, between the leading and trailing edges of the blades.

Said offset rear peripheral rim is located, in projection, in the middle of the blades, between their leading and trailing edges. Thus, the static stress is not only offset from the rear of the shell but is also reduced since the volume of material, in which the forces generating the static stress pass between the rear flange, the shell and the blades, is greater, the thickness of the blades being at this level the widest.

In an alternative inventive embodiment, said means for attaching to the outer casing comprises an annular flange provided at the periphery of the outer shell, and located projecting between the leading and trailing edges of the blades. The results in terms of the dissociation of the stresses are similar to the previous embodiment, the rear of the outer shell no longer being subjected to the static stress.

Said attachment flange is located, in projection, in the middle of the leading and trailing edges of the blades, resulting in the same advantage as previously in terms of reducing the static stress by increasing the volume of material.

In particular, said rear peripheral rim or said flange may extend continuously or discontinuously over all of the sectors.

• La figure 1 représente, en coupe longitudinale schématique, une partie d'un compresseur haute pression d'une turbomachine, avec un étage de stator à redresseur fixe conforme à l'invention suivi d'un étage de rotor.
• La figure 2 est une vue en perspective partielle du redresseur de la figure 1, avec le rebord d'accrochage arrière décalé axialement.
• La figure 3 est une de dessus du redresseur de la figure 2.
• La figure 4 est une vue en perspective d'un autre exemple de réalisation du redresseur conformément à l'invention.

The figures of the appended drawing will make it easier to understand how the invention can be implemented. In these figures, identical references designate similar elements.

• The figure 1 shows, in schematic longitudinal section, a part of a high pressure compressor of a turbomachine, with a stator stage with fixed rectifier according to the invention followed by a rotor stage.
• The figure 2 is a partial perspective view of the rectifier of the figure 1 , with the rear hooking flange axially offset.
• The figure 3 is a top of the rectifier of the figure 2 .
• The figure 4 is a perspective view of another embodiment of the rectifier according to the invention.

Compressor part 1 shown on figure 1 is that of a high-pressure compressor of an A-axis turbine engine for an aircraft, and it shows a stator stage 2 forming the fixed rectifier 3, downstream of which is a rotor stage 4 of this compressor. Usually, the stator rectifier 3 is sectorized, that is to say composed of several sectors 5 successively mounted one after the other in an annular outer casing 6 for receiving and maintaining these sectors in position by a attachment or hooking means 7 to thus form the rectifier as a whole.

A single sector 5 is illustrated in the figures and reference will be made, in the following description, to it, bearing in mind that it applies to all of the sectors, in this case to the rectifier 3 itself. said in its entirety. Each sector 5 of the rectifier comprises an outer shell 8 with a cylindrical wall 9 and an inner shell 10 also with a cylindrical wall 11, which are concentric with respect to the axis A and between which are provided blades 12 through which the flow of the flow passes. primary air F issuing upstream from the fan and moving downstream towards the combustion chamber. For the sake of representation, the distance separating the axis A from the internal ferrule 10 of the rectifier has been reduced. Regarding the internal ferrule, we see on the figure 1 that the outside thereof is covered in a known manner with an abradable coating 25 against which a multi-lip seal 26 provided on the rotor stage 4 is applied.

The heads 13 and the feet 14 of the blades 11 are fixed, for example by soldering, respectively to the walls 9 and 11 of the outer shell 8 and of the inner shell 10. The blades 12 extend over almost the entire width of the blades. ferrules along the axis A, so that the leading edge 15 and the trailing edge 16 of the blades along the flow F are located close to the transverse end faces 17 and 18, respectively front and rear (or upstream or downstream ), walls 9, 11 of the cylindrical shells.

On the outer periphery of the side wall 9 of the outer shell 8 is also provided the attachment means 7 with the outer casing 6 and this means comprises, in this example, a slide-slide assembly. For this, the attachment means 7 is defined, in this first embodiment of the rectifier, by two angled hooking edges, respectively front or upstream 19 and rear or downstream 20 according to the direction of flow F, forming a slide, and which engage, as shown schematically by the figure 1 , in receiving and holding slots 21, forming a slide, of the outer casing 6 which surrounds the sectors 5 of the rectifier 3.

We see on the figures 1 to 3 , that the front hooking rim 19 is located substantially in line with the front transverse face 17 of the outer shell 8, while the rear hooking flange 20 is for its part, in accordance with the invention, to distance from the rear transverse face 18 of the shell, substantially in the middle of the cylindrical side wall 9 and, therefore, directly above the blades 12. Dimensionally, this rear flange 20 is arranged to be located, in projection, in the middle of the blades 12, where the latter are thicker, as shown in the figure 3 .

By this axial offset towards the front edge 19 of the rear edge 20 (initially located at the level of the rear face 20 of the outer shell, i.e. near the trailing edge 16 of the blades, as shown in its representation in dotted lines, reference 20 ' on the figure 2 ) substantially up to the middle of the side wall 9 of the outer shell, all the aerodynamic forces (flow F passing through the rectifier) and the mechanical forces transmitted by the outer casing 6 will pass through the sectors 5 by the connecting radius defined by the rear bent flange 20, and the heads 13 of the blades, in their middle, and will therefore be taken up by a volume of material most important. Consequently, the maximum static stress resulting from these forces on the stator will be lower.

Therefore, as the rear part or end 22 of the side wall 9 of the outer shell 8 (part 22 ending in the rear transverse face 18) is no longer subjected to this maximum static stress, it can take up a maximum dynamic stress. admissible higher, since the latter always remains localized in this rear part 22. Consequently, by the separation of the stresses and the shift of the maximum static stress vis-à-vis the maximum dynamic stress, the vibratory capacity of the rectifier 3 and therefore of the stator stage 2, is improved, that is to say its capacity to withstand a given aerodynamic excitation.

Another embodiment of the sectorized rectifier 3 according to the invention is shown opposite the figure 4 . In this perspective view of a sector 5 of the rectifier, we find the concentric rings respectively outer 8 and inner 10 between which are arranged the blades 12. On the outside of the outer ring 8 is provided the attachment means 7 to the outer casing not shown in this figure. This attachment means 7, unlike the previous embodiment, comprises a single annular flange 23 projecting radially from the side wall 9 of the cylindrical shell 8 and which is regularly provided, at the periphery, with fixing holes 24 to the receiving casing for the passage of bolts or the like.

According to the invention, the flange 23 is arranged between the upstream 17 and downstream 18 transverse faces of the shell wall and in the middle of the blades, between the leading 15 and trailing 16 edges of the blades while being, in projection, substantially located at their widest thickness.

Such an embodiment with a central flange 23 provides results similar to the previous embodiment with two hooking flanges 19, 20. The static stress generated by the various forces is localized at the level of the central flange 23 of the shell and the thick parts of the rings. blades and is therefore separated from the maximum dynamic stress which occurs in the rear part 22 (then freed from the static stress) of the wall 10 of the shell 8. Consequently, the maximum admissible dynamic stress can be increased without harming the integrity of rectifier 3, allowing higher vibration levels on the motor.

Furthermore, the front 19 and rear 20 flanges, as well as the flange 23, can be produced continuously or discontinuously on the periphery of the side wall 11 of said outer shell 8.

Claims (3)

1. Sectorised turbine engine compressor rectifier (3), of the type comprising assembled sectors (5) forming two concentric outer (8) and inner (10) shrouds having cylindrical walls (9, 11) comprising respectively upstream and downstream transverse faces (17, 18), blades (12) being arranged between the outer (8) and inner (10) shrouds, with their leading (15) and trailing (16) edges near, respectively, to the upstream and downstream transverse faces (17, 18) of the shrouds, the outer shroud (8) being equipped externally with a means of attachment (7) with an outer fan duct (6) that houses said sectors,
   characterised by the fact that said means of attachment (7) is axially offset from the rear transverse face (18) of the outer shroud (8) and arranged to absorb the static forces between the outer fan duct (6), and the rectifier, said means of attachment (7) to the outer fan duct comprising, with respect to the direction of the flow traversing the blades,

   - either a front peripheral angled fastening edge (19), located at the upstream transverse face (17) of the outer shroud of said sectors, and a rear peripheral angled fastening edge (20) offset from the downstream transverse face (18) of the outer shroud and located, in projection, in the centre of the blades, between the leading (15) and trailing (16) edges thereof and substantially in the centre of the cylindrical wall (9) of the outer shroud (8), the front (19) and rear (20) peripheral angled fastening edges forming a slider being configured to be engaged in the receiving and holding slots (21) forming a sliding joint,

   - or an annular flange (23) provided at the periphery of the outer shroud (8), and located in projection directly above the blades (12) and in in the centre of the blades, between the leading and trailing edges of the blades (12), the annular flange (23) being regularly equipped with, at the periphery, fixing holes (24), and attachment bolts or similar traversing the fixing holes (24) to attach the annular flange (23) to the outer fan duct (6).
2. Rectifier according to claim 1, wherein said rear peripheral angled fastening edge (20) or said annular flange (23) extends continuously or discontinuously along all of the sectors (5).
3. Rectifier according to claim 1 or 2, wherein the front (19) and rear (20) peripheral angled fastening edges are configured to be engaged in the receiving and maintaining slots (21) of the outer fan duct (6) which surrounds the sectors (5) of the rectifier.

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