WO2016146920A1

WO2016146920A1 - Assembly with sealing plates for gas turbine

Info

Publication number: WO2016146920A1
Application number: PCT/FR2016/050552
Authority: WO
Inventors: Olivier Jean Daniel Baumas; Nicolas Daniel DELAPORTE; Anthony Pierre BEGUIN
Original assignee: Snecma
Priority date: 2015-03-17
Filing date: 2016-03-11
Publication date: 2016-09-22
Also published as: FR3033827A1; FR3033827B1

Abstract

The invention relates to an assembly for a gas turbine, including stationary vanes forming a distributor (5) in which the adjacent side surfaces (171, 173) are placed end-to-end and which comprise slots (31a, 33a) made facing one another in the adjacent side surfaces of two consecutive stationary vanes, and sealing plates (35) arranged individually in the facing slots of two consecutive stationary vanes. At least some of the sealing plates have a natural curve and are wedged and deformed under bending stress in the slots.

Description

Sealing pad assembly for a gas turbine

The present invention relates to the general field of devices providing a sealing function in a turbomachine, in particular an airplane turbojet or turboprop engine.

The turbines of such machines typically comprise a plurality of stages each comprising an annular row of stationary vanes carried by a casing of the turbine and an annular row of vanes rotatably mounted about a central axis of rotation.

Radially, in delimitations of the circulating gas vein, in particular the vanes have areas called platforms where two successive blades are adjacent.

Annually extending, these platforms are sectored, that is to say that they each consist of a plurality of segments joined end to end, along a circumference, around the central axis of rotation.

It is necessary to provide at least a relative sealing between the adjacent segments of these platforms in order to prevent air leakage that is particularly detrimental, in particular to the proper cooling of these segments and which may also lead to a decrease in engine performance, damage to parts downstream.

For this purpose, it is known to interpose tabs or sealing plates between the adjacent segments. Such tongues or plates are generally housed in substantially axial slots and / or radial formed opposite vis-à-vis in the adjacent side faces of the segments. They thus make it possible to obstruct the clearance existing between two adjacent segments in order to limit the air leaks irrespective of the thermal expansion undergone by the segments.

Thus, for example, there is known a unit for a turbine of an aeronautical turbine engine in which a gas circulates, comprising: a plurality of stationary vanes forming a distributor whose adjacent lateral faces are placed end to end and which comprise slots facing each other in the adjacent lateral faces of two successive fixed vanes, said vanes extend radially around of an axis and have external and internal platforms respectively delimiting, radially outer and inner, a vein for a gas flowing through the turbine,

and sealing plates disposed individually in the slots facing two successive fixed vanes, said slots being elongated in a general direction from upstream (AM) downstream (AV) with respect to a circulation of the gas in the turbine,

at least some of the sealing plates having at least one natural curvature and being wedged, deformed under mechanical stress, in the slots.

A persistent problem remains, however, related to a pronounced wear of these sealing pads, see their absence: The wear reduces the size of the pads that can then go out of their homes (slots).

One solution proposed here is that:

the turbine is that of an aeronautical turbine engine,

and, in a said slot, said stress-deformed sealing pad is, by pressing against walls of said slots, disposed away from a downstream end of the slot.

Thus, one will avoid, or at least limit, the typical wear in bottom of slots.

Mounting these curved plates in the current sealing slots designed for flat plates will allow mounting prestressing without having to change the slots.

Thus locked under tension, platelets will be less sensitive to the conjunction of vibrations and temperature, typical causes of wear. Indeed, pushed to the bottom of their homes by the force of the air, the current pads vibrate and come to wear in the bottom of distributors.

Favorably, some at least platelets will have a length and several inverse curvatures along this length.

Thus (at least) doubly curved, the plates can not only be mounted in prestressing in their receiving slots, but maintain a preload even in case of slight wear of a wafer end.

For the sake of an optimized balance efficiency / ease of manufacture / cost, it is recommended that at least some of the pads have two reverse curvatures.

Thus doubly curved in their length, the plates can not only be mounted in prestressing in their receiving slots, but maintain a preload even in case of slight wear of a platelet end.

And by planning:

- along said length, only two curved vertices, respectively located about 1/4 and about 3/4 of this length,

and / or platelets having a maximum deflection of 1 mm to +/- 10% at the location of these two apices,

the constraints on the platelets will be balanced and will continue to tend towards the aforementioned optimized equilibrium.

In addition, in order to combine suitable flexibility and resistance over time, it is recommended that the inserts be made of nickel-cobalt hot-melt alloy with a thickness of 0.2mm to +/- 10%.

It should also be noted that, on the basis of these characteristics, it has been possible to propose a solution avoiding to change the parts in interface, while keeping the dimensions of the current pads used by the depositor on the engines concerned (these current pads having been defined according to the most unfavorable min / max geometry of the distributor grooves). It has also been possible to conserve a material identical to the current version: DMD0408 (CoCrNi22W), Alloy above resistant to hot base Nickel or Cobalt.

Other features and advantages are further detailed below, with reference to the accompanying drawings in which:

- Figure 1 is a partial schematic axial axial sectional view of a turbomachine portion, it being specified that the solution applies both to one or more low pressure stages to one or more high pressure stages.

FIG. 2 is a local perspective view, along the arrow II of FIG. 1, of a part of the dispenser schematized in FIG. 1 and carrying the sealing means of the invention;

3.4 are enlarged views, in median axial sections, of a radially outer portion of one of the vanes of the distributor of FIG. 2, mounted, in each case with a wafer embodiment,

and FIG. 5 is a side view of one of the embodiments of the wafer shown as a relevant sealing means in the invention.

In Figure 1 is more precisely schematically a turbine part 1 of an aerospace turbine engine.

In the gas turbine 1, there is seen a rotor 3 and a stator, also called a distributor, 5 belonging to the same stage of the turbine which may comprise several, successively, parallel to the axis 7 about which the blades of the turbine are rotating. rotor 3.

In this description is "radial" what is (substantially) radiating vis-à-vis the axis 7 and is "axial" which extends (substantially) following, or parallel to, the axis 7.

The rotor 3 defines a wheel having a plurality of blades 9 fixed to a disc 11 and rotatably mounted each around the axis 7, here axially downstream of the distributor.

Each blade 9 comprises a blade 13 and a radially inner platform 15. A ring 16 sealing the blade against the outside air is arranged around the blades 13, radially outside thereof, to limit the fact that the air in the vein does not bypasses the blading.

The stator 5 comprises a plurality of stationary blades 17 which collectively form an annular structure, centered on the axis 7, and individually a ring segment (see FIG. 2).

Each segment 17 comprises one or more blades 19 extending radially between an external platform 21 and an internal platform 23.

The inner platforms 23 are fixed to a fixed support structure, or stator, and the outer platforms 21 are supported by the casing, or casing, 27 arranged radially outside (around) of the stator 5. This may be specific to the high pressure part or stage 1 of a low pressure turbine. On the other stages, the vanes can be fixed at their outer part 21 to the turbine casing and the inner platform 23 can not be maintained. The outer and inner platforms 21, 23 collectively form the outer and outer limits respectively of the vein 29 of the gas flowing through the turbine, this vein being also limited radially by the inner platform 15 and the outer seal 16 , at the location of the rotor 3.

In FIG. 2, it can be seen that adjacent lateral faces 171, 173 of the stationary blades 17 of this distributor belonging to two successive sectors of blades 17a, 17b are placed end to end, circumferentially, around the aforementioned axis 7. each side face (see for example that marked 175 sector 17a, opposite the face 171) are formed one or more slots, here 31a, 33a.

In this case, two sets of slots have been provided, in the lateral faces of the respectively external and internal platforms 21, 23.

In the corresponding adjacent lateral faces, such as here 171 and 173, of two internal platforms (and / or external) of two circumferentially successive fixed blades, the considered slits, such as those indicated 31b, 31c and 2c, are located in vis-a-vis. And in each double slot opposite two successive sectors of this distributor, is housed (at least) a sealing plate 35 intended to obstruct the clearance between two adjacent segments in order to limit air leakage, whatever the thermal expansion experienced by the segments.

However, such pads are highly stressed in this environment where vibration and temperature are critical for their wear.

It is therefore in particular to limit premature and inappropriate wear of these wafers 35 that it is expected that they individually have a natural curvature (see Figure 2, left wafer at rest, out of its receiving slots) and are stuck in their receiving slots (see right figure 2, for example in the double slot vis-à-vis 31b, 31c, but also Figures 3 and 4), being deformed under mechanical stress, here bending.

Curved, the plates 35 will thus be able to be mounted in prestressing in the receptive slots typically not curved (planes) of conventional distributor segments.

Thus blocked under tension, platelets will be less sensitive to the conjunction of vibrations and temperature.

In FIGS. 3 and 4 (where the drawings are less symbolic than in the preceding figures), a radially outer portion of a fixed blade 17 and two types of curved plates 35 are shown, which can also be seen respectively in FIG. left and figure 5, at rest.

Figure 3, the outer platform 21 is provided with two tabs, respectively upstream and downstream, 211, 213, connecting (fixing) to the housing 27 and which extend radially outwardly.

The slot 31 d, formed in the side face 177 of the outer platform 21, is extended by or comprises, in the example, two portions 311 d, 313d transverse to an intermediate portion 315d. The intermediate portion 315d extends into the platform 21 which is slightly inclined with respect to the axis 7. The two portions 311 d, 313d cross respectively extend in the upstream leg (AM) 211 and in the downstream leg (AV ) 213.

In the example, only the part 315d of the slot 31 d houses, over part of its width or depth, a curved plate according to an embodiment of the invention and marked 35a, by difference with the one with multiple curvatures 35b Figures 4 and 5.

In this example, the wafer 35a, of length L, has a single curvature, with a vertex centered at mid-length, at 350a in FIG.

Under bending stress in the contiguous slots which receive it, the plate bears at its ends and at 350a against two opposite walls which limit them internally, as illustrated.

Figures 4,5, the wafer 35b has the same length L and several inverse curvatures, two in this case, along this length

This solution will promote preservation of the prestressing, even in the event of slight wear of one end of platelets, in the slots.

For the sake of an optimized balance efficiency / ease of manufacture / cost, the wafer 35b has two inverse curvatures, with a point of inflection at mid-length.

In fact, she presents:

according to the length L, only two curved peaks 350b, 351b, respectively situated at approximately 1/4 and approximately 3/4 of this length,

and a maximum height of curvature, or arrow, h of 1 mm to +/- 10% at the location of these two vertices.

It will have been understood that this arrow h is, perpendicular to the length L and the jettison I, the distance between the vertices, or that between one of the vertices and one of the ends, as illustrated in FIG.

To also combine a suitable flexibility and a resistance in time, it is recommended that the pads 35, 35a, 35b are in Nickel-Cobalt hot-resistant alloy with a thickness of 0.2mm to +/- 10%.

Overall, each wafer will be favorable as a parallelepiped thin plate-shaped body, possibly beveled angles.

It should be considered that, when dimensioned, the aforementioned curved plates could be usefully introduced into the "radial" slots 311d, 313d, and be provided both at the external platforms 21 and in the interior 23.

3 and 4, it will also be noted that the stress engagement of the plates allows, in particular, in the "axial" slots 315d extending along the length of the platforms 21 (like those 31a, 33a in FIG. thus differently "radial" slots of the transverse portions 311 d, 313d), the plates are not plated sloping downstream bottom. Figures 3 and 4, a space 31 Od remains between the downstream end of the wafer and the downstream wall of the slot considered.

Thus, in the slot 315d thus elongated generally in a direction from upstream (AM) downstream (AV) with reference to the flow direction of the gas in the vein 29, the sealing plate disposed therein is by pressing against walls of the slot, kept away from a downstream end 3150d of the slot, even if, in operation, the plates will be plated, despite the prestressing, at the bottom of the slots.

Claims

1. Assembly for a turbine of an aeronautical turbine engine where a gas circulates, comprising:

a plurality of stationary vanes forming a distributor (5) whose adjacent lateral faces (171, 173) are placed end to end and which comprise slots (31a, 33a, 315d) practiced vis-à- screw in the adjacent lateral faces of two successive fixed vanes, said blades extend radially about an axis (7) and have external and internal platforms (21, 23) delimiting radially outer and inner respectively, a vein (29) for a gas flowing through the turbine,

and sealing plates (35, 35a, 35b) arranged individually in the slots (31 a, 33 a, 315 d) opposite two successive fixed vanes, said slots being elongated in a general direction going upstream (AM) downstream (AV) with respect to a circulation of gas in the turbine,

at least some of the sealing plates (35, 35a, 35b) having at least one natural curvature and being wedged, deformed under mechanical stress, in the slots characterized in that:

the turbine is that of an aeronautical turbine engine,

and in a said slot, said pressure-deformed sealing plate (35, 35a, 35b) is, by pressing against walls of said slots, disposed away from a downstream end (3150d) of the slot.

2. The assembly of claim 1, wherein at least some of the wafers (35, 35a, 35b) have a length (L) and several inverse curvatures along this length.

3. The assembly of claim 2, wherein at least some platelets have two inverse curvatures along said length, with vertices (350b, 351b) respectively about 1/4 and about

3/4 of this length.

4. The assembly of claim 2 or 3, wherein at least some platelets have a maximum deflection (h) of 1 mm to +/- 10% at the point of the vertices (350b, 351b).

5. An assembly according to one of claims 1 to 4, wherein the plates (35, 35a, 35b) are hot-nickel-based alloy of nickel and cobalt, with a thickness of 0.2mm to +/- 10%.

6. Assembly according to one of claims 1 to 5, wherein the blades belong to a turbine turbine low pressure (1) of the turbomachine.