EP3906357B1 - Turbine nozzle, turbine comprising said nozzle and turbomachine comprising said turbine - Google Patents

Description

GENERAL TECHNICAL AREA

The present invention relates to a distributor for a low or high pressure turbine, a low or high pressure turbine comprising this distributor and a turbomachine, such as a turbojet or an airplane turboprop, comprising the aforementioned turbine.

STATE OF THE ART

Some turbomachines include a low pressure turbine and a high pressure turbine, which recover part of the energy released by the combustion of fuel to drive respectively a low pressure compressor and a high pressure compressor, located at the inlet of turbomachine air.

On the figure 1 attached, one can see a low pressure turbine 1 with several stages 10, each stage 10 comprising successively a distributor 2 and a rotor wheel 3, from upstream to downstream with respect to the direction of flow of the air in the turbine (arrow V: i.e. from left to right on the figure 1 ). All the rotors are fixed on a shaft not shown in the figures and driven simultaneously in rotation.

The low pressure turbine 1 has a longitudinal axis X-X'.

Each distributor 2 is sectorized, that is to say formed of several angular sectors 20 of distributor, arranged circumferentially end to end and assembled.

Each angular sector of distributor 20 comprises two platforms in portion of an arc of circle, arranged coaxially one inside the other and interconnected by radial or substantially radial blades 201. These platforms delimit between them the annular flow path of the gases in the turbine 1.

The external platform 202 comprises hooking means on an external casing 100 of the turbine 1. The internal platform 203 extends towards the inside of the turbine by a radial foot 204 which ends in a base 205.

This base 205 carries on its radially inner face, elements made of abradable material 206. This abradable material is in the form of a honeycomb structure. The elements made of abradable material 206 cooperate with annular wipers 30 carried by the neighboring rotor 3, to form seals of the “labyrinth seal” type. Indeed, in operation and under the effect of heat, the wipers 30 and the internal platform 203 expanding and approaching, the wipers 30 dig grooves in the abradable material 206. There thus exists between the grooves and the wipers, a small game that constitutes this maze joint. This clearance induces the performance of the stream of hot air flowing through the turbine.

The honeycomb 206 is brazed onto the base 205 of each angular sector 20 of the distributor, then is machined again. Currently, this material is machined by spark erosion (known by the acronym EDM for “Electrical Discharge Machining” ) , which is an expensive technique and also requires specific and expensive controls.

In addition, in the event of significant wear of the elements made of abradable material, it is necessary to replace them with new ones during maintenance operations. It is therefore necessary to dismantle each angular sector of the distributor, to machine the worn abradable elements to remove them and to braze new abradable elements on the internal bases of said angular sectors of the distributor. This replacement operation is therefore long and expensive.

Furthermore, the internal platform 203, the foot 204 and the base 205 of each sector 20 have sealing slots 207, which open onto each of the end faces of a sector 20 intended to come into contact with the end faces of the adjacent distributor sector 20. An inter-sector sealing tab (not shown in the figures) is engaged in each sealing slot 207, so as to overlap the space existing between two neighboring distributor sectors 20 and thus to stop or limit leaks. inter-sector air.

The production and manufacture of the sealing slots 207 and the mounting of the inter-sector sealing tabs are very expensive and time-consuming. The slots 207 are also difficult to size and there is a significant risk that the sealing tabs will be dislodged from the sealing slots 207 and get lost in the air stream, resulting in air leaks and possible impacts on other parts of the turbine.

We already know from the document US 2004/169122 , a distributor for a turbine, comprising several angular sectors of distributors, each angular sector comprising two respectively internal and external sectors of platforms, in the shape of an arc of a circle, coaxial, interconnected by several radial or substantially radial blades.

Each internal platform sector is integral with a radially internal foot.

This distributor also comprises an annular ferrule on which said angular distributor sectors are fixed circumferentially end to end, this ferrule comprising a cylindrical ring whose radially inner face bears an abradable material.

However, this document neither describes nor suggests the mode of attachment by dog clutching of the foot of a platform sector with the ferrule.

PRESENTATION OF THE INVENTION

The object of the invention is to propose a turbomachine distributor which solves the aforementioned drawbacks of the state of the art.

More specifically, the object of the invention is to provide a turbomachine distributor which is simple and less expensive to produce and to assemble, while reducing air leaks in the vein.

Another object is to simplify the maintenance of the distributor.

To this end, the invention relates to a distributor for a turbine, comprising several angular sectors of distributors, each angular sector comprising two respectively internal and external sectors of platforms, in the form of an arc of a circle, coaxial, interconnected by several radial or substantially radial blades, each internal platform sector being integral with a radially internal foot, this distributor comprising an annular shroud on which said angular distributor sectors are fixed circumferentially end to end, this shroud comprising a cylindrical ring whose the radially inner face carries an abradable material.

In accordance with the invention, the radially internal foot of each internal platform sector comprises a tongue, which extends radially inward from said foot, and which extends circumferentially over part of the length of said foot, the radially outer face of said cylindrical ring carries an outer radial wing, provided with a plurality of L-shaped lugs, one of the so-called "fixing" legs of which is integral with the outer radial wing and extends perpendicularly to a radius of the ring and parallel to the longitudinal axis X1-X' 1 of said ring and whose other branch, called "retaining", extends opposite this external radial wing and at a short distance from it, so as to provide with it a slot for receiving said tongue of each angular sector of the distributor and this slot is open at one of its ends longitudinal to allow the engagement of said tongue, so as to ensure the fixing by dog clutching of said ferrule on each angular sector of the distributor.

Thanks to these characteristics of the invention, it is no longer necessary to have sealing slots at the internal ends of the platform sectors, nor of sealing tabs therein, since the annular shell over 360 ° provides this seal. This reduces flow losses in the vein in this zone.

Finally, the manufacturing costs of the angular distributor sectors, their assembly and their maintenance are also reduced.

• ladite languette du pied radialement interne s'étend circonférentiellement sur un tiers de la longueur dudit pied ;
• ladite languette s'étend circonférentiellement au centre du pied radialement interne de chaque secteur de plate-forme interne ;
• l'extrémité de la branche de retenue est munie d'un ergot saillant en direction de l'aile radiale externe, de façon à retenir circonférentiellement ladite languette lorsque celle-ci est engagée dans la fente de réception de la languette ;
• la branche de retenue et l'aile radiale externe sont jointes par une goupille, un rivet et/ou une soudure ;
• le distributeur comprend au moins une tôle d'étanchéité, en au moins un segment, à section transversale en L ou sensiblement en L, fixée sur le pied radialement interne d'un secteur angulaire de distributeur(6), de façon à s'étendre au moins en regard de l'intersection entre deux secteurs angulaires de distributeur voisins ;
• le distributeur comprend au moins une tôle de protection thermique, en au moins un segment, à section transversale en L ou sensiblement en L, fixée sur l'anneau cylindrique de la virole.

According to other advantageous and non-limiting characteristics of the invention, taken alone or in combination:

• said radially inner foot tongue extends circumferentially over one third of the length of said foot;
• said tongue extends circumferentially at the center of the radially inner foot of each inner platform sector;
• the end of the retaining branch is provided with a lug projecting in the direction of the outer radial wing, so as to retain said tongue circumferentially when the latter is engaged in the slot for receiving the tongue;
• the retaining branch and the outer radial wing are joined by a pin, a rivet and/or a weld;
• the distributor comprises at least one sealing sheet, in at least one segment, with L-shaped or substantially L-shaped cross-section, fixed to the radially internal foot of an angular sector of the distributor (6), so as to extend at least opposite the intersection between two neighboring distributor angular sectors;
• the distributor comprises at least one thermal protection plate, in at least one segment, with an L-shaped or substantially L-shaped cross-section, fixed to the cylindrical ring of the shroud.

The invention also relates to a turbomachine turbine comprising the aforementioned distributor and a turbomachine, such as a turbojet or an airplane turboprop, which comprises the aforementioned turbine.

DESCRIPTION OF FIGURES

Other characteristics and advantages of the invention will appear from the description which will now be made of it, with reference to the appended drawings, which represent, by way of indication but not limitation, various possible embodiments.

• [Fig. 1] est une vue en coupe longitudinale d'une turbine basse pression de l'état de la technique,
• [Fig. 2] est une vue en perspective de la virole du distributeur conforme à l'invention,
• [Fig. 3] est une vue de détail de la figure 2,
• [Fig. 4] est une vue de détail de la figure 3,
• [Fig. 5] est une vue en perspective d'un secteur angulaire de distributeur conforme à l'invention,
• [Fig. 6] est une vue en perspective d'une portion de virole et d'un secteur angulaire de distributeur assemblés conformément à l'invention,
• [Fig. 7] est une vue schématique en coupe axiale de la virole, de la partie intérieure d'un secteur angulaire de distributeur et d'une tôle de protection assemblées, la tôle étant réalisée selon un premier mode de réalisation,
• [Fig. 8] est une vue schématique en coupe axiale de la virole, de la partie intérieure d'un secteur angulaire de distributeur et d'une tôle de protection assemblées, la tôle étant réalisée selon un deuxième mode de réalisation,
• [Fig. 9] est une vue en perspective d'un secteur angulaire de distributeur, de deux tôles de protection et d'une partie de la virole assemblés, qui constituent une partie d'un distributeur conforme à l'invention,
• [Fig. 10] est une vue de détail et en perspective de deux tôles de protection différentes assemblées respectivement sur la virole et sur un secteur angulaire de distributeur,
• [Fig. 11] est une vue de détail et en perspective d'une variante de réalisation d'une tôle de protection assemblée sur un secteur angulaire de distributeur, et
• [Fig. 12] est une vue de détail et en perspective d'un mode de fixation d'un secteur angulaire de distributeur sur la virole.

In these drawings:

• [ Fig. 1 ] is a view in longitudinal section of a low pressure turbine of the state of the art,
• [ Fig. 2 ] is a perspective view of the distributor shell according to the invention,
• [ Fig. 3 ] is a detail view of the picture 2 ,
• [ Fig. 4 ] is a detail view of the picture 3 ,
• [ Fig. 5 ] is a perspective view of an angular sector of a dispenser according to the invention,
• [ Fig. 6 ] is a perspective view of a ferrule portion and an angular distributor sector assembled in accordance with the invention,
• [ Fig. 7 ] is a schematic view in axial section of the ferrule, of the inner part of an angular sector of the distributor and of an assembled protective sheet, the sheet being made according to a first embodiment,
• [ Fig. 8 ] is a diagrammatic view in axial section of the ferrule, of the inner part of an angular sector of the distributor and of an assembled protective sheet, the sheet being made according to a second embodiment,
• [ Fig. 9 ] is a perspective view of an angular distributor sector, two protective plates and part of the shroud assembled, which constitute part of a distributor according to the invention,
• [ Fig. 10 ] is a detail and perspective view of two different protective plates assembled respectively on the shell and on an angular sector of the distributor,
• [ Fig. 11 ] is a detail and perspective view of an alternative embodiment of a protective plate assembled on an angular distributor sector, and
• [ Fig. 12 ] is a detail and perspective view of a method of fixing an angular distributor sector on the ferrule.

DETAILED DESCRIPTION OF THE INVENTION

The distributor according to the invention is referenced 4 and comprises an annular shell 5, on which are fixed several angular distributor sectors 6. Only part of the distributor 4 is visible on the figure 9 .

The annular shell 5 will now be described in more detail in connection with the figures 2 to 4 . It extends over 360° and has a longitudinal axis X1-X'1.

The annular shell 5 comprises a cylindrical ring 50 (or tube) of small width relative to its diameter, of small thickness and of longitudinal axis X1-X'1.

This ring 50 has a radially inner face 51 and a radially outer face 52.

As seen best on the figures 7, 8 And 11 , the inner face 51 carries an abradable material 53 in one or more elements. This abradable material 53 is preferably a honeycomb structure. It is brazed onto the ring 50 and resumed machining as previously described for the abradable material 206. This abradable material 53 is also cylindrical.

The outer face 52 of the ring 50 comprises several first mechanical fixing members, distributed around its periphery and intended to cooperate with second complementary mechanical fixing members, carried by each of the angular sectors 6.

According to a preferred embodiment of the invention, these mechanical fasteners are of the "clutch" type and allow coupling of the ferrule 5 and the distributor sectors 6 by the engagement of tabs in the slots for receiving these tabs.

On the figures 3 and 4 , it can be seen that the shroud 5 is provided with a radial wing 54, which extends radially outwards, from the outer face 52 of the ring 50. This wing 54 is annular and extends over the entire periphery of the ring 50. It has a rear face 541 and an opposite front face 542.

During assembly of the distributor 4, the rear face 541 is preferably oriented downstream of the turbine.

A plurality of L-shaped tabs 55 are integral with the wing 54 and are uniformly distributed over the entire circumference of the latter.

Each leg 55 is also curved and has the general shape of an arc of a circle, the circle of which is coaxial with the ring 50 but with a radius greater than the radius of the ring 50. The leg 55 matches the shape of the ring 50.

Each L-shaped leg 55 has a short branch 551, called the “fixing branch” and a long branch 552, called the “retaining branch”. The fixing arm 551 extends perpendicular to a radius of the ring 50 and parallel to the longitudinal axis X1-X'1 of said ring. The retaining branch 552 extends circumferentially and at a short distance from the rear face 541 of the wing 54, so as to define therewith a slot 553.

The long branch 552 has a front face 554 which extends opposite and parallel to the rear face 541 of the wing 54.

Part of the branch 551 constitutes the bottom 555 of the slot 553. The slot 553 is open opposite the bottom 555, between the free end of the long branch 552 and the wing 54.

Advantageously, the long arm 552 has at its free end a lug 556 (see figure 4 ), which protrudes from the front face 554, in the direction of the rear face 541 of the wing 54, so as to only partially close the slot 555.

Branch 552 is advantageously slightly flexible.

Note, as it appears better on the picture 2 , that the ring 50 can optionally be split, (see the longitudinal slot 500). This gives it a certain flexibility and facilitates the assembly of the distributor 4.

The different parts 50, 54 and 55 of the ferrule 5 are preferentially in one piece (made in one piece). The ferrule 5 can be manufactured for example by machining or by additive manufacturing.

The ferrule 5 is preferably made of metal.

An example embodiment of an angular sector 6 of a distributor will now be described in conjunction with the figures 5 to 8 .

This sector 6 comprises, in a conventional manner, two angular sectors of platforms in an arc of a circle, coaxial, namely an external platform sector 61 and an internal platform sector 62, interconnected by several blades 63 radial or substantially radial.

The different angular sectors 6 are assembled around the shroud 5, end to end circumferentially, so that the different angular sectors of the external platform 61 together form the external platform of the distributor 4 and that the different angular sectors of the platform internal form 62 together form the internal platform of the dispenser 4.

In accordance with the invention, the angular sector of the internal platform 62 is integral with a foot 621, called "internal radial foot", because it extends radially from the internal face of the said internal platform sector, in the direction from inside the dispenser 4.

As can be seen on the figure 5 , the internal radial foot 621 is curved, seen from the front. It is extended radially inwards by an internal radial tab 622, also curved in front view.

Preferably, the tongue 622 is centered in length with respect to the internal radial foot 621, so as to avoid the cantilever.

The length of the tongue 622 is preferably reduced to what is necessary for it to absorb the forces. Advantageously, the tongue 622 has a tangential length L1, equal to approximately one third of the tangential length L2 of the foot 621.

According to the variant embodiment represented here, the foot 621 supports a single tab 622. However, depending on the dimensions of the angular sectors of the distributor 6, it is possible to have several tabs 622 on each foot 621.

Preferably, and as it appears better on the sectional views of the figures 7 and 8 , the tongue 622 is thinner than the foot 621, so that it can form with this foot 621, i.e. a shoulder 623 which opens onto the front face 6211 of the foot 621 (see figure 7 ), or a shoulder 624 which opens onto the rear face 6212 of the foot 621 (see figure 8 ).

Advantageously and in order to further improve the sealing, one or more sealing plates 7 can be fixed on the different angular sectors of the distributor 6.

As can be seen on the figure 9 , the sheet 7 is formed of a profile slightly curved in an arc of a circle, in a circle whose radius is coaxial with the circle of the internal platform 62 in an arc of a circle, so as to match the shape of this platform.

As can be seen on the figures 7 and 8 , the sheet 7 has a substantially L-shaped cross-section, with a fixing flank 71 and a protective flank 72.

The fixing flank 71 is intended to be fixed on the foot 621, for example by brazing or welding, this brazing or this welding being able to be carried out punctually or over the entire length of the sheet.

Each flank 71, 72 may optionally have folds, which define different sides, so as to adapt to the different shapes of feet 621, as can be seen for example on the figures 7 and 8 .

It is possible to have several segments of sealing plates 7, as shown in the figure 9 , these segments then being advantageously fixed at the intersection between two angular sectors of neighboring distributors 6, so as to limit air leaks at this location. It is also possible to have a single sheet 7 which extends over 360°, closed on itself in a ring or split.

As shown on the figure 11 , it is possible to reduce the mass of the sheet 7, to provide scallops 710 on the lower part of its fixing side 71.

The sheet 7 provides both a sealing role by limiting the inter-sector leaks of the distributor 6 and a role of thermal protection with respect to the shroud 5, the abradable material 53 and the other elements of the low pressure turbine which are below this plate.

Furthermore, it is also possible to provide an additional thermal protection sheet 8, shown in the figure 10 .

The sheet 8 is arcuate as is the protective sheet 7. It also has a substantially L-shaped cross-section with a fixing flank (not visible in the figure) intended to be fixed by welding or brazing on the external face 52 of the ferrule 50 and a protective flank 81 which extends substantially parallel to the feet 621.

Just like the protective sheet 7, the sheet 8 can be divided into sectors or extend over 360° and may or may not have scallops 810. Its role is to protect the shroud 5 and to direct the flow of hot air towards the blades. 63.

The assembly of the various angular distributor sectors 6 on the ferrule 5 will now be described in more detail.

Each angular sector 6 is mounted on the shroud 5 so that its tab 622 is introduced laterally through the open end of the slot 553 then moved in the anti-clockwise direction, that is to say towards the left on the picture 3 .

The bottom 555 of the slot 553 acts as an anti-rotation stop.

The rear 541 and front 554 faces constitute bearing faces for the tongue 622 and limit its axial displacement and therefore the axial displacement of the corresponding angular sector 6.

As can be seen in the sectional views of the figures 7 and 8 , the tabs 622 are preferably inserted into the slots 553, so that the shoulders 623 or 624 do not come into contact respectively with the wing 54 or the branch 552, which makes it possible to leave a slight radial clearance j1, respectively j2, between the two, and allows the expansion of the various components.

There figure 6 represents an angular distributor sector 6 whose tab is inserted into the slot of the dog clutch carried by the ferrule 5.

Finally, in order to avoid any risk of displacement of an angular sector 6, once the tongue 622 has been inserted into the slot 553, it is necessary to block the sector 6 with respect to the ferrule 5.

Advantageously, the lug 556 makes it possible to prevent the disengagement of the tongue 622, the elasticity of the branch 552 being sufficient to allow the introduction of the tongue into the slot.

However, as shown in the figure 12 , it is also possible to add a spot weld 90 between the pin 556 and the face 541 and/or a pin, a screw or a rivet 91 between the branch 552 and the wing 54.

The various angular sectors 6 are all positioned on the outer casing of the turbine (see the casing 100 of the figure 1 ). Then, the ferrule 5 is brought closer to the tabs 622 so that each tab 622 is in front of the entrance to a slot 553 and then the ferrule 5 is rotated to the right of the picture 3 , to simultaneously engage all the tabs 622 in the slots 553.

The shroud 5 is mounted in the turbine so that its axis X1 -X'1 coincides with the axis X, X' of the turbine.

The invention has the following advantages:
The ferrule 5 is cylindrical in shape and with a simple claw fixing system. Its manufacture is therefore inexpensive, especially with new manufacturing processes, for example additive manufacturing.

The abradable material fixed 53 to the ferrule 5 is now separated from the sectors 6 of the distributor. The repairs of the ferrule 5 or of the distributor sectors 6 are therefore independent of each other, which can simplify maintenance operations.

The invention also allows an overall mass saving on the whole of the distributor 4, because the ferrule 5 has a thickness less than that of the base of an internal platform on a conventional angular sector.

The intersector clearances at the level of the internal platforms of sectors of neighboring distributors 6 are completely covered by the shroud 5. The leaks under the distributor's platform have thus been greatly reduced.

Thanks to the ferrule 5, all of the internal platforms 62 of the distributor sectors 6 are aligned axially, which makes it possible to better controlling axial play in the turbine, with a beneficial impact on engine performance.

The manufacturing cost, in particular the foundry cost for manufacturing the distributor, is also reduced, since there is less material and less areas to control. It is no longer necessary to braze and machine the abradable material on each distributor sector. In addition, it is no longer necessary to make slots on the internal platform 62, which leads to a reduction in costs and simplifies manufacture.

Finally, overall, the invention saves considerable time during assembly of the dispenser.

Claims (9)

1. A turbine nozzle (4) comprising several angular nozzle sectors (6), each angular sector (6) comprising two coaxial circular arc-shaped inner (62) and outer (61) platform sectors respectively, interconnected by several radial or substantially radial blades (63), each inner platform sector (62) being secured to a radially inner foot (621), this nozzle (4) comprising an annular shroud (5) on which said angular nozzle sectors (6) are fixed circumferentially end to end, this shroud (5) comprising a cylindrical ring (50) whose radially inner face (51) carries an abradable material (53), characterized in that the radially inner foot (621) of each inner platform sector (62) comprises a tab (622), which extends radially inwards from said foot (621), and which extends circumferentially over part of the length of said foot, in that the radially outer face (52) of said cylindrical ring (50) carries an outer radial wing (54), provided with a plurality of L-shaped legs (55), whose one of the branches (551) called "fixing" branches is secured to the outer radial wing (54) and extends perpendicularly to a radius of the ring (50) and parallel to the longitudinal axis X1-X'1 of said ring (50) and whose other branch (552) called "retaining" branch extends opposite this outer radial wing (54) and at a short distance therefrom, so as to arrange therewith a slot (553) for receiving said tab (622) of each angular nozzle sector (6) and in that this slot (553) is open at one of its longitudinal ends to allow the engagement of said tab (622), so as to ensure the fixing by dog clutching of said shroud (5) on each angular nozzle sector (6).
2. The nozzle (4) according to claim 1, characterized in that said tab (622) of the radially inner foot (621) extends circumferentially over one third of the length of said foot (621).
3. The nozzle (4) according to claim 1 or 2, characterized in that said tab (622) extends circumferentially at the center of the radially inner foot (621) of each inner platform sector (62).
4. The nozzle (4) according to any of the preceding claims, characterized in that the end of the retaining branch (552) is provided with a protruding lug (556) in the direction of the outer radial wing (54), so as to circumferentially retain said tab (622) when the latter is engaged in the slot (553) for receiving the tab.
5. The nozzle (4) according to any of the preceding claims, characterized in that the retaining branch (552) and the outer radial wing (54) are joined by a pin, a rivet (91) and/or a weld (90).
6. The nozzle (4) according to any one of the preceding claims, characterized in that it comprises at least one sealing metal sheet (7), in at least one L-shaped or substantially L-shaped cross-sectional segment, fixed on the radially inner foot (621) of an angular nozzle sector (6), so as to extend at least opposite the intersection between two neighboring angular nozzle sectors.
7. The nozzle (4) according to any one of the preceding claims, characterized in that it comprises at least one thermal shielding metal sheet (8), in at least one L-shaped or substantially L-shaped cross-sectional segment, fixed on the cylindrical ring (50) of the shroud (5).
8. A turbomachine turbine, characterized in that it comprises at least one nozzle (4) according to any one of the preceding claims.
9. The turbomachine, such as an aircraft turbojet engine or turboprop, characterized in that it comprises a turbine according to claim 8.

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