EP3553322B1 - Assembly for an axial turbine engine with two-part external ferrule - Google Patents

Description

Technical area

The invention relates to the field of axial turbomachines and more particularly aircraft turbojets. More specifically, the invention relates to the construction of an outer shroud of a compressor fitted with variable-pitch stator vanes. The invention also relates to a compressor fitted with such a shroud, to the method of assembling such a compressor and to a blade for such a compressor.

Prior technique

The document FR 2 565 297 A1 describes a gas turbine compressor stator. The stator vanes can be oriented around their axis by means of a connecting rod which is screwed to each vane tip. Housings are provided on the shroud to receive the blade heads with a sleeve and a flange closes the housings to enclose the blade heads in their housings. The sleeve and the heads of the blades are hollowed out to cooperate with a bolt in order to hold the blade radially in its housing.

This design is complex, because it involves a large number of parts and the assembly of such a stator is therefore tedious.

The documents EP 2 006 495 A1 , US 2016/341068 A1 , US 3,314,654A And US 3,558,237A describe various examples of designs for housings receiving blades. These examples have in common to present areas of mechanical stress concentrations and therefore structural weaknesses.

Summary of the invention Technical problem

The object of the invention is to solve at least one of the problems posed by the prior art. Another object of the invention is to propose a simpler and more compact design, allowing easier mounting of variable orientation vanes. The invention also aims to provide a lightweight solution, economical, reliable, easy to produce, easy to maintain, and easy to inspect.

Technical solution

The subject of the invention is an assembly according to claim 1 and an assembly method according to claim 12.

Thus, the half-orifices and the flanges of the sections are arranged to allow the assembly of the sections to each other via the flanges, the half-orifices of the sections being placed opposite each other to form cylindrical orifices when the two sections are assembled.

• chaque espacement circonférentiel entre deux demi-orifices adjacents contient une bride ;
• les brides s'étendent circonférentiellement d'un demi-orifice au demi-orifice adjacent ;
• les brides comprennent chacune deux trous prévus pour recevoir un goujon d'assemblage des tronçons, les trous étant à une position circonférentielle inférieure au quart de la longueur circonférentielle d'une bride, à proximité de chacun des demi-orifices ;
• les bossages ont une surface extérieure semi-conique et une surface intérieure semi-cylindrique formant le demi-orifice ;
• le tronçon amont présente une bride à son extrémité axiale opposée aux demi-orifices, pour assembler ledit tronçon à un carter de support de soufflante ou à un bec de dégivrage. Alternativement ou en combinaison, le tronçon aval peut être équipé d'une bride de fixation du côté axial opposé aux demi-orifices ;
• un des tronçons, notamment le tronçon dit aval, comporte un siège pour une bague de synchronisation de l'orientation des aubes, le siège comprenant une surface cylindrique externe. La bague de synchronisation est aussi appelée anneau de manoeuvre, bague d'actionnement ou bague de commande ;
• le tronçon qui comprend le siège de la bague ou de patins comprend uniquement, du côté axial du siège opposé aux demi-orifices, des portions de diamètre inférieur à la surface cylindrique du siège, de sorte que la bague éventuellement avec ses patins puisse être montée par translation axiale sur son siège ;
• un troisième tronçon, relié au tronçon amont ou aval, formant avec celui-ci une autre rangée annulaire d'orifices pour accueillir une autre rangée annulaire d'aubes statoriques ;
• la bielle est monobloc avec l'aube, venue de matière, soudée ou collée à la tête de l'aube. Par « venus de matière », on entend, fabriqué d'un seul tenant, monobloc ;
• la bague comprend des patins en contact radial avec le siège ;
• les brides chevauchent radialement le la bague de synchronisation et sont à distance axialement de celle-ci.

According to advantageous embodiments of the invention, the assembly may comprise one or more of the following characteristics, taken individually or in any combination as defined by the claims:

• each circumferential spacing between two adjacent half-orifices contains a flange;
• the flanges extend circumferentially from one half-hole to the adjacent half-hole;
• the flanges each comprise two holes provided to receive a stud for assembling the sections, the holes being at a circumferential position less than a quarter of the circumferential length of a flange, close to each of the half-orifices;
• the bosses have a semi-conical outer surface and a semi-cylindrical inner surface forming the half-orifice;
• the upstream section has a flange at its axial end opposite the half-orifices, to assemble said section to a fan support casing or to a de-icing nozzle. Alternatively or in combination, the downstream section can be fitted with a fixing flange on the axial side opposite the half-orifices;
• one of the sections, in particular the so-called downstream section, comprises a seat for a ring for synchronizing the orientation of the blades, the seat comprising an outer cylindrical surface. The synchronization ring is also called an operating ring, actuation ring or control ring;
• the section which includes the seat of the ring or pads comprises only, on the axial side of the seat opposite the half-orifices, portions of diameter smaller than the cylindrical surface of the seat, so that the ring possibly with its pads can be mounted by axial translation on its seat;
• a third section, connected to the upstream or downstream section, forming with the latter another annular row of orifices to accommodate another annular row of stator vanes;
• the connecting rod is in one piece with the blade, made from material, welded or glued to the head of the blade. By “made from material”, we mean, made in one piece, in one piece;
• the ring comprises pads in radial contact with the seat;
• the flanges radially overlap the synchronization ring and are axially spaced therefrom.

The invention also relates to a method for assembling an assembly as described above, the method comprising the following steps: the assembly of an operating rod at the head of each blade, or the one-piece manufacture of a connecting rod with dawn; the introduction of the journals of the blades into the half-orifices of one of the sections, preferably the downstream section; the positioning of the other of the sections, thus enclosing the journals in the orifices thus formed; fixing, preferably by screwing, the flanges of the two sections together.

According to an advantageous embodiment of the invention, the method comprises a step of fixing the synchronization ring of the connecting rods, preferably on the downstream section, and preferably before the assembly of the blades.

According to an advantageous embodiment of the invention, the method comprises a step of connecting the connecting rods to the synchronization ring takes place before the sections are positioned facing one another.

Alternatively, the ring can be fixed to the connecting rods after the assembly of the two sections.

Benefits provided

The invention proposes a specific geometry which makes it possible to assemble the vanes with variable orientation without requiring the mounting of each of the connecting rods once the vane has been fitted. When the compressor comprises about fifty blades per stage, the design proposed in the present invention generates substantial savings in assembly time. Moreover, despite the presence of upstream and/or downstream flanges, this design allows the mounting of a more compact one-piece synchronization ring (a 360° ring).

Brief description of the drawings

• There figure 1 represents an axial turbomachine according to the invention;
• There figure 2 is a diagram of a turbomachine compressor with an assembly according to the invention;
• THE figures 3 and 4 respectively show the head of a blade and a bottom view of the operating rod;
• There figure 5 illustrates a partial top view of the arrangement of the two sections;
• THE figures 6 and 7 are cross-sectional views of the arrangement of the blade head with a welded connecting rod;
• There figure 8 is a cross-section of a vane with a one-piece connecting rod;
• There figure 9 is a partial isometric view of the arrangement of the two sections;
• There figure 10 shows a partial sectional view of the compressor.

Description of embodiments

In the following description, the terms “internal” and “external” refer to positioning relative to the axis of rotation of an axial turbomachine.

The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the main flow direction of the stream in the turbomachine.

There figure 1 schematically represents an axial turbomachine. In this specific case, it is a turbofan engine. The turbojet engine 2 comprises a first compression level, called low-pressure compressor 4, a second compression level, called high-pressure compressor 6, a combustion chamber 8 and one or more levels of turbines 10. In operation, the mechanical power of the turbine 10 transmitted via the central shaft to the rotor 12 sets in motion the two compressors 4 and 6. The latter comprise several rows of rotor blades associated with rows of stator blades. The rotation of the rotor around its axis of rotation 14 thus makes it possible to generate an air flow and to gradually compress the latter until it enters the combustion chamber 8.

An inlet fan commonly referred to as a fan or blower 16 is coupled to the rotor 12 via a gear train 13, and generates an air flow which is divided into a primary flow 18 crossing the various aforementioned levels of the turbomachine, and into a secondary flow 20 passing through an annular duct (partially shown) along the machine to then join the primary flow at the turbine outlet.

The secondary flow can be accelerated so as to generate a thrust reaction necessary for the flight of an aircraft. The primary 18 and secondary 20 streams are coaxial annular streams fitted into one another.

There picture 2 is a sectional view of a compressor of an axial turbomachine such as that of the figure 1 . The flow can be transonic there. The compressor may be a low-pressure compressor 4. The rotor 12 comprises several rows of rotor blades 24, in this case three. It can be a bladed one-piece drum, or include blades fixed by dovetail.

The low-pressure compressor 4 comprises several rectifiers, in this case four, which each contain a row of stator vanes 26. Certain stator vanes are of adjustable orientation, also called variable-pitch vanes. The rectifiers are associated with the fan 16 or with a row of rotor blades to straighten the air flow, so as to convert the speed of the flow into pressure, in particular into static pressure.

A de-icing nozzle 22 may be mounted on a housing which supports a row of inlet stator vanes 28.

Stator vanes 26 extend substantially radially from outer shroud 30 to inner rings 32. Vanes 26 can be attached to outer shroud 30 using pins. The shroud 30 defines an internal surface 29 which guides the flow of gas. According to the invention, the shroud 30 is composed of several axial sections.

The blades 26 comprise a cylindrical trunnion 34 which is received in a radial orifice of the outer shroud 30. A connecting rod 36 integral with the trunnion and pivoting around the axis of the trunnion 34 makes it possible to maneuver the pivoting of the blade. Actuating means 40 of the connecting rod 36 are shown schematically and will be described later.

THE figures 3 and 4 illustrate a known example of a connection between the tip of a blade 26 and the outer shroud 30. The blade 26 comprises a blade 42 having a leading edge 44 and a trailing edge 46. The tip of the blade 26 can include a shoulder 48 for centering and positioning the vane 26 in the shroud 30 as well as a groove to receive a seal. In the known embodiments, the connecting rod 36 for operating the pivoting of the blade is fixed by a nut 50 on a threaded portion 52 of the head of the blade. A centering chamfer 54 may be provided at the end of pin 34.

The head of the blade is received in line with an extra thickness of the shroud 30, which can be in the form of a boss 33.

Connecting rod 36 comprises a conical orifice 60 corresponding to chamfer 54, a body 62 and a lug 64. As shown in figure 4 which is a bottom view of the connecting rod 36, the orifice 60 may comprise a groove 66 to receive a key and thus make the blade 26 and the connecting rod 36 integral in rotation. The connecting rod 36 also comprises a hole 68 to be connected to an actuating member (described in figure 10 ). In this example, the outer shroud 30 has an orifice receiving the journal 34. The journal 34 is inserted into the orifice from below (in the direction of the picture 3 ), then connecting rod 36 is screwed to thread 52.

THE figures 5 to 7 show a first embodiment of the connection between the blade 26 and the outer shroud 30 according to the invention

There figure 5 shows a partial top view of the assembly according to the invention. There figure 5 references the directions VI and VII whose cross-sectional views are illustrated in figures 6 and 7 respectively.

Two sections 130 and 230 form the shell. Each of the sections comprises a tubular wall 131, 231 defining an internal guide surface 129, 229 and an annular series of half-orifices 132, 232, formed in half-bosses 133, 233. The two half-orifices 132, 232 form the orifice 31 which receives the head of the blade. The two sections 130, 230 are assembled via screwed elements which hold two adjacent flanges 134, 234 together. The flanges 134, 234 extend from one boss to the neighboring boss circumferentially. There figure 5 represents only one orifice.

There figure 6 is a cut in the VI:VI plane defined on the figure 5 .

The shroud comprises two adjacent axial sections 130, 230. Each of the two sections comprises a tubular wall 131, 231 and an annular row of half-orifices 132, 232 formed in the bosses 133, 233.

The connecting rod 36 of this first embodiment is welded to the head of the blade. This is done before the assembly of the blade in the shell. As the orifice 31 results from the combination of the two sections 130, 230, the journal 34 can be positioned in a half-orifice 132, 232 of one of the sections despite the dimension of the connecting rod which is greater than the diameter of the orifice. 31, then the other section is fixed to enclose pin 34 in hole 31.

The connecting rod 36 may have a shape similar to that of the figure 4 , potentially without keyway, become unnecessary due to welding.

There figure 7 shows a view according to the VII:VII plane defined on the figure 5 . This view shows the assembly of the two flanges 134, 234 by means of a bolt 35. Indeed, the flanges 134, 234 have through holes 135, 235 allowing the assembly of the ferrule sections by screwed elements 35. Back -map on the figure 7 we distinguish the bosses 133, 233.

There figure 8 shows another embodiment. As opposed to figures 6 and 7 , the connecting rod 36 is here not welded to the pin 34 but the entire blade (blade, pin, connecting rod) is one piece, made in one piece. For example, the connecting rod can be forged or cast with the rest of the blade. The functional surfaces (trunnion, extrados/intrados) are then machined. In the same way as for the example of figures 6 and 7 , it is the two-part design of the orifice of the ferrule which makes it possible to provide such a one-piece blade with its connecting rod.

There figure 9 represents a partial isometric view of the ferrule 30. It shows in particular some of the bosses 133, 233 as well as the flanges 134, 234 and their assembly holes (only the holes 235 of the downstream section 230 are visible). The flanges completely connect each of the bosses 133, 233 to the neighboring boss. The upstream section 130 comprises a flange 136 which makes it possible to connect the shroud to the nozzle of the compressor. The downstream section 230 comprises a cylindrical bearing surface 237 to guide the pads of the synchronization ring 72 (see figure 10 ).

In this example, the flanges 134, 234 rise above the tubular wall 131, 231 by a height equivalent to that of the bosses 133, 233. Alternatively, their respective elevations may differ.

The sections may have axial centering pins, in particular at the level of the flanges. For example, axial pins provided in one or more of the flanges 134 can penetrate into corresponding axial orifices in one or more of the flanges 234.

There figure 10 represents a section of the compressor. The shroud made up of the two sections 130, 230 is fixed to the support casing of the de-icing nozzle which carries the inlet stator vanes 28 via the upstream flange 136. A downstream flange 236 can be provided on the downstream section.

The mechanism 40 for actuating the pivoting of the blade comprises a pin 70 which is received in a distal orifice of the connecting rod 36 (equivalent to the orifice 68 of the connecting rod of the figure 4 ). The pin 70 passes through a synchronization ring 72 and ends in a pad 74. The pad 74 rests on a cylindrical surface 237 of the downstream section. The cylindrical surface 237 ends upstream with a projection which limits the movement of the pad 74 axially. The projection and the cylindrical surface 237 form a seat for the shoe 74. The synchronization ring 72 cooperates with as many pins 70 as connecting rods 36 distributed annularly. The ring 72 can be actuated in pivoting around the axis 14 by appropriate means such as for example a toothed wheel cooperating with a rack provided on the ring 72. The pivoting of the ring 72 causes a corresponding displacement of the pins 70 along the surface 237 and these thus make the connecting rod 36 and the blade 26 pivot around the axis 38.

The general shape of the downstream section allows the assembly of the synchronization ring and the pins. In the example shown in figure 10 , the flange 236 has an outer diameter which is substantially smaller than the inner diameter of the ring 72, thereby allowing the pegs with their pads to be inserted into the ring before the ring and peg assembly is slid axially upstream to be mounted on the downstream section.

According to the invention, the trunnions 34 of the blades are inserted into the half-orifices 232, then the upstream section is brought to enclose the trunnions 34 in the orifices 31 thus formed. The flanges 134, 234 are then screwed together. Then the actuating pins 70 carried by the synchronization ring 72 can be assembled to the connecting rods 36. Alternatively the fixing of the pins 70 to the connecting rods 36 can take place before the upstream section 130 is positioned in contact with the downstream section 230. Also , the ring 72 can be inserted around the downstream section 230 before the blades 26 are brought into the half-orifices 232.

The embodiment described here has two sections 130 and 230 but one or more additional sections can be provided and assembled in the same way, each of the sections having an annular row of half-orifices facing the half-orifices of the adjacent section to forming orifices receiving blade tips which may or may not have variable orientation.

Claims (12)

1. An assembly for an axial turbomachine (2), in particular for an aircraft turbojet engine, comprising:

   - an annular row of stator vanes (26) each with an airfoil (42) and a radial head (34, 48, 54) containing a cylindrical journal (34), the vanes (26) being orientable by pivoting about the axis of the journal (38);

   - an actuator (40) for pivoting the vanes (26) comprising a synchronizing ring (72) and operating rods (36) connecting the synchronizing ring (72) to each of the vanes;

   - an outer shroud (30) comprising a tubular wall (131, 231) and having an annular row of radial orifices (31) for receiving the heads (34, 48, 54) of the vanes (26),

   the outer shroud (30) comprising an axial outer shroud section (130), referred to as the upstream section, and an axial outer shroud section (230), referred to as the downstream section;

   each of the sections (130, 230) comprising an internal guide surface (129, 229) for the flow of gas from the turbomachine, the two sections (130, 230) being axially adjacent,

   each of the sections (130, 230) comprising:

   - an annular row of preferably semi-cylindrical radial half-orifices (132, 232); and

   - at least one flange (134, 234) positioned between two circumferentially adjacent half-orifices (132, 232);

   the half-orifices (132, 232) being arranged to allow each of the half-orifices (132, 232) of one section (130, 230) to be brought into axial and circumferential registration with a half-orifice (132, 232) of the other section (230, 130) to form the annular row of orifices (31),

   the at least one flange (134, 234) of one section (130, 230) being arranged to be axially and circumferentially matched with the at least one flange (134, 234) of the other section (230, 130);

   the sections (130, 230) being provided with an annular row of radial thickenings or bosses (133, 233) accommodating the half-orifices (132, 232),

   the radial thickeners or bosses (133, 233) being connected two by two circumferentially by the flanges (134, 234),

   one of the sections (130, 230), in particular the downstream section (230), having a seat for the vane orientation actuator (40), the seat comprising an outer cylindrical surface (237),

   characterized in that

   the head (34, 48, 54) of each of the vanes (26) has an outer radial portion (36, 62, 64) on the side of the journal (34) opposite the vane (42), the outer radial portion (36, 62, 64) extending circumferentially and/or axially by a dimension which is greater than the diameter of the corresponding orifice (31), and

   the section (130, 230) which comprises the seat has, on the axial side of the seat opposite the half-orifices (132, 232), only portions of smaller diameter than the diameter of the cylindrical surface (237) of the seat.
2. An assembly according to any of the preceding claims, characterised in that each circumferential spacing between two adjacent half-orifices (132, 232) contains one of the flanges (134, 234).
3. An assembly according to any of the preceding claims, characterised in that the flanges (134, 234) extend circumferentially completely from one half-orifice (132, 232) to the adjacent half-orifice (132, 232).
4. An assembly according to any of the preceding claims, characterised in that the flanges (134, 234) each comprise two holes (135, 235) adapted to receive a fastening pin (35) for joining the sections (130, 230), the holes (135, 235) being at a circumferential position less than a quarter of the circumferential length of a flange (134, 234), proximate to each of the half-ports (132, 232).
5. An assembly according to the preceding claim, characterised in that the bosses (133, 233) have a semi-conical outer surface and a semi-cylindrical inner surface forming the half-orifice (132, 232).
6. An assembly according to any of the preceding claims, characterised in that the upstream section (130) has a flange (136) at its axial end opposite the half-orifices (132), for connecting said section (130) to a fan support casing or to a de-icing nozzle (22).
7. An assembly according to any of the preceding claims, comprising a third section, connected to the upstream or downstream section (130, 230), forming therewith a further annular row of orifices for accommodating a further annular row of stator blades.
8. An assembly according to any of the preceding claims, characterised in that the ring (72) carries pads (74) in radial contact with a cylindrical surface (237) of one of the sections (130, 230).
9. An assembly according to any of the preceding claims, characterised in that the flanges (134, 234) radially overlap the ring (72) and are axially spaced therefrom.
10. A method of assembling an assembly according to any of claims 1 to 9, the method comprising the following steps:

    - assembling a connecting rod (36) to the head (34, 48, 54) of each vane (26), or integrally manufacturing a connecting rod (36) with the vane (26);

    - inserting the journals (34) of the blades (26) into the half-orifices (232) of one of the sections, preferably the downstream section (230);

    - placing the other of the sections (130), thus enclosing the journals (34) in the orifices (31) thus formed;

    - fixing, preferably by screwing (35, 135, 235), the flanges (134, 234) of the two sections (130, 230) together.
11. Method according to claim 10, characterised in that it comprises a step of fixing the ring (72) for synchronising the connecting rods (36), preferably on the downstream section (230), and preferably before the blades (26) are fitted.
12. Method according to one of claims 10 or 11, characterised by a step of connecting the connecting rods (36) to the synchronisation ring (72) before the sections (130, 230) are positioned opposite each other.

Images