Attachment of a nozzle to a casing of a turbomachine

The invention relates to an assembly comprising a turbomachine casing (7) and a nozzle made of ceramic matrix composite material having a blade (21), the frontside and backside surfaces of which delimit an internal cavity, and which is connected at its radially external end by a connecting part (31) of the nozzle to the casing (7), said connecting part (31) extending substantially radially outwards, the blade (21) and said connecting part (31) being formed in one piece, said assembly being characterized in that the connecting part (31) is fastened to a first radial wall (51) integral with the casing (7) by fastening means (53).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to French Patent Application No. 1857149, filed Jul. 31, 2018, which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the connection between a ceramic matrix composite material (CMC) nozzle and a metal turbomachine casing.

TECHNICAL BACKGROUND

Turbine3nozzles1radially extend between stator walls5and an external turbomachine casing7. The nozzles1are used to channel and orient the gas flow through the primary jet9of the turbomachine. A turbine3is composed of several stages. Each stage includes a stationary nozzle1and a movable impeller11.

In the current turbines3, the nozzle1is commonly made of a metallic material and consists of guide vanes13delimited by radially internal15and radially external17platforms. The radially internal and radially external platforms15,17radially define between them the primary jet9through which the gas flow passes. The areas radially inside the radially internal platform15and radially outside the radially external platform17are considered off-jet.

Generally, the radially external platforms17include at their upstream and downstream ends flanges19extending radially outwards and then longitudinally protruding from the blade21of the nozzle1. The flanges19are intended to fasten the nozzle1to the outer casing7, so that the parts extending substantially axially with respect to the flanges are supported on casing7rails23.

In addition, in the current configurations, the metal nozzles1are subjected to forces related to the aerodynamic flow of air in the jet9. The nozzle1is also subjected to a piston effect due to pressure differences between each stage of the turbomachine. The pressure decreases as the air passes through the turbine3. Thus, the upstream end25and the downstream end27of the radially internal off-jet part which the nozzle1is fastened to are subjected to different pressures. This pressure difference in the radially internal off-jet part generates a force in the downstream direction, represented by an arrow F. The forces related to the aerodynamic flow and the piston effect, described above, create a moment at the attachment between the nozzle1and the casing7. This moment can damage the nozzle1.

A nozzle1made of CMC material is preferable to a metallic nozzle1since the CMC nozzles1increase the performance of the turbines3by reducing the amount of cooling gas required. However, manufacturing a CMC nozzle1with the same shape as a metal nozzle1is complex and it is not optimal to want to attach it to the casing7in the same way as a metal nozzle1. As a matter of fact, the differential expansion between parts made of metallic material and CMC prevents particular arrangements of metallic parts and others made of CMC. In addition, the CMC material is abrasive, so the flanges of the CMC nozzle1would damage the metal rails23of the casing7.

The invention aims in particular to provide a simple and effective solution to the problems associated with mounting a CMC nozzle1in a turbine3, and more particularly its attachment to a metal casing7.

SUMMARY OF THE INVENTION

For this purpose, it proposes an assembly comprising a turbomachine casing and a nozzle made of ceramic matrix composite material having a blade, the frontside and backside surfaces of which delimit an internal cavity, and which is connected at its radially external end by a connecting part of the nozzle to the casing, said connecting part extending substantially radially outwards, the blade and said connecting part being formed in one piece, said assembly being characterized in that the connecting part is fastened to a first radial wall fastened to the casing by fastening means.

Such a nozzle consists of a blade and a connecting part produced in one piece, which allows the forces induced by the aerodynamic flows and the most direct piston effect possible to flow.

The blade and the connecting part are produced by sagging two-dimensional fibrous fabrics bonded at the leading and trailing edges of the blade. The fibrous fabrics are fibrous reinforcements.

In another embodiment, the blade and the connecting part are obtained by three-dimensional weaving. The fact that the blade and the connecting part are in one piece guarantees the continuity of the reinforcing fibres between the blade and the connecting part.

In addition, the fastening of the connecting part on a radial wall integral with the casing makes it possible to take up the forces over the entire connecting part, which is not the case for a connecting part resting on a casing rail.

Advantageously, the radially external end of said connecting part comprises at least one radial flange, strictly extending radially and being applied in the circumferential direction on said first radial wall.

The fact that the radial flange is arranged at the radially external end of the connecting part allows the latter to be applied and fastened, without clearance, to the radial wall integral with the casing. The absence of clearance between the radial flange and the radial wall integral with the casing makes it possible to avoid the presence of a moment between these two radial walls, and consequently to prevent an accelerated degradation of the fastening between the radial flange and the radial wall integral with the casing.

According to a characteristic of the invention, the assembly comprises an intermediate part for fastening the nozzle to the casing, the intermediate part comprising a circumferential wall and said at least one first radial wall which extends radially inward from said circumferential wall and is fastened to said at least one radial flange of the connecting part.

In a preferred embodiment, the nozzle is not directly fastened to the casing but to an intermediate part which comprises a circumferential wall from which a wall extends radially inward. The radial flange of the connection part of the nozzle is fastened to the radial wall of the intermediate part. The circumferential wall of the intermediate part can thus be configured in such a way that a CMC nozzle can be fastened to the casing. Since the intermediate part is preferably made of metal, the fastening areas of the intermediate part can be similar by fastening a metal nozzle to a metal casing.

In a particular embodiment, the nozzle comprises a platform having a circumferential wall externally delimiting an air flow path and a second radial wall extending radially outwards from said circumferential wall, said second radial wall being fastened by said fastening means to the first radial wall and said connecting part.

In a second preferred embodiment, compatible with the embodiment described above, the nozzle includes a platform at the radially external end of the blade. This platform includes a circumferential wall from which a radial wall extends radially outwards. The radial wall of the platform extends substantially parallel to the connecting part of the nozzle. Said radial wall of the platform is fastened to the connecting part and to the radial wall integral with the casing, so as to stiffen the fastening thereof.

Advantageously, fastening means pass through said at least one fastening flange of the connecting part, said first radial wall of the intermediate part and said second radial wall of the platform.

In order to stiffen the fastening between the connecting part and the radial wall integral with the casing, it is preferable that the fastening means also pass through the radial wall of the platform in order to press the various radial walls against each other and avoid the creation of a moment around the fastening means. A moment is defined by a rotating movement of at least one of the walls relative to a stationary element, in this case the fastening means.

Preferably, said at least one radial flange is bolted to said first wall.

The bolted fastening of the radial flange on the radial wall of the casing thus prevents any movement of the nozzle with respect to the casing or an intermediate part fastened to the casing. Therefore, such a fastening avoids friction of the CMC nozzle, the material of which is abrasive on the metal surface of the casing or the intermediate part.

Advantageously, the connecting part comprises at least one opening in fluid communication with the internal cavity of the blade.

The connecting part comprises at least one opening to allow fluid communication of air between the off-jet part radially outside the nozzle and the off-jet part radially inside the nozzle through the opening and the internal cavity of the blade.

Advantageously, the ceramic matrix composite material of the blade and the connecting part includes continuous reinforcing fibers preferentially extending in the radial direction.

The radial direction of the reinforcing fibres in the CMC material of the blade and the connecting part allows these parts to have a better resistance to aerodynamic forces caused by the flow of air longitudinally moving in the turbomachine.

According to another particular embodiment, the connecting part consists of two radial flanges, with the radial flanges extending parallel and spaced from each other.

These first and second disjoint walls allow less impact on the air flow in the radially external off-jet part since the surfaces intended to be impacted by the air flow are thinner.

The invention will be better understood and other details, characteristics and advantages of the invention will appear when reading the following description, which is given as a non-limiting example, with reference to the attached drawings.

DETAILED DESCRIPTION

In the detailed description below, the first, respectively the second wall of the connecting part extends radially outwards from the backside, respectively the frontside surface of the blade.

FIG. 1relates to a turbine3of the prior art described above.

The CMC nozzle1, according to one of the embodiments of the invention, comprises a blade21having an internal cavity29(FIG. 4A) extending radially. The nozzle1comprises, at the radially internal and external ends, respectively radially internal and radially external platforms15,17. The radially internal platform15is fastened by means of fastening means to a radially internal stator wall5of the turbomachine. The nozzle1also includes a connecting part31for fastening the nozzle1to the casing7. The connecting part31consists of a part in one piece with the blade21and extends radially outwards from the radially external end of said blade21. The blade21and the connecting part31consist of at least two impregnated fibrous fabrics or at least two stacks of impregnated fibrous fabrics connected at the leading edge33and the trailing edge35forming the internal cavity29of the blade21. The impregnated fabrics of the connecting part31form a first wall37and a second wall39connected in the extension of the blade at the leading edge33and the trailing edge35.

In another embodiment, the blade21and the connecting part31can be formed using a single fibrous fabric constituting a preform. Such an embodiment is advantageous in that the reinforcement formed by the blade21and the connecting part31is continuous and has a good mechanical reaction to the stresses. This preform can be obtained by three-dimensional weaving.

In the case where the blade21and the connecting part31are obtained using a single fibrous fabric, the leading edge33and the trailing edge35are naturally connected by strands that ensure cohesion in the thickness of the preform.

The first and second walls37,39extend radially outwards on either side of the internal cavity29formed in the blade21. The blade21, the connecting part31and the radially internal and external platforms15,17are made of CMC material respectively. The CMC material consists of a fibrous texture and a matrix.

The matrix is preferably made according to the chemical vapor silicon carbide infiltration process according to the CVI (Chemical Vapor infiltration) process and/or by melting according to the MI (Melt Infiltration) process. The matrix can also be produced using the PIP (Polymer Impregnation and Pyrolysis) process, or using the SIC process.

Preferably, the reinforcing fibres used are HiNiS silicon carbide fibres.

Optionally, at least one of the platforms15,17is formed integrally with the blade21and the connecting part31by three-dimensional fibrous weaving between the reinforcing fibres of the blade21and the connecting part31and the fibres of the platform.

Alternatively, said platform15,17can be obtained in one piece with the blade21and the connecting part31by gluing using the ceramic materials matrix of the platform15,17, the blade21and the connecting part31. The matrix here acts as a binder when the silicon rises from the matrix of the CMC material.

FIGS. 2A and 2Bare now referred to, which represent a CMC nozzle1according to a first embodiment.

The radially internal platform15is radially supported and fastened to a stator wall5of the turbine3.

The upstream edge41of the connecting part31formed by the connection of the first and second walls37,39extends radially outwards in the extension of the leading edge33of the blade21and matches its profile. The radially external edge43of the connecting part31extends substantially longitudinally to conform to the shape of the casing wall7.

The downstream edge45of the connecting part31formed by the connection of the first and second walls37,39extends radially outwards in the extension of the trailing edge35so as to be substantially parallel to the upstream edge41. The connecting part31has a fillet between the upstream edge41and the radially external edge43of the connecting part. The same applies between the downstream edge45and the radially external edge43of the connecting part31.

The fibrous fabrics of the first and second walls37,39arranged on either side of the internal cavity29of the blade21are circumferentially abutting against each other, so that the two fabrics extend parallel and strictly radially at the contact zone47. The fabrics of the first and second walls37,39are connected to each other at the contact zone47, so as to form a radial fastening flange49.

Said connection can be reinforced with reinforcing fibres extending in a direction transverse to said direction of extension of the radial fastening flange49.

In another embodiment, said connection can be obtained by gluing. As described above, the matrix of the first and second walls37,39can act as a binder between two ceramic parts of the same construction.

The radial fastening flange49is fastened to a radial wall51fastened to the casing7by means of fastening means53. The attachment is provided by bolts. Thus, said radial flange49includes two ports55,55a,55bthrough which fastening means53pass. The first port55ais larger than the second port55b.

When the nozzle1is fastened to the casing7, the fastening means53extend substantially transversely through the radial connecting flange49and the radial wall51integral with the casing7.

The connecting part31also has an opening57transversely leading to the radial extension direction of the connecting part31. This opening57is radially delimited so as to be flush with the radially internal end of the radial flange49and the radially external end of the radially external platform17. This opening57is in fluid communication with the internal cavity29of the blade21and allows the radially internal and external off-jet parts with respect to the nozzle1to be in fluid communication.

FIGS. 3A and 3B, which represent a nozzle1according to a second embodiment, are now referred to.

The radially internal platform15is bolted59at an upstream flange61aand a downstream flange61bon an upstream flange and a downstream flange of a stator wall5.

The radially external platform17includes a flange63extending radially outward at the upstream end. The radially external platform17also includes first and second walls65,67extending radially outward from the circumferential wall of the radially external platform17. These walls65,67are arranged on either side of the connecting part31. The first wall65, respectively the second wall67, extending radially outwards from the radially external circumferential wall69of the radially external platform17follows the shape of the first wall37of the connecting part31, respectively the second wall39of the connecting part31.

The first and second walls37,39of the connecting part31extend radially outwards in a substantially planar manner at the upstream37a,39aand downstream ends (not visible). The first and second walls37,39of the connecting part31extend radially along a radial component and a circumferential component towards the backside surface of the blade over a first height H1and then strictly in a radial direction over a second height H2. The first and second walls37,39of the connecting part31also extend in a direction having a circumferential component and a longitudinal component substantially similar or parallel to the direction connecting the leading edge33to the trailing edge35of the blade21, in a radial cross-sectional plane.

The substantially flat upstream37a,39aand downstream ends of the first wall37and the second wall39of the connecting part31are pressed against each other. The upstream end37a,39arespectively the downstream end of the first wall37and the second wall39are fastened against each other by reinforcement in the third direction or gluing, as described above, thus forming a radial flange49, also called a radial fastening flange. Between their upstream37a,39aand downstream ends, the first wall37and the second wall39respectively comprise an intermediate part37c,39cextending in a direction transverse to the direction of longitudinal and circumferential extension of the connecting part31. The intermediate part37c,39cof the first wall37, respectively the second wall39, extends in the transverse direction opposite the second wall39, respectively the first wall37, so that the first wall37and the second wall39are spaced from each other at their respective intermediate parts37c,39c.

The intermediate parts37c,39cof the first wall37and the second wall39are arranged opposite each other and include a complementary shape defining a radially extending channel71between them. Said channel71radially extends between the internal cavity29of the blade21and the radially external off-jet part. This channel71thus allows a fluid communication between the radially external and radially internal off-jet part of the turbine3.

Optionally, the intermediate parts37c,39c, of the first and second walls37,39of the connecting part31, respectively define a circular half tube. Thus, when the first wall37and the second wall39of the connecting part31are applied and connected to each other, the intermediate parts37c,39cof the first wall37and the second wall39together define a cylindrical tubular channel71.

The first radial wall65and the second radial wall67of the radially external platform17extend radially outwards on either side of the connecting part31. Said first and second65,67radial walls of the radially external platform17respectively comprise an upstream end65a,67a, a downstream end65b(the downstream end of the second wall67being invisible) and an intermediate part65c,67c.

The upstream end65a,67a, the intermediate part65c,67cand the downstream end65bof the first radial wall65, respectively second radial wall67, of the radially external platform17conform to the shapes of the upstream end37a,39a, the intermediate part37c,39cand the downstream end of the first wall37, respectively second wall39, of the connecting part31on said first height H1. The downstream edge73a,75aof the upstream end65a,67a, respectively the upstream edge73b,75bof the downstream end65bof the first radial wall65band the second radial wall67of the radially external platform17extending radially outwards are flush with the upstream end71a, respectively the downstream end71bof the channel71.

On said second height H2, the upstream65a,67aand downstream65bends of said first and second walls65,67of the radially external platform17extend radially outwards along a strictly radial component protruding from their respective intermediate parts65c,67c. The upstream edge77a,79aand the radially external end65d,67dof the upstream end65a,67aof the first and second radial walls65,67of the radially external platform are flush with the upstream edge41and the radially external end43aof the upstream end37a,39aof the first and second walls37,39of the connecting part31. Respectively, the downstream edge77band the radially external end65e,67eof the downstream end of the first and second radial walls65,67of the radially external platform17are flush with the downstream edge and the radially external end43bof the downstream end of the first and second walls37,39of the connecting part31.

The connecting part31of the nozzle1according to the second embodiment is fastened to the casing7by means of an intermediate part81.

The intermediate part81comprises a circumferential wall83from which a wall85extends radially inward. The circumferential wall83of the intermediate part81is arranged circumferentially between two connecting parts31extending radially outwards from the radially external end of two consecutive blades21of the same nozzle1. The circumferential wall83of the intermediate part81thus provides a circumferential support on a said first radial wall65of the radially external platform17of a first blade21and a said second radial wall67of the radially external platform17of a second blade21.

The circumferential wall83longitudinally extends from the upstream radial flange63of the external radial platform17and protrudes downstream of the downstream end of the connecting part31. The circumferential wall83of the intermediate part81comprises first and second circumferential flanks87,89longitudinally extending at the circumferential ends of the circumferential wall83. The two circumferential flanks87,89respectively include an upstream end91a,93a, a first part87a,89a, an intermediate part87c,89c, a second part87b,89band a downstream end91b,93b.

The first and second parts87a,87bof the first circumferential flank87bconform to the shape of the upstream end65aand the downstream end65bof the first radial wall65of the radially external platform17of the first blade21. The intermediate part87cof the first flank87cconforms to the shape of the intermediate part37cof the first wall37of the connecting part31of said first blade31. Respectively, the first and second parts89a,89bof the second circumferential flank89conform to the shape of the upstream end67aand the downstream end of the second radial wall67of the radially external platform17of the second blade21. The intermediate part89cof the second flank89conform to the shape of the intermediate part39cof the second wall39of the connecting part31of the second blade31. In this way, the intermediate part87c,89cof the first and second circumferential flanks87,89ccircumferentially extends but are set back from their respective upstream87a,89aand downstream87,89bends. The upstream and downstream ends93a,93bof the second circumferential flank89circumferentially extend in a protruding manner with respect to the first and second parts89a,89band the intermediate part89c. Thus, two consecutive intermediate parts81are form-fit supported on the entire periphery of the external radial end of the radial flange49of said connecting part31.

The upstream and downstream ends93a,93bof the second circumferential flank89are circumferentially abutting at the upstream and downstream ends91a,91bof the first circumferential flank87of a second intermediate part81. The upstream and downstream ends93a,93bof the second circumferential edge89thus longitudinally extend and protrude from the upstream and downstream ends37a,39a,65a,65b,67aof the first and second walls37,39of the connecting part31as well as the first and second radial walls65,67of the radially external platform17which conform to the shape of said connecting part31. The upstream and downstream ends93a,93bof the second circumferential flank89thus provide longitudinal support on the upstream edge41of the first and second walls37,39of the connecting part31as well as the upstream edge77a,79aof the first and second radial walls65,67of the radially external platform17which conform to the shape of said connecting part31.

The radial wall85of the intermediate part81radially extends in a strictly radial direction from the first and second parts87a,87band the intermediate part87cof the first circumferential flank87c. The radial wall85thus comprises a first part85a, a second part85band an intermediate part85clongitudinally arranged between the first and second parts85a,85b. The radial wall85of the connecting part81extends over a third height H3so that the first and second parts85a,85bof the radial wall85conform to the upstream and downstream ends67aof the second radial wall67of the radially external platform17. On this so-called third height H3, the intermediate part85cof the radial wall85of the intermediate part81conforms to the shape of the intermediate part39cof the second wall39of the connecting part31. The first and second parts85a,85bof the radial wall85extend radially inwards over a fourth height H4with respect to the intermediate part85cof said radial wall85of the intermediate part81. The inner radial ends of the first and second parts85a,85bare flush with the radially internal ends from which the second radial wall67of the radially external platform17extends radially outwards along a strictly radial component.

The first part85a, respectively the second part85b, of the radial wall85of the intermediate part81, as well as the upstream end41, respectively the downstream end41, of the connecting part31and the first and second radial walls65,67of the radially external platform17extending radially along a strictly radial component are provided with a port through which a fastening means53passes. The fastening means53is typically of the bolting type.

Optionally, the radial wall85of the intermediate part81can extend from the second circumferential edge89of the circumferential wall. In this case, the fastening with the connecting part31and the radial walls65,67of the radially external platform17will be identical to what is described in the previous paragraph except that the radial wall85will come substantially in circumferential abutment with the first radial wall65of the adjacent radially external platform17.

Preferably the intermediate part81is made of a metallic material, which allows a CMC nozzle according to the second embodiment of the invention to be fastened to the casing7in a similar way to the nozzles made of a metallic material.

FIGS. 4A and 4Bare now referred to, which represent a CMC nozzle1with a CMC connecting part31attached to the casing7in a third embodiment.

Similarly to the first and second embodiments, the nozzle1comprises a blade21and a connecting part31obtained from a first and second wall37,39respectively consisting of a stack of fibrous impregnated fabrics of a matrix. The first and second walls37,39extend radially outwards. The fibrous fabrics of the first and second walls are connected to each other at the leading edge33and the trailing edge35of the blade21.

The first and second walls37,39of the connecting part31longitudinally extend in a direction having a circumferential component and a longitudinal component substantially similar or parallel to the direction connecting the leading edge33to the trailing edge35of the blade21, in a radially cross-sectional plane. The first wall37of the connecting part31radially extends over a height H5along a radially outward component and along a component transverse to the longitudinal extension, towards the frontside surface from the radially external end of the blade21. The second wall39of the connecting part31radially extends over the same height H5as the first wall37along an outward radial component and a component transverse to the direction of longitudinal extension, towards the backside surface from the external radial end of the blade21. Thus the first and second walls37,39extend towards each other over the same height H5.

The first and second walls37,39radially extend, from the height H5onwards, over a height H6, according to a strictly radial component defining a first and a second radial flange95a,95b. The first and second radial flanges49,95a,95bextend parallel and are spaced from each other.

The spacing of the first and second flanges49,95a,95bforms an opening97leading out in the longitudinal extension direction of the connecting part31. This opening97is in fluid communication with the internal cavity29of the blade21. Thus the radially external off-jet part is in fluid communication with the radially internal off-jet part.

Each of the first and second radial flanges49,95a,95bhas two ports99. The ports99open in the direction transverse to the longitudinal extension direction of the connecting part31. The ports99of the first radial flange95aare coaxial with the ports99of the second radial flange95b, and are preferably longitudinally aligned.

When a nozzle1according to the third embodiment is fastened to the casing7, a radial wall integral with the casing7is arranged between the two radial flanges49,95a,95bof the connecting part31. This radial wall integral with the casing7is also provided with two longitudinally aligned ports and coaxial with ports99of the first and second radial flanges95a,95b. The ports99of the first and second radial flanges49,95a,95bas well as the radial wall integral with the casing7are traversed by two fastening means. Typically, the fastening means are of the bolting type.

Optionally, each of the first and second radial flanges49,95a,95bcan be fastened to an independent radial wall integral with the casing.