Patent Publication Number: US-2023142040-A1

Title: Turbine assembly, and gas turbine engine provided with such an assembly

Description:
FIELD OF THE INVENTION 
     The invention relates to a turbine assembly comprising a plurality of ring sectors made of ceramic-matrix composite (CMC) material, assembled to form a turbine ring, and a ring support structure. 
     The field of application of the invention is in particular that of aeronautical gas turbine engines or turbomachines. The invention is however applicable to other turbomachines, for example industrial turbines. 
     STATE OF THE ART 
     In aeronautical gas turbine engines, the improvement of efficiency and the reduction of some polluting emissions lead to the search for an operation at ever higher temperatures. From the state of the art, an all-metal turbine ring assembly is already known. It is however necessary to cool all the elements of this assembly and particularly the turbine ring, because the latter is subjected to very hot streams whose temperature is higher than the temperature that the metal materials can withstand. 
     However, this cooling has a significant impact on the performance of the engine, because the cooling stream used is taken from the main stream of the engine. Furthermore, the use of metal for the turbine ring limits the possibilities of increasing the temperature at the turbine, which would nevertheless improve the performances of the aeronautical engines. 
     In an attempt to solve the aforementioned problem, it was envisaged to produce a turbine ring sector made of ceramic-matrix composite (CMC) material, in order to avoid the use of a metal material. 
     The ceramic-matrix composite materials are known to maintain their mechanical properties at temperatures significantly higher than metals, which makes them able to constitute elements of hot structure. The use of this type of materials allows reducing the cooling flow rate of the parts and therefore increasing the performance of the turbomachine. In addition, the CMC materials have the advantage of having a lower density than that of the metals usually used to produce a turbine ring. This allows envisaging a significant mass gain in the whole turbomachine. 
     The production of turbine ring sectors in a single piece of CMC material is in particular described in document US 2012/0027572. The ring sectors include an annular base whose inner face defines the inner face of the turbine ring and an outer face, from which two legs radially extend the ends of which are held between the two flanges of a metal ring support structure. 
     The use of CMC ring sectors thus allows significantly reducing the ventilation required to cool the turbine ring. However, the CMC having a different mechanical behavior from that of a metal material, its integration as well as the way of positioning it within the turbine had to be redesigned. Indeed, the CMC does not withstand shrink-fitted mounting (usually used for metal rings) and its thermal expansion is lower than a metal material. 
     Document WO 2015/191 169 already discloses a turbine assembly comprising a plurality of turbine ring sectors made of ceramic composite material, a support structure held by an outer casing, (this structure comprising an annular shroud and annular spacer sectors), and an air deflector which diffuses air. 
     Document WO 2015/108 658 also discloses a turbine assembly which comprises a ring support structure and a plurality of turbine ring sectors which together form a turbine ring. This assembly also comprises a deflector provided with a passage allowing the introduction of cooling air on the radially inner face of the turbine ring sector. 
     Finally, document EP 3 118 417 discloses a turbine assembly which comprises a plurality of turbine ring sectors made of CMC ceramic materials and a ring support structure. A deflector can be disposed radially between the support and the ring sector. 
     However, none of these documents describes or suggests the mounting of the air diffuser by interlocking on one of said spacer sectors, nor the structure of the air diffuser in accordance with the invention. 
     DISCLOSURE OF THE INVENTION 
     One aim of the invention is to propose a turbine ring assembly which does not have the aforementioned drawbacks and in particular which is lighter than the turbine ring assemblies known from the state of the art, with, in particular the removal of all the bolted connections, usually present in this kind of integration. 
     To this end, the invention relates to a turbine assembly extending about a longitudinal axis, this assembly comprising:
         a plurality of turbine ring sectors made of ceramic-matrix composite material, assembled circumferentially end to end to form a turbine ring, each turbine ring sector comprising a base with a radially inner face and a radially outer face from which an upstream leg and a downstream leg axially spaced apart from each other radially extend outwardly,   a ring support structure, held by an outer annular turbine casing, said ring support structure comprising an annular shroud, and a plurality of angular spacer sectors together forming an annular spacer, said annular spacer being fixed to said annular shroud, and each turbine ring sector being fixed, by said legs, on said annular spacer,   at least one air diffuser, configured to diffuse cooling air on said radially outer face of at least one of said turbine ring sectors.       

     In accordance with the invention, said at least one air diffuser is mounted by interlocking on one of said angular spacer sectors, in an interlocked position, the air diffuser has an inner cavity and a radially inner face pierced with a plurality of air ejection orifices opening out into this cavity, each angular spacer sector has a radially inner face and has on its radially inner face, a rectilinear interlocking slot, which has on part of its length, an interlocking area with a T-shaped cross-section and each air diffuser is provided, in its radially outer portion, with an also T-shaped attachment member, configured to be able to be received and interlocked into said interlocking area, the attachment member of the air diffuser is pierced with an air intake hole opening out into said inner cavity and each angular spacer sector comprises at least one air supply duct, opening out on the one hand onto one of its upstream faces and on the other hand into the bottom of the T-shaped interlocking area of the slot, facing the mouth of the air intake hole of the attachment member of the diffuser, when this diffuser is in its interlocked position, so that this air supply duct is in fluid communication with said air ejection orifices. 
     Thanks to these characteristics of the invention, and in particular to the interlocking of the air diffuser on one of the angular spacer sectors, the mounting of the diffuser is simplified, it is no longer necessary to use sleeves or pins for its fixing and the overall mass of the turbine ring assembly is reduced. 
     Furthermore, this mounting allows maintaining the use of a ring made of ceramic-matrix composite material and the associated advantages. 
     According to other advantageous and non-limiting characteristics of the invention, taken alone or in combination:
         said attachment member comprises at least one abutment cooperating with the T-shaped interlocking area of said interlocking slot, so as to block the axial displacement of the air diffuser, once the latter is in the interlocked position;   each angular spacer sector comprises an upstream hook oriented axially downstream and a downstream finger, the annular shroud comprises two annular grooves opening out upstream, and in that these grooves are intended to receive respectively said upstream hook and said downstream finger;   each spacer sector is provided with an upstream flange, and a nozzle of the turbine, forming a crown disposed upstream of said turbine ring assembly presses axially against this upstream flange, in order to hold said upstream hook and said downstream finger respectively in the corresponding grooves of the annular shroud;   said annular shroud comprises a downstream flange, this downstream flange having, in the axial direction of the turbine ring, a thickness generally smaller than the thickness of the downstream leg of the ring sector, the downstream flange exerting a stress on the downstream leg of the ring sector;   said upstream leg of a ring sector is fixed on the upstream flange of the spacer sector using fixing slugs, each spacer sector comprises several downstream lugs and said downstream leg of a ring sector is fixed on at least one downstream lug of this same spacer sector using fixing slugs, the slugs extending mainly axially;   each angular spacer sector has at its two circumferential ends, sealing slots for receiving sealing tabs, these sealing tabs being disposed in said sealing slots between two angular spacer sectors disposed circumferentially end to end.       

     The invention also relates to a turbomachine comprising a turbine assembly, as mentioned above. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       Other characteristics, aims and advantages of the invention will emerge from the following description which is purely illustrative and not limiting, and which should be read relation to the appended drawings in which: 
         FIG.  1    represents a longitudinal sectional view of a turbine assembly in accordance with the invention, mounted in a turbomachine. 
         FIG.  2    is an enlarged longitudinal sectional view of a turbine assembly in accordance with the invention. 
         FIG.  3    is an elevational view of one end of an angular spacer sector. 
         FIG.  4    is a perspective view of an air diffuser in accordance with the invention. 
         FIG.  5    is a perspective and transparent view of an angular spacer sector, on which two diffusers are mounted. 
         FIG.  6    is a bottom view of an angular spacer sector on which a diffuser is mounted. 
         FIG.  7    is a view similar to  FIG.  6    but without the diffuser. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A turbine assembly  1  in accordance with the invention will now be described in relation to  FIGS.  1  and  2   . This assembly  1  extends about a longitudinal axis X-X′. 
     In  FIG.  1   , the arrow D A  indicates the axial direction of the turbine assembly  1 , while the arrow D R  indicates its radial direction. For reasons of simplification of the representation,  FIGS.  1  and  2    are partial views of this assembly, which is in reality annular. 
     This assembly  1  comprises in particular a turbine ring  2  made of ceramic-matrix composite (CMC) material, centered on the longitudinal axis X-X′ and a ring support structure  3 , held by an outer annular turbine casing  4 , the latter being visible only in  FIG.  1   . 
     The turbine ring  2  surrounds a turbine blade assembly  5 . 
     In the remainder of the description, the turbine described is a high-pressure turbine. However, the invention also applies to a low-pressure turbine. 
     The turbine ring  2  is formed of a plurality of angular ring sectors  20 , which are placed end to end circumferentially to form a ring. 
     Each angular ring sector  20  has a section substantially in the shape of an inverted Greek letter Pi (or π), with a base  21 , having a radially inner face  211 , which defines an angular portion of the inner face of the turbine ring  2  and a radially outer face  212 , which defines an angular portion of the outer face of the turbine ring and from which an upstream leg  22  and a downstream leg  23  radially extend outwardly. 
     The terms “upstream” and “downstream” are used here with reference to the direction of flow of the gas stream, inside the turbine ring, represented by the arrow F in  FIGS.  1  and  2   . The two legs  22  and  23  extend over the entire width of the ring sector, in the direction circumferential. They are axially spaced apart from each other. 
     The upstream leg  22  is pierced with a plurality of axial orifices  220  and the downstream leg  23  is pierced with a plurality of axial orifices  230 . 
     Conventionally, the sealing between two neighboring angular sectors  20  is ensured by sealing tabs (not visible in the figures), housed in sealing slots  24  arranged at the two ends of each ring sector  20 , the slots  24  facing each other when two sectors  20  are assembled end to end. 
     The ring support structure  3  comprises several distinct parts, assembled to each other, namely an annular shroud  6 , and in accordance with the invention, an annular spacer  7 . 
     The annular shroud  6  can be formed by a revolution part, that is to say extending over 360°, or produced by an assembly of a plurality of angular sectors placed end to end. 
     As best seen in  FIG.  2   , the annular shroud  6  has an upstream annular groove  61 , which opens out upstream, a median annular groove  62 , which also opens out upstream and finally a downstream annular groove  63 , which opens out downstream. These different annular grooves are centered on the longitudinal axis X-X′ and they extend axially. 
     The downstream annular groove  63  is intended to receive the end of a blade of a nozzle A (here for example a low-pressure nozzle) of the low-pressure turbine, disposed downstream of the high-pressure turbine and visible only in  FIG.  1   . 
     In addition, the annular shroud  6  comprises an annular downstream flange  64 , which extends radially inwardly and whose end  640  is curved upstream so as to extend axially. The thickness of this flange  64  in its radial portion is sufficiently small so that it maintains an elastic, flexible nature. 
     Finally, the annular shroud  6  has on its radially outer face, a protrusion  65 , intended to come into abutment radially against the outer casing  4 . The shroud  6  is fixed on this casing  4  by fixing means not visible in the figures (shrink-fitting). According to another variant of embodiment not represented in the figures, the shroud can be made in one piece with the outer casing  4 . 
     The annular spacer  7  consists of a plurality of angular spacer sectors  70 , assembled circumferentially end to end. 
     One of these spacer sectors  70  appears better in  FIG.  5   . Each sector  70  comprises a curved body  71  which has a radially outer face  711  and a radially inner face  712 . The curved downstream edge of this body  71  defines an axially oriented downstream finger  713 . This downstream finger  713  is intended to be inserted into the median annular groove  62  of the shroud  6 . As can be seen better in  FIG.  2   , the assembly of the spacer  7  and of the shroud  6  is made so that the radially outer face of the downstream finger  713  is pressed against the radially inner face of the median annular groove  62 , and this, so as to ensure the sealing between the two parts. 
     An upstream hook  714  in the form of a ring sector, oriented axially downstream protrudes outwardly from the upstream end of the radially outer face  711 . This upstream hook  714  is intended to be inserted into the upstream annular groove  61  of the annular shroud  6 . As can be seen in  FIG.  2   , the assembly of the spacer  7  and of the shroud  6  is made so that the radially outer face of the upstream annular groove  61  is pressed against the radially inner face of the upstream hook  714 , and this, so as to ensure the sealing between the two parts. 
     In  FIG.  2   , it can also be seen that the contact of the downstream finger  713  upwardly and of the upstream hook downwardly guarantees the radial positioning of each spacer sector  70  with respect to the annular shroud  6  (tilting effect). 
     In addition, the body  71  comprises an upstream flange  72  and a plurality of downstream lugs  73 . In  FIG.  5   , it can be seen that these lugs  73  are for example two per sector  70 . Each lug  73  is pierced with an axial orifice  730 . Furthermore, the flange  72  has several blind, axial cavities  720  opening out downstream. 
     The upstream flange  72  and the downstream lugs  73  extend radially or substantially radially in the direction of the interior of the ring assembly  1 , that is to say in the direction of the axis X-X′. 
     The turbine ring assembly  1  further comprises upstream axial slugs  24  and downstream axial slugs  25 . The upstream axial slugs  24  are inserted into the blind cavities  720  and through orifices  220 , so as to ensure the fixing of the upstream leg  22  of the ring sector  20  on the upstream flange  72 . The downstream axial slugs  25  are inserted through the axial orifices  730  of the spacer  7  and  230  of the ring sector  20 , so as to ensure the fixing of the downstream leg  23  of the ring sector  20  on the lugs  73 . The different axial slugs are evenly distributed about the longitudinal axis X-X′ of the ring. 
     When the assembly is done, the lugs  73  are disposed upstream of the downstream leg  23  of the ring  2  and the upstream flange  72  is upstream of the upstream leg  22 . 
     In addition, the upstream  22  and downstream  23  legs of each ring sector  20  are held respectively between the upstream flange  72  and the flange  64 , which each exert an axial stress on these legs, the end  640  of the flange  64  pressing against the downstream face of the downstream leg  23 , these axial stresses being opposed. 
     The upstream flange  72  is generally thicker in the axial direction (with the exception of the areas provided with the casings  720 ) than the radial portion of the flange  64 . The upstream flange  72  is therefore more rigid and the flange  64  is more flexible and deformable. 
     Finally, as can be seen in  FIG.  1   , the turbine ring assembly  1  is disposed between two nozzle stages, here between the nozzle A for example low-pressure nozzle and the nozzle B, for example here high-pressure nozzle of the high-pressure turbine. This nozzle B, disposed upstream of the turbine ring assembly  1  presses axially against the upstream flange  72 . Thus, in operation, the take-up of the forces of the nozzle B is ensured by the spacer  7  by limiting the transmission of these forces to the CMC ring  2 , due to the high stiffness of the upstream flange  72 . The transmission of the forces to the ring  2  is also limited by the flexible nature of the downstream flange  64 . 
     Finally, once the assembly has been done, the annular shroud  6  surrounds the annular spacer  7 , which itself surrounds the ring  2 , so that these three elements are concentric and coaxial, with a longitudinal axis X-X′. 
     Advantageously, and as best seen in  FIG.  5   , each angular spacer sector  70  has at its both ends, sealing slots  721  for receiving sealing tabs. These tabs, not represented in the figures, are disposed between two angular spacer sectors  70 , disposed circumferentially end to end. This allows ensuring the sealing between two neighboring sectors  70 . 
     Preferably, these sealing slots  721  are arranged at the two ends of the upstream flange  72 , as well as at the two ends of the hook  714 . 
     The turbine assembly  1  also comprises an air diffuser  8 , intended to diffuse cooling air on the radially outer face  212  of the base  21 . This air diffuser  8  comprises walls which delimit an interior cavity  80  (see  FIG.  2   ). In the exemplary embodiment represented in the figures, the walls of this air diffuser have the shape of a truncated pyramid. 
     This air diffuser  8  has a preferably planar radially inner wall  81  pierced with a plurality of air ejection orifices  810 . 
     According to the invention, each air diffuser  8  is mounted by interlocking on one of the angular spacer sectors  70 . In the example represented in  FIG.  5   , two air diffusers  8  are mounted on an angular spacer sector  70 . They are in a position called “interlocked” position. 
     To this end, each angular spacer sector  70  has on one of its radially inner faces, here its face  712 , a rectilinear interlocking slot  74  (see  FIGS.  5  to  7   ). This slot is rectilinear, that is to say not curved, whereas it is arranged in the body  71  which is curved. 
     Advantageously, the spacer sectors  70  are manufactured by additive manufacturing. 
     In addition, this slot  74  has on part of its length, preferably its central portion, a T-shaped cross-section, forming an interlocking area  742 . This T-shaped cross-section appears better on the section of  FIG.  3   . At this location, the slot  74  is punctually provided with two tabs  740  facing each other and spaced apart from each other, so as to delimit the two branches of the T. 
     Furthermore, as best seen in  FIG.  4   , the air diffuser  8  has at its radially outer portion, here at the top of the truncated pyramid, an also T-shaped attachment member  82  configured to be able to be received and interlocked by sliding in the slot  74 . As the latter is rectilinear, the sliding is facilitated. 
     Advantageously, this attachment member  82  has at one of its ends, two abutments  821 , disposed on either side of the T. The horizontal branch  822  of the T-shaped attachment member is configured to be received in the slot  74  between the bottom of the latter and the two tabs  740 , while the vertical branch  823  of the T is received between the two tabs  740 . The radially outer face  824  of the member  82  is planar. 
     Complementary interlocking shapes of the attachment member  82  and of the slot  74 , other than a T-shape, could also be envisaged. 
     The air diffuser  8  can thus be inserted by axial sliding into the slot  74 , from one of the ends of the sector  70  (insertion arrow G in  FIG.  6   ), the tabs  740  retaining the horizontal branch  822  of the T, until the two abutments  821  come into contact with the two respective tabs  740 . These abutments  821  thus block the axial sliding of the air diffuser  8  inside the slot  740 . The diffuser  8  cannot move further towards the center of the spacer sector  70 . Additional wedges, not represented in the figures, can be added to prevent the displacement of the diffuser  8  in the direction opposite to that of its insertion. 
     In addition, the attachment member  82  is pierced with at least one air intake hole  825  which opens out both onto the outer face  824  of the attachment member  82  and inside the cavity  80 . 
     Each angular spacer sector  70  further comprises at least one air supply duct  75  (in the embodiment represented in  FIG.  5   , two ducts  75 ). Each duct  75  opens out on the one hand onto the upstream face  76  of the angular sector  70  and on the other hand into the bottom of the slot  74 , facing the slot portion  74  having a T-shaped section (interlocking area  742 ). As can be seen in  FIG.  5   , the duct  75  is configured so that when the air diffuser  8  is positioned in abutment inside the slot  74 , against the tabs  740 , (interlocked position), this duct  75  opens out at the mouth of the air intake hole  825  of the attachment member  82  of the diffuser  8 . 
     Thus, the cooling air, taken from a stage of the compressor of the turbomachine, enters the duct  75  then the diffuser  8  where it is ejected via the air ejection orifices  810 , in the direction of the inner face  212  of the ring sector base  21 , thus leading to the cooling of the latter. 
     Advantageously, the shroud  6 , the spacer  7  and the diffuser  8  are made of metal.