Patent Publication Number: US-11035244-B2

Title: Aircraft turbine engine sealing module

Description:
TECHNICAL FIELD 
     The present invention relates to a turbine engine module, which can be a turbine or form part of a turbine, for example. 
     STATE OF THE ART 
     The state of the art comprises, in particular, documents FR-A1-3 914 350 and WO-A1-2016/024060. 
     A turbine engine turbine comprises one or more stages, each comprising a distributor formed of an annular row of fixed blades carried by a casing of the turbine, and an impeller mounted rotating in general downstream of the distributor. The impeller is surrounded by a sealing ring which is sectored and formed by sectors which are arranged circumferentially end-to-end and which are fastened onto the casing of the turbine. 
     Each ring sector generally comprises a circumferentially-oriented body which has an abradable coating fixed on the inner surface of the body. This coating is, for example, of the honeycomb type and is intended to be used by friction on outer seal lips of the blades of the impeller, to form a labyrinth seal and minimise the radial clearances between the impeller and the ring sectors. 
     Each ring sector comprises, at the upstream and downstream ends thereof, fastening means on the casing. Each ring sector can comprise, at the downstream end thereof, a circumferential hook which defines an annular groove, wherein is engaged, on the one hand, an annular rail of the casing, and on the other hand, a fastening spoiler downstream of the distributor located upstream. The hook of the ring has, in the cross-section, a general U- or C-shape and comprises two coaxial circumferential walls, respectively inner and outer, connected together by a median bottom wall. The fastening spoiler, downstream of the distributor has a circumferential orientation and is held clamped radially against the casing rail by way of the circumferential hook upstream of the ring, of which the circumferential walls extend respectively inside the spoiler of the distributor and outside of the casing rail. This makes it possible to contribute to the radial holding of the distributor opposite the casing. 
     It is known to use an annular foil for protecting the casing rail, in particular against wear and high temperatures. This foil can be sectored and thus comprises an annular row of foil sectors arranged circumferentially end-to-end. It has, in the cross-section, a general U- or C-shape and comprises two coaxial circumferential walls, respectively inner and outer, connected together by a median bottom wall. 
     The foil sectors are made of sheet metal and make it possible to avoid the direct contacts between the hooks of the ring sectors and the casing rail, which makes it possible, on the one hand, to protect the latter against wear by friction and on the other hand, to protect it thermally from the ring which can be very hot while functioning due to the proximity thereof with combustion gases flowing into the turbine duct. 
     Due to the sectorisation of the ring, the longitudinal edges of the circumferential ends of two adjacent sectors of the ring are facing one another and are separated from one another by a circumferential clearance through which hot gases of the duct can pass. These hot gases tend to heat the casing, which is damaging for several reasons. One of the reasons, is that a heating of the casing would lead to a dilatation and a deformation of the latter which would risk altering the radial clearances between the mobile impeller and the ring, and therefore decrease the performance of the turbine. Moreover, these gas leaks have an impact on the performance of the turbine engine. For these two reasons, it is necessary to seal, as much as possible, the inter-sector zones. A known solution to this problem consists of inserting seal lips between the ring sectors, which are housed in the slots of the abovementioned longitudinal edges of the ring sectors. 
     However, due to the sectorisation of the foil, the longitudinal edges of the circumferential ends of two adjacent sectors of the foil are facing one another and are separated from one another by a circumferential clearance. In the current technique, the circumferential clearances between the foil sectors can be offset circumferentially with respect to the circumferential clearances between the ring sectors, and in particular, with respect to the circumferential clearances between the hooks of the ring sectors at the level of which it is not possible to mount seal lips of the abovementioned type for size reasons, in particular. Hot gases can thus pass through circumferential clearances between the hooks of the ring sectors and impact the foil sectors, which will heat by conduction, the casing rail, and therefore risks reducing the lifespan thereof. 
     Document WO-A1-2016/024060 proposes to circumferentially offset each foil with respect to the associated hook so as to best protect the casing rail as the gases which would be likely to pass between the edges of the circumferential ends of the ring sectors are blocked by the foil sectors (due to the circumferential offset thereof opposite the ring sectors) and do not reach to the casing rail. However, this solution does not make it possible to protect the casing from inter-sector leaks which occur at the level of the median bottom walls of the hooks of the ring. 
     Document FR-A1-3 914 350 proposes to circumferentially offset the body of the ring sector, with respect to the hook thereof and to the abradable coating thereof. However, this solution is only applicable in the case where the body of the ring sector covers the hook thereof, which is not always the case when an optimisation of the integration is desired. This solution furthermore leads to inter-sector leaks at the level of the hooks of the ring sectors. 
     Moreover, the gases of the duct which are likely to heat and damage the casing leak out of the duct by passing through an axial clearance between the outer periphery of the impeller and the outer periphery of the distributor located upstream of the impeller. These gases pass through this clearance by passing radially inside, outwards, and enter into a delimited annular space, upstream, through the fastening spoiler downstream of the distributor, and downstream, through a seal lip upstream of the impeller. This annular space is therefore the leak gas circulation place, which is likely to pass through the inter-sector clearances and reach the casing. 
     The present invention, in particular relates to providing a simple, effective and economic solution to this need by improving, in particular, the thermal protection of the casing rail in the case above. 
     SUMMARY OF THE INVENTION 
     The present invention thus proposes a turbine engine sealing module, in particular for aircraft, this sealing module extending about an axis and comprising a distributor fixed to a casing and comprising at least one blade connected to an outer platform, the outer platform comprising a spoiler fixed to the casing, the turbine casing further comprising a impeller mounted rotating inside the casing and surrounded by a sealing ring fastened to this casing, this ring being sectored and comprising an annular row of ring sectors arranged such that the circumferential end edges of two adjacent sectors are facing one another, each ring sector comprising a body carrying an abradable coating configured to engage with at least one seal lip carried by the impeller and a hook which extends circumferentially by being located upstream of said abradable coating and which is configured to engage with a fastening rail of the casing, this hook having, in the cross-section, a general C-shape of which the opening is oriented axially upstream and intended to receive said rail. The invention is characterised in that each ring sector further comprises a deflector which is arranged downstream of said coating and which extends radially inwards and upstream with respect to the axis such that the radially inner end thereof extends around a downstream end of the outer platform of the distributor. The invention is also characterised in that each hook has a circumferential extent identical to that of said deflector, and the circumferential ends of said hook are offset in the circumferential direction of the circumferential ends of said deflector. 
     The deflector is thus intended to be located in the abovementioned annular space, between the outer periphery of the impeller and that of the distributor located upstream, and makes it possible to limit the gas circulations in this space. It makes it possible, in particular, to limit the circulation of leak gases at the level of the hook upstream of each ring sector and therefore to reduce the risk of these gases passing into the inter-sector clearances at the level of the hooks thereof. The casing is thus best protected and has an optimised lifespan. 
     The ends offset is also advantageous as the gases which are likely to pass radially inside, outwards through the circumferential clearances between the circumferential ends of the deflectors, are blocked by the hooks which extend facing these clearances, and the gases which are likely to pass radially inside, outwards through the circumferential clearances between the circumferential ends of the hooks, are blocked by the deflector sectors which extend facing these clearances. 
     The module according to the invention can comprise one or more of the following characteristics, taken individually or in combination with one another.
         said deflector comprises an annular sheet metal sector inserted axially between the hook, on the one hand, and the coating and/or body, on the other hand,   the sheet metal sector has, in the cross-section, a general V-shape, of which a radially outer portion extends radially, and of which a radially inner portion is truncated and extends, upstream to downstream, radially inwards,   the hook comprises a median bottom wall which connects two circumferential walls respectively radially inner and outer, the radially outer portion of the sheet metal sector inserted axially between the bottom wall of the hook, and the coating and/or the body,   each deflector has a circumferential extent identical to that of said body and of said coating, and the circumferential ends of said deflector are substantially axially aligned with those of said body and of said coating,   said body comprises, at the circumferential ends thereof of the slots for housing inter-sector seal lips, and said deflector comprises, at the circumferential ends thereof of the notches axially aligned with these slots such that the upstream axial ends of at least some of said seal lips enter into these notches; the seal lips thus extend the closest as possible to the hook, which optimises the inter-sector sealing,   each ring sector comprises, at one of the circumferential ends thereof, at least one seal lip of which the upstream axial end passes through a notch of the deflector and axially bears on a hook of this ring sector, and at the other of the circumferential ends thereof, at least one seal lip of which the upstream axial end passes through a notch of the deflector and bears on a hook of an adjacent ring sector.       

     The present invention also relates to a turbine engine, comprising at least one sealing module such as described above. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The invention will be better understood and other details, characteristics and advantages of the invention will appear upon reading the following description given as a non-limiting example and in reference to the appended drawings, wherein: 
         FIG. 1  is an axial, cross-sectional, partial, schematic half-view of a turbine engine turbine; 
         FIG. 2  is an axial, cross-sectional, partial, schematic half-view of another turbine engine turbine; 
         FIG. 3  is a perspective, partial, schematic view, on a larger scale, of a sealing ring of the turbine of  FIG. 2 ; 
         FIG. 4  is an axial, cross-sectional, partial, schematic half-view of a turbine engine module according to the invention; 
         FIG. 5  is a perspective, schematic view of a sealing ring sector of the module of  FIG. 4 ; and 
         FIGS. 6 and 7  are perspective, schematic views, on a larger scale, of the inter-sector clearances of the sealing ring of the module of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     First,  FIG. 1  is referred to, which represents a turbine  10 , here low-pressure, of a turbine engine such a turbine engine or an aircraft turboprop, this turbine comprising several stages (only one of which is represented here) each comprising a distributor  12  formed of an annular row of fixed blades carried by a casing  14  of the turbine, and an impeller  16  mounted downstream of the distributor  12  and rotating about an axis (not visible) in a ring  18  fastened to the casing  14 . 
     The ring  18  is sectored and formed of several sectors which are carried circumferentially end-to-end by the casing  14  of the turbine. 
     Each ring sector  18  comprises a body  20  which extends circumferentially and a coating  22  of abradable material fixed by soldering and/or welding on the radially inner surface of the body  20 , this coating  22  being of the honeycomb type and being intended to be used by friction on the outer seal lips  24  of the blades of the impeller  16  to minimise the radial clearances between the impeller and the ring sectors  18 . The seal lips  24  are formed protruding over an outer platform  16   a  of the impeller  16 , the outer platform  16   a  being connected to a blade of the impeller. 
     Each ring sector  18  comprises, at the upstream end thereof, a hook  32  with a C- or U-shaped cross-section which extends circumferentially and of which the opening opens upstream, this hook  32  being axially engaged from downstream on a fastening spoiler  34  oriented towards the downstream of the distributor  12  which extends circumferentially upstream of the ring sectors  18 , on the one hand, and on a cylindrical rail  36  of the casing  14  on which is fastened this distributor, on the other hand. The spoiler  34  has a general L-shape and protrudes from a platform  12   a  of the distributor  12 , to which are connected at least one blade of the distributor. 
     The hook  32  of each ring sector  18  comprises two walls  38  and  40  extending circumferentially and upstream, each wall, respectively radially outwards and radially inwards are connected together at the downstream ends thereof by a substantially radial median bottom wall  42 , and which extend respectively radially outside and inside the rail  36 , the inner wall  40  radially holding the spoiler  34  of the distributor against the rail  36 . 
     Such as illustrated in  FIG. 1 , the circumferential holding of the distributor  12  is ensured by way of an anti-rotating pin  44  which is carried by the casing  14  and is engaged in a notch of the distributor  12 . The axial holding thereof downstream is ensured by an annular split ring  46  which is mounted in an annular groove  48  of the rail  36 , which opens radially inwards. In this case, the spoiler  34  of the distributor  12  axially bears downstream on the ring  46  which is held radially in the groove of the casing rail by the inner wall  40 , which extends radially inside the ring  46 . In a variant, the axial stopping function of the ring  46  can be ensured directly by the casing rail  36 . 
     The downstream ends of the ring sectors  18  are radially clamped on a cylindrical rail  30  of the casing by the distributor located downstream of the ring sectors. The ring sectors  18  radially bear outwards on a radially inward cylindrical face of the rail  30  of the casing, and inwards on a radially outward cylindrical face of a cylindrical edge  28  of the downstream distributor. The downstream ends of the ring sectors  18  are furthermore clamped axially via the lugs on the cylindrical rail  30 . 
     To thermally protect the rail  36 , and against the wear, it is also known to use an annular foil  50  which is sectored and comprises an annular row of foil sectors arranged circumferentially end-to-end. It has, in the cross-section, a general C- or U-shape and comprises coaxial annular walls, respectively inner  52  and outer  54 , connected together by a median bottom wall  56 . 
     The foil  50  is mounted on the casing rail  36  and on the spoiler  34  of the distributor  12  such that the inner walls  52  of the foil sectors  50  are inserted between the inner walls  40  of the hooks  32  of the ring sectors  18 , on the one hand, and the spoiler  34  of the distributor  12  and the annular ring  46 , on the other hand, that the outer walls  54  of the foil sectors are inserted between the outer walls  38  of the hooks  32  of the ring sectors and the casing rail  36 , and that the bottom walls  56  of the foil sectors are inserted between the bottom walls  42  of the hooks of the ring sectors and the casing rail  36 . 
     The foil sectors  50  are made of sheet metal and make it possible to avoid the direct contacts between the hooks  32  of the ring sectors  18  and the casing rail  36 , which makes it possible on the one hand to protect the latter against wear by friction and on the other hand, to thermally protect it from the ring which can be very hot while functioning, due to the proximity thereof with the combustion gases flowing into the turbine duct. 
     To avoid gas leaks towards the casing  14 , it is also known to mount seal lips  58  at the level of the inter-sector circumferential clearances. The longitudinal edges of the circumferential ends of the ring sectors comprise mounting slots for the seal lips  58 . The seal lips  58  each have a general extended and flat shape and each comprise a longitudinal edge engaged in a slot of the edge of a ring sector and an opposite longitudinal edge engaged in a slot of the edge facing an adjacent ring sector. 
       FIG. 1  represents a first sealing technology  18  wherein the body and the hook  32  are formed of one single part. 
       FIG. 2  represents a second sealing ring technology  18  wherein the body  20  and the hook  32  are formed of assembled parts. The references used in  FIG. 2  are the same as those of  FIG. 1 , insofar as they designate the same elements. 
     The second technology covers the case where the hook  32  is fixed under the body, just upstream of the coating  22  (as is the case in application FR-A1-3 914 350), as well as the case where the hook  32  is fixed upstream of the body, as is the case in the example represented. 
     While functioning, combustion gases flow upstream to downstream in the turbine duct, through the blades of the distributors  12  and the module blades of the impellers  16 . The outer periphery of each distributor  12  is separated by an axial clearance J of the outer periphery of the adjacent impeller  16 , which can be passed through by leak gases. The engagement of the seal lips  24  with the abradable coating  22  limits the passage of these leak gases upstream to downstream between the impeller  16  and the ring  18 . The leak gases thus circulate in the annular space E extending radially between the outer platforms  12   a ,  16   a  of the distributor  12  and of the impeller  16 , and axially between the downstream spoiler  34  of the distributor  12  and the upstream seal lip  24   a  of the impeller  16 . 
     The strips  58  limit the passage of gases from the space E radially outwards, at the level of the circumferential clearances between the bodies  20  of the ring sectors. However, as can best be seen in  FIG. 3 , the circumferential clearances are always present between the hooks  32  and gases can pass from the space E radially outwards, in particular between the median bottom walls  42  of the hooks  32  (arrow F). 
       FIG. 4  and below represent an embodiment of the invention which makes it possible to resolve at least some of these problems. The references used in  FIG. 3  are the same as those of the preceding figures insofar as they designate the same elements. 
     The ring  18  differs from that described above, in particular in that each ring sector further comprises a deflector  60  which is arranged upstream of the coating  22  and which extends radially inwards with respect to the abovementioned axis such that the radially inward end thereof extends around the downstream end of the outer platform  12   a  of the distributor  12 . In the example represented, the deflector  60  is formed by an independent part of the hook  32  and of the body  20 , and which is inserted axially between the hook  32  located upstream, and the body  20  and the coating  22  located downstream. The deflector  60  can be formed by an annular sheet metal sector. 
     The deflector  60  here has a general curved orientation and a general V-shape. It thus comprises a radially outward portion  60   a  extending into a plane, substantially perpendicular to the abovementioned axis, and a radially inward portion  60   b  which is truncated. 
     The portion  60   a  is inserted between the median bottom wall  42  of the hook  32  and the upstream ends of the body  20  and of the coating  22 . 
     The portion  60   b  extends downstream to upstream, radially inwards. The inner periphery thereof defines a diameter D which is less than the smallest inner diameters D 1 , D 2  of the hook  32  and of the coating  22 . This inner periphery here surrounds, with a small radial clearance, the end of the outer platform  12   a  of the distributor  12  ( FIG. 4 ). 
     The deflector  60  has a circumferential extent about the axis which is identical to that of the body  20  and of the coating  22 . The circumferential ends of the deflector  60  are substantially aligned axially with those of the body and of the coating  22 , as can be seen in  FIG. 5 . 
       FIG. 5  makes it possible also to see that the deflector  60  comprises, at the circumferential ends thereof, notches  62  aligned axially with the slots  64  for housing inter-sector sealing strips  58 . These notches  62  are designed to be able to be passed through by the strips  58 . Each notch  62  has a height (or radial dimension) at least equal to the height (or radial dimension of the slots  64  for housing the strips), and a width (or circumferential dimension) at least equal to the circumferential dimension between the bottoms of the two slots  64  facing the housing for the strips. 
     It will be noted in the drawings, that the longitudinal edge of each circumferential end of a ring sector can comprise two slots  64  for housing two strips  58 , which have different lengths and extend on top of one another in the radial direction. The upstream ends of the slots  64  are joined at the upstream end of each edge and both communicate with the notch  62 , even if the two strips  58  of each edge are likely to pass through the notch  62  ( FIGS. 4 and 5 ). In a variant, the edge of each circumferential end of a ring sector could carry one single strip  58 . 
     Each hook  32  has a circumferential extent identical to that of the deflector  60 , and the circumferential ends of the hook  32  are offset in the circumferential direction of the circumferential ends of the deflector ( FIG. 5 ). Each hook  32  thus comprises a circumferential end portion  32   a  which protrudes with respect to the circumferential ends of the other parts of the ring sector, and another circumferential end portion  32   b  which is removed with respect to the circumferential ends of the other parts of the ring sector ( FIG. 5 ). 
     During the mounting of the ring  18  on the casing, it is understood therefore that the ring sectors will be circumferentially interlocked together ( FIG. 6 ). 
     At the level of the circumferential end of each ring sector comprising the protruding end portion  32   a , the strips  58  axially bear on this end portion (the support zone Z can be seen in  FIGS. 6 and 7 ). At the level of the circumferential end of each ring sector comprising the removed end portion  32   b , the strips  58  bear axially not on this end portion  32   b , but on the end portion  32   a  of the adjacent ring sector. 
     As can be seen in  FIG. 4 , the deflector  60  extends into the space E located between the hook  32  and the end  12  of the outer platform  12   a  of the distributor and splits it into two respectively upstream and downstream portions. The shape thereof imposes on the leak gases passing through the clearance J of flowing downstream in the direction of the labyrinth seal defined by the seal lips  24 . There is therefore less risk of leak gas circulation at the level of the hooks  32  of the ring sectors. The inter-sector clearances at the level of these hooks are moreover sealed due to the circumferential offset between the hooks  32  and the deflectors  60 . The invention thus makes it possible to effectively protect the casing  14  and improve the lifespan thereof and also avoid losses from the duct to the casing, which improves the efficiency of the turbine engine.