Sealing between segments of stator nozzle ring of a turbomachine

Abstract

Angular sector of a fixed blading ring of a turbomachine (10), in particular of a stator or distributor, said sector extending through a given angle about an axis A of said ring and comprising, with respect to said axis A, a radially outer platform, a radially inner platform, at least two blades extending between said platforms, and at least one block of abradable honeycomb material (44a) that extends inwardly with respect to the inner platform between transverse ends (52a) of the sector (34a) and that comprises radially oriented tubular cells (54a), in which the block of abradable material (44a) comprises at least one transverse end wall (52a) at which all of the cells are open by openings (56a1, 56a2) oriented away from said sector (34a).

Description

[0001] The invention relates to an angular sector of a turbomachine blade, in particular an angular sector of a blade of a rectifier equipping a compressor or a distributor equipping a turbine of this turbomachine. STATE OF PRIOR ART

[0002] Gas turbine engines comprise, in a known manner, fixed internal blade rings, which are mounted in external casings of a primary flow path of the engine and which are axially interposed between moving compressor blade wheels or between moving turbine blade wheels of these engines. Each fixed blade ring is mounted with a dynamic seal around a compressor or turbine rotor. For this purpose, each fixed blade ring internally comprises a block of abradable material which is intended to cooperate with lip seals integral in rotation with the associated compressor or turbine rotor to ensure a gas seal.

[0003] Some of the gases are nevertheless likely to insinuate themselves between the fixed blades and the moving blades of the compressor or turbine rotors, in the opposite direction to the main flow circulating in the primary flow vein.

[0004] The fixed internal blade rings constitute rectifiers when they are interposed between compressor wheels, or constitute distributors when they are interposed between turbine wheels.

[0005] In order to facilitate their assembly and reduce their manufacturing cost, fixed blade rings are often made in the form of an assembly of angular sectors which are juxtaposed next to each other to form a complete ring of fixed blades.

[0006] In some configurations, such as that of document US-2015-0304463-A1, the block of abradable material is a single piece and made in the form of a ring. This configuration provides satisfactory sealing but is very bulky.

[0007] When the blocks of abradable material are segmented into angular sectors, the crowns reveal an inter-sector clearance which leaves recirculation passages for the gases, no longer around the feet of the angular sectors, but between them.

[0008] Indeed, conventionally, part of the gases that pass from upstream to downstream through the fixed blades tends to recirculate from downstream to upstream through the seal that is made between the block of abradable material and the lip seal according to a leakage flow that we seek to keep as minimal as possible, because it affects the performance of the corresponding compressor or turbine. Another part of the gases that pass from upstream to downstream through these blades tends to recirculate from downstream to upstream by insinuating itself between the sectors through the gap between the sectors, also called inter-sector gap.

[0009] The difficulty in ensuring a satisfactory level of sealing lies in the fact that the angular sectors of the crown move due to mechanical and thermal deformations occurring during engine operation. Thus, the clearance between the sectors and the leakage flow vary during engine operation. The hot clearance during engine operation must also never be zero because contact between the sector platforms could cause ovalization of the casing which is external to the fixed blade and / or peening of the contacting surfaces, which could drastically increase the stresses exerted on the fixed blade, with the consequence of transferring these stresses to the external casing of the engine which houses the fixed blade.

[0010] A transfer of these constraints can result in ovalization of the outer casing and significantly modify the radial clearances between this casing and the neighboring moving blades, with a very negative impact on the engine in terms of service life.

[0011] Conventionally, the sealing between two immediately adjacent angular sectors of fixed blade crowns is ensured by tongue sealing systems interposed between these sectors in order to limit leaks between sectors. These sealing systems can be used to ensure the sealing of fixed blade crown sectors placed in the primary flow path, and also, in the case of a double-flow engine, to ensure the sealing of fixed blade crown sectors placed in the secondary flow path.

[0012] In this technology, tabs are housed between two adjacent sectors in recesses that have been machined into the sectors. The tabs prevent the flow of gases passing through the inter-sector gap.

[0013] Conventionally, an angular sector of a blade crown comprises, relative to the axis of the crown, a radially outer platform substantially in the form of an angular section of a cylinder, a radially inner platform in the form of an angular section of a cylinder, at least two blades which extend between said platforms, a root linked to the inner platform and at least one block of abradable honeycomb material which extends internally to the root, as described in documents FR-2.552.159-A1 and JP-2008 / 180149-A. The tabs interposed between two sectors are embedded in the mass of the two adjacent roots of the two sectors and in housings facing the adjacent inner and outer platforms of the two sectors. Documents FR-2.732.416-A1, EP-1.229.213-A1, and EP-0.017.534-A1 describe such configurations.

[0014] However, these tabs are not easy to install. In addition, they require the creation of housings in the angular sectors of the fixed blade crown, which are expensive to manufacture.

[0015] As for the sealing made internally to the inner platform, the tabs cannot be arranged along the entire radial thickness of the foot. Consequently, there are gaps between the sectors through which gases can circulate.

[0016] Document DE-10305899-A1 proposed a solution comprising a seal between the blocks of abradable material by means of open cells facing each other, but this solution was only applied to blade sectors without a radially external platform.

[0017] There is therefore a need for an alternative sealing technology that can eliminate the need for such tabs and improve the seal between the fixed blade crown sectors. STATEMENT OF THE INVENTION

[0018] The invention proposes to this end to take advantage of the block of abradable material arranged inside the inner platform to ensure a seal directly between transverse end walls of two angular sectors of adjacent fixed blade crowns.

[0019] For this purpose, the invention proposes an angular sector of a ring of fixed blades of a turbomachine, in particular a rectifier or distributor, said sector extending at a determined angle around an axis A of the ring of fixed blades and comprising, with respect to the axis A of said ring of fixed blades, a radially outer platform, a radially inner platform, at least two blades which extend between said platforms, and at least one block of abradable honeycomb material which extends internally to the inner platform between transverse ends of the sector and which comprises radially oriented tubular cells, characterized in that the block of abradable honeycomb material comprises at least one transverse end wall at which all the cells are open via openings which are turned towards the side opposite said sector.

[0020] According to other characteristics of the angular sector: the block of abradable material extends radially to the platform, the openings of the cells are all arranged in the same plane of said wall, the opening of each cell is of a width corresponding to a total width of said cell, the cells are identical and of polygonal shape.

[0021] The invention also relates to an assembly of two adjacent angular sectors of the type described above, characterized in that the transverse end walls of said adjacent angular sectors comprise open cells which are turned towards each other and in that the cells of the end wall of one of said adjacent angular sectors are offset by a determined offset in the axial direction relative to those of the end wall of the other of said adjacent angular sectors.

[0022] According to other characteristics of the assembly: the cells of the adjacent angular sectors are arranged in a staggered pattern, the cells of the end wall of one of the adjacent angular sectors being offset in the axial direction relative to those of the end wall of the other of the adjacent angular sectors by a determined offset equal to half the width of a cell, the plane of the openings of the cells of the end wall of one of the adjacent angular sectors forms a determined clearance with the plane of the openings of the cells of the end wall of the other of the adjacent angular sectors, the determined clearance is zero or negative so that the axially offset open cells form baffles.

[0023] The invention finally relates to a ring of fixed blades for a turbomachine comprising a plurality of angular sectors of ring of fixed blades, characterized in that it comprises a determined number of sectors whose juxtaposition forms the entire ring of fixed blades, in that each angular sector of ring of fixed blades comprises two opposite transverse end walls at the level of which all the cells are open and in that each angular sector of ring of fixed blades is assembled with each of the angular sectors of ring of fixed blades which are adjacent to it to form an assembly of the type described above. DESCRIPTION OF FIGURES

[0024] The invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings, in which: there figure 1 is a schematic sectional view of a turbomachine according to the state of the art, the figure 2 is a detailed sectional view of a turbine of the turbomachine of the figure 1 , there figure 3 is a detailed sectional view of a compressor of the turbomachine of the figure 1 , there figure 4 is an end view of a turbine blade comprising an assembly of angular blade sectors according to the invention, the figure 5 is a perspective view of a blade sector of a blade sector according to the state of the art, the figure 6A is a sectional view of the blade sector of the figure 5 , there figure 6B is a sectional view of a blade sector according to the invention, the figure 7 is a perspective view of an assembly of abradable material blocks of two angular blade sectors, the figure 8 is a sectional view of an assembly with a set of blocks of abradable material of two angular sectors of blading, the figure 9 is a diagram representing the flow rate of a recirculation flow passing through an assembly of angular blade sectors as a function of the clearance between these sectors, the figure 10A is a sectional view of an assembly with a high clearance of abradable material blocks of two angular blade sectors, and of the recirculation gas flow passing through it, the figure 10B is a sectional view of an assembly with a reduced set of abradable material blocks of two angular blade sectors, and of the recirculation gas flow passing through it. DETAILED DESCRIPTION

[0025] In the following description, like reference numerals designate like parts or parts having similar functions.

[0026] By axial direction, we will designate by extension any direction parallel to an axis A of a turbomachine, and by radial direction any direction perpendicular and extending radially with respect to the axial direction.

[0027] We represented at the figure 1 a turbomachine 10 of axis A of the double-flow type. Such a turbomachine 10, here a turbojet 10, comprises in a known manner a fan 12, a low-pressure (LP) compressor 14, a high-pressure (HP) compressor 16, a combustion chamber 18, a high-pressure (HP) turbine 20, a low-pressure (LP) turbine 22 and an exhaust nozzle 24. The rotor of the HP compressor 16 and the rotor of the HP turbine 20 are connected by a high-pressure shaft HP 26 and form with it a high-pressure body. The rotor of the LP compressor 14 and the rotor of the low-pressure turbine LP 22 are connected by a LP shaft 28 and form with it a low-pressure body.

[0028] The high and low pressure bodies are crossed by a primary air flow "P" and the fan 12 produces a secondary air flow "S" which circulates in the turbojet 10, between a casing 11 and an external casing 13 of the turbojet, in a cold flow channel 15. At the outlet of the nozzle 24, the gases from the primary flow "P" are mixed with the secondary flow "S" to produce a propulsive force, the secondary flow "S" here providing the majority of the thrust.

[0029] The BP 14 and HP 16 compressors and the HP 20 and BP 22 turbines each have several compressor or turbine stages respectively. As illustrated for example by figure 2 , the BP 22 turbine comprises several mobile turbine blade wheels 22a, 22b, 22c, 22d, 22e whose blades are carried by associated ferrules 30a, 30b, 30c, 30d, 30e which are assembled to each other by bolts 36.

[0030] The BP 22 turbine also comprises fixed blade rings 32a, 32b, 32c, 32d of a diffuser 32 which are interposed between the mobile blade wheels 22a, 22b, 22c, 22d, 22e of the turbine.

[0031] Each ring of fixed blades 32a, 32b, 32c, 32d of diffuser is formed of an assembly of sectors 34a, 34b, 34c, 34d of ring of fixed blades, assembled around the axis A of the turbomachine over 360° so as to constitute a complete ring of fixed blades 32a, 32b, 32c, 32d around the axis A. figure 4 represents by way of example a diffuser blade 32a consisting of an assembly of ten blade sectors 34a.

[0032] In the same way, as illustrated by the figure 3 , an HP compressor 16 of the turbomachine 10 may comprise a series of wheels 22a, 22b of mobile compressor blades between which are interposed rings 32a of fixed stator blades which are themselves produced in the form of an assembly of angular sectors 34a of fixed blade rings. It will therefore be understood that the invention applies to any assembly of angular sectors 34a of fixed blade rings, whether they are angular sectors of a stator intended for a compressor or angular sectors of a diffuser intended for a turbine.

[0033] As also illustrated by the figure 3 , a crown of fixed blades 32a of the compressor is made up of an assembly of angular sectors 34a of crown of blades. It can be seen that each crown of fixed blades, and in particular the crown of blades 32a, is placed in the primary flow vein P by forming a clearance with the adjacent compressor wheels 22a and 22b, and in particular with shells 30a and 30b of these wheels 22a, 22b. A portion of the pressurized gases of the primary flow P, which circulates from upstream to downstream, tends to insinuate itself between the shells 30a and 30b and the angular sector 34a to recirculate from downstream to upstream according to a recirculation flow rc, represented by the arrows of the figure 3 , which tends to bypass the angular sector 34a.

[0034] The existence of this recirculation flow rc is particularly penalizing. The recirculation flow rc tends to reduce the performance of the turbine, or in the case of a compressor, the performance of said compressor. This is the reason why current designs tend to minimize this recirculation flow rc by equipping the angular sector 34a with sealing means with the shell that it surrounds.

[0035] As illustrated by the figure 4 , each sector 34a extends at a determined angle α around the axis of the crown 32a, which corresponds to the axis A of the turbomachine 10 previously illustrated on the figure 1 .

[0036] By "lower" we mean any positioning close to the axis A in the radial direction, while by "upper" we mean any positioning further from the axis A in the radial direction than the lower positioning. Finally, by "transverse" we mean any plane or surface including the axis A and parallel to a section plane of a sector 34.

[0037] Conventionally, as illustrated by the figure 3 , each sector 34a comprises, with respect to the axis A of the blade 32a, a radially outer platform 38a, a radially inner platform 40a, at least two blades 42a which extend substantially in a radial direction R between said platforms 38a, 40a, a root 43a which extends radially inwards from the inner platform 40a and at least one block 44a of abradable honeycomb material which consequently also extends internally to the inner platform 40a between transverse ends (not shown) of the angular sector 34a.

[0038] A radially inner radial sealing face 46a is configured to cooperate with wipers 48a of a labyrinth seal 50a carried by a rotor of the turbomachine, here the shell 30a.

[0039] This configuration makes it possible to significantly reduce the intensity of the recirculation flow rc circulating between the sector 34a and the shell 30a. However, it has no influence on the recirculation flow between two adjacent sectors 34a.

[0040] Conventionally, as illustrated by the figure 5 , the sealing between adjacent sectors 34a is achieved by means of tabs 35a, 37a which are received in housings 39a, 41a which are arranged opposite each other between the sectors 34a to form a barrier to the recirculation flow rc between the sectors 34a. For example, each sector 34a comprises an upper housing 39a, formed in its outer platform 38a, which receives a tangential tab 35a and a lower housing 41a formed in its foot 43a, which receives a radial tab 37a. This configuration is particularly expensive because it requires precise manufacturing tolerances of the housings 39a, 41a on the one hand, and because it imposes particular assembly precautions, in particular with regard to the sectors which are intended to close the entire blading 32a during its assembly.

[0041] The invention proposes to simplify the sealing between the sectors 34a by taking advantage of the block 44a of abradable material already present radially inside the sector 34a relative to the internal platform 40a so as to ensure a seal directly between transverse end walls 52a of two adjacent angular sectors 34a.

[0042] As illustrated by the figures 7 And 8which represent the assembly of two angular sectors 34a at their blocks 44a made of abradable material, the abradable honeycomb material of each block 44a comprising, in a manner known per se, tubular cells 54a oriented radially in the radial direction R. According to the invention, at the transverse end wall 52a of a block 44a, which is intended to cooperate with the transverse end wall 52a of the other adjacent block 44a, all the cells 54a are open by means of openings 56a1 which are turned towards the side opposite to the sector 44a in which they are formed, and which cooperate with openings 56a2 formed in the wall 52a of the other block 44a of the adjacent sector 34a.

[0043] To ensure optimal reduction of the leakage rate rc under the inner platform 40a of the sector 34, the block of abradable material 44a of the sector 34a, in the preferred embodiment of the invention, extends to the inner platform 40a. This configuration has been shown in figure 6B . Compared to a conventional angular sector 34a like the one shown in the figure 6A , the foot 43a has been removed and the block 44a of honeycomb material has been extended radially to the inner platform 40a so as to give a maximum height to the block 44a of honeycomb material, and in doing so, to give it maximum sealing. Furthermore, this configuration makes it possible to dispense with the installation of a conventional sealing system with tabs arranged between the feet 43a of the adjacent platforms.

[0044] As illustrated by the figures 7 And 8, the openings 56a1, 56a2 of the cells 54a are all arranged in the same associated plane T1, T2 of the wall 52a. The wall 52a can therefore be obtained very simply. In the preferred embodiment of the invention, the honeycomb material of the block 44a is obtained by an additive manufacturing process. This configuration allows the formation of a wall 52a provided with regular cells 54a and a regular conformation of the openings 56a1, 56a2 without risking deterioration during the manufacture of the wall 52a as could be the case using a material removal process.

[0045] Preferably, as illustrated by the figure 8 , the opening 56a1, 56a2 of each cell 54a is of a width corresponding to the total width I of said cell 54a. This configuration makes it possible to prevent the gas flow rc from remaining trapped in a cell and creating micro-turbulences there which would disturb the gas flow.

[0046] The cells 54a may take various cylindrical or polygonal shapes, and may also be different from each other. However, it has been found that the optimal orientation of the openings 56a1, 56a2 is obtained when the cells 54a are identical and polygonal in shape.

[0047] In this configuration, an assembly of two adjacent angular sectors 44a as shown in figures 7 And 8 can advantageously be obtained with cells 54a of the end wall 52 of one of said adjacent angular sectors 34a which are offset in the axial direction A by a determined offset d relative to those of the end wall 52a of the other of said adjacent angular sectors 34a. As illustrated by figures 7 And 10B , this shift d allows to create a series of obstacles to the flow rc which slows down the flow. It is sufficient that the shift d has a non-zero value.

[0048] As illustrated by the figures 7 And 8 , the cells 54a of the adjacent angular sectors 44a are arranged in a staggered pattern, the cells 54a of the end wall 52a of one of the adjacent angular sectors 44a being offset in the axial direction A relative to those of the end wall 52a of the other of the adjacent angular sectors 44a by an offset d equal to half the width I of a cell 54a.

[0049] As can be seen in the figure 8 , the plane T1 of the openings 56a1 of the cells of the end wall 52a of one of the adjacent angular sectors 44a forms a determined clearance J with the plane T2 of the openings 56a2 of the cells 54a of the end wall 52a of the other of the adjacent angular sectors 44. This clearance J conditions the flow rate of the recirculation flow rc passing between the sectors.

[0050] As illustrated by the figure 9 which represents a flow rate D of the flow rc as a function of the value of the clearance J, we see that the flow rate D decreases as the clearance J decreases. From a minimum value Jmin of the clearance J, this flow rate D remains constant, minimal and equal to a minimal flow rate Dmin.

[0051] The clearance J can be zero when the cells 54a are arranged in a staggered pattern, as shown in figures 7 And 10B , because due to the offset of the cells 54a there is no risk of interference of the cells 54a with each other. In this case, the axially offset open cells 54a form baffles which slow down the gas flow rc with maximum efficiency.

[0052] The clearance J can also be negative, the cells 54a then being nested within each other to form baffles.

[0053] There figure 10A illustrates a gas flow rc corresponding to a clearance J of 0.5mm and the figure 10B illustrates an rc gas flow corresponding to zero clearance J. The rc flow rate is considerably reduced at zero clearance, and the flow rate can be reduced by almost 96%.

[0054] As seen in reference to the figure 4, the ring 32a of fixed blades comprises a determined number of sectors 34a of ring of fixed blades whose juxtaposition forms the entire ring and it comprises at least two of these angular sectors 34a of ring of fixed blades comprising blocks 44a of abradable material 44a provided with open cells 54a. It will be understood that obviously, all the sectors of ring of fixed blades preferably comprise blocks 44a provided with open cells 54a. Thus, each angular sector 34a of ring of fixed blades is assembled with each of the angular sectors 34a of ring of fixed blades which are adjacent to it in an assembly of the type described above, and each block 44a comprises at its two ends opposite transverse end walls 52a which are shaped with open cells 54a.

[0055] The invention therefore advantageously makes it possible to ensure sealing between angular sectors 32a of fixed blade rings in a simple and effective manner, and to limit the flow rate of the recirculation flow rc between these angular sectors 32a, which makes it possible to significantly improve the performance of a compressor or a turbine equipped with such angular sectors 32a of fixed blade rings.

Claims

1. An angular sector (34a) of a fixed blading ring (32a) of a turbomachine (10), in particular of a rectifier or distributor, said sector (34a) extending at a given angle (α) around an axis (A) of (32a) and comprising, with respect to the axis (A) of said ring (32a), a radially outer platform (38a) and a radially inner platform (40a), at least two vanes (42a) extending between said platforms (38a, 40a), and at least one abradable honeycomb material block (44a) extending internally of the inner platform (40a) between transverse ends (52a) of the sector (34a) and comprising radially oriented tubular cells (54a), characterized in that the abradable honeycomb material block (44a) comprises at least one transverse end wall (52a) at which all the cells (54a) are open via openings (56a1, 56a2) which face away from said sector (34a).

2. The angular sector (34a) according to the preceding claim, characterized in that the abradable material block (44a) extends radially to the inner platform (40a).

3. The angular sector (34a) according to the preceding claim, characterized in that the openings (56a1, 56a2) of the cells (54a) are all arranged in the same plane (T1, T2) of said wall (52a).

4. The angular sector (34a) according to one of the preceding claims, characterized in that the opening (56a1, 56a2) of each cell (54a) is of a width corresponding to a total width (I) of said cell (54a).

5. The angular sector (34a) according to one of the preceding claims, characterized in that the cells (54a) are identical and polygonal in shape.

6. An assembly of two adjacent angular sectors (34a) according to the preceding claim, characterized in that the transverse end walls (52a) of said adjacent angular sectors (34a) comprise open cells (54a) which face each other and in that the cells (54a) of the end wall (52a) of one of said adjacent angular sectors (34a) are offset by a given offset (d) in the axial direction (A) with respect to those of the end wall (52a) of the other of said adjacent angular sectors (34a).

7. The assembly of two adjacent angular sectors (34a) according to the preceding claim, characterized in that the cells (54a) of the adjacent angular sectors (34a) are arranged in a staggered manner, the cells (54a) of the end wall (52a) of one of the adjacent angular sectors (34a) being offset in the axial direction (A) with respect to those (54a) of the end wall (52a) of the other of the adjacent angular sectors (34a) by a given offset (d) equal to half the width (I) of a cell.

8. The assembly of two adjacent angular sectors (34a) according to one of claims 6 or 7 taken in combination with claim 3, characterized in that the plane (T1) of the openings (56a1, 56a2) of the cells (54a) of the end wall (52) of one of the adjacent angular sectors (34a) forms a given clearance (J) with the plane (T2) of the openings (56a2) of the cells (54a) of the end wall of the other of the adjacent angular sectors.

9. The Assembly of two adjacent angular sectors (34a) according to the preceding claim, characterized in that said given clearance (J) is zero or negative so that the open cells (54a) axially offset form baffles.

10. A turbomachine fixed blading ring (32a) comprising a plurality of angular sectors (34a) of the fixed blading ring, characterised in that it comprises a given number of sectors (34a) whose juxtaposition forms the entire fixed blading ring (32a), in that each angular sector (34a) of the fixed blading ring comprise two opposite transverse end walls (52a) at which all cells (54a) are open, and in that each angular sector (34a) of the fixed blading ring is assembled with each adjacent angular sectors (34a) of the fixed blading ring to form an assembly according to one of claims 6 to 9.

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