Angular sector for turbomachine blading with improved sealing

Abstract

An angular sector of a fixed blade ring of a turbomachine, in particular a stator or a guide vane assembly, includes, relative to the axis of said fixed blade ring, 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 extending on the inside of the inner platform between transverse ends of the sector. The block of abradable material includes at least one transverse end wall shaped according to a toothed profile having at least one radially oriented tooth extending across an entire radial thickness of said block.

Claims

1. A fixed blading ring of a turbomachine made of multiple angular sectors, each angular sector extending at a given angle around an axis A of the fixed blading ring and comprising, relative to the axis A, a radially outer platform, a radially inner platform, at least two vanes extending between said radially outer and radially inner platforms, and one honeycomb structure extending between transverse ends of each sector, said honeycomb structure comprising at least one abradable honeycomb material block extending on an inside of the radially inner platform between the transverse ends of said angular sector, wherein the abradable honeycomb material block comprises at least one transverse end wall shaped according to a toothed profile comprising at least one tooth with a radial direction, said at least one tooth extending along an entire radial thickness of said abradable honeycomb material block.

2. The fixed blading ring according to claim 1, wherein the abradable honeycomb material block extends to the radially inner platform.

3. The fixed blading ring according to claim 1, wherein the at least one tooth projects transversely from said abradable honeycomb material block and is made of an abradable honeycomb material of said abradable honeycomb material block.

4. The fixed blading ring according to claim 1, wherein the toothed profile has a sawtooth cross-sectional shape in a plane perpendicular to the radial direction.

5. The fixed blading ring according to claim 1, wherein the toothed profile has a crenellated cross-sectional shape in a plane perpendicular to the radial direction.

6. The fixed blading ring according to claim 1, wherein the toothed profile has a single tooth in the form of a pin.

7. The fixed blading ring according to claim 6, wherein the single tooth extends from an axial end wall of the abradable honeycomb material block.

8. The fixed blading ring according to claim 1, wherein an abradable honeycomb material of the abradable honeycomb material block comprises radially oriented tubular cells.

9. The fixed blading ring according to claim 1, wherein said at least one transverse end walls of two adjacent angular sectors face each other, and wherein said toothed profiles of said two adjacent angular sectors are complementary.

10. The fixed blading ring of claim 9, wherein each angular sector comprises two opposite transverse end walls which are shaped into toothed profiles, each toothed profile comprising at least one radially oriented tooth, and wherein each angular sector is assembled with each of the angular sectors adjacent thereto.

Description

DESCRIPTION OF THE FIGURES

(1) The invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly when reading the following description made as an example, which is not limitative, and with reference to the appended drawings, in which:

(2) FIG. 1 is a schematic sectional view of a turbomachine according to the prior art,

(3) FIG. 2 is a detailed cross-sectional view of a turbine of the turbomachine of FIG. 1,

(4) FIG. 3 is a detailed cross-sectional view of a compressor of the turbomachine in FIG. 1,

(5) FIG. 4 is a perspective view of an assembly of angular blading sectors according to the invention,

(6) FIG. 5A is a sectional view of a blading ring sector according to the prior art,

(7) FIG. 5B is a sectional view of a blading ring sector according to the invention,

(8) FIG. 6 is a schematic cross-sectional view of a first tooth profile of an abradable material block of a blading ring sector according to the invention,

(9) FIG. 7 is a schematic sectional view of a second tooth profile of an abradable material block of a blading ring sector according to the invention,

(10) FIG. 8 is a schematic cross-sectional view of a third tooth profile of an abradable material block of a blading ring sector according to the invention,

(11) FIG. 9 is a schematic cross-sectional view of a fourth tooth profile of an abradable material block of a blading ring sector according to the invention.

DETAILED DESCRIPTION

(12) In the following description, identical reference numbers refer to parts that are identical or have similar functions.

(13) Axial direction means by extension any direction parallel to an axis A of a turbomachine, and radial direction means any direction perpendicular and extending radially with respect to the axial direction.

(14) FIG. 1 shows a turbomachine 10 of axis A of the double flow type. Such a turbomachine 10, here a turbojet engine 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 HP high pressure shaft 26 and form a high pressure body with it. The rotor of the LP compressor 14 and the rotor of the LP low pressure turbine 22 are connected by a LP shaft 28 and form with it a low pressure body.

(15) A primary air flow “P” passes through the high- and low-pressure bodies and fan 12 produces a secondary air flow “S” that circulates in the turbojet engine 10, between a casing 11 and an outer casing 13 of the turbojet engine, 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 propulsion force, the secondary flow “S” providing most of the thrust here.

(16) The LP and HP compressors 14, 16 and the HP and LP turbines 20, 22 each comprise several compressor or turbine stages respectively. As shown for example in FIG. 2, the LP turbine 22 comprises several turbine moving blading wheels 22a, 22b, 22c, 22d, 22e whose bladings are carried by associated shrouds 30a, 30b, 30c, 30d, 30e which are assembled together by bolts 36.

(17) The LP turbine 22 also comprises rings of fixed bladings 32a, 32b, 32c, 32d of a diffuser 32 which are interposed between the turbine moving blading wheels 22a, 22b, 22c, 22d, 22e.

(18) Each fixed blading ring 32a, 32b, 32c, 32d of the diffuser is formed by an assembly of sectors 34a, 34b, 34c, 34d of a fixed blading ring, assembled around the axis A of the turbomachine over 360° so as to constitute a complete fixed blading ring 32a, 32b, 32c, 32d around the axis A of the turbomachine.

(19) In the same way, as illustrated in FIGS. 3 to 5B, the HP compressor 16 of the turbomachine 10 can comprise a series of compressor moving blading wheels 22a, 22b between which are interposed rings 32a of the fixed bladings of a rectifier which are themselves made in the form of an assembly of angular sectors 34a of fixed blading rings. It will therefore be understood that the invention applies to any assembly of angular sectors 34a of the fixed blading rings 32a, whether it is an assembly of angular sectors 34a of a rectifier for a compressor or angular sectors 34a of a diffuser for a turbine.

(20) As illustrated in more detail in FIG. 3, a compressor fixed blading ring 32a consists of an assembly of angular sectors 34a of the blading ring. It can be seen that each fixed blading ring, and in particular ring 32a, is placed in the primary flow duct P forming a clearance with the adjacent compressor impellers 22a and 22b, and in particular with shrouds 30a and 30b of these impellers 22a, 22b. Part of the pressurized gases of the primary flow P, which flows from upstream to downstream, tends to insinuate itself between the shrouds 30a and 30b and the angular sector 34a to recirculate from downstream to upstream according to a recirculation flow rc, represented by the arrows in FIG. 3, which tends to bypass the angular sector 34a.

(21) The existence of this recirculation flow rc is particularly penalizing. The recirculation flow rc tends to reduce the performance of the compressor, or similarly in the case of a turbine, the performance of the said turbine. This is why current designs tend to minimize this recirculation flow rc by equipping the angular sector 34a with sealing means with the shroud it surrounds.

(22) As shown in FIG. 3, each sector 34a extends at a given angle around the axis of the ring 32a, which corresponds to the axis A of the turbomachine previously illustrated in FIG. 1.

(23) The term “lower” refers to any position close to the axis A in the radial direction, while the term “upper” refers to any position further from the axis A in the radial direction than the lower position. Finally, by “transverse” is meant any plane or surface comprising the axis A and parallel to a sectional plane of a sector 34.

(24) Conventionally, each sector 34a comprises, with respect to the axis A of the ring 32a, a radially outer platform 38a, a radially inner platform 40a, at least two vanes 42a which extend between said platforms 38a, 40a, a root 43a which extends radially inward from the inner platform 40a and at least one block 44a of abradable honeycomb material which therefore also extends inward to the inner platform 40a between transverse ends (not shown) of the angular sector 34a.

(25) A radially inner radial sealing face 46a is configured to cooperate with lips 48a of a labyrinth seal 50a carried by a rotor of the turbomachine, here the shroud 30a.

(26) This configuration significantly reduces the intensity of the recirculation flow rc circulating between the sector 34a and the shroud 30a. However, it has no influence on the recirculation flow between two adjacent sectors 34a.

(27) Conventionally, the sealing between adjacent sectors 34a is achieved by means of lips (not shown) that are received in housings facing the adjacent sectors 34a and that are arranged between these sectors 34a to form a barrier to the recirculation flow rc between the sectors 34a. This configuration is particularly costly because it requires the creation of housings for the lips, especially in the roots 43a, and because it imposes particular assembly precautions, especially with regard to the sectors that are intended to close the entire blading during its assembly.

(28) As illustrated in FIG. 4, 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 inner platform 40a so as to ensure a sealing directly between transverse end walls of two adjacent angular sectors.

(29) For this purpose, as illustrated in FIG. 4, the invention proposes an angular sector 34a of a turbomachine fixed blading ring of the type described above, characterized in that the block 44a of abradable material comprises at least one transverse end wall 52a which is shaped according to a toothed profile 54a1, 54a2 comprising at least one tooth 56a1, 56a2 with a radial direction R, said at least one radial tooth 56a1, 56a2 extending along an entire radial thickness of said block 44a.

(30) Thus, FIG. 4 shows an assembly of two angular sectors 34a of a fixed blading ring. Each of these two angular sectors 34a of the fixed blading ring comprises a transverse end wall 52a which faces the transverse end wall 52a of the other sector 34a of the fixed blading ring.

(31) As shown in particular in FIG. 6, the block 44a of one of the sectors 34a comprise a tooth profile 54a1 comprising at least one tooth 56a1 and the block 44a of the other of the sectors 34a comprises a tooth profile 54a2, complementary to the tooth profile 54a1, with at least one tooth 56a1. Sealing is thus ensured in the opposite direction to the primary flow P by the cooperation of the transverse end walls 52a and their complementary tooth profiles 54a1 and 54a2.

(32) The fixed blading ring 32a comprises a specific number of ring sectors 34a, the juxtaposition of which forms the entire fixed blading ring 32a and it comprises at least two of these angular sectors 34a of the blading ring comprising complementary tooth profiles 54a1, 54a2. It is to be understood that all ring sectors 34a preferably comprise toothed profiles. Thus, each angular sector 34a is assembled with each of the adjacent angular sectors 34a in an assembly of the type described above, and each block 44a comprises at both ends opposite transverse end walls 52a which are shaped according to toothed profiles 54a1, 54a2 intended to cooperate with the toothed profiles 54a1, 54a2 with radially oriented teeth of the adjacent blocks 44a.

(33) In the preferred embodiment of the invention, the abradable material block 44a of the sector 34a extends to the inner platform 40a. This configuration has been shown in FIG. 5B. Compared to a conventional angular sector 34a as shown in FIG. 5A, the root 43a has been removed and the block 44a of honeycomb material has been extended radially to the inner platform 40a so as to impart maximum height to the block 44a of honeycomb material, thereby providing maximum sealing. Furthermore, this configuration eliminates the need for a conventional lip and groove sealing system on the root 43a.

(34) Preferably, as shown in FIG. 4, each inner platform 40a has an end edge 58a which is shaped into a toothed profile 60a1, 60a2 which is superimposed on the toothed profile 54a1, 54a2 of the corresponding honeycomb material block 44a. Thus the toothed profiles 60a1, 60a2 are also complementary to each other. However, this configuration is not limiting the invention, and the end edges 58a of the inner platforms 40a could be straight.

(35) Each tooth 56a1 or 56a2 of each block 44a can be made in different ways. For example, teeth 56a1 or 56a2 could be attached to block 44a, provided they protrude from the block 44a. However, each tooth 56a1 or 56a2 is preferably made directly from the abradable honeycomb material of the block 44a.

(36) The tooth profile 54a1, 54a2 of the honeycomb material block 44a can be configured in different ways, depending on the desired seal. The higher the number of teeth 56a1 or 56a2, the better the profile 54a1, 54a2 is able to provide a labyrinth that effectively reduces the flow rate of the recirculating flow rc between adjacent angular sectors 44a. On the other hand, the higher the number of teeth 56a1 or 56a2, the more the fitting tolerances of two adjacent angular sectors 44a are reduced and the more complex these adjacent sectors 44a are to achieve. It will therefore be understood that the number of teeth 56a1 or 56a2 will be the result of a compromise between the efficiency of the reduction of the recirculating flow rc and the cost of obtaining the ring 32a formed of the angular sectors 34a, this cost including the realization of these sectors 34a and their assembly.

(37) In this configuration, as shown in FIGS. 6 and 7, the tooth profile 54a1, 54a2 can present, in section in a plane perpendicular to a radial direction R, a crenellated shape, i.e. with teeth of substantially rectangular or square section.

(38) Alternatively, as shown in FIG. 8, the toothed profile 54a1, 54a2 can have a sawtooth shape in cross-section in a plane perpendicular to the radial direction R.

(39) Alternatively, as shown in FIG. 9, the tooth profile 54a1, 54a2 of each sector 44a may comprise a pin which forms the single tooth 56a1, 56a2. In this case, the single tooth 56a1, 56a2 shaped as a pin extends from one of the axial ends 62a1 or 62a2 of the block 44a.

(40) Although this configuration is not limiting the invention, it will be understood that the abradable honeycomb material of the block 44a comprises tubular cells (not shown) that are radially oriented in the radial direction R. This configuration provides maximum strength to the block 44a of material.

(41) In the preferred embodiment of the invention, the honeycomb material of the block 44a is obtained by an additive manufacturing process. This configuration allows for the formation of regular cells and a regular conformation of the tooth profiles 54a1, 54a2 without any risk of deterioration as might be caused by a material removal process.

(42) The invention thus makes it possible to ensure the sealing between angular sectors 32a of the fixed blading ring in a simple and effective manner, and to limit the flow rate of the recirculation flow rc between these angular sectors 32a, which allows to improve the performance of a compressor or a turbine equipped with such angular sectors of the blading ring 32a in a consequent manner.