The invention relates to an angular sector of a turbomachine blading, in particular an blading angular sector of a rectifier equipping a compressor or a distributor equipping a turbine of this turbomachine.
Gas turbine engines have, in a known manner, fixed internal blading rings, which are mounted in external casings of a primary flow duct of the engine and which are axially interposed between compressor moving blading wheels or between turbine moving blading wheels of these engines. Each fixed blading ring is dynamically sealed around a compressor or turbine rotor. For this purpose, each fixed blading ring comprises an internal block of abradable material which is designed to cooperate with lip sealing elements that are rotationally integral with the associated compressor or turbine rotor to ensure gas-tightness.
Part of the gas is nevertheless likely to enter between the stationary and moving blading of the compressor or turbine rotors, in the opposite direction to the main flow circulating in the primary flow duct.
The fixed internal blading ring constitute rectifiers when they are interposed between compressor wheels, or constitute distributors when they are interposed between turbine wheels.
In order to facilitate their assembly and reduce their manufacturing cost, the fixed blading rings are often made as an assembly of angular sectors that are juxtaposed next to each other to form a whole fixed blading ring. These rings thus leave an inter-sector clearance which leaves recirculation passages for the gases, no longer around the roots of the angular sectors, but between them.
Indeed, conventionally, part of the gases that pass through the fixed blading from upstream to downstream tend to recirculate from downstream to upstream through the seal that is made between the block of abradable material and the lip sealing element according to a leakage flow rate that one tries to keep as minimal as possible, because it affects the performance of the corresponding compressor or turbine. Another part of the gas that passes through these blading from upstream to downstream tends to recirculate from downstream to upstream by insinuating itself between the sectors through the clearance between the sectors, also called the inter-sector clearance.
The difficulty in ensuring a satisfactory level of sealing lies in the fact that the angular sectors of the ring move due to the mechanical and thermal deformations that occur during engine operation. Thus, the inter-sector clearance and leakage flow rate vary during engine operation. Furthermore, the clearance during hot engine operation must never be zero because contact between the sector platforms could cause ovalization of the casing, which is outside the fixed blading, and/or matting of the surfaces in contact, which could drastically increase the stresses exerted on the fixed blading, resulting in particular in a transfer of these stresses to the outer casing of the engine, which receives the fixed blading.
A transfer of these stresses could cause an ovalization of the outer casing and significantly modify the radial clearances between this casing and the adjacent moving blading, with a very negative impact on the engine in terms of service life.
Conventional sealing between two immediately adjacent angular sectors of a fixed blading ring is ensured by lip seal systems interposed between these sectors to limit leakage between sectors. These sealing systems can be used to seal ring sectors of the fixed blading in the primary flow duct, and also, in the case of a double-flow engine, to seal ring sectors of a fixed blading in the secondary flow duct.
In this technology, lips are housed between two adjacent sectors in housings that have been machined into the sectors. The lips are used to prevent the flow of gas of passing through the inter-sector clearance.
Conventionally, an angular sector of the blading ring comprises, with respect to the axis of the ring, a radially outer platform substantially in the shape of an angular section of a cylinder, a radially inner platform in the shape of an angular section of a cylinder, at least two vanes extending between said platforms, a root attached to the inner platform, and at least one block of abradable honeycomb material extending inwardly to the root, as described in FR-2.552.159-A1 and JP-2008/180149-A. The lips interposed between two sectors are embedded in the mass of the two adjacent roots of the two sectors and in housings facing the adjacent interior and exterior 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.
However, these lips are not easy to install. In addition, they require the construction of housings in the angular sectors of the fixed blading ring, which are expensive to manufacture.
In addition, the lips cannot be arranged along the entire radial thickness of the root for the sealing on the inside of the inner platform. Consequently, clearances remain between the sectors through which the gases can flow.
Therefore, there is a need for an alternative sealing technology to dispense with such lips and to improve the sealing between the ring sectors of a fixed blading.
For this purpose, the invention proposes to take advantage of the block of abradable material arranged inside the inner platform to provide a seal directly between transverse end walls of two adjacent angular sectors of a fixed blading ring.
For this purpose, the invention provides an angular sector of a fixed blading ring of a turbomachine, in particular of a rectifier or distributor, said sector extending at a given angle around an axis A of the fixed blading ring and comprising, with respect to the axis A of said fixed blading ring, a radially outer platform, a radially inner platform, at least two vanes extending between said platforms, and at least one abradable honeycomb material block extending internally of the inner platform between transverse ends of the sector and comprising radially oriented tubular cells, characterized in that the abradable honeycomb material block comprises at least one transverse end wall at which all the cells are open via openings which face away from said sector.
According to other characteristics of the angular sector:
the abradable material block extends radially until 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 polygonal in shape.
The invention also concerns 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 face each other and in that the cells of the end wall of one of said adjacent angular sectors are offset by a given offset in the axial direction with respect to those of the end wall of the other of said adjacent angular sectors.
According to other characteristics of the assembly:
the cells of the adjacent angular sectors are arranged in a staggered manner, the cells of the end wall of one of the adjacent angular sectors being offset in the axial direction with respect to those of the end wall of the other of the adjacent angular sectors by a given offset equal to half the width of a cell,
the plane of the openings of the cells in the end wall of one of the adjacent angular sectors forms a given clearance with the plane of the openings of the cells in the end wall of the other of the adjacent angular sectors,
the given clearance is zero or negative so that the open cells axially offset form baffles.
Finally, the invention concerns a fixed blading ring of a turbomachine comprising a plurality of angular sectors of the fixed blading ring, characterized in that it comprises a given number of sectors whose juxtaposition forms the entire fixed blading rings, in that each angular sector of the fixed blading ring comprises two opposite transverse end walls at which all cells are open and in that each angular sector of the fixed blading ring is assembled with each adjacent angular sector of the fixed blading ring to form an assembly of the type described above.
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:
In the following description, identical reference numbers refer to parts that are identical or have similar functions.
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.
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 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.
The LP and HP compressors 14, 16, and the HP and LP turbines 20, 22 each have several compressor or turbine stages respectively. As shown for example in
The LP turbine 22 also comprises fixed blading rings 32a, 32b, 32c, 32d of a blading of a diffuser 32 which are interposed between the turbine moving blading wheels 22a, 22b, 22c, 22d, 22e.
Each fixed blading ring 32a, 32b, 32c, 32d of a diffuser is formed of an assembly of sectors 34a, 34b, 34c, 34d of fixed blading rings, assembled around the axis A of the turbomachine on 360° so as to constitute a fixed blading ring 32a, 32b, 32c, 32d complete around the axis A.
In the same way, as illustrated in
As shown also in
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 why current designs tend to minimize this recirculation flow rc by equipping the angular sector 34a with sealing means with the shroud it surrounds.
As shown in
Any position close to the axis A in the radial direction is referred to as “lower” and any position further from the axis A in the radial direction than the lower position is referred to as “upper”. Finally, by “transverse” is meant any plane or surface comprising the axis A and parallel to a sectional plane of a sector 34.
Conventionally, as shown in
A radially inner radial sealing face 46a is configured to cooperate with sealing elements 48a of a labyrinth seal 50a carried by a rotor of the turbomachine, here the shroud 30a.
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.
Conventionally, as shown in
The invention proposes to simplify the sealing between the sectors 34a by taking advantage of the abradable material block 44a already present radially inside the sector 34a with respect to the inner platform 40a so as to provide a seal directly between transverse end walls 52a of two adjacent angular sectors 34a.
As illustrated in
To ensure optimum reduction of the leakage flow rate rc under the inner platform 40a of the sector 34, the abradable material block 44a of the sector 34a, in the preferred embodiment of the invention, extends to the inner platform 40a. This configuration has been shown in
As shown in
Preferably, as shown in
The cells 54a can be cylindrical or polygonal in shape and can 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.
In this configuration, an assembly of two adjacent angular sectors 44a as shown in
As shown in
As can be seen in
As shown in
The clearance J can be zero as soon as the cells 54a are staggered, as shown in
The clearance J can also be negative, in which case the cells 54a are nested within each other to form baffles.
As seen in reference to
The invention thus allows advantageously 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 32a of a fixed blading ring in a consequent manner.
Number | Date | Country | Kind |
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1854335 | May 2018 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2019/051138 | 5/20/2019 | WO | 00 |