Turbine exhaust housing

Abstract

The invention relates to an exhaust casing (15) for a turbine, the turbine extending along a longitudinal axis (X), the exhaust casing comprising: an annular shroud (23) having a wall (24) extending from a first flange (25) along the longitudinal axis (X), a plurality of openings (27) being arranged through the wall (24); a plurality of mouths (28), each of the plurality of mouths forming a passage (29) extending from upstream to downstream between a corresponding inlet (30) and one of the openings (27), each mouth (28) having: a butt flange (31) located at the inlet (30) and having a radially inner edge (32) in contact with the first flange (25) of the annular shroud (23); a mouth wall (34) delimiting the passage (29) and comprising a radially inner wall portion (35), the radially inner wall portion being formed by a thickened section made on the wall (24) of the shroud (23).

Description

Technical Field

[0001] The present invention relates to the field of turbines, and more specifically to a turbine exhaust casing and a method for manufacturing a turbine exhaust casing. Background Art

[0002] Such as Figure 1 The turbomachine 1 shown generally has a housing delimiting one or more flow ducts, through which a gas stream accelerated by moving elements of the turbomachine circulates.

[0003] Typically, the turbine 1 includes a fan 3 , a compressor 4 , a combustion chamber 5 , a turbine 6 , and an exhaust gas 7 along a flow direction of a fluid in the turbine.

[0004] Such as Figure 1 Some turbomachines of the example shown have two compressors and two turbines operating at different pressures and therefore have a low-pressure compressor 41 , a high-pressure compressor 42 , and a high-pressure turbine 61 and a low-pressure turbine 62 located downstream of the combustion chamber 5 .

[0005] Depending on the operating mode of the turbomachine 1 (for example, idle or full throttle), the compressor 4 operates differently. When the turbomachine 1 transitions from idle mode to full throttle mode, a high flow rate of compressed air must be discharged from the compressor 4 to avoid pumping risks. This is also the case during transient flight phases, or during idle phases, or more generally, when the pilot is prompted to manipulate the throttle control.

[0006] Usually, the bleed is made from the air flow located downstream of the high-pressure compressor 42, but this bleed at high temperature, high speed and high expansion rate generates strong noise levels and causes thermal stresses. However, the acoustic limitations of the turbomachine require that the additional noise of the aircraft caused by the bleed of the air flow (the noise belonging to this new flow) and its subsequent reintroduction is less than 1 EPNdB (“Effective Perceived Noise in decibels”, ie the effective noise perceived in decibels).

[0007] In this respect, the solutions proposed by the prior art for discharging the bleed gas stream are unsatisfactory.

[0008] It is known to reintroduce the flow at the injection nozzle section of the turbine. However, this solution degrades the turbine acoustically. Furthermore, the turbine is cumbersome to place in place, since a large additional opening needs to be installed at the injection nozzle section.

[0009] Another known solution is to reintroduce the airflow into the secondary duct of the turbine. However, this means introducing the hot airflow into the cold flow of the secondary duct, and this mixing causes a strong acoustic shock.

[0010] A turbomachine having an exhaust housing is also proposed, which is equipped with a pipe extending from an opening provided in the exhaust housing, the pipe being connected to a line connected to an opening for bleeding the gas flow at the compressor.

[0011] However, such solutions are limited by the manufacturing methods usually used to produce these components, which are usually obtained by assembling multiple parts of untreated cast components and machining the functional surfaces.

[0012] Specifically, casting introduces geometric constraints on the final shape of the component, which can reduce the potential performance of the component.

[0013] In fact, in a turbofan engine, the secondary flow flows concentrically with the flow of the main duct which passes through the compressor and turbine stages of the turbomachine.

[0014] The secondary flow flows around the compressor, turbine and exhaust housings, and elements protruding from the compressor, turbine and exhaust housings create turbulence in the flow of the secondary flow.

[0015] For example, Figure 2 An exhaust housing 7 is shown comprising a mouth 8 connected to a tube 9 configured to convey the air flow to the mouth 8 to reintroduce the air flow into the flow of the main duct at the exhaust housing 7 .

[0016] Also shown is the flow line L of the secondary flow, which has an area I of intersection with the tube 9, which generates disturbances in the flow of the secondary flow.

[0017] Therefore, there is a need to limit these disturbances and thus improve the aerodynamic performance of the exhaust casing. Summary of the invention

[0018] An object of the present invention is to improve the aerodynamic performance of prior art solutions.

[0019] Another object is to improve the production methods for prior art solutions.

[0020] To this end, an exhaust housing for a turbine is provided, the turbine extending along a longitudinal axis, the exhaust housing comprising:

[0021] - an annular cover portion having a wall extending axially from the first flange along the longitudinal axis, a plurality of openings being provided through the wall;

[0022] - a plurality of nozzles, each nozzle of the plurality of nozzles forming a passage extending between a respective inlet and one of the openings, each nozzle having:

[0023] - a butt flange located at the inlet and having a radially inner edge in contact with the first flange of the annular hood portion,

[0024] - A mouth wall comprising a radially inner wall portion formed by a thickened section made on the wall of the cage.

[0025] Such an exhaust casing can be radially closer to the abutment flanges of the walls of the mouth and the hood, increasing the compactness of the exhaust casing and improving the aerodynamic performance of the exhaust casing.

[0026] Advantageously, the invention is complemented by the following features, taken alone or in combination:

[0027] at least one of the plurality of nozzles also has a plurality of fins located in the channel; this makes it possible to orient the bleed flow when it is reintroduced into the flow duct through the opening, which makes it possible to limit the collision between the flow and the bleed flow and therefore the aerodynamic disturbances caused by the injection of the bleed flow; moreover, this makes it possible to limit the flow entering the opening, which limits the risk of flow separation in the flow duct;

[0028] - the thickened section has at least one cavity; this makes it possible to limit the mass of the exhaust gas housing and, when producing the thickened section by additive manufacturing, to limit the manufacturing time;

[0029] the first flange of the exhaust gas casing is formed with a thickened section and has a plurality of holes, each of the plurality of holes being shaped so that a shank of a mounting screw passes between the first flange and a flange of the low-pressure turbine casing, and at least one hole opens into a cavity shaped so as to receive an end of the shank of the mounting screw;

[0030] - The thickened sections are formed with a honeycomb structure; this structural formation offers a good compromise between mass and mechanical properties.

[0031] According to another aspect, the invention proposes a method for producing an exhaust gas housing according to the invention, wherein the mouth is produced by an additive manufacturing method. This enables the production of geometries that cannot be realized in other ways and limits the amount of material used.

[0032] According to another aspect, the present invention provides a pressure regulating unit for a turbine, the pressure regulating unit comprising:

[0033] - an exhaust housing according to the invention,

[0034] a bleed module configured to bleed the pressurized gas flow upstream of the exhaust casing, the bleed module comprising an inlet pipe and a valve capable of closing or not closing the inlet pipe,

[0035] - a distribution module configured to distribute the discharged flow to the mouths of the exhaust housing, the distribution module comprising a distribution pipe and a plurality of injection pipes, the inlet pipe opening into the distribution pipe, each of the plurality of injection pipes being connected to the distribution pipe and respectively to one of the plurality of mouths.

[0036] According to a further aspect, the invention provides a turbine comprising an exhaust gas housing according to the invention.

[0037] According to another aspect, the invention provides an aircraft comprising a turbomachine according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other characteristics and advantages of the invention will emerge from the following description, which is given purely by way of illustration and not as a limitation and should be read with reference to the accompanying drawings, in which:

[0039] - Figure 1 is a schematic illustration of a turbine according to the prior art;

[0040] - Figure 2 is a detailed schematic illustration of a cross section of a mouth of an exhaust housing according to the prior art;

[0041] - Figure 3 is a diagrammatic representation of a pressure regulating unit according to the present invention;

[0042] - Figure 4 is a detailed schematic illustration of a cross section of the mouth of an exhaust housing according to the invention. DETAILED DESCRIPTION

[0043] refer to Figure 3 , along the flow direction of the flow F in the flow duct 11 of the turbine 10 , the turbine 10 generally includes a high-pressure compressor 12 , a high-pressure turbine 13 and a low-pressure turbine 14 .

[0044] In this description, the concepts upstream and downstream refer to the flow direction of the flow in the components of the turbomachine 10. The concepts axial and radial refer to a cylindrical geometry having an axis X along which the turbomachine extends.

[0045] The turbomachine 10 further comprises an exhaust casing 15 arranged at the outlet of the low-pressure turbine 14 , upstream of an exhaust nozzle (not shown).

[0046] The turbomachine 10 further has a pressure regulating unit 16 configured to bleed a pressurized gas flow that can be generated, for example, at the high-pressure compressor 12 and to reinject the pressurized gas flow at the exhaust casing 15. In other words, the pressure regulating unit 16 creates a fluid connection parallel to the flow duct 11 and is configured to reinject the bleed flow at the exhaust casing 15. Advantageously, the bleed flow is reinjected into the flow duct 11 at a Mach number less than or equal to 0.5, which can limit the acoustic impact.

[0047] In the embodiment shown, the pressure regulating unit 16 comprises:

[0048] a discharge module 17 configured to discharge the gas flow in the flow duct 11 (preferably the gas flow downstream of the high-pressure compressor 12), the discharge module 17 comprising an inlet pipe 18 and a valve 19 capable of closing or not closing the inlet pipe 18,

[0049] A distribution module 20 , configured to distribute the bleed flow to the exhaust housing 15 , comprises a distribution pipe 21 into which the inlet pipe 18 opens and a plurality of injection pipes 22 , each of which is connected to the distribution pipe 21 .

[0050] The valve 19 makes it possible to control the flow rate of the bleed air flow taken through the inlet pipe 18. The opening and closing of the valve 19 is usually controlled by a computer of the aircraft, for example according to the flight commands of the pilot.

[0051] like Figure 3 and Figure 4 As shown, the exhaust housing 15 has a substantially rotationally symmetrical geometry and comprises:

[0052] an annular cover portion 23 having a wall 24 extending from upstream to downstream between a first flange 25 and a second flange 26 and defining the flow duct 11 radially to the outside, through which a plurality of openings 27 are provided; and

[0053] a plurality of mouths 28 , each of which forms a passage 29 extending from upstream to downstream between the inlet 30 and the respective opening 27 , the mouths 28 being configured to convey the vented flow from the inlet 30 to the opening 27 .

[0054] The injection pipe 22 is therefore connected to the mouth 28 so as to enable the delivery of the bleed air flow taken at the high-pressure compressor 12 to reinject the bleed air flow at the exhaust casing 15 .

[0055] Advantageously, the plurality of mouths 28 are distributed on a circle around the exhaust casing 15 , which makes it possible to distribute the flow reintroduced into the flow duct 11 and thus limit the disturbances caused by reintroducing the bleed flow into the flow duct 11 .

[0056] Advantageously, the mouths 28 are distributed in groups which are themselves distributed around the exhaust housing 15 , which simplifies the construction and installation of the distribution module 20 , since it is not necessary to distribute the flow over the entire circumference of the exhaust housing 15 .

[0057] according to Figure 3 In the illustrated embodiment, the inlet pipe 18 opens into a distribution pipe 20 which is divided into two substantially symmetrical sections which are arranged on both sides of the exhaust housing 15 .

[0058] In this example, each section of the distribution pipe 20 has three injection pipes 22 , each of which is connected to a mouth 28 of the exhaust housing 15 .

[0059] Thus, in this example, the exhaust housing 15 comprises six symmetrically distributed holes: three holes on one side and three holes on the other side. This makes it possible to limit thermomechanical deformations of the exhaust housing.

[0060] Since the openings 27 are not in communication with each other, this can further improve the acoustics of the flow at the outlet of the injection tube 22 , since the gas flows at the outlet of the injection tube 22 do not mix.

[0061] Each mouth portion 28 has a butt flange 31 at the inlet 30, the butt flange 31 having a radial inner end 32 and a radial outer end 33, the radial inner end 32 of the butt flange 31 being in contact with the first flange 25 of the annular cover portion 23. This makes it possible to avoid the flow between the first flange 25 and the butt flange 31 (which flow may be disturbed by obstacles and may cause turbulence), thereby improving the aerodynamic performance of the exhaust casing 15.

[0062] Each mouth 28 has a mouth wall 34 which delimits the passage 29 and comprises a radially inner wall portion 35 and a radially outer wall portion 36, the radially inner wall portion 35 of the mouth being formed by a thickened section made on the wall 24 of the cover 23. This makes it possible to position the mouth 28 as close as possible radially to the wall 24 of the cover 23, which improves the compactness of the exhaust casing 15 and the aerodynamic performance of the exhaust casing 15.

[0063] In practice, this enables the injection pipe 22 to be brought radially closer to the exhaust casing 15, thus making it possible to limit the intersections between the injection pipe 22, the mouth 28 and the flow line L of the secondary flow that flows concentrically with the flow F around the high-pressure compressor 12, the high-pressure turbine 13, the low-pressure turbine 14 and the exhaust casing 15. This thus makes it possible to limit the disturbances in the secondary flow, which limits the noise and improves the aerodynamic performance of the turbine.

[0064] The presence of the opening 27 in the non-discharge configuration in the flow duct 11 is similar to the presence of an interruption, or to the presence of a wall at the exhaust housing 15 that partially blocks the flow in the flow duct 11 .

[0065] A local obstruction of the flow in the pressure regulating unit 16 results in a dissipation of the energy of the flow, which manifests itself in increased losses and reduced aerodynamic performance.

[0066] To improve the acoustics, the mouth 28 has at its end an inclination with a slope less than or equal to 45°, preferably less than 35°, relative to the longitudinal axis X of the turbine.

[0067] This avoids abrupt changes between the direction of the flow duct 11 and the direction of the passage 29 of the mouth 28. Such a change would have the effect of causing a large-scale separation of the boundary layer and thus an increase in noise.

[0068] Advantageously, at least one of the nozzles 28 has a plurality of fins 37 arranged in the passage 29 and close to the opening 27, the fins 37 being configured to redirect the flow to limit the effect of the flow reintroduced into the flow duct 11. This can reduce the disturbance of the flow F passing through the flow duct 11 caused by the bleed flow being reintroduced into the flow duct 11. Furthermore, when the pressure regulating unit 16 does not distribute the flow, the fins 37 limit the tendency of the flow F to enter the opening 27 and thus limit the aerodynamic losses in the flow duct.

[0069] Advantageously, the thickened section of the radially inner wall portion 35 forming the mouth 28 may have one or more cavities 38 or voids, which may limit the mass of the exhaust casing 15 .

[0070] Optionally, the first flange 25 of the exhaust casing 15 is formed in a thickened section and has a plurality of holes 39, each hole being shaped so that a shank of a mounting screw 40 passes between the first flange 25 and the flange of the low-pressure turbine casing 14. Advantageously, each hole 39 opens into a cavity 38 shaped so as to receive one end of the shank of the mounting screw 40.

[0071] Preferably, the hole 39 is threaded to cooperate with the thread of the shank of the assembly screw 40, and the end of the shank is located in the cavity 38. This makes it unnecessary to have an assembly nut, thereby limiting the number and mass of components of the unit, which simplifies the assembly operation.

[0072] Advantageously, the thickened section is formed with a honeycomb structure which has good mechanical properties while greatly limiting the amount of material required to form a given volume.

[0073] Such an exhaust housing 15 can be manufactured by a method comprising a step of assembling cast elements, which is a known method and can further comprise an additive manufacturing step. The assembly can be achieved, for example, by welding or brazing.

[0074] In one embodiment, the nozzle 28 is produced by an additive manufacturing method or a 3D printing method. This type of method can produce complex shapes while limiting material costs. In addition, this can greatly facilitate the production of the fins 37 of the nozzle 28.

[0075] This also makes it possible to produce a porous material to form the thickened section which forms the radially inner wall portion 35 of the mouth 28. This makes it possible to limit the mass of the exhaust casing, limit the material costs and also significantly reduce the manufacturing time of the thickened section, while maintaining the mechanical properties required for the mechanical strength of the exhaust casing (as dictated by the exhaust casing specification).

[0076] The mouth 28 may be manufactured separately and then attached and fixed to the cover 23 by welding or brazing, or alternatively may be manufactured directly on the cover 23 or a part of the cover intended to be assembled to other cover parts to form the annular cover 23 .

Claims

1. An exhaust housing (15) for a turbine, the turbine extending along a longitudinal axis (X), the exhaust housing comprising: - an annular cover portion (23) having a wall (24) extending axially from a first flange (25) along said longitudinal axis (X), a plurality of openings (27) being provided through said wall (24); - a plurality of nozzles (28), each of the plurality of nozzles forming a passage (29) extending between a respective inlet (30) and one of the openings (27), each nozzle (28) having: - a butt flange (31) located at the inlet (30) and having a radially inner edge (32) in contact with the first flange (25) of the annular cover portion (23), - a mouth wall (34) comprising a radially inner wall portion (35) formed by a thickened section made on the wall (24) of the annular mantle portion (23).

2. The exhaust housing (15) according to claim 1, wherein: At least one of the plurality of nozzles (28) also has a plurality of fins (37) located in the passage (29).

3. The exhaust housing (15) according to claim 1 or 2, wherein: The thickened section has at least one cavity (38).

4. The exhaust housing (15) according to claim 3, wherein: The first flange (25) of the exhaust casing (15) is formed with the thickened section and has a plurality of holes (39), each of the plurality of holes being shaped so that a rod of a mounting screw (40) passes between the first flange (25) and a flange of the low-pressure turbine casing (14), and at least one hole (39) leads to a cavity (38) shaped so as to receive an end of the rod of the mounting screw (40).

5. The exhaust housing (15) according to claim 1 or 2, wherein: The thickened section is formed with a honeycomb structure.

6. A method for producing an exhaust housing (15) according to claim 1 or 2, wherein: The mouth (28) is produced by an additive manufacturing method.

7. A pressure regulating unit (16) for a turbine, comprising: - an exhaust housing (15) according to claim 1 or 2, a discharge module (17) configured to discharge the pressurized gas flow upstream of the exhaust housing (15), the discharge module comprising an inlet pipe (18) and a valve (19) capable of closing or not closing the inlet pipe (18), - a distribution module (20), which is configured to distribute the discharged flow to the mouth (28) of the exhaust housing (15), and comprises a distribution pipe (21) and a plurality of injection pipes (22), the inlet pipe (18) leading to the distribution pipe, each of the plurality of injection pipes being connected to the distribution pipe (21) and respectively connected to one of the plurality of mouths (28).

8. A turbomachine comprising an exhaust casing (15) according to claim 1 or 2.

9. An aircraft comprising a turbine according to claim 8.

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