Turbomachine turbine distributor

Abstract

The present invention relates to a turbomachine turbine distributor, comprising an annular outer casing (18) arranged around an axial direction, the outer casing (18) being intended to be cooled by an air jet by means of a cooling system, the distributor comprising at least one aerodynamically profiled blade (17), at least one lower platform and at least one upper platform (23), the lower platform (22) and the upper platform (23) defining a circulation channel of a gas flow from upstream to downstream along the axial direction, each blade (17) extending radially from a lower platform to an upper platform (23), the upper platform (23) comprising a body (25) from which extend an upstream hook (20a) and a downstream hook (20b) for attaching the platform to the outer casing (18), the body (25) comprising a circumferential front opening (26) and a cavity (27) formed in the body (25),the cavity (27) extending into the body (25) from the anterior circumferential opening (26) to a posterior circumferential bottom (28), the cavity (27) opening into the primary vein only downstream of the superior platform (23). Figure 4,

Description

Title of the invention: Turbomachine turbine distributor FIELD OF INVENTION

[0001] The invention relates to the field of aircraft turbomachinery and more particularly to a distributor for a low-pressure turbine of a turbomachine. PRIOR TECHNOLOGY

[0002] An aircraft turbomachine operates on the principle of combustion and includes a turbine to recover energy from the gases and then convert it into mechanical energy on a drive shaft to drive a fan that generates thrust. The turbine's efficiency, as well as its lifespan, is highly dependent on the seals between its different stages. To improve these seals, blade tips are generally fitted with scrapers that come into contact with an abradable material partially covering the casing.

[0003] However, the relative position of the blade tip (rotor and stator) with respect to the abradable can evolve during the use of the turbomachine according to various parameters including the variation of the temperature of the casing which, when it is cold, contracts, and when it is hot, expands, leading to its displacement both axially and radially with respect to the blade tip.

[0004] To better control these clearances and prevent premature degradation of the various fixed and moving parts of the turbine, it is known to control the crankcase temperature by regulating the supply of fresh air to the crankcase using an active clearance control (ACC) valve. Controlling the valve position controls the airflow, which in turn controls the clearances at the blade tips and also the crankcase temperature, which must not exceed a critical temperature, for example, 650°C during continuous operation (particularly under cruising conditions).

[0005] In the case of a twin-spool, twin-flow turbomachine, such crankcase temperature control is implemented for the low-pressure turbine. This is referred to as a cooling device known as LPTACC (for Low Pressure Turbine Active Clearance Control). Fresh air drawn from the upstream high-pressure compressor is injected onto the low-pressure turbine crankcase via manifolds extending around the crankcase and equipped with orifices.

[0006] However, by drawing air from the high-pressure compressor, this air does not contribute to the turbomachine's thrust. This extraction therefore increases fuel consumption at a given power output. Description of the invention

[0007] The invention makes it possible to reduce the amount of fresh air needed to cool a low-pressure turbine housing of a turbomachine.

[0008] According to a first aspect, the invention proposes a turbomachine turbine distributor, comprising an annular outer casing disposed around an axial direction, the outer casing being intended to be cooled by an air jet by means of a cooling system, the distributor comprising at least one aerodynamically profiled blade, at least one lower platform and at least one upper platform, the lower platform and the upper platform delimiting a circulation vein of a gas flow from upstream to downstream along the axial direction, each blade extending radially from a lower platform to an upper platform, the upper platform comprising a body from which extend an upstream hook and a downstream hook for attaching the platform to the outer casing, the body comprising a circumferential front opening and a cavity formed in the body,The cavity extends into the body from the circumferential anterior opening towards a circumferential posterior fundus, the cavity opening into the primary vein only downstream of the superior platform.

[0009] The invention is advantageously complemented by the following features, taken alone or in any technically possible combination thereof:

[0010] - the circumferential front opening is delimited by two radial walls extending in a radial plane in which the circumferential front opening extends.

[0011] - the cavity is delimited by a lower surface, an upper surface and a bottom positioned opposite the circumferential front opening, the upper surface extending axially from the bottom away from the lower surface.

[0012] - the lower surface and / or the upper surface of the cavity comprise at least a reflective portion.

[0013] - the lower surface and / or the upper surface includes a surface treatment reflective or a reflective coating.

[0014] According to a second aspect, the invention proposes an assembly comprising several distributors according to the first aspect of the invention.

[0015] According to a third aspect, the invention proposes a low pressure turbine comprising an assembly according to the second aspect of the invention.

[0016] According to a fourth aspect, the invention proposes a turbomachine comprising a low-pressure turbine according to the third aspect of the invention.

[0017] According to a fifth aspect, the invention proposes an aircraft comprising a cell and a turbomachine according to the fourth aspect of the invention, the turbomachine being fixed to the cell. DESCRIPTION OF THE FIGURES

[0018] Fig. 1 represents a double-flow turbomachine according to one embodiment of the invention;

[0019] Figure [Fig. 2] shows a cross-sectional view of a distributor of a turbine turbomachine according to an embodiment of the invention;

[0020] Fig. 3 represents a detailed cross-sectional view of a distributor of a turbomachine turbine according to one embodiment of the invention;

[0021] Figure 4 shows a perspective view of a distributor of a turbine turbomachine according to an embodiment of the invention;

[0022] Fig. 5 represents a perspective view of a distributor blade of a turbomachine turbine according to one embodiment of the invention;

[0023] Figure 6 represents an aircraft according to one embodiment of the invention.

[0024] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0025] Figure 1 represents a twin-spool, twin-flow turbomachine 1. Such a turbomachine 1 is advantageously mounted on an aircraft airframe 100, in particular under its wings by means of a pylon or mast (see Figure 6). The longitudinal axis of the turbomachine is denoted X and corresponds to the axis of rotation of the rotating parts. In what follows, the terms axial and radial are defined with respect to the X axis. Unless otherwise specified, the terms "upstream" and "downstream" refer to the overall direction of airflow through the operating turbomachine 1. Similarly, an axial direction corresponds to the direction of the longitudinal axis X, and a radial direction is a direction perpendicular to and intersecting the longitudinal axis X. Furthermore, an axial plane is a plane containing the longitudinal axis X, and a radial plane is a plane perpendicular to the longitudinal axis X.A circumference is understood as a circle belonging to a radial plane and whose center lies on the longitudinal axis X. A tangential or circumferential direction is a direction tangent to a circumference: it is perpendicular to the longitudinal axis X but does not pass through the longitudinal axis X. Finally, the adjectives "interior" (or "internal") and "exterior" (or "external") are used with reference to a radial direction such that the interior part of an element is, along a radial direction, closer to the longitudinal axis X than the exterior part of the same element.

[0026] The turbomachine 1 comprises, from upstream to downstream in the direction of gas flow, a blower 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6 and a low pressure turbine 7.

[0027] The air from the blower 2 is divided into a primary flow 8 flowing into a primary annular vein 9, and a secondary flow 10 flowing into a secondary annular vein 11 surrounding the primary annular vein 9.

[0028] The low pressure compressor 3, the high pressure compressor 4, the combustion chamber 5, the high pressure turbine 6 and the low pressure turbine 7 are arranged in the primary vein 9.

[0029] The rotor of the high-pressure turbine 6 and the rotor of the high-pressure compressor 4 are rotationally coupled via a first shaft 12 to form a high-pressure unit. The rotor of the low-pressure turbine 7 and the rotor of the low-pressure compressor 3 are rotationally coupled via a second shaft 13 to form a low-pressure unit, the blower 2 being able to be connected directly to the rotor of the low-pressure compressor 3 or via an epicyclic gear train, for example.

[0030] Fig. 2 schematically illustrates a partial view of a low-pressure aircraft turbomachine turbine 7 comprising moving wheels 14 with moving blades 15 and stators or distributors 16 with blades 17 and a casing 18. The casing 18 is designed to be cooled by a jet of fresh air by a clearance management system 19 (LPTACC).

[0031] The term "fresh air" refers to air drawn from the high-pressure compressor, which is at a temperature lower than the crankcase temperature 18, for example between 200 and 500 degrees. By comparison, the temperature of a turbine crankcase 18 is typically regulated not to exceed 650°C.

[0032] The rotating wheel 14 includes a rotating ring 19 on which rotating vanes 15 are mounted. Low-pressure distributors 16 are located downstream of the rotating wheels 14. The distributors 16 are mounted on the housing 18 by means of flanges or hooks 20a, 20b extending from the radially internal surface of the housing 18, the housing 18 also including additional hooks 24. The ends of the vanes 15 and the rotating rings 19 are surrounded by fixed rings 21 made of abradable material. The fixed rings 21 are attached to the housing or the low-pressure distributor 16.

[0033] The low-pressure distributor 16 comprises aerodynamically profiled blades 17, each extending radially from a lower platform 22 to an upper platform 23. The blades 17 are therefore in the primary gas flow channel 9. The upper platform 23 is closer to the housing 18 than the lower platform 22, the upper platform 23 being at a distance from the lower platform 22, which is itself close to the longitudinal axis X.

[0034] As can be seen more clearly in Figures 3, 4, 5, the upper platform 23 comprises a body 25 from which extend an upstream hook 20a and a hook A downstream component 20b is used to attach the upper platform 23 to the housing 18. The body 25 extends axially from upstream to downstream, from a rear radial portion 25a to a front radial portion 25b. The body 25 includes a cavity 27 formed within its thickness, which extends axially from a circumferential bottom 28 upstream (rear bottom) to a circumferential opening 26 downstream (front opening). The rear bottom and the front opening are arranged in respective radial planes (see plane PI at the front).

[0035] The cavity 27 opens onto the opening 26 before so as to open into the primary vein 9 only downstream of the upper platform 23.

[0036] Thus, the upper platform is provided with a semi-open cavity in that it only includes an opening in a radial plane of the platform at the front.

[0037] The presence of the cavity limits the thermal conduction from the distributor to the housing 18 by the hot air circulating in the primary flow 9 during the operation of the turbomachine. Indeed, the cavity creates an air interface that breaks this conduction.

[0038] In addition, the cavity 27 has, in an axial plane, a width that varies from a value d to a value D > d in the axial direction X, that is, from upstream to downstream. In particular, the cavity 27 comprises a lower surface 29 and an upper surface 30, and the rear bottom 28 is positioned opposite the front opening 26, the upper surface 30 extending axially away from the lower surface 29. The upper surface 30 therefore diverges from the lower surface 29 in the axial direction.

[0039] The diverging cavity 27 allows the airflow from the distributor blade to be guided towards the primary vein 9 (the arrows inside the cavity show the path of the flow in the cavity 27).

[0040] Alternatively or complementaryly, to improve the guidance of the airflow in the cavity 27, the lower 29 and / or upper 30 surfaces of the cavity 27 are reflective. This property is obtained either by surface treatment or by applying a reflective coating to these surfaces. Such a coating is a nickel-chromium type surface coating that increases the reflection, known as emissivity, of the radiative flux towards the vein 9.

[0041] Alternatively or additionally, the front opening 26 is delimited by two radial walls 31 to improve the mechanical strength of the platform thus obtained. The cavity is therefore open on a part at the front of the body 25 of the upper platform 23.

[0042] Thanks to the cavity 27 provided in the upper platform 23 it is possible to better control the air flow of the LPTACC and in particular to reduce the amount of air taken in.

Claims

Demands

1. Turbomachine turbine distributor (16), comprising an annular outer casing (18) disposed around an axial direction (X), the outer casing (18) being intended to be cooled by an air jet by means of a cooling system (19), the distributor (16) comprising at least one aerodynamically profiled blade (17), at least one lower platform (22) and at least one upper platform (23), the lower platform (22) and the upper platform (23) defining a flow channel (9) of an upstream to downstream gas flow along the axial direction (X), each blade (17) extending radially from a lower platform (22) to an upper platform (23), the upper platform (23) comprising a body (25) from which extend an upstream hook (20a) and a downstream hook (20b) for attaching the platform to the outer casing (18),the body (25) comprising a circumferential anterior opening (26) and a cavity (27) formed in the body (25), the cavity (27) extending in the body (25) from the circumferential anterior opening (26) towards a circumferential posterior bottom (28), the cavity (27) opening into the primary vein (9) only downstream of the superior platform (23).

2. Distributor according to claim 1, wherein the circumferential front opening (26) is delimited by two radial walls (31) extending in a radial plane (PI) in which the circumferential front opening (26) extends.

3. Dispenser according to any one of claims 1 to 2, wherein the cavity (27) is delimited by a lower surface (29), an upper surface (30) and a bottom (28) disposed opposite the circumferential front opening (26), the upper surface (30) extending axially from the bottom (28) away from the lower surface (29).

4. Distributor according to claim 3, wherein the lower surface (29) and / or the upper surface (30) of the cavity (27) comprise at least one reflective portion.

5. Distributor according to claim 4, wherein the lower surface (29) and / or the upper surface (30) comprises a reflective surface treatment or a reflective coating

6.

7.

8.

9. Assembly comprising several distributors (16) according to any one of the preceding claims. Low pressure turbine (7) comprising an assembly according to the preceding claim. Turbomachine (1) comprising a low-pressure turbine according to the preceding claim. Aircraft comprising a cell (100) and a turbomachine (1) according to claim 7, the turbomachine (1) being fixed to the cell (100).

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