The invention relates to the general field of turbomachinery single or double flow, especially the cooling of the blades ventilated distributors.

BACKGROUND

A turbomachine 1 typically includes a nacelle or air inlet (plenum) which forms an opening for the admission of a determined flow of air towards the motor itself. Generally, the turbine engine comprises one or more compression sections 4 of the air admitted into the engine (usually a low pressure section and a high pressure section). The thus compressed air is admitted into the combustion chamber 5 and mixed with fuel before being burnt.

Hot flue gases from this combustion are then expanded in various turbine stages 6, 7. A first expansion is made in a high pressure stage 6 immediately downstream of the chamber and which receives the gas at the highest temperature . The gases are expanded again by being guided through said turbine stages to low pressure 7.

A turbine, high pressure or low pressure 6 7 conventionally includes one or more stages each consisting of a row of blades fixed turbine, also called distributor 8, followed by a row of rotor blades circumferentially spaced turbine around the disk of the turbine. The distributor 8 deflects and accelerates the flow of gas from the combustion chamber to the appropriate mobile blades turbine at an angle and a speed for driving in rotation said movable vanes and the disk of the turbine.

The distributor 8 comprises a plurality of blades arranged radially with respect to an axis X of rotation of the turbomachine connecting a radially inner annular element (or inner platform) and a radially outer annular element (or outer platform). The assembly forms an annular vein facing the mobile blades of the turbine.

More specifically, the distributor 8 is formed of fixed blades arranged in a ring which can, where appropriate, be divided into a plurality of segments distributed circumferentially around the axis X of the turbomachine. Each segment includes one or more adjacent fixed blades integral with a ring sector member and a means for retaining upstream and a downstream restraining means. Here, upstream and downstream are defined by the direction of flow of the gases in the turbine engine.

The distributor blades 8 are generally obtained by molding and are made of a nickel-base superalloy or single crystal material which has very good heat resistance.

Distributors 8 high pressure turbine 6 of turbine engine parts are exposed to very high thermal stresses. They are actually placed at the outlet of the combustion chamber and are traversed by extremely hot gas which subject to very high thermal stresses, the temperature of the combustion chamber outlet in gas being much greater than the melting temperature the materials constituting the distributor 8. the vein temperature at the inlet of the dispenser 8 may indeed locally reach 2000 ° C, whereas it is not uncommon in certain points significant damage to the part whose melting temperature is below 1400 ° C.

To decrease the room temperature and limiting its degradation, cooling dispensers 8 is necessary. Usually, the dispensers 8 cooling function is provided by one or more inserts placed inside of the distributor blades 8. An insert is a sheet metal part or hollow molding comprising cylinder bores typically trained using a laser and conforming better to the shape of the vane to cool. Air "fresh" taken at the compressor of the turbomachine impact by these holes the inner face of the vane to cool.

The inner face of the blading is thus cooled by jets of impacts and a forced convection between the insert and the wall of the profile. The distance between the insert and the inner face of the blading, called the gap, is constantly done.

However, two phenomena governing the cooling of the blading, namely the jet impacts and forced convection between the insert and the inner surface of the blading. One of the parameters dominant in the cooling efficiency of these two modes is the value of the gap. In fact, the air gap should be minimal if one wishes to maximize the forced convection, but it should not be too low if it is desired to maximize the height of impact of the jets (which corresponds to the distance between the outlet a bore and the inner wall of the blading) to optimize the effectiveness of the jet impacts.

Currently, the gap is constant, a compromise is made on its value so as not to degrade too strongly the jet impacts the benefit of an effective forced convection.

The performance of a turbine engine, however, are in part related to the ventilation system in place. Indeed, all air samples taken to cool the components penalize the thermodynamic cycle of the turbine engine, degrading the power and specific consumption of the engine. It is therefore necessary to limit to the minimum necessary air samples. The efficiency of cooling systems used is therefore essential for engine performance and service life of the component.

EP 2228517 discloses a dispenser vane of a turbomachine a blade and an insert accommodated in the blade in which are formed apertures. The wall of the insert is further locally bent at the orifices so as to cross their air jet and create turbulence.

EP 1284338 describes in turn a nozzle vane of a turbomachine a blade and an insert accommodated in the blade in which are formed apertures. The wall of the insert is discontinuous so as to form overlap and changing the direction of impact of the air jets fed through the orifices on the inner face of the blade.

SUMMARY OF THE INVENTION

An object of the invention is to optimize cooling distributors blades to limit the amounts of fresh air used, the ultimate objective limitation thermomechanical damage (cracks, burns, oxidation, etc.).

For this, the invention provides a dispenser of a turbomachine vane, said vane having:

- a blade having a pressure side wall and a suction side wall, and

- an insert located between the pressure wall and suction wall, the insert comprising:

* A closed wall having an outer skin extending opposite to the pressure side wall and the suction side wall and an inner skin facing away from the outer skin, the outer skin of the closed wall and the wall of the blade facing being separated by an air gap, and

* A series of through holes formed in the closed wall between the outer skin and the inner skin.

The insert of the blading comprises a plurality of generally hemispherical-shaped indentations in egg head or drop formed in the closed wall and opening into the outer skin. The through holes are also formed in said recesses and impact heights between said through holes and the pressure side wall or extrados facing wall are larger than the air gap.

Some features preferred but not limiting to the blades described above are the following, individually or in combination:

- the through holes have a periphery having a maximum width defined, a ratio between the height of impact and the maximum width of all or part of the through holes is between 2.5 and 10, preferably between 2.5 and 7, more preferably between 2.5 5 and typically between 2.8 and 3.2, for example equal to 3,

- the through holes are circular, the maximum width of said through holes corresponding to their diameter,

- the inner skin of the closed wall of the insert further comprises bulges, the through holes opening into said bulges, - the height of impact is between 1 .0 mm and 3.0 mm, preferably between 1 mm and 2 mm, typically from 1 mm to 1 .5 mm,

- the air gap is between 0.5 mm to 1 .0 mm, preferably between 0.5 mm and 0.8 mm, and typically equal to 0.6 mm, and / or

- an inner face of the pressure wall and suction wall further comprises pins protruding from said inner face towards the outer skin of the insert.

According to a second aspect, the invention also provides a dispenser for a turbine of a turbomachine including an inner platform and an annular coaxial outer annular platform about an axis and a series of nozzle vanes as described above , said blades being spaced apart circumferentially about the axis between the inner platform and the outer platform.

According to a third aspect, the invention provides a method of manufacturing a nozzle vane as described above, wherein the insert is produced by selective melting of a powder bed by high energy beam.

BRIEF DESCRIPTION OF DRAWINGS

Other features, objects and advantages of the invention appear better on reading the detailed description that follows, and the accompanying drawings given as non-limiting examples and in which:

Figure 1 is a perspective view of an embodiment of an insert of a nozzle vane according to the invention,

Figure 2 is a side view of an embodiment of a nozzle vane according to the invention comprising the insert of Figure 1, in which the insert is shown in phantom inside the blade ,

Figure 3 is a partial view of an exemplary embodiment of a nozzle vane according to the invention,

Figure 4 is a perspective view of an exemplary embodiment of a distributor consistent with the invention and

Figure 5 is a simplified sectional view of an embodiment of a turbomachine comprising a dispenser according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

The invention will be described particularly with reference to a high pressure turbine 6 single-stage, thus comprising a high pressure valve 8 (or stator) and an impeller (or rotor). However, this is not limitative insofar as the turbine 6 may include more stages and that the invention also finds application in both a low pressure turbine 7 in a compressor 4 (high or low pressure), which also each comprise several fixed floors. Furthermore, the dispenser 8 may be in one piece or sectorized.

6 turbine conventionally includes one or more stages, each consisting of a valve 8, followed by a row of turbine moving blades 3 of circumferentially spaced around the disc of the turbine 6.

The distributor 8 deflects the gas flow from the combustion chamber 5 to the moving blades at a suitable angle and speed in order to rotate the vanes and the disk of the turbine 6. This

distributor 8 comprises a plurality of stationary blades radially disposed relative to the axis X of rotation of the turbomachine 1 connecting a radially inner annular platform 9a and a radially outer annular platform 9b.

Each airfoil 10 includes a blade 12 having a pressure side wall 16 and an extrados wall 14 interconnected by a leading edge 18 and a trailing edge 19. The leading edge 18 of a blade 12 corresponds in the anterior part of its aerodynamic profile. It faces the gas flow and divides it into a pressure side air flow along the pressure side wall 16 and a suction air flow along the suction wall 14. The trailing edge 19 in turn corresponds to the posterior part of the aerodynamic profile, which meet the pressure face and suction flows.

The valve 8 further comprises a cooling system.

For this purpose, each vane 10 includes an insert 20 housed in the blade 12 between the pressure side wall 16 and suction side wall 14. The insert 20 comprises:

- a closed wall 12 having an outer skin 24 extending opposite to the pressure side wall 16 and suction side wall 14 and an inner skin 26 opposite the outer skin 24, outer skin 24 of the wall 12 and the closed wall of the vane 10 facing being separated by a gap 30, and

- a series of through holes 28 formed in the closed wall 12 between the outer skin 24 and the inner skin 26.

A series of recesses 25 which open into the outer skin 24 are further formed in the closed wall 12 of the insert 20. The through holes 28 are formed in the recesses 25 and impact heights h between the through holes 28 and the facing wall of the blade 12 are larger than the air gap 30.

In one embodiment, the air gap can be constant. By gap 30, here will be understood the shortest distance between a point the outer skin 24 of the closed wall 12 of the insert 20 around the recesses 25 and the facing wall of the blade 12, that is, -dire the pressure side wall 16 or the suction side wall 14. the air gap 30 is measured in a plane parallel to the plane tangential to the inner platform 9a at the root of the blade 12, and is generally constant between the inner platform and the outer platform 9a 9b.

By height of impact h, it is understood the distance between the output (relative to the flow direction of the cooling air flow) of the through hole 28 and the inner face 15 of the facing wall of the blade 12, that is to say the pressure side wall 16 or the suction side wall 14, along the axis X of the cooling air flow in the through hole 28.

This configuration of the vane 10 allows both to ensure a small air gap 30 between the blade 12 and the insert 20, and thus maintain the effectiveness of the forced convection during the evacuation of the air after impact through the through holes 28, while improving the effectiveness of impact thanks to the increased height h of impact by the depressions 25 which shifts the output through holes 28 relative to the outer skin 24 of the insert 20 .

In one embodiment, the height of impact h is between 1 .0 mm and 3.0 mm, preferably between 1 .0 and 2.0 mm, for example about 1 .5 mm, where the gap 30 is between 0.5 and 1 .0 mm, preferably between 0.5 and 0.8 mm, for example of the order of 0.6 mm.

The through holes 28 have a periphery having a maximum width L defined. By width L of the periphery, it will be understood by the distance between two parallel straight lines (or "support lines) that are tangential at two distinct points in the closed curve formed by the periphery of the through hole 28 at the recess. L maximum width corresponds to the largest width L of the periphery. When a through-hole 28 has a circular section, the maximum width L is for example equal to the external diameter of the circle. Alternatively, the through hole 28 may be square or rectangular section, the maximum width L then corresponding to its diagonal.

To further optimize the effectiveness of impact of the jets on the inner face 15 of the blade 12, the ratio between the height of impact h and the maximum width L of all or part of the orifices is between 2.5 and 10 , preferably between 2.5 and 5 mm, typically between 2.5 and 5, for example between 2.8 and 3.2. Typically, in the case of a blade 12 of which the closed wall 12 has a thickness of between 0.4 and 0.6 mm with an air gap 30 substantially equal to 0.6 mm, the optimum ratio between the height of impact h and the width L of the maximum holes is of the order of 3. such a relationship allows in particular to obtain an impact distance of 1 .5 mm.

The recesses 25 may have a generally hemispherical or "egg head" or drop. Note that, depending on the height of impact h sought and the thickness of the outer wall, the inner skin 26 of the insert 20 may not be planar.

This form also allows to expect from such a height of impact h reports maximum width L.

Thus, in the embodiment illustrated in Figures 1 to 3, the gap 30 is 0.6 mm, the closed wall of the blade 12 has a thickness of about 0.6 mm while the height of impact desired h is 1 .5 mm. The recesses 25 are therefore obtained by changing the geometry of the inner skin 26 and outer skin 24 of the closed wall 12, and not by making a recess in said outer wall. The inner skin 26 of the closed wall 12 is not smooth is comprises bulges 27 corresponding to the recesses 25 formed in the outer skin 24. Here, the recesses 25 are hemispherical: the outer skin 24 of the closed wall 12 has therefore a series of hemispherical hollow at the bottom of which are formed the through holes 28,

In an alternative embodiment, the inner face 15 of the pressure side wall 14 and the suction wall 16 of the blade 12 may include studs 13 projecting from said inner face 15 towards the insert 20, to protect the jet impinging the inner face 15 of the blade 12 against the shear flow. The pads 13 may for example have a generally triangular cross-section or V-shaped cutting edge section extending towards the leading edge 18 of the blade 12.

This alternative embodiment, coupled with L maximum width L and the height of impact h optimum, allows to obtain an effective cooling and constant throughout the profile of the blade 12.

The insert configuration 20 and, if applicable, achieving pads 13 on the inner face 15 of the blade 12, provides a significant gain on local efficiency impact the cooling of the distributor 8 and the possibility of manage the efficiency of the forced convection in the air gap 30 while limiting the shear downstream rows of impacts by those located further upstream. Optimizing these parameters also enables to best exploit the air used to cool the wall. This allows isoflow to be more thermally efficient (gain life) or reduce the flow-isothermal efficiency, which results in engine performance gain.

The blade 12 can be obtained in conventional manner, for example by casting in a suitable material such as a superalloy based on nickel or single crystal material which has very good heat resistance. Alternatively, the blade 12 can be obtained by selective melting of a powder bed by high energy beam.

The insert in turn can for example be obtained by casting or by selective melting of a powder bed by high energy beam. Selective melting of a powder bed by high-energy beam makes it possible in particular to obtain an insert for a lower cost (in comparison with the foundry) providing recesses 25 (and optionally of

bulges 27) of suitable shape. The outer wall of the insert may then have a thickness of between 0.4 and 0.8 mm, for example about 0.6 mm, or 0.4 mm.

CLAIMS

1. Blading (10) distributor (8) of a turbomachine (1), said vane (10) having:

- a blade (12) comprising a pressure side wall (16) and a suction side wall (14), and

- an insert (20) located between the pressure side wall (16) and the suction side wall (14), the insert (20) comprising:

* A closed wall (22) having an outer skin (24) extending opposite to the pressure side wall (16) and the suction wall (14) and an inner skin (26) opposite the skin external (24), the outer skin (24) of the closed wall (22) and the wall of the vane (12) facing being separated by an air gap (30), and

* A series of through holes (28) formed in the closed wall

(22) between the outer skin (24) and the inner skin (26), and

* A series of recesses (25) formed in the closed wall (22) and opening in the outer skin (24), the through holes (28) being formed in said recesses (25), impact heights (h) between said through holes (28) and the pressure side wall (16) or the suction wall (14) facing being larger than the air gap (30), the recesses (25) have a generally hemispherical shape, in head egg or teardrop.

2. vane assembly (10) according to claim 1, wherein the through holes (28) have a periphery having a width (L) defined maximum, a ratio of the impact height (h) and width (L) maximum all or part of the through holes (28) being between 2.5 and 10, preferably between 2.5 and 7, more preferably between 2.5 and 5 mm, typically between 2.8 and 3.2, for example equal to 3.

3. vane assembly (10) according to claim 2, wherein the through holes (28) are circular, the width (L) maximum of said through holes (28) corresponding to their diameter.

4. vane assembly (10) according to one of claims 1 to 3, wherein the inner skin (26) of the closed wall (22) of the insert (20) further comprises bulges (27), the through holes (28) opening into said bulges (27).

5. vane assembly (10) according to one of claims 1 to 4, wherein the impact height (h) is between 1 .0 mm and 3.0 mm, preferably between 1 mm and 2 mm, typically between 1 mm and 1 .5 mm.

6. vane assembly (10) according to one of claims 1 to 5, wherein the gap (30) is between 0.5 mm to 1 .0 mm, preferably between 0.5 mm and 0.8 mm, and typically equal to 0.6 mm .

7. vane assembly (10) according to one of claims 1 to 6, wherein an inner face (15) of the pressure side wall (16) and the suction wall (14) further includes studs (13 ) projecting from said inner face (15) towards the outer skin (24) of the insert (20).

8. The dispenser (8) of a turbomachine (1) comprising an inner annular platform (9a) and an outer annular platform (9b) which are coaxial about an axis (X) of the dispenser (8),

the distributor (8) being characterized in that it comprises a series of blades (10) of valve (8) according to one of claims 1 to 7 circumferentially distributed about the axis (X) between the inner platform ( 9) and the outer platform (9b).

9. A method of manufacturing a vane (10) distributor (8) according to one of claims 1 to 7, characterized in that the insert (20) is produced by selective melting of a powder bed by beam high energy.