Cooling jacket of a hollow distributor blade

Description

Technical Field

[0001] The present invention relates to the general field of aeronautical turbomachines and in particular to aircraft turbomachines such as turbojets and turboprops, and it relates more particularly to the hollow distributor blades of a gas turbine engine comprising a cooling jacket. Prior art

[0002] A turbine of a gas turbine engine typically comprises one or more rows of turbine blades spaced circumferentially around the turbine rotor. It also comprises a nozzle generally comprising a plurality of fixed or guide vanes which extend substantially radially between radially outer and radially inner coaxial annular platforms and which are circumferentially spaced from one another. These fixed nozzle vanes, making it possible to direct the flow of vein gas towards the turbine blades located downstream of the nozzle at an angle and at a speed appropriate to rotate the blades and the turbine rotor, are therefore in direct contact with the hot gases coming from the combustion chamber and are subjected to high temperatures.They therefore need to be cooled and, in order to ensure effective cooling of a fixed distributor vane, it is desirable to have a cooling device which is thermally efficient to enable high thermal power to be dissipated using a moderate air flow.

[0003] Furthermore, it is desirable that this cooling device be sealed to ensure that the mobilized air is only dedicated to cooling the blade. Indeed, the higher the sealing of the cooling device, the greater its overall efficiency, this being an increasing function of the sealing and thermal efficiency of the cooling device.

[0004] The state of the art includes in particular documents FR3066783A1 and US5145315A. It is also known, for example, with application FR2976616 filed in the name of the applicant, to use a ventilation system comprising a tubular jacket made of multi-perforated sheet metal to cool the hollow blade of a distributor by impacts of cooling air passing through the orifices made in the walls of the jacket. This air taken upstream then flows downstream where it is evacuated into the gas stream through perforations provided along the wall of the trailing edge of the blade. It should be noted that the internal face of the wall of the blade may possibly be provided with flow-disrupting elements which promote heat exchanges between the air circulating between the jacket and the wall of the blade.

[0005] During assembly, the liner, which has been previously shaped and fitted with an air inlet sleeve and a closure plate to form a single-piece assembly, is slid into the internal cavity of the hollow blade of the distributor through the opening made in the radially external annular platform. The liner is then made integral with the blade by welding or brazing along its edge in contact with the wall of the opening made in this radially external annular platform. The opposite part of the liner is simply guided in the opening made in the radially internal annular platform of the blade, which forms a slide to allow relative movements between the blade and the liner. These longitudinal movements are due to temperature variations during operation of the turbomachine and to the fact that the two parts are different in the nature of the materials from which they are made and their method of manufacture.

[0006] This solution, although generally satisfactory, nevertheless places little importance on the proper air supply to the orifices in the liner located near the leading edge of the distributor blades and on the robustness of the air supply to the inter-disc cavities of the turbine. Indeed, the interior of the liner consists of only a single cavity supplying all the orifices in the liner. In such a device, the air preferentially goes to the circuits and / or orifices where the pressure is the lowest. Thus, as soon as the air enters the liner through the air inlet sleeve, it will primarily go to the orifices in the liner located closest to the perforations provided along the wall of the trailing edge of the distributor blade, thereby de-supplying the perforations located near the leading edge of the distributor and the inter-disc cavities, leading to a loss of robustness in sealing and cooling of these same cavities. Statement of the invention

[0007] The main aim of the present invention is therefore to overcome such drawbacks by proposing a cooling jacket intended to be mounted in a hollow distributor blade of a turbomachine which allows a better distribution of the ventilation air flow admitted into the jacket. One aim is also to provide a portion of this ventilation air flow to other components of the turbomachine, in particular to the inter-disc cavities of a turbine, in order to seal them and cool the turbine discs. Another aim is still to propose a method of assembling a turbine distributor which is economically advantageous with the lowest possible production cost.

[0008] These goals are achieved by a cooling jacket for a hollow turbine nozzle blade of a turbomachine, comprising: a main body extending in a radial direction between a radially inner end and a radially outer end and comprising extrados and intrados faces and a central intake duct defining a first ventilation air circulation zone and connected to these two faces by two separating walls defining second and third ventilation air circulation zones, each of the extrados and intrados faces comprising at least two rows of holes for discharging ventilation air from the second and third ventilation air circulation zones, an outer plate arranged at the radially outer end of the main body, the outer plate comprising first, second and third orifices for admitting ventilation air respectively into the first, second and third ventilation air circulation zones, and an inner plate arranged at the radially inner end of the main body,the internal plate having a central opening for evacuating air from the first ventilation air circulation zone, , the external and internal plates being secured by brazing to the main body to form a single-piece assembly with three independent and mutually sealed ventilation air circulation zones, before its assembly in the hollow blade of the turbine distributor.

[0009] Preferably, the main body and the external and internal plates are made using additive manufacturing and the drilling is carried out using die-sinking or laser electroerosion.

[0010] Advantageously, the first orifice has a section which, relative to the number of blades, is greater than the sum of the sections of the injectors ensuring the downstream ventilation air flow rates, and the second and third ventilation air intake orifices each have a section which is less than the sum of the sections of the holes respectively ensuring the evacuation of the ventilation air from the second and third ventilation air circulation zones.

[0011] The present invention also relates to a turbomachine turbine distributor comprising two coaxial annular platforms between which extend substantially radial hollow blades, each comprising a cooling jacket as mentioned above.

[0012] The present invention also relates to an aeronautical turbomachine, such as an aircraft turbojet or turboprop, comprising a turbine distributor as mentioned above.

[0013] Finally, the present invention relates to a method for assembling a cooling jacket for a hollow turbine nozzle blade of a turbomachine, characterized in that it consists of: producing a main body extending along a radial axis between a radially external end and a radially internal end and comprising extrados and intrados faces and a central intake duct defining a first ventilation air circulation zone and connected to these two faces by two separating walls defining second and third ventilation air circulation zones; producing an external plate comprising first, second and third orifices for admitting ventilation air respectively into the first, second and third ventilation air circulation zones; producing an internal plate comprising a central opening for discharging ventilation air from the first ventilation air circulation zone;machining at least two rows of holes on each of the extrados and intrados faces of the main body to evacuate the ventilation air from the second and third ventilation air circulation zones; and securing by brazing the external and internal plates to the main body to form a single-piece assembly with three independent and mutually sealed ventilation air circulation zones, before mounting it in the hollow blade of the turbine distributor.;

[0014] Preferably, the extrados and intrados faces constituting the external shape of the main body are configured to fit an internal cavity of the hollow blade of the distributor.

[0015] Advantageously, the contact surfaces between the main body and each of the external and internal plates and the external and internal surfaces of the main body are further polished before they are joined into said single-piece assembly.

[0016] Preferably, the metallic material has a thickness of at least 0.5 mm. Brief description of the drawings

[0017] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character and in which: [ Fig. 1 ] there figure 1 is a schematic perspective view of a turbine distributor sector intended to receive in each of its hollow blades a cooling jacket according to the invention, [ Fig. 2 ] there figure 2 is an external perspective view of a cooling jacket according to the invention intended to be mounted in each of the hollow blades of the turbine distributor of the figure 1 , [ Fig. 3 ] there figure 3 details the upper and inner parts of the shirt of the figure 1 , [ Fig. 4 ] there figure 4 details the lower and inner parts of the shirt of the figure 1 , And [ Fig. 5 ] there figure 5 is a sectional view of the cooling jacket mounted in the internal cavity of the hollow blade of the turbine nozzle of the figure 1 . Description of the embodiments

[0018] There figure 1 shows a turbine distributor sector 10 of a turbomachine, such as an aircraft turbojet or turboprop, comprising two coaxial annular platforms, respectively internal 12 and external 14, which delimit between them an annular gas flow vein and between which extend substantially radial hollow blades 16 (the number of blades possibly being of the order of several tens). The external platform 14 comprises radially external upstream 18 and downstream 20 annular rims comprising axial annular tabs 22 oriented upstream and intended to be engaged in corresponding axial annular grooves (not shown) of a turbine casing. The terms external and internal are understood in relation to the distance in the radial direction of the elements concerned from the longitudinal axis of the turbomachine around which the turbine distributor extends.

[0019] The hollow blades of the turbine distributor comprise internal cavities 24 in each of which is mounted a cooling jacket 26 (visible on the figure 2 ) intended to ensure circulation of ventilation air (see the arrows In and Out, respectively air inlet and outlet) coming from a supply enclosure (not shown) radially external to the external platform 14, both in the hollow blade 16 (the air exiting through the slots 28 of the trailing edge) and towards a distribution enclosure (not shown) radially internal to the internal platform 12 and intended to supply air to the inter-disc cavities of the turbine.

[0020] In accordance with the invention and as illustrated in external perspective at figures 2 à 4 , the cooling jacket 26 comprises the following elements: a hollow main body 30 extending in the radial direction between a radially external end and a radially internal end and comprising an extrados face 30a and an intrados face 30b, the external shape of which constituted by these two faces substantially matches the internal cavity 24 of the blade 16 of the distributor and which is made integral with a central intake duct 32 defining a first ventilation air circulation zone 34a, by means of two thick separation walls 36a, 36b arranged on either side of this central intake duct, between the central intake duct and each of the two faces 30a, 30b of the main body, so as to define on either side of these walls, advantageously aligned, two separate upstream and downstream cavities, respectively defining second and third ventilation air circulation zones 34b, 34c,sealed from each other and from the first ventilation air circulation zone 34a and capable of being supplied with ventilation air independently of each other, the extrados and intrados faces of the main body each comprising several rows of holes 37 (typically at least two, one per cavity) in order to allow cooling by impact of the internal wall of the blade 16 of the distributor, an external plate (first plate 38) intended to be secured to the radially external end of the main body and on which are pierced both a first orifice 38a supplying ventilation air to the central intake duct 32 containing the first ventilation air circulation zone 34a, a second orifice 38b supplying ventilation air to the second ventilation air circulation zone 34b and a third orifice 38c supplying ventilation air to the third ventilation air circulation zone 34c,and an internal plate (second plate 40) intended to be secured to the radially external end of the main body and on which a single central opening 40a is pierced in order to allow the ventilation air circulating in the central intake duct 32 to go directly towards the inter-disc cavities of the turbine.

[0021] The cooling jacket is advantageously entirely produced using additive manufacturing using the metal 3D printing process which takes place in the following phases.

[0022] First of all, in a first phase, on the same plate of an additive manufacturing machine (or 3D printer) without recourse to any specific printing support, the main body 30 (including its central intake duct 32 and the separating walls 36a, 36b), the upper plate 38 and the internal plate 40 are preferably printed separately (to facilitate the subsequent polishing step). In order not to obtain surfaces deformed by the scraper of the 3D printer, a minimum material thickness of 0.5 mm is also recommended. The printing of the main body is done vertically, starting with its lower part (the bottom of the body) or its upper part (the top of the body). The material used is a metallic material, typically among metal alloys of the Inconel ® type.

[0023] Then, once the printing is finished, a second phase is carried out, preferably by electroerosion by sinking (EDM for "electrical discharge machining"), of the various holes 37 of each extrados and intrados face of the main body. However, laser drilling is also possible.

[0024] In a third phase, a polishing operation of the functional surfaces of the different elements (contact surfaces between the main body and the plates and external and internal surfaces of the sleeve) is preferably carried out.

[0025] Finally, in a last phase, a brazing operation of the external and internal plates on the main body makes it possible to finalize the jacket into a single-piece assembly with three independent and sealed ventilation air circulation zones before its assembly in the cavity 24 of the blade 16 of the distributor as shown in the section of the figure 5 .

[0026] The cooling jacket obtained in this way by additive manufacturing is then, as is known, made integral and sealed with the internal wall of the distributor by welding or brazing at the level of its external plate 38 (see the weld bead 42), the internal plate 40 of the jacket being simply guided in the lower part of the distributor which forms a slide to allow relative movements between the blade 16 and the cooling jacket 26.

[0027] Thus mounted and fixed in the cavity 24, the cooling jacket 26 makes it possible to perform the following functions: impact cooling of the upstream portion (near the leading edge) of the inner wall of the distributor blade, the ventilation air entering through the second orifice 38b to supply the upstream cavity 34b, then being evacuated through a first row of holes 37 to impact the inner wall of the distributor blade. The air will then circulate in the space delimited by the inner wall of the distributor blade and the outer wall of the jacket to then be evacuated through the outlet orifices located on the trailing edge of the distributor blade. impact cooling of the downstream portion (near the trailing edge) of the inner wall of the distributor blade, the ventilation air entering through the third orifice 38c to supply the downstream cavity 34c, then being evacuated through another row of holes 37 to impact the inner wall of the distributor blade.The air will then circulate in the space delimited by the internal wall of the distributor blade and the external wall of the jacket to then be evacuated through the same outlet orifices located on the trailing edge of the distributor blade. a supply of ventilation air for the inter-disc cavities, the air entering through the first orifice 38a, circulating in the central intake duct 32 and being evacuated through the central opening 40a of the internal plate 40.

[0028] It will be noted that the second 38b and third 38c ventilation air intake orifices may be of any shape (rectangular, circular, ovoid, etc.) but must have sections allowing the respective flow rates of the upstream 34b and downstream 34c cavities to be controlled. In other words, the section of these orifices must be less than the sum of the sections of the holes making up the respective cavity.On the contrary, the first orifice 38a (as well as the central opening 40a which may have the same dimension or a smaller dimension) which may also be of free form, must not have a section controlling the downstream flow rates (this role is in fact assigned to the injectors located in the inter-disc cavities), that is to say that the sum of all the sections of the first orifices 38a of the distributor must be greater than the sum of the sections of the injectors ensuring the downstream ventilation air flow rates (the calculation of the flow rate for an orifice must therefore be related to the number of blades of the distributor).

[0029] The main advantages of the invention resulting from the aforementioned structure are therefore the following: The ventilation air supply to the upstream holes is separate from the holes located downstream of the jacket. The ventilation air supply to the inter-disc cavities is separate from the supply to the holes and without heating when passing through the central intake duct of the jacket. The manufacturing cost of the part is reduced.

Claims

1. A cooling jacket (26) for a hollow airfoil of a turbine nozzle (10) of a turbomachine, including: - a main body (30) extending along a radial direction between a radially outer end and a radially inner end and including suction (30a) and pressure (30b) faces and a central intake duct (32) defining a first ventilation air circulation area (34a) characterized in that the central intake duct (32) is connected to these two faces by two separating walls (36a, 36b) defining second (34b) and third (34c) ventilation air circulation areas, each of the suction and pressure faces including at least two rows of drill holes (37) to expel the ventilation air from the second and third ventilation air circulation areas, - an outer plate (38) disposed at the radially outer end of the main body, the outer plate (38) including first (38a), second (38b) and third (38c) holes to allow the ventilation air respectively into the first (34a), second (34b) and third (34c) ventilation air circulation areas, and - an inner plate (40) disposed at the radially inner end of the main body, the inner plate (40) including a central opening (40a) to expel air from the first ventilation air circulation area (34a), the inner and outer plates being secured by soldering to the main body (30, 32, 36a, 36b) to form a one-piece unit with three ventilation air circulation areas, independent and airtight with respect to one another, before its installation in the hollow airfoil (16) of the turbine nozzle (10).

2. The cooling jacket as claimed in claim 1, characterized in that the main body (30, 32, 36a, 36b) and the outer (38) and inner (40) plates are made using additive manufacturing and the drill holes (37) are made using electrical discharge machining or by laser.

3. The cooling jacket as claimed in claim 1 or claim 2, characterized in that the first hole (38a) includes a section which, in proportion to the number of airfoils, is greater than the sum of the sections of the injectors ensuring the ventilation air flow rates downstream.

4. The cooling jacket as claimed in claim 1 or claim 2, characterized in that the second (38b) and third (38c) ventilation air intake holes each include a section which is less than the sum of the sections of the drill holes respectively ensuring the expulsion of the ventilation air from the second (34b) and third (34c) ventilation air circulation areas.

5. A turbine nozzle (10) of a turbomachine including two coaxial annular platforms (12, 14) between which substantially radial hollow airfoils (16) extend, each including a cooling jacket as claimed in any of claims 1 to 4.

6. An aeronautical turbomachine, such as a turbojet engine or a turboprop engine of an airplane, including at least one turbine nozzle as claimed in claim 5.

7. A method for assembling a cooling jacket (26) of a hollow airfoil (16) of a turbine nozzle (10) of a turbomachine, characterized in that it consists in: making a main body (30) extending along a radial direction between a radially outer end and a radially inner end and including suction (30a) and pressure (30b) faces and a central intake duct (32) defining a first ventilation air circulation area (34a) and connected to these two faces by two separating walls (36a, 36b) defining second (34b) and third (34c) ventilation air circulation areas; making an outer plate (38) including first (38a), second (38b) and third (38c) holes for taking in ventilation air respectively in the first, second and third ventilation air circulation areas; making an inner plate (40) including a central opening (40a) for expelling the ventilation air from the first ventilation air circulation area; machining at least two rows of drill holes (37) on each of the suction and pressure faces of the main body to expel the ventilation air from the second and third ventilation air circulation areas; and securing by soldering the outer (38) and inner (40) plates to the main body (30, 32, 36a, 36b) to form a one-piece unit with three ventilation air circulation areas, independent and airtight with respect to one another, before its installation in the hollow airfoil (16) of the turbine nozzle (10).

8. The assembling method as claimed in claim 7, characterized in that the suction (30a) and pressure (30b) faces constituting the outer shape of the main body are configured to fit an inner cavity (24) of the hollow airfoil (16) of the nozzle (10).

9. The assembling method as claimed in claim 7 or claim 8, characterized in that the contact surfaces between the main body and each of the outer (38) and inner (40) plates and the outer and inner surfaces of the main body (30, 32, 36a, 36b) are moreover polished before they are secured to said one-piece unit.

10. The assembling method as claimed in any of claims 7 to 9, characterized in that the main body and the outer and inner plates are printed on a metallic material having a thickness of at least 0.5 mm.