Cooling device for a turbine of a turbomachine

Abstract

This document relates to a turbomachine assembly comprising cooling tubes (23) extending circumferentially around a turbomachine housing, each cooling tube (23) being fixed to the housing by at least one retaining collar (100), wherein, for at least one retaining collar, an annular sleeve (104) surrounds the cooling tube (23) inserted into said retaining collar and is housed within said retaining collar, characterized in that said sleeve (104) is made of a material having a roughness Ra of less than 1.6 and a thermal resistance up to a temperature of 350°C. Figure to be published with the abbreviation: [Fig. 7]

Description

Title of the invention: Cooling device for a turbine of a turbomachine Technical field of the invention

[0001] The present document relates to a cooling device for a turbine of a turbomachine, such as for example an aircraft turbomachine, in particular a double-flow turbomachine. State of the prior art

[0002] [Fig.l] represents a double-flow, double-body turbomachine 1. The axis of the turbomachine is referenced X and corresponds to the axis of rotation of the rotating parts.

[0003] The turbomachine 1 comprises, from upstream to downstream in the direction of gas flow, a fan 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.

[0004] The air from the blower 2 is divided into a primary flow 8 flowing in a primary annular vein 9, and a secondary flow 10 flowing in a secondary annular vein 11 surrounding the primary annular vein 10.

[0005] 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.

[0006] 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 so as to form a high pressure body.

[0007] The rotor of the low pressure turbine 7 and the rotor of the low pressure compressor 3 are coupled in rotation by means of a second shaft 13 so as to form a low pressure body, the fan 2 being able to be connected directly to the rotor of the low pressure compressor 3 or else by means of an epicyclic gear train for example.

[0008] As can be better seen in [Fig. 2], the low-pressure turbine 7 comprises in particular different successive stages comprising moving wheels 14 and fixed parts. The moving wheel comprises a disc 15 at which blades 16 are mounted. The ends of the blades 16 are surrounded by a fixed ring 17 made of abradable material, said ring 17 being fixed to the casing 18 of the turbine. Distributors 19 are located downstream of the moving wheels 14. The distributors 19 and the rings 17 are mounted on the casing by means of flanges or hooks 20 extending from the radially internal surface of the casing 18.

[0009] In order to guarantee a high efficiency of the turbomachine, it is necessary to limit the flow of air not passing through the moving wheels 14 of the different stages, that is to say to limit the leaks between the radially external ends of the blades 16 and the ring 17 made of abradable material. To this end, it is necessary to control the clearance at this interface, this clearance being highly dependent on the temperature of the casing 18, and in particular of the zones of said casing 18 comprising the hooks or flanges 20 supporting the ring 17.

[0010] The primary air flow from the combustion chamber 5 has a very high temperature and heats the parts located downstream, such as the fixed and moving parts of the turbine 6, 7.

[0011] In order to control the aforementioned clearance and to avoid any premature deterioration of the various fixed and moving parts of the turbine, it is necessary to provide effective cooling devices which can be easily integrated into the environment of the turbomachine.

[0012] Such a cooling device 21 of a casing 18 of a low pressure turbine 7, visible in [Fig. 3], comprising collector boxes 22, each collector box 22 forming a channel extending axially.

[0013] The device 21 further comprises tubes 23 extending circumferentially on either side of the collector boxes 22. Said tubes 23, also called ramps, are formed by curved pipes of circular section, each tube 23 extending circumferentially around the casing, for example at an angle of approximately 90°.

[0014] Each tube 23 has an air inlet opening into the channel of the corresponding collector housing 22 and a closed distal end. Each tube 23 further comprises a cylindrical wall provided with air ejection orifices facing the casing 18, so that cooling air can penetrate into the collector housings 22 then into the tubes 23 before opening through the orifices facing the casing 18, so as to cool it. This is particularly referred to as impact cooling since the air impacts the casing 18.

[0015] All the tubes 23 are held together on the casing 18 by means of several sheets 24, at different locations on the circumference of the casing 18. The tubes 23 are fixed to the sheets 24 by fixing collars 26. One of the fixing collars 26 is shown in [Fig.4] and comprises a deformable metal tab surrounded by two layers of silica to protect the tube 23 from metal-to-metal friction.

[0016] In operation, the silica layers of the fixing collars 26 are subject to high thermo-mechanical stresses due to the radiant heat of the casing 18 which then exceeds the limit of use of the silica. These stresses can lead to wear of the silica layers and contact of the metal of the tube 23 with the metal ring of the fixing collar 26. This risks damaging the tube 23 or even piercing it.

[0017] There is a need to improve the means of fixing the tubes to the casing. Summary of the invention

[0018] The present disclosure provides a turbomachine assembly comprising cooling tubes extending circumferentially around a casing of the turbomachine, each cooling tube being fixed to the casing by at least one fixing collar,

[0019] in which for at least one fixing collar, an annular sleeve surrounds the cooling tube inserted in said fixing collar and is housed in said fixing collar,

[0020] characterized in that said sleeve is made of a material having a roughness Ra less than 1.6 and a thermal resistance up to a temperature of 350°C.

[0021] The sleeve protects the cooling tube from friction, particularly friction with the fixing collar. This reduces the risk of perforation of the tube and extends the life of the tube.

[0022] The casing may be annular, and may be the casing of a turbine of the turbomachine or of a fan of the turbomachine.

[0023] Each sleeve may extend circumferentially around the casing beyond the fixing collar receiving it on either side of said fixing collar. The circumferential dimension, around the casing, of the sleeve may be greater than the circumferential dimension, around the casing, of the fixing collar comprising said sleeve.

[0024] Thus, the roughness Ra can be applied to a surface of the sleeve in the circumferential direction greater than the width in the circumferential direction of the collar, allowing a reduction in friction forces.

[0025] Thus, the sleeve allows, in addition to absorbing friction due to vibrations, to place less stress on the cooling tube which will then be even less exposed to wear.

[0026] Each sleeve may comprise at least two retainers extending radially from a radially outer surface of said sleeve. The outer surface may be radially outer relative to the longitudinal axis of the cooling tube. The retainers may be arranged on either side of the fixing collar receiving said sleeve so that the fixing collar is locked between the two retainers. Thus, the retainers may form stops for the circumferentially outer edges, around the casing, of the fixing collar.

[0027] The retainers may bear against the casing or a tube support to which the fixing collars are fixed.

[0028] The tube support may be formed by a sheet metal fixed to the casing. The fixing collars may be screwed to said sheet metal. The sheet metal may extend along the axis of the casing. Several tube supports can be connected to the housing. Each cooling tube can be connected to one or more of said tube supports by the fixing clamps. The fixing clamps can be screwed to the tube support.

[0029] At least one sleeve may be made of a nickel-cobalt-based alloy, in particular a heat-resistant nickel-cobalt-based alloy.

[0030] The tube may be metallic and made of steel, in particular high-alloy steel.

[0031] Each fastening collar may comprise a metal retaining ring surrounded by a first protective layer and surrounding a second protective layer, the sleeve being surrounded by the second protective layer.

[0032] The metal retaining ring may be a metal tab that can be deformed to surround the tube.

[0033] The first protective layer and the second protective layer can be made of silica.

[0034] The first protective layer and the second protective layer may be bonded to either side of the metal retaining ring.

[0035] The tubes may comprise air ejection orifices directed towards the casing, i.e. opening radially inwards. The orifices may be regularly distributed over the entire circumference and may form one or more rows of orifices per tube.

[0036] The present document also relates to a turbomachine, for example an aircraft turbomachine, comprising an assembly as mentioned above.

[0037] The casing may be an annular turbine or fan casing of said turbomachine. Brief description of the figures

[0038] [Fig-1] [Fig.l], already described, is an axial sectional view of a turbojet engine with double flow,

[0039] [Fig.2] [Fig.2], already described, is an axial sectional view of part of the turbo reactor of [Fig.l] illustrating in particular the low pressure turbine,

[0040] [Fig.3] [Fig.3], already described, is a perspective view of cooling tubes surrounding a casing of the turbojet engine of figures 1 and 2,

[0041] [Fig.4] [Fig.4], already described, is a perspective view of a fixing collar according to the prior art of cooling tubes,

[0042] [Fig.5] [Fig.5] is a top view of an exemplary embodiment of a collar of fixing the cooling tubes of [Fig.3],

[0043] [Fig.6] [Fig.6] is a side view of the exemplary embodiment of the fixing collar of [Fig.5],

[0044] [Fig.7] [Fig.7] is a perspective view of the exemplary embodiment of the collar of fixing of [Fig.5]. Detailed description of the invention

[0045] Figures 5 to 7 illustrate an example of assembly of the cooling tubes 23 to the casing 18 of [Fig.3]. The cooling tubes 23 are held together on the casing 18 by means of supports 24, at different locations on the circumference of the casing 18. The cooling tubes 23 are fixed to the supports 24 by fixing collars 100 each comprising a deformable metal tab 108 and an external protective layer 106 arranged on the side of the external surface of the metal tab 108 and an internal protective layer 110 arranged on the side of the internal surface of the metal tab 108. The protective layers 108 and 110 are made of silica and are bonded respectively to the external and internal surface of the metal tab 108. Each support 24 may be formed by a sheet extending along the axis of the casing 18 and is fixed to the casing 18 at its axial ends along the axis of the casing 18.

[0046] The metal tab 108 is fixed by screws 102 to the support 24. The metal tab 108 can be folded to form a ring around the tube 23. The internal protective layer 110 is arranged opposite the tube 23.

[0047] To limit the friction experienced by the tube 23, a sleeve 104 is arranged around the tube and is surrounded by the fixing collar 100. The sleeve 104 is made of a material having a roughness Ra less than 1.6 and a thermal resistance up to a temperature of 350°C.

[0048] Such a material makes it possible to absorb friction due to vibrations, which protects the cooling tube 23.

[0049] The sleeve 104 is surrounded by the internal protective layer 110 of the fixing collar 100.

[0050] The sleeve 104 is equipped with two retainers 112 which extend from the radially external surface relative to the axis of the sleeve 104. The retainers are arranged on either side of the fixing collar 100 and make it possible to block the fixing collar 100 between the two retainers 112.

[0051] The sleeve 104 can be arranged centered relative to the fixing collar 100 along the circumference of the casing 18.

[0052] The sleeve 104 extends circumferentially around the casing 18 beyond the fixing collar 100 on either side of said fixing collar 100.

[0053] The circumferential dimension L1 of the sleeve 104 is greater than the circumferential dimension L2 of the fixing collar 100. For example, the circumferential dimension L1 of the sleeve 104 may be twice the circumferential dimension L2 of the fixing collar 100.

[0054] Each fixing collar 100 retaining the cooling tube 23 can be equipped with a sleeve 104.

Claims

Claims

1. A turbomachine assembly (1) comprising cooling tubes (23) extending circumferentially around a casing (18) of the turbomachine, each cooling tube (23) being fixed to the casing (18) by at least one fixing collar (100), wherein for at least one fixing collar, an annular sleeve (104) surrounds the cooling tube (23) inserted in said fixing collar and is housed in said fixing collar, characterized in that said sleeve (104) is made of a material having a roughness Ra less than 1.6 and a thermal resistance up to a temperature of 350°C.

2. An assembly according to claim 1, wherein each sleeve (104) extends circumferentially around the casing (18) beyond the fixing collar (100) receiving it on either side of said fixing collar.

3. An assembly according to claim 2, wherein each sleeve (104) comprises at least two retainers (112) extending radially from a radially outer surface of said sleeve (104), the retainers (112) being arranged on either side of the fixing collar (100) receiving said sleeve so that the fixing collar is locked between the two retainers (112).

4. Assembly according to one of the preceding claims, in which at least one sleeve (104) is made of an alloy based on nickel and cobalt.

5. An assembly according to any preceding claim, wherein each fixing collar (100) comprises a metal retaining ring (108) surrounded by a first protective layer (106) and surrounding a second protective layer (110), the sleeve (104) being surrounded by the second protective layer (110).

6. An assembly according to claim 5, wherein the first protective layer (106) and the second protective layer (110) are made of silica.

7. Turbomachine, for example of an aircraft, comprising an assembly according to one of the preceding claims.

Images