Turbine with contra-rotating turbines for an aircraft

Abstract

A turbine (10) with a contra-rotating turbine for an aircraft, the turbine comprising a contra-rotating turbine (22) and a mechanical reduction gear (42) having a planetary epicyclic gear train, the mechanical reduction gear comprising a planet carrier (46) which is fixed to the stator housing (26) of the turbine, the stator housing being located upstream of the contra-rotating turbine with respect to the flow direction of the gas within the turbine, characterized in that the planet carrier is fixed to the stator housing by an annular member (50) having an elongated shape which extends inside a second shaft, the member comprising an upstream end fixed to an intermediate housing and a downstream end coupled to the planet carrier, and the member comprising an integrated circuit (78, 80, 82) for conveying lubricating oil from the upstream end of the member to the planet carrier.

Description

Technical field

[0001] The present invention relates to a turbine for an aircraft having a contra-rotating turbine. Background art

[0002] The background art particularly includes the documents FR-A1-3 013 325, FR-A1-2 955 085, FR-A1-2 998 867, US 2019 / 085722 A1 and FR 28 742 38 A1.

[0003] Generally, a turbine of an aircraft includes, in the flow direction of the gas, from upstream to downstream, a fan, a low-pressure compressor, a high-pressure compressor, an annular combustion chamber, a high-pressure turbine and a low-pressure turbine. The rotor of the low-pressure compressor is driven by the rotor of the low-pressure turbine, and the rotor of the high-pressure compressor is driven by the rotor of the high-pressure turbine.

[0004] From the perspective of engine performance and fuel consumption, it is advantageous to maximize the rotational speed of the low-pressure turbine, because this results in higher efficiency of the turbine. However, increasing the rotational speed of the turbine means increasing the centrifugal force to which the turbine is subjected, thus making the design of the turbine very complex.

[0005] One proposal for increasing the efficiency of the turbine without increasing its rotational speed is to use a contra-rotating turbine. Then, the low-pressure turbine is replaced by a dual-rotor turbine having a first rotor and a second rotor, the first rotor being configured to rotate in a first rotational direction and connected to a first turbine shaft, and the second rotor being configured to rotate in a opposite rotational direction and connected to a second turbine shaft. The turbine wheel part included in the first rotor is inserted between the turbine wheel parts of the second rotor.

[0006] In a conventional architecture in which the turbine directly drives the fan, the low-pressure turbine can have a take-off rotational speed of about 4,000 rpm, or (in an architecture in which the turbine drives the fan through a reduction gear) the low-pressure turbine can have a take-off rotational speed of about 10,000 rpm. Replacing the above-mentioned low-pressure turbine with a contra-rotating turbine whose rotors rotate at take-off speeds of about 3,000 revolutions per minute and about 7,000 revolutions per minute respectively makes it possible to have a relative speed of 10,000 (3,000 + 7,000) revolutions per minute, while having an absolute speed in a low range within the above speed range.

[0007] This contra-rotating turbine includes a low-speed rotor and a high-speed rotor, the low-speed rotor driving the fan, and the high-speed rotor meshing with a mechanical reduction gear having a planetary epicyclic gear train, the input and output of which are contra-rotating (rotating ring gear, fixed planet carrier, rotating sun gear).

[0008] The reduction gear couples the high-speed rotor and the low-speed rotor, thus enabling power to be transferred from the high-speed rotor to the low-speed rotor. The higher efficiency of the high-speed turbine is achieved by transferring most of the power from the turbine to the fan, not through the reduction gear but through the shaft.

[0009] Due to the mechanical integration of this architecture, the architecture is complex: the mechanical reduction gear is located downstream of the turbine and radially inside the stator housing (referred to as the exhaust housing).

[0010] The positioning of the reduction gear involves arranging a number of bearings and oil collection housings inside the exhaust housing. In addition, the reduction gear is located in a relatively hot area, which requires a thermal solution. Therefore, the space inside the exhaust housing is particularly constrained, which means that the integration of the reduction gear must be carried out as much as possible and the implementation radius of the reduction gear must be reduced.

[0011] To optimize the operation and service life of the reduction gear, it is important to absorb the torque borne by the planet carrier of the reduction gear during operation. In addition, delivering lubricating oil to the reduction gear is essential for the operation of the reduction gear and is complex to implement in such a constrained environment. Summary of the Invention

[0012] The present invention proposes an improvement to the above technology, which represents a simple, effective and economical solution to at least some of the above problems.

[0013] The present invention proposes a turbine for an aircraft having a contra-rotating turbine,

[0014] The turbine includes a contra-rotating turbine, the first rotor of the contra-rotating turbine is configured to rotate in a first rotational direction and is connected to a first turbine shaft, the second rotor of the contra-rotating turbine is configured to rotate in a reverse rotational direction and is connected to a second turbine shaft, and the first rotor includes a turbine wheel portion that is inserted between the turbine wheel portions of the second rotor,

[0015] The turbine further includes a mechanical reduction gear having a planetary epicyclic gear train, the mechanical reduction gear including: a sun gear driven to rotate by the second shaft; a ring gear driven to rotate by the first shaft; and a planet carrier attached to the stator housing of the turbine, the stator housing being located upstream of the contra-rotating turbine with respect to the flow direction of the gas in the turbine,

[0016] Characterized in that the planet carrier is attached to the stator housing by an annular member having an elongated shape extending inside the second shaft, the member including an upstream end attached to an intermediate housing and a downstream end coupled to the planet carrier, and the member including an integrated circuit for delivering lubricating oil from the upstream end of the member to the planet carrier.

[0017] The component for connecting the stator housing to the planet carrier has a dual function. The component is coupled to the planet carrier and by this coupling has a first function: to absorb the torque forces transmitted to the planet carrier during operation. These forces are transmitted by the component to the stator housing. The component also includes a function for delivering lubricating oil to the reduction gear, in particular to the planet carrier of the reduction gear.

[0018] The turbine according to the invention may comprise one or more of the following features, which are taken independently of each other or in combination with each other:

[0019] - The component is integral.

[0020] - The component includes a frustoconical section and a cylindrical section, the frustoconical section extending between the upstream end and the cylindrical section, and the cylindrical section extending between the frustoconical section and the spline for coupling to the planet carrier.

[0021] - The circuit includes an internal annular cavity at the junction between the frustoconical section and the cylindrical section.

[0022] - The circuit includes an oil inlet duct formed in a boss or an additional thickness of the frustoconical section, the oil inlet duct extending upstream from the annular cavity to a hole located on the upstream face of the component and upstream of the spline.

[0023] - The circuit includes an oil outlet duct formed in a boss or an additional thickness of the cylindrical section, the oil outlet duct extending downstream from the annular cavity to a hole located on the outer cylindrical surface at the downstream end.

[0024] - The cylindrical surface is located between two annular grooves for receiving an annular seal.

[0025] - The cross-section of at least some of the ducts is elliptical.

[0026] - The spline is separated from the rest of the component by a circumferential weld.

[0027] - The cross-section of the planet carrier is generally L-shaped, and the planet carrier includes a radial section for supporting the shafts of the planet gears and a cylindrical section for coupling to the component. The planet carrier also includes an integrated circuit for delivering oil from the component, and

[0028] - The turbine is of the type with a single shrouded fan.

[0029] The invention also relates to a method for manufacturing the annular component described herein, the method comprising the following steps:

[0030] a) The upstream part of the component is produced by additive manufacturing, and the upstream part includes an upstream end for attachment to the stator housing and at least partially includes an integrated lubricating oil delivery circuit;

[0031] b) The downstream part of the component is produced by forging, and the downstream part includes a downstream end for connection to the planet carrier;

[0032] c) The thus-produced upstream part and downstream part are welded together.

[0033] Advantageously, the production of the upstream part includes producing a cylindrical section and a frustoconical section by additive manufacturing, as well as the upstream end of the component.

[0034] Preferably, the downstream part of the component includes a spline made of forged material for connection to the planet carrier. Description of the Drawings

[0035] In the following description made by way of non-limiting examples and with reference to the drawings, the present invention will be better understood, and other details, features and advantages of the present invention will become clearer. In the drawings:

[0036] - Figure 1 is a very schematic axial cross-sectional view of a turbine with a contra-rotating turbine,

[0037] - Figure 2 is Figure 1 an enlarged view of the contra-rotating turbine of

[0038] - Figure 3 is a partial schematic axial cross-section of a component for connecting the planet carrier of a speed reduction device to the stator housing of a turbine according to the present invention,

[0039] - Figure 4 is a schematic perspective view of the component seen from the downstream side of Figure 3 in

[0040] - Figure 5 is Figure 3 a schematic perspective cross-sectional view of the component in Figure 3 which is taken at the level of the V-V line in

[0041] - Figure 6 is Figure 3 a schematic perspective cross-sectional view of the component in Figure 3 which is taken at the level of the VI-VI line in

[0042] - Figure 7 is Figure 3 a schematic partial perspective view of a part of the component in

[0043] - Figure 8 is Figure 3 a schematic partial axial cross-sectional view of a component in and of the planet carrier of a reduction gear. DETAILED DESCRIPTION

[0044] Figure 1 There is shown a very schematic illustration of a turbine 10 with contra-rotating turbines for an aircraft.

[0045] The turbine 10 includes, in the flow direction of the gas, from upstream to downstream, a fan 12, a low-pressure compressor 14, a high-pressure compressor 16, an annular combustion chamber 18, a high-pressure turbine 20, and a contra-rotating turbine 22.

[0046] Reference numeral 24 denotes an intermediate housing located between the compressors 14 and 16. Reference numeral 26 denotes a turbine housing (a turbine housing of the TVF type, TVF being an abbreviation for Turbine Vane Frame, a turbine housing of the turbine vane frame type denoting a turbine housing equipped with arms forming stator vanes) located between the turbines 20 and 22. Finally, reference numeral 28 denotes an exhaust housing (an exhaust housing of the TRF type, TRF being an abbreviation for Turbine Rear Frame, an exhaust housing of the turbine rear frame type denoting the last turbine housing). These housings form the structure of the turbine: these housings support bearings that guide the rotation of the shaft and are linked to the suspension of the turbine.

[0047] The rotor of the high-pressure turbine 20 drives the rotor of the high-pressure compressor 16 to rotate via a high-pressure shaft 30, which is centered and guided in rotation by bearings (such as an upstream ball bearing 32 and a downstream roller bearing 34). The bearing 32 is mounted between the upstream end of the shaft 30 and the intermediate housing 24, and the bearing 34 is mounted between the downstream end of the shaft 30 and the turbine housing 26.

[0048] The contra-rotating turbine 22 includes a first rotor 22a and a second rotor 22b. The first rotor has a wheel portion 22aa, which is configured to rotate in a first rotational direction and is connected to a first turbine shaft 36. The second rotor has a wheel portion 22ba, which is configured to rotate in the opposite rotational direction and is connected to a second turbine shaft 38. The wheel portion 22ba of the rotor 22b is inserted between the wheel portions 22aa of the rotor 22a (see Figure 2 ).

[0049] Each turbine wheel portion includes an annular row of blades, and each of the blades includes an aerodynamic profile that includes an inner arc surface and an outer arc surface, and the inner arc surface and the outer arc surface meet to form a leading edge and a trailing edge of the gas in the turbine duct.

[0050] The first shaft 36 drives the rotation of the fan 12 and the rotor of the low-pressure compressor 14. In addition, the first shaft 36 meshes with the ring gear 40 of a mechanical reduction gear 42 having a planetary epicyclic gear train.

[0051] The second shaft 38 meshes with the sun gear 44 or the planet gears (planétaire) of the reduction gear 42.

[0052] The reduction gear 42 also includes planet gears 41 that respectively mesh with the sun gear 44 and the ring gear 40 and are carried by a planet carrier 46 attached to the turbine housing 26.

[0053] Each of the housings 26 and 28 generally includes: a central hub portion; and an outer ring portion that surrounds the hub portion and is connected to the hub portion by a series of arms that are substantially radial with respect to the longitudinal axis of the turbine and that pass through the turbine duct. The central hub portion of the housing 28 extends around at least a portion of the reduction gear 42.

[0054] In the example shown, the high-pressure shaft 30 is centered and guided in rotation by two upstream ball bearings 32 and roller bearings 33 and a downstream roller bearing 34. The bearings 32, 33 are mounted between the upstream end of the shaft 30 and the intermediate housing 24, and the bearing 34 is mounted between the downstream end of the shaft 30 and the turbine housing 26.

[0055] As described above, the downstream end of the second shaft 38 meshes with the sun gear and is also connected to the last or downstream stage of the second rotor 22b, i.e., to the last wheel portion 22ba1 of the rotor.

[0056] The second shaft 38 is centered and guided in rotation on the turbine housing by two guide bearings, namely an upstream guide bearing 56 and a downstream guide bearing 58, respectively.

[0057] The downstream end of the first shaft 36 is attached to the ring gear 40 of the reduction gear, and the upstream end of the first shaft is attached to the last or downstream stage of the first rotor 22a, i.e., to the last wheel portion of the rotor. The ring gear 40 is also attached to the upstream end of a ring gear carrier 40a, and the downstream end of the ring gear carrier is attached to or meshes with the downstream end of the shaft 36.

[0058] The planet carrier 46 can here include an annular section with a C-shaped or S-shaped cross-section on the downstream side of the reduction gear 42, in order to impart a certain flexibility to the planet carrier, in particular in the radial direction and in an inclination, by elastic deformation (flexibility about an axis perpendicular to the motor axis). Due to this flexibility provided by the planet carrier 46, the ring gear carrier 40a of the reduction gear 42 can be rigid. Under certain conditions, the opposite can be the case. In this case, the ring gear carrier 40a would be flexible or would be imparted flexibility, and the planet carrier 46 would be rigid. Then, the ring gear carrier 40a would include an annular forging with a C-shaped or S-shaped cross-section, in order to impart a certain flexibility to the ring gear, in particular in the radial direction and in an inclination, by elastic deformation (flexibility about an axis perpendicular to the motor axis). In this second configuration, advantageously, the flexibility is integrated outside the force path from the downstream end of the ring gear carrier 40a to the bearing 60.

[0059] The shaft 36 is guided upstream by bearings 52, 54 mounted between this shaft and the intermediate housing 24. The first of these bearings is, for example, the upstream roller bearing 52, and the second of these bearings is, for example, the downstream ball bearing 54.

[0060] The shaft 36 is also centered and guided in rotation downstream by two guide bearings (the upstream guide bearing 60 and the downstream guide bearing 62 respectively), which are supported by the exhaust housing 28. Advantageously, these bearings are arranged on both sides of the reduction gear 42.

[0061] Figure 3 And the following shows an embodiment of the component 50 for connecting the planet carrier 46 to the housing 26.

[0062] In the example shown, the component 50 is integral and has a generally elongated, annular and in particular tubular shape.

[0063] The component extends around the longitudinal axis of the turbine and can be inserted between the shafts 38 and 36, as Figure 2 shown.

[0064] The upstream end of the component 50 ( Figure 3 the left side) is attached to the housing 26 and includes an annular attachment flange 70 fixed, for example, by screws or bolts.

[0065] The downstream end of the component 50 (the right side) is intended to be coupled to the planet carrier 46 and for this purpose includes straight splines 72 (here male splines). These splines 72 are intended to engage with complementary splines 73 (and thus female splines) of the planet carrier 46 by axial translation.

[0066] Component 50 essentially comprises two sections or segments 74, 76 between the ends of the component. The first upstream segment 74 is frustoconical and flares out upstream. The second segment 76 is cylindrical. The first segment 74 extends between the flange 70 and the second segment 76. The second segment 76 extends between the first segment 74 and the spline 72.

[0067] At the junction between the first segment 74 and the second segment 76, the component 50 may include an annular oil flow cavity 78. The cavity 78 is integrated in the component 50 and may be located in an annular additional thickness of the component.

[0068] The cavity 78 is connected on the one hand to an oil inlet pipe 80 and on the other hand to an oil outlet pipe 82. The cavity 78 has the function of distributing the oil from the pipe 80 and evenly distributing this oil in the pipe 82.

[0069] There are 4 pipes 80 and these pipes are regularly distributed around the axis of rotation of the component 50. The pipes 80 are also integrated in the component and are formed in a local additional thickness on the downstream frustoconical surface of the first segment 74. The pipes 80 have a downstream end and an upstream end, the downstream end leading into the cavity 78 and the upstream end leading axially upstream to the upstream radial surface of the segment 74 or the upstream end of the component 50.

[0070] The number of pipes 82 is greater than the number of pipes 80. The pipes 82 are evenly distributed around the axis of rotation of the component 50. The pipes 82 are also integrated in the component 50 and are formed in a longitudinal additional thickness on the outer surface of the segment 76. The pipes 82 have an upstream end and a downstream end, the upstream end leading into the cavity 78 and the downstream end leading radially to the outer cylindrical surface 84 of the second segment 76.

[0071] This surface 84 extends between two annular bosses which include annular grooves 86 for receiving annular seals. These seals are configured to cooperate with a part of the planet carrier 46, as Figure 3 and Figure 8 shown. An annular oil receiving space 88 is defined between the surface 84 and a part of the planet carrier 46 and enables oil to flow from the integrated circuit in the component 50 to the integrated oil circuit in the planet carrier 46. Thus, the planet carrier 46 includes a hole 90 which leads radially inwards to the space 88 and communicates with an oil pipe 92 integrated in the planet carrier 46, which oil pipe is used for example to convey oil to the shaft 94 of the planet gear 41.

[0072] Figure 6 and Figure 7 Enabling the pipes 82 to advantageously have an elliptical cross-section with a minimum diameter in the radial direction to limit the overall radial dimensions of the component while maximizing the pipe cross-section.

[0073] The number of pipes 80, 82 and the cross-sectional area of the passage of the pipes are determined to be able to pass the amount of oil required to lubricate and cool the reduction gear. There can be various pipe shapes from circular to oval. However, since the part 50 is subject to torsional stress, an oval pipe is preferred, so that the concentration of stress (contraintes) at the level of the part is considerably limited, and thus an optimal design in terms of mass and overall dimensions is obtained.

[0074] Moreover, such an integral part can only be easily manufactured by additive manufacturing. However, the mechanical properties of additive manufacturing are generally not as good as those of forged materials. The significant forces transmitted through this part do not allow the spline 72 to be made of a material manufactured by additive manufacturing downstream.

[0075] To overcome this problem, the part 50 is preferably manufactured in two parts: the upstream part is made by additive manufacturing and has integrated pipes 80, 82. The upstream part includes an upstream end for attachment to the stator housing and at least partially includes an integrated lubricating oil delivery circuit, in particular the integrated pipes 80, 82. Thus, advantageously, the upstream part includes a frustoconical section 74 and a cylindrical section 76. Then, the downstream part of the part is made by forging, and the downstream part includes a downstream end connected to the planet carrier. In particular, the downstream part with the spline 72 is made of a forged material with better mechanical properties. These two parts will be connected together by welding, and the welding is carried out between the spline 72 and the surface 84. Figure 3 and Figure 7 The reference numeral 96 in represents the circumferential weld of these two parts.

[0076] Using the spline 72 to transmit torque also makes it possible to ensure easier disassembly of the reduction gear and reduce the overall dimensions of the upstream oil housing. A flange would be more bulky and would thus limit the possibility of integrating the shaft 64.

[0077] The oil passage is formed upstream of the spline 72 through a transition region defined by the space 88 between the planet carrier 46 and the part 50 (see Figure 3 ). The seal carried by the part 50 ensures the sealing of this region and the good transmission of oil at the joint between the two elements.

[0078] The cavity 78 enables the oil reaching through the pipe 80 to distribute this oil in the pipes 82 (here 12 pipes). Using a larger number of pipes 82 allows minimizing the total radial dimensions of these pipes and thus optimizing the integration of the part 50 into the turbine.

[0079] Thus, the present invention offers several advantages:

[0080] - The present invention enables the reduction gear to be lubricated through the planet carrier 46,

[0081] - The pipes 80, 82 having an oval cross-section enable oil to be transported through the components stressed during operation, as the components are subjected to the forces transmitted by the reduction gear.

[0082] - The component 50, although complex, can be easily made at least in part by additive manufacturing.

[0083] - The spline 72, which is a location of high stress concentration, is made by forging, thus having good mechanical properties.

Claims

1. A turbine (10) for an aircraft, having a contra-rotating turbine, The turbine includes a contra-rotating turbine (22), a first rotor (22a) of the contra-rotating turbine is configured to rotate in a first rotational direction and is connected to a first turbine shaft (36), a second rotor (22b) of the contra-rotating turbine is configured to rotate in an opposite rotational direction and is connected to a second turbine shaft (38), and the first rotor includes a turbine wheel portion which is inserted between the turbine wheel portions of the second rotor. The turbine further includes a mechanical reduction gear (42) having a planetary gear train, and the mechanical reduction gear includes: A sun gear (44) that is driven to rotate by the second turbine shaft (38); A ring gear (40) that is driven to rotate by the first turbine shaft (36); And a planet carrier (46) that is attached to the stator housing (26) of the turbine, the stator housing being located upstream of the contra-rotating turbine with respect to the flow direction of the gas in the turbine, Characterized in that the planet carrier is attached to the stator housing by an annular member (50) having an elongated shape that extends inside the second turbine shaft, the annular member including an upstream end attached to an intermediate housing and a downstream end coupled to the planet carrier, and the annular member including an integrated circuit for conveying lubricating oil from the upstream end of the annular member to the planet carrier.

2. The turbine (10) according to claim 1, wherein, The annular member (50) is integral.

3. The turbine (10) according to claim 1 or 2, wherein, The annular member (50) includes a frustoconical section (74) and a cylindrical section (76), the frustoconical section extending between the upstream end and the cylindrical section, and the cylindrical section extending between the frustoconical section and a spline (72) for coupling to the planet carrier (46).

4. The turbine (10) according to claim 3, wherein, The integrated circuit includes an internal annular cavity (78) at the junction between the frustoconical section (74) and the cylindrical section (76).

5. The turbine (10) according to claim 4, wherein, The integrated circuit includes an oil inlet duct (80) formed in the additional thickness of the frustoconical section (74), the oil inlet duct extending upstream from the internal annular cavity (78) to a hole in the upstream face located at the upstream end.

6. The turbine (10) according to claim 4 or 5, wherein, The integrated circuit includes an oil outlet duct (82) formed in the additional thickness of the cylindrical section (76), the oil outlet duct extending downstream from the internal annular cavity (78) to a hole located on the outer cylindrical surface (84) of the annular member, upstream of the spline (72).

7. The turbine (10) according to claim 6, wherein, The outer cylindrical surface (84) is located between two annular grooves (86) for receiving an annular seal.

8. The turbine (10) according to claim 5, wherein, The integrated circuit includes an oil outlet duct (82) formed in the additional thickness of the cylindrical section (76), the oil outlet duct extending downstream from the internal annular cavity (78) to a hole located on the outer cylindrical surface (84) of the annular member, upstream of the spline (72), wherein at least some of the ducts of the oil inlet duct (80) and the oil outlet duct (82) have an elliptical cross-section.

9. The turbine (10) according to claim 3, wherein, The spline (72) is separated from the remainder of the annular member (50) by an annular weld (96).

10. The turbine (10) according to claim 1 or 2, wherein, The mechanical reduction gear (42) further includes a planetary gear (41), the cross-section of the planet carrier (46) is generally L-shaped, and the planet carrier includes a radial section for supporting a shaft (94) of the planetary gear (41) and a cylindrical section for coupling to the annular member (50), and the planet carrier further includes an integrated circuit for conveying oil from the annular member.

11. The turbine (10) according to claim 1 or 2, wherein, The turbine is of the type having a single shrouded fan.

12. The turbine (10) according to claim 5, wherein, The oil inlet pipe is formed in a boss of the frustoconical section (74).

13. The turbine (10) according to claim 6, wherein, The oil outlet pipe is formed in a boss of the cylindrical section (76).

14. A method for manufacturing an annular component (50) for attaching a planet carrier (46) to a stator housing (26) of a turbine according to any one of claims 1 to 13, the method comprising the following steps: a) producing an upstream portion of the annular component by additive manufacturing, the upstream portion including an upstream end for attachment to the stator housing and at least partially including an integrated lubricating oil delivery circuit; b) producing a downstream portion of the annular component by forging, the downstream portion including a downstream end for connection to the planet carrier; c) welding the upstream portion and the downstream portion together.

15. According to the method of claim 14, wherein, The downstream portion of the annular component includes a spline (72) for connection to the planet carrier (46), and the upstream portion of the annular component (50) includes a frustoconical section (74) and a cylindrical section (76), the frustoconical section extending between the upstream end and the cylindrical section, and the cylindrical section extending between the frustoconical section and the spline (72) of the downstream portion.

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