TURBOMACH FOR AN AIRCRAFT

Description

Technical field of the invention

[0001] The invention relates to the technical field of turbomachinery for aircraft. Technical background

[0002] An aircraft turbomachine typically extends along and around a longitudinal axis. Such turbomachines are disclosed, for example, in GB 2 578 522 A, US 11 220 929 B2, or FR 3 104 206 B1. It comprises a gas generator which typically includes, from upstream to downstream in the direction of gas flow within the turbomachine, a low-pressure compressor, a high-pressure compressor, a gas combustion chamber, a high-pressure turbine, and a low-pressure turbine.

[0003] The rotor of the low-pressure compressor is typically connected to the rotor of the low-pressure turbine via a low-pressure shaft. The rotor of the high-pressure compressor is connected to the rotor of the high-pressure turbine via a high-pressure shaft. The high-pressure shaft is generally arranged coaxially around the low-pressure shaft. The turbomachine also includes a blower located upstream of the gas generator, which is driven in rotation around its longitudinal axis by a blower shaft. The blower shaft may be connected to the low-pressure shaft via a speed reducer. The low-pressure shaft is guided in rotation by guide bearings, which must be lubricated for proper operation. Similarly, the speed reducer has gears and must also be lubricated for proper operation.It is therefore common practice to spray lubricating oil onto the guide bearings and into the gearbox. To protect the turbomachine's related components from this lubricating oil, the low-pressure shaft guide bearings are typically arranged in lubrication chambers. The guide bearings upstream of the turbomachine are located in an intermediate lubrication chamber, and the guide bearings downstream of the turbomachine are arranged in a downstream lubrication chamber. The gearbox itself may be arranged in an upstream lubrication chamber.

[0004] Lubrication chambers contain a pressurized mist of lubricating oil that must be contained to prevent oil leaks outside the chambers and to protect the associated turbomachine components. The chambers are generally delimited by rotor walls or elements and by stator walls or elements. During operation, it is therefore necessary to ensure a seal between the stator and rotor walls or elements.

[0005] This sealing is ensured by dynamic sealing joints mounted between the stator elements or walls and the rotor elements or walls which hermetically delimit the lubrication chambers.

[0006] To limit oil leaks outside the enclosure through these seals, it is necessary to adjust the pressures between the inside and outside of the lubrication chambers. To achieve this, pressurized air must be supplied to the seals. The air pressure outside the chamber must be higher than the pressure inside. The pressurized air outside the chamber will then naturally pass through the seals and enter the chamber, thus preventing oil leaks from the chamber to the outside through these seals.

[0007] In current technology, one solution for pressurizing the seals of the downstream lubrication chamber involves drawing air from the upstream stages of the high-pressure compressor and directing this air axially to the seals of this chamber. However, this solution is not entirely satisfactory because the air drawn from the upstream stages of the high-pressure compressor must pass through all the stages of the high-pressure compressor before reaching the downstream chamber. Consequently, the temperature of this air increases during its journey and reaches a high temperature by the time it arrives at the downstream lubrication chamber.

[0008] An excessively high temperature of the pressurized air in the downstream lubrication chamber is undesirable as it would promote coking of the lubricating oil in the downstream lubrication chamber.

[0009] In this context, there is a need to provide a turbomachine capable of ensuring the sealing of the downstream lubrication chamber while limiting the risk of coking of the lubricating oil within this chamber. Summary of the invention

[0010] To this end, the invention proposes a turbomachine for an aircraft, the turbomachine extending along a longitudinal axis and comprising: a low-pressure compressor comprising a compressor rotor, a low-pressure shaft for driving the compressor rotor, the low-pressure shaft being centered on the longitudinal axis and having an internal passage for the circulation of a first airflow along the longitudinal axis from upstream to downstream, the low-pressure shaft comprising: a first cylindrical section, a second section fixed in rotation to the first section and arranged upstream of the first section, the second section comprising a first frustoconical portion connected to the compressor rotor, an intermediate casing arranged around the first section and downstream of the low-pressure compressor, at least one bearing for guiding the rotation of the low-pressure shaft arranged radially between the first section and the intermediate casing, an annular intermediate lubrication chamber in which said at least one bearing is arranged,the intermediate lubrication chamber being arranged in the intermediate crankcase, an annular air chamber configured to be supplied with air from the low-pressure compressor, the air chamber being axially delimited, at least in part, by the first frustoconical portion and a radial separating wall mounted around the first portion, the first frustoconical portion further having at least one orifice communicating the air chamber with the internal passage to allow passage of the first airflow from the air chamber to the internal passage.

[0011] Thanks to the internal passage of the low-pressure shaft, the initial airflow from the upstream low-pressure compressor can be circulated downstream. This initial airflow can then be used to pressurize the downstream lubrication chamber. With this configuration, it is no longer necessary to pass through the high-pressure compressor stages. The temperature of this initial airflow is thus maintained at a suitable level to limit oil coking within the lubrication chamber.

[0012] Furthermore, according to the invention, the low-pressure shaft has first and second sections. The first section is intended to be connected to the low-pressure turbine, and the second section is connected to the low-pressure compressor. Thanks to the presence of a first cylindrical section connected to the low-pressure turbine and a second frustoconical section equipped with an orifice and connected to the low-pressure compressor, it is possible to ensure the entry of the first airflow into the internal passage without drilling through the first section. This makes it possible to meet the mechanical integration requirements of the low-pressure shaft connected to the low-pressure turbine without impacting the performance of the turbomachine. Indeed, drilling through the portion of the low-pressure shaft connected to the low-pressure turbine would require locally increasing the thickness of the low-pressure shaft at the drilling point to maintain sufficient mechanical strength.However, since the low-pressure shaft is designed to be positioned inside the high-pressure shaft, a localized increase in the thickness of the low-pressure shaft necessitates either increasing the diameter of the high-pressure shaft or reducing the clearances between the two shafts. The turbomachine's performance is then reduced in such a configuration. The invention overcomes this drawback. Furthermore, by eliminating the need for a bore on the first section, it is not necessary to provide dynamic seals (e.g., labyrinth seals) between this first section and the high-pressure shaft to limit leakage through this bore. This reduces the number of seals in this area and thus improves the overall reliability.

[0013] The invention may include one or more of the following features, taken individually or in combination with each other: The air enclosure is externally delimited, at least in part, by a first axial wall extending axially upstream from the separating wall and a second axial wall connected to the first frustoconical portion and extending axially downstream, the first and second walls axially delimiting between them an air inlet to allow passage of the first airflow from the low-pressure compressor into the air enclosure, a fixed annular air cavity arranged around the air enclosure, the air cavity opening into the air enclosure and being supplied by air from the low-pressure compressor, the air cavity is axially delimited, at least in part, by a dynamic seal located radially between the first axial wall and the intermediate casing, and a dynamic seal located radially between the second axial wall and the intermediate casing,an axially arranged drainage cavity between the intermediate lubrication chamber and the air cavity, the drainage cavity is axially delimited by the dynamic seal located radially between the first axial wall and the intermediate housing, and a dynamic seal located radially between the first axial wall and the intermediate housing and separating the drainage cavity from the intermediate lubrication chamber, a high-pressure compressor arranged downstream of the intermediate housing and comprising a compressor rotor, a high-pressure shaft arranged coaxially around the first section of the low-pressure shaft and connected to the compressor rotor, the first section and the high-pressure shaft defining an annular space for the circulation of a second airflow from downstream to upstream,the high-pressure shaft comprising a radial orifice opening into the annular space for the passage of the second airflow from the outside to the inside of the annular space, a sleeve arranged around the first section and inside the intermediate casing, the sleeve being integral with the separating wall and axially delimiting with an upstream end of the high-pressure shaft an opening for the passage of the second airflow from the annular space to the intermediate lubrication chamber, a blower movable in rotation about the longitudinal axis and arranged upstream of the low-pressure compressor, a blower shaft connected to the blower, a speed reducer connecting the blower shaft to the low-pressure shaft, the speed reducer being arranged in an upstream lubrication chamber,and the second section comprising a radial wall extending outwards from the first frustoconical portion and connecting the first frustoconical portion to the compressor rotor, the radial wall having an axial opening for the passage of air from the air chamber to the upstream lubrication chamber, a speed reducer connecting the blower shaft to the low-pressure shaft, the speed reducer being arranged in an upstream lubrication chamber, the second section comprising a second frustoconical portion connected to the speed reducer and to the first frustoconical portion, the second frustoconical portion having an opening into the internal passage for the passage of air from the air chamber to the upstream lubrication chamber. Brief description of the figures

[0014] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which: there figure 1 is a schematic longitudinal cross-sectional view of half a turbomachine according to the invention; the figure 2 is a detailed longitudinal cross-sectional view of part of the turbomachine half of the figure 1 ; there figure 3 is a longitudinal cross-sectional view of a first embodiment of the invention; the figure 4 is a longitudinal cross-sectional view of an alternative embodiment of the figure 3 ; there figure 5 is a longitudinal cross-sectional view of another embodiment of the figure 3 ; there figure 6 is a longitudinal cross-sectional view of another embodiment of the figure 3 . Detailed description of the invention

[0015] An example of an aircraft turbomachine 1 according to the invention is shown very briefly on the figure 1 . Turbomachine 1 is, for example, a turbofan engine.

[0016] Turbomachine 1 extends along a longitudinal axis X. A gas flow F flows into turbomachine 1.

[0017] For the purposes of the present invention, the terms "upstream" and "downstream" are understood in relation to the direction of flow of the gas flow F in the turbomachine 1.

[0018] Furthermore, the terms "longitudinal," "longitudinally," "radial," and "radially" refer to the distance from the longitudinal axis X of the turbomachine. The terms "external" and "internal" refer to the distance from the longitudinal axis X along a radial axis perpendicular to the longitudinal axis X.

[0019] The turbomachine 1 comprises, from upstream to downstream, a blower 2 and a gas generator. The gas generator comprises, from upstream to downstream, 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.

[0020] The turbomachine 1 further includes an intermediate casing 10, arranged axially downstream of the low-pressure compressor 3, between the low-pressure compressor 3 and the high-pressure compressor 4. The intermediate casing 10 includes, for example, an inner shell and an outer shell which are centered on the longitudinal axis X. The inner and outer shells are, for example, connected by arms.

[0021] The turbomachine 1 may further include an inlet casing 11. The inlet casing 11 is arranged axially between the fan 2 and the low-pressure compressor 3. The inlet casing 11 includes, for example, an inner shell and an outer shell which are centered on the longitudinal axis X. The inner and outer shells are, for example, connected by arms.

[0022] The turbomachine 1 may further include an inter-turbine casing 12. The inter-turbine casing 12 is arranged axially between the high-pressure turbine 6 and the low-pressure turbine 7.

[0023] Each compressor 3,4 comprises a compressor rotor 3a, 4a and each turbine 6, 7 comprises a turbine rotor 6a, 7a. The compressor rotors 3a, 4a and the turbine rotors 6a, 7a are composed of a plurality of stages, each comprising a bladed wheel.

[0024] The compressor rotor 3a of the low pressure compressor 3 is connected to the turbine rotor 7a of the low pressure turbine 7 by a low pressure shaft 8. They form a low pressure body.

[0025] The compressor rotor 4a of the high-pressure compressor 4 is connected to the turbine rotor 6a of the high-pressure turbine 6 by a high-pressure shaft 9. They form a high-pressure body.

[0026] The low pressure shaft 8 and high pressure shaft 9 are centered on the longitudinal axis X and are free to rotate around the longitudinal axis X. The high pressure shaft 9 is arranged coaxially around the low pressure shaft 8.

[0027] The gas flow F passes through the blower 2 and splits into a primary air flow F1, which flows through a primary channel, and a secondary air flow F2, which flows through a secondary channel surrounding the primary channel. The primary channel is delimited, at least partially, by the inner and outer shells. The primary air flow F1 passes through the low-pressure compressor 3 and the high-pressure compressor 4. The compressed primary air flow F1 then passes through the combustion chamber 5, where it is mixed with fuel. The combustion gases thus pass through the high-pressure turbine 6 and the low-pressure turbine 7. The energy of the gases is transformed by the turbine rotor 7a of the low-pressure turbine 7 into mechanical energy, which drives the low-pressure shaft 8 and, consequently, the low-pressure compressor 3.

[0028] The blower 2 comprises a disc 2b that rotates about the longitudinal axis X and blades 2a evenly distributed on the disc 2b. The disc 2b can be connected upstream to an inlet cone 2c and downstream to a rear ring 2d. One end of the rear ring 2d is mounted inside the inlet housing 11. A sealing element 2e is mounted radially between the rear ring 2d and the inlet housing 11. The sealing element 2e is, for example, a dynamic seal such as a labyrinth seal. It includes flaps carried by the rear ring 2d that cooperate with the inner housing 11.

[0029] The disk 2b is driven in rotation by a blower shaft 13. Advantageously, the blower shaft 13 is connected to the low-pressure shaft 8 via a speed reducer 14. The speed reducer 14 is of the mechanical type. It is, for example, an epicyclic or planetary gear train. The speed reducer 14 conventionally comprises a sun gear 14a and a ring gear 14b centered on the longitudinal axis X. It also includes satellite gears 14c meshing with the sun gear 14a and the ring gear 14b. Furthermore, it includes a satellite carrier 14d.

[0030] The solar element 14a is rotationally fixed to the low-pressure shaft 8 and forms the input of the speed reducer 14, while either of the ring gear 14b and the planet carrier 14d, depending on the configuration of the reducer 14, is rotationally fixed to the fan shaft 13 and forms the output of the speed reducer 14. In an epicyclic gear train configuration (not shown), the ring gear 14b is fixed, therefore fixed to a fixed part of the turbomachine such as the inlet housing 11, and the planet carrier 14d is rotationally mobile, therefore fixed to the fan shaft 13. In a planetary gear train configuration as illustrated in the figure 1 , the ring 14b is mobile in rotation and therefore fixed to the blower shaft 13, and the planet carrier 14d is fixed and therefore fixed to a fixed part of the turbomachine such as the inlet casing 11.

[0031] The speed reducer 14 allows the blower shaft 13 to be driven at a rotational speed lower than the rotational speed of the low-pressure shaft 8. This allows the dilution ratio of the turbomachine 1 to be increased.

[0032] As more clearly seen on the figure 2 or the figure 3 The low-pressure shaft 8 according to the invention has an internal passage 18 for the circulation of a first air flow A1 along the longitudinal axis X. In particular, the first air flow A1 circulates in the internal passage 18 from upstream to downstream along the longitudinal axis X. The first air flow A1 comes from the low-pressure compressor 3.

[0033] The low-pressure shaft 8 further comprises, from downstream to upstream, a first section 8a, for example, connected to the turbine rotor 7a of the low-pressure turbine 7, a second section 8b connected to the compressor rotor 3a of the low-pressure compressor 3, and optionally a third section 8c, for example, connected to the speed reducer 14. The low-pressure shaft 8 is preferably made of at least two interconnected and rotationally fixed sections. In particular, the first and second sections 8a and 8b may be connected to each other in a detachable manner to allow the assembly of the high-pressure housing around the low-pressure housing of the turbomachine 1.

[0034] The first, second, and third sections 8a, 8b, 8c are hollow for the passage of the first airflow A1 and each define a section of the internal passage 18.

[0035] The first section 8a is cylindrical. However, the first section 8a may, for example, exhibit variations in its cross-section in the longitudinal direction. The downstream end of the first section 8a is connected to the turbine rotor 7a of the low-pressure turbine 7, and the opposite upstream end is connected to the second section 8b.

[0036] According to the invention, the low-pressure shaft 8 comprises a radial separating wall 80a mounted around the first section 8a. The separating wall 80a is rotationally fixed to the first section 8a. The separating wall 80a is, for example, arranged inside the intermediate housing 10. The separating wall 80a carries a first axial wall 81a extending axially upstream from the separating wall 80a.

[0037] Advantageously, the low-pressure shaft 8 further comprises a sleeve 82a arranged around the first section 8a and inside the intermediate housing 10. The sleeve 82a is rotationally fixed to the first section 8a. The sleeve 82a is mounted around the first section 8a and connected to it by a splined connection, for example. The sleeve 82a is arranged downstream of the separating wall 80a and connected to the separating wall 80a. The sleeve 82a and the separating wall 80a can form a single piece mounted around the first section 8a by means of the splined connection, for example. Advantageously, the sleeve 82a is cylindrical.

[0038] The second section 8b is rotationally fixed to the first section 8a and is connected to it by a mechanical link, for example, a splined joint. It comprises a first frustoconical portion 8b' and possibly a second frustoconical portion 8b'.

[0039] The first frustoconical portion 8b' is flared upstream. According to the invention, the first frustoconical portion 8b' has an orifice 19. The orifice 19 opens to the outside and inside of the first frustoconical portion 8b'. The orifice 19 thus opens into the internal passage 18. The orifice 19 has a radial axis.

[0040] As depicted on the figure 2 The second section 8b may further comprise a first cylindrical portion 8b1 attached to the first frustoconical portion 8b'. The second section 8b is connected to the upstream end of the first section 8a via the first cylindrical portion 8b1, which may, for example, be grooved for this purpose. The upstream end of the first section 8a is open. It opens into the second section 8b, and in particular into the first cylindrical portion 8b1 or the first frustoconical portion 8b'.

[0041] The second frustoconical section 8b" is flared downstream. It is integral with the first frustoconical section 8b'. Each frustoconical section 8b', 8b" has an annular radial surface centered on the longitudinal axis X, the junction of the two radial surfaces forming an annular rim. The second frustoconical section 8b" is also connected to the third section 8c.

[0042] Furthermore, advantageously, the second section 8b comprises a radial wall 80b extending radially outwards from the first frustoconical portion 8b' and, in particular, from the annular rim. The radial wall 80b connects the first frustoconical portion 8b' to the compressor rotor 3a of the low-pressure compressor 3. A second axial wall 81b is connected to the first frustoconical portion 8b'. More specifically, the second axial wall 81b is supported by the radial wall 80b and extends axially downstream from this radial wall 80b.

[0043] The second truncated conical section 8b" is, for example, attached to the downstream end of the third section 8c.

[0044] As depicted on the figure 2The second section 8b further comprises a second cylindrical portion 8b2 integral with the second frustoconical portion 8b. The second section 8b is fixed to the downstream end of the third section 8c via the second cylindrical portion 8b2. The second cylindrical portion 8b2 is, for example, fixed inside the downstream end of the third section 8c by means of splines. The third section 8c is advantageously arranged inside the inlet housing 11. The third section 8c has a cylindrical body 80c' extending between the upstream and downstream ends of the third section 8c. The third section 8c is connected to the solar element 14a of the speed reducer 14. More specifically, the upstream end of the third section 8c is connected to the solar element 14a.Advantageously, the third section 8c includes a support wall 80c extending radially outwards from the cylindrical body 80c' and in particular from the downstream end of the cylindrical body 80c'.

[0045] Furthermore, the high-pressure shaft 9 is advantageously arranged coaxially around the first portion 8a of the low-pressure shaft 8 and together they define an annular space 22 for the circulation of a second airflow A2 from downstream to upstream.

[0046] The high-pressure shaft 9 comprises, for example, a cylindrical body 9b and a frustoconical skirt 9c extending radially outwards from the cylindrical body 9b. The frustoconical skirt 9c is connected to the compressor rotor 4a of the high-pressure compressor 4. The frustoconical skirt 9c has a bore 9d.

[0047] The high-pressure shaft 9 also includes a radial orifice 23. The radial orifice 23 opens both inside and outside the high-pressure shaft 9. It thus opens into the annular space 22. By "radial orifice," it is understood that the axis of the orifice extends radially with respect to the longitudinal axis X. The radial orifice 23 is provided on the cylindrical body 9b. For example, it is provided downstream of the frustoconical skirt 9c.

[0048] Furthermore, the high-pressure shaft 9 is more specifically arranged downstream of the sleeve 82a. The high-pressure shaft 9 axially defines with the sleeve 82a an opening 22a leading into the annular space 22.

[0049] The low and high pressure shafts 8, 9 of the turbomachine 1 are guided in rotation by bearings. The bearings are, for example, rolling bearings such as rollers or balls.

[0050] As illustrated on the figures 3 to 6The blower shaft 13 is guided in rotation by a first guide bearing 20a. The first bearing 20a is arranged radially between the blower shaft 13 and the inlet housing 11. The first bearing 20a comprises, for example, a bearing arranged between an outer ring and an inner ring. The outer ring is supported by a first bearing support 21a extending radially inward from the inlet housing 11. The inner ring is supported by the blower shaft 13. The bearing is, for example, a single row of balls. Advantageously, the bearing comprises two rows of balls.

[0051] The low-pressure shaft 8 is guided in rotation by a second and a third bearing 20b, 20c. The second bearing 20b is arranged radially between the input housing 11 and the low-pressure shaft 8, specifically the third section 8c. The second bearing 20b comprises, for example, a bearing arranged between an outer ring and an inner ring. The outer ring is, for example, supported by a second bearing support 21b extending radially inward from the input housing 11. The inner ring is, for example, supported by the third section 8c. The bearing is, for example, a row of rollers. The third bearing 20c is arranged radially between the intermediate housing 10 and the first section 8a. With reference, for example, to the figure 2The third bearing 20c comprises a bearing, for example a row of balls, arranged radially between an inner ring and an outer ring. The outer ring is supported by a third bearing support 21c connected to the intermediate housing 10. The inner ring is supported by a third axial wall 81c extending axially downstream from the separating wall 80a.

[0052] The high-pressure shaft 9 is guided in rotation by a fourth bearing 20d. The fourth bearing 20d is, for example, arranged radially between the high-pressure shaft 9 and the intermediate housing 10. The fourth bearing 20d comprises a bearing, for example, a row of balls and a row of rollers arranged radially between an outer ring and an inner ring. The inner ring is supported by the high-pressure shaft 9, and in particular by the cylindrical body 9b, and the outer ring is supported by a fourth bearing support 21d connected to the intermediate housing 10.

[0053] As depicted on the figure 1 , the low pressure shaft 8 can be guided in rotation downstream by a fifth bearing 20e arranged radially between a downstream end of the low pressure shaft 8 and the inter-turbine housing 12 for example.

[0054] Bearings 20a, 20b, 20c, 20d, 20e, and the speed reducer 14 must be lubricated with oil to ensure their proper operation. To prevent oil contamination of the associated components of the turbomachine 1, bearings 20a, 20b, 20c, 20d, 20e, and the speed reducer 14 are arranged in lubrication chambers.

[0055] For this purpose, the turbomachine 1 further comprises an upstream lubrication chamber 15 in which the first and second bearings 20a, 20b and the speed reducer 14 are arranged, an intermediate lubrication chamber 16 in which the third and fourth bearings 20c, 20d are arranged, a downstream lubrication chamber 17 in which the fifth bearing 20e is arranged.

[0056] The lubrication chambers 15, 16, 17 are annular.

[0057] The upstream lubrication chamber 15 is arranged for example inside the inlet housing 11 and in particular inside the inner ferrule.

[0058] The intermediate lubrication chamber 16 is arranged inside the intermediate housing 10. It is internally delimited at least in part by the low pressure shaft 8, in particular the sleeve 82a, and by the high pressure shaft 9.

[0059] The downstream lubrication chamber 17 is arranged for example inside the inter-turbine casing 12.

[0060] Each lubrication chamber 15, 16, 17 is supplied with oil by at least one lubrication circuit (not shown). Inside each lubrication chamber 15, 16, 17, a pressurized oil mist exists. To limit oil leakage outside the chambers 15, 16, 17, dynamic seals such as labyrinth seals are arranged at the axial ends of the chambers 15, 16, 17. A dynamic seal is understood as an assembly that limits fluid leakage between a stationary part and a rotating part.

[0061] With reference to figures 3 to 6The upstream enclosure 15 is axially delimited by a first dynamic seal 24a, for example a labyrinth seal, and a second dynamic seal 24b, for example a labyrinth seal. The first seal 24a delimits the upstream end of the upstream enclosure 15, and the second seal 24b delimits the downstream end of the upstream enclosure 15. The first seal 24a is arranged upstream of the first bearing 20a. It comprises an outer ring carried by the first bearing support 21a and an inner ring carried by the blower shaft 13. The inner ring is lined with flanges that cooperate with the outer ring. The second seal 24b is arranged downstream of the second bearing 20b. It comprises an outer ring carried by the second bearing support 21b and an inner ring carried by the low-pressure shaft 8, in particular the third section 8c and especially the radial support wall 80c. The inner ring is coated with ridges that cooperate with the outer ring.

[0062] The intermediate housing 16 is axially delimited by a third dynamic seal 24c, for example a labyrinth seal, and a fourth dynamic seal 24d, for example a labyrinth seal. The third seal 24c delimits the upstream end of the intermediate housing 16, and the fourth seal 24d delimits the downstream end of the intermediate housing 16. The third seal 24c is arranged upstream of the third bearing 20c. It comprises an outer ring carried by the third bearing support 21c and an inner ring carried by the low-pressure shaft 8, and in particular by the first section 8a, specifically by the first axial wall 81a. The inner ring may be fitted with flanges that cooperate with the outer ring. The fourth seal 24d is arranged downstream of the fourth bearing 20d. More precisely, the fourth seal 24d is arranged axially between the radial port 23 and the fourth bearing 20d.It comprises an outer ring carried by a first radial arm 21e extending radially inwards from the intermediate housing 10 and an inner ring carried by the high-pressure shaft 9. The inner ring may be coated with scuffs cooperating with the outer ring.

[0063] Opening 22a leads into the intermediate lubrication chamber 16. To prevent oil leakage from the intermediate lubrication chamber 16 into the annular space 22 through opening 22a, a first dynamic seal 24g and a second dynamic seal 24h are arranged axially on either side of opening 22a. The first seal 24g is located radially between the intermediate housing 10 and an upstream end of the high-pressure shaft 9, and the second dynamic seal 24h is located radially between the first section 8a and the intermediate housing 10. The fourth bearing 20d is arranged axially between the fourth seal 24d and the first seal 24g. The first seal 24g is a labyrinth seal. It includes an outer sealing ring 21f connected to the intermediate housing 10 and an inner ring carried by the upstream end of the high-pressure shaft 9.The outer ring 21f is arranged around the opening 22a. The inner ring is lined with grooves that cooperate with the outer ring 21f. The second sealing element 24h comprises an inner ring carried by the first section 8a and, in particular, the sleeve 82a. The inner ring is lined with grooves that cooperate with the outer sealing ring 21f. The outer ring 21f is arranged around the opening 22a.

[0064] The turbomachine 1 further comprises an air chamber 25, axially delimited at least partially by the first frustoconical section 8b' and the separating wall 80a. The separating wall 80a thus advantageously separates the intermediate lubrication chamber 16 and the air chamber 25. The air chamber 25 is also externally delimited at least partially by the first axial wall 81a and the second axial wall 81b. The air chamber 25 is arranged radially between the first and second axial walls 81a, 81b and the first section 8a.

[0065] The air enclosure 25 further includes an air inlet 25a. The air inlet 25a is delimited or defined between the first axial wall 81a and the second axial wall 81b. The air enclosure 25 is therefore rotatable.

[0066] The air chamber 25 is supplied with air from the low-pressure compressor 3. According to the present invention, the air chamber 25 can be supplied directly or indirectly by air from the low-pressure compressor 3. By directly, it is meant that the air from the low-pressure compressor 3 is directly communicated to the air chamber 25, while by indirectly, it is meant that the air from the low-pressure compressor 3 is communicated to an intermediate component which in turn supplies the air chamber 25.

[0067] The air enclosure 25 communicates with the internal passage 18 through the orifice 19, which allows the passage of the first airflow A1 from the air enclosure 25 to the internal passage 18.

[0068] Advantageously, the turbomachine 1 further comprises an air cavity 26 arranged around the air chamber 25. The air cavity 26 is fixed against rotation about the longitudinal axis X. The air cavity 26 is arranged inside the third bearing support 21c. It is axially delimited by a fifth dynamic seal 24e, for example a labyrinth seal, and a sixth dynamic seal 24f, for example a labyrinth seal. The fifth seal 24e comprises an outer ring carried by the third bearing support 21c and an inner ring carried by the second axial wall 81b. The inner ring is lined with flaps that cooperate with the outer ring. The sixth seal 24f comprises an outer ring carried by the third bearing support 21c and an inner ring carried by the first axial wall 81a. The air cavity 26 opens into the air chamber 25 via the air inlet 25a.The third bearing support 21c can advantageously carry a tube (not shown) opening into the air cavity 26. The tube allows air to be conveyed from the low pressure compressor 3 to the inside of the air cavity 26.

[0069] The air cavity 26 is thus supplied with air drawn from the low-pressure compressor 3, and the air chamber 25 is supplied with air from the low-pressure compressor 3 via the air cavity 26. The air cavity 26 homogenizes the air pressure around the third seal 24c, thereby improving the sealing of the intermediate lubrication chamber 16. Slight oil leaks from the intermediate lubrication chamber may occur. For this purpose, advantageously, the turbomachine 1 further includes a drain cavity 27 arranged axially between the air cavity 26 and the intermediate lubrication chamber 16. The drain cavity 27 is axially delimited by the sixth seal 24f and the third seal 24c. The third seal thus axially separates the drain cavity 27 from the intermediate lubrication chamber 16.The drainage cavity 27 is arranged inside the third bearing support 21c and internally delimited by the low pressure shaft 8, and in particular the first section 8a, especially the first axial wall 81a.

[0070] The drainage cavity 27 allows for the storage of oil leaks from the intermediate lubrication chamber 16 and the evacuation of this oil outside the drainage chamber 27. The drainage cavity 27 thus prevents oil leaks into the air chamber 25.

[0071] The turbomachine 1 may include additional drainage cavities 27a at the terminals of the upstream lubrication chamber 15.

[0072] The turbomachine 1 further includes a drainage circuit comprising a first drainage conduit (not shown) which allows the recovery of oil from the drainage cavity 27 and the evacuation of this oil (not shown) to an oil receptacle 28 or to the outside of the turbomachine 1. The oil receptacle 28 is for example arranged in an inter-vein compartment arranged between the primary and secondary veins, or in the lower part of a nacelle of the turbomachine 1.

[0073] The turbomachine 1 further includes a pressurization circuit C1. The pressurization circuit C1 includes an air sampling device (not shown) configured to draw air from the low-pressure compressor 3, and in particular downstream of the low-pressure compressor 3. By "downstream of the compressor" it is understood that the air is drawn from the last stages of the low-pressure compressor 3, that is to say the stages located downstream of a middle stage located at an intermediate distance between the first and last stages of the low-pressure compressor 3.

[0074] The pressurization circuit C1 includes the first airflow A1. The first airflow A1 pressurizes the downstream chamber 17. The first airflow A1 is drawn in by the sampling device. The first airflow A1 is directed to the air chamber 25 via the air cavity 26 and flows through the internal passage 18 via the orifice 19. The first airflow A1 flows from upstream to downstream in the internal passage 18 until it reaches the downstream lubrication chamber 17.

[0075] According to an embodiment shown in the figures 3 And 4The pressurization circuit C1 includes an additional airflow At drawn by the sampling device. The pressurization circuit C1 advantageously comprises a conduit having an inlet connected to the sampling device and an outlet opening upstream of the high-pressure compressor 4. The conduit advantageously passes through one of the arms of the intermediate housing 10. The additional airflow At is routed through the conduit and directed radially towards the cylindrical section 9b via the bore 9d. It then splits into a second airflow A2 for pressurizing the first and second sealing devices 24g, 24h, and a third airflow A3 for cooling the compressor rotor 4a of the high-pressure compressor 4.

[0076] The second airflow A2 passes through the radial orifice 23 and is directed into the annular space 22. It flows from downstream to upstream in the annular space 22 to the intermediate sealing chamber 16 through the opening 22a.

[0077] The third airflow A3 circulates around the high-pressure shaft 9 from upstream to downstream and allows cooling of the compressor rotor 4a of the high-pressure compressor 4.

[0078] Alternatively, for cooling the high-pressure compressor 4 and pressurizing the first and second sealing elements 24g, 24h, with reference to Figures 5 And 6 The turbomachine 1 advantageously includes a cooling circuit L1. The cooling circuit L1 includes an air intake device (not shown) configured to take air from the high-pressure compressor 4, in particular upstream of the high-pressure compressor 4.

[0079] The cooling circuit L1 includes the additional airflow At taken by the air intake device of the high-pressure compressor 4. The additional airflow At is divided into a second airflow A2 and a third airflow A3.

[0080] The second airflow A2 is directed into the annular space 22 through the radial orifice 23 and flows upstream within the annular space 22 to the intermediate sealing chamber 16 via the opening 22a for pressurizing the first and second sealing elements 24g, 24h. The third airflow A3 flows around the high-pressure shaft 9 from upstream to downstream and provides cooling for the rotor of the high-pressure compressor 4a.

[0081] Furthermore, with reference to the figure 3The pressurization circuit C1 includes a fourth air flow A4 for pressurizing the upstream lubrication chamber 15. The fourth air flow A4 is taken by the sampling device in the low-pressure compressor 3. The pressurization circuit C1 advantageously includes a conduit having an inlet connected to the sampling device and an outlet opening into the inlet housing 11. The conduit advantageously passes through one of the arms of the inlet housing 11. The air flow A4 is divided into an upstream flow A4' for pressurizing the first seal 24a and a downstream flow A4" for pressurizing the second seal 24b.

[0082] Alternatively, with reference to the figure 4An axial hole 29 is provided in the radial wall 80b and is configured to conduct axially a portion A1' of the first airflow A1 from the air chamber 25 to the upstream lubrication chamber 15. The portion A1' of the first airflow A1 allows the pressurization of the second seal 24b. Alternatively, the hole 29 is provided in the second frustoconical portion 8b.

[0083] According to yet another alternative shown on the figure 5 The portion A1' of the first airflow A1 also allows the pressurization of the first seal 24a. For this purpose, the pressurization circuit C1 includes a conduit arranged in the internal ferrule of the inlet housing 11 and which opens into the inside of the inlet housing 11. A portion A1" of the portion A1' of the first airflow A1 is directed into the conduit and allows the pressurization of the first seal 24a.

[0084] This embodiment is particularly advantageous since no duct passes through the inlet casing arms. The inlet casing arms can therefore be sized to minimize disturbance to the primary flow F1. The aerodynamic performance of the turbomachine 1 is thus improved. Indeed, when the duct is arranged in at least one arm, it may be necessary to adapt the arm's dimensions to accommodate such a duct, which then negatively impacts the turbomachine's aerodynamic performance.

[0085] According to yet another alternative, it represents on the figure 6 , the second truncated conical portion 8b" has a hole 30 which is configured to conduct part A1' of the first airflow A1 from the air chamber 25 to the upstream lubrication chamber 15. Part A1' of the first airflow A1 allows the pressurization of the second seal 24b.

[0086] According to this alternative, the portion A1' of the first airflow A1 also allows the pressurization of the first seal 24a. For this purpose, the pressurization circuit C1 includes a conduit arranged in the internal ferrule of the inlet housing 11. A portion A1" of the portion A1' of the first airflow A1 is directed into the conduit and allows the pressurization of the first seal 24a.

[0087] Thus, thanks to the internal passage 18 of the low-pressure shaft, it is possible to circulate the first air flow A1 taken from the low-pressure compressor 3 to the downstream lubrication chamber 17, thus making it possible to maintain an adequate temperature of the pressurization air of this downstream lubrication chamber to avoid coking of the oil.

[0088] Furthermore, thanks to the presence of a first cylindrical section 8a connected to the low-pressure turbine 7 and a second frustoconical section 8b equipped with the orifice 19 and connected to the low-pressure compressor 3, it is possible to ensure the entry of the first air flow A1 into the internal passage 18 without piercing the first section 8a. This makes it possible to meet the mechanical integration requirements of the low-pressure shaft 8 in the turbomachine.

[0089] Furthermore, by eliminating the need for drilling on the first section, it is not necessary to provide dynamic seals between this first section and the high-pressure shaft to limit leaks through this drilling.

Claims

1. A turbomachine (1) for an aircraft, the turbomachine (1) extending along a longitudinal axis (X) and comprising: - a low-pressure compressor (3) comprising a compressor rotor (3a), - a low-pressure shaft (8) for driving the compressor rotor (3a), the low-pressure shaft (8) being centered on the longitudinal axis (X), characterized in that the low-pressure shaft (8) has an internal passage (18) configured for the circulation of a first air stream (A1) along the longitudinal axis (X) from upstream to downstream, the low-pressure shaft (8) comprising: - a first cylindrical segment (8a), - a second segment (8b) secured in rotation to the first segment (8a) and arranged upstream of the first segment (8a), the second segment (8b) comprising a first frustoconical portion (8b') connected to the compressor rotor (3a), the turbomachine (1) comprising: - an intermediate casing (10) arranged around the first segment (8a) and downstream of the low-pressure compressor (3), - at least one bearing (20c) for guiding the low-pressure shaft (8) in rotation, arranged radially between the first segment (8a) and the intermediate casing (10), - an annular intermediate lubrication chamber (16) wherein said at least one bearing (20c) is arranged, the intermediate lubrication chamber (16) being arranged in the intermediate casing (10), - an annular air chamber (25) configured to be supplied with air from the low-pressure compressor (3), the air chamber (25) being delimited axially, at least in part, by the first frustoconical portion (8b') and a radial separating wall (80a) mounted around the first segment (8a), the first frustoconical portion (8b') also having at least one opening (19) putting the air chamber (25) into communication with the internal passage (18) to allow the first air stream (A1) to pass from the air chamber (25) to the internal passage (18).

2. The turbomachine according to the preceding claim, characterized in that the air chamber (25) is delimited externally, at least in part, by a first axial wall (81a) extending axially upstream from the separating wall (80a) and a second axial wall (81b) connected to the first frustoconical portion (8b') and extending axially downstream, the first and second walls (81a, 81b) axially delimiting between them an air inlet (25a) to allow the first air stream (A1) to pass from the low-pressure compressor (3) inside the air chamber (25).

3. The turbomachine according to any one of the preceding claims, characterized in that it further comprises a stationary annular air cavity (26) arranged around the air chamber (25), the air cavity (26) opening into the air chamber (25) and being supplied with air from the low-pressure compressor (3).

4. The turbomachine according to claims 2 and 3, characterized in that the air cavity (26) is delimited axially, at least in part, by a dynamic seal (24f) housed radially between the first axial wall (81a) and the intermediate casing (10), and a dynamic seal (24e) housed radially between the second axial wall (81b) and the intermediate casing (10).

5. The turbomachine according to one of claims 3 or 4, characterized in that it comprises a drainage cavity (27) arranged axially between the intermediate lubrication chamber (16) and the air cavity (26).

6. The turbomachine according to claims 4 and 5, characterized in that the drainage cavity (27) is delimited axially by the dynamic seal (24f) housed radially between the first axial wall (81a) and the intermediate casing (10), and a dynamic seal (24c) housed radially between the first axial wall (81a) and the intermediate casing (10) and separating the drainage cavity (27) from the intermediate lubrication chamber (16).

7. The turbomachine according to any one of the preceding claims, characterized in that it further comprises: - a high-pressure compressor (4) arranged downstream of the intermediate casing (10) and comprising a compressor rotor (4a), - a high-pressure shaft (9) arranged coaxially around the first segment (8a) of the low-pressure shaft (8) and connected to the compressor rotor (4a), the first segment (8a) and the high-pressure shaft (9) delimiting an annular space (22) for the circulation of a second air stream (A2) from downstream to upstream, and in that the high-pressure shaft (9) comprises a radial opening (23) opening into the annular space (22) for the passage of the second air stream (A2) from the outside to the inside of the annular space (22).

8. The turbomachine according to the preceding claim, characterized in that it comprises a sleeve (82a) arranged around the first segment (8a) and inside the intermediate casing (10), the sleeve (82a) being secured to the separating wall (80a) and axially delimiting, with an upstream end of the high-pressure shaft (9), an aperture (22a) for the passage of the second air stream (A2) from the annular space (22) to the intermediate lubrication chamber (16).

9. The turbomachine according to any one of the preceding claims, characterized in that it further comprises: - a fan (2) movable in rotation about the longitudinal axis (X) and arranged upstream of the low-pressure compressor (3), - a fan shaft (13) connected to the fan (2), - a speed reducer (14) connecting the fan shaft (13) to the low-pressure shaft (8), the speed reducer (14) being arranged in an upstream lubrication chamber (15), and in that the second segment (8b) comprises a radial wall (80b) extending outwards from the first frustoconical portion (8b') and connecting the first frustoconical portion (8b') to the compressor rotor (3a), the radial wall (80b) having an axial hole (29) for the passage of air (A1') from the air chamber (25) to the upstream lubrication chamber (15).

10. The turbomachine according to any one of claims 1 to 8, characterized in that it further comprises: - a fan (2) movable in rotation about the longitudinal axis and is arranged upstream of the low-pressure compressor (3), - a fan shaft (13) connected to the fan (2), - a speed reducer (14) connecting the fan shaft (13) to the low-pressure shaft (8), the speed reducer (14) being arranged in an upstream lubrication chamber (15), and in that the second segment (8b) comprises a second frustoconical portion (8b") connected to the speed reducer (14) and to the first frustoconical portion (8b'), the second frustoconical portion (8b") having a hole (30) opening into the internal passage (18) for the passage of air (A1') from the air chamber (26) to the upstream lubrication chamber (15).