Propulsion assembly for the rear of an aircraft fuselage

Abstract

Propulsion assembly for the rear fuselage of an aircraft, comprising: - a turbofan engine (2) having a main axis (X), the turbofan engine comprising a high-pressure casing and a low-pressure casing including a low-pressure shaft (11) mounted to rotate freely about the main axis, - a nacelle receiving the turbofan engine (2), - a support mast (14) for the turbofan engine attached to the turbofan engine on one side and intended to be attached to the rear fuselage on the other, and - an electric machine (15) comprising at least one stator (22) integral with the turbofan engine, disposed externally to the nacelle, on a side opposite the mast relative to the main axis, and at least one rotor (23) driven in rotation by the low-pressure shaft about an axis of rotation (X') forming an angle (β) less than or equal to 15° with the main axis (X). Figure to be published with the abbreviation: 3

Description

Title of the invention: Propulsion assembly for the rear of an aircraft fuselage Technical field of the invention

[0001] The invention relates to a propulsion assembly for the rear of an aircraft fuselage. including an electric machine. State of the prior art

[0002] [Fig.l] is a cross-sectional view of a propulsion unit 1 comprising a turbomachine 2 and a nacelle 3 radially surrounding the turbomachine 2.

[0003] The propulsion unit 1 can be configured for installation at the rear of the fuselage, that is to say that it is connected to the rear of the fuselage of an aircraft by a transverse mast, or pylon, which carries the turbomachine and the nacelle and integrates the electrical and fluid connections.

[0004] An aircraft may comprise two such propulsion units, located on either side of the rear of the fuselage. Such a configuration is generally preferred for small aircraft intended for business aviation.

[0005] The turbomachine 2 extends along a main axis X and comprises, in a known manner, from upstream to downstream, a fan 4, a low-pressure compressor 5, a high-pressure compressor 6, a combustion chamber 7, a high-pressure turbine 8 and a low-pressure turbine 9.

[0006] The high-pressure compressor 6 and the high-pressure turbine 8 are connected to each other by a high-pressure shaft 10 and form, with the combustion chamber 7, a high-pressure body.

[0007] The blower 4, the low pressure compressor 5 and the low pressure turbine 8 are connected to each other by a low pressure shaft 11 coaxial with the high pressure shaft 10, and together form a low pressure body.

[0008] The low and high pressure compressors 5, 6, the combustion chamber 7 and the high and low pressure turbines 8, 9 are located in a primary vein 12, or internal vein. A secondary vein 13, or external vein, extends around the primary vein 12, downstream of the fan 4, inside the nacelle 3.

[0009] The terms axial, radial and circumferential are defined relative to the main axis X of the turbomachine 2. The terms upstream and downstream are defined relative to the direction of circulation of the gases within the turbomachine 2.

[0010] In order to be able to be fixed indifferently on one side or the other of the rear of the fuselage, a rear fuselage turbomachine comprises, as standard, members for fixing to the mast on two opposite sides of the turbomachine 2.

[0011] In the context of the hybridization of aircraft engines, which aims both to improve their operability and to reduce their environmental impact, it is desirable to install on aircraft electrical machines mechanically coupled to the turbomachines, in particular to the low pressure shaft which is coupled in rotation with the fan.

[0012] These electrical machines are adapted to operate as an electrical generator during phases where the required thrust is low, making it possible to redirect surplus energy for use by secondary functions or for storage in on-board batteries. The electrical machines are also adapted to provide, in electric motor mode, surplus mechanical energy to the turbomachine for a relatively short time, for example when additional thrust is particularly beneficial, such as during takeoff of the aircraft.

[0013] However, the integration of an electrical machine and mechanical connections with the low-pressure shaft in the confined space of a turbomachine and the nacelle receiving it is particularly complex. This problem is even more pronounced for small engines, such as rear fuselage engines intended for small aircraft. Finally, it is desirable to reduce as much as possible the number of modifications to be made to the turbomachine, in order to avoid significant design costs and possible losses in efficiency of the turbomachine. Presentation of the invention

[0014] The invention aims to remedy these drawbacks by proposing a method of integrating an electric machine into a propulsion unit of reduced size requiring few modifications to the propulsion unit.

[0015] To this end, the invention relates to a propulsion assembly for the rear of an aircraft fuselage, comprising:

[0016] - a double-flow turbomachine having a main axis, the turbomachine comprising a high pressure body and a low pressure body comprising a low pressure shaft mounted to rotate about the main axis,

[0017] - a nacelle receiving the turbomachine, substantially symmetrical around the axis main,

[0018] - a turbomachine support mast fixed to the turbomachine on the one hand and intended to be fixed to the rear of the fuselage on the other hand, and

[0019] - an electrical machine comprising at least one stator integral with the turbomachine, arranged externally to the nacelle, on one side opposite the mast relative to the main axis, and at least one rotor driven in rotation by the low pressure shaft around an axis of rotation forming an angle less than or equal to 15° with the main axis.

[0020] Such a propulsion unit makes it possible to combine an electric machine with a turbomachine while benefiting from a robust fixing and reduced bulk.

[0021] The rotor may be driven by the low pressure shaft through a transverse shaft extending substantially perpendicular to the main axis and through a first set of bevel gears meshing the low pressure shaft and the transverse shaft and a second set of bevel gears meshing the transverse shaft and the rotor.

[0022] Such a characteristic makes it possible to mechanically associate the rotor shaft of the electric machine and the low pressure shaft of the turbomachine by a double angle transmission drive system, which makes it possible to arrange the electric machine in a stable configuration and generating low aerodynamic drag.

[0023] The first set of bevel gears may be connected to a downstream end of the low pressure shaft.

[0024] Such a feature makes it possible to reduce the bulk associated with the mechanical transmission in the cluttered space of the turbomachine.

[0025] At least one of the first set of bevel gears and the second set of bevel gears may comprise two bevel gears of different diameters, such that the rotor of the electric machine has a speed greater than the speed of the low pressure shaft.

[0026] Such a characteristic makes it possible to have a higher rotation speed of the electric machine and therefore to reduce the diameter of the electric machine for the same electric power, thus reducing the aerodynamic drag.

[0027] The axis of rotation of the rotor of the electric machine may be substantially parallel to the main axis of the turbomachine.

[0028] Such a feature makes it possible to improve the stability of the transmission by having two angle reports at 90° each time.

[0029] The axis of rotation of the rotor of the electric machine may form an angle of less than 90° with the transverse shaft.

[0030] Such a characteristic makes it possible to position the electric machine as close as possible to the curved external surface of the nacelle and thus to reduce its aerodynamic drag and the lever arm of the suspension.

[0031] The turbomachine may comprise means for fixing to the mast provided on two opposite sides of the turbomachine on either side of the main axis, the electric machine being fixed to the turbomachine by the fixing means located on the side opposite the means for fixing the turbomachine to the mast.

[0032] Such a feature makes it possible to use the fixing means already provided on the turbomachine and unused, on the side opposite the mast, to fix the electric machine in a rigid and robust manner.

[0033] The electric machine can be fixed to the turbomachine by fixing means which comprise a cradle, said cradle comprising a U-shaped support member, provided with two branches between which the electric machine is arranged.

[0034] Such a characteristic makes it possible to improve the stability of the electric machine and thus to maintain the transmission in position despite the vibrations generated by the turbomachine.

[0035] The means for fixing the electric machine to the turbomachine may be rigid.

[0036] Such a characteristic makes it possible to maintain contact between the different parts of the transmission even during phases of significant vibrations or shocks.

[0037] The invention also relates to an aircraft comprising a fuselage and at least two propulsion units as above, fixed to a rear of said fuselage by substantially horizontal masts. Brief description of the figures

[0038] [Fig-1] is a cross-sectional view of a turbomachine,

[0039] [Fig.2] is a top view of a propulsion unit according to the invention fixed to the rear of the fuselage of an aircraft,

[0040] [Fig.3] is a schematic view of a transmission of the propulsion unit of [Fig.2],

[0041] [Fig.4] is a perspective view of a fixing member of an electrical machine of the propulsion unit of figures 2 and 3, and

[0042] [Fig.5] is a schematic view of a second embodiment of a propulsion assembly according to the invention. Detailed description of the invention

[0043] A propulsion unit 1 according to the invention is shown in [Fig.2].

[0044] The propulsion unit 1 comprises a turbomachine 2 and a nacelle 3, as well as a mast 14 supporting the turbomachine 2 and an electric machine 15 fixed to the turbomachine 2.

[0045] The turbomachine 2 is a double-flow turbomachine having a main axis X, and is substantially identical to that of [Fig.l].

[0046] The nacelle 3 extends in a substantially cylindrical manner around the main axis X and receives and houses the turbomachine 2 in its internal space.

[0047] The mast 14 extends substantially perpendicular to the main axis X of the turbomachine 2.

[0048] The mast 14 is fixed to the turbomachine 2 by a first end 16 and to a rear fuselage 17 of an aircraft 18 by its second end 19.

[0049] The rear fuselage 17 is a portion of the aircraft fuselage 18 extending behind the wings, to the rear end of the fuselage.

[0050] The turbomachine 2 comprises first fixing members 20 and second fixing members 21, arranged diametrically opposite on either side of the axis main X.

[0051] The first fixing members 20 are fixed to the first end 16 of the mast 14, with fixing members implementing a flexible suspension. Such a suspension is adapted to dampen vibrations and reduce their transmission from the turbomachine 2 to the fuselage.

[0052] The electrical machine 15, shown in more detail in [Fig. 3], comprises a stator 22 and a rotor 23 mounted on a rotor shaft 24 movable in rotation relative to the stator 22 around an axis of rotation X' of the electrical machine 15.

[0053] In the embodiment shown in Figures 2 and 3, the axis of rotation X' is substantially parallel to the main axis X of the turbomachine 2.

[0054] The stator 22 and the rotor 23 are arranged in a substantially cylindrical main casing 25 fixed to the turbomachine 2 by suspension means 26. The stator 22 is secured to the main casing 25, while the rotor shaft 24 carrying the rotor 23 is mounted on rotation bearings secured to the main casing 25.

[0055] The propulsion assembly 1 further comprises a transverse shaft 27 extending along a transverse axis Y and movable in rotation around this transverse axis Y.

[0056] The transverse axis Y extends perpendicular to the main axis X of the turbomachine 2 and can, as in the case shown in [Fig.3], extend perpendicular to the axis of rotation X'.

[0057] The transverse shaft 27 is arranged to transmit a rotational torque between the low pressure shaft 11 and the rotor shaft 24.

[0058] To do this, a first set of bevel gears 28 meshes with the low pressure shaft 11 and the transverse shaft 27, and a second set of bevel gears meshes with the transverse shaft 27 and the rotor shaft 24.

[0059] Advantageously, the first set of bevel gears is mechanically connected to the low pressure shaft 11 in the vicinity of a downstream end 30 thereof.

[0060] The second set of bevel gears 29 is arranged in a transmission casing 31 secured to the main casing 25 and arranged downstream of the latter.

[0061] The first set of bevel gears 28 and the second set of bevel gears 29 may have ratios of the radii between the two gears which compose them both equal to 1. In this case, the rotation speeds of the low pressure shaft 11 and the rotor shaft 24, or regimes, are equal.

[0062] Alternatively, at least one of the sets of bevel gears 28, 29 may have a ratio between the radii of the gears other than 1, with in particular the gear located on the side of the rotor shaft 24 smaller than the gear located on the side of the low pressure shaft 11.

[0063] The operating speed of the electric machine 15 is then higher than that of the low pressure shaft, which makes it possible to reduce the diameter of the machine. 15 electric for equivalent electric power, and thus reduce aerodynamic drag and suspended mass.

[0064] The suspension means 26 are adapted to fix the electric machine 15 to the turbomachine 2 and comprise for example an upstream fixing 32 and a downstream fixing 33.

[0065] The suspension means 26 are for example integral with the main casing 25 at one end and fixed to the second fixing members 21 of the turbomachine 2, on the side opposite the mast 14 relative to the main axis X.

[0066] The fixing means 26 implement a rigid suspension of the electric machine 15 to the turbomachine 2, so as to maintain the mechanical drive between the rotor shaft 24 and the low pressure shaft 11.

[0067] The fixing means 26 are shown in detail in [Fig. 4], which shows a front suspension 34 forming part of the second fixing means 21, as well as the upstream fixing 32 and the downstream fixing 33.

[0068] The fixing means 26 further comprise a cradle 35 comprising a connection structure 36, a U-shaped support member 37 and a holding stud 38.

[0069] The connection structure 36 is integral with the upstream and downstream fixings 32, 33 and carries the U-shaped support member 37 and the holding stud 38.

[0070] The U-shaped support member 37 comprises a first projecting branch 39 intended to extend under the electrical machine 15, in particular in contact with the main casing 25, and a second projecting branch 40, intended to extend above the electrical machine 15, in particular in contact with the main casing 25.

[0071] The holding stud 38 projects from the connection structure 36, upstream of the U-shaped support member, in the direction of the electrical machine 15, and is intended to cooperate with a relief of the main casing 25 in order to block the vertical movements of the electrical machine.

[0072] In a second embodiment shown schematically in [Fig.5], the main axis X of the turbomachine 2 and the axis of rotation X' of the rotor shaft 24 are not parallel to each other.

[0073] In particular, the main axis X of the turbomachine 2 and the axis of rotation X' of the rotor shaft 24 are coplanar and form between them an angle [3 less than 15°.

[0074] Such an embodiment makes it possible to fix the electric machine 15 as close as possible to a curved surface of the nacelle 3, reducing the mechanical moment and the aerodynamic drag.

[0075] In this case, the transverse axis Y is always perpendicular to the main axis X, but the transverse axis Y is not perpendicular to the axis of rotation X' of the rotor shaft 24, with which it forms an angle α strictly less than 90°, and greater than or equal to 75°.

[0076] The angle variation is then entirely taken up by the second set of bevel gears 29, which have respective angles adapted to the value of the angle a.

Claims

Claims

1. Propulsion assembly (1) for a rear fuselage (17) of an aircraft, comprising: - a double-flow turbomachine (2) having a main axis (X), the turbomachine (2) comprising a high-pressure body and a low-pressure body comprising a low-pressure shaft (11) mounted to rotate about the main axis (X), - a nacelle (3) receiving the turbomachine (2), substantially symmetrical about the main axis (X), - a mast (14) for supporting the turbomachine (2) fixed to the turbomachine (2) on the one hand and intended to be fixed to the rear fuselage (17) on the other hand, and - an electric machine (15) comprising at least one stator (22) secured to the turbomachine (2), arranged externally to the nacelle (3), on a side opposite the mast (14) relative to the main axis (X), and at least one rotor (23) driven in rotation by the low-pressure shaft (11) around an axis of rotation (X') forming an angle (|3) less than or equal to 15° with the main axis (X).

2. A propulsion unit (1) according to claim 1, wherein the rotor (23) is driven by the low pressure shaft (11) through a transverse shaft (27) extending substantially perpendicular to the main axis (X) and through a first set of bevel gears (28) meshing the low pressure shaft (11) and the transverse shaft (27) and a second set of bevel gears (29) meshing the transverse shaft (27) and the rotor (23).

3. A propulsion assembly (1) according to claim 2, wherein the first set of bevel gears (28) is connected to a downstream end (30) of the low pressure shaft (11).

4. Propulsion assembly (1) according to claim 2 or 3, wherein at least one of the first set of bevel gears (28) and the second set of bevel gears (29) comprises two bevel gears of different diameters, so that the rotor (23) of the electric machine (15) has a speed higher than the speed of the low pressure shaft (H).

5. Propulsion assembly (1) according to one of the preceding claims, in which the axis of rotation (X') of the rotor (23) of the electric machine (15) is substantially parallel to the main axis (X) of the turbomachine (2).

6. Propulsion assembly (1) according to one of claims 2 to 4, in which the axis of rotation (X') of the rotor (23) of the electric machine (15) forms an angle (a) less than 90° with the transverse shaft (27).

7. Propulsion assembly (1) according to one of the preceding claims, in which the turbomachine (2) comprises means (20, 21) for fixing to the mast (14) provided on two opposite sides of the turbomachine (2) on either side of the main axis (X), the electric machine (15) being fixed to the turbomachine (2) by the fixing means (21) located on the side opposite the means (20) for fixing the turbomachine (2) to the mast (14).

8. Propulsion assembly (1) according to the preceding claim, in which the electric machine (15) is fixed to the turbomachine (2) by fixing means (26) which comprise a cradle (35), said cradle comprising a U-shaped support member (37) provided with two branches (39, 40) between which the electric machine (15) is arranged.

9. Propulsion assembly (1) according to the preceding claim, in which the means (26) for fixing the electric machine (15) to the turbomachine (2) are rigid.

10. Aircraft (18) comprising a fuselage and at least two propulsion units (1) according to one of the preceding claims, fixed to a rear (17) of said fuselage by substantially horizontal masts (14).