Energy transfer in an aircraft turbine engine

Abstract

The invention relates to a turbine engine (10) for an aircraft (18), comprising a system (30) for transferring energy from one of its shafts (12) to another of its shafts (14), this system (30) comprising a mechanical differential with epicyclic gear train, centered on the axis (X) and comprising a sun gear (32) constrained to rotate with one of the shafts (12), a ring gear (34), and planet gears (36) which are interposed between the sun gear (32) and the ring gear (34) and which are carried by a planet carrier (238), a first of the elements chosen from the ring gear (32) and the planet carrier (38) being constrained to rotate with the other of the shafts (14), the system (30) further comprising a first device (40) for braking a second of the elements chosen from the ring gear (34) and the planet carrier (38).

Description

Description TITLE: ENERGY TRANSFER IN AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to the aeronautical field. It relates in particular to a turbomachine comprising a device for transferring energy from one shaft to another shaft of the turbomachine. Technological background

[0002] The technical background includes documents WO-A1-2008 / 044972 and US-A1-2017 / 058781.

[0003] Hybrid propulsion is a key element in reducing the carbon footprint of air transport. For turbofan applications, studies have shown that hybridization as understood in automobiles, with the addition of large batteries, is not relevant because batteries are very heavy and the potential gains are insufficient to offset the losses due to their weight.

[0004] The strategy adopted was to hybridize the turbofan engines during transient phases. Hybridization involves transferring power from one shaft to another (high pressure (HP) to low pressure (LP) and / or LP to HP) in order to optimize overall engine performance and reduce engine operating time during non-optimal phases. Thanks to this, the problem associated with adding large batteries is no longer relevant.

[0005] Figure 1 shows an example of a hybridization case. On the turbomachinery 10 used on modern airliners or business jets, the BP shaft 12 has a much greater inertia than the HP shaft 12. Thus, a small power draw from the BP shaft 12 in favor of reinjection onto the HP shaft 14 will result in a significant gain on the latter and therefore on the overall performance of the engine. This observation is all the more true as new generations of engines tend to maximize the size of the turbomachine's propulsion propeller 16, and therefore the inertia of the BP shaft 12.

[0006] Today, power transfer from one shaft to another is achieved using electrical machines that can act as both motors and generators. The mechanical energy of a shaft is transformed into electrical energy, allowing it to be easily transmitted to the motor. This electrical energy is then converted back into mechanical energy to be injected onto the other shaft. The constraints of electrical energy require having at least one buffer battery even for energy transfer during transient phases.

[0007] A use case would therefore be: 1. Mechanical power extraction from the BP shaft via an AGB type power transmission gearbox, 2. Transformation of mechanical power into electrical power via the electrical machine connected to the BP and called "LPMG", 3. Transfer of electrical power from the LPMG to buffer batteries, 4. Transfer of power from the batteries to the electrical machine connected to the HP and called "HPMG", 5. Transformation of electrical power into mechanical power via HPMG, and 6. Mechanical power injection onto the HP shaft via an AGB (Accessory Gear Box) type power transmission box.

[0008] However, this architecture is not optimal for several reasons. - At each stage in the transfer chain, losses occur. Numerous factors impact efficiency: mechanical transmission, LPMG, electrical cables, battery, mechanical transmission, HPMG, etc. Therefore, the overall efficiency of this solution is not very good. - The use of electrical machines makes the solution much less reliable. The failure rate of electronic components is lower than that of mechanical parts, or at the very least, sometimes more difficult to control with certainty. This implies the addition of new failure modes related to the new electrical machine technology, including a fire safety risk in the event of a short circuit. This leads to new requirements, such as the development of a mechanical disconnection system to be installed upstream of the electrical machines. This disconnection system is complex, heavy, and takes up space in already highly constrained motor environments. - The solution is complicated to implement because it is a complex system and difficult to integrate into the engine because the two links with the two shafts are far apart.

[0009] The present invention offers a simple, effective and economical solution to the problem of the prior art. Summary of the invention

[0010] The invention proposes for this purpose a turbomachine for an aircraft, comprising along a longitudinal axis: - a low-pressure compressor, - a high-pressure compressor, - an annular combustion chamber, - a high-pressure turbine, and - a low-pressure turbine, high-pressure compressors and turbines comprising rotors which are connected to each other by a high-pressure shaft which is tubular and centered on the axis, low-pressure compressors and turbines comprising rotors which are connected to each other by a low-pressure shaft which is centered on the axis and which passes axially through the high-pressure shaft, the turbomachine further comprising a system for transferring energy from one of the shafts to the other of the shafts, characterized in that said system comprises a mechanical differential with an epicyclic gear train centered on the axis and comprising a sun gear fixed in rotation to one of the shafts, a ring gear, and satellites which are interposed between the sun gear and the ring gear and which are carried by a satellite carrier, a first of the elements chosen from the ring gear and the satellite carrier being fixed in rotation to the other of the shafts,and in that the system further comprises a first braking device for a second element chosen from among the crown and the satellite carrier.

[0011] The invention proposes a purely mechanical power transfer method, without the use of electrical energy. This is achieved by connecting the low-pressure (LP) shaft and the high-pressure (HP) shaft via an epicyclic gear train. Mechanical systems offer significantly higher efficiency compared to electrical systems. Losses are therefore minimized, and the gains associated with hybridization are maximized. The reliability of mechanical systems is also easier to control than that of electrical systems, which is crucial in the aerospace industry. The resulting power transfer system is simpler, more compact, and lighter.

[0012] The HP shaft and the BP shaft are connected by an epicyclic gear train, which itself consists of a ring gear, a sun gear, satellites, and a satellite carrier. When none of the three parts—sun gear, ring gear, and satellite carrier—is blocked or When one of the components is braked or locked, this is transparent to both shafts; that is, the energy transfer system is inactive. Both shafts rotate at their respective speeds and are neither braked nor accelerated by the other. This is referred to as the non-activated case. When one of the components is braked or locked, the planetary gear train becomes active, and a connection is established between the high-pressure (HP) and low-pressure (LP) shafts. Depending on the gear train design, it is possible to choose to accelerate one shaft relative to the other (and therefore decelerate the other); this is referred to as the activated case. Several possible configurations will be described below.

[0013] The first braking device can be of any type and this application describes several examples of implementation of this device.

[0014] The turbomachine may include one or more of the following features, taken alone or in combination: - the solar element is rotationally fixed to the high-pressure shaft, and the first of said elements is rotationally fixed to the low-pressure shaft; - the braking system is of the electric brake type; - the braking device comprises an electric rotor centered on the axis and carried by the second of said elements, and an electric stator centered on the axis and which surrounds the electric rotor; - the braking system is of the drum type; - the braking device comprises an external cylindrical surface centered on the axis and supported by the second of said elements, and a drum in the shape of an angular sector which extends around the axis and which is able to bear against said external cylindrical surface; - the braking system is of the disc brake type; - the braking device comprises an annular disc centered on the axis and carried by the second of said elements, and a caliper through which said disc passes and which is capable of clamping it; - the longitudinal end of the low-pressure shaft is connected to a propulsion propeller without a mechanical reduction gear; - the longitudinal end of the low-pressure shaft is connected to a propulsion propeller via a mechanical reducer; - a longitudinal end of the low-pressure shaft is connected to a propulsion propeller for the purpose of driving its rotation; - the turbomachine also includes a second braking device for the first of the elements.

[0015] The invention also relates to an aircraft equipped with such a turbomachine. The invention also relates to a method of energy transfer in a turbomachine as described above, comprising two distinct phases: - a first phase without energy transfer, in which the first braking device is inactive, and - a second phase with energy transfer, in which the first braking device is active and slows the rotation of the second element, causing one of the shafts to accelerate and the other shaft to decelerate.

[0016] Advantageously, during the second phase, the high-pressure shaft is accelerated and the low-pressure shaft is decelerated.

[0017] The process may include braking the first of said elements when the propeller undergoes a freewheeling phenomenon. Brief description of the figures

[0018] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the detailed explanatory description that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which: [Fig. 1] Figure 1 is a highly schematic view of an aircraft turbomachine and illustrates energy transfer within this turbomachine. [Fig.2] Figure 2 is a very schematic view of an aircraft turbomachine according to the invention, [Fig. 3a-3b] Figures 3a and 3b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a first embodiment of the invention, [Fig. 4a-4b] Figures 4a and 4b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a second embodiment of the invention, [Fig. 5a-5b] Figures 5a and 5b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a third embodiment of the invention, [Fig. 6] Figure 6 is a very schematic view of another aircraft turbomachine according to the invention, [Fig. 7a-7b] Figures 7a and 7b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a fourth embodiment of the invention, [Fig. 8a-8b] Figures 8a and 8b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a fifth embodiment of the invention, [Fig. 9a-9b] Figures 9a and 9b are schematic perspective and axial section views of an energy transfer device for an aircraft turbomachine, according to a sixth embodiment of the invention, [Fig. 10] Figure 10 is a very schematic view of another aircraft turbomachine according to the invention, [Fig. 11] Figure 11 is a very schematic view of another aircraft turbomachine according to the invention, [Fig.12] Figure 12 is a very schematic view of another aircraft turbomachine according to the invention. Detailed description of the invention

[0019] In this description, identical or substantially identical elements and / or elements with the same functions are represented by the same numerical references.

[0020] Figures 1 and 2 represent a turbomachine 10 which is intended to be mounted on an aircraft 18. The aircraft 18 comprises, for example, a fuselage and two wings extending on either side of the fuselage relative to the fuselage axis. Each wing can carry at least one turbomachine 10.

[0021] The turbomachine 10 can be a turbojet or a turboprop.

[0022] The turbomachine 10 may include at least one propeller 16 configured to participate in the propulsion of the aircraft. The propeller 16 may be an unfaired propeller or may be faired and be, for example, a fan.

[0023] Turbomachine 1 has a longitudinal axis X, which here is the axis of rotation of the turbomachine rotors.

[0024] In the present invention, and more generally, the terms "upstream," "downstream," "axial," and "axially" are defined with respect to the gas flow in the turbomachine and with respect to the longitudinal axis X of the turbomachine. Similarly, the terms "radial," "radially," "internal," and "external" are defined with respect to a radial axis Z perpendicular to the longitudinal axis X.

[0025] The turbomachine 10 generally comprises, from upstream to downstream, a set of compressors 22, an annular combustion chamber 24 and a set of turbines 26 which preferably form a gas generator.

[0026] The turbomachine 10 is, in particular, a twin-spool, twin-flow turbomachine. The compressor assembly 22 comprises a low-pressure compressor 22a and a high-pressure compressor 22b. The turbine assembly 26 comprises a high-pressure turbine 26a and a low-pressure turbine 26b. The rotors of the low-pressure compressor 22a and the low-pressure turbine 26b are connected by a low-pressure shaft 12 to form a low-pressure housing. The rotors of the high-pressure compressor 22b and the high-pressure turbine 26a are connected, for example, by a high-pressure shaft 14 to form a high-pressure housing. The high-pressure shaft 14 is tubular and is traversed axially by the low-pressure shaft 12.

[0027] The impeller 16 is mounted upstream of the compressor assembly 22. The impeller 16 advantageously, but not exclusively, comprises blades 16a extending radially outwards from a hub 16b. The hub 16b is coupled to one longitudinal end of the low-pressure shaft 12, either directly or via a mechanical reduction gear (not shown). The blades 16a may be enclosed by a blower housing 28 centered on the longitudinal axis X.

[0028] Figure 2 illustrates the invention which consists of equipping the turbomachine 10 with a system 30 for transferring energy from one of the shafts to the other of the shafts.

[0029] According to the invention, the system 30 comprises a mechanical differential with an epicyclic gear train which is centered on the axis X and which includes a sun 32 fixed in rotation to one of the shafts 12, 14, a ring 34, and satellites 36 which are intercalated between the sun 32 and the ring 34 and which are carried by a satellite carrier 38. A first of the elements chosen from the ring 34 and the satellite carrier 38 is fixed in rotation to the other of the shafts 14, 12.

[0030] In addition, the system 30 includes a first braking device 40 for a second of the elements chosen from the ring 34 and the satellite carrier 38.

[0031] In the embodiment shown in Figure 2, the solar element 32 is rotationally fixed to the high-pressure shaft 14, and the first element is rotationally fixed to the low-pressure shaft 12. The first element here is the ring gear 34, which is therefore rotationally fixed to the low-pressure shaft 12. The braking device 40 is thus configured to act on the second element, namely the carrier. satellites 38. The operation of this example implementation will be described below.

[0032] Figures 3a-3b, 4a-4b and 5a-5b illustrate several embodiments of the braking device 40.

[0033] Figures 3a-3b illustrate a braking device 40 of the electric brake type. The braking device 40 comprises an electric rotor 42 centered on the X-axis and carried by the planet carrier 38, and an electric stator 44 centered on the X-axis and surrounding the electric rotor 42.

[0034] Figures 4a-4b illustrate a drum-type braking device 40. The braking device 40 comprises an external cylindrical surface 46 centered on the X-axis and supported by the planet carrier 38, and a drum 48 in the shape of an angular sector extending around the X-axis and adapted to bear against the external cylindrical surface 46.

[0035] Figures 5a-5b illustrate a braking device 40 of the disc brake type. The braking device 40 comprises an annular disc 50 centered on the X-axis and carried by the planet carrier 38, and a caliper 52 through which the disc 50 passes and which is adapted to clamp it between pads 54, for example.

[0036] In the embodiment shown in Figure 6, the solar element 32 is rotationally fixed to the high-pressure shaft 14, and the first element is rotationally fixed to the low-pressure shaft 12. The first element here is the planet carrier 38, which is therefore rotationally fixed to the low-pressure shaft 12. The braking device 40 is thus configured to act on the second element, namely the ring gear 34. The operation of this other embodiment will be described below.

[0037] Figures 7a-7b illustrate a braking device 40 of the disc brake type. The braking device 40 comprises an annular disc 50 centered on the X-axis and carried by the ring 34, and a caliper 52 through which the disc 50 passes and which is adapted to clamp it between pads 54, for example.

[0038] Figures 8a-8b illustrate a drum-type braking device 40. The braking device 40 comprises an external cylindrical surface 46 centered on the X-axis and supported by the ring 34, and a drum 48 in the shape of an angular sector extending around the X-axis and adapted to bear against the external cylindrical surface 46.

[0039] Figures 9a-9b illustrate a braking device 40 of the electric brake type. The braking device 40 comprises an electric rotor 42 centered on the X axis is carried by the ring 34, and an electric stator 44 is centered on the X axis and surrounds the electric rotor 42.

[0040] In the embodiment examples in Figures 2 and 6, the longitudinal end of the low-pressure shaft 12 is connected to the propulsion propeller 16 without a mechanical reducer, i.e. at the same rotational speed.

[0041] In the other embodiment examples of figures 10 to 12, the longitudinal end of the low-pressure shaft 12 is connected to the propulsion propeller 16 via a mechanical reducer 60.

[0042] The example of implementation in Figure 10 differs from that in Figure 2 by the presence of the reducer 60.

[0043] The embodiment example in Figure 11 differs from that in Figure 10 in that it also includes a second braking device 70 for the first element, namely the ring 34.

[0044] The embodiment shown in Figure 12 differs from that shown in Figure 6 by the presence of the reducer 60, on the one hand, and by the presence of a second braking device 70 for the first of the elements, namely here the crown carrier 38, on the other hand.

[0045] The invention also relates to a method of transferring energy in a turbomachine 10 as described above. It is understood here that the energy is mechanical and is not transformed, in particular into electrical energy.

[0046] The process includes a first phase of operation without energy transfer. It is therefore understood that the transfer system 30 is passive or inactive and that the braking device 40 is also passive or inactive. There is no energy transfer between the shafts 12 and 14.

[0047] The process includes a second operating phase with energy transfer. It is therefore understood that the transfer system 30 is active and that the braking device 40 is also active. There is energy transfer between the shafts 12 and 14. More precisely, the braking device 40 slows the rotation of the second shaft, which causes one shaft to accelerate and the other to decelerate.

[0048] In the examples discussed above, during the second phase, the high-pressure shaft 14 is accelerated and the low-pressure shaft 12 is decelerated. The reverse would be possible.

[0049] In the embodiment of figures 3a-3b, the braking of the satellite carrier 38, by electrical supply of the braking device 40, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0050] In the embodiment of figures 4a-4b, the braking of the planet carrier 38, by clamping the drum 48 against the surface 46, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0051] In the embodiment of figures 5a-5b, the braking of the planet carrier 38, by clamping the disc 50 in the caliper 52, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0052] In the embodiment of figures 7a-7b, the braking of the crown 34, by clamping the disc 50 in the caliper 52, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0053] In the embodiment of figures 8a-8b, the braking of the crown 34, by clamping the drum 48 against the surface 46, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0054] In the embodiment of figures 9a-9b, the braking of the crown 34, by electrical supply of the braking device 40, causes the transfer of mechanical energy from the low pressure shaft 12 to the high pressure shaft 14.

[0055] In the embodiment of Figure 11, it is also possible, in addition to the braking of the satellite carrier 38 by the device 40, as in the embodiment of Figures 3a-3b, 4a-4b, and 5a-5b, to brake the propeller 16 by the device 70. For this purpose, the braking device 70 acts on the ring gear 34 of the device 30. The solar element of the reduction gear 60 is generally coupled to the low-pressure shaft 12 and will thus be braked to prevent the propeller 16 from running away and in particular a freewheeling phenomenon commonly called "windmilling".

[0056] In the embodiment of Figure 12, it is also possible, in addition to the braking of the ring gear 34 by the device 40, as in the embodiment of Figures 7a-7b, 8a-8b, and 9a-9b, to brake the propeller 16 by the device 70. For this purpose, the braking device 70 acts on the ring gear carrier 38 of the device 30. The solar element of the reduction gear 60 is generally coupled to the low-pressure shaft 12 and will thus be braked to prevent the propeller 16 from running away and in particular a freewheeling phenomenon commonly called "windmilling". The invention described above thus enables power transfer to be achieved purely mechanically, without the use of electrical energy. This is accomplished by connecting the LP shaft and the HP shaft via an epicyclic gear differential. This type of mechanical system has very high efficiency compared to electrical systems. Losses are therefore minimized, and the gains associated with hybridization are thus maximized. The reliability rates of the systems are improved. Mechanical systems are also easier to optimize than electrical systems, which is crucial in aeronautics. Generally speaking, the 30 energy transfer system is simpler, more compact, and lighter.

Claims

DEMANDS 1. Turbomachine (10) for an aircraft (18), comprising along a longitudinal axis (X): - a low-pressure compressor (22a), - a high-pressure compressor (22 bar), - an annular combustion chamber (24), - a high-pressure turbine (26a), and - a low-pressure turbine (26b), high-pressure compressors and turbines (22b, 26a) comprising rotors which are connected to each other by a high-pressure shaft (14) which is tubular and centered on the axis (X), low-pressure compressors and turbines (22a, 26b) comprising rotors which are connected to each other by a low-pressure shaft (12) which is centered on the axis (X) and which axially passes through the high-pressure shaft (14), the turbomachine (10) further comprising a system (30) for transferring energy from one of the shafts (12) to the other of the shafts (14), characterized in that said system (30) comprises a mechanical differential with an epicyclic gear train centered on the axis (X) and comprising a sun gear (32) fixed in rotation to one of the shafts (12), a ring gear (34), and satellites (36) which are interposed between the sun gear (32) and the ring gear (34) and which are carried by a satellite carrier (238),a first of the elements chosen from the ring (32) and the planet carrier (38) being rotationally fixed to the other of the shafts (14), and in that the system (30) further comprises a first braking device (40) for a second of the elements chosen from the ring (34) and the planet carrier (38), said first braking device being capable of operating according to two distinct phases:, - a first phase without energy transfer, in which the first braking device (40) is inactive, and - a second phase with energy transfer, in which the first braking device (40) is active and brakes the rotation of the second of the elements, which causes the acceleration of one of the shafts (14) and the deceleration of the other of the shafts (12).

2. Turbomachine (10) according to the preceding claim, characterized in that the solar element (32) is rotationally fixed to the high-pressure shaft (14), and the first of said elements is rotationally fixed to the low-pressure shaft (12).

3. Turbomachine (10) according to any one of the preceding claims, characterized in that the braking device (40) is of the electric brake type.

4. Turbomachine (10) according to the preceding claim, characterized in that the braking device (40) comprises an electric rotor (42) centered on the axis (X) and carried by the second of said elements, and an electric stator (44) centered on the axis (X) and which surrounds the electric rotor (42).

5. Turbomachine (10) according to any one of the preceding claims, characterized in that the braking device (40) is of the drum type.

6. Turbomachine (10) according to the preceding claim, characterized in that the braking device (40) comprises an external cylindrical surface (46) centered on the axis (X) and carried by the second of said elements, and a drum (48) in the shape of an angular sector which extends around the axis (X) and which is able to bear against said external cylindrical surface (46).

7. Turbomachine (10) according to any one of the preceding claims, characterized in that the braking device (40) is of the disc brake type.

8. Turbomachine (10) according to the preceding claim, characterized in that the braking device (40) comprises an annular disc (50) centered on the axis (X) and carried by the second of said elements, and a caliper (52) through which said disc (50) passes and which is able to clamp it.

9. Turbomachine (10) according to any one of the preceding claims, characterized in that the longitudinal end of the low-pressure shaft (12) is connected to a propulsion propeller (16) without a mechanical reducer.

10. Turbomachine (10) according to any one of claims 1 to 8, characterized in that the longitudinal end of the low pressure shaft (12) is connected to a propulsion propeller (16) via a mechanical reducer (60).

11. Turbomachine (10) according to the preceding claim, characterized in that it further comprises a second braking device (70) for the first of the elements.

12. A method for transferring energy in a turbomachine (10) according to any one of the preceding claims, comprising two distinct phases: - a first phase without energy transfer, in which the first braking device (40) is inactive, and - a second phase with energy transfer, in which the first braking device (40) is active and brakes the rotation of the second of the elements, which causes the acceleration of one of the shafts (14) and the deceleration of the other of the shafts (12).

13. Method according to claim 12, wherein, during the second phase, the high-pressure shaft (14) is accelerated and the low-pressure shaft (12) is decelerated.

14. Method according to claim 12 or 13, wherein, the turbomachine (10) being as defined in claim 11, it comprises braking the first of said elements when the propeller (16) undergoes a freewheeling phenomenon.

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