阅读说明：本技术 包括电源装置的涡轮反应器 (Turbo-reactor comprising a power supply device ) 是由 亨利·耶西尔西门 卡罗琳·玛丽·弗兰茨 尼古拉斯·杰罗姆·让·坦托 娜塔莉·诺瓦科夫斯基 吉 于 2019-09-20 设计创作，主要内容包括：一种双流涡轮反应器(10),包括风扇(20),定位在风扇(20)下游并使主要流道(12)与次级流道(14)分离的壳体(30),布置在主要流道(12)中的压气机(60)、燃烧室(70)和涡轮(80),所述涡轮反应器包括一种耦合到涡轮(80)的差速传动装置(40、50),以及一种被构造成提供附加功率到由涡轮(80)所提供的功率以驱动压气机(60)的电源装置(90)。(A dual flow turbo-reactor (10) comprising a fan (20), a housing (30) positioned downstream of the fan (20) and separating a primary flowpath (12) from a secondary flowpath (14), a compressor (60), a combustor (70) and a turbine (80) disposed in the primary flowpath (12), the turbo-reactor comprising a differential transmission (40, 50) coupled to the turbine (80), and a power supply device (90) configured to provide additional power to the power provided by the turbine (80) to drive the compressor (60).)

1. A dual flow turbofan engine (10) comprising a fan (20), a housing (30) positioned downstream of the fan (20) and separating a primary flowpath (12) from a secondary flowpath (14), a compressor (60), a combustor (70), and a turbine (80) disposed in the primary flowpath (12), the turbofan engine comprising a differential transmission (40, 50) coupled to the turbine (80), and an electrical power device (90) configured to provide additional power to power provided by the turbine (80) to drive the compressor (60).

2. The turbofan engine of claim 1, further comprising a control unit (99) configured to control the power supply device (90) in accordance with a rotational speed of the turbine (80).

3. Turbofan engine according to claim 1 or 2, wherein the power supply device (90) comprises an electric motor (91) configured to drive the compressor (60) in rotation.

4. Turbofan engine according to any of claims 1 to 3, wherein the power supply means (90) comprises a generator (92) configured to be driven by the turbine (80).

5. Turbofan engine according to claim 3 or 4, comprising an electrical storage device (96) electrically connected to the electric motor (91) or the electrical generator (92).

6. Turbofan engine according to any of claims 1 to 5, wherein the power supply device (90) comprises a connector (94) configured to be connected to an external power source.

7. Turbofan engine according to any of claims 1 to 6, wherein the power supply means (90) comprises a variable speed mechanical transmission (98a, 98b, 98c) coupled on the one hand to the shaft (62) of the compressor and on the other hand to the shaft (82) of the turbine.

8. Turbofan engine according to any of claims 1 to 7, wherein the power supply device (90) comprises an electromagnetic transmission device (98a, 98b, 98c) coupled on the one hand to the shaft (62) of the compressor and on the other hand to the shaft (82) of the turbine.

9. Turbofan engine according to any of claims 1 to 8, wherein the maximum additional power provided by the power supply device (90) is larger than 1.5 MW.

10. Turbofan engine according to any of claims 1 to 9, wherein the power supply device (90) is configured to be deactivated when the rotational speed of the turbine (80) is greater than 95% of a nominal maximum rotational speed of the turbine (80).

11. Turbofan engine according to any of claims 1 to 10, the turbofan engine (10) being a single spool turbofan engine and the bypass ratio between the secondary flow path (14) and the main flow path (12) being greater than or equal to 12.

12. Turbofan engine according to any of claims 1 to 11, wherein the differential transmission comprises a first reduction gear (40) configured to modify the speed ratio between the turbine (80) and the fan (20) and a second reduction gear (50) configured to modify the speed ratio between the turbine (80) and the compressor (60).

13. The turbofan engine of claim 12 wherein the first reduction gear (40) is a differential reduction gear having an input wheel (44) rotationally fixed to a turbine wheel (80), a first output wheel (48) rotationally fixed to the fan (20), a second output wheel (42) rotationally fixed to an input wheel of the second reduction gear (42), and the second reduction gear (50) is an epicyclic reduction gear having an output wheel (54) rotationally fixed to the compressor (60).

14. The turbofan engine of claim 13 wherein a ratio of a number of teeth of the first output wheel (48) of the first reduction gear (40) to a number of teeth of the input wheel (44) of the first reduction gear (40) is greater than 1.

15. Turbofan engine according to claim 13 or 14, wherein the ratio of the number of teeth of the ring gear (58) of the second reduction gear (50) to the number of teeth of the output gear (54) of the second reduction gear (50) is larger than 2.

16. Turbofan engine according to any of claims 13 to 15, wherein the ratio of the number of teeth of the first output wheel (48) of the first reduction gear (40) to the number of teeth of the input wheel (44) of the first reduction gear (40) is smaller than the ratio of the number of teeth of the ring gear (58) of the second reduction gear (50) to the number of teeth of the output wheel (54) of the second reduction gear (50).

17. Turbofan engine according to any of claims 12 to 16, wherein the gear ratio of the second reduction gear (50) is larger than 3.

18. Turbofan engine according to any of claims 1 to 17, wherein the fan (20) has a compression ratio at cruising speed between 1.3 and 1.45.

19. Turbofan engine according to any of claims 1 to 18, wherein the compressor (60) has a compression ratio greater than or equal to 25 at 15500 rpm.

20. The turbofan engine of any one of claims 1 to 19 wherein the total pressure ratio for climbing the top is greater than or equal to 30.

Technical Field

The present invention relates to the field of aircraft, and more particularly to turbojet engines usable for aviation propulsion.

Background

In recent years, aircraft engines have undergone many improvements which increase the performance of the engine and significantly reduce its fuel consumption and its greenhouse gas emissions. Currently, the effort required to obtain similar gains in the coming years is reasonably much higher. This means a considerable increase in costs and also an increase in the complexity of the system implemented, so that the operability of the engine and its performance/cost ratio may deteriorate.

There is therefore a need for a new type of aircraft engine, in particular a turbojet, which forms a more acceptable compromise between different parameters such as specific fuel consumption, drag, geometry, mass, simplicity and cost.

Disclosure of Invention

To this end, the invention relates to a turbofan engine comprising a fan, a casing positioned downstream of the fan and separating a primary flowpath from a secondary flowpath, a compressor, a combustion chamber and a turbine having been arranged in the primary flowpath, the turbofan engine comprising a differential transmission coupled to the turbine, and a power supply device configured to provide additional power to power provided by the turbine to drive the compressor.

In the present invention, the so-called turbofan engine axis is its axis of symmetry or quasi-symmetry forming the axis of rotation of the compressor and turbine. The axial direction corresponds to an axial direction of the turbofan engine, and the radial direction is a direction perpendicular to and intersecting the axis. Likewise, an axial plane is a plane containing the axis of the turbofan engine, and a radial plane is a plane perpendicular to the axis. A circumference is understood to be a circle which belongs to a radial plane and whose center belongs to the axis of the turbofan. The tangential direction or circumferential direction is the direction tangential to the circumference; it is perpendicular to, but does not pass through, the axis of the turbofan engine.

Unless otherwise specified, the adjectives "forward" and "aft" are used with reference to the axial direction, it being understood that the inlet of the turbofan engine is positioned on the forward side of the turbofan engine, while its outlet is positioned on the aft side. The adjectives "upstream" and "downstream" are used with reference to the normal direction of airflow in a turbofan engine.

Finally, unless otherwise specified, the adjectives "inner (inner)" and "outer (outer)" are used with reference to the radial direction, so that, in the radial direction, the inner portion of one element is closer to the axis of the turbofan engine than the outer portion of the same element.

The turbofan engine is referred to as a turbofan engine because it includes a primary flowpath for receiving a primary flow and a secondary flowpath for receiving a secondary flow. The housing separating the primary and secondary flow passages is sometimes referred to as an inner housing.

As shown, the differential drive is coupled to the turbine, i.e. there is a functional, possibly permanent, connection between the turbine and the differential drive. The differential drive may be configured to drive the fan and/or the compressor due to the mechanical energy provided by the turbine. A differential transmission is a power transmission that allows speed and/or torque ratios to be modified between at least one input member (in this case a turbine) and at least one output (in this case a fan and/or compressor). Within the meaning of the invention, the transmission ratio of the differential transmission can be less than 1, in which case it is sometimes referred to as a reduction system (reduction system), but can also be greater than 1, depending on what component is considered to be the input or output component, in which case it is sometimes referred to as a multiplication system. The differential gearing may be electromechanical or purely mechanical.

The turbofan engine may be a single spool turbofan engine. A single spool turbofan engine comprises a single rotating assembly that connects one or more compressors to one or more turbines via a common kinematic system, which does not mean that all components rotate at the same speed, but rather that their rotations are linked. In contrast, a twin-spool turbofan engine comprises two kinematically independent rotating assemblies, each of which connects its own compressor and turbine via its own kinematic system, which is independent of the other assembly's own kinematic system. Hereafter, for the sake of simplicity and without loss of generality, it will be assumed that a single shaft comprises one compressor and one turbine.

Unlike most, if not all, current developments in turbofan engines based on dual rotors, the present invention proposes to implement a turbofan engine having a single shaft. Such an architecture allows to greatly simplify the turbofan, for example by reducing its mass and cost, thanks to the suppression of complex components such as shafts, bearings and supports.

Furthermore, since the turbofan engine comprises a power supply arrangement configured to provide additional power to the power provided by the turbine to drive the compressor, depending on the speed, the compressor can be caused to operate in a desired operating range, whereas the turbine alone at the speed in question, in particular at a low speed, is not allowed to operate in this range. Thus, regardless of turbofan engine speed, the performance level of the turbofan engine is comparable to other existing turbofan engines or has a better performance/cost ratio than existing turbofan engines.

In some embodiments, the turbofan engine further comprises a control unit configured to control the power supply device in dependence on a rotational speed of the turbine. Thus, the power supply device may be controlled in accordance with the speed of the turbofan engine. This allows to precisely adapt the parameters of the turbofan and to optimize the operation of the turbofan.

In some embodiments, the power supply apparatus includes a motor configured to drive rotation of the compressor. In these embodiments, the power supply means can be controlled in a very flexible way according to the need for power, in particular continuously over a range covering zero power to the maximum estimated power of the power supply means.

In some embodiments, the power supply device comprises a generator configured to be driven by the turbine. The generator may be configured to supply power to the electric motor described above directly or via an electric storage device.

Indeed, in some embodiments, the turbofan engine includes an electrical storage device electrically connected to the electric motor or generator. Thus, during certain flight phases, for example at high speeds, the turbine may drive a generator such that excess mechanical power is stored in the form of electricity in an electricity storage device. During other flight phases, for example at low speeds, the compressor may be driven by a turbine and a motor that draws its energy from an electrical storage device. However, other variations are possible. For example, rather than being charged by a turbine-driven generator, the electrical storage device may be charged by a power source external to the turbofan engine.

Thus, in some embodiments, the power supply device includes a connector configured to connect to an external power source.

In some embodiments, the power supply means comprise a variable speed mechanical transmission coupled on the one hand to the shaft of the compressor and on the other hand to the shaft of the turbine. Thus, the variable speed mechanical transmission allows deriving power from the turbine for driving the compressor, which power can be controlled, for example, in dependence on the speed of the turbofan engine. The variable speed mechanical transmission may be connected or disconnected from the compressor and/or the turbine. The variable speed mechanical transmission may transmit a fixed or variable proportion of turbine power to the compressor. The variable speed mechanical transmission may include any of the following elements: clutches, gearboxes, transmissions, etc.

In some embodiments, the power supply device comprises an electromagnetic transmission device coupled on the one hand to the shaft of the compressor and on the other hand to the shaft of the turbine. For example, the electromagnetic transmission may be a magnetic geared transmission. Electromagnetic drives have many advantages, in particular no mechanical fatigue, no lubrication, no mechanical contact losses, no noise, and high efficiency.

In some embodiments, the maximum additional power provided by the power supply device is greater than 1.5 Megawatts (MW). This additional maximum power is used to compensate for the power not provided by the turbine at the particular speed of the turbofan engine.

In some embodiments, the power device is configured to be deactivated when the rotational speed of the turbine is greater than 95% of the nominal maximum rotational speed of the turbine. Thus, the size of the power supply unit can be limited to operating at moderate mechanical speeds where its function is useful, thereby minimizing its mass and complexity. For example, the power supply arrangement may be configured to be deactivated when the rotational speed of the turbine is sufficient to drive the compressor solely at a reduced speed of at least 50%, preferably at least 70%, of the nominal speed. Conversely, the power supply device may be configured to start when the rotational speed of the turbine is insufficient to drive the compressor at a reduced speed of at least 50%, preferably at least 70%, of the nominal speed alone.

The invention also relates to a single spool turbofan engine comprising a fan, a housing positioned downstream of the fan and separating a primary flowpath from a secondary flowpath, a compressor, a combustor, and a turbine disposed in the primary flowpath, the turbofan engine comprising a differential transmission coupled to the turbine, wherein a bypass ratio between the secondary flowpath and the primary flowpath is greater than or equal to 12.

The bypass ratio between the secondary flowpath and the primary flowpath, more simply referred to as the bypass ratio (BPR), is the ratio of the flow rate of air entering the secondary flowpath to the flow rate of air entering the primary flowpath. Increasing the BPR allows for increased performance of the turbofan engine because the thrust is substantially provided by the air swept by the fan and passing through the secondary flowpath.

However, increasing the BPR requires increasing the diameter of the fan, which results in an associated increase in the cross-section of the secondary flowpath.

The performance of the turbofan engine is further improved due to the bypass ratio between the secondary flowpath and the primary flowpath being greater than or equal to 12. For example, such bypass ratios may be achieved in the range of subsonic jet speeds of turbofan engine exhausts for corresponding aircraft speeds between mach 0.7 and mach 0.9, preferably between mach 0.8 and mach 1 at the throat of the jet nozzle.

In some embodiments, the differential drive includes a first reduction gear configured to modify a speed ratio between the turbine and the fan, and a second reduction gear configured to modify a speed ratio between the turbine and the compressor.

Thus, the rotation of the fan can be decoupled from the rotation of the compressor, which allows for different rotational speeds for the two components. This allows the compressor speed to be maintained at a certain level while reducing the fan speed. However, the rotational speed of the fan limits the tangential velocity of the radially outer portions of the fan blades (also referred to as the blade tips). The speed of the blade tip must meet certain constraints, in particular maintaining a subsonic speed, for example, less than or equal to 310 meters per second (m/s). Thus, the fact that the fan speed can be reduced allows the diameter of the fan to be increased at equivalent blade tip speeds. The result is still better performance of the turbofan engine.

In some embodiments, the second reduction gear is coupled to the output of the first reduction gear.

In some embodiments, the first reduction gear is a differential reduction gear having an input wheel rotationally fixed to the turbine wheel, a first output wheel rotationally fixed to the fan, a second output wheel rotationally fixed to the input wheel of the second reduction gear, and the second reduction gear is an epicyclic reduction gear having an output wheel rotationally fixed to the compressor.

A reduction gear is a device that allows the speed and/or torque ratio between at least one input wheel and at least one output wheel to be modified. Within the meaning of the invention, the reduction gear can have a transmission ratio smaller than 1, but also larger than 1, depending on what component is considered to be the input or output component (reduction gears are usually reversible transmissions), in the case of larger than 1 the reduction gear is sometimes called a multiplier. The differential reduction gear may relate the rotation of three wheels, for example one input wheel and two output wheels. An epicyclic reduction gear may relate the rotation of two wheels, for example one input wheel and one output wheel.

The differential reduction gear and/or the epicyclic reduction gear may be designed in the form of an epicyclic gearing. An epicyclic gear train typically has outer planet gears, also known as a ring gear, and inner planet gears, also known as planet gears or sun gears. The sun gear and the ring gear are coupled by one or more planet gears, which are coupled together by a planet carrier. Within the meaning of the present invention, a so-called "wheel" in the general sense is any of a ring gear, a planet carrier or a sun gear. Each wheel may be used as an input or output member of the mechanical transmission.

In this case, the rotation of the turbine is transmitted to the fan via the first reduction gear. The result is a first gear ratio, such as a first torque ratio, between the turbine and the fan. The second output wheel of the first reduction gear drives the input wheel of the second reduction gear, and the output of the second reduction gear drives the compressor. The result is a second gear ratio between the turbine and the compressor. Thus, the use of a differential reduction gear allows the rotation of the fan and the compressor to be decoupled. To limit the complexity of the turbofan engine, the epicyclic reduction gear may be coupled with the differential reduction gear, rather than directly with the turbine.

In some embodiments, the ratio of the number of first output teeth of the first reduction gear to the number of input teeth of the first reduction gear is greater than 1. The ratio may be greater than 1.2, more preferably greater than 1.4. Furthermore, the ratio may be less than 1.8, more preferably less than 1.6. This ratio is approximately equal to 1.5. Under normal operation, the first reduction gear is therefore configured to provide a lower rotational speed to the fan than is provided to the compressor.

In some embodiments, the ratio of the number of ring gear teeth of the second reduction gear to the number of output gear teeth of the second reduction gear is greater than 2. For an epicyclic gear train, the gear ring of the second reduction gear may be fixed relative to the inner casing of the turbofan engine. This ratio allows to increase the rotational speed of the compressor with respect to the speed provided by the first reduction gear at the input of the second reduction gear. The ratio may be greater than 5, more preferably greater than 6. Furthermore, the ratio may be less than 9, more preferably less than 8. This ratio is approximately equal to 7.

In some embodiments, the ratio of the number of teeth of the first output gear of the first reduction gear to the number of teeth of the input gear of the first reduction gear is less than the ratio of the number of ring gear teeth of the second reduction gear to the number of output gear teeth of the second reduction gear. This is the ratio of the two ratios; in the example given, it can also be verified that 1.5 is less than 7. In this configuration, the diameters of the different wheels of the differential transmission can be reduced, and the overall cost of the differential transmission can be limited.

In some embodiments, the second reduction gear has a gear ratio greater than 3. The transmission ratio is the ratio of the output wheel speed to the input wheel speed. For a planetary gear, the rotational speed of the planet carrier considered corresponds to the rotational speed of the planetary gear around the sun gear and not to the rotational speed of the planetary gear around itself.

The transmission ratio may be greater than 6, more preferably greater than 7. Furthermore, the transmission ratio may be less than 10, more preferably less than 9. The transmission ratio may be approximately equal to 8.

In some embodiments, the fan has a compression ratio between 1.3 and 1.45 at cruising speeds. By general definition, the so-called fan compression ratio is the ratio of the volume-average total pressure of a given mass of air at the fan input (input) to the volume-average total pressure of the same mass of air at the fan output. The relatively low compression ratio allows for improved performance of the turbofan engine.

In some embodiments, the compressor has a compression ratio of greater than or equal to 25 at 15500 rpm. Such compression ratios are suitable for the aerodynamics of compressors and turbines. For example, the compressor may comprise at least eight stages of moving blades, preferably at least nine or ten stages.

In some embodiments, the total pressure ratio for climbing the top is greater than or equal to 30. The total pressure ratio or OPR is the ratio of the total air pressure at the compressor output to the total air pressure at the fan input. The point called the "climb apex" is the point at which the elevation is completed, which is typically calculated so that the elevation is as economical and short as possible. A high OPR allows to increase the thermal efficiency, and therefore the performance, of the gas generator of a turbofan engine. An OPR between 30 and 40 seems to be less advantageous than in a dual rotor turbofan engine, but this is compensated by a huge improvement in simplicity, operability and cost.

In addition, unless otherwise stated, the numerical values mentioned in the present invention were measured when the turbofan engine was stationary in the standard atmosphere specified in International Civil Aviation Organization (ICAO) manual, document No. 7488/3, 3 rd edition, and when stationary at sea level.

The invention also relates to a turbofan engine comprising a fan, a compressor, a combustion chamber, a turbine configured to drive the fan in rotation via a first reduction gear and to drive the compressor in rotation via a second reduction gear, wherein an output end (output) of the first reduction gear is rotationally coupled to an input end (input) of the second reduction gear by a reduction shaft supported by a bearing arranged between the first reduction gear and the second reduction gear.

It will therefore be appreciated that the above-mentioned bearing may be arranged axially between the first reduction gear and the second reduction gear. The bearing may be supported relative to a stationary housing of the turbofan engine, in particular fixed relative to the combustion chamber.

Due to the support of the reduction shaft by bearings arranged between the first reduction gear and the second reduction gear, the turbofan has good dynamic conditions, i.e. good mechanical and pneumatic behaviour at operating speed, and a predominant natural vibration mode located outside the operating speed, i.e. can cause damage to the turbofan. Furthermore, the bearing allows to properly hold the first reduction gear and the second reduction gear, while avoiding or limiting the dynamic coupling between these two reduction gears.

In some embodiments, the bearing is a roller bearing. Thus, the bearing allows axial movement of the reduction shaft.

In some embodiments, a bearing is supported by the housing. Since the bearing is supported by the inner casing, the support structure of the bearing can be simplified, which limits the increase in mass of the turbofan engine, simplifies the general structure thereof and improves the performance thereof.

In some embodiments, the bearings are disposed radially outward of the compressor shaft, turbine shaft, and reduction shaft. This allows further optimization of the dynamic conditions of the turbofan engine.

In some embodiments, the reduction shaft is a planet carrier common to the first reduction gear and the second reduction gear.

In addition to the features just mentioned, the proposed turbofan may comprise one or more further bearings according to features among the following considered alone or in technically possible combinations:

-a fan bearing arranged between the fan shaft and the housing. A fan bearing supporting the fan shaft relative to the housing;

-a compressor bearing arranged between the compressor shaft and the housing. The compressor bearing, also referred to as a first compressor bearing, supports the compressor shaft relative to a housing;

-a second bearing, such as a roller bearing, arranged to support the reduction shaft. The fact that two roller bearings are used to support the reducer avoids static uncertainties;

an inter-shaft bearing, such as a roller bearing, arranged between the compressor shaft and the turbine shaft. An inter-shaft bearing may be disposed radially between the compressor shaft and the turbine shaft and support the two shafts opposite to each other;

a compressor bearing arranged between the compressor shaft and a structural component downstream of the compressor, which may be, for example, the casing of the combustion chamber or a diffuser positioned between the compressor and the combustion chamber. A compressor bearing, also referred to as a second compressor bearing, supports the compressor shaft relative to the structure.

Brief description of the drawings

The invention and its advantages will be better understood on reading the following detailed description of embodiments, given by way of non-limiting example. The description makes reference to the accompanying drawings, in which:

FIG.1 is a schematic view of a turbofan according to one embodiment;

fig.2 schematically shows an axial half-section of a turbofan according to a second embodiment;

fig.3 schematically shows an axial half-section of a turbofan according to a third embodiment;

fig.4 schematically shows an axial half-section of a turbofan according to a fourth embodiment;

fig.5 schematically shows an axial half section of a turbofan according to a fifth embodiment.

Detailed Description

Fig.1 schematically shows a turbojet engine 10 according to one embodiment. In this case, turbojet 10 is a single-spool turbofan. In practice, the turbojet engine 10 comprises a fan 20, an inner casing 30 arranged downstream of the fan 20 and separating the primary flow path 12 from the secondary flow path 14. The compressor 60, the combustor 70 and the turbine 80 are arranged in the main flow passage 12 from upstream to downstream. Due to the fact that the turbojet engine 10 is a single-shaft engine, it comprises a single rotating assembly comprising a compressor 60 and a turbine 80. In this case, the turbojet comprises a single compressor 60 driven directly or indirectly by a single turbine 80, the turbine 80 being started by combustion gases coming from the combustion chamber 70.

The fan 20 may comprise an impeller. The fan 20 may be sized such that its compression ratio at cruising speeds at approximately 2,600rpm is between 1.3 and 1.45. The diameter of the fan 20 may be between 2 and 2.7 meters, more specifically between 2.2 and 2.4 meters. Here, "diameter of the fan 20" will be understood as the radial distance between the axis of the turbojet 10 and the ends of the fan blades.

The compressor 60 may comprise 5 to 15 stages, in particular 8 to 12 stages, preferably about 10 stages, each stage being formed by a blade and a vane. It should be remembered that the blades of the stages of the same compressor are rotationally fixed about the compressor axis. The compressor may be sized such that its compression ratio is greater than or equal to 25 at a speed of approximately 15500rpm, which may correspond to cruise speed.

Thus, in the present embodiment, the OPR of the turbojet 10 may be greater than or equal to 30.

The turbine 80 may include 2 to 6 stages, particularly 3 to 5 stages, preferably about 4 stages. It should be remembered that the blades of multiple stages of the same turbine are rotationally fixed about the turbine axis. The turbine may rotate at approximately 8600rpm at cruising speed.

In the present embodiment, the turbine 80 rotationally drives the compressor 60. The turbine 80 also rotationally drives the fan 20. More specifically, turbojet engine 10 includes a differential drive coupled to turbine 80. In this case, as shown in fig.1, the differential transmission is coupled to the fan 20 and the compressor 60, and here includes a first reduction gear 40 configured to modify the speed ratio between the turbine 80 and the fan 20, and a second reduction gear 50 configured to modify the speed ratio between the turbine 80 and the compressor 60.

In this embodiment, the bypass ratio (also referred to as BPR) between the secondary flowpath 14 and the primary flowpath 12 is greater than or equal to 12, preferably greater than or equal to 14, or even 14.5. In the present embodiment, such a BPR can be realized due to the diameter of the fan, the compression ratio of the fan, and the number of stages of the turbine 80. However, other parameters may also be involved: for example, high BPR can also be achieved by a joint increase in OPR and turbine inlet temperature, which combination helps to reduce the mass flow rate of the main flow path, thereby increasing BPR.

As mentioned above, in the turbojet engine 10, the speed of rotation of the fan 20 can be separated from the speed of rotation of the compressor 60. For example, at full power, the ratio of the speed of the compressor 60 to the speed of the fan 20 may be between 5.5 and 6.5. Furthermore, unlike a single differential reduction gear, the use of two reduction gears may alleviate mechanical and aerodynamic stresses on the turbine 80.

Fig.2 to 5 show a turbojet engine 10 in a further embodiment. In these figures, elements corresponding or equivalent to those of the first embodiment will have the same reference numerals and will not be described again.

Fig.2 shows the structure of the turbojet engine 10 in more detail.

It is first noted that the fan shaft 22, the compressor shaft 62 and the turbine shaft 82 are decoupled from one another due to the differential transmission.

As shown in fig.2, the first reduction gear 40 is a differential reduction gear having an input wheel 44, in this case a sun gear (also referred to as sun gear 44), which is rotationally fixed to a turbine wheel 80, here via a turbine shaft 82, and a first output wheel 48, in this case a ring gear (also referred to as ring gear 48), which is rotationally fixed to the fan 20, here via the fan shaft 22. Preferably, the ratio R1 of the number of teeth of the first output gear 48 to the number of teeth of the input gear 44 is greater than 1, and in the present embodiment, approximately equal to 1.5.

The sun gear 44 and the ring gear 48 are engaged by the planet gears 46. One or more planet gears 46 may be provided. Within the meaning of the present invention, the term "joined" denotes the mutual joining of two elements, whether this joining is mechanical, electromagnetic or of other nature. The planet carrier 42 connected to the planet gear 46 forms a second output wheel of the first reduction gear 40.

Further, the second reduction gear 50 is an epicyclic reduction gear. As described above, the second reduction gear 50 has the input wheel rotationally fixed to the second output wheel 42 of the first reduction gear 40. In this case, as shown in fig.2, the carrier 42 forms the second output wheel of the first reduction gear 40 and the input wheel of the second reduction gear 50. Therefore, the carrier 42 also forms a reduction shaft between the first reduction gear 40 and the second reduction gear 50. Thus, in this embodiment, the following terms will be used interchangeably: planet carrier 42, the reduction shaft, the second output wheel of first reduction gear 40, the input wheel of second reduction gear 50. However, typically, these components may be separate from each other, in which case the outlet of the first reduction gear 40 is rotationally coupled to the inlet of the second reduction gear 50 by the reduction shaft 42.

The transfer shaft 42 is the planet carrier of the first reduction gear 40 and independently also the planet carrier of the second reduction gear 50. Thus, the second reduction gear 50 comprises one or more planet gears 56, the rotation of which planet gears 56 is actuated by the rotation of the planet carrier 42.

In addition to its input wheel 42, the second reduction gear 50 also comprises an output wheel 54, in this case a sun gear (also referred to as sun gear 54) which is here rotationally fixed to the compressor 60 via a compressor shaft 62. In the present embodiment, the sun gear 54 is engaged with the planet gears 56. The planet gears 56 can furthermore be coupled to a ring gear 58, which is fixed here relative to the housing 30.

Preferably, the ratio R2 of the number of teeth of the ring gear 58 of the second reduction gear 50 to the number of teeth of the planetary gear 56 is greater than 2, and in the present embodiment is approximately equal to 7.

In addition, in the present embodiment, the ratio R1 is smaller than the ratio R2.

The second reduction gear may be sized to have a gear ratio greater than 3, for example approximately equal to 8.

As can be seen in fig.2, the first and second reduction gears 40, 50 are coaxial.

Bearings may be provided to support the shaft. In particular, the reduction shaft 42 may be supported by a bearing 41 arranged between the first reduction gear 40 and the second reduction gear 50, so as to improve the dynamic conditions of the differential transmission. More specifically, as shown in fig.2, a bearing 41 (a roller bearing in this case) is axially arranged between the first reduction gear 40 and the second reduction gear 50, and is radially arranged between the reduction shaft 42 and the housing 30, thereby supporting the reduction shaft 42 relative to the housing 30.

The reduction shaft 42 may be supported by a second bearing 43, if necessary. The second bearing 43 may be provided at the front of the first reduction gear 40, or as shown in fig.2, the second bearing 43 may be provided at the rear of the second reduction gear 50. The second bearing 43 may be a roller bearing. The second bearing 43 may be radially disposed between the reduction shaft 42 and the housing 30. The second bearing 43 may support the reduction shaft 42 with respect to the housing 30.

Further, the fan shaft 22, the compressor shaft 62, and the turbine shaft 82 may each be supported independently of one another by at least one bearing, or in this embodiment by at least two bearings.

According to one example, the fan shaft 22 is supported relative to the housing 30 by a forward fan bearing 21 and an aft fan bearing 23. Further, according to one example, the compressor shaft 62 is supported by a forward compressor bearing 61 relative to the housing 30, and the compressor shaft 62 is supported by a rearward compressor bearing 63 relative to a structural member 72 downstream of the compressor (here the combustor housing). Further, according to one example, the turbine shaft 82 is supported by a rear turbine bearing 83 relative to an exhaust housing 84 (also referred to as a "turbine rear frame" (TRF)).

Further, the compressor shaft 62 may be coaxial with the turbine shaft 82 and mounted outside the turbine shaft 62. In this perspective view, an inter-shaft bearing 81 arranged between the compressor shaft 62 and the turbine shaft 82, in particular radially between these two shafts, may be provided. The inter-shaft bearing 81 supports the compressor shaft 62 relative to the turbine shaft 82 and allows relative rotation thereof.

For each of the shafts 22, 62, 82, it may be provided that one bearing ensures axial locking of the shaft, for example in the form of a ball bearing, while the other bearing allows axial displacement of the shaft, for example in the form of a roller bearing, so as to control the axial position of the shaft while avoiding static overdeterminations.

In this example, the forward fan bearing 21 and inter-shaft bearing 81 are roller bearings, while the fan and aft turbine bearings 23, 83 are ball bearings. In this example, the front compressor bearings 61 are ball bearings and the rear compressor bearings are roller bearings.

It should be noted that, in order to further improve the dynamics, in this case, the ball bearings 23, 61 can be positioned as close as possible to the inlet housings of the fan 20 and of the compressor 60, respectively, by reducing the length of the relative shaft 22, 62, 82 so that its natural mode intervenes at higher rotational speeds that may exceed the operating speed range of the turbojet engine. For example, the bearings may be placed near the inlet housings of the fan 20 and compressor 60, respectively, as the geometry of these housings allows.

As shown in fig.2, the first bearing 41 supporting the reduction shaft 42 may be a bearing called a "large radius" bearing, that is, a bearing having a radius relatively close to that of the housing 30 to which the first bearing is fixed. In this case, the bearing 41 is arranged radially outside the compressor shaft 62, the turbine shaft 82, and the reduction shaft 42.

It should be noted that, thanks to the simplified structure of the turbojet 10, and in particular of the single-shaft engine 10, the distance between the bearings supporting the same shafts can be reduced compared to the more complex structures currently developed. This results in better rotation mechanics of the components of the turbojet 10. In general, reducing the shaft length to diameter ratio may improve the shaft dynamics.

In terms of mass, the inventors estimate that the mass gain of the turbojet engine 10 of the second embodiment is between 5% and 15% compared to a conventional twin-spool turbofan with a single reduction gear.

In the third to fifth embodiments shown in fig.3 to 5 respectively, in order to reduce the risk of the compressor 60 being at too low a speed when the turbine 80 is rotating at idle or more generally at a non-zero but low speed, an electrical power supply arrangement 90 may be provided which is configured to provide additional power to the power provided by the turbine 80 to drive the compressor 60. Of course, such a power supply device may be compatible with the above-described embodiments.

The power supply device may be of various types. For example, the power supply device 90 may be configured to provide power from a source separate from the turbine 80, and thus not directly or indirectly, momentarily, or with a delay, from the turbine 80. Conventionally, in the third embodiment, the power supply device 90 includes a motor 91 configured to rotationally drive the compressor 60. As shown in fig.3, the electric motor 91 may be engaged with the compressor shaft 62. In the present embodiment, the electrical energy of the electric motor 91 may come from an electrical generator 92 configured to be driven by the turbine 80, or more specifically, the turbine shaft 82.

Alternatively or in addition, the power supply device 90 may comprise a connector 94, said connector 94 being configured to be connected to a power supply external to the turbojet engine and to supply the electric motor 91 with the necessary electric power, the additional power for driving the compressor 60 being substantially useful despite the idling of the turbine 80 when the turbojet engine 10 is operating on the ground and at idle in flight (for example during descent).

Alternatively or additionally, as shown in fig.4 with reference to the fourth embodiment, the electric energy for driving the electric motor 91 may come from an electric storage device 96 electrically connected to the electric motor. The electrical storage device 96 may be connected to the generator 92 or to the connector 94 shown in the third embodiment, where appropriate. According to this configuration, the electric storage device 96 can function as a buffer, thereby accumulating the energy generated by the generator 92 independently of its consumption by the electric motor 91.

The power storage device 96 may include one or more batteries, or any other suitable storage device.

However, the power supplied by the power supply device 90 does not have to be switched electrically. In a fifth embodiment, shown in fig.5, the power supply means 90 comprise a variable speed mechanical or electromagnetic transmission coupled on the one hand to the shaft 62 of the compressor 60 and on the other hand to the shaft 82 of the turbine 80. More specifically, the power supply device 90 includes a first engagement member 98a rotationally fixed to the compressor shaft 62, and a second engagement member 98b rotationally fixed to the turbine shaft 82. The first and second engagement elements 98a, 98b may be variably engaged with each other (which includes the possibility of disengaging them) by a mechanical or electromagnetic linkage 98 c. For example, the linkage 98c may be a clutch, a differential system, an electromagnetic coupling, or any other variable speed transmission of mechanical energy.

The third, fourth and fifth embodiments have in common that the power supplied by the power supply device 90 to the compressor 60 is variable and controllable. To this end, a control unit 99 may be provided which is configured to control the power supply device 90. For example, the control unit 99 may control the power supply device on the basis of the rotation speed of the turbine 80 or another parameter indicative of the rotation speed of the turbojet engine 10. For example, it may be useful to activate the power device 90 when the turbine is rotating at less than or equal to 95% of its maximum nominal rotational speed, and it may be useful to deactivate the power device 90 when the rotational speed of the turbine is greater than 95% of its maximum nominal rotational speed. Therefore, even when the turbine 80 is in the idle mode, the compressor 60 can be maintained at a stable rotational speed, thereby providing good operability, that is, the stable and transient operating points of the turbine can be maintained at a sufficiently distant distance from the aerodynamic instability region.

The power supply device 90 may be sized such that the maximum additional power provided by the power supply device may be greater than 1.5 Megawatts (MW), preferably greater than or equal to 1.8MW, more preferably greater than or equal to 2.1 MW.

Although it is proposed to increase the speed of the compressor 60 when the turbine 80 rotates at idle speed, the power supply device 90 may be used incidentally as an auxiliary device for the acceleration of the turbojet engine 10, for example in start-up or in fast transient maneuvers.

Further, the power supply device may be used as a part of a twin-spool turbofan engine that includes, in addition to the above-described compressor and turbine forming the high-pressure spool, a low-pressure compressor or supercharger and a low-pressure turbine positioned on both sides of the high-pressure shaft and forming the low-pressure spool. The low pressure compressor is driven by a low pressure turbine. For example, the power supply device can be used to supply power to the high-pressure shaft, thereby improving its operability by reducing the operating line of the high-pressure compressor, which is generally defined as the coordinate system [ compression ratio; reduced mass flow rate ] of the compressor. When the power supply device is used, the supplied power can be taken from the low-pressure shaft, which improves the operability of the low-pressure compressor by lowering its operating line.

Although the present description refers to particular exemplary embodiments, modifications may be made to these examples without departing from the general scope of the invention, as defined by the appended claims. In particular, individual features of the different embodiments described/mentioned may be combined in additional embodiments. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.