Hybrid turbojet engine, method for controlling a turbojet engine and computer program product for performing the method

Abstract

A hybrid turbojet engine comprising: - an input shaft (a26) configured to be driven by a low-pressure turbine (102), - an output shaft (a64) for driving an electric machine (104) and another output shaft (a64') for driving another electric machine (104'), - a variable speed drive (106) for adjusting the speed of each output shaft (a64, a64') based on the speed of the input shaft, the drive comprising: • a first planetary gear train (T1) comprising at an input end a carrier (108) connected to the input shaft, a ring gear (112) and planet gears (110), the first planetary gear train comprising at an output end a first sun gear (130) connected to the output shaft, • a second planetary gear train (T2) comprising at an input end the ring gear (112) and another planet gear (120), the second planetary gear train comprising at an output end a second sun gear (140) connected to the other output shaft, • a locking device (MB) for locking or putting the ring gear in a free state.

Description

Technical Field

[0001] This invention belongs to the field of aviation, and more specifically relates to a hybrid turbojet engine. Background Technology

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, states have already implemented, are implementing, or will implement various restrictions on carbon emissions. In particular, stringent standards apply to both new and currently operational aircraft, necessitating the implementation of technological solutions to ensure compliance with existing regulations. For many years, civil aviation has been committed to helping address climate change.

[0003] Technological research has significantly improved the environmental performance of aircraft. The applicant considers factors influencing all stages of design and development to obtain more energy-efficient and environmentally friendly aerospace components and products. The integration and use of these components and products in civil aviation will have a moderate environmental impact, with the aim of improving aircraft energy efficiency. Therefore, the applicant is committed to continuously reducing its climate impact and thus lowering its environmental footprint by adopting sound development and manufacturing methods and minimizing greenhouse gas emissions.

[0004] This ongoing research and development effort focuses on next-generation aircraft engines, particularly by using lighter materials and lighter avionics to make aircraft lighter, thereby developing electric propulsion technologies, and ultimately researching aviation biofuels.

[0005] Against this backdrop, a hybrid turbojet engine has been proposed, which has a propulsion configuration that combines a conventional turbojet engine with at least one electric motor capable of operating in engine mode and generator mode.

[0006] In a known manner, a hybrid turbojet engine for an aircraft integrates at least one electric motor on the high-pressure (HP) body and / or low-pressure (BP) body of the turbojet engine.

[0007] Documents US2020 / 386188A1, US10208675B2, US2020 / 248632A1, FR3103011A1, or WO2020 / 058652A1 describe hybrid turbojet engines for aircraft.

[0008] The motor is connected to the shaft of the HP or BP body. The motor can be used in "generator mode" to generate electricity from mechanical energy, or conversely, in "engine mode" to supply mechanical energy from electricity.

[0009] When the motor is used in "generator mode", it is usually referred to as a "generator".

[0010] In practice, the motor is driven by a turbine (called the low-pressure turbine (TBP)) within the BP engine via a rotating drive shaft to generate current to power the aircraft. This motor is called the BP motor. The size of the BP motor and its control electronics is determined by the range of the motor's speed to deliver a constant electrical power, expressed in kilowatts (kW). In fact, the wider the range, the larger the motor becomes, which increases the weight of the turbojet engine.

[0011] A turbojet engine includes a fan, or rotating component, whose rotor is equipped with blades that draw air into the turbojet engine. Some types of fans are known to have blades whose orientation (i.e., pitch) can be adjusted.

[0012] The variable-pitch blades of the fan ensure the performance of the hybrid turbojet engine, but the BP main body has a limited speed range. On the other hand, for a turbojet engine with a fixed pitch (i.e., fixed blade orientation), the speed range of the BP main body is almost doubled, which has a significant impact on the size of the electrical components of the BP motor, thereby increasing the weight of the turbojet engine.

[0013] In existing hybrid turbojet engines, it is known to connect a BP motor directly to a low-pressure turbine via a common drive shaft. However, these turbojet engines are not optimized in terms of size and weight: the BP motor and its control electronics remain relatively bulky, thus increasing the weight of the turbojet engine.

[0014] Therefore, it may be desirable to design a hybrid turbojet engine that avoids at least some of the aforementioned problems and limitations. For example, it is necessary to reduce the overall weight of existing hybrid turbojet engines while maintaining the BP motor at a constant power output. Summary of the Invention

[0015] The present invention includes a variable speed drive in a hybrid turbojet engine, which enables ratio switching between components of a low-pressure turbine and two BP motors driven differently according to the low-pressure speed of the engine (the speed of the shaft connected to the low-pressure turbine).

[0016] More specifically, a hybrid turbojet engine is proposed, which includes: Low-pressure turbine; A first motor and a second motor, the motors being configured to supply constant power together; The input shaft is configured to be driven by a low-pressure turbine; A first output shaft and a second output shaft, wherein the first output shaft is configured to drive a first motor and the second output shaft is configured to drive a second motor; A device for acquiring the rotational speed of the input shaft; A variable speed drive for adjusting the speed of each output shaft based on the speed of the input shaft, the drive comprising: A first planetary gear train, comprising: - at the input end a planet carrier, a ring gear, and at least one first planetary gear, the planet carrier being connected to the input shaft, and the at least one first planetary gear being carried by the planet carrier and engaging with the ring gear; - at the output end a first sun gear, which meshes with the at least one first planetary gear and is centered on a first output shaft aligned with the input shaft. The first gear has a first transmission ratio defined between the rotational speed of the first output shaft and the rotational speed of the input shaft, and a first ratio defined between the ring gear and the first sun gear, also given. The second planetary gear train comprises: - a ring gear and at least one second planetary gear at the input end, the at least one second planetary gear engaging with the ring gear and being carried by a fixed bearing; - a second sun gear at the output end, the second sun gear meshing with the second planetary gear and centered on a second output shaft aligned with the input shaft. The second gear train has a second transmission ratio defined between the rotational speed of the second output shaft and the rotational speed of the input shaft, which is less than the first transmission ratio defined for the first gear train. The second gear train also has a second ratio defined between the ring gear and the second sun gear, which is the same as the first ratio defined for the first gear train. A locking device for locking the gear ring in two operating modes: a first operating mode and a second operating mode. In the first operating mode, the gear ring is locked and prevents any rotation of the second planetary gear and the second motor. In the second operating mode, the gear ring is in a free state. An electronic control unit is used to compare the acquired rotational speed with a predetermined threshold. When the acquired rotational speed is greater than the predetermined threshold, the electronic control unit sends a control signal to the locking device to put the gear ring in a free state, and sends a control signal to the first motor to drive the first sun gear at a constant rotational speed.

[0017] Therefore, the speed range of one of the BP motors and the maximum torque value borne by each motor can be limited while delivering a constant total electrical power (the sum of the electrical power of the two motors). This limitation on the speed range of at least one motor is significant and makes it possible to reduce the overall weight of the BP generator in the hybrid turbojet engine.

[0018] These features also have the advantage of simplifying the structure of turbojet engines, particularly in terms of the size and mass of the BP generator, which consists of two motors, thereby simplifying the control electronics for these two motors.

[0019] The present invention may also include one or more of the following optional features in any technically possible combination: - The first planetary gear train is configured such that the first gear ratio is equal to four and the first ratio is equal to three, and the second planetary gear train is configured such that the second gear ratio is at most equal to two and the second ratio is equal to three.

[0020] - The turbojet engine includes a fan at the inlet and connected to the input shaft, the fan comprising multiple blades with a fixed orientation.

[0021] - The acquisition device used to obtain the rotational speed of the input shaft is a speed sensor, which is configured to measure the instantaneous rotational speed of the input shaft.

[0022] - The predetermined threshold is defined as a function of the maximum speed. Preferably, the predetermined threshold is set to 5000 tr / mn. Preferably, for a gear ratio of four, the maximum speed is 20000 tr / mn.

[0023] - The locking device for locking the gear ring can be released to free the gear ring, and is a braking component arranged on the second output shaft.

[0024] - The locking device used to lock the gear ring can be released to free the gear ring, and is the short-circuit torque generated by the second motor on its own resistance.

[0025] - Turbojet engines also include dedicated electric inverters for each motor, without DC-DC converters.

[0026] The present invention also relates to a method for controlling a turbojet engine as described above, the method comprising the following steps: Obtain the rotational speed of the input shaft; The acquired rotational speed is compared with a predetermined threshold. If the obtained rotational speed is greater than a predetermined threshold, a control signal is sent to the locking device used to lock the gear ring to put the gear ring in a free state, and a control signal is sent to the first motor to drive the first sun gear at a constant rotational speed.

[0027] Finally, the present invention relates to a computer program product capable of being downloaded from a communication network and / or recorded on a computer-readable medium, characterized in that, when the program is executed on a computer, the computer program product includes instructions for performing the steps of the above-described method. Attached Figure Description

[0028] The invention will be better understood through the following description, given only by way of example and with reference to the accompanying drawings, in which: - Figure 1 A hybrid-powered turbojet engine with a variable speed drive in a first operating mode is shown as an example according to the present invention; - Figure 2 It shows Figure 1 The hybrid turbojet engine is in its second operating mode; - Figure 3 A turbojet engine control method according to an embodiment of the present invention is illustrated schematically; - Figure 4 The results illustrate the rotational speed behavior of the low-pressure turbine and electric motor in a hybrid turbojet engine, based on one possible example; and - Figure 5 Another result is shown, illustrating the torque behavior of the low-pressure turbine and electric motor of a turbojet engine, based on one possible example. Detailed Implementation

[0029] refer to Figure 1 and Figure 2 A hybrid turbojet engine 100 according to an embodiment of the present invention will now be described.

[0030] The turbojet engine 100 includes a low-pressure turbine 102, a first motor 104, a second motor 104', and a transmission drive 106 mounted between the low-pressure turbine 102 and each motor 104, 104' to transmit mechanical power from the low-pressure turbine 102 to the two motors 104, 104'.

[0031] The turbojet engine 100 includes an input shaft a26 connected to a low-pressure turbine 102 for being driven by the low-pressure turbine 102.

[0032] Upstream of the low-pressure turbine 102, the turbojet engine 100 includes a fan 180 for injecting airflow F. The fan 180 is connected to the input shaft a26.

[0033] The fan 180 includes a plurality of blades 182. In this example, the fan has a fixed pitch, meaning that the orientation of each blade in the blades 182 is fixed. However, the invention may also include a variable pitch fan.

[0034] The turbojet engine 100 includes a first output shaft a64 configured to drive a first motor 104 and a second output shaft a64' to drive a second motor 104'. Thus, each motor 104, 104' is driven by a low-pressure turbine 102 via a transmission driver 106, which differs from prior art hybrid turbojet engines where the motors are directly mounted on the low-pressure turbine 102.

[0035] The turbine 102 and the motors 104 and 104' are aligned in the same direction that coincides with the input shaft a26 and the output shafts a64 and a64'.

[0036] The transmission drive 106 is designed to operate according to the rotational speed of the turbine 102 (i.e., the rotational speed ω of the input shaft a26). T On the one hand, the rotational speed ω of the first motor 104 is adjusted. ME (i.e., the rotational speed of the output shaft a64), and on the other hand, adjusting the rotational speed ω' of the second motor 104'. ME (That is, the rotational speed of the output shaft a64').

[0037] The variable speed drive 106 includes two planetary gear systems T1 and T2, which are speed-increasing planetary gear systems, preferably planetary gear systems.

[0038] The first planetary gear train T1 includes an input planet carrier 108, a ring gear 112, and at least one first planetary gear 110. The input planet carrier 108 is connected to the input shaft a26, and the at least one first planetary gear 110 is carried by the planet carrier 108 and held by the ring gear 112.

[0039] The first planetary gear train T1 includes a first sun gear 130 at the output end, which meshes with the first planetary gear 110 and is centered on the first output shaft a64, which is aligned with the input shaft a26.

[0040] The first planetary gear train T1 has a first transmission ratio defined between the rotational speed of the first output shaft a64 and the rotational speed of the input shaft a26, and a first ratio defined between the ring gear 112 and the first sun gear 130.

[0041] The second planetary gear train T2 includes a gear ring 112 and at least one second planetary gear 120 at the input end, the at least one second planetary gear 120 being held by the gear ring 112 and carried by the fixed shaft AF.

[0042] On the output side, the second planetary gear train T2 includes a second sun gear 140, which meshes with the second planetary gear 120 and is centered on the second output shaft a64', which is aligned with the input shaft a26.

[0043] The second planetary gear train T2 has a second transmission ratio defined between the rotational speed of the second output shaft a64' and the rotational speed of the input shaft a26, which is less than the first transmission ratio defined for the first gear T1. The second train also has a second ratio defined between the ring gear 112 and the second sun gear 140, which is the same as the first ratio defined for the first train T1.

[0044] It can be seen that the first planetary gear 110 may be driven by the support shaft of the planet carrier 108, while the second planetary gear 120 may be driven by the ring gear 112. The ring gear 112 is shared by both planetary gears 110 and 120.

[0045] According to a specific feature of the invention, it should be noted that the two planetary gear systems T1 and T2 have the same ratio k. As a result, the torque at the first output shaft a64 of the first motor 104 is the same as the torque at the second output shaft a64' of the second motor 104'.

[0046] By definition, the ratio k here refers to the relationship between the number of teeth on the gear ring 112 and the number of teeth on the sun gears 130 and 140.

[0047] With gear ring 112 locked, the rotational speed of the first output shaft a64 is equal to the rotational speed of the input shaft a26 multiplied by the ratio 1-k.

[0048] The speed drive 106 includes a function for obtaining the rotational speed ω of the input shaft a26. T The acquisition device 160. For example, the acquisition device may be configured to measure the rotational speed ω of the input shaft a26. T The speed sensor 160. In an alternative embodiment (not shown), the speed sensor may be located external to the transmission drive 106, in which case the acquisition device includes an interface configured to acquire speed measurements from the sensor.

[0049] The turbojet engine 100 also includes a locking device MB for locking the gear ring 112, which can be released to free the gear ring. The locking device MB can be a mechanical device, such as a brake member arranged on the second output shaft a64', thus applying torque to the second motor 104'. However, alternatively, such a mechanical device for the gear ring 112 can be omitted, and the locking device MB can be an electrical device, for example, by the second motor 104' applying a short-circuit torque to its own resistance. Other ways of implementing the locking device MB are conceivable. Figure 1 and Figure 2 It is shown schematically in the diagram.

[0050] The turbojet engine 100 also includes an electronic control unit (ECU) 170, which is used to process the rotational speed ω obtained for the input shaft a26. T With the predetermined threshold ω S Comparison, when the obtained rotational speed ω T Greater than the predetermined threshold ω S At that time, the ECU170 sends a control signal S to the locking device MB. C This allows the locking device MB to release the gear ring 112 and sends a control signal S to the first motor 104. C This allows the first motor 104 to preferably drive the first sun gear 130 at a constant speed. Therefore, the ECU 170 is configured to acquire data related to the rotation of the turbine 102, such as the rotational speed ω of the input shaft a26. T For example, ECU170 may be a microcontroller that includes a processor, possibly read-only memory (e.g., ROM), random access memory (e.g., RAM), peripheral units, and input / output interfaces. ECU170 may also be a Full Authority Digital Engine Control (FADEC).

[0051] For example, for a ratio k=3, the threshold rotational speed ω S The speed can be set to 5000 rpm (tr / mn), therefore, at low speeds, the gear ratio between the rotational speed of the sun gear 130 and the rotational speed of the input shaft a26 is 4, and the ring gear 112 is locked. This 5000 rpm threshold corresponds to a rotational speed of 20000 rpm for the sun gear 130 connected to the motor 104. This threshold allows for the definition of two operating modes of the speed controller 106 according to the invention, namely a first operating mode and a second operating mode, in which the ring gear 112 is locked by the locking device MB (…). Figure 1 In the second operating mode, gear ring 112 is unlocked. Figure 2 Furthermore, the rotational speed of the sun gear 130 is controlled at a constant speed by the first motor 104.

[0052] For each motor 104, 104', the turbojet engine 100 also includes an electric inverter or stator blades 190, 190' (or "AC / DC converter") for converting the AC voltage V supplied at the output of the motor 104 into a DC voltage U.

[0053] According to the features of the invention, compared with the conventional architecture that integrates a BP motor and electronic devices consisting of an AC / DC inverter and a DC / DC inverter, preferably, no DC / DC (direct current to direct current) converter is associated with the electric inverters 190, 190'.

[0054] Now refer to Figure 3 A method for controlling a transmission drive 106 of a turbojet engine 100 according to the present invention is described.

[0055] In measurement step 302, the instantaneous rotational speed ω of the input shaft a26 is measured by the speed sensor 160. T .

[0056] During comparison step 304, ECU170 acquires the instantaneous rotational speed ω of input shaft a26. T The value, and the instantaneous rotational speed ω of input shaft a26. T The value of ω is related to the predetermined threshold. S Compare them.

[0057] During test step 306, if the measured rotational speed ω T Greater than the predetermined threshold ω S If the measured rotational speed is less than the threshold, then ECU 170 determines that the gear ring 112 must be released. Under the default condition (i.e., the measured rotational speed is less than the threshold), the locking device MB (braking member, or alternatively, the short-circuit torque of motor 104' on its own resistance) locks the gear ring 112. In control step 308, ECU 170 generates a first control signal S. c And send a first control signal S to the locking device MB. c This allows the gear ring 112 to be in a free state. If the threshold is not reached, the rotational speed ω is measured again. T .

[0058] Once the speed sensor 160 measures the new rotational speed value ω T Then repeat the steps of the above method.

[0059] In this example, steps 304, 306, and 308 are implemented by ECU170 through computer program product P, which is stored in the memory of ECU170 in the form of instructions.

[0060] Figure 4 The results show the performance of the hybrid turbojet engine according to the invention, particularly compared to the prior art.

[0061] The first curve C1 (solid line) represents the rotational speed ω of the first motor 104, expressed in revolutions per minute (tr / mn), on the left y-axis for the turbojet engine 100 according to the present invention. METhe rotational speed ω of the low-pressure turbine 102, expressed in revolutions per minute (tr / mn) on the x-axis. T The function.

[0062] The second curve C2 (solid line) represents the rotational speed ω of the second motor 104', expressed in revolutions per minute (tr / min), on the left y-axis for the turbojet engine 100 according to the present invention. ME The rotational speed ω of the low-pressure turbine 102, expressed in revolutions per minute (tr / mn) on the x-axis. T The function.

[0063] The third curve C3 (solid line) represents the rotational speed of the equivalent (single) motor, but in the case of a conventional turbojet engine (i.e., the turbine is directly connected to the motor), there is no transmission drive.

[0064] The fourth curve C4 (dashed line) represents the turbine rotational speed ω of the electrical power P, expressed in kW on the right y-axis, supplied at the output of the first motor 104 for the turbojet engine according to the present invention. T The function.

[0065] The fifth curve C4 (dashed line) represents the turbine rotational speed ω of the electrical power P, expressed in kW on the right y-axis, supplied at the output of the second motor 104' for the turbojet engine according to the present invention. T The function.

[0066] Curve C4 (dashed line) represents the electric power P, expressed in kW on the right y-axis, supplied at the output of the low-pressure turbine 102 for the turbojet engine according to the present invention, as the turbine rotational speed ω. T The power is a function of the turbine shaft a26. This power is constant within the range of the turbine shaft's rotational speed (in this case, between 2000 rpm and 10000 rpm).

[0067] The sum of the power supplied by the first motor 104 and the power supplied by the second motor 104' is constant and corresponds to the power supplied by the low-pressure turbine.

[0068] At the turbine speed threshold speed (low speed, ω) less than 5000 rpm. T <ω S When the first motor 104' is locked, the gear ring 112 is locked, the second motor 104' does not supply power, and only the first motor 104 is operating. Therefore, the power supplied by the first motor 104 is combined with the power of the low-pressure turbine 102. On curve C1, we can see that the increase in the speed of the first motor is four times the increase in the speed of the low-pressure turbine, and on curve C2, we can see that the speed remains zero.

[0069] Starting from the threshold speed and exceeding the threshold speed (high speed, ω) T >ω S With gear ring 112 unlocked, the second motor 104' draws some power from the turbine. Therefore, power is distributed between the two motors 104 and 104'. Curve C1 shows that the speed of the first motor 104 no longer increases. On the other hand, curve C2 shows that the speed increase rate of the second motor does not exceed 2. Therefore, the maximum speed reached by the second motor 104' eventually reaches the maximum speed of the first motor 104 at 20000 rpm.

[0070] like Figure 4 As shown, compared to the prior art, the variable speed drive 106 significantly reduces the speed range. For a turbojet engine in the prior art, i.e., without a variable speed drive, the motor's speed range extends from 1860 rpm to 10000 rpm, meaning the ratio between the motor's minimum and maximum speeds is 5.4. With the variable speed drive 106, the motor 104's speed range extends from 7440 rpm to 20000 rpm, meaning the ratio between the motor 104's minimum and maximum speeds is 2.7, achieving a 2x gain in speed reduction compared to the prior art.

[0071] This gain is reflected in the magnitude of the voltage range supplied at the output terminals of motors 104 and 104'. Limiting the magnitude of the voltage range provides the advantage of eliminating the need for DC / DC converters used in conventional hybrid turbojet engines, which explains why the turbojet engine 100 according to the example of the invention includes inverters 190 and 190' for each motor without DC / DC converters. In this way, the electrical architecture of the turbojet engine is simplified, while the size of each of the motors 104 and 104' is reduced to one-quarter of its original size.

[0072] Figure 5 This demonstrates another result regarding the performance of the hybrid turbojet engine according to the invention, particularly compared to existing technologies.

[0073] Figure 4 It shows Figure 3 The curves are C1, C2, and C3. However, on the right-hand y-axis, the power is no longer represented, but rather torque in Nm.

[0074] Therefore, curve C40 shows the torque supplied by the first motor 104 as a function of the rotational speed of the low-pressure turbine 102 (in tr / mn). Curve C50 shows the torque supplied by the second motor 104' as a function of the rotational speed of the low-pressure turbine. Curves C40 and C50 are identical: therefore, the torque produced by each motor 104, 104' is the same. This is because the ratio is the same for each series T1, T2.

[0075] Curve C60 represents the torque supplied by the low-pressure turbine 102 at shaft a26 as a function of the rotational speed of the low-pressure turbine 102 (in tr / mn).

[0076] When switching from the first operating mode (low speed) to the second operating mode (high speed), the torque borne by the second motor 104' is equal to the torque of the low-pressure turbine 102 at constant power at a threshold speed (5000 rpm in the example), which is less than the torque associated with a speed of 1860 rpm, and further reduced to 1 / 4 of that torque. Therefore, it should be understood that the recovery torque of the second motor in the second operating mode is less than the torque associated with a speed of 1860 rpm (at a threshold speed of 5000 rpm in the example). Figure 4 The torque at the minimum speed of the low-pressure turbine observed in the study first decreases to 1860 / 5000 of that torque (i.e., practically 1 / 3), and further decreases to 1 / 4 of that torque (i.e., approximately 1 / 10.7 of that torque). Therefore, the mass of the components of the second motor 104' and its inverter 190' is reduced to approximately 1 / 9 of the mass of the BP motor and its associated electronic components in a conventional hybrid turbojet engine (i.e., without a transmission drive).

[0077] At low engine speeds, as can also be shown in our example, the mass of the components of the first motor 104 and its inverter 190 is reduced to about one-third the mass of the motor and its associated electronic components of a conventional hybrid turbojet engine (i.e., without a transmission drive).

[0078] Therefore, in order to cover the same speed range of the motor, the present invention has the advantage of reducing the mass and overall size of the motor and its control electronics.

[0079] It will be further noted that the present invention is not limited to the embodiments described above.

Claims

1. A hybrid turbojet engine (100), said hybrid turbojet engine comprising: -Low-pressure turbine (102); - A first motor (104) and a second motor (104'), the motors (104, 104') being configured to supply constant power together; - Input shaft (a26), which is configured to be driven by the low-pressure turbine (102); - A first output shaft (a64) and a second output shaft (a64'), the first output shaft being configured to drive the first motor (104) and the second output shaft being configured to drive the second motor (104'). - Used to obtain the rotational speed (ω) of the input shaft (a26). T Acquisition device (160); - A variable speed drive (106), the variable speed drive being used for rotational speed (ω) based on the input shaft (a26). T The driver (106) is used to adjust the rotational speed of each output shaft (a64, a64'), and includes: • First planetary gear system (T1), the first planetary gear system: - The input end includes a planet carrier (108), a gear ring (112) and at least one first planetary gear (110), the planet carrier being connected to the input shaft (a26), and the at least one first planetary gear being carried by the planet carrier (108) and engaging with the gear ring (112); - At the output end, a first sun gear (130) is included, which meshes with the at least one first planetary gear (110) and is centered on the first output shaft (a64), which is aligned with the input shaft (a26). The first system (T1) has a given first transmission ratio between the rotational speed of the first output shaft (a64) and the rotational speed of the input shaft (a26), and also a given first ratio between the gear ring (112) and the first sun gear (130); • Second planetary gear system (T2), the second planetary gear system: - The input end includes the gear ring (112) and at least one second planetary gear (120), the at least one second planetary gear engaging with the gear ring (112) and carried by a fixed shaft (AF). - A second sun gear (140) is included at the output end, which meshes with the second planetary gear (120) and is centered on the second output shaft (a64'), which is aligned with the input shaft (a26). The second system (T2) has a second transmission ratio defined between the rotational speed of the second output shaft (a64) and the rotational speed of the input shaft (a26), the second transmission ratio being less than the first transmission ratio defined for the first system (T1). The second system has a second ratio defined between the ring gear (112) and the second sun gear (130), the second ratio being the same as the first ratio defined for the first system (T1). • A locking device (MB) for locking the gear ring (112) in two operating modes, namely a first operating mode and a second operating mode. In the first operating mode, the gear ring (112) is locked and prevents any rotation of the second planetary gear (120) and the second motor (104'). In the second operating mode, the gear ring (112) is in a free state. • Electronic control unit (170), the electronic control unit is used to transfer the acquired rotational speed (ω) T ) and the predetermined threshold (ω) S When compared, the obtained rotational speed (ω) T ) is greater than the predetermined threshold (ω) S When the electronic control unit sends a control signal (S) to the locking device (MB), the electronic control unit sends the control signal (S) to the locking device (MB). C This allows the gear ring (112) to be in a free state, and sends a control signal to the first motor (104) to drive the first sun gear (130) at a constant speed.

2. The turbojet engine (100) according to claim 1, wherein, The first planetary gear train (T1) is configured such that the first gear ratio is equal to four and the first ratio is equal to three, and the second planetary gear train (T2) is configured such that the second gear ratio is at most equal to two and the second ratio is equal to three.

3. The turbojet engine (100) according to claim 1 or 2, comprising a fan (180) at the inlet of the turbojet engine (100) and connected to the input shaft (a26), the fan comprising a plurality of blades (182) having a fixed orientation.

4. The turbojet engine (100) according to any one of claims 1 to 3, wherein, Used to obtain the rotational speed (ω) of the input shaft (a26). T The acquisition device (160) is a speed sensor configured to measure the instantaneous rotational speed of the input shaft (a26).

5. The turbojet engine (100) according to any one of claims 1 to 4, wherein, The predetermined threshold (ω) S The value is defined as a function of the maximum speed. Preferably, the predetermined threshold is set to 5000 tr / mn. Preferably, for a gear ratio of four, the maximum speed is 20000 tr / mn.

6. The turbojet engine (100) according to any one of claims 1 to 5, wherein, The locking device (MB) for locking the gear ring (112) can be released to free the gear ring, and is a braking member arranged on the second output shaft (a64').

7. The turbojet engine (100) according to any one of claims 1 to 5, wherein, The locking device (MB) used to lock the gear ring (112) can be released to free the gear ring, and is a short-circuit torque generated by the second motor (104') on its own resistance.

8. The turbojet engine (100) according to any one of claims 1 to 7 further includes an electric inverter (190, 190') dedicated to each motor, without a DC-DC converter.

9. A method for controlling a turbojet engine (100) according to any one of claims 1 to 8, the method comprising the following steps: - Obtain the rotational speed (ω) of the input shaft (a26) described in (302). T ); -The obtained rotational speed (ω) T ) and the predetermined threshold (ω) S ) for comparison (304); -If the obtained rotational speed (ω) T If the value is greater than the predetermined threshold, a control signal (308) is sent to the locking device (MB) for locking the gear ring (112). c This allows the gear ring to be in a free state, and sends a control signal to the first motor (104) to drive the first sun gear (130) at a constant speed.

10. A computer program product (P) capable of being downloaded from a communication network and / or recorded on a computer-readable medium, characterized in that, When the program (P) is executed on the computer (170), the computer program product includes instructions for performing the steps of the method according to claim 9.

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