EP3870827A1

EP3870827A1 - Turbomachine with unducted twin propellers

Info

Publication number: EP3870827A1
Application number: EP19813119.5A
Authority: EP
Inventors: Nicolas Jérôme Jean TANTOT; Anthony BINDER; Mario Antoine LAMBEY
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2018-10-26
Filing date: 2019-10-25
Publication date: 2021-09-01
Also published as: FR3087849B1; CA3117485A1; WO2020084271A1; CN112930436A; US11987369B2; FR3087849A1; US20210403169A1

Abstract

The invention concerns an aircraft turbomachine comprising an outer housing (2) delimiting, with an inner hub (3), a flow path (1) for a gas stream in which a low-pressure turbine is arranged, configured to rotate a low-pressure shaft; the turbomachine comprising, in the direction of flow of the gas stream, a first propeller (31); and a second propeller (32) downstream from the first propeller, the first propeller (31) being rotated by the low-pressure shaft and the second propeller being rotated by an electric motor (70), the second propeller (32) further being arranged at a distance of between 1.5 and 4 chord lengths (LC1) from the first propeller (31) defined between the respective pitch axes (A31, A32) of each of the first and second propellers.

Description

l

Turbomachine with non-faired double propellers

GENERAL TECHNICAL AREA

The invention relates to the field of turbomachinery and more particularly relates to turbomachines of the non-faired type (in English, "open rotor").

STATE OF THE ART

Turbomachinery of the non-faired type are part of the context of having architectures aimed at maximizing energy efficiency, while exhibiting an ability to integrate (geometrically and aerodynamically) correctly with the aircraft.

Several solutions are known to fall within this context.

A first solution is a turbomachine with a pair of counter-rotating propellers (in English, "counter rotating open rotor" (CROR)) as described for example in document FR 2 941 492. Such a turbomachine comprises an air inlet and a vein circulation of a flow delimited by an external casing and an internal hub. The vein passes through a gas generator, here with a double body which feeds a turbine driving two counter-rotating propellers. In this document, these two counter-rotating propellers are integral in rotation with a gas generator turbine. The turbomachine of this document has the particular advantage of combining an excellent propulsive efficiency linked to a generation of thrust via propellers with very low pressure ratio, and of external dimensions smaller than those of a turbomachine with single propeller of same thrust, facilitating its physical integration on the aircraft. This architecture based on a pair of counter-rotating propellers, however, has a certain number of limitations, in particular due to the complexity of the subsystems necessary for its implementation (double pitch setting system for the propellers, rotating casings under each propeller rotor , ...).

Another solution, as a variant to the doublet architecture of counter-rotating propellers is the USF architecture (in English, "Unducted Single Fan"), comprising a propeller rotor, and a stator with variable setting in its wake, intended to straighten the residual gyration of the propeller rotor. This variant can be seen as a CROR type architecture whose rotation of the downstream propeller is stopped. If it has greater architectural simplicity, this solution however suffers from a lower low-pressure module efficiency than the CROR solution, and requires larger diameters to maintain a rotor load equivalent to that of the CROR solution (this rotor load conditioning at first order the perceived noise levels).

Finally, both of the architectural solutions mentioned above have the following drawbacks:

1. The quasi-bijectivity of the operation of the gas generator and the propulsive parts: when the need for thrust requested by the aircraft is reduced (for the end of cruise and idle phases), all of the rotating parts operate at low energy levels (low pressure ratio, low rotational speeds), which proves detrimental to the proper performance of each component, particularly within the gas generator, significantly degrading the overall performance of the propulsion system.

2. The difficulty in extracting significant mechanical power from the shafts of the turbomachine without major impact on the operability of the compressors.

In fact, in a context of growing needs for mechanical power extraction for increasingly electric aircraft cells, it is necessary to adapt the turbomachine architectures so as to drive electric generators of increasing capacity. This leads to increasing the stresses on the compressors, leading to the necessary oversizing of the latter, detrimental to their absolute performance.

PRESENTATION OF THE INVENTION

An object of the invention is to provide a turbomachine architecture with two non-faired propellers which does not have the aforementioned drawbacks.

To this end, the invention proposes, according to a first aspect, a turbomachine of an aircraft comprising an external casing delimiting with an internal hub, a flow stream of a gas flow in which is arranged a low pressure turbine configured for rotating a low pressure shaft; said turbomachine comprising, in the direction of flow of the gas flow, a first propeller; and a second propeller downstream of the first propeller, the first propeller being rotated by said low pressure shaft and the second propeller being rotated by an electric motor, the second propeller being further disposed at a distance between 1, 5 and 4 lengths of strings from the first propeller defined between the respective timing axes of each of the first and second propellers.

The invention according to the first aspect is advantageously supplemented by the following characteristics, taken alone or in any of their technically possible combinations:

- The second propeller has an external diameter of 0.8 and 1 times the external diameter of the first propeller.

- The turbomachine comprising an internal hub from which the blades of the second propeller extend, the second propeller having a ratio of the radius of the hub / external radius of the blade between 0.22 and 0.40.

- The second propeller has a length of rope between 0.8 and 1.2 times the length of the rope of the first propeller.

- The turbomachine comprises a first electric motor / generator configured to contribute to driving a low pressure shaft in rotation, the first propeller being driven in rotation by said low pressure shaft by means of a reducer.

The propulsion system comprises or is connected to an energy storage unit connected to the first and / or second electric motor / generator, the energy storage unit preferably having a capacity of between 200 and 500 kWh.

The first and second propellers are arranged in front of the inlet of the gas flow circulation stream.

The first and second propellers are arranged downstream of the stream and outside the stream of gas flow.

The turbomachine comprises a gas generator, a control unit of the second engine / electric generator, a control unit of the stall angle of the second propeller, said control units being configured to control the second engine and the angle of timing of the second propeller according to one of the following operating modes:

a first operating mode requiring a given first propulsive power, first operating mode in which the second motor / generator rotates the second propeller in the opposite direction to the first, and the pitch angle of the second propeller is controlled to that the second propeller provides between 20% and 40% of said given propellant power;

a second operating mode requiring a second given propulsive power, second operating mode according to which the second motor / generator does not rotate the second propeller and the setting angle of the second propeller is controlled so as to maximize the 'efficiency of an aerodynamic coupling with the first propeller;

- A third operating mode requiring a third given propulsive power, third mode according to which the gas generator and the first propeller are regulated so as to provide a propulsive power greater than the third given propellant power;

a fourth operating mode according to which the setting angle of the first propeller 31 is positioned at a negative angle and according to which the second propeller is controlled in neutral setting, the gas generator operating in a high pressure operating range between 90 % and 100%, fourth mode according to which the first propeller is in reverse thrust and the second propeller allows an inversion of the air flow supplying the first propeller;

- A fifth operating mode according to which an overall thrust level is maintained by an exclusively electrical energy supply of the second propeller rotor for a given duration;

a sixth operating mode according to which the second propeller has a malfunction:

o if the control of the stall angle of the second propeller is defective then, the stall angle of the second propeller is blocked; o if the second engine / generator of the second propeller is defective then the second propeller is ordered to coast.

In the third operating mode the pitch angle of the second propeller can be controlled so as to obtain an angle of incidence of the blades less than 0 °, in order to rotate the second propeller, in an opposite direction of rotation in the direction of rotation of the first propeller. It is also possible to control the second propeller so as to obtain an angle of incidence of the blades greater than 0 °, in order to drive the second propeller in rotation, in a direction of rotation identical to the direction of rotation of the first propeller.

Thanks to this configuration of variable interactions between the two propellers, the performance of the turbomachine is increased.

In addition, it is possible to control the first and second propeller in different ways depending on the operating modes of the turbomachine.

PRESENTATION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which should be read with reference to the appended drawings in which:

Figure 1 illustrates, schematically, a turbomachine according to a first configuration according to the invention;

- Figure 2 illustrates, schematically, an alternative to the turbomachine according to the first configuration;

FIG. 3 illustrates, diagrammatically, a turbomachine according to a second configuration in accordance with the invention;

FIG. 4 illustrates the arrangement of the propellers of the turbomachine;

FIG. 5 illustrates modes of operation of the turbomachine according to the invention;

- Figure 6 illustrates, schematically, a first mode of operation of the turbomachine according to the invention, corresponding to takeoff of the aircraft;

FIG. 7 schematically illustrates a second mode of operation of the turbomachine according to the invention, corresponding to the cruise of the aircraft;

FIG. 8 illustrates, diagrammatically, a third mode of operation of the turbomachine according to the invention, according to a first embodiment, corresponding to an idle, descent of the aircraft;

- Figure 9 illustrates, schematically, the arrow of a propeller of the turbomachine according to the invention;

- Figure 10 illustrates, schematically, the leading edge of a propeller of the turbomachine according to the invention; - Figure 11 illustrates, schematically, a third mode of operation of the turbomachine according to the invention, according to a second embodiment, corresponding to an idle, descent of the aircraft;

In all of the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

In connection with FIGS. 1, 2 and 3, a turbomachine of an aircraft comprises an annular space 1 for the flow of a gas flow, delimited by an external casing 2 and an internal hub 3. Such an annular space 1 is called, hereinafter, a stream of gas flow.

The flow stream 1 of the gas flow can comprise from upstream to downstream, in the direction of flow of the gas flow (along the axis AA ′ and represented by arrow F), a low pressure compressor 1 1, a high pressure compressor 12, a combustion chamber 13, a high pressure turbine 14 and a low pressure turbine 15.

The low pressure turbine 15 is configured to rotate a low pressure shaft 25 while the high pressure turbine 14 is configured to rotate a high pressure shaft 24.

The turbomachine comprises, in the direction of flow of the gases, a first propeller 31 and a second propeller 32 downstream of the first propeller 31. The first and second propellers are not faired (type architecture, according to the English terminology "open rotor ”).

The first and second propellers 31, 32 extend from the internal hub 3 and include several blades extending from this internal hub 3.

Two configurations are described below, a first configuration in relation to FIGS. 1 and 2 and a second configuration in relation to FIG. 3.

According to the first configuration, the first and second propellers 31, 32 are arranged in front of the inlet of the stream 1 for circulation of the gas flow.

Alternatively, according to the second configuration, the first and second propellers 31, 32 are arranged at the outlet of the flow stream of the gas flow. In particular, the first and second propellers 31, 32 are arranged downstream and externally behind and above the stream 1 for circulation of the gas flow.

SUBSTITUTE SHEET (RULE 26> The two configurations differ from each other by the position of the first and second propeller relative to the inlet and outlet of the stream 1 for the flow of gas (the inlet and the sort being defined in the direction gas flow).

Advantageously according to one or other of the two configurations described above, the second propeller 32 is disposed at a distance between 1, 5 and 4 lengths of rope from the first propeller defined between respective chock axes of each of the first and second propellers 31, 32 as described below in relation to FIG. 4.

FIG. 4 illustrates the arrangement of the first 31 and second 32 propellers along the longitudinal axis AA ’of the turbomachine. As illustrated in this figure, it is specified that the length of rope LCi is understood (i = 1 for the first propeller, i = 2 for the second propeller) the length of the rope 42, that is to say the length of the segment (or rope) between the leading edge 41 and the trailing edge 43 of a propeller. In addition, the spacing between the two propellers 31, 32 is taken between the timing axes A31, A32 respective of each of the propellers 31, 32. In this figure, the propellers are spaced three lengths of LC strings.

Such spacing between the two propellers 31, 32 makes it possible to have an aerodynamic coupling which can contribute effectively to the propulsion of the turbomachine.

Also, this spacing results from the aeroacoustic compromise between:

• A distance between the two propellers large enough to limit the intensity of the lines of acoustic interaction between the propellers;

• A distance between the two propellers small enough to minimize the spread of the speed profiles at the output of the first propeller (upstream propeller) and encourage their immediate re-use by deflecting the second propeller (downstream propeller).

In addition, this spacing takes into account the need to integrate the pitch change mechanisms of each propeller, mechanisms requiring a certain axial volume.

The second propeller 32 advantageously has the following geometric characteristics:

An external diameter between 0.8 and 1 times the external diameter of the first propeller 31 upstream; A hub ratio (internal radius / external radius of the blade ratio) of between 0.22 and 0.40;

An average chord between 0.8 and 1.2, twice the average chord of the first propeller 31 upstream.

Advantageously, the first propeller 31 is rotated by the low pressure turbine 15, by means of the low pressure shaft 25 and a first reducer 50 only, or else by the combination of a first motor / electric generator 60 and the low pressure turbine 15, and this by means of the same first reducer 50. In this way the first motor / generator 60 makes it possible to compensate occasionally for the deficiencies of the low / pressure shaft 25.

In this variant, in the event of failure of the contribution of the low pressure turbine contributing to the energy supply of the first propeller 31, the motor / generator 60 provides part of the energy supply expected for the first propeller 31.

This configuration illustrated in Figure 2 also applies to the configuration of Figure 3 where the propellers are located at the outlet of the annular space for circulation of the gas flow.

The second propeller 32 is itself only driven in rotation by a second electric motor / generator 70 by means of a second reducer 80.

The first reduction gear 50 and the second reduction gear 80 are advantageously: mechanical (of the epicyclic or planetary type) having a reduction ratio in rotation regime preferably between 8 and 12; or - electromagnetic.

Depending on the configuration, the turbomachine can comprise a first electric motor / generator 60 and a second electric motor / generator 70 which can operate as an "engine" but also as an "electric generator".

The propulsion system therefore includes an energy storage unit 90 connected to the first and / or second electric motor / generator, the energy storage unit preferably having a capacity of between 200 and 500 kWh . When the electric motor / generator 60, 70 operates as a motor, the storage unit 90 is a power source for the electric motor / generator 60, 70 while when the propellers 31, 32 are not driven by the motor / electric generator 60, 70, the electric motor / generator allows the storage unit 90 to be recharged.

Indeed, the electric motor / generator 60, 70 can make use of the operating modes during which it is not used as an "engine" to recharge the storage unit 90.

Whatever the configuration, the turbomachine can comprise, associated with each propeller, a control unit for the propeller setting angle (units UC1 and UC'1 in the figures) which is characterized by

for the first propeller, a clearance preferably between -30 ° and + 90 °;

for the second propeller, a clearance preferably limited to the positive pitch angles, typically 0 ° to + 90 ° / maximum 0 ° to +1 10 °.

We use the terminology "propeller pitch" here to refer to the timing of each blade of the propeller.

The second propeller 32 is advantageously used in different ways according to several operating modes of the propulsion system of the aircraft. As will be described (in relation to FIG. 5), the second propeller 32 can have several functions to contribute to the operation of the aircraft according to these different configurations.

Thus, the turbomachine comprises a unit UC2 for controlling the second motor / generator associated with the second propeller 32, the unit UC2 for controlling the second motor / generator 70 making it possible to continuously control the supply of electric power for this second motor / generator between the extreme cases of a zero supply and a supply corresponding to the maximum second design power of the engine / generator 70.

A first operating mode M1 corresponds to takeoff / climb of the aircraft, mode during which the turbomachine needs a high propulsive power called given propulsive power:

The second motor / generator 70 is in "motor" mode and uses the energy of the storage unit 90 as power supply in order to drive the second propeller 32 in rotation; The stall angle of the second propeller is adjusted so that the second propeller 32 provides thrust, up to approximately 20 to 40% of the given propulsive power (i.e. ~ 5 MW maximum for a short / medium aircraft class -courrier), and so that the angle of incidence of the blades Ai is greater than 0 ° (as illustrated in FIG. 6);

- The gas generator operates in a high pressure reduced speed range (N2K) of between 90 and 100% depending on the flow of fuel injected into the combustion chamber.

During this first operating mode M1, the rotation of the second propeller 32 makes it possible to reduce the level of energy required on the first propeller 31 to ensure the expected overall thrust of the propulsive system, which makes it possible to size the diameter of the first propeller 31 to a lower value than what the state of the art would require in the absence of assistance in supplying thrust via the propeller 32. Such a reduction in diameter makes it possible to have a first propeller 31 which is easily integrated while maintaining a high energy efficiency of the overall propulsion system.

In addition, the energy level required on the low pressure shaft is reduced, as is that expected from the gas generator, which has the consequence of dimensioning the annular gas flow space to a lower value adapted to this reduced level of energy expected. A benefit on the mass of the turbomachine is obtained with improved performance as well as a reduction in noise pollution due to the ejection of gases at the outlet of the gas generator.

A second operating mode M2 corresponds to cruising of the aircraft, mode during which the turbomachine needs intermediate propulsive power:

The second motor / generator 70 is unused, the second propeller 32 does not receive mechanical power, it is in "freewheeling";

The setting angle of the second propeller 32 is controlled in conjunction with the setting angle of the first propeller 31 so as to maximize the propulsive efficiency of its combination with the first propeller 31 upstream, always so that the angle incidence of the blades Ai is greater than 0 ° (as illustrated in FIG. 7). The second propeller 32 therefore functions as a rectifier. Its rotation speed is free and depends on the aerodynamic coupling with the first propeller 31: either stopped, or in very slow rotation. The generator gas and the first propeller 31 are regulated so as to respond exactly to the expected propellant need. The timing angles are derived from previous aerodynamic predictions.

The gas generator operates in a high pressure reduced speed range between 80 and 90%

During this second operating mode M2, the propulsive efficiency of the first propeller 31 is maximized by upgrading its residual gyration. The gyration of the flow (undesirable rotation because it does not contribute to the increase in flow speed along the propulsive axis) from the first propeller is recovered by the interaction with the blades of the second propeller (here almost immobile), and revalued in the form of a velocity vector of the flow oriented along the main propulsive axis.

A third operating mode M3 corresponds to an idling, lowering of the aircraft, mode during which the turbomachine needs a low power:

The gas generator and the first propeller 31 are regulated at an operating point greater than the real propellant need;

The energy generated in excess manifests itself in the form of an enthalpy excess and a gyration at the output of the first propeller 31. This excess energy is recovered on the second propeller 32 which is then rotated and operates in mode. wind turbine via the choice of a suitable stall angle. The mechanical energy thus recovered from the second propeller 32 feeds the second motor / generator 70 which then operates in generator mode, recharging the storage unit 90.

The gas generator operates in a high pressure reduced speed range of between 90 and 100% depending on the flow of fuel injected into the combustion chamber.

During this third operating mode M3, the energy decoupling of the propellant requirement and the operating point of the gas generator and of the first propeller 31 makes it possible to position the latter on much more favorable efficiency zones than those achieved on a configuration classic slow motion. This also makes it possible to move away from the critical areas of compressor operability by positioning the gas generator at medium / high power levels for which the operability is less critical than at idle conditions. This operating mode M3 can be obtained according to two embodiments:

In a first embodiment (as illustrated in FIG. 8), the setting angle of the second propeller 32 is modified so that the angle of incidence of the blades Ai is less than 0 °. This modification of the angle of incidence of the blades Ai has the effect of obtaining a lift coefficient less than 0, and thus makes it possible to rotate the second propeller 32 in a direction of rotation opposite to the direction of rotation of the first propeller 31. This embodiment thus makes it possible to keep the same direction of rotation of the second propeller 32 as in the other operating modes, and thus avoids the complexification of the gearbox. However, it involves modifying the geometry of the propeller by reducing the arrow Fl, which corresponds to the maximum distance between the rope and the line of camber (shown in Figure 9). In addition, in order to avoid delamination, it is necessary to design blades with a wide leading edge Ba (shown in FIG. 10);

In a second embodiment (as illustrated in FIG. 11), the setting angle of the second propeller 32 is modified so that the angle of incidence of the blades Ai is greater than 0 °. This modification of the angle of incidence of the blades Ai makes it possible to rotate the second propeller 32 in the same direction of rotation as the first propeller 31. This embodiment involves designing a gearbox allowing the second propeller 32 to rotate in both directions, on the other hand it does not imply a modification of the geometry of the propeller since its aerodynamic operation remains the same as in the other operating modes.

A fourth operating mode M4 corresponding to the braking of the aircraft:

The timing of the first propeller 31 is positioned at a negative angle;

The second propeller 32 is left in neutral timing (in English, "windmilling") which makes it possible to generate no mechanical power on the propeller;

The gas generator operates in a high pressure reduced speed range between 90 and 100%. During this fourth operating mode M4, there is a reverse thrust on the first propeller 31 and the second propeller 32 has a timing chosen so as to allow an inversion of air flow supplying the first propeller 31.

A fifth operating mode corresponds to a malfunction of the first propeller 31 or to a malfunction of the gas generator:

The setting angle of the first propeller 31 is positioned in neutral setting ("windmilling") if the malfunction of this first propeller allows it, or maintained at its setting value at the time of occurrence of the malfunction

- The stall angle of the second propeller 32 is positioned in the full traction position, that is to say according to a stall angle similar to that of the first propeller 31 when it is operating under conditions to provide maximum power;

The second motor / generator 70 is controlled to supply maximum power to the second propeller 32.

During this fifth operating mode M5, a minimum overall thrust level is maintained for a certain period of time (by means of the supply of the second propeller 32 in order to maintain a traction capacity, the thrust is then generated exclusively by the second rotor 32), duration conditioned by the capacity of the second electric motor / generator 70 and the power available in the storage unit 90 which is associated with it. This fifth operating mode makes it possible to minimize the impact of a loss of thrust from the first propeller 31 or a loss of primary energy supply from the gas generator.

A sixth operating mode M6 also corresponds to a malfunction, but here of the second propeller 32:

- If the malfunction comes from the fact that it is not possible to control the setting angle of the second propeller 32 then the setting angle of the second propeller 32 is kept locked in its last occupied position;

- If the malfunction comes from the second motor / generator 70 then the second propeller 32 is left to coast as long as the timing range allows to provide a thrust;

Such a sixth operating mode M6 makes it possible to have a turbomachine architecture which is robust to the failure of the second propeller. As already mentioned, the first electric motor / generator 60 associated with the first propeller 31 can complement the rotation by the low pressure turbine 15 (see FIG. 2).

This configuration allows:

· The assistance of the low pressure shaft (first propeller 31 upstream) by the first electric motor / generator 60;

o In the case of the first operating mode: take-off assistance, together with the assistance already produced by the second propeller 32;

o In the event of failure of the gas generator during the fifth operating mode: ability to drive the first propeller for a period limited by the capacity of the energy storage device;

• Real-time energy transfer between the second propeller 32 and the low-pressure shaft: even when the storage device linked to the first engine / generator, in "generator" mode is empty, the second propeller 32 can thus be supplied with energy mechanical as required;

• A recharging profile for the first motor / generator in "motor" mode which is more efficient since it is directly connected to the low pressure turbine.

Claims

1. Turbomachine of an aircraft comprising an external casing (2) delimiting with an internal hub (3), a stream (1) for circulation of a gas flow in which is arranged a low pressure turbine configured to drive in rotation a low pressure shaft; said turbomachine comprising, in the direction of flow of the gas flow, a first propeller (31); and a second propeller (32) downstream of the first propeller, the first propeller (31) being rotated by said low pressure shaft and the second propeller being rotated by an electric motor (70), the second propeller (32 ) being furthermore arranged at a distance between

1, 5 and 4 lengths of strings (LC1) of the first propeller (31) defined between respective timing axes (A31, A32) of each of the first and second propellers.

2. A turbomachine according to claim 1, in which the second propeller (32) has an external diameter of 0.8 and 1 times the external diameter of the first propeller (31).

3. Turbomachine according to one of the preceding claims, in which the turbomachine comprising an internal hub (3) from which blades of the second propeller (32) extend, the second propeller (32) having a radius ratio of the hub , external radius of the blade between 0.22 and 0.40.

4. Turbomachine according to one of the preceding claims, in which the second propeller (32) has a length of rope (LC2) of between 0.8 and 1.2 times the length of rope (LC1) of the first propeller (31 ).

5. Turbomachine according to one of claims 1 to 4, comprising a first electric motor / generator (60) configured to contribute to driving in rotation a low pressure shaft, the first propeller (31) being driven in rotation by said low pressure shaft (25) via a reducer (50).

6. Turbomachine according to one of claims 1 to 5, comprising a storage unit (90) of energy connected to the first and / or second motor / generator electric (60, 70), the energy storage unit preferably having a capacity of between 200 and 500 kWh.

7. Turbomachine according to one of the preceding claims, in which the first and second propellers (31, 32) are arranged in front of the inlet of the stream (1) for circulation of the gas flow.

8. Turbomachine according to one of claims 1 to 6, in which the first and second propellers (31, 32) are arranged downstream of the stream (1) and outside the stream (1) for the circulation of the gas flow .

9. Propulsion system comprising a turbomachine according to one of claims 1 to 5, and further comprising a storage unit (90) of energy connected to the first and / or second motor / electric generator (60, 70), the energy storage unit preferably having a capacity between 200 and 500 kWh.

10. Turbomachine according to one of the preceding claims, comprising a gas generator, a unit (uc2) for controlling the second electric motor / generator (70), a unit (uc2 ') for controlling the setting angle of the second propeller (32), said control units being configured to control the second motor and the setting angle of the second propeller according to one of the following operating modes:

a first operating mode (M1) requiring a first given propulsive power, first operating mode according to which the second motor / generator rotates the second propeller in the opposite direction to the first, and the stall angle of the second propeller is controlled so that the second propeller provides between 20% and 40% of said given propellant power;

a second operating mode (M2) requiring a given second propulsive power, second operating mode according to which the second motor / generator does not rotate the second propeller and the setting angle of the second propeller is controlled so as to maximize aerodynamic coupling with the first propeller; a third operating mode (M3) requiring a given third propulsive power, third mode according to which the gas generator and the first propeller are regulated so as to provide a propulsive power greater than the third given propellant power;

a fourth operating mode (M4) according to which the setting angle of the first propeller 31 is positioned at a negative angle and according to which the second propeller is controlled in neutral setting, the gas generator operating in a high pressure operating range included between 90% and 100%, fourth mode according to which the first propeller is in reverse thrust and the second propeller allows an inversion of the air flow supplying the first propeller;

a fifth operating mode (M5) according to which an overall thrust level is maintained by an exclusively electrical energy supply for a given duration;

A sixth operating mode (M6) according to which the second propeller has a malfunction:

o If the setting of the setting angle of the second propeller is defective then, the setting angle of the second propeller is blocked; o If the second engine / generator of the second propeller is defective then the second propeller is ordered to coast.

1 1. Turbomachine according to claim 10, in which in the third operating mode (M3) the setting angle of the second propeller is controlled so as to obtain an angle of incidence of the blades less than 0 °, in order to drive in rotation the second propeller, in a direction of rotation opposite to the direction of rotation of the first propeller.

12. The turbomachine according to claim 10, in which in the third operating mode (M3) the setting angle of the second propeller is controlled so as to obtain an angle of incidence of the blades greater than 0 °, in order to cause in rotation the second propeller, in a direction of rotation identical to the direction of rotation of the first propeller.