FR3132729A1 - Propulsion assembly for aircraft comprising a gas turbomachine and an electric machine with a cooling system comprising a main coupling member and associated method of use - Google Patents

Abstract

A propulsion unit (1) for an aircraft comprising at least one propulsion member (10), a gas turbine engine (T) configured to drive the propulsion member (10) in rotation, an electric machine (M), mounted downstream of the gas turbine engine (T), comprising a shaft (M1) integral in rotation with the gas turbine engine (T), the electric machine (M) being mounted in an enclosure (2) fed by a flow of cooling air ( FR) and at least one cooling system of the electric machine (M), mounted in the enclosure (2), comprising at least one ventilation member (3), at least one main coupling member (4) configured, according to a coupling position (P1), to couple the shaft (M1) and the ventilation member (3) in order to drive it in rotation and, according to a decoupling position (P2), to decouple the shaft (M1 ) and the ventilation member (3) so as not to cause it to rotate. Figure of the abstract: Figure 2

Description

Propulsion assembly for aircraft comprising a gas turbomachine and an electric machine with a cooling system comprising a main coupling member and associated method of use

The present invention relates to the field of propulsion assemblies for aircraft, in particular, a propulsion assembly comprising a gas turbomachine associated with an electric machine which can operate as a motor to provide electric propulsion or as a generator to power for example an electric battery or a network electrical of the aircraft.

In a known manner, with reference to the , we know a propulsion assembly 100 comprising a gas turbomachine T driving a propulsion member 10 to ensure the propulsion of an aircraft. The gas turbomachine T extends axially along an axis X and is double flow. For this purpose, the gas turbomachine T comprises a primary stream V1 in which circulates a primary flow F1 coming from the combustion chamber (not shown) and a secondary stream V2 in which circulates a secondary flow F2 which has been accelerated without circulating by the combustion chamber. The gas turbomachine T comprises a low pressure body LP, comprising a low pressure compressor 11 and a low pressure turbine 14, and a high pressure body HP, comprising a high pressure compressor 12 and a high pressure turbine 13.

The propulsion assembly 100 also comprises an electric machine M, mounted downstream of the gas turbomachine T, comprising a shaft, connected to the low pressure body BP or to the high pressure body HP of the gas turbomachine T. An electric machine M contains electrical components that must be cooled during use. Cooling is particularly critical given that the electric machine M is positioned near the primary stream V1 whose primary flow F1, coming from the combustion chamber, has a high temperature.

For this purpose, it has been proposed to mount the electric machine M in an enclosure, 101 for example of a conical shape called a "plug", and to supply it with a flow of cooling air FR coming from the secondary stream V2, that is to say, from the secondary flow F2 whose temperature is lower than that of the primary flow F1.

In practice, the flow rate of the cooling air flow FR depends on the flow rate of the secondary flow F2 which itself depends on the speed of the gas turbomachine T. In fact, this presents a disadvantage given that the cooling requirements of the electric machine M are uncorrelated with the speed of the gas turbomachine T.

In addition, the cooling of an electrical machine M must be carried out evenly in order to avoid the appearance of hot spots. In practice, the zones of the electric machine M which are far from the cooling air flow inlet FR in the enclosure 101 are insufficiently cooled, which affects the overall efficiency of the electric machine M or its operating range. use.

The invention thus aims to eliminate at least some of these drawbacks by proposing a propulsion assembly allowing optimal cooling of an electric machine for any operating regime of the turbomachine.

PRESENTATION OF THE INVENTION

• Au moins un organe propulsif configuré pour participer à la propulsion de l’aéronef par accélération d’un flux d’air circulant selon un axe longitudinal d’amont vers l’aval,
• Une turbomachine à gaz configurée pour entrainer en rotation l’organe propulsif, la turbomachine à gaz comprenant un corps basse pression, un corps haute pression et une chambre de combustion, la turbomachine à gaz étant à double flux et comprenant une veine primaire dans laquelle circule un flux primaire issu de la chambre de combustion, et une veine secondaire dans laquelle circule un flux secondaire contournant la chambre de combustion,
• Une machine électrique, montée, en aval de la turbomachine à gaz, comportant un arbre solidaire en rotation de la turbomachine à gaz, la machine électrique étant montée dans une enceinte alimentée par un flux d’air de refroidissement issu de la veine secondaire, et
• Au moins un système de refroidissement de la machine électrique, monté dans l’enceinte, comprenant :
  • au moins un organe de ventilation configuré pour être entrainé en rotation dans l’enceinte par l’arbre,
  • Au moins un organe de couplage principal configuré, selon une position de couplage, pour coupler l’arbre et l’organe de ventilation afin de l’entrainer en rotation et, selon une position de découplage, pour découpler l’arbre et l’organe de ventilation afin de ne pas l’entrainer en rotation.

The invention relates to a propulsion assembly for an aircraft comprising:

• At least one propulsion member configured to participate in the propulsion of the aircraft by accelerating an air flow circulating along a longitudinal axis from upstream to downstream,
• A gas turbomachine configured to rotate the propulsion member, the gas turbomachine comprising a low pressure body, a high pressure body and a combustion chamber, the gas turbomachine being dual flow and comprising a primary vein in which circulates a primary flow coming from the combustion chamber, and a secondary stream in which a secondary flow bypassing the combustion chamber circulates,
• An electric machine, mounted downstream of the gas turbomachine, comprising a shaft integral in rotation with the gas turbomachine, the electric machine being mounted in an enclosure supplied by a flow of cooling air coming from the secondary stream, and
• At least one cooling system for the electric machine, mounted in the enclosure, comprising:
  • at least one ventilation member configured to be rotated in the enclosure by the shaft,
  • At least one main coupling member configured, according to a coupling position, to couple the shaft and the ventilation member in order to cause it to rotate and, according to an uncoupling position, to decouple the shaft and the member ventilation so as not to cause it to rotate.

This advantageously makes it possible to ventilate the electrical machine and/or its enclosure by force and with sufficient air flow. Advantageously, even when the gas turbomachine is off, the electric machine can be used as a motor to rotate the ventilation member and cool the enclosure. In addition, thanks to the main coupling member, the ventilation can be decoupled during certain operating phases of the gas turbomachine, in particular, at very high speed and at low speed.

In the prior art, the cooling air flow depends directly on the speed of the gas turbomachine. As a result, the cooling air flow does not always match cooling needs. Thanks to the main coupling member, it is possible to decouple the ventilation member to drive it at a rotation speed corresponding to the cooling needs.

Preferably, the shaft having a rotation speed, the main coupling member is configured to switch to the decoupling position when the rotation speed is greater than a predetermined high threshold. This helps protect the ventilation system which is likely to be damaged at very high speed. This avoids the need for a heavy and bulky ventilation unit that can be driven at high speed.

Preferably, the shaft having a rotation speed, the main coupling member is configured to switch to the decoupling position when the rotation speed is lower than a predetermined low threshold. At low shaft speed, forced ventilation is insufficient. The main coupling member makes it possible to achieve decoupling in order to enable drive independent of that of the shaft of the electric machine.

Preferably, the main coupling member is chosen from the set comprising: a powder visco-coupler, a mechanical disc clutch, a centrifugal coupler, a freewheel, a magnetic coupler, a splined shaft coupled to an actuator longitudinal. Such a main coupling member makes it possible to switch position precisely and automatically for a predetermined speed range.

According to a preferred aspect, the cooling system comprises an auxiliary power source configured to rotate the ventilation member independently of the shaft. Thus, advantageously, the ventilation member can be rotated at a predefined speed and controlled by the auxiliary source when the shaft is rotated at low speed which is potentially insufficient to ensure optimal cooling functions.

Preferably, the cooling system comprises an auxiliary coupling member, mounted between the auxiliary power source and said ventilation member, configured, in a coupling position, to couple the auxiliary power source and said ventilation member in order to 'rotate and, according to a decoupling position, to decouple the auxiliary power source and said ventilation member so as not to cause it to rotate. Thus, the main coupling member and the auxiliary coupling member ensure that the ventilation member is only driven by one driving source at a time, which limits the risk of damage.

Preferably, the cooling system comprises at least one multiplication member, mounted between the shaft and the ventilation member, configured to rotate said ventilation member at a speed different from that of the speed of said shaft. Preferably, the multiplication member has a multiplication coefficient greater than 1 so as to accelerate the ventilation member and obtain improved ventilation performance. This is particularly relevant when the shaft is driven at a low speed.

According to one aspect, the multiplication member is mounted between the main coupling member and the ventilation member. According to another aspect, the multiplication member is mounted between the shaft and the main coupling member.

Preferably, the assembly comprises at least one overall coupling member, mounted between the shaft and the gas turbomachine, configured, according to a coupling position, to couple the gas turbomachine to the shaft to secure them in rotation and , according to a decoupling position, to decouple the gas turbomachine from the shaft. Such a global coupling member makes it possible to couple/decouple the electric machine from the gas turbomachine as needed. This is particularly advantageous to avoid drawing mechanical power from the gas turbomachine in certain operating modes.

Preferably, the cooling system comprises at least one ventilation member mounted downstream of the electrical machine. This advantageously makes it possible to generate a suction of the cooling air flow while maximizing the use of the space available in the “plug” enclosure. The electric machine can thus be mounted as close as possible to the gas turbomachine, with more advantageous aerodynamic lines.

Preferably, the cooling system comprises at least one first ventilation member mounted upstream of the electrical machine and at least one second ventilation member mounted downstream of the electrical machine. Such a “tandem” assembly makes it possible to optimize the space available in the enclosure while allowing optimal circulation of the cooling air flow. This also makes it possible to define two compression stages in order to limit the compression rate per stage in order to avoid operating the stages in degraded operating conditions which could lead to suboptimal cooling.

According to one aspect of the invention, the enclosure comprises a peripheral separation wall defining at least one interior sub-enclosure, in which the electrical machine is mounted, and an exterior sub-enclosure. At least one first ventilation member is mounted in the outer sub-enclosure and at least one second ventilation member is mounted in the inner sub-enclosure so as to optimally cool each sub-enclosure. The outer sub-enclosure advantageously fulfills a thermal barrier function by protecting the inner sub-enclosure in which the electrical machine is mounted against the heat coming from the primary vein.

The invention also relates to a method of using a propulsion assembly for an aircraft as presented previously, the shaft being coupled to the ventilation member in order to cause it to rotate, the method comprising a step consisting of decoupling the ventilation member of the shaft so as not to cause it to rotate. Thus, for certain operating modes of the propulsion assembly, the ventilation member can be decoupled to avoid any risk of damage or improve ventilation.

• découpler l’organe de ventilation de l’arbre lorsque la vitesse de rotation de l’arbre est inférieure à un seuil bas prédéterminé
• entrainer en rotation l’organe de ventilation par une source de puissance auxiliaire de manière indépendante de l’arbre.

The invention further relates to a method of using a propulsion assembly for an aircraft as presented previously, the shaft being coupled to the ventilation member in order to cause it to rotate, the method comprising steps consisting of:

• decouple the ventilation member from the shaft when the rotation speed of the shaft is lower than a predetermined low threshold
• drive the ventilation member into rotation by an auxiliary power source independently of the shaft.

Thus, at low speed, the auxiliary power source takes over from the shaft to ensure satisfactory ventilation.

• découpler l’arbre de la turbomachine à gaz, et
• l’organe de ventilation étant couplé à l’arbre, entrainer en rotation l’organe de ventilation par rotation de l’arbre de manière à refroidir la machine électrique.

The invention also relates to a method of using a propulsion assembly for an aircraft as presented previously, the method comprising steps, according to an engine mode, consisting of:

• decouple the shaft from the gas turbomachine, and
• the ventilation member being coupled to the shaft, rotate the ventilation member by rotating the shaft so as to cool the electrical machine.

Thus, when the gas turbomachine is off, the electric machine can be used in engine mode to cool the electric machine given that the cooling air flow, coming from the secondary flow, has a low flow rate.

• coupler l’arbre à la turbomachine à gaz de manière à ce que la machine électrique génère de l’énergie électrique, l’organe de ventilation étant découplé de l’arbre.

The invention also relates to a method of using a propulsion assembly for an aircraft as presented previously, the method comprising steps, according to a generating mode, consisting of:

• couple the shaft to the gas turbomachine so that the electric machine generates electrical energy, the ventilation member being decoupled from the shaft.

Thus, when the gas turbomachine is in operation, the electric machine can be used in generator mode to generate electrical energy. No mechanical power is advantageously taken from the shaft for ventilation in order to maximize generation. Advantageously, when the gas turbomachine is in operation the flow of cooling air, coming from the secondary flow, has a high flow rate which is sufficient to ensure cooling.

The invention relates to a method of using a propulsion assembly for an aircraft as presented previously, in which the shaft of the electric machine rotates in opposite directions in generator mode and in motor mode.

PRESENTATION OF FIGURES

The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects .

There is a schematic representation of a propulsion assembly according to the prior art.

There is a schematic representation of a propulsion assembly according to a first embodiment of the invention.

There is a close schematic representation of the electrical machine of the .

There is a schematic representation of the coupling/decoupling positions as a function of the speed of the electric machine shaft.

There is a schematic representation of a propulsion assembly according to a second embodiment of the invention.

There is a schematic representation of a variant of the second embodiment of the invention of the .

There is a schematic representation of a propulsion assembly according to a third embodiment of the invention according to a first variant.

There is a schematic representation of a propulsion assembly according to the third embodiment of the invention according to a second variant.

There is a schematic representation of a propulsion assembly according to a fourth embodiment of the invention.

There is a schematic representation of a propulsion assembly according to a fifth embodiment of the invention.

There is a schematic representation of a propulsion assembly according to a first variant of the fifth embodiment of the invention.

There is a schematic representation of a propulsion assembly according to a second variant of the fifth embodiment of the invention.

There and the are schematic representations of the propulsion assembly according to the second embodiment of the invention during coupling/decoupling of the main coupling member.

There and the are schematic representations of the propulsion assembly according to the fourth embodiment of the invention during coupling/decoupling of the overall coupling member.

It should be noted that the figures set out the invention in detail to implement the invention, said figures being able of course to be used to better define the invention if necessary.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a propulsion assembly for an aircraft, the aircraft may comprise one or more propulsion assemblies to enable its propulsion.

In reference to the , there is shown in a longitudinal sectional view a propulsion assembly 1 according to a first embodiment of the invention. The propulsion assembly 1 comprises a propulsion member 10 configured to participate in the propulsion of the aircraft by accelerating an air flow F circulating along a longitudinal axis X from upstream to downstream. In this example, the propulsion member 10 is in the form of a fan which is ducted but it goes without saying that the invention also applies to a non-ducted propeller.

In reference to the , the gas turbomachine T is configured to rotate the propulsion member 10. The gas turbomachine T comprises a low pressure body LP, a high pressure body HP and a combustion chamber (not shown). In particular, the low pressure body LP comprises a low pressure compressor 11 and a low pressure turbine 13 while the high pressure body HP comprises a high pressure compressor 12 and a high pressure turbine 14. The gas turbomachine T is double flow and comprises a primary stream V1, in which circulates a primary flow F1 coming from the combustion chamber, and a secondary stream V2 in which circulates a secondary flow F2 bypassing the combustion chamber, in particular, accelerated by the propulsion member 10.

Such a gas turbomachine T is known to those skilled in the art and will not be presented in further detail.

According to the invention, the propulsion assembly 1 comprises an electric machine M, mounted downstream of the gas turbomachine T, comprising a shaft M1 integral in rotation with the gas turbomachine T, in particular, with the low pressure body BP or of the HP high pressure body. The electric machine M is configured to operate, on the one hand, in generator mode in order to generate electrical energy from a mechanical torque received on its shaft M1 and, on the other hand, in motor mode to drive the shaft M1 from an electrical source (battery, electrical network, etc.). It nevertheless goes without saying that the invention applies to an electric machine M operating only in a generator mode or a motor mode. The general structure of an electrical machine M is known to those skilled in the art and will not be presented in further detail. In this example, the electric machine M comprises a movable rotor part, secured to the shaft M1, and a fixed stator part (not shown). Subsequently, the shaft M1 of the electric machine M has a rotation speed VM.

In reference to the , the electric machine M is mounted in an enclosure 2 supplied by a flow of cooling air FR coming from the secondary stream V2, that is to say, coming from the secondary flow F2 which is, by nature, colder than the primary flow F1. Enclosure 2 preferably has a conical shape but it goes without saying that it could be different.

Likewise, he is represented in the an enclosure 2 which is open at its downstream end for the evacuation of the cooling air flow FR but it goes without saying that the evacuation could be carried out in a different way.

In this example, the cooling air flow FR is injected at an upstream part of enclosure 2 via a cooling pipe (not shown) connected to the secondary stream V2. The cooling line could come in various forms.

According to the invention, with reference to Figures 2 and 3, the propulsion assembly 1 comprises a cooling system of the electric machine M, mounted in the enclosure 2, which comprises several ventilation members 3 configured to be rotated in enclosure 2 via shaft M1. Thus, the cooling air flow FR is accelerated directly in the enclosure 2, which makes it possible, on the one hand, to promote the capture of calories and, on the other hand, to allow uniform cooling of the electrical machine M independently of the injection position of the cooling air flow FR into enclosure 2.

Preferably, the ventilation members 3 are configured to accelerate the flow of cooling air FR in a peripheral manner in order to cool the exterior surface of the electric machine M in a homogeneous manner. The calories generated by the electric machine M are thus captured in a practical manner.

The ventilation member 3 can be in the form of a fan, a bladed wheel or a pump.

• selon une position de couplage P1, pour coupler l’arbre M1 et l’organe de ventilation 3 afin de l’entrainer en rotation et,
• selon une position de découplage P2, pour découpler l’arbre M1 et l’organe de ventilation 3 afin de ne pas l’entrainer en rotation.

According to the invention, with reference to Figures 2 and 3, the cooling system comprises a main coupling member 4 configured:

• according to a coupling position P1, to couple the shaft M1 and the ventilation member 3 in order to cause it to rotate and,
• according to a decoupling position P2, to decouple the shaft M1 and the ventilation member 3 so as not to cause it to rotate.

Such a main coupling member 4 is advantageous since it ensures cooling in coupling mode when the rotation speed VM of the electric machine M is adapted. As soon as this rotation speed VM is no longer suitable, the main coupling member 4 makes it possible to carry out a decoupling allowing either to completely stop the rotation of the ventilation member 3, or to drive the ventilation member 3 at a rotation speed different from that of the shaft M1 and more adapted to the cooling needs of the electric machine M as will be presented subsequently.

Thanks to the main coupling member, the ventilation can be stopped during certain operating phases of the gas turbomachine, in particular, during phases where the speed of the M1 shaft is too high or too low.

The main coupling member 4 is preferably configured to automatically couple/decouple depending on the speed of the member which drives it, in particular, of the shaft M1. Thus, the coupling/decoupling steps can be conveniently associated with speed ranges for which the cooling air flow requirements FR are different. Preferably, the main coupling member 4 is chosen from the set comprising: a visco-powder coupler, a mechanical disc clutch, a centrifugal coupler, a freewheel, a magnetic coupler.

As illustrated in , the main coupling member 4 is configured to switch to the decoupling position P2 when the rotation speed VM is greater than a predetermined high threshold S2, preferably between 500 rpm and 30,000 rpm. Advantageously, high-speed decoupling makes it possible to avoid rotating the ventilation member 3 at excessive speeds likely to damage it.

Still with reference to the , the main coupling member 4 is configured to switch to the decoupling position P2 when the rotation speed VM is less than a predetermined low threshold S1, preferably between 0 rpm and 20,000 rpm. Advantageously, low speed decoupling makes it possible to drive the ventilation member 3 by another source at a higher speed to ensure optimal cooling as will be presented subsequently.

According to a second embodiment, with reference to the , the cooling system includes an auxiliary power source 5 configured to rotate the ventilation member 3 independently of the shaft M1. Such an auxiliary power source 5 is of great interest when the main coupling member 4 is in the decoupling position P2, the ventilation member 3 being able to be driven at a speed different from that of the shaft M1, in particular, at a rotation speed determined by the auxiliary power source 5. The use of an auxiliary power source 5 makes it possible to drive the ventilation member when the power on the shaft M1 is non-existent or insufficient, as for example at low speed or when the turbomachine is off. The auxiliary power source 5 can be in various forms, in particular, a low-power electric machine.

According to a variant, with reference to the , the cooling system comprises an auxiliary coupling member 4', mounted between the auxiliary power source 5 and said ventilation member 3, configured, according to a coupling position, to couple the auxiliary power source 5 and said ventilation member 3 in order to cause it to rotate and, according to a decoupling position, to decouple the auxiliary power source 5 and said ventilation member 3 so as not to cause it to rotate.

Advantageously, the main coupling member 4 and the auxiliary coupling member 4' synergistically enable the ventilation member 3 to be driven entirely independently. Preferably, when driven by the shaft M1, the main coupling member 4 is in the coupling position while the auxiliary coupling member 4' is in the decoupling position ( ). Conversely, when driven by the auxiliary source 5, the main coupling member 4 is in the decoupling position while the auxiliary coupling member 4' is in the coupling position ( ).

Preferably, the auxiliary coupling member 4' is of the same nature as the main coupling member 4 presented previously. Preferably, the auxiliary coupling member 4' and the main coupling member 4 are configured not to be in coupling mode simultaneously. For this purpose, the speed ranges associated with the coupling modes of the coupling members 4, 4' are chosen appropriately.

With reference to Figures 7 and 8, according to a third embodiment, the propulsion assembly 1 comprises a multiplication member 6, mounted between the shaft M1 and the ventilation member 3, configured to rotate said ventilation member 3 at a speed different from that of the speed of said shaft M1, preferably higher. Such a multiplication member 6 advantageously makes it possible to increase the flow rate of the cooling air flow FR while using the rotation of the shaft M1 adapted to the motor/generator operating mode of the electric machine M. This is particularly advantageous when the speed of the shaft M1 is too low compared to the cooling needs.

Such a multiplication member 6 makes it possible to obtain a greater flow rate without resorting to an auxiliary power source 5. It nevertheless goes without saying that an auxiliary power source 5 could be used with a multiplication member 6, the forms of realization being compatible together. In this last configuration, a so-called differential assembly makes it possible to drive the ventilation unit at speeds independent of the speeds of the main shaft (variable multiplication rate) and to ensure optimal ventilation at all points in the operating range.

The multiplication member 6 can be presented in various forms, in particular, an epicyclic train. A multiplication member 6 is associated with a multiplication coefficient which is preferably greater than 1. This multiplication coefficient can be fixed or variable.

According to a first aspect, with reference to the , the multiplication member 6 is mounted between the main coupling member 4 and the ventilation member 3. This configuration makes it possible to use coupling members operating at low speed. It also makes it possible to isolate the multiplier if its reliability can impact the overall reliability of the system.

According to a second aspect, with reference to the , the multiplication member 6 is mounted between the shaft M1 and the main coupling member 4. This configuration makes it possible to implement coupling members operating preferably at high speed.

In reference to the , according to a fourth embodiment, the propulsion assembly 1 comprises an overall coupling member 7, mounted between the shaft M1 and the gas turbomachine T, configured, according to a coupling position, to couple the gas turbomachine T to the shaft M1 to secure them in rotation and, according to a decoupling position, to decouple the gas turbomachine T from the shaft M1. Thus, the overall coupling member 7 makes it possible to transmit mechanical power between the shaft M1 and the gas turbomachine T, in particular, with the low pressure body BP or the high pressure body HP. Preferably, the overall coupling member 7 is of the same nature as the main coupling member 4 presented previously.

Preferably, when the electric machine M is in generator mode, the overall coupling member 7 is in the coupling position. When the electric machine M is in motor mode, the overall coupling member 7 can be in the coupling position if the electric machine M wishes to contribute to propulsion or be in the decoupling position if the electric machine M wishes to provide a non-propelling torque , in particular, for ventilation as will be presented later.

In the previous embodiments, the shaft M1 extends only upstream so as to allow the ventilation members 3 to extend upstream of the electrical machine M to cool it optimally.

Alternatively, with reference to the , according to a fifth embodiment, the shaft M1 also extends downstream and the ventilation members 3 extend downstream of the electric machine M to allow air to be sucked in and bring the electric machine M closer together. as close as possible to the gas turbomachine T to gain compactness. In addition, there are space constraints which are less downstream to allow the installation of a larger and more efficient ventilation unit 3. This finally makes it possible to optimize the use of the “plug” space of the turbomachine in order to maintain advantageous aerodynamic lines for the turbomachine.

According to a first variant, with reference to the , ventilation members 3 are positioned upstream and downstream (tandem position) of the electric machine M to improve cooling and optimize the available space while bringing the electric machine M as close as possible to the gas turbomachine T. This also makes it possible to form two compression stages and optimize the circulation of the FR cooling air flow. Such a configuration makes it possible to reduce the compression rate per ventilation stage and to avoid entering into degraded ventilation modes which could cause suboptimal cooling. On the , there is shown a main coupling member 4 associated with each ventilation member 3 but it goes without saying that a single ventilation member 3 could be associated with a main coupling member 4.

According to a second variant, with reference to the , the enclosure 2 comprises a peripheral separation wall 8 defining at least one interior sub-enclosure 21, in which the electrical machine M is mounted, and an exterior sub-enclosure 22. At least one ventilation member 3 is mounted in rotation in each sub-enclosure 21, 22 so as to ensure distinct cooling. The external sub-enclosure 22 advantageously makes it possible to form a thermal barrier, between the primary vein V1 and the electrical machine M, which can be cooled independently.

In this example, the peripheral separation wall 8 comprises an upstream part 8a and a downstream part 8b which are separated by a slot 80 in which extends the ventilation member 3 which is mounted in the external sub-enclosure 22 in order to ventilate it.

On the , for the sake of clarity, there is not shown a main coupling member 4 associated with each ventilation member 3 but it goes without saying that such a main coupling member 4 could be associated with one, several or each member ventilation 3.

Preferably, the ventilation member 3 associated with the outer sub-enclosure 22 is mounted on an upstream portion of the shaft M1 of the electric machine M and the ventilation member 3 associated with the inner sub-enclosure 21 is mounted on a downstream portion of the shaft M1 of the electric machine M in order to optimize size and compactness. However, it goes without saying that the ventilation members 3 could be positioned all upstream or all downstream.

• découpler l’organe de ventilation 3 de l’arbre M1 afin de ne pas l’entrainer en rotation, en particulier, en commutant l’organe de couplage principal 4 en mode de découplage, lorsque la vitesse de rotation VM de l’arbre M1 est inférieure au seuil bas prédéterminé S1,
• entrainer en rotation l’organe de ventilation 3 par une source de puissance auxiliaire 5 de manière indépendante de l’arbre M1 comme illustré à la .

An example of implementation of a method of use according to the invention will now be presented with reference to Figures 13 and 14. With reference to the , the shaft M1 is coupled to the ventilation member 3 in order to cause it to rotate. The method comprises a step consisting of:

• decouple the ventilation member 3 from the shaft M1 so as not to cause it to rotate, in particular, by switching the main coupling member 4 to decoupling mode, when the rotation speed VM of the shaft M1 is lower than the predetermined low threshold S1,
• drive the ventilation member 3 into rotation by an auxiliary power source 5 independently of the shaft M1 as illustrated in .

This advantageously makes it possible to provide a greater flow of cooling air FR with the auxiliary power source 5 when the rotation speed VM of the shaft M1 is low. Preferably, the main coupling member 4 is in the coupling position then switched to the decoupling position. Conversely, the auxiliary coupling member 4' is in the decoupling position then switched to the coupling position. Thanks to this example of implementation, cooling is improved even when the rotation speed VM is low, for example, when the aircraft is in taxi phase or moving at low speed.

• découpler l’arbre M1 de la turbomachine à gaz T par commutation de l’organe de couplage global 7 en position de découplage, et
• l’organe de ventilation 3 étant couplé à l’arbre M1 par l’organe de couplage principal 4 en mode de couplage, entrainer en rotation l’organe de ventilation 3 par rotation de l’arbre M1 de manière à refroidir la machine électrique M.

According to another aspect of the invention, the electric machine M is used in generator mode and receives mechanical energy via the gas turbomachine T thanks to the overall coupling member 7 which is in the coupling position. According to an example of implementation with reference to Figures 15 and 16, the method comprises steps, according to a motor mode of the electric machine M, consisting of:

• decouple the shaft M1 from the gas turbomachine T by switching the overall coupling member 7 to the decoupling position, and
• the ventilation member 3 being coupled to the shaft M1 by the main coupling member 4 in coupling mode, rotate the ventilation member 3 by rotation of the shaft M1 so as to cool the electric machine M .

In this example of implementation, the electric machine M can be dedicated to cooling, which is advantageous for effectively ventilating the enclosure 2, in particular, when the gas turbomachine T is off.

• coupler l’arbre M1 à la turbomachine à gaz T, par commutation de l’organe de couplage global 7 en position de couplage, de manière à ce que la machine électrique M génère de l’énergie électrique, l’organe de ventilation 3 étant découplé à l’arbre M1.

According to another example of implementation, the method comprises steps, according to a generating mode of the electric machine M, consisting of:

• couple the shaft M1 to the gas turbomachine T, by switching the overall coupling member 7 into the coupling position, so that the electric machine M generates electrical energy, the ventilation member 3 being decoupled from the M1 shaft.

Such an example of implementation makes it possible to use the mechanical energy supplied by the gas turbomachine T essentially for the generation of electrical energy, no power being taken for cooling. This configuration is advantageous in cases where the ventilation system could fail, or in cases where the supply conditions in the secondary flow are sufficient to ventilate the electrical machine without the need to compress the air further thanks to the ventilation system .

Preferably, the shaft M1 of the electric machine M rotates in opposite directions in generator mode and in motor mode allowing the use of “freewheel” type coupling systems for ventilation driven solely by the electric machine.

It goes without saying that the multiplication member 6 could also be used in each of the configurations, in particular, when the speed VM is not sufficient to ensure optimal cooling.

Claims (18)

Propulsion assembly (1) for aircraft comprising:

• At least one propulsion member (10) configured to participate in the propulsion of the aircraft by accelerating an air flow (F) circulating along a longitudinal axis (X) from upstream to downstream,
• A gas turbomachine (T) configured to rotate the propulsion member (10), the gas turbomachine (T) comprising a low pressure body (LP), a high pressure body (HP) and a combustion chamber, the gas turbomachine (T) being dual flow and comprising a primary stream (V1) in which a primary flow (F1) from the combustion chamber circulates, and a secondary stream (V2) in which a secondary flow (F2) circulates bypassing the combustion chamber,
• An electric machine (M), mounted downstream of the gas turbomachine (T), comprising a shaft (M1) integral in rotation with the gas turbomachine (T), the electric machine (M) being mounted in an enclosure ( 2) supplied by a flow of cooling air (FR) coming from the secondary vein (V2), and
• At least one cooling system for the electric machine (M), mounted in the enclosure (2), comprising:
  • at least one ventilation member (3) configured to be rotated in the enclosure (2) by the shaft (M1),
  • At least one main coupling member (4) configured, according to a coupling position (P1), to couple the shaft (M1) and the ventilation member (3) in order to drive it in rotation and, according to a position decoupling (P2), to decouple the shaft (M1) and the ventilation member (3) so as not to cause it to rotate.

Propulsion assembly (1) according to claim 1, in which, the shaft (M1) having a rotational speed (VM), the main coupling member (4) is configured to switch to the decoupling position (P2) when the rotation speed (VM) is greater than a predetermined high threshold (S2). Propulsion assembly (1) according to one of claims 1 and 2, in which, the shaft (M1) having a rotational speed (VM), the main coupling member (4) is configured to switch to the decoupling position (P2) when the rotation speed (VM) is less than a predetermined low threshold (S1). Propulsion assembly (1) according to one of claims 1 to 3, in which the main coupling member (4) is chosen from the set comprising: a powder visco-coupler, a mechanical disc clutch, a coupler centrifugal, a freewheel, a magnetic coupler. Propulsion assembly (1) according to one of claims 1 to 4, in which the cooling system comprises an auxiliary power source (5) configured to rotate the ventilation member (3) independently of the shaft (M1). Propulsion assembly (1) according to claim 5, in which the cooling system comprises an auxiliary coupling member (4'), mounted between the auxiliary power source (5) and said ventilation member (3), configured, according to a coupling position, for coupling the auxiliary power source (5) and said ventilation member (3) in order to cause it to rotate and, according to a decoupling position, for decoupling the auxiliary power source (5) and said ventilation member (3) so as not to cause it to rotate. Propulsion assembly (1) according to one of claims 1 to 6, in which the cooling system comprises at least one multiplication member (6), mounted between the shaft (M1) and the ventilation member (3) , configured to rotate said ventilation member (3) at a speed different from that of the speed of said shaft (M1). Propulsion assembly (1) according to claim 7, in which the multiplication member (6) is mounted between the main coupling member (4) and the ventilation member (3). Propulsion assembly (1) according to claim 7, in which the multiplication member (6) is mounted between the shaft (M1) and the main coupling member (4). Propulsion assembly (1) according to one of claims 1 to 9, comprising at least one overall coupling member (7), mounted between the shaft (M1) and the gas turbomachine (T), configured in a position of coupling, to couple the gas turbomachine (T) to the shaft (M1) to secure them in rotation and, according to an uncoupling position, to decouple the gas turbomachine (T) from the shaft (M1). Propulsion assembly (1) according to one of claims 1 to 10, in which the cooling system comprises at least one ventilation member (3) mounted downstream of the electrical machine (M). Propulsion assembly (1) according to one of claims 1 to 11, in which the cooling system comprises at least one first ventilation member (3) mounted upstream of the electric machine (M) and at least one second ventilation member (1). ventilation (3) mounted downstream of the electric machine (M). Propulsion assembly (1) according to one of claims 1 to 12, in which, the enclosure (2) comprising a peripheral separation wall (8) defining at least one interior sub-enclosure (21), in which the electric machine (M), and an outer sub-enclosure (22), at least one first ventilation member (3) is mounted in the outer sub-enclosure (22) and at least one second ventilation member (3) is mounted in the interior sub-enclosure (21). Method of using a propulsion assembly (1) for an aircraft according to one of claims 1 to 13, the shaft (M1) being coupled to the ventilation member (3) in order to cause it to rotate, the process comprising a step consisting of:

• decouple the ventilation member (3) from the shaft (M1) so as not to cause it to rotate.

Method of using a propulsion assembly (1) for an aircraft according to claims 3 and 5, the shaft (M1) being coupled to the ventilation member (3) in order to cause it to rotate, the method comprising steps consisting of:

• decouple the ventilation member (3) from the shaft (M1) when the rotation speed (VM) of the shaft (M1) is less than a predetermined low threshold (S1)
• drive the ventilation member (3) into rotation by an auxiliary power source (5) independently of the shaft (M1).

Method of using a propulsion assembly (1) for an aircraft according to claim 10, the method comprising steps, according to an engine mode, consisting of:

• decouple the shaft (M1) from the gas turbomachine (T), and
• the ventilation member (3) being coupled to the shaft (M1), rotate the ventilation member (3) by rotating the shaft (M1) so as to cool the electric machine (M).

Method of using a propulsion assembly (1) for an aircraft according to claim 10, the method comprising steps, in a generating mode, consisting of:

• couple the shaft (M1) to the gas turbomachine (T) so that the electric machine generates electrical energy, the ventilation member (3) being decoupled from the shaft (M1).

Method of using a propulsion assembly (1) for an aircraft according to claims 16 and 17, in which:

• the shaft (M1) of the electric machine (M) rotates in opposite directions in generator mode and in motor mode.