Propulsion systems for aircraft

Abstract

The invention relates to a propulsion system (1, 1') for an aircraft, comprising a rotor (2) and a nacelle fairing (3), the nacelle fairing extending around the rotor relative to an axis (X) and comprising an upstream portion and a downstream portion (20), the upstream portion forming an inlet cross section of the nacelle fairing, the downstream end (21) of the downstream portion (20) forming an outlet cross section (BF) of the nacelle fairing (3); characterised in that the downstream portion (20) comprises a radial inner wall (20a) and a radial outer wall (20b). The outer wall (20b), the radial inner wall (20a) and the radial outer wall (20b) are made of deformable shape memory material, and the wall (20b) has a piston actuator mechanism (23, 23'), each actuator mechanism can be actuated independently of the other actuator mechanisms, and is designed to cooperate with a device (24, 24') embedded in the inner surface (20b') of the wall (20b) to deform the wall (20b) along a radial direction relative to the axis (X) under the action of a predetermined displacement command.

Description

Technical Field

[0001] The present invention relates to the field of propulsion systems for aircraft. In particular, the present invention relates to a propulsion system capable of providing a lateral thrust component.

[0002] The invention also relates to an aircraft comprising such a propulsion system. Background Art

[0003] The technical background includes in particular documents US 2011 / 030380 A1, EP 2184481 A2, US 5328098 A1 and FR 2310471 A1.

[0004] A propulsion system for an aircraft includes at least one rotor or propeller including a plurality of blades mounted on a rotating shaft.

[0005] There are aircraft, in particular vertical take-off and landing (VTOL) aircraft, in which the aircraft has a single rotor propulsion system when the aircraft includes only one rotor, or a counter-rotating rotor propulsion system when the aircraft includes rotors combined in pairs and rotating in opposite directions.

[0006] These propulsion systems either have a shrouded rotor (whereby the rotor is surrounded by an annular nacelle fairing) or a free rotor, the propulsion system, in particular and the rotor (free rotor or shrouded rotor), being mountable on a pivot axis such that the propulsion system can be oriented so that the rotor can be oriented between a vertical position and a horizontal position, for example a vertical orientation for vertical take-off and landing and a horizontal orientation for forward flight or airplane flight mode.

[0007] Shrouded rotors offer several interesting advantages, such as:

[0008] - During direct start, the rotor sound signature is significantly reduced;

[0009] - Protect the rotor blades from surrounding obstacles;

[0010] - Improved rotor performance, especially when the vehicle is hovering or moving at low speeds.

[0011] However, VTOL aircraft with shrouded rotors do not have the same maneuverability as conventional helicopters, especially in hovering flight.

[0012] For conventional helicopters, altitude and position corrections can be made in the X, Y, Z aviation standard reference trihedron by:

[0013] - correction of the roll axis X (the axis about which the helicopter rotates around its longitudinal axis) by acting on the cyclic pitch (the direction of the thrust acting on the rotor, here in a plane perpendicular to the axis X) to the left or to the right;

[0014] - correction of the pitch axis Y (the axis of the helicopter about its transverse axis) by acting forward (nose down) or aft (nose up) on the cyclic pitch (the direction of the thrust acting on the rotor, here in a plane perpendicular to the Y axis);

[0015] - correction of the yaw axis Z (the axis of rotation around its vertical axis in the horizontal plane of the helicopter) by acting on the rudder (thrust acting on the anti-torque rotor of the helicopter);

[0016] - Correction of the longitudinal translation along the axis X (longitudinal axis) of the reference trihedron in aviation standards by commanding the cyclic / collective pitch (direction of thrust acting on the rotor, here forward or backward);

[0017] - Correction of the transverse translation of the axis Y (transverse axis) of the reference trihedron according to aeronautical standards by commanding the cyclic / collective pitch (direction of thrust acting on the rotor, here the direction of thrust acting on the rotor towards the left or towards the right);

[0018] The vertical translation along the reference axis Z is corrected by commands for collective pitch up and down (thrust acting on the rotor, setting the pitch change: command to pull upward).

[0019] Of course, coordinated corrections of collective pitch and rudder, well known to pilots, are required to counter the inductive and torque effects of the loss of lift component.

[0020] For VTOL aircraft with shrouded rotors, positioning corrections or corrections that enable wind gusts to be counteracted in hovering flight are often complicated, rendering the flight uncomfortable for the passengers of the aircraft.

[0021] For example, in the case of a quadrotor aircraft (i.e. an aircraft with four rotors), in order to make a correction in the direction of the reference axis X, it is necessary to tilt the aircraft forward around the reference axis Y (along the pitch axis), then make a correction to the position reached (e.g. to counteract gusts of wind), and quickly return to the intermediate position, which is called "calm". Similarly, in order to make a correction in the direction of the reference axis Y, it is necessary to tilt the aircraft toward and around the reference axis X (along the roll axis), i.e. roll over, then make a correction to the position reached, and quickly return to the intermediate position. For such a quadrotor aircraft, when transporting passengers, the passengers may experience forward / backward swaying and / or right / left swaying.

[0022] A gas turbine engine is proposed, comprising a two-dimensional nozzle comprising a flexible plate capable of changing position under the action of a cylinder to regulate the exhaust gas of the engine.

[0023] Gas turbine engines comprising variable nozzle geometry have also been proposed, such that the exit surface area of ​​the nozzle can be varied.

[0024] Therefore, these proposed solutions propose a nozzle in which a two-dimensional vector thrust technology is implemented.

[0025] However, none of the proposed solutions proposes to implement three-dimensional thrust vectoring technology in the nacelle fairing of the propulsion system, and in particular, none of the proposed solutions proposes to guide the secondary flow generated by the rotor in the VTOL mode of using the rotor.

[0026] Therefore, it is necessary to provide a simple and effective solution to the above problems.

[0027] The object of the present invention is to provide a solution making it possible to improve the handling of an aircraft of the VTOL type while reducing the weight and aerodynamic penalty effects associated with flight commands.

[0028] In particular, the present invention proposes to improve the maneuverability of a VTOL aircraft by providing a propulsion system capable of providing a thrust component transverse to the axis of the rotor. Summary of the invention

[0029] To this end, the present invention relates to a propulsion system for an aircraft, the propulsion system comprising at least one rotor and a nacelle fairing, the nacelle fairing extending around the at least one rotor relative to the rotation axis of the rotor, the nacelle fairing comprising an upstream section and a downstream section, the upstream section forming an inlet cross-section of the nacelle fairing, and the downstream end of the downstream section forming an outlet cross-section of the nacelle fairing; characterized in that the downstream section comprises a radial inner wall and a radial outer wall, the radial inner wall and the radial outer wall being made of a deformable shape memory material, and the radial outer wall comprising a plurality of actuator mechanisms having at least one cylinder, each actuator mechanism being capable of operating independently of the other actuator mechanisms and being configured to cooperate with a device embedded in the inner surface of the radial outer wall to deform the radial outer wall in a radial direction relative to the rotation axis under the action of a predetermined displacement command.

[0030] The propulsion system according to the invention may have a single rotor or counter-rotating rotors mounted in a fixed nacelle or a pivoting nacelle with a through or offset pivot axis.

[0031] According to the present invention, the fairing is composed of a semi-deformable shape memory material at its air outlet and is composed of a plurality of actuator mechanisms including cylinders, the actuator mechanisms being configured to automatically change the shape of the nacelle, thereby changing the direction of the air flow at the outlet of the nacelle, so as to control the aircraft on which the nacelle is installed.

[0032] Advantageously, the profile of the fairing has a semi-rigid downstream portion, the size and shape of the trailing edge outlet cross-section of the semi-rigid downstream portion can be changed so that under the action of a controlled device, the trailing edge outlet cross-section can be laterally oriented to form a flow duct that produces a thrust with a lateral component (called vector thrust or directional thrust).

[0033] Therefore, the propulsion system according to the invention makes it possible to improve the maneuverability of an aircraft equipped with it, in particular during maneuvers at low forward speeds (such as take-off and landing), while minimizing the noise pollution caused by the rotor of the propulsion system and ensuring the safety of the rotor through the presence of a nacelle fairing.

[0034] In fact, the shape of the fairing is constantly adjusted according to the deflection of the controlled thrust to obtain the precise arrangement of the aircraft.The profile of the fairing can thus be oriented transversely according to the mechanical constraints of flight sought in VTOL mode, so as to generate a thrust component perpendicular to the rotor axis.

[0035] Advantageously, an actuator mechanism with a cylinder enables a relatively rigid realization of the rear portion of the fairing and an activation with a short response time.

[0036] During the flight phases in airplane mode, the actuator mechanism with cylinders which is useful during phases at low forward speeds can be deactivated.

[0037] According to an embodiment, the device comprises a plurality of prisms distributed in at least one annular row on the inner surface of the radially outer wall.

[0038] Advantageously, a plurality of prisms may be arranged angularly equidistantly on the inner surface of the radially outer wall.

[0039] In an embodiment, the plurality of prismatic bodies are actuated by a cylinder via at least one annular element.

[0040] Advantageously, the cylinder angles are arranged angularly equidistantly in the downstream section.

[0041] According to an embodiment, a plurality of actuator mechanisms having at least one cylinder include: a first actuator mechanism having at least one cylinder, wherein the cylinder is configured to cooperate with the device to deform the radial outer wall along a first radial direction relative to the rotation axis under the action of a predetermined shift command; and a second actuator mechanism having at least one cylinder, wherein the cylinder is configured to cooperate with the device to deform the radial outer wall along a second direction opposite to the first direction under the action of a predetermined shift command.

[0042] Advantageously, the propulsion system further comprises a reinforcing bridge connecting the radially inner wall and the radially outer wall of the downstream section and making it possible to ensure that the distance between the radially inner wall and the radially outer wall of the downstream section is substantially constant.

[0043] The nacelle fairing may include an upstream section and a middle section, the upstream section forming an inlet cross section of the nacelle fairing, and the middle section connecting the upstream section and the downstream section.

[0044] Advantageously, the middle section is rigid and connected to the engine of the propulsion system by at least one rod, thus providing the nacelle fairing of the propulsion system with a rigid structure that ensures a protective function.

[0045] The invention also relates to an aircraft, characterized in that it comprises at least one propulsion system having at least one of the above-mentioned characteristics, the propulsion system being mounted to pivot on the aircraft via a pivot axis which is offset from the rotor or passes through the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention will be better understood and other details, features and advantages thereof will become more apparent from the following description made by way of non-limiting example and with reference to the accompanying drawings, in which:

[0047] [ Figure 1A ] Figure 1A is a schematic perspective view of a first embodiment of a propulsion system, the propulsion system being shown having a nacelle mounted on an offset pivot axis, the propulsion system being in a horizontal position;

[0048] [ Figure 1B ] Figure 1B is with Figure 1A A similar view showing the propulsion system in a vertical position;

[0049] [ Figure 1C ] Figure 1C is a schematic perspective view of a second embodiment of a propulsion system, the propulsion system being shown having a nacelle mounted on a through-going pivot axis, the propulsion system being in a horizontal position;

[0050] [ Figure 2 ] Figure 2 is a schematic diagram of a longitudinal cross section of a propulsion system according to the invention, the downstream section of the nacelle fairing of the propulsion system being in a symmetrical thrust (ie axial thrust) mode;

[0051] [ Figure 3-4 ] Figure 3 and Figure 4 is a propulsion system according to the invention similar to Figure 2 A view of a downstream section of a nacelle fairing of the propulsion system in an asymmetric thrust mode;

[0052] [ Figure 5 ] Figure 5 is a schematic rear view of an embodiment of an actuator mechanism according to the present invention in an axial thrust mode;

[0053] [ Figure 6-7 ] Figure 6 and Figure 7 is a schematic rear view of an embodiment of an actuator mechanism according to the present invention in an asymmetric thrust mode; and

[0054] [ Figure 8 ] Figure 8 is a schematic cross-sectional view of a propulsion system according to another embodiment of the present invention, with a downstream section of a nacelle fairing of the propulsion system in an axial thrust mode.

[0055] Elements having the same function in different exemplary embodiments are provided with the same reference symbols in the figures. DETAILED DESCRIPTION

[0056] In the present disclosure, the terms "axial", "inner" and "outer" are used with reference to the axis of rotation of the propulsion system according to the invention.

[0057] The propulsion system typically includes:

[0058] - Nacelle;

[0059] - Engines and their command and control systems;

[0060] - and in the case of propeller propulsion or rotor propulsion, a propeller or one or more rotors.

[0061] The nacelle is the element that enables the engine to be integrated with the aircraft. It consists of:

[0062] - nacelle fairing (capable of covering the engine in order to cover the rotor, capture the air flow during the operation of the aircraft, generate propulsion, reverse the thrust on the propulsion system, etc.);

[0063] - Equipment installed on the engine (e.g. Engine Assembly Unit - EBU, including electrical, hydraulic and pneumatic networks); and

[0064] - Systems attached to an aircraft.

[0065] Figure 1A and Figure 1B A first embodiment of an aircraft propulsion system 1 according to the invention is shown in a simplified manner.

[0066] Here, the propulsion system 1 comprises at least one rotor 2 and a nacelle fairing 3 extending around said at least one rotor 2 relative to the axis of rotation X of the rotor 2. Advantageously, the fairing 3 acts as a sound barrier by its shape and material. The propulsion system 1 can be fixedly mounted on the aircraft. The propulsion system 1 can also be mounted on a pivot axis 4 offset from the axis of rotation X of the rotor 2. The pivot axis 4 is attached to the propulsion system 1 on the one hand by any means and to the aircraft on the other hand and enables the propulsion system 1 to be oriented on the aircraft, allowing the propulsion system 1 to be moved about the pivot axis 4 according to the arrow F1 by known actuators. Figure 1A The horizontal position shown and Figure 1B The vehicle is tilted between the vertical positions shown. This tilt enables the vehicle to switch from a conventional aircraft mode to a VTOL or helicopter mode.

[0067] The rotors 2 of the propulsion system 1 are connected to the aircraft by means of a rod 5 supporting an engine 6 (for example an electric motor) which drives the rotors 2 in rotation via a power shaft in a manner known per se. According to the example shown in a non-limiting manner, each rotor 2 comprises two blades 7.

[0068] Figure 1CA second embodiment of an aircraft propulsion system 1 ' according to the invention is shown, in which the propulsion system 1 ' can be mounted on a pivot shaft 4' which passes through the rotor 2 perpendicularly to the axis of rotation X of the rotor 2. The rotor 2 of the propulsion system 1 ' is connected to the aircraft via a lever 5 supporting an engine 6 (for example an electric motor) which drives the rotor 2 in rotation via a power shaft in a manner known per se. According to an embodiment, the lever 5 of the rotor 2 is merged with the pivot shaft 4'.

[0069] refer to Figures 2 to 4 According to the present invention, the nacelle fairing 3 of the propulsion system 1, 1' comprises:

[0070] - an upstream section 10;

[0071] - a downstream section 20; and

[0072] An intermediate section 30 , which connects the upstream section 10 and the downstream section 20 .

[0073] The upstream section 10 forms the inlet cross section (or in other words the leading edge) BA or the air inlet of the nacelle fairing 3 .

[0074] The upstream section 10 is made of a material which, when supplied with hot air, can withstand a temperature which makes it suitable for anti-icing.

[0075] The middle section 30 is rigid. For example, it is made of an aluminum alloy, titanium filled with 6% aluminum and 4% vanadium (TA6V), or an organic matrix carbon fiber composite material. Advantageously, the middle section 30 is connected to the engine 6 of the propulsion system 1, 1' by at least one rod 5, preferably by two rods 5, to the engine 6 of the propulsion system 1, 1', so as to mechanically mount the nacelle fairing 3 to the engine 6 of the propulsion system 1, 1'. Therefore, the middle section 30 confers a protective function to the propulsion system 1, 1' by its material and construction.

[0076] The downstream end 21 of the downstream section 20 forms the outlet cross section (or in other words the trailing edge) BF or the air outlet of the nacelle fairing 3 .

[0077] The downstream section 20 comprises a radially inner wall 20a and a radially outer wall 20b. The radially inner wall 20a and the radially outer wall 20b of the downstream section 20 provide not only a structural function of the downstream section 20 but also an aerodynamic function.

[0078] The radially inner wall 20a and the radially outer wall 20b of the downstream section 20 are made of a semi-rigid deformable shape memory material. In other words, the material constituting the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 is both rigid to provide the structural shape to the downstream section 20 and flexible to provide the downstream section 20 with deformability. Therefore, the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 are made of a material that can react under the action of an actuator as described below. When the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 are subjected to force by one or more actuators, the wall deforms, and when the one or more actuators stop applying stress, the wall returns to the original shape of the wall. For example, the radially inner wall 20a and the radially outer wall 20b are made of a composite material or a nickel-titanium alloy (also called "Kiokalloy") (e.g., NiTiNol or NiTiCu).

[0079] The shape memory material constituting the radially inner wall 20a and the radially outer wall 20b is fail-safe, i.e. the shape memory material is such that the rest position of the shape memory material (in other words, the position of the shape memory material when no actuator acts on the shape memory material to deform the shape memory material) corresponds to the natural storage geometry of the material or a longer period of use. Thus, in the event of an actuator failure, the shape memory material will return to the natural shape of the shape memory material at rest, and the nacelle fairing 3 will return to a safe geometry ensuring axial thrust to ensure the correct operation of the propulsion system 1, 1' of the aircraft.

[0080] The radially inner wall 20a and the radially outer wall 20b may also have a varying thickness in the axial direction and in the azimuth angle near the reinforcing bridge 22 to locally modify the elasticity of the structure. Further, the mechanical characteristics of the shape memory material constituting the radially inner wall 20a and the radially outer wall 20b can be locally optimized according to the desired local characteristics along the downstream section 20. Therefore, it is conceivable that the downstream section 20 includes a plurality of sections made of different materials.

[0081] The downstream section 20 is made of a deformable semi-rigid material, which ensures a rigid structural shape to avoid collapse of the downstream section 20 at rest and under the action of air flow during operation of the propulsion system 1, 1', so that the nacelle fairing 3 can maintain a uniform aerodynamic profile of the outlet cross section BF of the nacelle fairing. Advantageously, the downstream end 21 of the downstream section 20 can be made of an orthotropic material with a suitable elastic modulus.

[0082] Furthermore, in order to ensure that the distance between the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 is substantially constant, reinforcing bridges 22 are provided at regular angular intervals between these walls 20a, 20b.

[0083] One object of the invention is to be able to direct the thrust of a propulsion system 1 , 1 ′ using a nacelle fairing 3 of the propulsion system 1 , 1 ′, the outlet cross section BF of which and the shape of the outlet cross section can be varied.

[0084] The downstream section 20 therefore comprises means enabling the shape of the outlet cross section BF to be varied.

[0085] To this end, the downstream section 20 comprises a plurality of actuator mechanisms with cylinders 23, 23'. For example, the propulsion system 1, 1' may comprise two actuator mechanisms with cylinders 23, 23', one actuator mechanism being arranged, for example, angularly at 6 o'clock (with reference to the time dial) (i.e. arranged in the lower position) and the other actuator mechanism being arranged diametrically opposite, i.e. arranged at 12 o'clock (with reference to the time dial) (i.e. arranged in the upper position) when the propulsion system 1, 1' is mounted on the aircraft. Each actuator mechanism 23, 23' is configured to cooperate with a device 24, which is integral with an inner surface 20b' of the radially outer wall 20b, so as to deform the radially outer wall 20b in a radial direction relative to the axis of rotation X under the action of a predetermined displacement command.

[0086] Specifically, for each actuator mechanism 23, 23', the cylinder arm 26, 26' is configured to extend or retract under the action of a displacement command to act on the device 24 and radially displace the device 24, generating a thrust on the radial inner surface 20b' of the radial outer wall 20b, thereby changing the size and shape of the outlet cross section BF. Each cylinder 23, 23' can be in a retracted state or a fully extended state. The actuator mechanism with the cylinder 23, 23' can be an electric system, a hydraulic system, a pneumatic system or a screw-nut system.

[0087] The devices 24 are arranged on different, consecutive angular sectors around the axis X. One or more prisms may be associated with a single predetermined angular sector. Each actuator member 23, 23' cooperates with a device 24 facing the cylinder 23, 23', which is therefore associated with a predetermined angular sector, so as to deform the radially outer wall 20b in a direction that is radial with respect to the axis of rotation X and that is angularly centered about the predetermined angular sector over which the prism associated with the cylinder extends.

[0088] For example, the device 24 is embedded, for example by vulcanization, in the radially inner surface 20b' of the radially outer wall 20b and is radially moved under the action of an actuator mechanism having cylinders 23, 23'.

[0089] According to an embodiment, the device 24 comprises a plurality of prisms, for example with a triangular cross section, distributed in at least one annular row, actuated by the cylinders 23 , 23 ′ through at least one annular element 25 .

[0090] Preferably, the prisms 24 are arranged angularly equidistantly on the radially inner surface 20b' of the radially outer wall 20b.

[0091] Advantageously, the contact surfaces of the annular element 25 and the prismatic body 24 are covered with a friction-resistant coating.

[0092] Each actuator member 23 , 23 ′, and more specifically each cylinder, is able to function independently of the other actuator members and is configured to deform the radially outer wall in a radial direction relative to the axis of rotation X under the effect of a predetermined displacement command.

[0093] To this end, each actuator mechanism 23, 23' is connected to an automatic machine which enables the cylinder 23, 23' to be actuated or not actuated by applying a displacement command to obtain the desired transverse thrust component, the displacement command being adjusted according to the desired configuration of the nacelle fairing 3. In particular, the automatic machine operates the actuator mechanism and thus the cylinder 23, 23' independently of the other actuator mechanisms (and therefore the other cylinders).

[0094] Preferably, the cylinders 23 , 23 ′ are arranged angularly equidistantly in the downstream section 20 .

[0095] according to Figures 2 to 7 , the propulsion system 1, 1' comprises two actuator mechanisms with cylinders 23, 23': a first actuator mechanism with one cylinder 23 extending in a first part of the downstream section 20 (upper part in the drawing); and a second actuator mechanism with one cylinder 23' extending in a second part of the downstream section 20 (lower part in the drawing). In the drawing, the actuator mechanisms with cylinders are shown in the upper (top) part and in the lower (bottom) part of the downstream section, but can of course be integrated in different angular sectors (for example, the right sector and the left sector in the rear view) depending on the orientation of the propulsion system when it is installed on the aircraft. Of course, the invention is by no means limited to this embodiment, and the propulsion system 1, 1' can comprise more actuator mechanisms with cylinders.

[0096] Figure 2 A propulsion system 1 , 1 ′ according to the invention is shown, wherein the nacelle fairing 3 is shown in a neutral position, ie a pure axial thrust position. Figure 5The cylinder 23, 23' is shown in this neutral position. The arm 26, 26' of the cylinder 23, 23' of the actuator mechanism with the cylinder 23, 23' is fully retracted. The radially inner wall 20a and the radially outer wall 20b are in a state of zero extension (in other words, the walls 20a and 20b are in a state of rest). Therefore, the local deformation of the radially outer wall 20b is zero.

[0097] Figure 3 A propulsion system 1 , 1 ′ according to the invention is shown, wherein the nacelle fairing 3 is shown in a position deflected in the flow direction. Figure 6 The radially outer wall 20b and the prismatic body 24 are shown when the actuator mechanism with cylinders 23, 23' is in an asymmetric downward thrust position. The command to produce a downward displacement of the nacelle requires that the output cross section of the nacelle be deformed upwards to produce a force directed downwards from the top. The actuator mechanism with cylinder 23 is actuated. Specifically, an extension set point is calculated based on the input of the flight command and then sent to the actuator mechanism with cylinder 23. The actuation of the actuator mechanism with cylinder 23 causes the cylinder arm 26 to extend, which causes the upper part of the annular element 25 to be axially displaced (along the Figure 3 In the direction of arrow F2 in FIG. 1 ), thereby causing the opposite row of prisms 24 to shift radially outward (along Figure 3 and Figure 6 In particular, the annular element 25 moves on the face of the prismatic body 24 facing the cylinder 23 to be located in a position flush with the inner surface 20b' of the radially outer wall 20b in the neutral position of the downstream section 20 of the nacelle fairing 3, and in a position close to the vertex of the prismatic body 24 facing the cylinder 23 in the asymmetric position of the downstream section 20 of the nacelle fairing 3. Since the prismatic body 24 is embedded in the radially inner surface 20b' of the radially outer wall 20b, and the annular element 25 is rigid, the size of the upper part of the radially inner wall 20a increases under the radial thrust of the prismatic body 24. This increase in size results in a change in the shape of the upper part of the outlet cross section BF. In fact, the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 are made of a deformable material, and in particular, due to the bridge 22, the change in the geometry of the radially outer wall 20b leads to a change in the geometry of the radially inner wall 20a, which has the effect of changing the downstream section of the nacelle fairing 3 into, for example Figure 6 The asymmetric structure shown in FIG. The cooperation between the cylinder 23, the annular element 25 and the prism 24 causes the radial outer wall 20b to extend in the radial direction relative to the rotation axis X ( Figure 6 The arrow F3 in the figure is deformed, the radial direction being angularly centered relative to the angular segment over which the prism 24 associated with the cylinder 23 extends, i.e. Figure 623'. In other words, the cylinder 23' is in a stationary position. In particular, the lower portion of the annular element 25 does not move on the surface of the prismatic body 24 facing the cylinder 23'. The actuation of the cylinder 23 causes a local deformation of the outlet cross section BF, i.e., a local radial expansion E. Therefore, the outlet cross section of the fairing is asymmetric, and the shape of the outlet cross section is due to the mechanical characteristics of the structure subjected to the thrust of the cylinder 23. When the cylinder 23 is activated, there is a radial local expansion E of the outlet cross section BF of the fairing 3, i.e., there is a local deflection of the structure on the side of the activated cylinder. The radial dimension (in the direction of the arrow F3) of a set of actuator mechanisms having cylinders 23, 23' (cylinder 23 is activated, cylinder 23' is in a stationary state) is equal to the sum of the radial dimension DE of the radial outer wall 20b and the expansion E when the actuator mechanism having the cylinder is in a stationary state. The radially outer wall 20b forms a ring, a part of which (in this case, the upper part) is deformed.In the radially outer wall 20b (at the level of the prismatic body 24 facing the actuated upper cylinder 23) there is a radial local enlargement.

[0098] Figure 4 A propulsion system 1 , 1 ′ according to the invention is shown, wherein the nacelle fairing 3 is shown in a position in which the flow is deflected downward. Figure 7 The radial outer wall 20b and the prismatic body 24 are shown when the actuator mechanism with cylinders 23, 23' is in an asymmetric upward thrust position. The command to produce an upward displacement of the nacelle requires that the output cross section of the nacelle be deformed downward to produce a force directed upward from the bottom. The actuator mechanism with cylinder 23' is activated. Specifically, an extension set point is calculated based on the input of the flight command, and then the extension set point is sent to the actuator mechanism with cylinder 23'. The actuation of the actuator mechanism with cylinder 23' causes the cylinder arm 26' to extend, which causes the lower part of the annular element 25 to be axially displaced (along the Figure 4 In the direction of arrow F4 in FIG. 1 ), thereby causing a row of prisms 24 to shift radially outward (along Figure 4 and Figure 7In particular, the annular element 25 moves on the face of the prismatic body 24 facing the cylinder 23' to be located in a position flush with the inner surface 20b' of the radially outer wall 20b in the neutral position of the downstream section 20 of the nacelle fairing 3, and in a position close to the vertex of the prismatic body 24 facing the cylinder 23' in the asymmetric position of the downstream section 20 of the nacelle fairing 3. Since the prismatic body 24 is embedded in the radially inner surface 20b' of the radially outer wall 20b, and the annular element 25 is rigid, the size of the upper part of the radially inner wall 20a increases under the radial thrust of the prismatic body 24. This increase in size results in a change in the shape of the lower part of the outlet cross section BF. In fact, the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 are made of a deformable material, and in particular, due to the bridge 22, the change in the geometry of the radially outer wall 20b leads to a change in the geometry of the radially inner wall 20a, which has the effect of changing the downstream section of the nacelle fairing 3 into, for example Figure 7 The asymmetric structure shown in FIG. The cooperation between the cylinder 23 ', the annular element 25 and the prism 24 causes the radial outer wall 20b to extend in the radial direction relative to the rotation axis X ( Figure 7 The radial direction is angularly centered relative to the angular segment over which the prism 24 associated with the cylinder 23' extends, i.e., Figure 7 23', and the cylinder 23' is in a vertically downward extension. Therefore, the cylinder 23' is activated, while the cylinder 23 is deactivated. In other words, the cylinder 23 is in a stationary position. In particular, the upper part of the annular element 25 does not move on the surface of the prismatic body 24 facing the cylinder 23. The actuation of the cylinder 23' causes a local deformation of the outlet cross section BF, i.e. a local radial expansion E. Therefore, the outlet cross section of the fairing is asymmetric, and the shape of the outlet cross section is caused by the mechanical characteristics of the structure subjected to the thrust of the cylinder 23'. When the cylinder 23' is activated, there is a radial local expansion E of the outlet cross section BF of the fairing 3, i.e., there is a local deflection of the structure on the activated cylinder side. The radial dimension (along the direction of the arrow F5) of a set of actuator mechanisms having cylinders 23, 23' (cylinder 23 is in a stationary state, cylinder 23' is activated) is equal to the sum of the radial dimension DE of the radial outer wall 20b and the expansion E when the actuator mechanism having the cylinder is in a stationary state. The radially outer wall 20b forms an annulus of which a part (in this case the lower part) is deformed.In the radially outer wall 20b (at the level of the prismatic body 24 facing the operated lower cylinder 23') there is a radial local enlargement.

[0099] The extension of the cylinder caused by the automatic machine gradually increases, so that the shape and size of the outlet cross section BF are gradually changed. In particular, there is a local deformation of the radially inner wall 20a and the radially outer wall 20b made of deformable shape-memory material of the downstream section 20 associated with the prismatic body facing the actuated cylinder, in the radial direction relative to the axis X. This therefore changes the size and shape of the outlet cross section BF, so that the outlet cross section changes from Figure 2 The minimum radial dimension DE and circular shape in the axial thrust mode configuration shown change to Figure 3 and Figure 4 The radial dimension DE+E, which is greater than the minimum radial dimension DE, in the asymmetric thrust mode configuration of the nacelle fairing 3 shown is deformed in at least one radial direction of the circular shape of a set of actuators.

[0100] Similarly, the extension of the cylinder caused by the automatic device is gradually reduced, so that the nacelle fairing 3 is changed from Figure 3 and Figure 4 The asymmetric thrust mode configuration shown gradually transforms into Figure 2 Axial thrust mode configuration shown.

[0101] The downstream section 20 of the nacelle fairing 3 is Figure 5 The structure is transformed into Figure 6 or Figure 7 The structure and Figure 6 or Figure 7 The structure is transformed into Figure 5 The configuration is continuously performed under the action of extension or retraction of the arms 26, 26' of the cylinders 23, 23' of the actuator mechanism with cylinders caused by the automatic device, and during the change of the configuration (size and shape) of the outlet cross-section BF of the nacelle fairing 3, the reinforcing bridge 22 ensures that the distance between the radially inner wall 20a and the radially outer wall 20b of the downstream section 20 is substantially constant.

[0102] According to an embodiment, the propulsion system 1 , 1 ′ may comprise a plurality of rows of prismatic bodies 24 , 24 ′ and a plurality of actuator mechanisms with cylinders 23 , 23 ′ for each annular row of prismatic bodies 24 , 24 ′, independently of one another.

[0103] Advantageously, but in a non-limiting manner, each annular row may comprise at least four prisms 24 , 24 ′ distributed in an azimuthally equidistant manner along the radially inner surface 20 b ′ of the radially outer wall 20 b of the downstream section 20 .

[0104] refer to Figure 8, the means 24, 24' may comprise a plurality of prisms, for example with a triangular cross section, distributed in two annular rows. The prisms 24 of the first annular row are connected to an arm or each arm 26, 26' of a cylinder 23, 23' of an actuator mechanism having a cylinder 23, 23' via a first annular element 25. The prisms 24' of the second annular row are connected to the prisms 24 of the first annular row, more precisely to the first annular element 25, via a second annular element 28 and a plurality of rods 27, here arranged at 12 o'clock and 6 o'clock. The prisms 24, 24', the annular elements 25, 28 and the connecting rods 27 are made of a rigid material, for example metal.

[0105] Preferably, the downstream section 20 comprises at least two angularly equidistantly arranged means 24 , 24 ′ (for example angularly arranged at 6 o'clock and 12 o'clock), in particular for pushing the annular elements 25 , 28 and the connecting rod 27 .

[0106] If you can Figure 8 As can be seen in FIG. 1 , the prisms 24 of the first annular row (closest to the intermediate section 30) and the prisms 24' of the second annular row (closest to the outlet cross section BF) have different dimensions. In particular, the vertex angle θ' of the prisms 24' is smaller than the vertex angle θ of the prisms 24. In fact, in order to move the downstream section 20 of the nacelle fairing 3 from the neutral position to the asymmetric position, the inner wall 20a and the outer wall 20b are subjected to a displacement of variable amplitude, which increases when the inner wall 20a and the outer wall 20b approach the outlet cross section, and therefore, the prisms 24, 24' are configured so that for the same axial displacement of the annular elements 25, 28, the inner wall 20a and the outer wall 20b can undergo such a variable amplitude radial displacement.

[0107] In order to divert the flow upward, for example, the actuator mechanism with the cylinder 23 is operated. The actuation of the actuator mechanism with the cylinder 23 causes the cylinder arm 26 to extend, which causes the annular element 25 to be axially displaced (in the direction of the arrow F6), which in turn causes a row of prisms 24 to be radially displaced outward (in the direction of the arrow F7) and the rod 27 and the second annular element 28 to be axially displaced (in the direction of the arrow F8), which in turn causes the second row of prisms 24' to be radially displaced outward (in the direction of the arrow F9). Since the prisms 24, 24' are embedded in the radial inner surface 20b' of the radial outer wall 20b, and the annular elements 25, 28 are rigid, the size of the upper part of the radial inner wall 20a increases under the radial thrust of the prisms 24, 24'. This increase in size causes the shape of the upper part of the outlet cross section BF to change. The cooperation between the cylinder 23, the annular elements 25, 28, the rod 27 and the prismatic bodies 24, 24' causes the radial outer wall 20b to deform in a radial direction relative to the axis of rotation X, which is angularly centered relative to the angular segment over which the prismatic bodies 24, 24' associated with the cylinder 23 extend. Thus, the cylinder 23 is activated, while the cylinder 23' is deactivated. In particular, the lower part of the annular elements 25, 28 does not move on the face of the prismatic bodies 24, 24' facing the cylinder 23'. The actuation of the cylinder 23 causes a local deformation of the outlet cross section BF, i.e. a local radial expansion. There is a local radial increase in the radial outer wall 20b (at the level of the prismatic bodies 24, 24' facing the actuated cylinder 23).

[0108] In order to divert the flow downward, for example, the actuator mechanism with the cylinder 23' is actuated. The actuation of the actuator mechanism with the cylinder 23' causes the cylinder arm 26' to extend, which causes the annular element 25 to be displaced axially (in the direction of the arrow F10), which in turn causes a row of prisms 24 to be displaced radially outward (in the direction of the arrow F11) and the rod 27 and the second annular element 28 to be displaced axially (in the direction of the arrow F12), which in turn causes the second row of prisms 24' to be displaced radially outward (in the direction of the arrow F13). Since the prisms 24, 24' are embedded in the radial inner surface 20b' of the radial outer wall 20b, and the annular elements 25, 28 are rigid, the size of the lower part of the radial inner wall 20a increases under the radial thrust of the prisms 24, 24'. This increase in size results in a change in the shape of the lower part of the outlet cross section BF. The cooperation between the cylinder 23', the annular elements 25, 28, the rod 27 and the prismatic bodies 24, 24' causes the radial outer wall 20b to deform in a radial direction relative to the axis of rotation X, which is angularly centered relative to the angular segment over which the prismatic bodies 24, 24' associated with the cylinder 23' extend. Thus, the cylinder 23' is activated, while the cylinder 23 is deactivated. In particular, the upper part of the annular elements 25, 28 does not move on the face of the prismatic bodies 24, 24' facing the cylinder 23. The actuation of the cylinder 23' causes a local deformation of the outlet cross section BF, i.e. a local radial expansion. There is a local radial increase in the radial outer wall 20b (at the level of the prismatic bodies 24, 24' facing the actuated cylinder 23').

[0109] The invention is mainly described with respect to a propulsion system comprising one annular element and two cylinders, but the propulsion system may of course comprise a plurality of annular elements and a greater number of cylinders.

Claims

1. A propulsion system (1, 1') for an aircraft, comprising at least one rotor (2) and a nacelle fairing (3), the nacelle fairing (3) extending around the at least one rotor (2) relative to the axis of rotation (X) of the rotor (2), the nacelle fairing (3) comprising an upstream section and a downstream section (20), the upstream section forming an inlet cross section of the nacelle fairing, and a downstream end (21) of the downstream section (20) forming an outlet cross section (BF) of the nacelle fairing (3); characterized in that The downstream section (20) includes a radial inner wall (20a) and a radial outer wall (20b), wherein the radial inner wall (20a) and the radial outer wall (20b) are made of deformable shape memory material, and the radial outer wall (20b) includes a plurality of actuator mechanisms having at least one cylinder (23, 23'), each actuator mechanism being capable of operating independently of the other actuator mechanisms and being configured to cooperate with a device (24, 24') embedded in an inner surface (20b') of the radial outer wall (20b) so as to deform the radial outer wall (20b) in a radial direction relative to the rotation axis (X) under the action of a predetermined displacement command.

2. The propulsion system (1, 1') according to claim 1, wherein: The device (24, 24') comprises a plurality of prisms distributed in at least one annular row on the inner surface (20b') of the radially outer wall (20b).

3. The propulsion system (1, 1') according to claim 2, wherein: The plurality of prisms are arranged angularly equidistantly on the inner surface (20b') of the radial outer wall (20b).

4. The propulsion system (1, 1') according to claim 2, wherein: The plurality of prismatic bodies are actuated by the cylinder (23, 23') via at least one annular element (25, 28).

5. The propulsion system (1, 1') according to any one of claims 1 to 4, wherein: The cylinders (23, 23') are arranged angularly equidistantly in the downstream section (20).

6. The propulsion system (1, 1') according to any one of claims 1 to 4, wherein: The multiple actuator mechanisms having at least one cylinder include: a first actuator mechanism having at least one cylinder, wherein the cylinder of the first actuator mechanism is configured to cooperate with the device (24, 24') to deform the radial outer wall (20b) along a first radial direction relative to the rotation axis (X) under the action of a predetermined shift command; and a second actuator mechanism having at least one cylinder, wherein the cylinder of the second actuator mechanism is configured to cooperate with the device (24, 24') to deform the radial outer wall (20b) along a second radial direction opposite to the first radial direction under the action of a predetermined shift command.

7. The propulsion system (1, 1') according to any one of claims 1 to 4, further comprising a reinforcing bridge (22) connecting the radially inner wall (20a) and the radially outer wall (20b) of the downstream section (20).

8. The propulsion system (1, 1') according to any one of claims 1 to 4, wherein: The nacelle fairing further comprises an upstream section (10) forming an inlet cross section of the nacelle fairing, and an intermediate section (30) connecting the upstream section (10) and the downstream section (20), wherein the intermediate section (30) is rigid and connected to an engine (6) of the propulsion system (1, 1') via at least one rod (5).

9. An aircraft, characterized in that: The aircraft comprises at least one propulsion system (1, 1') according to any one of claims 1 to 8, which is mounted to pivot on the aircraft via a pivot axis (4, 4') which is offset from the rotor (2) or passes through the rotor (2).

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