Improved propulsive assembly with boundary layer ingestion

Abstract

Propulsion assembly of an aircraft, comprising a fuselage (10) extending along a longitudinal axis (X) and enclosing an inner casing, at least one ducted engine (20) fixed to said fuselage (10) and comprising an intake portion (20a) at least partially arranged in said inner casing, at least one plenum chamber (50) arranged in the inner casing upstream of said intake portion (20a) and in fluid communication with said intake portion (20a), at least one air intake (30) formed on an outer wall of said fuselage (10), an inlet (30a) of said air intake (30) being partially delimited by the outer wall of said fuselage (10), said air intake (30) being configured to draw in outside air and to divert it towards said plenum chamber (50).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of boundary layer ingestion for aircraft engines, and more particularly to a propulsion assembly for an aircraft comprising such an engine, and to an aircraft comprising such a propulsion assembly. BACKGROUND

[0002] To improve the efficiency of aircraft engines, in particular those powering long-range aircraft such as commercial or intercontinental aircraft, a known technique is based on the principle of boundary layer ingestion (BLI) by arranging the engine so as to be able to ingest the boundary layer formed on the fuselage of the aircraft, reducing the drag while at the same time improving the propulsion efficiency of the engine.

[0003] More particularly, the engine is arranged so that its intake portion is flush with the surface of the fuselage, or is partially integrated into the fuselage of the aircraft, so that the boundary layer developing along the wall of said fuselage is directly ingested into the engine. The boundary layer ingestion technique thus has at least two advantages.

[0004] On the one hand, the ingested boundary layer no longer rubs against the portion of the fuselage located downstream of the intake of the engine, since it is ingested by this intake and transformed into propulsion, this fact allowing the drag of the aircraft to be limited.

[0005] On the other hand, the average Mach number of the flow entering the engine is much lower than the flight Mach number of the aircraft due to the presence of the boundary layer, this fact being characterized by a lower average total pressure and therefore by a lower average speed of the flow than the flight speed. The thrust of the engine can thus be obtained with a lower ejection speed than in the case of a conventional installation, the term "conventional" in particular referring to a configuration in which the engine is arranged under the wing of the aircraft or is installed transversely on the fuselage, at a distance greater than the diameter of the fan. In fact, the thrust is directly proportional to the difference between the ejection speed and the speed of the intake of the engine. By reducing the speed of the intake, it is thus possible to obtain the same thrust at a lower ejection speed. The total energy required by the propulsion system to produce this speed difference is thus lower, and the required fuel flow rate is therefore reduced.

[0006] However, this boundary layer ingestion technique has drawbacks. In particular, although the average Mach number of the intake of the engine is lower than in the case of a conventional installation, in particular under the wing or behind the fuselage with a nacelle and pylons, this average masks a strong spatial distortion of the total pressure in the intake portion. This distortion is due to the lower speed of the boundary layer close to the wall of the fuselage than in the rest of the intake portion. This strong heterogeneity of the flow entering the engine has significant negative effects in terms of aerodynamic performance and aeronautical mechanical behavior. In particular, it has a negative effect on the energy concentration efficiency of the fan and on its aeroelasticity.

[0007] There is therefore a need for a propulsion assembly which at least partially overcomes the aforementioned drawbacks. SUMMARY

[0008] The present disclosure relates to a propulsion assembly for an aircraft, comprising:

[0009] - a fuselage extending along a longitudinal axis and enclosing an inner casing,

[0010] - at least one ducted engine secured to the fuselage and comprising an intake portion, the intake portion being at least partially disposed in the inner casing,

[0011] - at least one plenum disposed in the inner casing upstream of the intake portion and in fluid communication with the intake portion,

[0012] - at least one intake formed in the outer wall of the fuselage, the intake having an inlet portion partially delimited by the outer wall of the fuselage, the intake being configured to draw in external air and to divert it towards the plenum.

[0013] In the present disclosure, the terms "upstream" and "downstream" refer to the direction of flow of external air coming from an external region of the propulsion assembly, into the inner casing and upstream to the intake portion of the engine, through the plenum.

[0014] The longitudinal axis of the fuselage corresponds to the longitudinal axis of the aircraft, extending between the front and the rear of the latter. The longitudinal axis can be parallel to the rotation axis of the engine. By "ducted engine" is meant an engine surrounded by a generally annular wall or nacelle. The engine is preferably a ducted bypass engine comprising, from upstream to downstream, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine, wrapped in a fairing. Alternatively, the engine can be a distributed propulsion engine comprising a ducted fan directly driven by a gas generator comprising, from upstream to downstream, a compressor, a combustion chamber and a turbine, or the gas generator is driven by an electric motor. The intake portion of the engine corresponds to the plane in which the fan of the engine is located. Furthermore, it will be understood that the inlet of the intake is delimited on the one hand by a wall of the intake which is separate from the wall of the fuselage, and on the other hand by the wall of the fuselage itself. That is to say, the intake comprises a wall which is attached to the fuselage and which is connected continuously to the wall of the fuselage. The wall of the intake can for example take the form of a half-pipe secured to the wall of the fuselage, so that the wall of the fuselage itself partially delimits the inlet portion of the intake. Thus, when the aircraft is in motion, the boundary layer formed along the outer wall of the fuselage is drawn directly by the intake. This drawing in of the boundary layer thus allows to improve the propulsion efficiency of the engine.

[0015] Moreover, the plenum is a cavity used to homogenize the airflow entering the engine in terms of circumferential and azimuthal distribution of the airflow velocity vectors, while further reducing the average Mach number at the engine inlet. More specifically, the use of a plenum upstream of the engine inlet section allows to obtain low flow velocities upstream of the engine, while minimizing the distortion of the airflow. This allows to jointly optimize the propulsive efficiency and the polytropic efficiency of the fan (by minimizing the distortion), while greatly limiting the aero-mechanical stresses of the fan blades, due to the suction of the boundary layer by the inlet.

[0016] In some embodiments, the inlet section of the engine is entirely disposed in the inner shell of the fuselage.

[0017] The inlet section is thus not visible from the outside of the fuselage. The entire surface occupied by the inlet section is thus in fluid communication with the plenum, which allows to further improve the homogenization of the airflow and pressure at the engine inlet.

[0018] In some embodiments, the surface of the plenum entirely comprises the surface of the inlet section of the engine, in a view perpendicular to the inlet section of the engine.

[0019] That is, in a view perpendicular to the inlet section of the engine, i.e. parallel to the longitudinal axis of the fuselage, the projection of the plenum on the plane comprising the inlet section of the engine encircles, i.e. entirely surrounds, said inlet section. This allows to further improve the homogenization of the flow and pressure on the entire surface of the inlet section of the engine, thereby improving the polytropic efficiency of the fan.

[0020] In some embodiments, the inlet is a fixed inlet, the assembly comprising at least one retractable inlet configured to be movable between an open position for sucking outside air through the retractable inlet and directing it towards the plenum, and a closed position preventing outside air from entering the plenum through the retractable inlet.

[0021] “fixed” means that the size of the inlet portion of the intake is constant during all flight, ground or static phases. That is to say, the walls forming the fixed intake remain static relative to the fuselage during all these phases. Conversely, “retractable” means that the size of the inlet portion of the intake can vary depending on the flight, ground or static phase. Thus, in the open position, the retractable intake allows a greater amount of air to be drawn into the plenum. This increase in the amount of air drawn in is particularly useful in static conditions or during the take-off phase, when the movement speed of the assembly is low or zero, and when the air flow required to power the engines is greater. Then, when the take-off phase ends, these retractable intakes or secondary or auxiliary intakes are discreetly closed, that is to say, switched directly from the open position to the closed position without intermediate or progressive positions. Preferably, in the closed position, the retractable intake is fully integrated into the external shape of the wall of the fuselage, that is to say, in the continuity of the outer wall of the fuselage, without any undulations being created along the surface of the fuselage. This allows the risk of creating turbulence in the flow outside the fuselage to be limited, which would affect the efficiency of the engines. Furthermore, the area in which the retractable intake is in the open position can be characterised by an altitude of less than 15000 feet and / or a flight Mach number of less than 0.45.

[0022] In some embodiments, the inlet portion of the fixed intake is at least equal to the inlet portion of the engine.

[0023] When the assembly comprises a plurality of fixed intakes and / or a plurality of engines, the sum of the inlet portions of the fixed intakes must be at least representative of the sum of the inlet portions of the engines in order to allow a correct supply to the plenum.

[0024] In some embodiments, the inlet portion of the retractable intake in the open position is between 25% and 50% of the portion of the fixed intake. For certain flight phases, one or more retractable intakes can be added.

[0025] These values allow ensuring that there is sufficient air intake flow in the plenum to achieve optimal efficiency of the engines.

[0026] In some embodiments, the propulsion assembly comprises at least one air intake ramp hollowed out in the outer wall of the fuselage relative to a reference surface of said wall and extending from a portion of said outer wall located upstream of the intake to the inlet portion of said intake.

[0027] A "hollow ramp" is an inclined slope formed in the fuselage wall, i.e. a hollowed-out portion with respect to a reference surface of the fuselage wall, which is the average surface of the fuselage wall around the ramp, which does not show any undulations. This reference surface corresponds to the overall envelope of the fuselage. In other words, the hollow ramp represents a recessed portion of the fuselage wall, in the direction of the inner envelope. Conversely, the air intake represents a bulging portion of the fuselage wall, in the opposite direction to the inner envelope. The presence of this ramp allows the maximum cross-section of the air intake to be optimized and the air flow to be slowed down.

[0028] In some embodiments, the propulsion assembly comprises at least one movable deflector, which is arranged in the plenum and is configured to switch from a deployed position, in which it is configured to direct the external air towards the air intake portion of the engine, to a retracted position, in which it is folded on an inner wall of the plenum.

[0029] The deflectors can be fixed to the walls of the plenum or to the fuselage by means of a pivot link. Their movement between the deployed position and the retracted position can be controlled remotely by a control unit, which also controls the telescopic air intake. The deployed position of the deflectors allows a channel or passage to be formed which directs the air in a more direct manner towards the engine inlet when the air flow is slowed down. This allows the recirculation and pressure drop of this air flow in the plenum to be reduced. The area in which the deflectors are in the deployed position can also be characterized by an altitude lower than 15,000 feet and / or a flight Mach number lower than 0.45. Thus, during the flight phase, for higher air flow speeds, the deflectors are retracted against the inner walls of the plenum so as not to hinder the entry of air into the plenum.

[0030] In some embodiments, the propulsion assembly comprises two fixed air intakes formed on the outer wall of the fuselage in the radial direction of the fuselage, at opposite ends of the fuselage.

[0031] "Radial" means a direction perpendicular to the longitudinal axis of the fuselage. These two fixed air intakes allow a sufficient amount of air to be drawn into the plenum to achieve optimal operation of the engine. The presence of two fixed air intakes is particularly suitable in the case where there are two engines.

[0032] In some embodiments, at least some of the inner walls of the plenum comprise sound-absorbing material.

[0033] The acoustic material can in particular take the form of a honeycomb structure. In particular, the cells of the honeycomb can be inserted between a perforated skin oriented towards the inside of the plenum and a solid skin, the perforated skin allowing sound waves to penetrate into the cells where they will be attenuated. Advantageously, two levels of acoustic cells separated by an acoustic porous layer ("membrane") can be provided, the two layers having different thicknesses and thus being able to attenuate different wave frequencies. The presence of sound-absorbing material further allows the dissipation of the acoustic energy emitted by the fan to be improved.

[0034] In some embodiments, the fuselage has a substantially elliptical cross-section, comprising a major axis and a minor axis, the ratio between the major axis and the minor axis being comprised between 1 and 2.5.

[0035] By "substantially elliptical" it is meant that the fuselage has a cross-section of elongated shape, for example a rectangular or oval shape. The major axis and the minor axis each extend in a direction perpendicular to the longitudinal axis of the fuselage. The use of this type of fuselage is particularly suitable for arranging two or more engines side by side in the width direction, i.e. in a direction perpendicular to the longitudinal axis of the fuselage.

[0036] In some embodiments, the plenum has a parallelepiped shape.

[0037] This shape has the advantage of being easy to implement in terms of aircraft structure and is particularly suitable for a fuselage having an elongated cross-section.

[0038] In some embodiments, the parallelepiped shape of the plenum comprises a width extending along the major axis, a length extending along the longitudinal axis and a height extending along the minor axis.

[0039] In some embodiments, the width of the plenum is comprised between 2.1E and 2.8E, where E is the diameter of the engine inlet portion. The diameter E of the engine inlet portion can be comprised between 1.5m and 2.5m. In some embodiments, the length of the plenum is comprised between 1.1E and 2.5E. In some embodiments, the height of the plenum is comprised between 1.3E and 2.0E.

[0040] These ratio values between the dimensions of the plenum and the diameter of the engine inlet portion allow to limit recirculation phenomena inside the chamber while optimizing the plumping effect of the flow, i.e. the slowing down of the flow, minimizing the deformation and the homogenization of the flow at the engine inlet. This allows to further improve the polytropic efficiency of the fan while greatly limiting the aeronautical mechanical stresses on the fan blades.

[0041] In some embodiments, at the inlet of the fixed intake, the maximum spacing between the wall of the fuselage and the wall of the fixed intake defining the inlet of said fixed intake is comprised between 0.5E and 0.8E.

[0042] The inlet of the intake is comprised in one plane and is defined by the intake wall forming a first curve in this plane and the fuselage wall forming a second curve having a different radius of curvature than the first curve. Thus, within this plane, for a given radius of the first curve, the spacing between the wall of the fuselage and the wall of the fixed intake is the distance between a point of the first curve and a point of the second curve. The ratio between the value of this spacing and the diameter of the engine inlet portion allows to optimize the air flow rate entering the plenum.

[0043] In some embodiments, the assembly comprises two engines arranged side by side along a longitudinal axis, the plenum being configured to power both engines.

[0044] That is, the plenum contains the inlet portion of both engines. This configuration allows to increase the polytropic efficiency of both fans together.

[0045] The present disclosure also relates to an aircraft comprising a propulsion assembly according to any of the preceding embodiments.

[0046] The aircraft is preferably of the fast type, characterized by a flight Mach number greater than 0.6 in cruise phase, and is able to cover a range of sizes, making it possible to go from the "business jet" type to the transport of passengers on long-haul aircraft. The aircraft can also be of the "flying wing" type. BRIEF DESCRIPTION OF DRAWINGS

[0047] The application and its advantages will be better understood by reading the following detailed description of various embodiments of the application given by way of non-limiting examples. This description makes reference to the annexed drawings, in which:

[0048] Figure 1 represents a perspective view of an aircraft according to the prior art, using the principle of boundary layer suction;

[0049] Figure 2A represents a perspective view of a propulsion assembly according to one embodiment of the disclosure, comprising a retractable inlet in a closed position, Figure 2B representing the propulsion assembly of Figure 2A in which the retractable inlet is in an open position;

[0050] Figure 3 represents a view along a cutting plane perpendicular to the longitudinal axis of the propulsion assembly of Figures 2A and 2B;

[0051] Figure 4 schematically represents a transparent top view of a propulsion assembly according to one embodiment of the disclosure, comprising two retractable inlets;

[0052] Figure 5 represents Figure 4 a side view of the propulsion assembly illustrated;

[0053] Figure 6 represents Figure 4 and 5 a perspective view of the individual plenum of the propulsion assembly illustrated;

[0054] Figure 7 represents Figure 4 a top view and a partial view of a modified example of the propulsion assembly illustrated;

[0055] Figure 8 represents Figure 4Top view and partial view of an improved example of the propulsion assembly shown;

[0056] Figure 9 denotes Figure 4 Top view of another modified example of the propulsion assembly shown. DETAILED DESCRIPTION

[0057] Figure 1 A perspective view of an aircraft using the boundary layer suction principle according to the prior art is shown. The aircraft comprises a fuselage 1 and two engines 2 fixed on the fuselage 1 at the rear of the aircraft. The engines 2 are arranged so that their air intake portions 2a are partly arranged in the inner shell enclosed by the fuselage 1. In this way, only a part of the engines 2 is visible from the outside of the aircraft, the other part being hidden inside the aircraft. Thus, the boundary layer formed on the outer wall of the fuselage 1 during the flight of the aircraft is directly sucked by the engines 2.

[0058] The rest of the description describes a propulsion assembly according to one embodiment of the disclosure with reference to Figures 2A to 5. The embodiment described in the rest of the description presents a configuration in which the fuselage has a substantially elliptical or rectangular shape and comprises two engines arranged side by side. However, the invention is not limited to this configuration. The fuselage can have a cylindrical or other shape. Furthermore, the number of engines can be more than two.

[0059] Figure 2A schematically shows a perspective view of a propulsion assembly according to the disclosure. The propulsion assembly comprises a fuselage 10 enclosing an inner shell, not visible in Figure 2A. The fuselage 10 extends along a longitudinal axis X. In a cross-sectional view perpendicular to the longitudinal axis X (Figure 2B), the fuselage 10 has a major axis L extending in a direction perpendicular to the longitudinal axis X and a minor axis I extending in a direction perpendicular to the longitudinal axis X and to the major axis L. The ratio between the major axis L and the minor axis I can be comprised between 1 and 2.5. Figure 3

[0060] In the rest of the description, the terms "upper", "lateral", "side" and their derivatives are considered along the major axis and the minor axis of the ellipse formed by the fuselage. More specifically, the top view corresponds to a view in a direction parallel to the minor axis I, i.e. a view perpendicular to the plane formed by the axes X and L, and the side view corresponds to a view in a direction parallel to the major axis L, i.e. a view perpendicular to the plane formed by the axes X and I. In other words, when the propulsion assembly is arranged on an aircraft, the lateral side of the fuselage 10 corresponds to the side on which the wings of the aircraft are arranged, and the top of the fuselage 10 corresponds to the surface on which the tail can be arranged.

[0061] ​The two engines 20 are arranged side by side along the longitudinal axis L. In the present embodiment, the engines 20 are entirely arranged within the inner shell of the fuselage 10, which is not visible in Figure 2A. In particular, the intake portions 20a of the engines 20 are entirely arranged within the inner shell, and are thus entirely surrounded by the walls of the fuselage 10. Of course, the ejection nozzles 20b of the engines 20 are arranged outside the inner shell. To this end, when the propulsion assembly is installed on an aircraft, an opening (not represented) allowing the passage of the engines 20 can be provided at the rear end of the fuselage 10. In this way, the engines 20 are fixed to the fuselage 10 so that their intake portions 20a are arranged within the inner shell, and so that their air ejection nozzles 20b are arranged outside the fuselage 10, thereby allowing the ejection of gases.

[0062] The propulsion assembly comprises two fixed intakes 30, which are arranged on either side of the fuselage 10 along the main axis L, i.e. on the lateral faces of the fuselage 10. In the outer wall of the fuselage 10, the intakes 30 or scoops form a discontinuous portion on the outer wall of the fuselage 10, or form a vent in said wall. In particular, the upstream end of the intakes 30 has an arcuate wall which is separate from the wall of the fuselage 10, and substantially follows the shape of the outer wall of the fuselage 10 in this region of the fuselage 10. However, the radius of curvature of the wall of the intakes 30 is smaller than the radius of curvature of the wall of the fuselage 10 in this same region. Thus, the wall of the intakes 30 and the wall of the fuselage 10 together form an inlet portion 30a having a crescent shape at this upstream end. The downstream end of the intakes 30 is connected continuously to the wall of the fuselage 10.

[0063] Preferably, the sum of the inlet portions 30a of the fixed intakes 30 is at least equal to the intake portion of the engines. For example, the sum of the inlet portions 30a of the intakes 30 can be equal to: the number of engines x CD x π ((E / 2) 2 ), where E is the diameter of the inlet portion of the engines, and CD is a coefficient between 1.1 and 1.3. Furthermore, the maximum distance D between the intakes 30 and the fuselage 10 is between 0.5E and 0.8E, where E is the diameter of the inlet portion 20a of the engines 20. The distance between the intakes 30 and the fuselage 10 is considered to be, for a given intake air 30 radius, the distance between the wall of the intakes 30 and the wall of the fuselage 10 at the inlet portion 30a.

[0064] In addition to the fixed intakes 30, the propulsion assembly comprises at least one retractable intake 40. The retractable intake or intakes 40 are arranged at the top of the fuselage 10, i.e. on the upper face of the fuselage 10. Figure 4An example is shown in which two retractable air intakes 40 are disposed above the fuselage 10. They are movable between a closed position and an open position. The switch from the closed position to the open position can be achieved by a mechanical pivot, and vice versa. In the open position, the retractable air intakes 40 have an inlet portion 40a which represents between 25% and 50% of the inlet portion 30a of the fixed air intake 30. For example, for a fan with a diameter of 85 inches, corresponding to a diameter of approximately 216 centimeters, the inlet portion 40a of the retractable air intakes 40 in the open position is between 0.8 and 1.2 square meters, and the inlet portion 30a of the fixed air intake 30 is between 3 and 3.5 square meters. In the closed position, the retractable air intakes 40 have zero inlet portion 40a.

[0065] The plenum 50 is disposed in the inner shell of the fuselage 10. In this example, the plenum has a parallelepiped shape. This shape is suitable for the general shape of the fuselage 10. However, this shape of the plenum is not limiting and can vary depending on the shape of the fuselage. In particular, the shape of the plenum can generally follow the shape of the inner walls of the fuselage. For example, if the fuselage has a cylindrical shape, the plenum itself can have a cylindrical shape.

[0066] In this embodiment, the plenum 50 has a width 50a extending along the long axis L, a length 50b extending along the longitudinal axis X and a height 50c extending along the short axis I. Preferably, the width 50a is between 2.1 E and 2.8 E, the length is between 1.1 E and 2.5 E, and the height 50c is between 1.3 E and 2.0 E.

[0067] Furthermore, the engines 20 are arranged so that their inlet portions 20a face the plenum 50 entirely, so that the entire surface of the inlet portions 20a is in communication with the volume of the plenum 50. To this end, the lower end of the air intake portion 20a is disposed above the bottom wall of the plenum 50, and the upper end of the air intake portion 20a is disposed below the upper wall of the plenum 50. That is, the surface formed by the width 50a and the height 50c is greater than the sum of the air intake portions 20a of the two engines 20 and contains these two air intake portions 20a.

[0068] The fixed intake 30 is in fluid communication with the plenum 50, so that air sucked by the fixed intake 30 is deflected and directed to the inside of the plenum. Likewise, when the telescopic intakes 40 are in the open position, they are in fluid communication with the plenum 50, so that air sucked by the telescopic intakes 40 is deflected and directed to the inside of the plenum 50. Conversely, when the telescopic intakes 40 are in the closed position, external air will no longer enter the plenum 50 through the telescopic intakes 40. That is, in this configuration, only the fixed intake 30 allows external air to be sucked into the plenum 50. Moreover, in this configuration, the walls of the telescopic intakes 40 are in the continuity of the walls of the fuselage 10, giving them a smooth appearance without undulations compared to the reference surface.

[0069] Figure 7 and 8 A modified example of an embodiment of the application is shown, in which the propulsion assembly comprises a ramp 12 formed in the wall of the fuselage 10. More specifically, the ramp 12 can be formed upstream of each intake 30. In a top view of the propulsion assembly, the ramp 12 has the shape of an inclined slope formed and hollowed out in the wall of the fuselage 10, and descending from a portion of said wall located upstream of the intake 30 to the inlet portion 30a of said intake 30, thereby increasing the inlet portion 30a.

[0070] Figure 9 Another modified example of an embodiment of the application is shown, in which the propulsion assembly comprises a movable deflector 60. More specifically, one movable deflector 60 can be provided for each fixed intake 30. The movable deflector 60 is movable between a deployed position (shown in solid lines in Figure 9 ) and a retracted position (shown in dashed lines in Figure 9 ). In the deployed position, the movable deflector 60 deflects the air entering through the fixed intake 30 in the plenum 50 towards the inlet portion 20a of the engine 20. In the retracted position, the movable deflector 60 is folded on the inner wall of the plenum 50, thus no longer allowing air deflection.

[0071] Although the application has been described with reference to specific exemplifying embodiments, it is evident that modifications and changes can be made without departing from the scope of the application as defined in the claims. In particular, individual features of different illustrated / referred embodiments can be combined in additional embodiments. The description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. Propulsion assembly for an aircraft, comprising: - a fuselage (10) extending along a longitudinal axis (X) and enclosing an inner shell, - at least one ducted engine (20) fixed to the fuselage (10) and comprising an intake portion (20a) at least partially arranged in the inner shell, - at least one plenum chamber (50) arranged in the inner shell upstream of the intake portion (20a) and in fluid communication with the intake portion (20a) and configured to homogenize and reduce the speed of the airflow entering the ducted engine (20), - at least one intake (30) formed on the outer wall of the fuselage (10), the inlet portion (30a) of the intake (30) being partially delimited by the outer wall of the fuselage (10), the intake (30) being configured to draw in external air and to direct it towards the plenum chamber (50).

2. The propulsion assembly of claim 1, wherein, - the intake portion (20a) of the ducted engine (20) being entirely arranged in the inner shell of the fuselage (10).

3. The propulsion assembly of claim 1, wherein, - in a view perpendicular to the intake portion (20a) of the ducted engine (20), the surface of the plenum chamber (50) entirely comprises the surface of the intake portion (20a).

4. The propulsion assembly of claim 1, wherein, - the intake (30) being a fixed intake, the propulsion assembly comprising at least one retractable intake (40) configured to be movable between an open position for drawing in external air through the retractable intake (40) and directing it towards the plenum chamber (50) and a closed position for preventing the entry of external air into the plenum chamber (50) through the retractable intake (40).

5. Propulsion assembly according to claim 1, comprising at least one air intake ramp (12) hollowed in the outer wall of the fuselage (10) with respect to a reference surface of the outer wall of the fuselage (10) and extending from a portion of the outer wall located upstream of the intake (30) to the inlet portion (30a) of the intake (30).

6. Propulsion assembly according to claim 1, comprising at least one movable deflector (60) arranged in the plenum chamber (50) and configured to be switchable from a deployed position in which the movable deflector (60) is configured to direct external air towards the intake portion (20a) of the ducted engine (20) to a retracted position in which the movable deflector (60) is folded on an inner wall of the plenum chamber (50).

7. Propulsion assembly according to claim 1, the intake (30) comprising two fixed intakes formed on the outer wall of the fuselage (10) in the radial direction of the fuselage (10) at opposite ends of the fuselage (10).

8. The propulsion assembly of claim 1, wherein, - at least some of the inner walls of the plenum chamber (50) comprise sound-absorbing material.

9. The propulsion assembly of claim 1, wherein, - the fuselage (10) has a substantially elliptical cross-section comprising a major axis (L) and a minor axis (I), the ratio between the major axis (L) and the minor axis (I) being comprised between 1 and 2.

5.

10. The propulsion assembly of claim 9, wherein, The plenum has a parallelepiped shape comprising a width (50a) extending along the long axis (L), a length (50b) extending along the longitudinal axis (X) and a height (50c) extending along the short axis (I); wherein the width (50a) is comprised between 2.1E and 2.8E, the length (50b) is comprised between 1.1E and 2.5E, the height (50c) is comprised between 1.3E and 2.0E, where E is the diameter of the intake portion (20a) of the ducted engine.

11. The propulsion assembly of claim 4, wherein, At the inlet of the fixed intake (30), the maximum spacing (D) between the outer wall of the fuselage (10) and the wall of the fixed intake (30) defining the inlet of the fixed intake (30) is comprised between 0.5E and 0.8E, where E is the diameter of the intake portion (20a) of the ducted engine (20).

12. Propulsion assembly according to claim 9, comprising two ducted engines (20) arranged side by side along the long axis (L), the plenum (50) being configured to power both ducted engines (20).

13. An aircraft comprising a propulsion assembly (C) according to any one of claims 1-12.

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