AERONAUTICAL PROPELLER WITH RIGHTING

Abstract

The present invention relates to a faired or unfaired aeronautical propulsion system for an aircraft, comprising: - an external casing (102); - a hub mounted pivoting relative to the external casing (102) around a principal axis (X) extending in an upstream-downstream direction of the aircraft; - a propeller mounted on the hub so as to rotate relative to the external casing (102); and - a rectifier mounted on the external casing (102) downstream of the propulsion propeller along the main axis (X), the rectifier extending around the main axis (X), the rectifier comprising stator blades (114) each having: a stator leading edge (BA'), a stator inner radius, a stator outer radius, a stator blade height (H') equal to the difference between the stator outer radius and the stator inner radius, and a stator sweep angle at each point of the stator leading edge (BA').For at least one stator blade (114), the stator deflection angle (F') is positive and increasing over the entire stator blade height (H'), strictly increasing over at least a portion of the stator blade height (H'), and greater than 30° over at least 40% of the stator blade height (H'). Figure for the abbreviation: Fig. 7.

Description

Title of the invention: AERONAUTICAL PROPELLER WITH RIGHTING Technical field of the invention

[0001] The present invention relates to an aeronautical propulsion system for an aircraft, as well as an aircraft comprising such an aeronautical propulsion system. Technological background

[0002] Prior art is known of an aeronautical propulsion system for an aircraft, of the type comprising: - an external casing; - a hub mounted pivoting relative to the external casing around a main axis extending in an upstream-downstream direction of the aircraft; - a propeller mounted on the hub to rotate relative to the external casing; and - a rectifier mounted on the external casing downstream of the propulsion propeller along the main axis, the rectifier extending around the main axis, the rectifier comprising stator blades each having: a stator leading edge, a stator internal radius, a stator external radius, a stator blade height equal to the difference between the stator external radius and the stator internal radius, and a stator sweep angle at each point of the stator leading edge.

[0003] The propeller is designed to drive an airflow downstream.

[0004] The fixed stator is designed to straighten the airflow from the propeller in order to generate thrust that helps propel the aircraft forward. More specifically, this thrust is generated by deflecting the airflow over the stator blades, resulting in different inlet and outlet angles. The stator thus maximizes propulsive efficiency.

[0005] It is known that the propeller has rotor blades having a trailing edge generally provided with a belly, while the leading edges of the stator blades also have a belly.

[0006] It is further known that the flow over each rotor blade can undergo separation, particularly at the belly of the leading edge of the rotor blade. This separation produces wakes that interact with the stator blades to generate wake interaction noise. This separation on the rotor blades can occur during flight phases with high thrust on the rotor blades and / or during flight phases with high angles of attack of the aircraft, such as takeoff. The wakes The resulting impacts are more energetic (increased turbulent kinetic energy and / or mean velocity deficit) at the trailing edge antinodes and on the upper surface (between the antinode and the rotor blade tip) of the rotor blades. However, the leading edge antinodes of the stator blades are generally located at a radius close to the radius of the trailing edge antinodes of the rotor blades. Thus, the wakes reach the stator blades at their antinodes, where the sweep angle is not very large and wake interaction noise can be dominant.

[0007] Thus, to overcome this problem, in certain known rectifiers, the sweep angle is constant over the entire height of the stator blade, which means that the leading edge is straight. Therefore, such a stator blade has no leading edge bulge.

[0008] Furthermore, a vortex forms at the tip of each rotor blade of the propulsion propeller, and these vortices interact with the stator blades, generating vortex interaction noise. To reduce this vortex interaction noise, it is known to truncate the stator blades so that the vortices pass at least partially over the truncated stator blades.

[0009] The invention aims to provide an aeronautical propulsion system that reduces both wake interaction noise and vortex interaction noise. Summary of the invention

[0010] An aeronautical propulsion system is therefore proposed for an aircraft of the aforementioned type, characterized in that, for at least one stator blade, the stator sweep angle is positive and increasing over the entire height of the stator blade, strictly increasing over at least a part of the height of the stator blade and greater than 30° over at least 40% of the height of the stator blade.

[0011] Thanks to the invention, the absence of a leading edge bulge reduces wake interaction noise. This is possible due to the phase shift introduced by increasing the sweep angle along the span or height of the stator blade. Having a positive sweep angle over the entire height of the stator blade means there is no bulge, and therefore a zone with a low stator sweep angle. This is beneficial from an acoustic point of view because the noise radiates in phase at the bulge, increasing the emitted noise levels. Furthermore, the increasing stator sweep angle allows the stator blade to be progressively tilted downstream, so that the vortex from the rotor blade passes more easily over it with less stator blade truncation, thus reducing vortex interaction noise and increasing aerodynamic efficiency.

[0012] Furthermore, having a larger stator sweep angle near the stator blade tip helps to limit vortex interaction noise in case of impact during high angle-of-attack flight phases.

[0013] Furthermore, when the stator blades have variable pitch around a pitch axis, increasing the sweep angle allows a larger portion of the stator blade to be located upstream of the pitch axis, thus counterbalancing the portion of the stator blade downstream of the pitch axis. This prevents the stator blade's center of gravity from being too far from the pitch axis and prevents the moment of the forces (generated by the flow around the blade during operation) on the stator blade around the pitch change axis from being too high, thereby facilitating the modification of the pitch angle.

[0014] The invention may further include one or more of the following optional features, according to any technically possible combination.

[0015] Optionally, i → r, S_high, preferably -17. S_low, with S_high and d < S_low < S_low correspond to the mathematical area under a stator chord as a function of a radius with respect to the principal axis, above and below the antinode of the stator leading edge, respectively.

[0016] Also optionally, S_low, preferably S_high, S_low, and S_low correspond to the mathematical area under a stator chord as a function of a radius with respect to the principal axis, above and below the antinode of the stator leading edge, respectively.

[0017] Optionally, the stator leading edge may also have a lower intermediate point located at one-third of the stator blade height and an upper intermediate point located at two-thirds of the stator blade height, such that there is a straight line passing through the foot and the lower intermediate point making an angle θc with a plane perpendicular to the main axis, and there is also a straight line passing through the lower intermediate point and the upper intermediate point making an angle θd with a plane perpendicular to the main axis, and there is also a straight line passing through the upper intermediate point and the tip making an angle θe with a plane perpendicular to the main axis, and the angle θe is greater than the angle θd and / or the angle θd is greater than the angle θc.

[0018] Optionally, the maximum length of a stator chord may be between 10% and 35% of the stator blade height.

[0019] Optionally, the stator trailing edge has a slack located below 50% of the stator blade height, preferably below 40% of the stator blade height, or the stator trailing edge has a toe that is the upstreammost point of the stator trailing edge.

[0020] Optionally, the stator chord decreases monotonically with the radius, with an average decrease rate at least twice as high between 85% and 95% as between 40% and 60% of the stator blade height.

[0021] Optionally, the stator sweep angle is constant over a height between 10% and 50% of the stator blade height.

[0022] Optionally also, the stator leading edge and / or the stator trailing edge extend only downstream with the radius.

[0023] Optionally also, Axmid > Axpied, preferably Axmid > l,l*Axpied, where Axpied is the axial distance, along the main axis, between the stator leading edge and the stator trailing edge at 5% of stator blade height and Axmid is the axial distance between the stator trailing edge measured at 5% of stator blade height and the stator leading edge at 95% of stator blade height.

[0024] Optionally also, Axhead < Axmid, preferably Axhead < 0.8*Axmid, where Axhead is the axial distance between the stator leading edge at 95% of stator blade height and the trailing edge at 100% of stator blade height.

[0025] Optionally also, the stator deflection angle is greater than 20° over at least 60% of the stator blade height and / or greater than 30° over at least 40% of the stator blade height and greater than 40° over at least 10% of the stator blade height.

[0026] Optionally also, with the stator blade having variable pitch, an airflow driven by the propeller exerts, over the whole of a flight domain of an aircraft equipped with the aeronautical propulsion system, a moment resulting from pressure and friction forces, around a stator pitch axis of less than 500N*m, in particular less than 400N*m.

[0027] Optionally also, the rotor trailing edge and the stator leading edge being separated, at each radius, by a spacing having a maximum max{L(r)} and a minimum min{L(r)}, the spacing is strictly monotonic and 1.5 < max{L(r)} / min{L(r)} < 4, preferably 2.1 < max{L(r)} / min{L(r)} < 3.

[0028] Optionally also, at any radius above a radius of the belly of a rotor leading edge, the stator deflection angle is greater than or equal to the rotor deflection angle.

[0029] Optionally also, the stator blade having for each cut perpendicular to a radius with respect to the main axis, a skeleton like the curve at mid-distance of an intrados and an extrados of the stator blade, the skeleton making, at the stator leading edge, an angle [3 with the main axis, the absolute value of the angle [3 is strictly increasing with the radius.

[0030] Optionally also, the stator leading edge having a tangential displacement in an azimuthal direction, having a local maximum on the side of an extrados of the stator blade reached in a radius rext, a relative height of the local maximum of the tangential displacement, defined as: i, _ - rBÀ is between 5% and 50%. nextref}umyBA,

[0031] Optionally also, the propeller includes at least one rotor blade with a rotor trailing edge having serrations only located above 10% of a rotor blade height and below the smallest radial position between 60% of the rotor blade height and a radius of the belly of the rotor leading edge.

[0032] Optionally also, the stator leading edge having a tangential displacement in an azimuthal direction having a local maximum yBA'ext on the side of an extrados of the stator blade, the relative amplitude defined as (yBA'ext)ZH' will be between 0% and 10%, preferably between 1% and 5%, where H' is the stator blade height.

[0033] Optionally also, the stator string is included, for any radius, between 5% and 45% of the stator blade height.

[0034] An aircraft comprising an aeronautical propulsion system according to any one of the preceding claims is also proposed. Brief description of the figures

[0035] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig. 1] is a cross-sectional view of an aeronautical propulsion system according to the invention, - [Fig.2] is a side view of a rotor blade of a propeller of the aeronautical propulsion system of [Fig.1], - [Fig.3] is a front view of a leading edge of the rotor blade of [Fig.2], - [Fig.4] is a front view of a trailing edge of the rotor blade of [Fig.2], - [Fig. 5] is a view similar to [Fig. 3], further illustrating a cross-section of the rotor blade, - [Fig.6] is a view similar to [Fig.2] further illustrating a rotor deflection angle, - [Fig.7] is a side view of a stator blade of a rectifier of the aeronautical propulsion system of [Fig.1], - [Fig.8] is a front view of a stator leading edge of the stator blade of [Fig.7], - [Fig.9] is a front view of a stator trailing edge of the stator blade of [Fig.7], - [Fig. 10] is a view similar to [Fig. 8], further illustrating a cross-section of the stator blade, - [Fig. 1 1] is a view similar to [Fig. 7] further illustrating a stator deflection angle, - [Fig. 12] is a view similar to [Fig. 7] further illustrating a variation of the stator deflection angle as a function of a radius, - Figure 13 is a graph illustrating the variation of a stator string as a function of a radius. - [Fig. 14] is a view similar to [Fig. 7] further illustrating a variation of a stator string as a function of a radius, according to three zones, - [Fig. 15] is a side view of a stator blade, on which are indicated the distances between the leading edge and the trailing edge, at the base and the tip of the stator blade, - [Fig. 16] is a cross-section of the stator blade illustrating a skeleton of the stator blade and an angle [3 of the stator blade cross-section, - Figure 17 is a graph of the angle [3] as a function of the radius, - [Fig. 18] is a view similar to [Fig. 1], further illustrating a distance between a rotor trailing edge and a rotor leading edge, - Figure 19 is a graph illustrating a tangential displacement of the stator blade as a function of the radius, and - Fig. 20 is a diagram illustrating the average slopes of the leading edge of the stator blade as a function of the radius. Detailed description of the invention

[0036] In the following description, when a characteristic applies to at least one element, it may also apply to all such elements. Similarly, when a characteristic applies to at least one value within a range, it may also apply to all values ​​within that range.

[0037] AERONAUTICAL PROPELLER

[0038] With reference to [Fig.1], an aeronautical propulsion unit 100 in which the invention is implemented will now be described.

[0039] The aeronautical propulsion unit 100 is designed to contribute to the propulsion of an aircraft. For example, it is intended to be supported by a pylon fixed to a wing or fuselage of the aircraft.

[0040] The aircraft propulsion unit 100 is, for example, unducted (from the English "Unducted Single Fan," also designated by the acronym USF), as in the illustrated example. However, the invention also applies to a ducted aircraft propulsion unit, such as a twin-flow turbofan, in which case the propeller is known as the fan.

[0041] The aeronautical propulsion unit 100 first of all comprises an external casing 102 and a hub 104 mounted pivoting relative to the external casing 102 around a main axis X, oriented from upstream to downstream.

[0042] Subsequently, the terms "upstream" and "downstream" will be used to specify the relative position of the elements of the aeronautical propulsion 100 along the main axis X in a flow direction of an airflow PHI when the aircraft is propelled by the aeronautical propulsion 100.

[0043] The hub 104 is thus, for example, located upstream of the external casing 102.

[0044] The aeronautical propulsion unit 100 further comprises a drive engine 105 of the hub 104. The motor 105 extends for example into the external casing 102. The motor 105 comprises for example at least one heat engine, in particular a turbomachine, a turbomotor, a turbojet or a turbofan, and / or at least one electric motor, and / or at least one hydrogen engine.

[0045] PROPELLER

[0046] The aeronautical propulsion unit 100 further comprises a propeller 106, for example unfaired, which is propulsive and mounted on the hub 104 so as to be pivotable relative to the external casing 102 around the main axis X. The propeller 106 is therefore driven in rotation around the main axis X by the motor 105 via the hub 104.

[0047] The propeller 106 is, for example, located upstream of the engine 105. In the case where the propeller 106 is unshod, such an arrangement is known as a "tractor" (from the English "puller"). Alternatively, the engine 105 could be in a "pusher" (from the English "pusher") arrangement.

[0048] During its rotation, the propeller 106 is designed to drive the airflow PHI downstream to propel the aircraft in flight. For this purpose, the propeller 106 comprises rotor blades 108 (for example, between 10 and 16, preferably between 12 and 14) arranged, for example, in a single annular row around the main axis X. The rotor blades 108 may, for example, all be identical and spaced angularly at regular intervals around the main axis X.

[0049] At least one rotor blade 108 is, for example, variable pitch, about a respective pitch axis Y, by means of a pitch change mechanism (PCM). The pitch of each rotor blade 108 is defined by a rotor pitch angle CAL about the rotor pitch axis Y. In a preferred embodiment, all the rotor blades 108 are variable pitch. This allows the rotor blade pitch 108 to be adjusted and therefore the local incidence of the flow to be adjusted according to the phase of flight.

[0050] Subsequently, the dimensions given for the rotor blades 108 will be valid for at least one pitch angle, preferably for all pitch angles within an interval of at least 10°.

[0051] Each rotor blade 108 has an external radius Re equal by definition to the distance between the main axis X and the point of the rotor blade 108 furthest from the main axis X. Each rotor blade 108 also has an internal radius Ri equal by definition to the distance between the main axis X and the point of the rotor blade 108 closest to the main axis X.

[0052] The propeller 106 thus has a diameter D equal to twice the external radius Re. This diameter D is also called the "motor diameter". The diameter D of the propeller 106 is, for example, between 1 m and 6 m, preferably between 3 m and 5 m.

[0053] RECTIFIER

[0054] The aeronautical propulsion unit 100 further includes a rectifier 112 (in English, "Outlet Guide Vane" or OGV), for example unshrouded, and mounted on the external casing 102 downstream of the propeller 106.

[0055] The rectifier 112 forms a stator fixed to the external housing 102 and extending around the main axis X, but not able to rotate around the latter. The rectifier 112 comprises stator blades 114 (for example, between 8 and 16, preferably between 10 and 14) arranged, for example, in a single annular row around the main axis X. Preferably, the number of stator blades 114 is different from the number of rotor blades 108, in order to reduce the noise of the aircraft propulsion 100. In particular, the number of rotor blades 108 is greater, for example, by at least two, than the number of stator blades 114. Indeed, if the number of rotor blades 108 and the number of stator blades 114 were equal, the wakes of the rotor blades 108 would impact simultaneously with the stator blades 114, which would increase the noise levels.The stator blades 114 may, for example, all be identical or different and spaced angularly in a regular or heterogeneous manner around the main axis X, so that at least two stator blades 114 have a different angular spacing around the main axis X.

[0056] For example, at least one stator blade 114 has variable pitch about a respective stator pitch axis Y', by means of a pitch change mechanism (PCM). The pitch of each stator blade 114 is defined by a stator pitch angle CAL' about the stator pitch axis Y'.

[0057] For example, the stator alignment axis Y' is inclined with respect to a plane perpendicular to the main axis X by an angle α between -10° and 30° preferably between 5° and 20° (angle α is positive when tilted downstream - as illustrated, and negative when tilted upstream).

[0058] An inclination of the stator alignment axis Y' makes it possible to reduce radial moments around the stator alignment axis Y', so that the alignment changing device can have a reduced mass and size.

[0059] In addition, as the stator blade 114 has a main axis of torsional rigidity, the inclination of the stator alignment axis Y' allows the mass of the stator blade 114 to be distributed around this axis, in order to keep a lever in the positioning of the natural modes of the blade to reduce vibration and aero-mechanical risks.

[0060] Furthermore, when the inclination of the stator alignment axis Y' is downstream, the amount of energy transmitted in the event of bird ingestion is distributed between the stator alignment axis Y' and a plane perpendicular to the stator alignment axis Y'.

[0061] In addition, the inclination of the stator pitch axis Y' can be very useful in the case where the propulsion system 100 is unfaired and where the stator blades 114 are strongly inclined downstream and have variable pitch.

[0062] In a preferred embodiment, all the stator blades 114 have variable pitch. This allows the pitch of the stator blades 114, and therefore the local incidence of the flow, to be adapted according to the flight phase.

[0063] The alignment axes Y, Y' are separated along the main axis X by a minimum distance dHS. The stator alignment axis Y' can be inclined at an angle of inclination a' with respect to the radial direction. This can be useful for simplifying the integration of the stator blade 114 under the external housing 102 or for reducing the aerodynamic moments around said stator alignment axis Y'. When the angle of inclination aV0°, the distance dHs corresponds to the separation between the alignment axes Y, Y' along the main axis X measured at the root sections of the rotor blade 108 and the stator blade 114, as illustrated in [Fig. 1].

[0064] Subsequently, the dimensions given for the stator blades 114 will be valid for at least one pitch angle, preferably for all pitch angles within an interval of at least 10°.

[0065] Each stator blade 114 of the rectifier 112 has an external stator radius Re' equal by definition to the distance between the main axis X and the point of the stator blade 114 furthest from the main axis X. Each stator blade 114 also has an internal stator radius Ri' equal by definition to the distance between the main axis X and the point of the stator blade 114 closest to the main axis X.

[0066] Note that the external radius Re' of two adjacent stator blades may be different depending on their azimuthal position (variable truncation or clipping). azimutally to reduce interaction noise with the propeller blade tip vortex during the attack phases).

[0067] The external casing 102 further includes a nozzle 116 for separating the primary and secondary flows, as well as a portion called a nozzle 118 between the nozzle 116 and the stator blades 114.

[0068] Rotor Blade

[0069] Subsequently, any one of the rotor blades 108 will be described in more detail, all the others being similar, for example.

[0070] With reference to [Fig.2], the rotor blade 108 first of all comprises a rotor leading edge BA where the airflow PHI arrives and a rotor trailing edge BF from which the airflow PHI departs.

[0071] The rotor trailing edge BF, for example, has serrations, i.e., a succession of undulations or teeth (a succession of peaks and troughs). The serrations improve the mixing of the propeller 106's wake before it interacts with the straightener 112, in order to reduce wake interaction noise.

[0072] The rotor leading edge BA extends from a root BA_P to a tip BA_T. The rotor leading edge BA also has a belly BA_V, which is the point of the rotor leading edge BA furthest upstream along the principal axis X, i.e., located at a greater height than the root BA_P. Thus, with this definition, a rotor blade whose furthest upstream point is located at the root BA_P would not have a belly. Similarly, the rotor trailing edge BF extends from a root BF_P to a tip BF_T.

[0073] The rotor blade 108 can also be truncated, as in the illustrated example, i.e. there is a truncated section 202, for example straight, connecting the heads BA_T, BF_T. Alternatively, the rotor blade 108 could be non-truncated, in which case the heads BA_T and BF_T would coincide.

[0074] Thus, each rotor blade 108 has an external radius Re_BA at the rotor leading edge BA, which is the distance between the main axis X and the tip BA_T of the rotor leading edge BA, and an external radius Re_BF at the rotor trailing edge BF, which is the distance between the main axis X and the tip BF_T of the rotor trailing edge BF. The external rotor radius Re of the propeller 106 is therefore equal to the larger of the external radii Re_BA and Re_BF.

[0075] Furthermore, each rotor blade 108 has an internal radius Ri_BA at the rotor leading edge BA, which is the distance between the main axis X and the root BA_P of the leading edge BA, and an internal radius Ri_BF at the rotor trailing edge BF, which is the distance between the main axis X and the root BF_P of the rotor trailing edge BF. The internal rotor radius Ri of the propeller 106 is therefore equal to the smaller of the internal radii Ri_BA and Ri_BF.

[0076] In general, it is possible to define a radius r between the principal axis X and any point outside the principal axis X. In the following description, the radius r will designate, depending on the context, a radial direction (i.e. perpendicular to the principal axis X and passing through the principal axis X) passing through this point and / or a distance along this direction between the principal axis X and this point.

[0077] ROTARY RAY

[0078] With reference to [Fig.3], it is possible to position oneself on the rotor leading edge BA from a radius r extending from the principal axis X to each point of the rotor leading edge BA. For the rotor leading edge BA, the radius r thus varies from the internal radius Ri_BA of the rotor leading edge BA to the external radius Re_BA of the rotor leading edge BA. In particular, the antinode BA_V of the rotor leading edge BA is located at a radius r denoted r(BA_V).

[0079] With reference to [Fig. 4], similarly, it is possible to position oneself on the rotor trailing edge BF from the radius r extending from the principal axis X to each point of the rotor trailing edge BF. For the rotor trailing edge BF, the radius r thus varies from the internal radius Ri_BF of the rotor trailing edge BF to the external radius Re_BF of the rotor trailing edge BF.

[0080] Thus, to locate oneself on the rotor blade 108 in its entirety, it is possible to consider the radius r varying from the internal rotor radius Ri to the external rotor radius Re. The rotor blade 108 thus has a rotor blade height H (also called rotor span) equal to Re - Ri.

[0081] The [Fig.5] is a section (also called an aerodynamic profile) at a radius r of the rotor blade 108. This section is taken along a plane P(r) perpendicular to the radius r passing through a point on the rotor leading edge B A.

[0082] As can be seen, the rotor blade 108 has an intrados face 502 and an extrados face 504, respectively concave and convex, connected to each other, upstream, by the rotor leading edge BA and, downstream, by the rotor trailing edge BF.

[0083] ROTARY ROPE

[0084] When the rotor leading edge BA and the rotor trailing edge BF are both present in the section considered, the rotor leading edge BA and the rotor trailing edge BF can be connected by a rotor chord line 506 whose orientation changes according to the radius r. The rotor leading edge BA and the rotor trailing edge BF are then separated, on the rotor chord line 506, by a distance, called the rotor chord C, which can change according to the radius r.

[0085] ROTARY ARROW ANGLE

[0086] With reference to [Fig. 6], it is also possible to define a rotor sweep angle F for the rotor blade 108, varying according to the radius r. By definition, the rotor sweep angle F is the angle between the radius r and the projection, in the plane of the radius r and the principal axis X (plane of the sheet for [Fig.6]), of the line 402 connecting the point 404 of the rotor leading edge BA at the considered radius r and the point 406 of the rotor leading edge BA at the radius r plus 1%, i.e. 1.0 Ir.

[0087] ROTARY THICKNESS

[0088] Each rotor blade 108 has a rotor thickness that varies according to the radius r. Preferably, this rotor thickness is maximum at a radius r less than: Ri + 0.2*H, preferably Ri + 0.1*H. This ensures the mechanical strength of the rotor blades 108.

[0089] STATOR PALE

[0090] Subsequently, any one of the stator blades 114 will be described in more detail. Generally speaking, the stator blades 114 may differ from one another. For example, they may have different truncations.

[0091] With reference to [Fig.7], the stator blade 114 has first of all a stator leading edge BA' where the airflow PHI from the propeller 106 arrives and a stator trailing edge BF' from which the airflow PHI departs.

[0092] The stator leading edge BA' extends from a foot BA'_P to a head BA'_T. Similarly, the stator trailing edge BF' extends from a foot BF'_P to a head BF'_T. The stator trailing edge BF' further comprises a most upstream point along the principal axis X, which may be the foot BF'_P of the stator trailing edge BF' as in the illustrated example, or a slant BF'_V located higher than the foot BF'_P.

[0093] The stator blade 114 can also be truncated, as in the illustrated example, i.e. there is a truncated section 702 for example straight, connecting the heads BA'_T, BF'_T. Alternatively, the stator blade 114 could be non-truncated, in which case the heads BA'_T, BF'_T would coincide.

[0094] Thus, each stator blade 114 has an external radius Re'_BA at the stator leading edge BA', which is the distance between the principal axis X and the tip BA'_T of the stator leading edge BA', and an external radius Re'_BF at the stator trailing edge BF', which is the distance between the principal axis X and the tip BF'_T of the stator trailing edge BF'. The external stator radius Re' of the rectifier 112 therefore extends between the principal axis X and the furthest of the tips BA'_T, BF'_T. Note that the external radii Re', Re'_BA, Re'_BF of two adjacent stator blades can be different depending on their azimuthal position (azimutally variable truncation or clipping) to reduce interaction noise with the propeller blade tip vortex during the attack phases.

[0095] In addition, the stator blade 114 has an internal radius Ri'_BA at the stator leading edge BA' which is the distance between the principal axis X and the foot BA'_P of the stator leading edge BA', as well as an internal radius Ri'_BF at the stator trailing edge BF' which is the distance between the principal axis X and the foot BF'_P of the stator trailing edge BF'. The internal stator radius Ri' of the stator blade 114 is therefore equal to the smallest of the internal radii Ri'_BA, Ri'_BF.

[0096] Thus, preferably, the rectifier 112 is unfaired and the truncated section 702 of a stator blade 114 is such that: .¾^.1 > Q Q5

[0097] In this way, the stator outer radius Re' is less than the rotor outer radius Re, so that the vortices of the propeller 106 can more easily pass, at least in part, over the rectifier 112.

[0098] STATORIC RADIUS

[0099] With reference to [Fig. 8], it is possible to position oneself on the stator leading edge BA' from the radius r extending from the principal axis X to each point of the stator leading edge BA'. For the stator leading edge BA', the radius r thus varies from the internal radius Ri'_BA of the stator leading edge BA' to the external radius Re'_BA of the stator leading edge BA'.

[0100] With reference to [Fig. 9], it is similarly possible to position oneself on the stator trailing edge BF' from the radius r extending from the principal axis X to each point of the stator trailing edge BF'. For the stator trailing edge BF', the radius r thus varies from the internal radius Ri'_BF of the stator trailing edge BF' to the external radius Re'_BF of the stator trailing edge BF'.

[0101] Thus, to locate the entire stator blade 114, it is possible to consider the radius r varying from the internal stator radius Ri' to the external stator radius Re'. The stator blade 114 therefore has a stator blade height H' (also called stator span) equal to Re' - Ri'.

[0102] The [Fig. 10] is a section (also called an aerodynamic profile) at a radius r of the stator blade 114. This section is taken along a plane P(r) perpendicular to the radius r extending from the principal axis X to a point on the leading edge BA'.

[0103] As can be seen, the stator blade 114 has an intrados face 1002 and an extrados face 1004, respectively concave and convex, connected to each other, upstream, by the stator leading edge B A' and, downstream, by the stator trailing edge BF'.

[0104] STATOR STRING

[0105] When the stator leading edge BA' and the stator trailing edge BF' are both present in the section considered, the stator leading edge BA' and the stator trailing edge BF' can be connected by a stator chord line 1006 whose orientation changes according to the radius r. The stator leading edge BA' and the stator trailing edge BF' are then separated, on the stator chord line 1006, by a distance, called the stator chord C', which can change according to the radius r.

[0106] STATORIC DRAFT ANGLE

[0107] With reference to [Fig. 11], it is also possible to define a stator deflection angle F' for the stator blade 114, varying according to the radius r. By definition, the stator deflection angle F' is the angle between the radius r and the projection, in the plane of the radius r and the principal axis X (plane of the sheet for [Fig. 11]), of the line 1102 connecting the point 1004 of the stator leading edge BA' at the considered radius r and the point 1106 of the stator leading edge BA' at the radius r plus 1%, i.e. l,01r.

[0108] STATIC THICKNESS

[0109] Each stator blade 114 has a stator thickness that varies according to the radius r. Preferably, this stator thickness is maximum at a radius less than: Ri' + 0.2*H', preferably Ri' + 0.1*H'. This ensures the mechanical strength of the stator blades 114.

[0110] DIMENSIONS

[0111] Various dimensioning characteristics of the propeller 106 and the rectifier 112 will now be described.

[0112] With reference to [Fig. 12], for at least one stator blade 114, the stator deflection angle F' is positive and increasing monotonically over the entire stator blade height H', increasing strictly monotonically over at least a part of the stator blade height H' and greater than 30° over at least 40% of the stator blade height H'.

[0113] Thus, the deflection angle F' can be low at the base of the stator blade, and high at the top of the stator blade.

[0114] This offers several advantages, as mentioned in the introduction. First, during flight phases at an angle of attack, the airflow tends to separate at the stator leading edge BA' when the sweep angle is significant. Thus, thanks to the invention, separation would only occur locally at the tip of the stator blade 114, which can improve aerodynamic performance compared to the constant-sweep stator blade (straight stator leading edge) mentioned above, for which separation would occur at a smaller radius and affect a larger portion of the stator leading edge.

[0115] According to another possible feature, the stator leading edge BA' has a midpoint BA'_M located at half the height of the stator blade H'. There is thus a straight line passing through the foot BA'_P and the midpoint BA'_M having an angle ôa with a plane perpendicular to the principal axis X. There is also a straight line passing through the midpoint BA'_M and the head BA'_T having an angle ôb with a plane perpendicular to the principal axis X. Under these conditions, the angle ôb is preferably greater than the angle ôa.

[0116] According to another possible feature, the stator leading edge BA' has a low intermediate point BA'_IB located at one-third of the stator blade height H' and an upper intermediate point BA'_IH located at two-thirds of the height of the stator blade H'. There is thus a straight line passing through the base BA'_P and the lower intermediate point BA'_IB forming an angle ôc with a plane perpendicular to the principal axis X. There is also a straight line passing through the lower intermediate point BA'_IB and the upper intermediate point BA'_IH forming an angle ôd with a plane perpendicular to the principal axis X. Furthermore, there is a straight line passing through the upper intermediate point BA'_IH and the head BA'_T forming an angle ôe with a plane perpendicular to the principal axis X. Under these conditions, the angle ôe is preferably greater than the angle ôd, which itself is preferably greater than the angle ôc.

[0117] With reference to Figure 13, as explained previously, the stator string C' varies as a function of the radius r. Thus, it is possible to calculate the mathematical area under the curve of the stator string C' as a function of the radius r, above and below the maximum of C', called C'max and reached at the radius r(C'max): [Re, . and rAC max), s-high = J ^Cnwxf'(r)dr S_low = J C'(r)dr J Kl

[0118] With the absence of a slack at the stator leading edge BA', that is, with the foot BA'_P of the stator leading edge BA as the upstream point of the stator leading edge BA' as proposed above, the upper area S_area will be greater than the lower area S_area. Thus, according to another possible characteristic, i SJtaui preference r, ijsj,a$ 77^ Sjiutd According to another possible characteristic, SJuatt I prefer Sbas S_bas u still S_high. S-bas

[0119] The advantage of this feature is that it allows for a greater chord length on the lower part of the stator 114, but not necessarily on the root section (because a large chord length on the root section can increase aerodynamic losses due to interaction with the boundary layer on the hub and the increased percentage of overhanging chord length at the root of the stator blade 114). Indeed, to reduce propeller noise 106, it is preferable to unload the propeller head (i.e., reduce the pressure difference between the lower and upper surfaces) so that the maximum aerodynamic load is placed at lower radii. This implies that the stator 112 has a larger chord length on its lower part to better compensate for gyration in the flow and maximize aerodynamic efficiency, but not on the root section.

[0120] According to another possible feature, the maximum stator string C' is located between 10% and 35% of the stator blade height H'. This allows for a stator deflection angle F' that increases monotonically or strictly monotonically from the radial position corresponding to the maximum stator string C' and to have a large stator sweep angle F' close to the stator blade head at the leading edge BA'_T.

[0121] According to another possible feature, the belly BF'_V of the stator trailing edge BF' is located below 50% of the stator blade height H' (extending as explained previously from the foot section of the stator blade 114), preferably below 40% of the stator blade height H'.

[0122] This allows the BF'_V belly to be at a blade height relatively close to a transition zone between a small sweep angle under the lower portion of the blade and a larger sweep angle over the upper portion of the blade. This can be useful in some cases to increase the chord on the lower part and improve mechanical strength.

[0123] According to another possible characteristic, the maximum stator chord C' is located at the height of the antinode BF'_V, within 5% of the stator blade height H'. Having a significant chord at the antinode BF can be useful for improving mechanical strength because the antinode BF is an area of ​​high stress concentration.

[0124] According to another possible characteristic, with reference to [Fig. 14], the stator string C' evolves with the radius r according to three intervals, which may or may not be adjacent, of the radius r:

[0125] interval ZI (from 0% to at least 15% of the stator blade height H'): the string C' increases in a strictly monotonic way with the radius r;

[0126] interval Z2 (from 40% up to at least 60% and at most 85% of the blade height H'): the stator string C' decreases in a strictly monotonic manner with the radius r; and

[0127] interval Z3 (from 85% to 100% of the stator blade height H'): the stator string C' decreases in a strictly monotonic manner with the radius r, with an average decay rate at least twice as large between 85% and 95% as between 40% and 60%, i.e.: C'(0.85*H4C1a95*H') c(0.4*H>Q0.6*ir), which can also 0.2 *H' to write: C(r=«i+0.85*ff\c(r=RÏ+Q,95*H:) 02 *H'

[0128] This evolution of the stator string C' makes it possible to increase the sag F' locally near the head of the stator blade 114, which is interesting for minimizing vortex interaction noise.

[0129] According to another possible characteristic, the stator string C' is, for any radius r, between 5% and 45% of the stator blade height H': g Q5 < < g 45' Allows for variations in the stator string C' along of the stator blade height H' compatible with a high stator deflection angle F' over a large part of the stator blade height H'.

[0130] According to another possible feature, the stator sweep angle F' is constant over a height between 10% and 50% of the stator blade height H', this height preferably being located above 50% of the stator blade height H'. This simplifies the manufacturing process and avoids a large downstream offset of the tip cuts, which could increase interaction noise with the vortex generated at the rotor blade tip 108. Indeed, the envelope of the (helical) trajectory of the propeller tip vortex contracts as it moves away from the propeller plane, due to the contraction of the stream tube. In other words, as it moves away from the propeller plane, the vortex shifts to lower radial positions.

[0131] According to another possible feature, the stator leading edge BA' and / or the stator trailing edge BF' extend only downstream. In other words, the points of the stator leading edge BA' and / or the stator trailing edge BF' have a position along the principal axis X that increases strictly with height. Thus, the stator blade 114 has no bulge on the leading edge BA' and / or on the trailing edge BF', which improves mechanical strength and simplifies the manufacturing process of the stator blade 114. From an acoustic point of view, it is also beneficial not to have a bulge on the leading edge BA' and on the trailing edge BF' because a bulge is characterized by a zone of zero sweep angle, on which the noise sources will all be correlated, i.e., in phase, which is likely to increase the noise.

[0132] With reference to [Fig. 15], according to one possible characteristic, Axmid > Axpied, preferably Axmid > l,l*Axpied, where Axpied is the axial distance (along the principal axis X) between the leading edge BA' and the trailing edge BF' at 5% of the stator blade height H' and Axmid is the axial distance between the trailing edge BF' measured at 5% of the stator blade height H' and the leading edge BA' at 95% of the stator blade height H'. This ensures a large Axmid distance, which allows for a steep downstream inclination of the stator blade 114, while controlling (or minimizing) the chord C' near the foot cut. As discussed previously, a steep inclination of the stator blade 114 indicates a steep sweep which is favorable for noise reduction, and a relatively small root chord (or at least a root chord that does not correspond to the maximum chord) is beneficial from an aerodynamic point of view.

[0133] According to one possible characteristic, Axhead < Axmid, preferably Axhead < 0.8*Axmid, where Axhead is the axial distance between the leading edge BA' at 95% of the stator blade height H' and the trailing edge BF' at 100% of the blade height stator H'. This ensures that the stator head is not set too far back. If it is, the stator blade head 114 could be impacted by the leading edge vortex of a rotor blade 108 originating from the propeller, which could increase vortex interaction noise. As a reminder, the envelope of the (helical) trajectory of the propeller leading edge vortex contracts as it moves away from the propeller plane, due to the contraction of the stream tube. In other words, as it moves away from the propeller plane, the vortex shifts to lower radial positions.

[0134] According to another possible feature, at any radius r above the radius where the BA_V belly of the leading edge BA of the rotor blade 108 is located (r > r(BA_V)), the stator sweep angle F' is greater than or equal to the rotor sweep angle F. During high-attack, high-thrust flight phases, such as takeoff, the flow around the propeller tends to separate above the BA belly, which can increase noise. Having an even greater sweep angle on the BA trail of the OGV is therefore beneficial for reducing wake interaction noise.

[0135] According to another possible feature, the serrations of the rotor trailing edge BF begin at a radius smaller than the radius r(BA_V) of the belly BA_V of the rotor leading edge BA. Below the radial position of the belly BA_V of the rotor blades 108, the sweep angle F' of the stator blades 114 is smaller and the serrations of the rotor trailing edge BF can contribute effectively to wake mixing, phase shifting and wake interaction noise reduction.

[0136] According to another possible feature, the serrations of the rotor trailing edge BF are located opposite a zone in the radial direction with a low stator sweep angle F', where F' is less than 30°, preferably less than 25°. This helps to mix the wake and thus reduce interaction noise in a zone with a low stator sweep angle F', i.e., a zone where interaction noise is significant. Furthermore, this limits the radial extension of the serrations on the rotor trailing edge BF, which simplifies the manufacturing process and improves the mechanical strength of the rotor blade 108.

[0137] According to another possible feature, the serrations of the rotor trailing edge BF extend over a height less than 60% of the stator blade height H'. This is useful for noise reduction while limiting the radial extension of the serrations on the rotor trailing edge BF, which simplifies the manufacturing process and improves the mechanical strength of the rotor blade 108.

[0138] With reference to [Fig. 16], for each cross-section of the stator blade 114, it is possible to define a skeleton 1902, such as the mid-distance curve between the intrados 1002 and the extrados 1004. The skeleton 1902 can, for example, be obtained, as illustrated in [Fig. 16], as the set of centers of circles inscribed in the cross-section, i.e. said to be flush with both the intrados 1002 and the extrados 1004. At the stator leading edge BA', the skeleton 1902 makes an angle [3 with the principal axis X (that is to say that the angle [3 is the angle, in the plane P(r), between the principal axis X and a tangent to the skeleton 1902 at the stator leading edge BA') which varies according to the radius r, in order to adapt the profiles to the over-incidences / under-incidences linked to the effects of positive / negative sweep, respectively. For example, increasing the sweep angle F' at the stator leading edge BA' increases the local incidence on the aerodynamic profiles of the stator blade 114. This over-incidence must therefore be compensated by an increase in the absolute value of the angle [3, which realigns the skeleton with the incident flow and avoids separations which can have a negative impact on aerodynamic performance and noise.

[0139] According to another possible characteristic, the absolute value of the angle [3 is increasing (for example strictly increasing) with the radius r. Indeed, when the sweep angle F' increases, it is useful to increase the absolute value of the angle [3 of the stator leading edge BA' (closing) to reduce the incidence locally and avoid separations, which could deteriorate aerodynamic performance and increase some of the self-noise and / or noise.

[0140] According to another possible characteristic, the absolute value of the angle [3 varies, over the entire height of the stator blade H', between 12° and 30° at most.

[0141] Fig. 17 illustrates three examples of variation of the angle [3.

[0142] According to another possible feature, the stator deflection angle F' is greater than 20° over at least 60% of the stator blade height H' and / or greater than 30° over at least 40% of the stator blade height H' and greater than 40° over at least 10% of the stator blade height H'. Thus, the stator deflection angle F' is very high over a very large portion of the stator blade height H'.

[0143] According to another possible feature, when the stator blade 114 has variable pitch, the flow PHI exerts, over the entire flight envelope, a moment resulting from pressure and friction forces around the pitch axis Y' of less than 500 N*m, in particular less than 400 N*m. This ensures the proper functioning of the hydraulic system and the actuators responsible for adapting the pitch of the stator blade 114 according to the operating point in order to maximize aerodynamic performance (avoiding liftoff) and reduce noise. If the moments are too high, the system would not be able to rotate the stator blade 114 to adapt the pitch, or the system would be too heavy and therefore impractical on an aircraft engine.

[0144] According to another possible feature, the stator deflection angle F' is at least 45° at at least one point on the stator leading edge BA' above a midpoint BA'_M located at half the stator blade height H'. This allows reduce the interaction noise of the vortex at the tip of the rotor blade 108 with the head of the stator blade 114.

[0145] With reference to [Fig. 18], there exists, at each radius r, a spacing L(r) between the rotor trailing edge BF and the stator leading edge BA', having a maximum max{L(r)} and a minimum min{L(r)}.

[0146] According to another possible characteristic, the spacing L(r) increases in a strictly monotonic way with the radius r and 1.5 < max{L(r)} / min{L(r)} < 4, preferably 2.1 < max{L(r)} / min{L(r)} < 3. Increasing the distances between the propeller 108 and the straightener 112 allows for better dissipation of the wake of the propeller 108 and therefore reduces interaction noise.

[0147] According to another possible feature, at any radius r above the radius of the BA_V belly of the rotor leading edge BA (r > r(BA_V)), the stator sweep angle F' is greater than or equal to the rotor sweep angle F. During high-attack, high-thrust flight phases, such as takeoff, the flow around the propeller 108 tends to separate above the BA_V belly of the rotor leading edge BA, which can increase noise. Having an even larger stator sweep angle on the stator leading edge BA' is therefore beneficial for reducing interaction noise.

[0148] According to another possible feature, the stator leading edge BA' has a tangential displacement yBA' in the azimuthal direction having a local maximum yBA'ext on the extrados side reached in a radius rext (see [Fig. 19]) to maximize noise reduction.

[0149] According to another possible characteristic, the relative height of the local maximum or minimum extremum of yBA', defined as », will be Hextremumy^ - rBArrBAp preferably between 5% and 50%.

[0150] According to another possible characteristic, the relative amplitude of the law of yBA' defined as ysA^ will be between 0% and 10%, preferably between 1% and 5%.

[0151] According to another possible feature, the serrations of the rotor trailing edge BF are only located above 10% of the rotor blade height H and below 60% of the rotor blade height H. This allows for better dissipation of the propeller wakes before they interact with the area of ​​the OGV having a low sweep angle (which is related to dominant noise sources).

[0152] CONCLUSION

[0153] In conclusion, it should be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various Modifications may be made to the embodiments described above, in light of the teaching which has just been disclosed to him.

[0154] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands

1. A faired or unfaired aircraft propulsion system (100) comprising: - an outer casing (102); - a hub (104) mounted pivotally relative to the outer casing (102) about a principal axis (X) extending in an upstream-downstream direction of the aircraft; - a propeller (106) mounted on the hub (104) to rotate relative to the outer casing (102);and - a rectifier (112) mounted on the external casing (102) downstream of the propulsion propeller (106) along the main axis (X), the rectifier (112) extending around the main axis (X), the rectifier (112) comprising stator blades (114) each having: a stator leading edge (BA'), a stator internal radius (Ri'), a stator external radius (Re'), a stator blade height (H') equal to the difference between the stator external radius (Re') and the stator internal radius (Ri'), and a stator sweep angle (F') at each point of the stator leading edge (BA'); characterized in that, for at least one stator blade (114), the stator deflection angle (F') is positive and increasing over the entire height of the stator blade (H'), strictly increasing over at least a part of the height of the stator blade (H') and greater than 30° over at least 40% of the height of the stator blade (H').;

2. Aeronautical propellant (100) according to claim 1, wherein 1 S_high , preferably 97. S_high , with S_high and S_low sbax Shas correspond to the mathematical area under a stator chord (C') as a function of a radius (r) with respect to the principal axis (X), above and below the belly (BA'_V) of the stator leading edge (BA'), respectively.

3. Aeronautical propulsion system (100) according to claim 1 or 2, wherein SJwut < g, preferably < 45, with S_top and S_bottom correspond to the mathematical area under a stator chord (C') as a function of a radius (r) with respect to the principal axis (X), above and below the belly (BA'_V) of the stator leading edge (BA'), respectively.

4. An aeronautical propulsion system (100) according to any one of claims 1 to 3, wherein the stator leading edge (BA') has a lower intermediate point (BA'_IB) located at one-third of the stator blade height (H') and a higher intermediate point (BA'_IH) located at two-thirds of the stator blade height (H'), such that there exists a straight line passing through the base (BA'_P) and the lower intermediate point (BA'_IB) having an angle θc with a plane perpendicular to the principal axis (X), and furthermore, there exists a straight line passing through the lower intermediate point (BA'_IB) and the higher intermediate point (BA'_IH) having an angle θd with a plane perpendicular to the principal axis (X), and furthermore, there exists a straight line passing through the upper intermediate point (BA'_IH) and the tip (BA'_T) having an angle θe with a plane perpendicular to the principal axis (X), and in which the angle ôe is greater than the angle ôd and / or the angle ôd is greater than the angle ôc.

5. Aeronautical propulsion (100) according to any one of claims 1 to 4, wherein the maximum (C'max) of a stator chord (C') is between 10% and 35% of the stator blade height (H').

6. Aeronautical propulsion (100) according to any one of claims 1 to 5, wherein the stator trailing edge (BF') has a belly (BF'_V) located below 50% of the stator blade height (H'), preferably below 40% of the stator blade height (H') or wherein the stator trailing edge (BF') has a toe (BF'_P) which is the most upstream point of the stator trailing edge (BF').

7. Aeronautical propulsion (100) according to any one of claims 1 to 6, wherein the stator chord (C') decreases in a strictly monotonic manner with the radius (r), with an average rate of decrease at least twice as large between 85% and 95% as between 40% and 60% of the stator blade height (H').

8. Aeronautical propulsion (100) according to any one of claims 1 to 7, wherein the stator sweep angle (F') is constant over a height between 10% and 50% of the stator blade height (H').

9. Aeronautical propulsion (100) according to any one of claims 1 to 8, wherein the stator leading edge (BA') and / or the stator trailing edge (BF') extend only downstream with the radius (r).

10. Aeronautical propulsion system (100) according to any one of claims 1 to 9, wherein: Axmid > Axpied, preferably Axmid > 1.1*Axpied, where Axpied is the axial distance, along the principal axis (X), between the stator leading edge (BA') and the stator trailing edge (BF') at 5% of the stator blade height (H') and Axmid is the axial distance between the stator trailing edge (BF') measured at 5% of the stator blade height (H') and the stator leading edge (BA') at 95% of the stator blade height (H') or wherein: Axtête < Axmid, preferably Axtête < 0.8*Axmid, where Axtête is the axial distance between the stator leading edge (BA') at 95% stator blade height (H') and trailing edge (BF') at 100% of stator blade height (H').

11. Aeronautical propulsion (100) according to any one of claims 1 to 10, wherein the stator sweep angle (F') is greater than 20° over at least 60% of the stator blade height (H') and / or greater than 30° over at least 40% of the stator blade height (H') and greater than 40° over at least 10% of the stator blade height (H').

12. Aeronautical propulsion (100) according to any one of claims 1 to 11, wherein, the stator blade (114) being variable pitch, an airflow (PHI) driven by the propeller (108) exerts, over the whole of a flight domain of an aircraft equipped with the aeronautical propulsion (100), a moment resulting from pressure and friction forces, around a stator pitch axis (Y') of less than 500N*m, in particular less than 400N*m.

13. Aeronautical propulsion (100) according to any one of claims 1 to 12, wherein, the rotor trailing edge BF and the stator leading edge BA' being separated, at each radius (r), by a spacing (L(r)) having a maximum max{L(r)} and a minimum min{L(r)}, the spacing (L(r)) is strictly monotonic and 1.5 < max{L(r)} / min{L(r)} < 4, preferably 2.1 < max{L(r)} / min{L(r)} < 3.

14. Aeronautical propulsion (100) according to any one of claims 1 to 13, wherein, at any radius (r) above a radius of the belly (BA_V) of a rotor leading edge (BA), the stator deflection angle (F') is greater than or equal to the rotor deflection angle (F).

15. Aeronautical propulsion (100) according to any one of claims 1 to 14, wherein, the stator blade (114) having for each cut perpendicular to a radius (r) with respect to the principal axis (X), a skeleton (1902) as the mid-distance curve of an intrados (1002) and an extrados (1004) of the stator blade (114), the skeleton (1902) making, at the stator leading edge (BA'), an angle [3 with the principal axis (X), the absolute value of the angle [3 is strictly increasing with the radius (r).

16. Aeronautical propulsion (100) according to any one of claims 1 to 15, wherein the stator leading edge (BA') having a tangential displacement (yBA') in an azimuthal direction, having a local maximum (yBA'ext) on the side of an extrados of the stator blade (114) reaches in a radius rext, a relative height of the local maximum (yBA'ext) of the tangential displacement (yBA'), defined as: i, _ is between 5% and 50%.

17. Aeronautical propulsion (100) according to any one of claims 1 to 16, wherein the propeller (106) comprises at least one rotor blade (108) with a rotor trailing edge (BF) having serrations only located above 10% of a rotor blade height (H) and below my smallest radial position between 60% of the rotor blade height (H) and a radius (r(BA_V)) of the belly (BA_V) of the rotor leading edge (BA).

18. Aeronautical propulsion (100) according to any one of claims 1 to 17, wherein, the stator leading edge (BA') having a tangential displacement (yBA') in an azimuthal direction having a local maximum yBA'ext on the side of an extrados of the stator blade (114), the relative amplitude defined as (yBA'ext) / H' shall be between 0% and 10%, preferably between 1% and 5%, where H' is the stator blade height.

19. Aircraft comprising an aeronautical propulsion system (100) according to any one of the preceding claims.

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