Aviation thruster with improved integration

Abstract

Aviation thruster (40) having a longitudinal axis (X) and comprising unducted blades (18) of an upstream rotor row and a downstream stator row (16). Two adjacent blades of the downstream stator row (16) have an azimuthal spacing ([Delta] [Theta]) around the longitudinal axis (X) between which the blades are positioned one by one on both sides of the attachment structure (27) and / or the projection (270) in a plane perpendicular to the longitudinal axis (X), and the blades are positioned one by one on both sides of the attachment structure (27) and / or the projection (270) on both sides of the attachment structure (27) and / or the projection (270). The azimuthal spacing ([delta] [theta]) is between 1 DEG and 75 DEG greater than a minimum azimuthal spacing in the stator blades (16) present in the downstream stator row.

Description

Field of the Invention

[0001] The present disclosure relates to the field of aviation propellers having a longitudinal axis, each propeller comprising a hub and (at least) two annular rows of ductedless blades along the longitudinal axis, one row being upstream and the other row being downstream.

[0002] According to the foregoing and the following, throughout this text, the relative terms "upstream" and "downstream" are defined relative to each other with reference to the flow of gases in a turbomachine during the cruise flight phase in the longitudinal direction (i.e., the direction of the longitudinal axis).

[0003] An aviation propeller may include (at least) one thermal engine, specifically, a turbomachine, a turboprop, a turbojet, a turbofan, and / or (at least) one electric engine, and / or (at least) one hydrogen engine, and / or (at least) one hybrid engine: thermal and / or electric and / or hydrogen engines. Background Art

[0004] In the following, the case of a turbomachine will be more specifically and thus non - restrictively referred to, since the type of engine included in the propeller is not a determining factor here. A turbomachine is understood here to mean a propeller in which there is an energy exchange between the flowing fluid and the rotor.

[0005] In this context, it will be recalled by way of example that a turbomachine with a "ductedless" fan (or a turboprop of the "propeller" or "open fan" or "open rotor" or "counter - rotating open rotor" type) is a type of turbomachine in which the fan extends outside the engine casing (or nacelle), which is different from a conventional turbomachine with a ducted fan ("turbofan" type).

[0006] The absence of a duct (such as in a ductedless turbomachine) results in an increase in the noise level emitted by the aviation propeller, which generally includes at least one upstream rotor row, the blades of which have an impact on the blades of the downstream stator row.

[0007] In fact, the noise generated by the annular rows of ductedless blades propagates in the free field. The main cause of the noise emission is related to the vortex structures generated in the air flow at the free radial outer tips of the blades in the rotor row. These blade tip vortices can interact with the blades of the downstream stator row.

[0008] One of the challenges of these architectures is the certification of the noise level during take - off and landing operations. The noise level emitted by an aircraft is subject to increasingly strict regulations.

[0009] In addition, important considerations may be the presence of combinations of the following, ensuring the integration of the propeller, specifically, its blade pitch change system (if it has a blade pitch change system):

[0010] - A pylon, or strut, or engine mount (see "attachment structure" below) for fixing this propeller to the airfoil or fuselage of the aircraft to be propelled, and

[0011] - Specifically, a protrusion on the attachment structure that locally changes the flow around the attachment structure.

[0012] This specification aims to propose technical solutions to these drawbacks. Summary of the Invention

[0013] At this stage, it should be immediately stated that even though the above-mentioned prior art thus relates to a turbomachine, the technical solutions of the present invention are still applicable to any ducted and / or "open rotor" type of aircraft propeller, because part of the above problems is not necessarily specific to the above type of aircraft propeller.

[0014] In this context, therefore, a propulsion assembly for an aircraft is proposed, here and generally:

[0015] - The assembly includes an aircraft propeller having a longitudinal axis (X) and including a housing, and an upstream annular row of ducted rotor blades spaced apart from each other along the longitudinal axis (X) and a downstream stator row of ducted stator blades extending around the housing, with an azimuthal pitch (Δθ, Δθ i ) defined by an angle between corresponding axes around the longitudinal axis (X) between two adjacent blades of the stator row of the downstream stator row:

[0016] - When these axes are projected onto a plane perpendicular to the longitudinal axis (X), and in the case where the two adjacent blades have variable pitch angles, these corresponding axes are the pitch angle adaptation axes of the two adjacent blades,

[0017] - Or in the case where the two adjacent blades have fixed pitch angles, these corresponding axes are axes that are respectively radial to the longitudinal axis (X) and pass through the radially inner ends or radially outer ends of the two adjacent blades,

[0018] - Or, when one of the two adjacent blades has a variable pitch angle, for one of the corresponding axes, it is the pitch angle adaptation axis of the blade, and when the blade has a fixed pitch angle, the other of the corresponding axes is radial to the longitudinal axis (X) and passes through the radially inner end or through the radially outer end or through the center of gravity,

[0019] - The assembly further includes an attachment structure for attaching the aero - thruster to the aircraft, the attachment structure being fixed to the housing, and when observed in a plane (P1) perpendicular to the longitudinal axis (X) and preferably at least (partially) intersecting one of the blades of the downstream stator row, the attachment structure has or defines a protrusion that extends between or is axially adjacent to two of the stator blades of the downstream stator row, and

[0020] - Around the longitudinal axis (X), the angular position at 12 o'clock is defined as being vertically upward relative to the longitudinal axis (X), and the angular position at 6 o'clock is defined as being vertically downward relative to the longitudinal axis (X).

[0021] The assembly is characterized in that when the two adjacent blades are located one on each side of the attachment structure and / or the protrusion, in a plane perpendicular to the longitudinal axis (X), the azimuthal angular pitch ratio between the two adjacent blades is greater than the minimum azimuthal angular pitch existing among the stator blades of the downstream stator row by between 1° and 75°, preferably between 5° and 40°, or more preferably between 8° and 20°.

[0022] In another way of expressing: when the two adjacent blades are located one on each side of the attachment structure and / or the protrusion, in a plane perpendicular to the longitudinal axis (X), the azimuthal angular pitch between the two adjacent blades extends azimuthally (or circumferentially around the longitudinal axis X) within an angular sector that is greater than the minimum azimuthal angular pitch existing among the stator blades of the downstream stator row by between 1° and 75°, preferably between 5° and 40°, or more preferably between 8° and 20°.

[0023] In yet another way of expressing:

[0024] - The distribution of the stator blades around the longitudinal axis (X) of the aero - thruster is non - uniform; at least some of the azimuthal angular pitches of the stator blades are different from each other. Here, non - uniform, non - homogeneous, irregular, and non - uniform are synonyms with respect to this azimuthal distribution around the longitudinal axis X, and

[0025] - In the above - mentioned case, it means that in the nacelle, specifically, in the presence of pylons, engine mounts, or struts, it may be useful to provide an azimuthal angular pitch such that Δθ i or Δθ j increases between two stator blades on either side of the attachment structure and / or the protrusion.

[0026] A synonym for the projection is: the hub, which is non-axisymmetric about the longitudinal axis X and, when observed in a plane (P1) perpendicular to said longitudinal axis (X), preferably intersects at least (partially) one of the blades of the downstream stator row.

[0027] Advantageously, the assembly may include at least three different azimuthal spacings. Implementing at least three different azimuthal spacings helps integrate the projection and other additional equipment such as fuel tanks, fuel pumps or oil pumps, actuators or pitch angle adjustment systems into the nacelle. In addition, in addition to integrating the projection, a configuration with at least three different azimuthal spacings also allows a wider azimuthal spacing to be implemented in areas with turbulence (e.g., in the lower part of the assembly), thereby reducing noise generation during operation.

[0028] In this text, Δθ i and Δθ j respectively define two different azimuthal spacings between any two adjacent blades. i and j are indices (natural numbers: i, j = 1, 2,...), which are different when i ≠ j and less than or equal to the number of stator blades (i, j ≤ V), where V defines the number of blades in the stator blades of the downstream stator row. In other words: i and j are different and can take (any) integer values from 1, 2, 3,... and (at most) V. And, only when all azimuthal spacings are different / non-uniform, i or j can take the value i = V or j = V. Thus, for example, as in Figure 14 Δθ i can be equal to Δθ1, Δθ2, Δθ3, Δθ4 or Δθ5. As is conventional, the positions 3 o'clock, 6 o'clock, 9 o'clock, 12 o'clock are considered on the clock face and are oriented clockwise, as observed when facing the propeller or aircraft in question from upstream / front.

[0029] Also as is conventional, the pitch angle of the blade can be the angle formed by the chord of one of the profiles and the plane of rotation of the blade. Since the blade is designed to be twisted, by convention, we say that the pitch is the pitch of the profile located at 70% of the maximum radius.

[0030] From an “integration” perspective, the non-uniform distribution of stator vanes thus makes it possible to bypass auxiliary equipment below the casing or hub, in order to reduce the pressure buildup at the airfoil / lift surface downstream of the stator vanes, and / or to avoid the interaction between the stator wake and the airfoil, and, where appropriate, to accommodate the integration of the pylon. It should be noted that for a USF type architecture, the pylon can be located upstream of the rotor / stator vanes (referred to as a “pusher” configuration), which is different from the preferred “tractor” configuration where the pylon is at the level of the stator vanes or downstream thereof. From an acoustic perspective, one advantage of the “tractor” configuration is that it avoids the effect of the pylon wake on all the rotor blades. From an aerodynamic perspective, one advantage of the “tractor” configuration is that it does not introduce distortions or non-uniformities into the airflow upstream of the rotor, the introduction of which can degrade performance and increase the phenomenon of vibration response on the rotor blades.

[0031] Furthermore, the various technical solutions of the prior art are generally only relatively suitable in the isolation configuration of the turbomachine and at zero angle of attack. In fact, the presence of surrounding elements (struts, fuselage, airfoils, flaps, etc.), the non-zero angle of attack of the airflow sensed by the pusher, and the shape of the blades in the upstream rotor row can, on the one hand, modify the contraction and axial symmetry of the airflow around the longitudinal axis X of the flow tube downstream of the upstream rotor row, and / or, on the other hand, modify the size of the vortices present in the airflow downstream of the upstream rotor row, such that the truncation of the blades of the downstream stator row defined based on the isolation configuration and at zero angle of attack no longer prevents the interaction between the blades of the downstream stator row and the vortices formed by the blades of the upstream rotor row.

[0032] To perfect the integration and further improve the aerodynamics, and thus also to reduce the emitted noise, it has even been proposed to attach a structure to (i.e., integrate) one of the blades of the downstream stator row in order to form a single aerodynamic assembly together.

[0033] It should be noted that this must be compatible with the fact that the maximum azimuthal pitch over the entire circumference of the stator vanes (row) can be between two blades arranged one on each side of an attachment structure (strut, engine mount, pylon, etc.).

[0034] To focus on dealing with this integration problem of the pusher into the environment of the protrusion and to avoid weakening effects, it has also been proposed that:

[0035] - the azimuthal pitch between two adjacent blades, one on each side of the protrusion, respectively, in the series of blades of the downstream stator row is greater than any other azimuthal pitch between any other pair of adjacent blades of the downstream stator row, and / or

[0036] - Except for two adjacent blades in a pair, each located on one side of the protrusion respectively on both sides of the blade series of the downstream stator row, all pairs of adjacent blades of the downstream stator row have the same azimuthal pitch.

[0037] It should be noted that herein, and hereinafter, when the expression "each located on one side of the protrusion (reference numeral 270 in the following description) on both sides" is used, this will be interpreted as also including "and / or each located on one side of the attachment structure (reference numeral 27 in the following description) on both sides".

[0038] Also, in order to balance the weight of the thruster and avoid residual moments on the longitudinal axis X related to the non-uniform distribution of the stator blades, it is further proposed that the blades of the downstream stator row are azimuthally positioned symmetrically with respect to the axis (A1 or A2), and thus around the longitudinal axis (X), the axis (A1 or A2) being perpendicular to the longitudinal axis (X) and passing through the attachment structure and / or the protrusion. It should be noted that this is an axis that can be included in the plane P1.

[0039] To continue moving forward towards the effective / simpler integration of the thruster on the aircraft, the attachment structure (pylon or others) can be inclined at an angle δ≠0° with respect to the 12 o'clock - 6 o'clock axis in a plane perpendicular to the longitudinal axis (X), which will increase the ground clearance (i.e., the distance between the tips of the rotor / stator blades and the ground). In other words, this is beneficial to the technical solution, where:

[0040] - The protrusion extends upward in the direction (A), the direction (A) being vertical or forming a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X), such that 1°≤δ≤30°, preferably, 1°≤δ≤15°, and more preferably

[0041] - The blades of the downstream stator row extend along the angular position at 6 o'clock or on one side or the other side of the angular position at 6 o'clock along the angle (δ).

[0042] For the same expected integration effect, in the following cases, another embodiment is possible:

[0043] - The protrusion again extends upward in the direction (A), the direction (A) being vertical or forming a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X), such that 1°≤δ≤30°, preferably, 1°≤δ≤15°,

[0044] - The blades among the stator blades of the downstream stator row have at least three different azimuthal pitches (Δθ i), where the two with the largest angles are arranged on one side, one between two adjacent blades disposed on both sides of the protrusion and between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock, and the one with the smallest angle is between the blades disposed between the angular positions at 4 o'clock and 8 o'clock.

[0045] This allows reducing the number of blades in the upper part (around 12 o'clock) to allow for the integration of the attachment system, and reducing the number of blades around the azimuthal positions on the sides, i.e., at 3 o'clock and 9 o'clock. Limiting the number of blades on the sides allows modifying the directivity of the sound radiated towards the ground. This is particularly effective in the USF mode with pylons or engine mounts under the wing. However, the drawback of this embodiment is that more blades are concentrated around 6 o'clock, so it has no effect on the noise directed towards the fuselage.

[0046] For the same expected integration effect, another embodiment is possible in the following cases:

[0047] - The protrusion extends upward again in the direction (A), where the direction (A) is vertical or forms a non - zero angle (δ) relative to the vertical line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably, 1° ≤ δ ≤ 15°, and

[0048] - The blades in the stator vanes of the downstream stator row have at least three different azimuthal pitch (Δθ i ), where the two with the largest angles are arranged on one side, one between two adjacent blades disposed on both sides of the protrusion and between the angular positions at 4 o'clock and 8 o'clock, and the one with the smallest angle is between the blades disposed between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock.

[0049] In this case, the azimuthal distribution of stator vanes between the right and left turbine engines can be symmetric with respect to the symmetry plane of the aircraft / airframe. This allows for better load and weight balance on the stator vanes as well as on the aircraft. Additionally, this allows for a reduction in the number of vanes in the upper part (around 12 o'clock) to allow for the integration of the attachment system, and a reduction in the number of vanes in the lower part, i.e., around the azimuthal position at 6 o'clock. Reducing the number of vanes in the lower part allows for modification of the directivity of the sound radiated towards the airframe. This is particularly effective in the USF mode with pylons or engine mounts below the wings. However, a disadvantage of this embodiment is that more vanes are concentrated towards the sides (around 3 o'clock and 9 o'clock), and thus it is not possible to act on the noise generated by the vanes on the sides and directed towards the ground. From an aerodynamic perspective, having more downstream stator vanes upstream of the leading edge of the aircraft wing (e.g., around the azimuthal positions at 2 o'clock and 4 o'clock and / or 8 o'clock and 10 o'clock) makes it possible to filter out the pressure accumulation that would be sensed by the upstream rotor vanes.

[0050] For the same desired integration effect, another embodiment is possible:

[0051] - The protrusion extends upward along a direction (A1 or A2) forming the non-zero angle (δ), and

[0052] - The vanes in the vane series of the downstream stator row are distributed symmetrically or uniformly around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180°, with respect to the angular position at 12 o'clock - 6 o'clock.

[0053] This makes it possible to better balance the weight of the aero - propulsor by reducing the angular sector (Δψ) in which the stator vanes are distributed asymmetrically with respect to the 12 o'clock - 6 o'clock axis.

[0054] Δψ corresponds to the angular sector around the main axis X in which the distribution of the azimuthal pitch between the stators is asymmetric with respect to an axis (e.g., the 12 o'clock - 6 o'clock axis) included in the plane perpendicular to the longitudinal axis X.

[0055] In other words, in the angular sector Δψ, all azimuthal pitches are different, while in the angular sector 360° - Δψ, at least two azimuthal pitches are equal.

[0056] Another related proposal:

[0057] - The protrusion extends along a direction (A2) that is horizontal or forms a non - zero angle (δ) with respect to the horizontal line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and

[0058] - The vanes of the downstream stator row extend along an angular position at 3 o'clock or on one side or the other of the angular position at 3 o'clock or 9 o'clock along an angle δ.

[0059] When the aviation propulsor is mounted at the rear and attached to the fuselage via a strut, this allows for the integration of a protrusion at the strut. Here, the angle δ allows for better integration of the aviation propulsor while reducing the non-uniformity of the flow angle of attack sensed by the rotor blades. For example, when the propulsor is mounted towards the rear of the fuselage, this allows for reducing the effect of the angle of attack / flow angle downstream of the airfoil.

[0060] Three other related proposals that are particularly applicable to the case where the propulsor is laterally attached to the fuselage on one side of the fuselage (which can be done via a strut):

[0061] - The protrusion extends in a direction (A2) that is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably, 1° ≤ δ ≤ 15°, and

[0062] - The vanes in the stator vanes (16) of the downstream stator row have at least three different azimuthal angular spacings (Δθ i ), where the two with the largest angles are located between two adjacent vanes (18a, 18b) arranged one on each side of the protrusion and between the angular positions at 4 o'clock and 8 o'clock and / or between the angular positions at 10 o'clock and 2 o'clock, and the smallest angle is located between the vanes (18) arranged between the angular positions at 2 o'clock and 4 o'clock.

[0063] - Or the vanes in the stator vanes of the downstream stator row have at least three different azimuthal angular spacings (Δθ i ), where the two with the largest angles are located between two adjacent vanes arranged one on each side of the protrusion and between the angular positions at 1:30 and 4:30 o'clock, and the smallest angle is located between the vanes arranged between the angular positions at 10:30 and 1:30 o'clock and / or between the angular positions at 4:30 and 7:30 o'clock.

[0064] - Or the vanes in the vane series in the downstream stator row are symmetrically or evenly distributed around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180° with respect to the angular position at 3 o'clock - 9 o'clock.

[0065] However, it should be noted that the above expression “... or... or” does not prevent at least two of the mentioned alternatives from being combined.

[0066] Δψ corresponds to an angular sector around the main axis X, in which the distribution of the azimuthal pitch between the stator vanes is asymmetric with respect to an axis (e.g., the 3 o'clock - 9 o'clock axis) included in a plane perpendicular to the longitudinal axis X.

[0067] Another proposal concerns a case where there are at least two identical azimuthal pitches (Δθ i ) in the angular sector (360° - Δψ).

[0068] This simplifies the azimuthal distribution of the stator vanes, which can be beneficial for better balancing the distribution of weight and moment around the main axis X, and for better distributing the loads on the stator vanes.

[0069] In this embodiment, it is particularly advantageous that when the attachment structure (pylon or others) is inclined (δ ≠ 0°; when the aircraft is on a horizontal ground, 6 o'clock and 12 o'clock are not on the same vertical line), the stator vane ring can be symmetric around the 12 o'clock - 6 o'clock axis in an angular sector such that 360° - Δψ > 180°. Thus, in this angular sector, there are at least two identical pitches (Δθ i ).

[0070] This simplifies the azimuthal distribution of the stator vanes, which can be beneficial for better balancing the distribution of weight and moment around the main axis X, and for better distributing the loads on the stator vanes. When the azimuthal pitches are the same, the stators to be designed can also be the same. However, when there is a large number of different azimuthal pitches, this means that there are more stator vane families with different geometric characteristics (chord C - Figure 19 ), camber, thickness e - Figure 19 , etc.). For example, increasing the pitch between the vanes will reduce the vane solidity C / E. To maintain a relatively constant solidity, the chord of the vanes should be increased when the pitch is increased. However, it is preferable to limit the number of different pitches to reduce the number of different downstream stator vanes to be designed and manufactured, and thus reduce costs. In addition, the inclination (δ) of the attachment structure here allows for better integration of the aero - propulsor by reducing the non - uniformity of the flow angle of attack sensed by the rotor vanes. For example, when the propulsor is mounted towards the rear of the fuselage, this allows reducing the effect of the flow angle of attack downstream of the airfoil.

[0071] Another proposal concerns a case where all the azimuthal pitches (Δθ i ) in the angular sector complementary to the angular sector where 360° - Δψ > 180° are different.

[0072] This allows for better adaptation to the aerodynamic operation of the downstream stator vanes. For example, this will allow the azimuthal position of the downstream stator vanes to be adjusted so that the flow can easily bypass (without separation, aerodynamic losses, etc.) the attachment structure and / or protrusions, and also reduce the interaction between the wake from the downstream stator vanes and the wing, struts, and / or other aircraft components (slats, flaps, etc.) in the vicinity.

[0073] Another proposal relates to the following situation:

[0074] - One of the vanes of the downstream stator row is located at 6 o'clock, or

[0075] - At least one of the vanes of the downstream stator row is located between 5 o'clock and 7 o'clock.

[0076] This may allow for the integration of certain subsystems in this "low" position, such as an oil recovery circuit, which would benefit from the "gravity" effect.

[0077] Another proposal relates to the following situation: At least one of a pair of two adjacent vanes, on either side of a protrusion, in a series of vanes in the downstream stator row has a fixed pitch and / or has a non-uniform pitch angle (γ), i.e., the pitch angle is different from the pitch angles of the other vanes in the downstream stator row (non-uniform = varying, not the same anywhere).

[0078] In fact, the protrusion may prevent the integration of a variable pitch system in the stator vanes on either side of the protrusion. Additionally, it is possible to envision non-uniform pitches on either side of the protrusion in order to optimize their aerodynamic operation (i.e., allow the flow to better bypass the protrusion without aerodynamic losses, such as those introduced by flow separation, etc.).

[0079] Another proposal relates to the following situation: The longitudinal axis (X) of an aircraft propulsion unit and the longitudinal axis (X1) of an aircraft define an angle β such that the absolute value of the angle ||β|| can vary between 0.5° and 30°, preferably between 2° and 20°, or more preferably between 3° and 10°. The longitudinal axis of the fuselage (or the longitudinal axis of the aircraft, hereinafter axis X1) can be defined as the roll axis of the aircraft, which can correspond to the axis extending from the nose (upstream) to the tail (downstream) of the fuselage, or alternatively, to the axis passing through the most upstream and most downstream positions of the fuselage during cruise flight. Thus, axes X and X1 are not parallel (β≠0°).

[0080] In fact, when installing an aircraft propulsor, the aircraft propulsor generally has a certain inclination angle (β) relative to the aircraft axis. This allows reducing the flow angle of attack sensed by the ducted fan blades during the takeoff / landing phase. This reduces both the noise (reduction of flow separation around the blades associated with high angles of attack) and the 1P force. Therefore, this may affect the non-uniform distribution of the stator blades in the azimuthal direction.

[0081] The "absolute value" aspect of the angle β is important, at least because: in order to limit the effect of the angle of attack during takeoff / landing, the inclination is generally downward in the under-wing installation, but may be upward in the installation towards the rear of the fuselage.

[0082] Another proposal relates to the following situation: there is a plane (P1) perpendicular to the longitudinal axis (X) and intersecting at least one of the blades 18 of the downstream stator 16, where the ratio of the height or thickness K of the protrusion (see the non-limiting example in Figure 20 ) to the height of at least one of the stator blades on one side or the other side of the protrusion is such that 0.02 ≤ K / L2 ≤ 0.9, or preferably, 0.04 ≤ K / L2 ≤ 0.4. This feature allows ensuring the transmission of mechanical forces from the engine to the aircraft and reducing the aerodynamic disturbances associated with the protrusion.

[0083] At least for wake equalization / limitation and noise limitation, it is also proposed that there are at least two stator blade families, preferably at least three stator blade families, in the stator blade row, and each stator blade family includes one or more stator blades having the same geometric characteristics (at least including the chord (C), thickness (e), and height (such as L2 or L21 in the following text)) of the stator blade, where at least one of the geometric characteristics (at least the chord, thickness, height) is different from the same geometric characteristics (chord, thickness, height) of the stator blades in another stator blade family.

[0084] In addition, here again, in order to facilitate a more balanced control of the blade loading and the generated noise, it is proposed that:

[0085] - Each blade of the stator blades in the downstream stator row thus has a height (see L2 or L21 listed in the non-limiting example in Figure 8 ) between the radially inner end and the radially outer end,

[0086] - The corresponding heights (such as L2 and L21) of at least two blades of the downstream stator row are advantageously and preferably different.

[0087] Another proposal relates to the following situation: the protrusion is symmetric about an axis perpendicular to the main axis X of the aircraft propulsor in the plane P1. One objective is to simplify the geometric design of the protrusion.

[0088] Another proposal relates to the following situation: the reference axis of the attachment structure and / or its protrusion is the axis along which the attachment structure or the protrusion extends, and on both sides of the axis, the following situation exists: (360° / V)+2°≤Δθ i ≤(360° / V)+45°, or preferably, (360° / V)+5°≤Δθ i ≤(360° / V)+25°.

[0089] This should ensure that Δθ around the protrusion i is sufficient (or of sufficient size) to mount the attachment structure, but not too large so as to avoid having an aerodynamically harmful azimuthal spacing (not recovered from the vortex flow) between two adjacent vanes on both sides of the protrusion.

[0090] Another proposal relates to the following situation: in the downstream stator vane row, there is a ratio C / E of the chord C to the azimuthal spacing E around the longitudinal axis (X) between two consecutive stator vanes, such that C / E is less than 3 over the entire span, preferably less than 1 at the radially outer ends of two axially consecutive vanes.

[0091] For a possible number of stator vanes (preferably between 8 and 14) that may be selected as a priority, this criterion will be advantageously met. One advantage of a low solidity (C / E ratio) (at the tip / free end of the vane, C / E is preferably less than 1) is that it reduces vane-to-vane interaction. From an aerodynamic perspective, if C / E is large (greater than 3 or 4), then the flow channel or flow area between the vanes decreases. This increases the flow velocity between the vanes, which may lead to the generation of shock waves (between the vanes) and thus to a loss of efficiency at certain operating points. From an acoustic perspective, the lower the solidity (C / E), the more the correlation of the noise sources between the vanes is reduced.

[0092] In addition to the above, an aircraft with a longitudinal aircraft axis (X1) is proposed, the aircraft including an aircraft structure (or frame), and an attachment structure for fixing the aviation propeller is fixed to the aircraft structure (or frame).

[0093] On this aircraft, it can be specifically found that:

[0094] - an even number of the aviation propellers,

[0095] - the aircraft structure includes a fuselage,

[0096] - the fuselage has a symmetry plane (P2), the symmetry plane (P2) passes through the aircraft longitudinal axis (X1) and is parallel to the plane passing through the angular positions of each aviation propeller at 6 o'clock and 12 o'clock,

[0097] - The even number of aircraft propellers includes a pair of upstream annular rows of rotor blades of two of the aircraft propellers that are aligned perpendicular to the symmetry plane (P2),

[0098] - One rotor blade on each side of the pair of upstream annular rows of rotor blades is located on both sides of the fuselage and rotates in opposite directions, and

[0099] - Between the two aircraft propellers, the azimuthal angle distribution of the blades in the downstream annular row of stator blades is symmetric with respect to the symmetry plane (P2).

[0100] The distribution of the stator blades of the row between the propellers on the right and left sides of the fuselage is symmetric with respect to the aircraft / fuselage symmetry plane; this allows for better load balancing on the stator blades and on the aircraft. In fact, when the rotor blades rotate in opposite directions, the rising and falling rotor blades of each aircraft propeller can be positioned symmetrically (or at similar distances) with respect to the aircraft axis.

[0101] As mentioned below, the specified "angle of attack of the aircraft" (angle α hereinafter) can be defined as the angle between the longitudinal axis of the fuselage (axis X1 hereinafter) and the flow direction upstream of the fuselage (or from the forward direction of the aircraft). It should be noted that there can be an angle (β) other than zero degree between the longitudinal axis of the fuselage and the longitudinal axis of the aircraft propeller (sometimes referred to as the "tilt angle" or "bevel angle"). These axes may not be parallel. For example, this can be used to reduce the angle of attack perceived at the rotor during the takeoff phase. The main axis X of the aircraft propeller and the axis X1 of the fuselage / aircraft may not be aligned. This helps to reduce installation effects, such as 1P forces. Description of the Drawings

[0102] By reading the following detailed description and by analyzing the drawings, other features, details and advantages will become apparent, in which all the blades are ductedless, and:

[0103] Figure 1 is a partially schematic cross-sectional view of a turbomachine that can be used in this context, and thus has an upstream rotor and a downstream stator in a "pusher" configuration,

[0104] Figure 2 is a schematic view of a propeller in a configuration that can be a "tractor" configuration, which is in a phase that can be the takeoff phase, and thus has an angle of attack of the aircraft (angle α),

[0105] Figure 3 is a partially schematic cross-sectional view of a turbomachine that can be used in this context in a "tractor" configuration,

[0106] Figure 4Can be represented in a cross-section IV-IV (stator) perpendicular to the longitudinal axis X Figure 3 A turbomachine, an example of a possible arrangement of the blades of an annular row of downstream stators

[0107] Figure 5 Is a schematic perspective view (upstream view) illustrating another arrangement of the blades of the annular row of downstream stators

[0108] Figure 6 Is in the same way as Figure 4 Of the view similar to illustrate Figure 5 Of the arrangement of the schematic front view (upstream view),

[0109] Figure 7 Is a schematic perspective view (upstream view) illustrating another arrangement of the blades of the annular row of downstream stators

[0110] Figure 8 Is in the same way as Figure 4 Of the view similar to illustrate Figure 7 Of the arrangement of the schematic front view (upstream view),

[0111] Figure 9 Schematically shows another technical solution, in which it is mounted between the thruster and the aircraft wing via an engine mount

[0112] Figure 10 Is a schematic front half view (upstream view) of an example of an under-wing installation of a USF type stator blade ring / row, where the installation is carried out via a pylon or strut aligned with the axis passing through 12 o'clock and 6 o'clock

[0113] Figure 11 Is the same half view as Figure 10 But with a pylon or strut inclined at an angle δ with respect to the axis passing through 12 o'clock - 6 o'clock

[0114] Figure 12 Is in the same way as Figure 4 Of the view similar to illustrate the schematic front view (upstream view) of another arrangement of the blades of the annular row of downstream stators

[0115] Figure 13 Is to illustrate the schematic front view (upstream view) of another arrangement of the blades of the annular row of downstream stators (as in Figure 11 ), with a non-zero angle δ (see below);

[0116] Figure 14 Is similar to Figure 4 Of the view to illustrate the schematic front view (upstream view) of another arrangement of the blades of the annular row of downstream stators

[0117] Figure 15 A schematic front view (upstream view) of another arrangement of the blades of the annular row of the downstream stator is illustrated in a view similar to Figure 4 .

[0118] Figure 16 Another technical solution is schematically illustrated, for example, in the manner of the view in Figure 13 , which has two thrusters with stator blades according to the present invention, similar to the above-mentioned thrusters, each thruster being located below the wing.

[0119] Figure 17 The angle or "azimuthal pitch" Δθ between two consecutive stator blades is schematically illustrated i or Δθ j ,

[0120] Figure 18 and Figure 19 the manner in which the stator blade (downstream blade) and the pitch angle of this blade are considered is schematically illustrated. Figure 19 corresponding to Figure 18 section XVIII-XVIII of, this figure and Figure 2 indicate the air flow (lines with multiple arrows) around the thruster.

[0121] Figure 20 A technical solution is schematically illustrated that explains the relationship between the height of the protrusion (K, along the positioned vertical line) and the height (L2) of at least one of the blades.

[0122] Figure 21 The situation with the angle of attack of the aircraft is schematically illustrated in a side view, where the thruster is in a configuration that can be a "tractor" configuration, in a stage that can be the takeoff stage, and thus has a non-zero angle β in this example. Detailed Description

[0123] As an example, an aviation thruster compatible with what is proposed by the present invention can be a turbomotor, such as Figures 1 to 3 the turbomotor in

[0124] Any thruster mentioned herein (e.g., turbomotor 10) includes a hub 12 located upstream (UPST) of the engine housing 13. The annular upstream rotor row 14 of the ducted fan blades 18 is mounted on the hub 12 (around), and the annular downstream stator row 16 of the ducted fan blades 18 is mounted on the engine housing 13 (around). These two rows are spaced apart from each other along the longitudinal axis X of the turbomotor 10.

[0125] The hub 12 and the engine housing 13 can be combined below the term nacelle 40, which is a structure around which the blades 18 of the rotor 14 and the stator 16 are arranged and extended. The nacelle 40 is fixed to the aircraft that the aerospace propeller mentioned here will drive.

[0126] As already understood, orientation defining terms such as, for example, "longitudinal", "radial" or "circumferential" are defined with reference to the longitudinal axis X of the propeller involved, as in the case of the turbomachine 10. The longitudinal direction here corresponds to the forward direction of the propeller. Specifically, the longitudinal direction can coincide with the horizontal direction, that is, perpendicular to the gravitational field. The relative defining terms "upstream" (UPST) and "downstream" (DNST) are defined relative to each other with reference to the gas flow along the longitudinal direction in the propeller. The angular position of each of the blades 18 around the longitudinal axis X is identified with respect to a clock face (for example, as viewed from upstream here), where the angular positions at 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock are positioned in a conventional manner. Thus, the angular position at 12 o'clock is positioned vertically upward with respect to the longitudinal axis X, and the angular position at 6 o'clock is positioned vertically downward with respect to the longitudinal axis X. The angular position at 3 o'clock is positioned horizontally to the right with respect to the longitudinal axis X, and the angular position at 9 o'clock is positioned horizontally to the left with respect to the longitudinal axis X. Therefore, the axis extending radially through the angular positions at 12 o'clock and 6 o'clock is perpendicular to the axis extending radially through the angular positions at 3 o'clock and 9 o'clock. Absolute position defining terms such as, for example, the terms "up", "down", "left", "right", etc., or relative position defining terms such as, for example, the terms "above", "below", "upper", "lower", etc., and orientation defining terms such as, for example, the terms "vertical" and "horizontal" refer to the orientation of the figure here and are considered when the propeller is in the operating state, and the propeller is usually installed on an aircraft placed on the ground. In this state of the turbomachine 10, the axis passing through the angular positions at 12 o'clock and 6 o'clock extends in the direction of the gravitational field, that is, vertically. However, it can be inferred that the rolling motion during the flight of the aircraft equipped with the propeller will cause it to cause the rotation of the vertical and horizontal directions around the longitudinal axis X as considered in the figure. In the same way, the rolling motion during the flight of the aircraft equipped with a propeller on it will cause the axis passing through the angular positions at 12 o'clock and 6 o'clock and the axis passing through the angular positions at 3 o'clock and 9 o'clock to rotate around the longitudinal axis X. The "lateral region" of the turbomachine 10 refers to the region circumferentially near the angular position at 3 o'clock or 9 o'clock. Similarly, the "upper region" and "lower region" of the propeller refer to the region circumferentially near the angular position at 12 o'clock and the region circumferentially near the angular position at 6 o'clock, respectively.

[0127] Thus, the downstream stator row 16 (or stator) is fixed about the longitudinal axis X. In other words, the downstream stator row 16 does not rotate about the longitudinal axis X. This does not exclude the possibility that each blade 18 of the downstream stator row 16 may have a variable pitch.

[0128] If the aircraft propulsion involved is (or includes) a turbomachine, then it will thus be a turbomachine that includes, in order from upstream to downstream inside the nacelle 40 (including below the engine casing 13) and parallel to the longitudinal axis (X), the following:

[0129] - one (or more) compressors 2,

[0130] - at least one combustion chamber 4,

[0131] - one (or more) turbines 6 that drive the compressor, and

[0132] - at least one exhaust nozzle 8.

[0133] Among these turbomachines with an unducted fan, there are known turbomachines of the "unducted single (or stator) fan" (USF) type, as Figures 1 through 3 illustrated, in each of said turbomachines, the upstream rotor row 14 of the unducted blades 18 is mounted so as to rotate about the longitudinal axis X, and the downstream stator row 16 of the unducted blades 18 is fixed. The direction of rotation of the blades 18 of the upstream rotor row 14 (or rotor) is not a determining factor.

[0134] The downstream stator row 16 may be centered on an axis that may or may not coincide with the longitudinal axis X. In the example presented, the downstream stator row 16 is centered on the longitudinal axis X. Such a configuration of the upstream rotor row 14 and the downstream stator row 16 makes it possible to utilize the energy of the swirling airflow from the upstream rotor row 14 by means of the downstream stator row 16. Thus, in particular, the efficiency of the turbomachine 10 is improved compared to a single rotating propeller (such as 14) in the case of a conventional turboprop. The upstream rotor row 14 rotates about the longitudinal axis X by means of the turbine 6, which drives the compressor 2. The turbomachine 10 generally includes a reduction gearbox in order to decouple the rotational speed of the turbine 6 from the rotational speed of the upstream rotor row 14. In addition, one of the advantages of a turbomachine of the USF type compared to a turbomachine of the "counter-rotating open rotor" type is a reduction in the tonal noise emitted by the turbomachine, since the downstream stator row 16 of the unducted blades 18 is fixed.

[0135] As schematically shown in Figure 2 and 3 the propulsion may have a "tractor" configuration (the upstream rotor row 14 and the downstream stator row 16 are located at the upstream end portion of the propulsion), or as inFigure 1 is schematically shown with a "pusher" configuration (the upstream rotor row 14 and the downstream stator row 16 being located at the downstream end portion of the pusher).

[0136] In the tractor configuration, the upstream rotor row 14 and the downstream stator row 16 can surround a section of the compressor 2 of a turbomotor or a reduction gearbox. In the pusher configuration, the upstream rotor row 14 and the downstream stator row 16 can surround a section of the turbine 6 of the turbomotor 10.

[0137] Regardless of the type of pusher (turbomotor, hybrid, etc.), the attachment system 27 will allow the pusher to be fixed to the aircraft 29 equipped with said pusher, and more precisely, to its airfoil (wing) 31, or to its fuselage 33, or to any other suitable part. Generally, this can be done using the following:

[0138] - For the fuselage: struts 35 (as in the Figure 7 example), or

[0139] - For attachment to the wing or airfoil: pylons 37 (as in the Figure 5 、 10 、13、16 examples) or engine mounts 39 (as in the Figure 9 example). The blades 18 of the upstream rotor row 14 and / or the downstream stator row 16 can be variable pitch blades. Thus, it is possible to adjust the pitch of the blades 18 of the turbomotor 10 according to the operating point of the pusher or the flight phase. A pitch change system 38 can be provided, which is partly located in the nacelle 40 (hub 12 and / or casing 13) in order to adjust the angle of attack of the blades for each flight phase. Thus, each blade 18 can be rotated about the corresponding pitch change axis 19. The individual pitch change axes 19 of the blades 18 (possibly for each blade 18) are the following axes:

[0140] - Radially extending and / or longitudinally positioned at the middle part of the corresponding blade, and

[0141] - The pitch angle of the blade can be adjusted about said axis.

[0142] The technical solutions presented here can cover the following cases:

[0143] - The pitch change axis is perpendicular to the longitudinal axis X,

[0144] - The pitch change axis is not perpendicular to the longitudinal axis X, i.e., it is inclined; for example, in the case where the pitch change axis has a longitudinal component and / or a circumferential component.

[0145] Each blade 18 of the upstream rotor row 14 and the downstream stator row 16 extends radially from the hub 12 so as to define a radial dimension between the hub 12 and the radially outer end of the corresponding blade 18. In other words, the radial dimension of the blade 18 is measured between the radially inner end 23 and the radially outer end 25 of the blade. The radially inner end of each blade 18 is located at the hub 12 of the turbine engine 10. Specifically, each blade 18 may be fixed to the hub 12 of the turbine engine 10 at the radially inner end. The radially outer end of each blade 18 is here a free end (i.e., unshrouded). Thus, it is stipulated that the span of the blade 18 is the radial distance between its inner end 23 and outer end 25 (see Figure 9 ).

[0146] Here, L1 may be defined as the maximum height of the rotor blade, and L2 may be defined as the maximum height of the stator blade (regardless of whether all blades have the same height or there is a 360° limit; see for example Figure 8 for the height L21).

[0147] In other words:

[0148] - For the blades in the upstream rotor row, L1 = Re1 - Ri1, and

[0149] - For the blades in the downstream stator row, L2 = Re2 - Ri2.

[0150] Furthermore, each blade 18 of the upstream rotor row 14 and the downstream stator row 16 respectively has a radially inner radius Ri1, Ri2, which are considered to be the radial distances of the radially inner ends of the blades 18 located (i.e., closest) to the hub 12 (rotor row) or the housing 13 (stator row) from the longitudinal axis X. In Figure 3 , the radially inner end 23 is close to the pitch change axis of the corresponding blade. The radially inner end of each blade may alternatively be close to the leading edge at the blade root. The radially outer radius of each blade 18 (e.g., Figure 3 for Re1 or Re2) is considered to be the radial distance of the radially outer end of the blade 18 from the longitudinal axis X, i.e., the maximum radius of the blade.

[0151] As can be understood by observing, for example, Figure 4 , although only a small part of one of the rotor blades is shown, the radially outer ends 25 of the blades 18 of the upstream rotor row 14 and the downstream stator row 16 are respectively inscribed within the circumferential envelopes 20 around the upstream rotor row 14 and the circumferential envelopes 22 around the downstream stator row 16.

[0152] The projection of the circumferential envelope 20 of the downstream stator row 16 onto the section IV-IV (see Figure 1or 3) a circle with a definable radius of Re2 or a diameter of Ds can be defined, which circle can be centered on the longitudinal axis X (Ds = 2 * Re2).

[0153] The diameter D or the circle with a radius of Re1 in the radial section at the circumferential envelope 20 of the upstream rotor row 14 can represent the outer diameter of the considered propeller, which in the example is the turbomachine 10 (see Figure 1 ).

[0154] The radial dimension of each blade 18 of the downstream stator row 16 can be smaller than that of (each) blade 18 of the upstream rotor row 14, so as to limit the influence of the eddy current formed at the radially outer end of the blade 18 of the upstream rotor row 14 on the blade 18 of the downstream stator row 16. Then, when these envelopes are projected onto a common projection plane perpendicular to the longitudinal axis X (for example, section IV-IV here), the circumferential envelope 20 of the upstream rotor row 14 will surround the circumferential envelope 22 of the downstream stator row 16.

[0155] The projection of the circumferential envelope of the downstream stator row 16 onto a common projection plane perpendicular to the longitudinal axis X (for example, section IV-IV in the example) defines a circle whose center can be offset relative to the longitudinal axis X, for example, along the direction of the axis passing through the angular positions at 12 o'clock and 6 o'clock. The radial distance between the center of the circumferential envelope 22 of the downstream stator row 16 having a circular shape and the longitudinal axis X can be between 0.005D and 0.2D.

[0156] The circle / ellipse defined by the circumferential envelope 22 of the downstream stator row 16 can have a radius Re2 (for example, the maximum radius in the case of an elliptical shape), and the radius Re2 is smaller than the radius Re1 of the circumferential envelope 20 of the upstream rotor row 14 (for example, the maximum radius in the case of an elliptical shape).

[0157] Therefore, the non-uniform distribution (in the azimuthal direction) of the blades 18 of the downstream stator 16 is compatible with other noise reduction techniques (such as "360° clipping"). Therefore, in at least one angular sector:

[0158] - The blades 18 of the downstream stator 16 are arranged non-uniformly (in the circumferential direction), and

[0159] - For the blades 18 of the downstream stator 16, each or individually has a maximum radius (Re2) or height smaller than the maximum radius (Re1) or height of the blades 18 of the upstream rotor 14.

[0160] In this case, shorter vanes 18 of stator 16 would be preferred in the lower part (between 4 o'clock and 8 o'clock) and on the side (between 2 o'clock and 4 o'clock or between 7 o'clock and 10 o'clock, towards the outside and / or towards the fuselage) in order to minimize interaction noise during phases with a large angle of attack (landing / takeoff).

[0161] Having fewer vanes in stator 16 than in the upstream rotor 14 can also be used for combined noise reduction, aerodynamic efficiency, less stress on the load on certain vanes of the downstream stator, and weight and size reduction.

[0162] Recommendation: B ≥ V + 1, or preferably, B ≥ V + 2.

[0163] According to the important aspects mentioned above, for the reasons mentioned: integration constraints, or even aerodynamic and / or acoustic reasons, attention is hereby paid to the fact that the vanes of the downstream stator 16 have an uneven azimuthal pitch.

[0164] Depending on the desired compromise for the objective or cross - professional focus area, several embodiments can be envisaged.

[0165] As indicated above, there is an azimuthal pitch (Δθ i ) around the longitudinal axis (X) between two adjacent vanes (e.g., 18a, 18b) of the downstream stator row 16 of the stator vanes, and the azimuthal pitch is defined by the angle between their respective axes 180a, 180b and / or 19. These axes are interchangeable in the presented case and, in particular, can be swapped positions in the drawings.

[0166] These respective axes:

[0167] - When these axes are projected onto a plane perpendicular to the longitudinal axis X and in the case where the two adjacent vanes have variable pitch angles, they are the pitch angle adaptation axes (the above - mentioned axis 19) of the two adjacent vanes,

[0168] - Or in the case where the two adjacent vanes have fixed pitch angles, they are axes that are respectively radial with respect to the longitudinal axis X and / or pass through the radial inner end 23 or the radial outer end 25 (maximum radius Re2, for example, as in Figure 3 ), or pass through the center of gravity of the two adjacent vanes,

[0169] - Or:

[0170] - When one of the two adjacent vanes (e.g., 18a) has a variable pitch angle, for one of the corresponding axes, it is the pitch angle adaptation axis (the above - mentioned axis 19) of the vane,

[0171] - When the blade (e.g., 18b) has a fixed pitch angle, the other of the corresponding axes is radial to the longitudinal axis X and / or passes through the radially inner end 23 of the adjacent blade or through the radially outer end 25 or through the center of gravity.

[0172] In the case where one of the stator blades is fixed (e.g., for integration constraints, e.g., if there is a lack of space below the hub 12 or the housing 13 for integrating a pitch change system or for weight reduction), the main axis of the blade can thus be defined by a line perpendicular to the longitudinal axis X, which passes through the leading edge (LE) at the blade root 23 or through the center of gravity of the blade or at the blade tip (outer end) 25 (maximum radius, Re2). We will return to this case in the so-called "second case" below.

[0173] Hereinafter, and generally in the present disclosure, the expression "blade axis" will correspond indifferently to any one of these three cases.

[0174] In this context, in order to present the desired non-uniform distribution around the longitudinal axis X, at least some of the blades 18 of the downstream stator row 16 are arranged such that there is an azimuthal pitch Δθ between at least two of the adjacent blades (e.g., 18a, 18b) of the downstream stator row 16 i , or such that:

[0175] Δθ i ≠360° / V;

[0176] Δθ i ≥(360° / V)+1° or Δθ i ≤(360° / V)-1°,

[0177] where V defines the number of blades 18 in the downstream stator row 16;

[0178] and / or such that there are at least two azimuthal pitches between the blades 18 of the downstream stator row 16 such that when i≠j and i, j (integers)=1, 2,... and i, j≤V, Δθ i and Δθ j are different.

[0179] Thus, preferably, a difference of at least 1° is required to cause a significant effect associated with the non-uniform azimuthal pitch. Preferably, the difference will be ≥3° or more preferably, ≥5°.

[0180] As an example, Figure 17 schematically shows the angle or "azimuthal pitch" Δθ between two consecutive stator blades i or Δθ j, said two consecutive stator vanes have, for example, vanes 18a, 18b with respective radial axes 180a, 180b. These are two consecutive stator vanes with a smaller angle circumferentially around axis X between axes 180a, 180b.

[0181] Generally speaking, and as can be seen from the non - limiting examples in Figure 3 , each of said azimuthal spacings is defined by the circumferential distance E between two consecutive vanes 18a, 18b, which distance varies with the radial and azimuthal positions of the vanes 18 involved, i.e., E = r*Δθ (or E i = r*Δθ i ). Thus, when these axes are projected onto a plane perpendicular to the longitudinal axis X of the aerospace thruster, these azimuthal spacings can be characterized by said angle Δθ i .

[0182] Each downstream stator vane 18 defines an aerodynamic profile. For this purpose, each downstream stator vane includes a stack of sections 30 along the radial direction. One of the sections 30 is shown in Figure 19 . Each section 30 extends in a respective cross - section perpendicular to the radial extension direction of the corresponding downstream stator vane. Each section 30 includes an upstream leading edge and a downstream trailing edge, and a pressure side line 330 and a suction side line 340 extend between the upstream leading edge and the downstream trailing edge. Each section 30 defines an aerodynamic profile. Each section 30 also includes a chord C defined by a straight - line segment connecting the leading edge to the trailing edge.

[0183] As is conventional (see, for example, Figures 18 - 19 ), the pitch angle γ of each downstream stator vane 18 corresponds to the angle formed between, on the one hand, a first axis A1, which is defined by the intersection of the cross - section of a reference section 30 among the stack of sections 30 of the downstream stator vane and a plane perpendicular to the longitudinal axis X, the longitudinal axis X may include the pitch axis 19 of the downstream stator vane / each downstream stator vane discussed (thus, for all cases set forth herein, the pitch axis 19 may or may not be present) (this is usually the case but not mandatory when the pitch - changing axis is perpendicular to axis X), and, on the other hand, the chord C of the reference section 30 of the downstream stator vane 16. The pitch angle γ is measured on the upstream side of the plane perpendicular to the longitudinal axis X, which longitudinal axis X includes the pitch axis 19 of the downstream stator vane 18. The pitch angle γ is measured positively along a direction oriented from the first axis A1 towards the chord C of the reference section 30, more specifically, positively along a direction coinciding with the direction oriented from the pressure side line 330 to the suction side line 340.

[0184] A reference section 30 of each downstream stator vane 18 may be located on a corresponding downstream stator vane 16 at a radial distance from the longitudinal axis X, the radial distance corresponding to 75% of the outer radial radius of the downstream stator vane.

[0185] As has been noted, one problem addressed by the present disclosure relates to the integrated constraint of the non-uniform azimuthal distribution of the blades of the downstream stator 16 of an aero-propulsor, as generally presented above, and thus specifically even in the presence of said protrusions, in the presence of an attachment structure 27 for attaching the propulsor to an aircraft 29.

[0186] As schematically illustrated by way of example in the figures, this (each) protrusion 270 may be the attachment structure 27 itself for attaching the aero-propulsor to the aircraft, or a protrusion of some type, such as a bulge:

[0187] - on the attachment structure 27 and / or

[0188] - on the nacelle 40; specifically, this may be a protrusion at the interface between the housing 13 and the attachment structure 27, and the protrusion 270 is then partially integrated in said interface.

[0189] Thus, whether extending between two blades 18 of the downstream stator row 16 or axially adjacent to them, when observed in a plane (P1) perpendicular to the longitudinal axis (X), the attachment structure 27 has (for example, see Figure 3 or 5) or defines (for example, see Figure 1 , 2 ) a protrusion 270. For example, the protrusion 270 may be required for a fairlead portion of the variable pitch system 38 of the blade 18 involved or for a lubricant delivery line, or for a fairlead portion of the attachment structure itself.

[0190] The plane P1 is Figure 1 and 3 the section / plane IV-IV in

[0191] - at least (partially) intersects one of the stator vanes circumferentially adjacent to the attachment structure,

[0192] - or alternatively contains at least one (or more) of the blade axes (18a and / or 18b).

[0193] In the "engine mount solution" (using the engine mount 39), the protrusion 270 may be defined in the plane P1, as defined in the following description, at the midpoint between the blade axes at the side of the protrusion, i.e., at the midpoint between the axes 18a and 18b in the plane P1.

[0194] The nacelle 40 (specifically, the housing 13) is fixed by an attachment structure 27.

[0195] Thus, specifically, in the presence of the pylon 37, the engine mount 39 or the strut 35, it would be beneficial to provide an increased azimuthal spacing between two blades of the downstream stator 16 located on either side of the attachment structure 27 and / or the protrusion 270.

[0196] In practice, in any situation where, as in the present disclosure, the selected attachment structure 27 is integrated into the aircraft, when the two adjacent blades (e.g. 18a, 18b) are located one on either side of the attachment structure 27 and / or the protrusion 270, in a plane perpendicular to the longitudinal axis (X), the azimuthal spacing Δθ i (i = 1 to V) will thus be between 1° and 75° greater than the minimum azimuthal spacing Δθ present in the stator blades of the downstream stator row 16, preferably between 5° and 40°, or more preferably between 8° and 20°. i Specifically, this will allow an embodiment to be proposed in which the azimuthal spacing Δθ

[0197] : i

[0198] - for all pitch change axes 19, and / or

[0199] - in the case where the two adjacent blades are at a fixed pitch angle, for all the aforementioned axes (e.g. 18a, 18b) radial to the longitudinal axis X,

[0200] For example, except as Figure 6 and 8 illustrated, outside the angular sectors facing the attachment structure 27 and / or the protrusion 270, is uniform.

[0201] It should be understood that "uniform distribution" has the following meaning: for any azimuthal spacing between two (circumferential) adjacent / consecutive blades involved, Δθi = 360° / V. This angular sector will then preferably be limited to between 20° and 50°. In the case of a uniform distribution, this is the angle between two adjacent blades. This angle will be limited by the number of blades preferably envisaged, for example, V preferably varies between 8 and 16, which corresponds to an angular sector between 22.5° and 45°.

[0202] In Figures 5 to 9 three examples of such a situation are shown.

[0203] Thus, Figure 5 and 6 ​Shows the case where the pylon or strut is integrated at the stator vane ring 16 in the installation under the wing (wing 31). This can be:

[0204] - Figure 5 , the pylon 37,

[0205] - Figure 6 , via the pylon 37, the front view (from upstream) (axial section) of the vane ring 18 of the downstream stator 16 under the aircraft wing.

[0206] In Figure 7 、 8 , this is instead the case where the pylon or strut is integrated at the stator vane ring 16 in the lateral installation on one side of the fuselage 33. This can be:

[0207] - Figure 7 , the strut 35,

[0208] - Figure 8 , via the strut 35, the front view (from upstream) (axial section) of the vane ring 18 of the downstream stator 16 laterally attached to the aircraft fuselage.

[0209] Specifically, in Figure 6 、 7 and 8, the following should also be noted: In addition to the two adjacent blades 18a, 18b (azimuthal pitch Δθ1) located one on each side of the protrusion 270 and / or the attachment structure 27 respectively in the blade series of the downstream stator row 16, all pairs of adjacent blades in the downstream stator row 16 have the same azimuthal pitch Δθ2. In the cases involved, Δθ1 > Δθ2, regardless of whether the attachment structure 27 and / or the protrusion 270 is at or near 12 o'clock (δ = 0° or δ ≠ 0°) or elsewhere, and specifically, laterally located at or near 3 o'clock or 9 o'clock (δ = 0° or δ ≠ 0°).

[0210] In Figure 9 , there is the following case: The engine mount 39 is integrated at the stator vane ring 16 in the lateral installation just upstream of the leading edge 310 of the wing 31 or under the wing ("high wing" configuration); in the example, it is integrated at a level slightly below the wing.

[0211] A specific feature of the integrated engine mount 39 is that it corresponds to a (generally rather) tubular structure placed around the aviation thruster; the protrusion 270 can take the form of one or more rather tubular bosses.

[0212] In a particular embodiment, it is preferred that at least one of the blades of the downstream stator 16 is located at or near 180° (e.g., at 6 o'clock), or between 4 o'clock and 8 o'clock. This may allow for the integration of certain subsystems in this "low" position, such as an oil recovery circuit, which would then benefit from the "gravity" effect.

[0213] Other scenarios may arise in connection with the blades of the downstream stator 16 that are installed at a lower level than the wing 31 (usually below the wing or below the airfoil), and thus in connection with the pair of blades 18 of the upstream rotor 14 and the downstream stator 16 as presented above. Depending on the choice of the installation position of the aviation propulsor on the aircraft, the pylon 37 or the engine mount 39 may be aligned with the 12 o'clock position and / or θ = 0°, as Figure 10 illustrated. In this case, δ = 0°, where δ corresponds to the angular difference between the blade axis (in the example, 18c) passing through 12 o'clock and 6 o'clock and the reference axis of the attachment structure 27 (pylon 37 or engine mount 39) for the installation below the wing 31.

[0214] The reference axis of the attachment structure 27 (pylon 37 in the above example) and / or its protrusion 270 is the axis along which the attachment structure or protrusion extends, such as 18a, 18b, or 19, and on both sides of said axis, there is a situation where: Δθ i ≥ (360° / V) + 1°, and preferably, (360° / V) + 2° ≤ Δθ i ≤ (360° / V) + 45°, and more preferably, (360° / V) + 5° ≤ Δθ i ≤ (360° / V) + 25°.

[0215] In the case where the aviation propulsor is installed via the pylon 37 or the engine mount 39, for the installation below the wing 31, the protrusion 270 and / or the attachment structure 27 extends in the vertical direction (A1), or forms a so-called angle δ with respect to the vertical line and around the longitudinal axis (X), such that:

[0216] δ = 0° (e.g., Figure 10 or 12), or

[0217] δ is non-zero, where 1° ≤ δ ≤ 30°, preferably, 1° ≤ δ ≤ 15° (e.g., Figure 11 or 13).

[0218] Specifically, this embodiment may correspond to an embodiment having a pylon 37 on an aero-turbine engine, which is a turbofan engine and is thus equipped with a fan.

[0219] In the reference direction A1, when the pylon 37 or the engine mount 39 extends upward but is inclined at the angle δ≠0° (1°≤δ≤30°, preferably 1°≤δ≤15°) with respect to the 12 o'clock - 6 o'clock axis, the ground clearance may be increased, where the ground clearance means the distance between the ground and the radially outer end 25 of the blade 18 closest to the ground, which simplifies the integration on the aircraft. For example, this may be of interest when it is desired to integrate an aviation thruster under the wing of an aircraft but without increasing the height of the wing relative to the ground.

[0220] In other cases, the angle δ can be defined relative to the direction (A2) passing through 3 o'clock and 9 o'clock, for example towards the rear of the fuselage (see Figure 7 , 8 or the examples in 15, or any other case where the attachment structure 27 will be oriented accordingly) when the aviation thruster is mounted on the fuselage 33 and in the case where δ = 0° (see also the notes related to δ≠0°).

[0221] In this case, it will be noted that the integration of the pylon / strut at the stator vane ring 16, while taking into account the integration constraints around the pylon or strut.

[0222] However, regardless of the technical solution adopted (reference system along direction A1 or A2 and δ = 0° or δ≠0°), it is useful that:

[0223] - Keep the blades of the downstream stator 16 in an orientation such that, azimuthally, thus around the longitudinal axis (X), symmetrically with respect to the axis A1 or A2, perpendicular to the longitudinal axis (X) and thus passing through the attachment structure 27 and / or the protrusion 270, and even advantageously combining the integration constraints, limiting the possible difference in noise emitted by the stator blades 18 located on both sides of the protrusion 270, better distributing the loads on the stator blades 18 during flight without angle of attack, and / or simplifying the design of the blade row 18 of the downstream stator 16;

[0224] - Keep the spacing around the azimuthal position of the protrusion 270 (and / or thus the attachment structure 27, and thus the pylon 37 or the engine mount 39 or the strut 35, depending on the case) as the maximum azimuthal spacing Δθ between two adjacent blades 18 among all the blades 18 of the downstream stator 16 i .

[0225] In addition, for the reasons explained, the following specific cases (which can be combined when possible, or even associated with the above cases) may also be advantageous.

[0226] An example of which is schematically shown in Figure 12 The first case is:

[0227] - The protrusion 270 (and / or the attachment structure 27) extends upward along a direction A1, which is vertical or forms the angle δ with respect to the vertical line and around the longitudinal axis X, such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15° (for example, in Figure 12 not shown, but can be easily constructed with the angle δ in Figure 13 or the case of the angle δ in 15), and

[0228] - The blades 18 of the downstream stator 16 have at least three different azimuthal spacings (Δθ i ), where the two with the largest angles are located between two adjacent blades (such as 18a, 18b) arranged one on each side of the protrusion 270 (and / or the attachment structure 27) and between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock, and the smallest angle is located between the blades 18 of the downstream stator 16 arranged between the angular positions at 4 o'clock and 8 o'clock.

[0229] This allows reducing the number of blades in the upper part (around 12 o'clock) to allow the integration of the attachment system 27, and reducing the number of blades around the azimuthal positions on the sides, that is, at 3 o'clock and 9 o'clock. Limiting the number of blades on the sides makes it possible to modify the directivity of the sound radiated towards the ground. This is particularly effective in the USF mode with underwing pylons 37 or engine mounts 39. However, the disadvantage of this embodiment is that more blades are concentrated around 6 o'clock, so it has no effect on the noise guiding the fuselage 33.

[0230] From an aerodynamic point of view, having more blades 18 of the downstream stator 16 upstream of the leading edge of the wing 31 (around the azimuthal positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock) allows filtering the pressure accumulation that will be sensed by the blades 18 of the upstream rotor 14.

[0231] The azimuthal spacing between two adjacent blades can decrease in a (strictly) monotonic manner from the azimuthal position at 12 o'clock towards the azimuthal position at 6 o'clock, and the advantage is the expected reduction of aerodynamic interference, specifically, the expected reduction of the interaction between the wake of the stator blade 18 and the thruster support and its protrusion.

[0232] An example of it is in Figure 13 The second case illustrated in

[0233] - The protrusion 270 (and / or the attachment structure 27) extends upward along a direction A1, which is vertical or thus forms the angle δ with respect to the vertical line and around the longitudinal axis X, such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and

[0234] - The blades 18 of the downstream stator 16 have at least three different azimuthal spacings (Δθ i ), where the two with the largest angles are located one on each side between two adjacent blades (e.g., 18a, 18b) disposed on both sides of the protrusion 270 (and / or the attachment structure 27) and between the angular positions at 4 o'clock and 8 o'clock, and the smallest angle is located between the blades 18 of the downstream stator 16 disposed between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock.

[0235] In this case, the azimuthal distribution of the stator blades between the right and left turbofans can be symmetric with respect to the symmetry plane of the aircraft (airplane) / fuselage in the angular sector 360° - Δψ > 180°. This allows for better load and weight balance on the stator blades as well as on the aircraft. Additionally, this allows for a reduction in the number of blades in the upper part (around 12 o'clock) to allow for the integration of the attachment system, and a reduction in the number of blades in the lower part, i.e., around the azimuthal position at 6 o'clock. Limiting the number of blades in the lower part makes it possible to modify the directivity of the sound radiated towards the fuselage 33. This is particularly effective in the USF mode with underwing pylons 37 or engine mounts 39. However, a drawback of this embodiment is that more blades are concentrated towards the sides (around 3 o'clock and 9 o'clock), and thus it is not possible to act on the noise generated by the blades on the sides and directed towards the ground.

[0236] An example thereof is shown schematically in Figure 14 The third case is as follows:

[0237] - The protrusion 270 (and / or the attachment structure 27) extends in the direction A2, which is horizontal or forms an angle (δ) with respect to the horizontal line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15° (the notes are the same as Figure 12 the notes regarding this figure), and

[0238] - The blades 18 of the downstream stator 16 extend along the angular position at 3 o'clock or on one side or the other of the angular positions at 3 o'clock or 9 o'clock along the angle δ (if δ ≠ 0).

[0239] When the aviation propulsor is mounted at the rear and attached to the fuselage by the strut 35, this allows for the integration of the protrusion at the strut 35. Here, the angle δ allows for better integration of the aviation propulsor while reducing the non-uniformity of the flow angle of attack perceived by the rotor blades. For example, when the propulsor is mounted at the rear of the fuselage, this allows for a reduction in the effect of the angle of attack / flow angle downstream of the airfoil.

[0240] An example thereof is also illustrated in Figure 14 The fourth case is as follows:

[0241] - The protrusion 270 (and / or the attachment structure 27) extends along a direction A2 which is horizontal or forms an angle (δ) with respect to the horizontal line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15° (the same note as Figure 12 the note regarding this figure illustration), and

[0242] - The blades 18 of the downstream stator 16 (considered all together) have at least three different azimuthal pitchings (Δθ i ), where the two with the largest angles are located between two adjacent blades (such as 18a, 18b) arranged one on each side of the protrusion 270 (and / or the attachment structure 27) and between the angular positions at 4 o'clock and 8 o'clock and / or between 10 o'clock and 2 o'clock, and the smallest angle is located between the blades 18 arranged between the angular positions at 2 o'clock and 4 o'clock of the downstream stator 16.

[0243] This makes it possible to modify the directivity of the sound emitted by the blades 18 of the downstream stator 16 so as to limit the noise radiated towards the fuselage 33 when the aviation propeller is mounted towards the rear of the fuselage, for example via the strut 35.

[0244] An example thereof is Figure 15 In the fifth case illustrated in

[0245] - The protrusion 270 (and / or the attachment structure 27) extends along a direction A2 which is horizontal or forms an angle (δ) with respect to the horizontal line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and

[0246] - The blades 18 of the downstream stator 16 (considered all together) have at least three different azimuthal pitchings (Δθ i ), where the two with the largest angles are located between two adjacent blades (such as 18a, 18b) arranged one on each side of the protrusion 270 (and / or the attachment structure 27) and between the angular positions at 1:30 and 4:30 o'clock, and the smallest angle is located between the blades 18 arranged between the angular positions at 10:30 and 1:30 o'clock and / or between 4:30 and 7:30 o'clock.

[0247] This makes it possible to modify the directivity of the sound emitted by the blades 18 of the downstream stator 16 so as to limit the noise radiated towards the ground (such as around the airport) when the aviation propeller is mounted towards the rear of the fuselage, for example via the strut 35.

[0248] An example thereof is Figure 15 In the sixth case illustrated in

[0249] - The projection 270 (and / or the attachment structure 27) extends along a direction A2 which is horizontal or forms an angle (δ) with respect to the horizontal line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and

[0250] - The blades 18 of the downstream stator 16 (considered all together) are symmetrically or uniformly distributed around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180° with respect to the angular position at 3 o'clock - 9 o'clock.

[0251] In certain embodiments (such as Figure 15 the embodiments in), all the azimuthal spacings Δθ included in Δψ i are different.

[0252] An example thereof is described in Figure 13 and a seventh case which is to some extent complementary to the previous case is:

[0253] - The projection 270 (and / or the attachment structure 27) extends upward along a direction A1 which is vertical or thus forms an angle δ with respect to the vertical line and around the longitudinal axis X such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and

[0254] - The blades 18 of the downstream stator 16 (considered all together) are symmetrically or uniformly distributed around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180° with respect to the angular position at 12 o'clock - 6 o'clock.

[0255] When the azimuthal spacings are the same, the stators to be designed can be the same. However, when there is a large number of different azimuthal spacings, this indicates the existence of more stator blade families with different geometric characteristics (chord C, camber, thickness e etc.). For example, increasing the spacing E between the blades will reduce the blade solidity C / E. To keep the solidity relatively constant, the chord of the blade should increase as the spacing increases. Therefore, it is necessary to try to limit the number of different spacings to reduce the number of different downstream stator blades to be designed and manufactured, thereby reducing costs.

[0256] Still on this topic, in a specific sub - case where, with reference to direction A1, the angle δ is such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15° (such as in Figure 13 ), it may be useful to provide that there are at least two identical azimuthal spacings Δθ in this angular sector 360° - Δψ > 180° i : In the example of Figure 13 , there are two Δθ1, two Δθ2 and two Δθ3 in this angular sector.

[0257] And, assuming that all said azimuthal spacings Δθ i are different in said complementary angular sectors Δψ, such as again here as in Figure 13 , where in the angular sector Δψ, Δθ4≠Δθ5≠Δθ6≠Δθ7, which will allow for better adaptation to the aerodynamic operation of the blades 18 of the downstream stator 16. For example, this will allow adjustment of the azimuthal position of the blades 18 of the downstream stator 16 such that the flow can better bypass the attachment structure 27 and / or the protrusion 270 (and reduce its aerodynamic losses), as well as reduce the interaction of the wake of the blades 18 of the downstream stator 16 with the wing 31, the strut 35, and / or other nearby elements of the aircraft (slats, flaps, etc.).

[0258] An example thereof can again be illustrated in Figure 13 The eighth case illustrated in is as follows:

[0259] - The protrusion 270 (and / or the attachment structure 27) extends upward along the direction A1, which is vertical or thus forms an angle δ with respect to the vertical line and around the longitudinal axis X such that 1°≤δ≤30°, preferably 1°≤δ≤15°, and

[0260] - All the blades of the downstream stator 16 have said non-uniform azimuthal spacing Δθ in the angular sector Δψ i .

[0261] For example, this will allow adjustment of the azimuthal position of the blades 18 of the downstream stator 16 such that the flow can better bypass the attachment structure 27 and / or the protrusion 270, as well as reduce the interaction of the wake of the blades 18 of the downstream stator 16 with the wing 31, the strut 35, or other nearby elements of the aircraft (slats, flaps, etc.).

[0262] The ninth case, an example of which is illustrated in Figure 16 (but the azimuthal distribution of the blades of the downstream stator 16 can be the same as one of the cases presented above with reference to Figure 5 , 6 , 10 to 13 as appropriate), where:

[0263] - It relates to an aircraft 29 including an even number of aviation thrusters 10 (thus, having ducted fans with an upstream rotor 14 and also ducted fans for the downstream stator 16),

[0264] - The structure 290 (its frame) of the aircraft includes a fuselage 33,

[0265] - The fuselage 33 has a plane of symmetry (P2) that passes through the longitudinal axis (X1) of the aircraft and is parallel to the plane passing through the angular positions of each aviation thruster 10 at 6 o'clock and 12 o'clock,

[0266] - As in the case of, for example, Figures 1 to 3 the even number of aviation thrusters 10 includes a pair of upstream annular rows of rotor blades 14 of two of the aviation thrusters 10 aligned perpendicular to the symmetry plane (P2),

[0267] - One blade on each side of the pair of upstream annular rows of blades of the upstream rotor 14 is located on each side of the fuselage 33 and the rotor blades rotate in opposite directions, and

[0268] - Between the two aviation thrusters 10, the azimuthal distribution of the blades in the downstream annular row of the downstream stator 16 is symmetric with respect to the symmetry plane (P2).

[0269] The blades 18 of the upstream rotor 14 on the right and left sides of the fuselage 33 rotate in opposite directions.

[0270] The distribution of the stator blades of the row between the thrusters on the right and left sides of the fuselage is symmetric with respect to the aircraft / fuselage symmetry plane P2; and this allows for better balancing of the loads on the stator blades and on the aircraft. In fact, when the rotor blades rotate in opposite directions, the ascending and descending rotor blades of each aviation thruster can be symmetrically positioned (or at similar distances) with respect to the aircraft plane P2.

[0271] Independent of the nacelle, meaning that when the thruster includes a turbomachine 10 (gas turbine), it includes:

[0272] - A hub 12 provided with an upstream rotor row 14, and

[0273] - An engine casing 13 provided with a downstream stator row 16 located downstream (DNST) of the upstream rotor row 14,

[0274] The air inlet (such as 41) that brings air to the compressor will advantageously be located:

[0275] - Downstream of the upstream rotor row 14 of the rotor blades, and

[0276] - Upstream of the downstream stator row 16 of the stator blades,

[0277] In other words, longitudinally along the thruster, between the rotor blades and the stator blades.

[0278] It should be understood that such a turbomachine may then sequentially include, from upstream to downstream along the longitudinal axis (X):

[0279] - At least one compressor 2,

[0280] - At least one combustion chamber 6,

[0281] - At least one turbine 4 that drives the compressor, and

[0282] - the air inlet 41.

[0283] This has the following result: the radial dimension of the blades 18 of the downstream annular row 16 can even be further reduced, so that the vortices formed at the tips of the blades 18 of the upstream annular row 14 escape, which reduces the efficiency of the turbomachine 10.

[0284] Another case is discussed below, in which, as in the example of Figure 20 there is a plane (P1) perpendicular to the longitudinal axis (X) and intersecting at least one of the blades 18 of the downstream stator 16, where the ratio of the height K (along the vertical line of its position) of the protrusion 270 to the height of at least one of the stator blades (such as 18a, 18b) on one side or the other side of the protrusion 270 is such that 0.02 ≤ K / L2 ≤ 0.9, or preferably, 0.04 ≤ K / L2 ≤ 0.4.

[0285] This allows the size of the protrusion in the plane P1 to be characterized relative to the height of the adjacent stator blades.

[0286] In the case considered, K corresponds to the distance between Ri2 (as defined above) measured in the plane P1, the radial inner radius of the stator blade involved (or the radius of the hub / housing), and the outer radial end of the protrusion 270.

[0287] In fact:

[0288] - if the protrusion 270 is too long / extends too far upwards, then this adversely affects the aerodynamic performance (increased drag, aerodynamic losses, etc.) and the weight of the propulsion system, and

[0289] - if the protrusion 270 is too small, then there is no need to provide uneven spacing.

[0290] Another case is discussed below, in which, as in the example of Figure 21 the longitudinal axis (X) of the aeronautical pusher and the longitudinal axis (X1) of the aircraft define an angle β such that the absolute value of the angle ||β|| can vary between 0.5° and 30°, preferably between 2° and 20°, or more preferably between 3° and 10°. The longitudinal axis of the fuselage (or the longitudinal axis of the aircraft, hereinafter axis X1) can be defined as the roll axis of the aircraft, which can correspond to the axis extending from the nose (upstream) to the tail (downstream) of the fuselage, or alternatively, to the axis passing through the most upstream and most downstream positions of the fuselage during cruise flight. Thus, the axes X and X1 may not be parallel (β ≠ 0°).

[0291] In fact, when installing an aviation propeller, the aviation propeller typically has a certain inclination angle (β) relative to the aircraft axis. This allows reducing the flow angle of attack sensed by the ductedless blades during the takeoff / landing phase. This reduces both the noise (reduction of flow separation around the blades associated with high angles of attack) and the 1P force. Therefore, this may affect the non-uniform distribution of the blades 18 of the stator row 16 in the azimuthal direction.

Claims

1. Propulsion assembly for an aircraft: - The assembly includes an aircraft propulsion unit (10) having a longitudinal axis (X) and including a housing (13), and a ducted fan rotor blade of an upstream annular row and a ducted fan stator blade of a downstream stator row extending around the housing (13), which are spaced apart from each other along the longitudinal axis (X). An azimuthal pitch (Δθ i ) is defined between two adjacent blades (18a, 18b) of the stator blades (16) of the downstream stator row by an angle between corresponding axes (180a, 180b) around the longitudinal axis (X): - When these axes are projected onto a plane perpendicular to the longitudinal axis (X), and in the case where the two adjacent blades have variable pitch angles, these corresponding axes are the pitch angle adaptation axes of the two adjacent blades, - Or in the case where the two adjacent blades have fixed pitch angles, these corresponding axes are axes that are respectively radial to the longitudinal axis (X) and pass through the radially inner ends (20) or the radially outer ends (21) of the two adjacent blades, - Or, when one of the two adjacent blades has a variable pitch angle, for one of the corresponding axes, it is the pitch angle adaptation axis of the blade, and when the blade has a fixed pitch angle, the other of the corresponding axes is radial to the longitudinal axis (X) and passes through the radially inner end (20) or through the radially outer end (21) or through the center of gravity, - The assembly further includes an attachment structure (27) for fixing the aviation thruster (10) to the aircraft, the attachment structure (27) being fixed to the housing (13), and when observed in a plane (P1) perpendicular to the longitudinal axis (X) and at least (partially) intersecting one of the blades (18) of the downstream stator row (16), the attachment structure (27) has or defines a protrusion (270), the protrusion (270) extending between or being axially adjacent to two of the stator blades (18) of the downstream stator row, and - Around the longitudinal axis (X), the angular position at 12 o'clock is defined as being vertically upward relative to the longitudinal axis (X), and the angular position at 6 o'clock is defined as being vertically downward relative to the longitudinal axis (X), The assembly is characterized in that when the two adjacent blades (18a, 18b) are located one on each side of the attachment structure (27) and / or the protrusion (270), in a plane perpendicular to the longitudinal axis (X), the azimuthal angular spacing ratio between the two adjacent blades (18a, 18b) is greater than the minimum azimuthal angular spacing existing between the stator blades (16) of the downstream stator row by between 1° and 75°, preferably between 5° and 40°, or more preferably between 8° and 20°, The assembly includes at least three different azimuthal angular spacings.

2. The propulsion assembly according to claim 1, characterized in that, The azimuthal angular spacing between two adjacent blades (18a, 18b) that are respectively located one on each side of the protrusion (270) and / or the attachment structure (27) in the blade series of the downstream stator row (16) is greater than any other azimuthal angular spacing between any other pair of adjacent blades of the downstream stator row (16).

3. The propulsion assembly according to any one of the preceding claims, characterized in that, All around the longitudinal axis (X), except for the pairs of two adjacent blades (18a, 18b) that are respectively located one on each side of the protrusion (270) and / or the attachment structure (27) in the blade series of the downstream stator row (16), all pairs of adjacent blades of the downstream stator row (16) have the same azimuthal angular spacing.

4. The propulsion assembly according to any one of the preceding claims, characterized in that, At least one of a pair of two adjacent vanes (18a, 18b) that are respectively located on both sides of the protrusion (270), one on each side in a series of vanes of the downstream stator row (16), has a fixed pitch and / or has a non-uniform pitch angle (γ).

5. The propulsion assembly according to any one of the preceding claims, characterized in that, The vanes of the downstream stator row (16) are positioned azimuthally, and thus around the longitudinal axis (X), in a manner symmetric with respect to the axes (A1, A2) that are perpendicular to the longitudinal axis (X) and pass through the attachment structure (27) or the protrusion (270).

6. The propulsion assembly according to any one of the preceding claims, characterized in that, The radially outer end of each vane (18) of the rotor vanes of the upstream rotor row (14) is inscribed in a first circle (20), and the radially outer end (25) of each vane (18) of the stator vanes of the downstream stator row (16) is inscribed in a second circle (22) whose radius (Re2) is smaller than the radius (Re1) of the first circle (20).

7. The propulsion assembly according to any one of the preceding claims, characterized in that: - the protrusion (270) extends upward in a direction (A1) that is vertical or forms a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - the vanes of the downstream stator row (16) extend along the angular position at 6 o'clock or on one side or the other of the angular position at 6 o'clock along an angle (δ).

8. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - the protrusion (270) extends upward in a direction (A1) that is vertical or forms a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (18) in the stator blades of the downstream stator row (16) have at least three different azimuthal pitch angles (Δθ i ), where the two with the largest angles are located one on each side between two adjacent blades (18a, 18b) disposed on both sides of the protrusion (270) and / or the attachment structure (27), and between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock, and the smallest angle is located between the blades (18) disposed between the angular positions at 4 o'clock and 8 o'clock.

9. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - the protrusion (270) extends upward in a direction (A1) that is vertical or forms a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 15°, - The blades (18) in the stator vanes of the downstream stator row (16) have at least three different azimuthal pitch angles (Δθ i ), and - the azimuthal pitch between two adjacent vanes decreases in a (strictly) monotonic manner from the azimuthal position at 12 o'clock towards the azimuthal position at 6 o'clock.

10. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - the protrusion (270) extends upward in a direction (A) that is vertical or forms a non-zero angle (δ) with respect to the vertical line and around the longitudinal axis (X) such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (18) in the stator blades of the downstream stator row (16) have at least three different azimuthal pitch angles (Δθ i ), where the two with the largest angles are located one on each side between two adjacent blades (18a, 18b) arranged on both sides of the protrusion (270) and / or the attachment structure (27) and between the angular positions at 4 o'clock and 8 o'clock, and the smallest angle is located between the blades (18) arranged between the angular positions at 2 o'clock and 4 o'clock and / or at 8 o'clock and 10 o'clock.

11. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - The protrusion (270) extends in a direction (A2) which is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades of the downstream stator row (16) extend at an angle (δ) on one side or the other of the angular position at 3 o'clock or at the angular position at 3 o'clock or 9 o'clock.

12. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - The protrusion (270) extends in a direction (A2) which is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (18) in the stator vanes of the downstream stator row (16) have at least three different azimuthal spacings (Δθ i ), where the two with the largest angles are located one on each side between two adjacent blades (18a, 18b) arranged on both sides of the protrusion (270) and / or the attachment structure (27), and between the angular positions at 4 o'clock and 8 o'clock and / or at 10 o'clock and 2 o'clock, and the one with the smallest angle is located between the blades (18) arranged between the angular positions at 2 o'clock and 4 o'clock.

13. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - The protrusion (270) extends in a direction (A) which is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (18) in the stator vanes of the downstream stator row (16) have at least three different azimuthal pitch angles (Δθ i ), where the two with the largest angles are located between two adjacent blades (18a, 18b) arranged one on each side of the protrusion (270) and / or on both sides of the attachment structure (27), and between the angular positions at 1:30 and 4:30 o'clock, and the smallest angle is located between the blades (18) arranged between the angular positions at 10:30 and 1:30 o'clock and / or at 4:30 and 7:30 o'clock.

14. The propulsion assembly according to any one of claims 1 to 6, characterized in that: - The protrusion (270) extends in a direction (A) which is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (18) in the stator vanes of the downstream stator row (16) have at least three different azimuthal pitch angles (Δθ i ), where the two with the largest angles are located one on each side between two adjacent blades (18a, 18b) disposed on both sides of the protrusion (270) and / or the attachment structure (27), and between the angular positions at 1:30 and 4:30 o'clock, and the smallest angle is located between the blades (18) disposed between the angular positions at 10:30 and 1:30 o'clock and / or at 4:30 and 7:30 o'clock.

15. The propulsion assembly according to any one of claims 1 to 6, alone or in combination with any one of claims 12 or 14, characterized in that: - The protrusion (270) extends in a direction (A2) which is horizontal or forms a non-zero angle (δ) relative to the horizontal line and around the longitudinal axis (X), such that 1° ≤ δ ≤ 30°, preferably 1° ≤ δ ≤ 15°, and - The blades (16a, 16b) in the blade series of the downstream stator row (16) are symmetrically or evenly distributed around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180° with respect to the angular position at 3 o'clock - 9 o'clock.

16. The propulsion assembly according to any one of claims 1 to 6, alone or in combination with any one of claims 12 or 14, characterized in that: - The protrusion (270) extends upward in a direction (A1) which is vertical or forms a non-zero angle (δ) relative to the vertical line and around the longitudinal axis (X), and - The blades (18a, 18b) in the blade series of the downstream stator row (16) are symmetrically or evenly distributed around the longitudinal axis (X) in an angular sector such that 360° - Δψ > 180° with respect to the angular position at 12 o'clock - 6 o'clock.

17. The propulsion assembly according to claim 15 or 16, characterized in that, In the angular sector 360° - Δψ > 180°, there are at least two identical azimuthal spacings (Δθ i ).

18. The propulsion assembly according to claim 15, 16 or 17, characterized in that, All of said azimuthal spacings (Δθ i ) are adjacent and different in the angular sector Δψ < 180°.

19. The propulsion assembly according to any one of the preceding claims, characterized in that: - One of the stator blades of the downstream stator row (16) is located at 6 o'clock, or -At least one of the stator vanes of the downstream stator row (16) is located between 5 o'clock and 7 o'clock.

20. The propulsion assembly according to any one of the preceding claims, characterized in that The longitudinal axis (X) of the aviation thruster and the longitudinal axis (X1) of the aircraft define an angle β such that the angle (absolute value) (||β||) between the longitudinal axis (X) of the aviation thruster and the longitudinal axis (X1) of the aircraft varies between 0.5° and 30°, preferably between 2° and 20°, or more preferably between 3° and 10°.

21. The propulsion assembly according to any one of the preceding claims, characterized in that, There is a plane (P1) perpendicular to the longitudinal axis (X) and intersecting at least one of the vanes (18) of the downstream stator (16), where the ratio of the height (K) of the protrusion (270) to the height of at least one of the stator vanes (such as 18a, 18b) on one side or the other side of the protrusion 270 is such that 0.02 ≤ K / L2 ≤ 0.9, or preferably, 0.04 ≤ K / L2 ≤ 0.

4.

22. The propulsion assembly according to any one of the preceding claims, characterized in that, The protrusion (270) is symmetric about an axis perpendicular to the main axis X of the aviation thruster in the plane P1.

23. The propulsion assembly according to any one of the preceding claims, characterized in that, The reference axis of the attachment structure (27) and / or its protrusion (270) is the axis along which the attachment structure or the protrusion extends, and on both sides of the axis, the following condition exists: (360° / V) + 2° ≤ Δθ i ≤ (360° / V) + 45°, or preferably, (360° / V) + 5° ≤ Δθ i ≤ (360° / V) + 25°.

24. The propulsion assembly according to any one of the preceding claims, characterized in that, In the stator vanes of the downstream stator row (16), there is a ratio C / E of the chord C to the azimuthal pitch E around the longitudinal axis (X) between two consecutive stator vanes (16), such that C / E is less than 3 over the entire span, preferably less than 1 at the radially outer ends (25) of two axially consecutive vanes.

25. The propulsion assembly according to any one of the preceding claims, characterized in that, The number B of the vanes in the rotor row (14) of the upstream rotor is greater than the number V of the vanes (18) in the stator row (16) of the downstream stator, and preferably, B ≥ V + 2.

26. An aircraft having a longitudinal aircraft axis (X1), the aircraft comprising a structure (290), and an attachment structure (27) fixed to the structure (290), the attachment structure being for fixing the aviation thruster (10) of the propulsion assembly according to any one of the preceding claims.

27. The aircraft according to claim 26, comprising an even number of said aviation thrusters, characterized in that: The structure (290) of the aircraft comprises a fuselage (33), The fuselage (33) has a symmetry plane (P2) that passes through the longitudinal axis (X1) of the aircraft and is parallel to the plane passing through the angular positions of each aviation thruster at 6 o'clock and 12 o'clock, The even number of aviation thrusters includes a pair of upstream annular rows (14) of rotor vanes of two of the aviation thrusters (10) aligned perpendicular to the symmetry plane (P2), The rotor vanes of the pair of upstream annular rows (14) located one on each side of the fuselage rotate in opposite directions, and Between the two aviation thrusters (10), the azimuthal distribution of the vanes (18a, 18b) of the downstream annular row (16) of stator vanes is symmetric with respect to the symmetry plane (P2).

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