Unducted aviation propulsion unit for aircraft

Abstract

The invention relates to a propulsion unit comprising: a housing (102); a hub; -a thruster propeller; and-a fixed rectifier comprising at least one stator blade (114) having a variable pitch about a pitch axis (Y '), each variable pitch stator blade (114) having a pitch angle defined as an angle between any plane perpendicular to the main axis (X) and a chord line (706) connecting a leading edge of the stator blade (114) to a trailing edge of the stator blade (114), the chord line (706) is taken at 75% of the outer radius of the stator blade (114) relative to the main axis (X). The pitch angle is within the interval of [70 degrees; the leading edge of the at least one stator blade (114) has a dihedral angle (D 'BA') at 95% of the outer radius with an absolute value greater than 1 DEG, preferably greater than 3 DEG, still more preferably greater than 10 DEG.

Description

Technical Field

[0001] The present invention relates to a ductless aviation propulsion unit for an aircraft (e.g., a turbine, a turbojet engine, or a turboshaft engine), and an aircraft including such an aviation propulsion unit. Background Technology

[0002] A ductless aero propulsion unit for aircraft is known in the prior art, comprising: -shell; - Hub, which is pivotally mounted relative to the outer shell about a main axis extending in the upstream-downstream direction of the aircraft; - A propeller mounted on a hub so as to be pivotable relative to the outer casing; and - A fixed rectifier mounted on a housing downstream of the thruster propeller along the main axis. The fixed rectifier extends about the main axis and includes at least one stator blade with a variable pitch about the pitch axis. Each stator blade with a variable pitch has a pitch angle defined as the angle between any plane perpendicular to the main axis on one hand and a chord connecting the leading edge of the stator blade to the trailing edge of the stator blade on the other hand.

[0003] Propellers typically have rotor blades with variable pitch. Variable pitch systems are known in English as fan pitch actuation systems (FPAS) and / or pitch change mechanisms (PCMs). To achieve a target thrust, there may be various combinations of propeller speeds and rotor and stator blade pitches.

[0004] One of the challenges of this type of aircraft propulsion unit is certifying the noise level during takeoff and landing operations. The noise level emitted by aircraft is subject to increasingly stringent international regulations designed to limit the acoustic coverage area around airports. Currently, Chapter 14 of Annex 16 to Volume 1 of the OACI (Organisation de l'Aviation Civile Internationale, International Civil Aviation Organization) sets out the effective regulations, which provide the maximum noise level in the EPNL (Effective Perceived Noise Level) based on the flight phase and aircraft weight.

[0005] The main noise sources of a ductless propulsion unit are as follows.

[0006] The primary source of noise is the interaction noise between the eddies generated at the tips of the rotor blades and the wake of the upstream propeller, which in turn interacts with the leading edge of the downstream rectifier. This noise source contributes to the increase in broadband noise because the turbulence rate in the wake is typically very high at the tips of the rotor blades, and also contributes to the increase in tonal noise, which is related to the periodic nature of the eddies as the rotor blades rotate.

[0007] The second noise source is the inherent noise of the rotor and stator blades. This inherent noise is related to the fixed load on the rotor blades (a source of tone noise) and the development of the boundary layer on the rotor and stator blades. In this way, a broadband noise source is generated when the turbulent boundary layer passes over the trailing edge of the rotor and stator blades. Increasing the chords of the rotor and / or stator blades in a ductless aero-propulsion unit increases the surface area on which the boundary layer develops, thus increasing broadband noise.

[0008] The purpose of this invention is to improve the acoustic performance of the rectifier downstream of the propeller without reducing aerodynamic performance, while adhering to certain mechanical constraints.

[0009] In addition, patent applications US 2017 0284304 A1 and FR 3 124 832 A1, as well as the article “Cruise Noise of an Advanced Propeller with Vortex Recovery Blades” published by Dittmar et al. in 2012, describe ductless aero-propulsion units for aircraft. Summary of the Invention

[0010] Therefore, a ductless aero-propulsion unit for aircraft is proposed, comprising: -shell; - Hub, which is pivotally mounted relative to the outer shell about a main axis extending in the upstream-downstream direction of the aircraft; - A propeller, the propeller being mounted on the hub so as to be pivotable relative to the housing; and - A fixed rectifier mounted on the housing downstream of the propeller along the main axis, the fixed rectifier extending about the main axis and including at least one stator blade with a variable pitch about the pitch axis, each stator blade having a pitch angle defined as the angle between any plane perpendicular to the main axis on one hand and a chord connecting the leading edge of the stator blade to the trailing edge of the stator blade on the other hand. The characteristic feature is that the chord is obtained at 75% of the outer radius of the stator blade relative to the main axis, wherein, for at least one value of the pitch angle in the interval [70°; 90°], the leading edge of at least one stator blade has a dihedral angle at 95% of the outer radius with an absolute value greater than 1°, preferably greater than 3°, and even more preferably greater than 10°.

[0011] The present invention may also include one or more of the following optional features in any technically possible combination.

[0012] Optionally, for at least one value of the pitch angle within the range [70°; 90°], the dihedral angle (D') of the leading edge of the stator blade at 95% of the outer radius. BA’ The absolute value of the angle is at least 1° greater than the absolute value of the dihedral angle at 50% of the outer radius, preferably at least 3° greater, or even more preferably at least 10° greater.

[0013] Optionally, for at least one value of the pitch angle within the interval [70°; 90°], the absolute value of the dihedral angle on the leading edge of the stator blade is strictly monotonic with respect to radial positions greater than 90% of the outer radius.

[0014] Alternatively, the projection of the leading edge of the stator blade onto a plane perpendicular to the main axis has a so-called lateral deviation along a so-called lateral direction, which is perpendicular to the radial component of the main axis and the pitch axis. For at least one value of the pitch angle in the interval [70°; 90°], the lateral deviation of the leading edge of the stator blade is greater than 1% and less than 10% of the outer radius of the stator blade.

[0015] Alternatively, for at least one value of the pitch angle within the interval [70°; 90°], the projection of the leading edge of the stator blade onto a plane perpendicular to the main axis has at least one local maximum and / or minimum value.

[0016] Alternatively, for at least one value of the pitch angle within the range [70°; 90°], the projection of the leading edge of the stator blade onto a plane perpendicular to the main axis has at least one inflection point.

[0017] Alternatively, the propeller includes at least one rotor blade having a variable pitch about a pitch axis that passes through the main axis and has a non-zero radial component relative to the main axis. Each variable-pitch rotor blade has a pitch angle defined as the angle between an arbitrary plane perpendicular to the main axis on one hand and a chord connecting the leading edge of the rotor blade to the trailing edge of the rotor blade on the other hand. This chord is intercepted in a plane perpendicular to the radial component of the pitch axis and passes through the rotor blade at 75% of the outer radius of the rotor blade relative to the main axis.

[0018] Alternatively, the trailing edge of the rotor blade and the leading edge of the stator blade have a dihedral angle, such that for at least one value of the pitch angle of the rotor blade in the interval [50°; 80°] and for at least one value of the pitch angle of the stator blade in the interval [70°; 90°], the absolute value of the dihedral angle on the trailing edge of the rotor blade is greater than the absolute value of the dihedral angle on the leading edge of the stator blade at 95% of the outer radius of the stator blade.

[0019] Alternatively, the trailing edge of the rotor blade and the leading edge of the stator blade have a dihedral angle such that, for at least one value of the pitch angle of the rotor blade in the interval [50°; 80°] and for at least one value of the pitch angle of the stator blade in the interval [70°; 90°], the absolute value of the dihedral angle on the trailing edge of the rotor blade is at least 10° greater than the absolute value of the dihedral angle on the leading edge of the stator blade at 75% of the outer radius of the stator blade.

[0020] Alternatively, for at least one value of the rotor blade pitch angle within the interval [50°; 80°] and for at least one value of the stator blade pitch angle within the interval [70°; 90°], the trailing edge of the rotor blade and the leading edge of the stator blade have dihedral angles (Di) with opposite signs at 95% of the outer radius of the stator blade. BF D' BA' ).

[0021] Alternatively, at any height from the main axis, for at least one value of the rotor blade pitch angle in the interval [50°; 80°] and for at least one value of the stator blade pitch angle in the interval [70°; 90°], the absolute value of the dihedral angle of the leading edge of the stator blade is at least 2° greater than the absolute value of the dihedral angle of the trailing edge of the rotor blade, preferably at least 10° greater.

[0022] Alternatively, the projection of the trailing edge of the rotor blade onto a plane perpendicular to the main axis has a so-called lateral deviation along a so-called lateral direction, the lateral direction being perpendicular to the radial component of the main axis and the pitch axis of the rotor blade, wherein the projection of the leading edge of the stator blade onto a plane perpendicular to the main axis has a so-called lateral deviation along a so-called lateral direction, the lateral direction being perpendicular to the radial component of the pitch axis of the main axis and the pitch axis of the stator blade, wherein for at least one value of the pitch angle of the rotor blade in the interval [50°; 80°] and for at least one value of the pitch angle of the stator blade in the interval [70°; 90°], the lateral deviation of the leading edge of the stator blade is less than the lateral deviation of the trailing edge of the rotor blade.

[0023] Alternatively, the pitch angle has at least one value in the range [70°; 90°], and the leading edge of at least one pitch-variable stator blade has a tip located downstream of the radial component of the pitch axis.

[0024] Optionally, at least one pitch-variable stator blade has an activity factor between 50 and 200, preferably between 90 and 150.

[0025] An aircraft including an aviation propulsion unit according to the present invention is also proposed. Attached Figure Description

[0026] The invention will be better understood with the aid of the following description, which is given by way of example only and with reference to the accompanying drawings, in which: - Figure 1 This is a cross-sectional view of an aircraft propulsion unit according to the present invention. - Figure 2 yes Figure 1 The image shows a side view of the rotor blades of the propeller of an aircraft propulsion unit. - Figure 3 yes Figure 2 A cross-sectional view of the rotor blades in the image. - Figure 4 Is with Figure 2 A similar view shows the sweep angle of the rotor blades. - Figure 5 yes Figure 2 The front view of the rotor blades shows the dihedral angles of the rotor blades. - Figure 6 yes Figure 1 A side view of the stator blades of a fixed rectifier in an aircraft propulsion unit. - Figure 7 yes Figure 6 A cross-sectional view of the stator blades in the image. - Figure 8 Is with Figure 6 A similar view shows the sweep angle of the stator blades. - Figure 9 yes Figure 6 The front view of the stator blades shows the dihedral angles of the stator blades. - Figure 10 Is with Figure 6 A similar view shows stator blades with rounded tips. - Figure 11 This is a graph showing the evolution of the stator blade chord as a function of blade height. - Figure 12 This is a cross-sectional view of another aerospace propulsion unit according to the present invention, showing the spacing between the propeller and the stationary rectifier. - Figure 13 yes Figure 6 A cross-sectional view of the stator blades in the image, and - Figure 14 This is a front view of the trailing edge of the rotor blade and the leading edge of the stator blade. Detailed Implementation

[0027] In the following description, if a characteristic is applied to at least one element, then that characteristic can also be applied to all such elements. Similarly, if a characteristic is applicable to at least one value within a range, then that characteristic can also be applied to all values ​​within that range.

[0028] Reference Figure 1 The aviation propulsion unit 100 to which the present invention is applied will now be described. The aviation propulsion unit 100 is, for example, a turbine, a turbojet engine, or a turboshaft engine, since the type of aviation propulsion unit is not definitive here.

[0029] The aircraft propulsion unit 100 is designed to help propel the aircraft with an unducted single fan (USF).

[0030] The aircraft propulsion unit 100 first includes a housing 102 and a hub 104, the hub 104 being mounted to pivot about a main axis X relative to the housing 102.

[0031] In the following text, the terms "upstream" and "downstream" will be used to specify the relative positions of the elements of the aero-propulsion unit 100 along the main axis X in the direction of airflow PHI when the aircraft is propelled by the aero-propulsion unit 100. For example, the aircraft can be propelled by the aero-propulsion unit 100 in cruise mode at a flight Mach number greater than 0.7.

[0032] For example, hub 104 is located upstream of housing 102.

[0033] The aircraft propulsion unit 100 also includes a propeller 106, which is ductless and mounted on a hub 104 to pivot relative to the outer casing 102 about a main axis X. The propeller 106 is designed to drive a downstream airflow PHI to propel the aircraft in flight. For this purpose, the propeller 106 includes rotor blades 108 (e.g., 3 to 25, preferably 10 to 16), arranged, for example, in a single annular row around the main axis X. The rotor blades 108 may, for example, be all identical and spaced at regular angular intervals around the main axis X.

[0034] For example, at least one rotor blade 108 has a variable pitch about a corresponding pitch axis Y. The pitch axis Y may pass through or be slightly offset from the main axis X by, for example, up to 10 cm, up to 5 cm, up to 2 cm, or up to 1 cm. The pitch axis Y may be perpendicular to the main axis X, or at a small angle due to manufacturing tolerances or design intent. Thus, the pitch axis Y may be perpendicular, for example, within a tolerance range of 5°, 2°, 1°, or 0.1°. In all cases, the pitch axis Y forms a non-zero angle with the main axis X, and therefore has a non-zero radial component. As shown, the axis Y can therefore be radial, i.e., the axis Y forms a 90° angle with the main axis X. The pitch of each variable-pitch rotor blade 108 is defined by the pitch angle C described below. In a preferred embodiment, all rotor blades 108 have a variable pitch.

[0035] The aircraft propulsion unit 100 also includes an engine 110 for driving a hub 104 and thus driving a propeller 106 via the hub 104. For example, the engine 110 extends into a housing 102. The engine 110 is located, for example, downstream of the propeller 106. This arrangement is referred to as a “puller”. The engine 110 is, for example, a gas generator, which typically includes, from upstream to downstream, at least one compressor, at least one combustion chamber, and a power turbine configured to drive at least one propeller 106.

[0036] The aircraft propulsion unit 100 also includes a fixed ductless rectifier 112 mounted on a housing 102 downstream of the propeller 106. The rectifier 112 forms a stator located within the housing 102, extending about a main axis X but not rotating about it. The rectifier 112 includes, for example, stator blades 114 arranged in a single annular row around the main axis X. For example, 3 to 25 stator blades are provided, preferably 8 to 14. Preferably, the number of stator blades 114 differs from the number of rotor blades 108 to reduce noise in the aircraft propulsion unit 100. In particular, the number of rotor blades 108 is greater than the number of stator blades 114. In fact, if the number of rotor blades 108 and the number of stator blades 114 were equal, there would be a wake following the rotor blades 108, which would interact simultaneously with multiple stator blades 114, increasing the noise level. The stator blades 114 may be, for example, all identical or different, and spaced at an angle around the main axis X in a regular or non-uniform manner, such that at least two stator blades 114 have different angular spacings around the main axis X. Specifically, in the case of an aerospace propulsion unit installed in an aircraft, the stator blades 114: - It can have an outer radius smaller than that of the rotor blade 108 to reduce the interaction noise between the tip eddies of the rotor blade 108 and the stator blade 114; for each stator blade 114, this outer radius can be different in order to limit the interaction during the incident flight phase (such as landing and takeoff). - Stator blades can have different geometric characteristics (pitch angle, thickness, chord, etc.) to optimize operation based on the local properties of the flow; and - It can have uneven angular spacing around the main axis X, especially near the mast or pylon; this allows the operation of the stator blades 114 to be optimized depending on their installation in the aircraft.

[0037] The rectifier 112 is designed to rectify at least a portion of the airflow PHI passing through the propeller 106 to improve the performance of the aero propulsion unit 100. More specifically, the purpose of the rectifier 112 is to absorb the flow swirling caused by the propeller 106 to improve the performance of the ductless configuration. However, the presence of the rectifier introduces a major noise source from the interaction with the wake of the propeller 106 (and, when the stator blades 114 are not sufficiently trunculated, with the tip vortices). Therefore, it is important to reduce the noise generated by the rectifier 112 and its interaction with the wake of the propeller 106 while maintaining good aerodynamic performance, as reducing noise emissions and fuel consumption are major challenges for ductless engine architectures.

[0038] For example, at least one stator blade 114 has a variable pitch about a corresponding axis Y'. The pitch axis Y' may pass through or be slightly offset from the main axis X by, for example, up to 10 cm, up to 5 cm, up to 2 cm, or up to 1 cm. The pitch axis Y' may be perpendicular to the main axis X, or may be at a small angle due to manufacturing tolerances or design intent. Thus, the pitch axis Y' may be perpendicular, for example, within tolerances of 5°, 2°, 1°, or 0.1°. In all cases, the pitch axis Y forms a non-zero angle with the main axis X, and therefore has a non-zero radial component. As shown, the axis Y' can therefore be radial, i.e., the axis Y' forms a 90° angle with the main axis X. The pitch of each variable pitch stator blade 114 is defined by the pitch angle C', which will be described in more detail below. In a preferred embodiment, all stator blades 114 have a variable pitch.

[0039] When one of the stator blades is stationary (e.g., due to integration constraints, such as insufficient space below the hub to integrate a pitch control system or reduce weight), the blade's axis Y' can be defined by a line perpendicular to the main axis X, which passes through the leading edge BA' at the blade root. In this case, the blade has a fixed pitch angle C'.

[0040] The aircraft propulsion unit 100 also includes, for example, an air inlet 116 for supplying the mains air to the engine 110. The air inlet 116 is located, for example, between the propeller 106 and the rectifier 112.

[0041] Reference Figure 2 The rotor blade 108 first includes the leading edge BA (i.e. the front part of the rotor blade 108 facing the fluid (or initially in contact with the fluid) where the airflow PHI arrives, and the trailing edge BF (i.e. the rear part of the rotor blade 108 in the flow direction) where the airflow PHI departs.

[0042] The leading edge BA extends from the root BA_P (the point on the leading edge BA closest to the hub 104) to the tip BA_T (the highest point on the leading edge BA or the point with the largest radius relative to the main axis X on the upstream portion of the rotor blade 108). For at least one value of the pitch angle C in the interval [50°; 80°], the leading edge BA has a constant curvature between the root BA_P and the tip BA_T, i.e., without any inflection points (in other words, along the leading edge BA, the height h of the rotor blade 108 is constant). BA The function of the axial position x of the leading edge. BA Regarding h BA The second derivative of is not zero, that is, , and h BAIt is the height from the root BA_P). The curvature of the leading edge BA is also regular, i.e., there are no discontinuities. The leading edge BA also includes the ventral BA_V, and in particular, for at least one value of the pitch angle C in the interval [50°; 80°], the ventral BA_V is the upstream point of the leading edge BA (the smallest {x BA}).

[0043] Similarly, the trailing edge BF extends from the root BF_P (the point on the trailing edge BF closest to the hub 104) to the tip BF_T (the highest point on the trailing edge BF or the point with the largest radius relative to the main axis X on the rear portion of the rotor blade 108). For at least one value of the pitch angle C within the interval [50°; 80°], the trailing edge BF has a constant curvature between the root BF_P and the tip BF_T, i.e., no inflection point (in other words, along the trailing edge BF, the height h of the rotor blade 108 is constant). BF The function of the trailing edge BF, axial position x BF Regarding h BF The second derivative of is not zero, that is, , and h BF It is the height from the root BF_P). The curvature of the trailing edge BF is also regular, i.e., without discontinuities. The trailing edge BF also includes the ventral BF_V, specifically for at least one value of the pitch angle C in the interval [50°; 80°], where the ventral BF_V is the most upstream point of the trailing edge BF (minimum {x BF}).

[0044] The rotor blade 108 can also be truncated at its free end, as in the example shown, i.e., there is a truncated segment 202, for example a straight line, connecting the tips BA_T and BF_T. In this case, there is a curvature discontinuity at the tip BA_T between the leading edge BA and the truncated segment 202, and another curvature discontinuity at the tip BF_T between the truncated segment 202 and the trailing edge BF. Alternatively, the propeller blade can be untruncated, in which the tips BA_T and BF_T are combined.

[0045] In the following text, when applied in the context of rotor blade 108, the term "height" will refer to the distance between two points along the radial component of the pitch axis Y, that is, the distance between the orthogonal projections of these points onto the radial component of the pitch axis Y.

[0046] Therefore, the height H of the upstream blade positioned on the leading edge BA can be defined. 上游 Therefore, the upstream blade height H 上游 It is the height h from the root BA_P BA The total height H of the leading edge BA BA The ratio between (the root BA_P and the tip BA_T): H 上游 =hBA / H BA Therefore, the upstream blade height H 上游 This can be expressed as a percentage and varies between 0% (at the root BA_P) and 100% (at the tip BA_T). Similarly, the height H of the downstream blade located on the trailing edge BF can be defined. 下游 Therefore, the downstream blade height H 下游 It is the height h from the root BF_P BF The total height H of the trailing edge BF BF The ratio between (root BF_P and tip BF_T): H 下游 =h BF / H BF Therefore, the downstream blade height H 下游 It can be expressed as a percentage and varies between 0% (the position at the root BF_P) and 100% (the position at the tip BF_T).

[0047] Furthermore, specifically for at least one value of the pitch angle C within the interval [50°; 80°], the propeller 106 has an outer radius Re, which is defined as equal to the height or distance between the main axis X and the point on the rotor blade 108 furthest from the main axis X. In the example shown, this furthest point is the tip BA_T of the leading edge BA.

[0048] Figure 3 It is the cross-section (also known as the aerodynamic profile) of the rotor blade 108 at a certain height, which is perpendicular to the radial component of the pitch axis Y.

[0049] As can be seen, the rotor blade 108 has a pressure side 302 and a suction side 304 that are concave and convex, respectively, and the pressure side 302 and the suction side 304 are connected to each other by a leading edge BA and a trailing edge BF. Therefore, the leading edge BA separates the pressure side 302 and the suction side 304 in the upstream portion of the rotor blade 108, while the trailing edge BF separates the pressure side 302 and the suction side 304 in the rear portion of the rotor blade 108.

[0050] The leading edge BA is, for example, a point on the cross-section of the upstream portion of the rotor blade 108, having a local minimum radius of curvature. Similarly, when the downstream portion of the rotor blade is rounded, the trailing edge BF is, for example, a point on the cross-section of that downstream portion, exhibiting a local minimum radius of curvature. To simplify the manufacturing method of the rotor blade 108, the downstream portion of the rotor blade can be truncated. In the case where the downstream portion of the rotor blade is truncated, the trailing edge BF is, for example, the midpoint of the truncated portion.

[0051] When the leading edge BA and the trailing edge BF exist in the cross section under consideration (i.e., at a height not too close to the root BA_P and below the truncated section 202), the leading edge BA and the trailing edge BF can be connected by a chord 306, the orientation of which varies depending on the height under consideration. The leading edge BA and the trailing edge BF are separated by a distance on the chord 306, referred to as chord length L, which varies depending on the height under consideration.

[0052] Therefore, an angle A exists between any plane P perpendicular to the main axis X and the chord 306 at a certain height. This angle A can therefore be varied depending on the height considered. To explicitly identify the pitch, the pitch angle C is chosen as the previous angle A at a height of 75% of the outer radius Re of the rotor blade 108 (see...). Figure 2 The pitch angle C is measured, for example, on the upstream side of plane P, with its positive direction being from plane P to chord 306. This direction coincides with the direction from pressure side 302 to suction side 304.

[0053] Reference Figure 4 Furthermore, the sweep angle F of the rotor blade 108 can be defined, which is based on the blade height H. 上游 And it changes. By definition, the sweep angle F is the radial component of the pitch axis Y intersecting the line 402 in the plane formed by the radial component of the pitch axis Y and the principal axis X. Figure 4 The angle between the projections on the drawing plane, line 402 connects the blade height H under consideration. 上游 Point 404 on the leading edge BA and at the considered blade height H 上游 Add the total height H BA Point 406 on the leading edge BA at 1%.

[0054] Reference Figure 5 Furthermore, the dihedral angle D of the rotor blade 108 can be defined at the leading edge BA. BA The dihedral angle is based on the blade height H. 上游 However, this changes. By definition, the dihedral angle D at the leading edge BA... BA The pitch axis Y (or more generally, the radial component of the pitch axis Y) and line 402 lie in a plane perpendicular to the main axis X and containing the pitch axis Y (or more generally, the radial component of the pitch axis Y). Figure 5 The angle between the projections on the paper plane. As mentioned above, line 402 connects the leading edge BA at the blade height H under discussion. 上游 Point 404 and leading edge BA at the blade height H under discussion 上游 Add the total height H BA Point 406 at 1% of the value. Similarly, the dihedral angle D can be defined at the trailing edge BF. BF .

[0055] Reference Figure 6 The stator blade 114 first includes the leading edge BA' (i.e. the front part of the stator blade 114 facing the fluid (or initially in contact with the fluid) reached by the airflow PHI from the propeller 106) and the trailing edge BF' (i.e. the rear part of the stator blade 114 in the flow direction) where the airflow PHI leaves.

[0056] The leading edge BA' extends from the root BA'P (the point on the leading edge BA' closest to the outer casing 102) to the tip BA'T (the highest point of the leading edge BA' or the point with the largest radius relative to the main axis X on the upstream portion of the stator blade 114). Specifically, for at least one value of the pitch angle C' within the interval [70°; 90°], the leading edge BA' has a constant curvature between the root BA'_P and the tip BA'_T, i.e., without any inflection points (in other words, along the leading edge BA, as the height h' of the stator blade 114). BA The function, the axial position x' of the leading edge BA' BA Regarding h' BA The second derivative of is not zero, that is, , and h' BA It is the height from the root BA'_P). The curvature of the leading edge BA' is also regular, i.e., without discontinuities. The leading edge BA' also includes the ventral BA'_V, and in particular, for at least one value of the pitch angle C' in the interval [70°; 90°], the ventral BA'_V is the upstream point of the leading edge BA' (minimum {x' BA}).

[0057] Similarly, the trailing edge BF' extends from the root BF'_P (the point on the trailing edge BF' closest to the outer shell 102) to the tip BF'_T (the highest point on the trailing edge BF' or the point with the largest radius relative to the main axis X on the rear portion of the stator blade 114). Specifically, for at least one value of the teaching angle C' within the interval [70°; 90°], the trailing edge BF' has a constant curvature between the root BF'_P and the tip BF'_T, i.e., no inflection point (in other words, along the trailing edge BF', the height h' of the stator blade 114...). BF The function of the trailing edge BF' axial position x' BF Regarding h' BF The second derivative of is not zero, that is, , and h' BF It is the height from the root BF'_P). The curvature of the trailing edge BF' is also regular, i.e., there is no discontinuity. The trailing edge BF' also includes the ventral BF'_V, and in particular, for at least one value of the pitch angle C' in the interval [70°; 90°], the ventral BF'_V is the upstream point of the trailing edge BF' (minimum {x'BF}).

[0058] Stator blade 114 can also be truncated, as in the example shown, i.e., there is a truncated segment 602 connecting the tips BA'_T and BF'_T, which is a straight line. In this case, there is a curvature discontinuity at the tip BA'_T between the leading edge BA' and the truncated segment 602, and also a curvature discontinuity at the tip BF'_T between the truncated segment 602 and the trailing edge BF'. Alternatively, the stator blade can be untruncated, in which case the tips BA'T and BF'T will be combined.

[0059] In the following text, when applied in the context of stator blade 114, the term “height” will refer to the distance between two points along the radial component of the pitch axis Y’, that is, the distance between the orthogonal projections of these points onto the radial component of the pitch axis Y’.

[0060] Therefore, the height H' of the upstream blade positioned on the leading edge BA' can be defined. 上游 Therefore, the upstream blade height H' 上游 It is the height h' from the root BA'_P BA The total height H' of the leading edge BA' BA The ratio between (the root BA'_P and the tip BA'_T): H' 上游 =h' BA / H' BA Therefore, the upstream blade height H' 上游 This can be expressed as a percentage and varies between 0% (at the root BA'_P) and 100% (at the tip BA'_T). Similarly, the height H' of the downstream blade located on the trailing edge BF' can be defined. 下游 Therefore, the downstream blade height H' 下游 It is the height h' from the root BF'_P BF The total height H' of the trailing edge BF' BF The ratio between (the root BF'_P and the tip BF'_T): H' 下游 =h' BF / H' BF Therefore, the downstream blade height H' 下游 It can be expressed as a percentage and varies between 0% (the position at the root BF'P) and 100% (the position at the tip BF'T).

[0061] Furthermore, specifically for at least one value of the pitch angle C' within the interval [70°; 90°], each variable-pitch stator blade 114 of the rectifier 112 has an outer radius Re', which is defined as equal to the height or distance between the main axis X and the point on the stator blade 114 furthest from the main axis X. In the example shown, this furthest point is the tip BF'_T of the trailing edge BF'. Alternatively, this furthest point could be the tip BA'_T of the leading edge BA'.

[0062] Each variable-pitch stator blade 114 also has an inner radius Ri' at its leading edge BA'. BA The inner radius Ri' BA It is the distance between the principal axis X and the root BA'_P of the leading edge BA, and has an inner radius Ri' at the trailing edge BF'. BF The inner radius Ri' BF It is the distance between the principal axis X and the root BF'_P of the trailing edge BF'.

[0063] Figure 7 and Figure 13 The cross-sections of the stator blade 114 at different heights are shown, with the radial component perpendicular to the pitch axis Y'.

[0064] As can be seen, the stator blade 114 has a pressure side 702 that is concave and a suction side 704 that is convex, respectively, and the pressure side 702 and the suction side 704 are connected to each other by a leading edge BA' and a trailing edge BF'. Therefore, the leading edge BA' separates the pressure side 702 and the suction side 704 in the upstream portion of the stator blade 114, while the trailing edge BF' separates the pressure side 702 and the suction side 704 in the rear portion of the stator blade 114.

[0065] The leading edge BA' is, for example, a point on the cross-section of the upstream portion of the stator blade 114, having a local minimum radius of curvature. Similarly, when the downstream portion of the stator blade is rounded, the trailing edge BF' is, for example, a point on the cross-section of that downstream portion, exhibiting a local minimum radius of curvature. To simplify the method for manufacturing the stator blade 114, the downstream portion of the stator blade can be truncated. In the case where the downstream blade of the stator blade is truncated, the trailing edge BF' is, for example, the midpoint of that truncated portion.

[0066] When the leading edge BA' and trailing edge BF' are present in the cross-section under consideration (i.e., below the truncated section 602, for example, in the example shown), the leading edge BA' and trailing edge BF' can be connected by a chord 706, the orientation of which varies depending on the height under consideration. The leading edge BA' and trailing edge BF' are separated on the chord 706 by a distance referred to as the chord length L', which can vary depending on the height under consideration.

[0067] Therefore, an angle A' exists between any plane P' perpendicular to the main axis X and the chord 706 at a certain height. This angle A' can therefore be varied depending on the height considered. To explicitly identify the pitch, the pitch angle C' is chosen as the previous angle A' at a height of 75% of the outer radius Re' of the stator blade 114 (see [reference]). Figure 6 The pitch angle C' is measured, for example, on the upstream side of plane P', with its positive direction being from plane P' to chord 706. This direction coincides with the direction from pressure side 702 to suction side 704.

[0068] Reference Figure 8 Furthermore, the sweep angle F' of the stator blade 114 can be defined, which is based on the blade height H'. 上游 And it changes. By definition, the sweep angle F' is the angle between the radial component of the pitch axis Y' and the projection of line 402 onto the plane formed by the radial component of the pitch axis Y' and the principal axis X, with line 402 connecting the blade height H' under consideration. 上游 Point 804 on the leading edge BA' and at the considered blade height H' 上游 Add the total height H' BA Point 806 on the leading edge BA' at 1%.

[0069] Reference Figure 9 Furthermore, the dihedral angle D' of the stator blade 114 can be defined at the leading edge BA'. BA' The dihedral angle is based on the blade height H' 上游 And change. By definition, the dihedral angle D' at the leading edge BA'... BA' It is the angle between the radial component of the pitch axis Y' and the projection of line 802 onto a plane perpendicular to the main axis X and containing the radial component of the pitch axis Y'. Similarly, the dihedral angle D' can be defined at the trailing edge BF'. BF' .

[0070] The shape of the stator blades 114 of the rectifier 112 is designed to reduce noise pollution while ensuring good aerodynamic performance.

[0071] Therefore, for at least one value of the pitch angle C' within the range [70°; 90°], the tip BA'_T of the leading edge BA' is located downstream of the pitch axis Y' along a straight line parallel to the main axis X and passing through the tip BA'_T. In this way, the free end of the stator blade 114 moves away from the propeller 106, which reduces noise over a wide range of pitch angles C'. The downstream positioning of the free end of the stator blade 114 enables the reduction of interaction noise between the propeller wake and the leading edge BA' of the stator blade, i.e., by increasing the distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114, the noise source along the leading edge BA' is decorrelated and the propeller wake of 106 is dissipated.

[0072] Preferably, to facilitate the downstream positioning of the free end of the stator blade 114, for at least one value of the pitch angle C' within the interval [70°; 90°], the belly BA'_V, the root BA'_P, and the pitch axis Y' follow each other in this order from upstream to downstream along the main axis X. In other words, for at least one value of the pitch angle C' within the interval [70°; 90°], x BA'_V <x BA'_P <x Y' Therefore, a sweep angle F' can be added to the upper portion of the stator blade 114, particularly near the free end of the stator blade 114. When the pitch axis Y' is tilted or not perpendicular to the main axis X, x Y' The axial position of the pitch axis Y' of the stator blades at the housing 102 corresponds to the position of the blades. Furthermore, for at least one value of the pitch angle C' within the range [70°; 90°], the belly BA'_V, the root BA'_P, and the tip BA'_T preferably follow each other in this order from upstream to downstream along the main axis X.

[0073] Even more preferably, in order to facilitate the downstream positioning of the free end of the stator blade 114, the belly BA'_V is located at the total blade height H' BA It is between 20% and 70%, preferably located at the total blade height H' BAThe sweep angle is between 25% and 55%. This allows the belly BA'_V to be positioned close to the outer casing 102, and thus increases the sweep angle F' from a relatively low radial position, which reduces interaction noise. Therefore, a large sweep angle F' can be achieved in the upper portion of the stator blade 114, particularly near the free end of the stator blade 114. Furthermore, this positioning of the belly BA'_V causes the mass in the lower portion of the stator blade 114 to move upstream, which allows the mass in the upper portion of the stator blade 114 to move downstream (and therefore towards the free end) without significantly altering the center of mass of the stator blade 114 and having little effect on the aerodynamic torque about the pitch-changing axis. This is beneficial for the size and mechanical balance of the stator blade 114.

[0074] Utilizing this positioning of the ventral part BA'_V of the leading edge BA', the ventral part BF'_V of the trailing edge BF' is preferably located at the total blade height H' of the trailing edge. BF The total blade height H' is preferably between 20% and 70% of the trailing edge. BF Between 30% and 60%. This ensures that the belly BF'_V of the trailing edge BF' is located at a height relatively close to the belly BA'_V of the leading edge BA', which may be useful for the mechanical strength of the stator blade 114. Similar to the position of the belly BA'_V of the leading edge BA', this position of the belly BF'_V of the trailing edge BF' causes the mass in the lower portion of the stator blade 114 to move upstream, which makes it possible to move the mass in the upper portion of the stator blade 114 downstream (and therefore towards the free end) without significantly altering the center of mass of the stator blade 114.

[0075] In one embodiment, the height or radius (height or distance from the main axis X) of the ventral BA' of the leading edge BA' is smaller than the height or radius (height or distance from the main axis X) of the ventral BF' of the trailing edge BF'. This improves the mechanical strength of the blade and makes the chord L' more evenly distributed along the span (see...). Figure 11 ).

[0076] Furthermore, for at least one value of the pitch angle C' within the range [70°; 90°], by utilizing this positioning of the belly BA'V of the leading edge BA', stator blades 114 that satisfy one or more of the following three criteria can be obtained, thereby enabling an acceptable aeroacoustic and mechanical compromise.

[0077] According to the first criterion, the ventral part BA'_V of the leading edge BA' and the tip BF'_T of the trailing edge BF' are separated along the principal axis X by a distance greater than or equal to a coefficient K multiplied by the maximum chord length L' (maximum {L'}), where K is between 1 and 2, preferably between 1.2 and 1.6. The following equation summarizes this first criterion: x BF'_T -xBA'_V ≥K*Maximum {L'}, where x M It is the axial position of point M along the principal axis X.

[0078] According to the second criterion, the ventral BA'_V and apical BA'_T of the leading edge BA' are separated along the principal axis X by a distance less than or equal to the coefficient B multiplied by the maximum chord L' (maximum {L'}), where B is between 0.5 and 1.2. The following equation summarizes this second criterion: x BA'_T -x BA'_V ≤B*maximum{L'}.

[0079] According to the third criterion, the root BF'_P and tip BF'_T of the trailing edge BF' are separated by a distance along the principal axis X greater than or equal to a coefficient E multiplied by the maximum chord length L' (maximum {L'}), where E is between 0.05 and 0.7, preferably between 0.25 and 0.6. The third criterion is summarized by the following equation: x BF'_T -x BF'_P ≤E*maximum{L'}.

[0080] Even more preferably, to facilitate the downstream positioning of the free end of the stator blade 114, the chord length L' of the cross section at the tip BA'_T closest to the leading edge BA' is smaller than the chord length L' at the root BA'_P of the leading edge BA' and / or the root BF'_P of the trailing edge BF', and the chord length at the root of the leading edge and / or the root of the trailing edge is itself smaller than the chord length L' of the cross section at the belly BA'_V of the leading edge BA' ("smaller than" means "has a smaller length"). Increasing the chord length L' at the belly BA'_V and decreasing the chord length L' at the tip BA'_T increases the sweep angle F' at the upper portion of the stator blade 114, and thus moves the free end of the stator blade 114 further downstream, which is advantageous for noise reduction. Furthermore, when the chord length L' at the root BA'_P is greater than the chord length L' at the tip BA'_T, the mechanical strength of the blade (e.g., after bird ingestion) is improved. Furthermore, the smaller the chord length L' at the tip BA'_T, the lighter the free end of the stator blade 114, and therefore the more likely it is to place the free end downstream without causing the center of mass of the stator blade 114 to move too much.

[0081] For example, the sweep angle F' at the leading edge BA' of stator blade 114 is greater than 20°, and at the upstream blade height H' 上游 More than 80% of the area is preferably greater than 35°, at a height H' above the upstream blade. 上游 At a position of over 90%, or even more preferably greater than 45°, above the upstream blade height H' 上游More than 95% of the positions, or even more preferably greater than 50°, are located at this angle. This reduces the velocity component perpendicular to the trace of the leading edge BA' of the cross section, thereby reducing interaction noise.

[0082] Even more preferably, to facilitate the downstream positioning of the free end of the stator blade 114, for at least one value of the pitch angle C' within the interval [70°; 90°], the belly BF'_V is located upstream of the root BF'_P, and the root BF'_P itself is located upstream of the tip BF'_T. In other words, for at least one value of the pitch angle C' within the interval [70°; 90°], x BF'_V <x BF'_P <x BF'_T .

[0083] Reference Figure 10 This shows a non-truncated stator blade 114 with a rounded tip.

[0084] Reference Figure 11 Preferably, the chord length L' extends from the upstream blade height H' 上游 and / or downstream blade height H' 下游 40% to 100%, preferably from 50% to 100% (therefore in Figure 11 In the attached figure, the reference numeral H' can represent H' 上游 or H' 下游 Strictly decreasing. Especially when there are integrated or mechanical constraints preventing the trailing edge BF' of stator blade 114 from being modified or offset, this allows, on the one hand, the distance between the trailing edge BF of rotor blade 108 and the leading edge BA' of stator blade 114 to be increased, and on the other hand, it allows the sweep angle F' towards the free end of stator blade 114 to be increased. In fact, offsetting the trailing edge BF' to the upper portion of the blade (e.g., on the tip section 602) increases the aerodynamic moment about the pitch axis Y', and therefore has a significant impact on the mechanical dimensions of the pitch-changing system. The parameter providing the first estimate of the chord length distribution along the span of stator blade 114 is its activity factor (AF), which is defined as follows: Where Ri' is the inner radius Ri' of stator blade 114 at its leading edge BA'. BA Or the inner radius Ri' of stator blade 114 at the trailing edge BF' BF (see Figure 6 Re' is the outer radius Re' of stator blade 114 at its leading edge BA'. BA Or the outer radius Re' of stator blade 114 at trailing edge BF' BF ; L'(ξ) represents the radial distance from the principal axis X divided by the outer radius Re'; L'(ξ) represents the radial distance... The chord length between the leading edge BA' and trailing edge BF' of the cross section (or aerodynamic profile) of the stator blade 114 in a plane perpendicular to the radial component of the pitch axis Y'.

[0085] The activity factor of the stator blade 114 is preferably between 50 and 200, more preferably between 90 and 150. Using values ​​such as these ensures that the chord length L' in the lower portion of the stator blade 114 is sufficient, which contributes to the mechanical strength of the blade, and that reducing the chord length L' in the upper portion of the stator blade 114 increases the sweep angle in the upper portion of the blade and thus reduces noise.

[0086] Even more preferably, at the upstream blade height H' 上游 and / or downstream blade height H' 下游 The chord length L' at 95% is less than or equal to half of the maximum chord length L' of stator blade 114: L'(H'=95%)≤0.5*maximum{L'}, where H'=H' 上游 or H' 下游 This allows for an increase in the sweep angle F' relative to the mid-span and near the blade belly, which is beneficial from an aeroacoustic perspective, as well as a reduction in the mass of the blade in the upper portion, which is beneficial from a mechanical perspective, and a reduction in inertia in the event of blade tip loss (e.g., in the case of bird ingestion) or blade loss events (fan blade out (FBO)).

[0087] Even more preferably, 95% of the upstream blade height H' 上游 and / or downstream blade height H' 下游 The chord length L' at the point is less than or equal to 10% of the upstream height H' 上游 and / or downstream height H' 下游 Half of the chord L' at point H': L'(H'=95%)≤0.5*L'(H'=10%), where H'=H' 上游 or H' 下游 This reduces inertia in the event of leaf tip loss (e.g., in the case of bird ingestion) or leaf loss.

[0088] See Figure 12 The downstream positioning of the free end of the stator blade 114 ensures a large distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114, thereby reducing the noise of the aero-propulsion unit 100. Specifically, for at least one value of the pitch angle C in the range [50°; 80°] and at least one value of the pitch angle C' in the range [70°; 90°], at the upstream blade height H' 上游 and / or downstream blade height H'下游 At 95%, the axial distance s (along the main axis X) between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114 is preferably greater than 0.35 times the Reynolds number (Re) of the propeller 106, and even more preferably greater than 0.5 times the Reynolds number.

[0089] Figure 14 This is shown in a plane perpendicular to the principal axis X ( Figure 14 The projection y of the trailing edge BF of rotor blade 108 on the plane of the paper BF The projection y of the leading edge BA' of stator blade 114 BA' .

[0090] It can be seen that at least one stator blade 114 has a dihedral angle D' at 95% of its outer radius Re'. BA' For at least one value of the pitch angle C' within the interval [70°; 90°], the dihedral angle D' BA' The absolute value is greater than 1°, preferably 3°, and even more preferably 10°.

[0091] Preferably, for at least one value of the pitch angle C' within the interval [70°; 90°], the dihedral angle D' is located at 95% of the outer radius Re'. BA' The absolute value of the dihedral angle D of the leading edge BA' of stator blade 114 at 50% of the outer radius Re' is equal to that of the angle between the two sides. BA' The angle is at least 1°, preferably at least 3°, or even more preferably at least 10°.

[0092] Even more preferably, for at least one value of the pitch angle C' within the interval [70°; 90°], the dihedral angle D on the leading edge BA' of the stator blade 114 BA' The absolute value of is strictly monotonic for radial positions greater than 90% of the outer radius Re'.

[0093] Even more preferably, for at least one value of the pitch angle C' within the interval [70°; 90°], the projection y of the leading edge BA' of the stator blade 114 onto a plane perpendicular to the main axis X BA' It has at least one local maximum and / or minimum value.

[0094] Even more preferably, for at least one value of the pitch angle C' within the interval [70°; 90°], the projection y of the leading edge BA' of the stator blade 114 onto a plane perpendicular to the main axis X BA' It has at least one inflection point PI.

[0095] In addition, the protrusion y at the trailing edge BF of rotor blade 108 BF The protrusion y at the leading edge BA' of stator blade 114 BA'They move in the opposite direction as they approach their free ends. At least for the blade height H' of stator blade 114. 上游 Greater than 80%, for rotor blade 108, the pitch angle C is at least one value within the interval [50°; 80°], and for stator blade 114, the pitch angle C' is at least one value within the interval [70°; 90°], this is by assuming the dihedral angle D of the leading edge BA' of stator blade 114 is greater than 80%. BA' This is achieved by having the opposite sign to the dihedral angle DBF of the trailing edge BF of the rotor blade 108. Therefore, the leading edge BA' of the stator blade 114 is no longer aligned with the trailing edge BF of the rotor blade 108 from this height (80%), and thus no longer aligned with the wake of the propeller 106. In this way, the propeller 106 and rectifier 112, which form noise sources, are uncorrelated with each other, making it possible to reduce the interaction noise between the propeller 106 and rectifier 112 from this height.

[0096] Preferably, for at least one value of the pitch angle C of the rotor blade 108 within the interval [50°; 80°] and for at least one value of the pitch angle C' of the stator blade 114 within the interval [70°; 90°], the dihedral angle D' of the leading edge BA' of the stator blade 114... BA' The absolute value is greater than the dihedral angle D of the trailing edge BF of the rotor blade 108. BF 20% of the absolute value, i.e., |D' BA' |>0.2*|D BF |

[0097] More preferably, the dihedral angle D' of the leading edge BA' of the stator blade 114 BA The dihedral angle D with the trailing edge of rotor blade 108 BF They are not equal; or, for at least one value of the pitch angle C of the rotor blade 108 in the interval [50°; 80°] and for at least one value of the pitch angle C' of the stator blade 114 in the interval [70°; 90°], at any radial position (height or distance from the main axis X), the dihedral angle D' of the leading edge BA' of the stator blade 114 is... BA' The absolute value is greater than the dihedral angle D of the trailing edge BF of the rotor blade 108. BF 130%; or, for at least one value of the pitch angle C of the rotor blade 108 in the interval [50°; 80°] and at least one value of the pitch angle C' of the stator blade 114 in the interval [70°; 90°], at any radial position, the dihedral angle D' of the leading edge BA' of the stator blade 114 BA' The dihedral angle D of the trailing edge BF of the rotor blade is less than 108. BF 50%.

[0098] The dihedral angle D' of the leading edge BA' of stator blade 114BA' The optimal value depends on the dihedral angle D of the trailing edge BF of rotor blade 108. BF When the wake of rotor blade 108 interacts with stator blade 114, this maximizes the phase shift. This is particularly important in the upper portion of the blade near its free end, where the noise source is more intense.

[0099] Even more preferably, the dihedral angle D' of the leading edge BA' of the stator blade 114 BA' The absolute value is at 95% of the upstream blade height H' 上游 At an angle greater than 15°, or even more preferably at 95% of the upstream blade height H' 上游 The angle is greater than 30°. For the rotor blade 108, the pitch angle C is at least one value in the interval [50°; 80°] and for the stator blade (114), the pitch angle (C') is at least one value in the interval [70°; 90°], the dihedral angle D of the leading edge BA' of the stator blade 114 is greater than 30°. BA’ The size is relatively large at the blade tip, which is useful for reducing the sound level by increasing the phase shift of the noise source.

[0100] As can be further seen, the projection y of the trailing edge BF of rotor blade 108 onto a plane perpendicular to the main axis X BF With a lateral deviation Δy along the lateral direction T BF The lateral direction T is perpendicular to the radial component of the main axis X and / or the pitch axis Y. Similarly, the projection of the leading edge BA' of the stator blade 114 onto a plane perpendicular to the main axis X has a lateral deviation Δy along the lateral direction T' perpendicular to the radial component of the main axis X and / or the pitch axis Y'. BA' .

[0101] Preferably, for at least one value of the pitch angle C' within the interval [70°; 90°], the lateral deviation Δy of the leading edge BA' of the stator blade 114 BA' The radius of the stator blade 114 is greater than 1% of the outer radius Re' of the stator blade and less than 10% of the outer radius of the stator blade. This ensures that the stator blade 114 does not tilt too much in the lateral direction T', which may be beneficial to the blade's balance and / or mechanical strength.

[0102] Preferably, for at least one value of the pitch angle C of the rotor blade 108 within the interval [50°; 80°] and for at least one value of the pitch angle C' of the stator blade 114 within the interval [70°; 90°], the deviation Δy of the leading edge BA' of the stator blade 114 BA' For all operation points, the distance Δy is less than the distance Δy BFThis maximizes the phase shift and / or interaction between the propeller wake (generated at the trailing edge BF of rotor blade 108) and the leading edge BA' of downstream stator blade 114. In fact, the deviation Δy BA' The larger the blade, the larger the dihedral angle can be on the leaf (especially at the leaf tip).

[0103] In summary, it should be noted that the present invention is not limited to the embodiments described above. In fact, those skilled in the art can make various modifications to the embodiments based on the teachings just disclosed.

[0104] In the foregoing detailed description of the invention, the terminology used should not be construed as limiting the invention to the embodiments disclosed in this specification, but should be construed as including all equivalents that can be obtained by those skilled in the art by applying their common sense to the implementation of the teachings just disclosed.

Claims

1. A ductless aero-propulsion unit (100) for an aircraft, comprising: -Outer shell (102); - Hub (104), which is pivotally mounted relative to the outer shell (102) about a main axis (X) extending in the upstream-downstream direction of the aircraft; - A propeller (106) mounted on the hub (104) so ​​as to be pivotable relative to the housing (102); as well as - A fixed rectifier (112) mounted on the housing (102) downstream of the propeller (106) along the main axis (X), the fixed rectifier (112) extending about the main axis (X) and including at least one stator blade (114) having a variable pitch about a pitch axis (Y'), each pitch-variable stator blade (114) having a pitch angle (C') defined as the angle between any plane (P') perpendicular to the main axis (X) on one hand and a chord (706) connecting the leading edge (BA') of the stator blade (114) to the trailing edge (BF') of the stator blade (114) on the other hand; The characteristic feature is that the chord (706) is obtained at 75% of the outer radius (Re') of the stator blade (114) relative to the main axis (X), wherein, for at least one value of the pitch angle (C') within the interval [70°; 90°], the leading edge (BA') of at least one stator blade (114) has a dihedral angle (D') at 95% of the outer radius (Re') with an absolute value greater than 1°, preferably greater than 3°, and even more preferably greater than 10°. BA' Furthermore, for at least one value of the pitch angle (C') within the interval [70°; 90°], the projection of the leading edge (BA') of the stator blade (114) onto a plane perpendicular to the main axis (X) has at least one local maximum and / or minimum value.

2. The aviation propulsion unit (100) according to claim 1, wherein, For at least one value of the pitch angle (C') within the interval [70°; 90°], the dihedral angle (D') of the leading edge (BA') of the stator blade (114) at 95% of the outer radius (Re') is... BA’ The absolute value of ) is more than the dihedral angle (D') at 50% of the outer radius (Re'). BA’ The absolute value of ) is at least 1° greater, preferably at least 3° greater, or even more preferably at least 10° greater.

3. The aviation propulsion unit (100) according to claim 1 or 2, wherein, For at least one value of the pitch angle (C') within the interval [70°; 90°], the dihedral angle (D') on the leading edge (BA') of the stator blade (114) BA’ The absolute value of is strictly monotonic for radial positions greater than 90% of the outer radius (Re').

4. The aviation propulsion unit (100) according to any one of claims 1 to 3, wherein, The projection (y) of the leading edge (BA') of the stator blade (114) onto a plane perpendicular to the main axis (X) BA' It has a so-called lateral deviation (Δy) along the so-called lateral direction (T'). BA' The lateral component of the lateral direction perpendicular to the main axis (X) and the pitch axis (Y'), for at least one value of the pitch angle (C') within the interval [70°; 90°], the lateral deviation (Δy) of the leading edge (BA') of the stator blade (114) BA' The value is greater than 1% of the outer radius (Re') of the stator blade (114) and less than 10% of the outer radius of the stator blade.

5. The aviation propulsion unit (100) according to any one of claims 1 to 4, wherein, For at least one value of the pitch angle (C') within the interval [70°; 90°], the projection of the leading edge (BA') of the stator blade (114) onto a plane perpendicular to the main axis (X) has at least one inflection point (PI).

6. The aviation propulsion unit (100) according to any one of claims 1 to 5, wherein, The propeller (114) includes at least one rotor blade (108) having a variable pitch about a pitch axis (Y) that passes through the main axis (X) and has a non-zero radial component relative to the main axis (X). Each variable-pitch rotor blade (108) has a pitch angle (C) defined as the angle between an arbitrary plane (P) perpendicular to the main axis (X) on one hand and a chord (306) connecting the leading edge (BA) of the rotor blade (108) to the trailing edge (BF) of the rotor blade (108) on the other hand. The chord (306) is intercepted in a plane perpendicular to the radial component of the pitch axis (Y) and passes through the rotor blade (108) at 75% of the outer radius (Re) of the rotor blade (108) relative to the main axis (X).

7. The aviation propulsion unit (100) according to claim 6, wherein, The trailing edge (BF) of the rotor blade (108) and the leading edge (BA') of the stator blade (114) have a dihedral angle (D). BF D' BA' ), such that for at least one value of the pitch angle (C) of the rotor blade (108) in the interval [50°; 80°] and for at least one value of the pitch angle (C') of the stator blade (114) in the interval [70°; 90°], the dihedral angle (D) on the trailing edge (BF) of the rotor blade (108) is such that... BF The absolute value of ) is greater than the dihedral angle (D) on the leading edge (BA') of the stator blade (114) at 95% of the outer radius (Re') of the stator blade (114). BA' The absolute value of ).

8. The aviation propulsion unit (100) according to claim 6 or 7, wherein, The trailing edge (BF) of the rotor blade (108) and the leading edge (BA') of the stator blade (114) have a dihedral angle (D). BF D' BA' ), such that for at least one value of the pitch angle (C) of the rotor blade (108) in the interval [50°; 80°] and for at least one value of the pitch angle (C') of the stator blade (114) in the interval [70°; 90°], the dihedral angle (D) on the trailing edge (BF) of the rotor blade (108) is such that... BF The absolute value of the dihedral angle (D) on the leading edge (BA') of the stator blade (114) is 75% of the outer radius (Re') of the stator blade (114). BA The absolute value of ) is at least 10° greater.

9. The aviation propulsion unit (100) according to any one of claims 6 to 8, wherein, For at least one value of the pitch angle (C) of the rotor blade (108) within the interval [50°; 80°] and for at least one value of the pitch angle (C') of the stator blade (114) within the interval [70°; 90°], the trailing edge (BF) of the rotor blade (108) and the leading edge (BA') of the stator blade (114) have dihedral angles (D') of opposite signs at 95% of the outer radius (Re') of the stator blade (114). BF D' BA' ).

10. The aviation propulsion unit (100) according to any one of claims 6 to 9, wherein, At any height from the main axis (X), for at least one value of the pitch angle (C) of the rotor blade (108) within the interval [50°; 80°] and for at least one value of the pitch angle (C') of the stator blade (114) within the interval [70°; 90°], the dihedral angle (D) of the leading edge (BA') of the stator blade (114) BA' The absolute value of ) is compared with the dihedral angle (D) of the trailing edge (BF) of the rotor blade (108). BF The absolute value of ) is at least 2° greater, preferably at least 10° greater.

11. The aircraft propulsion unit (100) according to any one of claims 6 to 10, wherein, The projection of the trailing edge (BF) of the rotor blade (108) onto a plane perpendicular to the main axis (X) has a so-called lateral deviation (Δy) along the so-called lateral direction (T). BF The lateral direction is perpendicular to the radial component of the main axis (X) and the pitch axis (Y) of the rotor blade (108), wherein the projection of the leading edge (BA') of the stator blade (114) onto a plane perpendicular to the main axis X has a so-called lateral deviation (Δy) along the so-called lateral direction (T'). BA' The lateral direction is perpendicular to the radial component of the main axis (X) and the pitch axis (Y') of the stator blade, for at least one value of the pitch angle (C) of the rotor blade (108) in the interval [50°; 80°] and for at least one value of the pitch angle (C') of the stator blade (114) in the interval [70°; 90°], the lateral deviation (Δy) of the leading edge (BA') of the stator blade (114). BA' The lateral deviation (Δy) is smaller than the trailing edge (BF) of the rotor blade (108). BF ).

12. The aircraft propulsion unit (100) according to any one of claims 1 to 11, wherein, For at least one value of the pitch angle (C') within the interval [70°; 90°], the leading edge (BA') of at least one pitch-variable stator blade (114) has a tip (BA'_T) located downstream of the radial component of the pitch axis (Y').

13. The aircraft propulsion unit (100) according to any one of claims 1 to 12, wherein, At least one pitch-variable stator blade (114) has an active factor between 50 and 200, preferably between 90 and 150.

14. An aircraft comprising an aviation propulsion unit (100) according to any one of claims 1 to 13.

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