Unducted aviation propulsion unit for aircraft

Abstract

The invention relates to a propulsion unit comprising: a housing (102); -a hub (104) mounted so as to pivot relative to the housing (102) about a main axis (X) extending in an upstream-downstream direction of the aircraft; -a propeller propeller (106) mounted on the hub (104) so as to be pivotable relative to the housing (102); and-a fixed rectifier (112) mounted on said casing (102) downstream of the propeller propeller (106) along the main axis (X), the fixed rectifier (112) extending around the main axis (X). At least one stator blade (114) of the fixed rectifier (112) has an activity factor between 50 and 200, preferably between 90 and 150.

Description

TECHNICAL FIELD

[0001] The present application relates to a non-ducted aerial propulsion unit for an aircraft, such as a turbomachine or turbojet engine or turboshaft engine, and to an aircraft comprising such an aerial propulsion unit. BACKGROUND

[0002] In the prior art, a non-ducted aerial propulsion unit for an aircraft is known, comprising: - a casing; - a hub pivotally mounted with respect to the casing about a main axis extending in an upstream-downstream direction of the aircraft; - a propeller mounted on the hub so as to be pivotable with respect to the casing; and - a fixed fairing mounted on the casing downstream of the propeller along the main axis, the fixed fairing extending about the main axis.

[0003] The propeller generally has rotor blades with variable pitch. The variable pitch system is known in English as Fan Pitch Actuation System (FPAS) and / or Pitch Change Mechanism (PCM). To achieve the target thrust, there can be multiple combinations of propeller rotational speed and rotor and stator blade pitch.

[0004] One of the challenges of such aerial propulsion units is the certification of the noise level during take-off and landing operations. The noise level emitted by an aircraft is subject to increasingly stringent international regulations aiming at limiting the acoustic footprint around the airport. Currently, the OACI (Organisation de l'Aviation Civile Internationale) Volume 1 Annex 16 Chapter 14 sets valid provisions giving maximum noise levels in EPNL (Effective Perceived Noise Level) depending on the flight phase and the aircraft weight.

[0005] The main noise sources of a non-ducted propulsion unit are as follows.

[0006] A first source of noise is the interaction noise between the vortex created at the tip of the rotor blades and the wake of the upstream propeller, which interacts with the leading edge of the downstream fairing. This noise source contributes to an increase in broadband noise, as the turbulence rate in the wake is generally very high at the rotor blade tip, and to an increase in tonal noise, which is related to the periodic nature of this vortex as the rotor blades rotate.

[0007] The second noise source is the inherent noise of the rotor blades and the stator blades. This inherent noise is related to the fixed loads on the rotor blades (source of tonal noise) and the development of the boundary layer on the rotor blades and the stator blades. In this way, when the turbulent boundary layer passes the trailing edge of the rotor blades and the stator blades, a broadband noise source is created. Increasing the chord of the rotor blades and / or the stator blades on the unducted aerial propulsion unit increases the surface area on which the boundary layer develops, thus increasing the broadband noise.

[0008] The aim of the application is to improve the acoustic performance of the fairing downstream of the propeller, without reducing the aerodynamic performance, while respecting certain mechanical constraints.

[0009] Furthermore, patent application FR 3 124 832 A1 describes an unducted aerial propulsion unit for an aircraft. SUMMARY

[0010] Thus, an unducted aerial propulsion unit for an aircraft is proposed, comprising: - a housing; - a hub pivotally mounted with respect to the housing about a main axis extending in an upstream-downstream direction of the aircraft; - a propeller mounted on the hub so as to be able to pivot with respect to the housing; and - a fixed fairing mounted on the housing downstream of the propeller along the main axis, the fixed fairing surrounding; characterized in that at least one stator blade of the fixed fairing has an activity factor of between 50 and 200, preferably between 90 and 150.

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

[0012] At least one stator blade of the fixed fairing has a variable pitch around a pitch axis, each variable-pitch stator blade having a pitch angle defined as the angle between, on the one hand, any plane perpendicular to the main axis and, on the other hand, a chord line connecting a leading edge of the stator blade to a trailing edge of the stator blade, the chord line being taken at 75% of the outer radius of the stator blade with respect to the main axis.

[0013] Optionally, for at least one value of the pitch angle in the interval [70°; 90°], the leading edge of at least one variable-pitch stator blade has a tip located downstream of the pitch axis.

[0014] Optionally, the propeller further comprises at least one variable-pitch rotor blade.

[0015] Optionally, the leading edge of at least one stator blade has a root, a mid-chord and a tip, for at least one value of the pitch angle in the interval [70°; 90°], the mid-chord, the root and the tip follow one another in this order along the main axis from upstream to downstream.

[0016] Optionally, 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 mid-chord located between 20% and 70% of the total blade height of the leading edge, preferably between 25% and 55% of the total blade height of the leading edge.

[0017] Optionally, the leading edge of at least one stator blade has a root, a mid-chord and a tip, for at least one value of the pitch angle in the interval [70°; 90°], the mid-chord, the root and the tip follow one another in this order along the main axis from upstream to downstream.

[0018] Optionally, the leading edge of at least one stator blade has a root, a mid-chord and a tip, for at least one value of the pitch angle in the interval [70°; 90°], the mid-chord, the root and the tip follow one another in this order along the main axis from upstream to downstream.

[0019] Optionally, the chord length of at least one stator blade is strictly decreasing from 50% to 100% of the total blade height of the leading edge and / or trailing edge, preferably from 40% to 100% of the total blade height of the leading edge and / or trailing edge.

[0020] Optionally, for at least one stator blade, the chord length at 95% of the total blade height of the leading edge or trailing edge is less than or equal to half the maximum chord length.

[0021] Optionally, for at least one stator blade, the chord length at 95% of the total blade height of the leading edge or trailing edge is less than or equal to half the maximum chord length.

[0022] Optionally, for at least one value of the pitch angle in the interval [70°; 90°], the sweepback angle of at least one stator blade is greater than 20°, preferably greater than 35° at a position above 80% of the upstream blade height.

[0023] Optionally, for at least one value of the pitch angle in the interval [70°; 90°], the sweepback angle of at least one stator blade is greater than 20°, preferably greater than 35° at a position above 80% of the upstream blade height.

[0024] Optionally, for at least one stator blade, for a value of the pitch angle between 70° and 90°, the axial distance along the main axis between the tip of the trailing edge and the root of the trailing edge is less than or equal to a coefficient E times the maximum chord length, with E being between 0.05 and 0.7, preferably between 0.25 and 0.6.

[0025] Optionally, for at least one stator blade, for at least one value of the pitch angle between 70° and 90°, the axial distance along the main axis between the tip of the leading edge and the root of the leading edge is less than or equal to a coefficient B times the maximum chord length, with B being between 0.5 and 1.2.

[0026] Optionally, for at least one stator blade, for at least one value of the pitch angle between 70° and 90°, the axial distance along the main axis between the tip of the trailing edge and the root of the trailing edge is less than or equal to a coefficient E times the maximum chord length, with E being between 0.05 and 0.7, preferably between 0.25 and 0.6.

[0027] Optionally, the trailing edge of at least one rotor blade and the leading edge of at least one stator blade are separated along the main axis by a distance taken as 95% of the total blade height of the leading edge or of the trailing edge of the stator blade, this distance being greater than 0.35*Re, preferably greater than 0.5*Re, for at least one value of the pitch angle of the rotor blade between 50° and 80° and for at least one value of the pitch angle of the stator blade between 70° and 90°, with Re being the outer radius of the propeller of the aeronautical propulsion unit.

[0028] Optionally, at least two stator blades have at least one different geometrical element among the outer radius, the maximum chord length, the activity factor, the sweep angle at 90% of the upstream blade height and the pitch angle.

[0029] An aircraft comprising an aeronautical propulsion unit according to the application is also proposed. BRIEF DESCRIPTION OF DRAWINGS

[0030] The application will be better understood by means of the following description given solely by way of example with reference to the appended drawings in which: - Figure 1 is a cross-sectional view of an aeronautical propulsion unit according to the application, - Figure 2 is Figure 1 is a side view of a rotor blade of the propeller of the aeronautical propulsion unit shown, - Figure 3 is a cross-sectional view of a rotor blade in Figure 2 - -Figure 4 is a similar view as Figure 2 showing the rotor blade's sweep angle, Figure 5 is Figure 2 a front view of the rotor blade in Figure 6 is Figure 1 a side view of the stator blade of the fixed fairing of the aerial propulsion unit of Figure 7 is Figure 6 a cross-sectional view of the stator blade in Figure 8 is a similar view as Figure 6 showing the stator blade's sweep angle, Figure 9 is Figure 6 a front view of the stator blade in Figure 10 is a similar view as Figure 6 showing the stator blade with a rounded tip, Figure 11 is a graph showing the chord of the stator blade evolving with the blade height, Figure 12 is a cross-sectional view of another aerial propulsion unit according to the invention, showing the spacing between the propeller and the fixed fairing, Figure 13 is Figure 6 a cross-sectional view of the stator blade in Figure 14 is a front view of the rotor blade's trailing edge and the stator blade's leading edge. DETAILED DESCRIPTION

[0031] In the following description, if a feature applies to at least one element, this feature can also apply to all such elements. Similarly, if a feature applies to at least one value in a range, this feature can also apply to all values in the range.

[0032] Referring to Figure 1 An aerial propulsion unit 100 to which the invention applies will now be described. The aerial propulsion unit 100 is for example a turbomachine, a turbojet or a turboshaft, since the type of aerial propulsion unit is not decisive here.

[0033] The aerial propulsion unit 100 is an unducted single fan (USF) designed to help propel an aircraft.

[0034] ​​​​​​​​​​The aerial propulsion unit 100 first comprises a casing 102 and a hub 104 mounted so as to pivot about a main axis X with respect to the casing 102.

[0035] In the following, the terms "upstream" and "downstream" will be used to designate the relative position of the elements of the aerial propulsion unit 100 along the main axis X in the direction of flow of the air flow PHI when the aerial vehicle is propelled by the aerial propulsion unit 100. For example, the aerial vehicle can be propelled by the aerial propulsion unit 100 in cruise mode at a flight Mach number greater than 0.7.

[0036] For example, the hub 104 is located upstream of the casing 102.

[0037] The aerial propulsion unit 100 also comprises a propeller 106, which is unducted and mounted on the hub 104 so as to be able to pivot about the main axis X with respect to the casing 102. The propeller 106 is designed to drive the air flow PHI downstream to propel the aerial vehicle in flight. To this end, the propeller 106 comprises rotor blades 108, for example 3 to 25, preferably 10 to 16, arranged for example in a single annular row about the main axis X. The rotor blades 108 can for example all be identical and angularly spaced at regular intervals about the main axis X.

[0038] For example, at least one rotor blade 108 has a variable pitch about a respective pitch axis Y. The pitch axis Y can pass through the main axis X or be slightly offset therefrom, for example by up to 10 cm, for example up to 5 cm, for example up to 2 cm, for example up to 1 cm. The pitch axis Y can be perpendicular to the main axis X, or have a slight inclination due to manufacturing tolerances or design intent. Thus, the pitch axis Y can for example be perpendicular 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 thus has a non-zero radial component. As illustrated, the axis Y can thus 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 a pitch angle C described below. In a preferred embodiment, all rotor blades 108 have a variable pitch.

[0039] The aerial propulsion unit 100 also comprises an engine 110 for driving the hub 104 and thus, via the hub 104, the propeller 106. For example, the engine 110 extends into the casing 102. The engine 110 is for example located downstream of the propeller 106. This arrangement is referred to as a "puller". The engine 110 is for example a gas generator, which generally comprises, from upstream to downstream, at least one compressor, at least one combustion chamber and at least one power turbine configured to drive the propeller 106.

[0040] The aerial propulsion unit 100 also comprises a fixed ducted fairing 112 mounted on the casing 102 downstream of the propeller 106. The fairing 112 forms a stator located in the casing 102, which extends around the main axis X but cannot rotate around the main axis X. The fairing 112 comprises stator blades 114 arranged for example in a single annular row around the main axis X. For example, 3 to 25 stator blades are provided, preferably 8 to 14 stator blades 114. Preferably, the number of stator blades 114 is different from the number of rotor blades 108 to reduce the noise of the aerial propulsion unit 100. In particular, the number of rotor blades 108 is greater than the number of stator blades 114. Indeed, if the number of rotor blades 108 and the number of stator blades 114 are equal, the rotor blades 108 will be followed by a wake which will interact simultaneously with the plurality of stator blades 114, which will increase the noise level. The stator blades 114 can for example all be identical or different and angularly spaced around the main axis X in a regular or uneven manner, so that at least two stator blades 114 have a different angular spacing around the main axis X. In particular, in the case of an aerial propulsion unit mounted in an aircraft, the stator blades 114: - can have an outer radius smaller than the outer radius of the rotor blades 108 to reduce the interaction noise of the tip vortex of the rotor blades 108 with the stator blades 114; this outer radius of the stator blades 114 can be different for each stator blade 114 in order to limit the interaction during the phases of incident flight such as landing and takeoff; - can have different geometric characteristics (pitch angle, thickness, chord, etc.) to optimize the operation of the stator blades according to the local nature of the flow; and - can have an uneven angular spacing around the main axis X, in particular in the vicinity of the mast or pylon; this allows to optimize the operation of the stator blades 114 according to their mounting in the aircraft.

[0041] The fairing 112 is designed to fair at least part of the air flow PHI passing through the propeller 106 to improve the performance of the aerial propulsion unit 100. More particularly, the aim of the fairing 112 is to absorb the flow swirl induced by the propeller 106 to improve the performance of the unducted configuration. However, the presence of the fairing induces a major source of noise resulting from the interaction with the wake of the propeller 106 (and also with the blade tip vortex when the truncation of the stator blades 114 is not sufficient). It is therefore important to reduce the noise produced by the fairing 112 and its interaction with the wake of the propeller 106 while maintaining good aerodynamic performance, since reducing noise emissions and fuel consumption are major challenges for unducted engine architectures.

[0042] 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.

[0043] 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'.

[0044] 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.

[0045] 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.

[0046] 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 BAis the height from the root BA P). The curvature of the leading edge BA is also regular, i.e. without discontinuity. The leading edge BA also comprises a belly BA V, in particular for at least one value of the pitch angle C within the interval [50°; 80°], the belly BA V being the most upstream point of the leading edge BA (minimum {x BA}).

[0047] Similarly, the trailing edge BF extends from a root BF P, which is the point of the trailing edge BF closest to the hub 104, to a tip BF T, which is the highest point of the trailing edge BF or the point on the rear portion of the rotor blade 108 having the largest radius with respect to the main axis X. For at least one value of the pitch angle C within the interval [50°; 80°], between the root BF P and the tip BF T, the trailing edge BF has a curvature of constant direction, i.e. without inflection point (in other words, along the trailing edge BF, as a function of the height h BF of the rotor blade 108, the axial position x BF of the trailing edge BF is not zero, i.e. BF , and the second derivative with respect to h BF is not zero, i.e. , and h BF is the height from the root BF P). The curvature of the trailing edge BF is also regular, i.e. without discontinuity. The trailing edge BF also comprises a belly BF V, in particular for at least one value of the pitch angle C within the interval [50°; 80°], the belly BF V being the most upstream point of the trailing edge BF (minimum {x 上游}).

[0048] 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 straight, connecting the tips BA T, 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 non-truncated, in which case the tips BA T and BF T would be merged.

[0049] In the following, the term "height" when applied in the context of the rotor blade 108 will mean the distance between two points along the radial component of the pitch axis Y, i.e. the distance between the orthogonal projections of these points on the radial component of the pitch axis Y.

[0050] Thus, an upstream blade height H 上游 for positioning on the leading edge BA can be defined. Thus, the upstream blade height H 上游 is the ratio between the height h BA from the root BA P and the total height H BA of the leading edge BA (between the root BA P and the tip BA T): H 上游 =hBA / H BA . Thus, the upstream blade height H 上游 may be expressed in percentage and varies between 0% (position at the root BA P) and 100% (position at the tip BA T). Similarly, a downstream blade height H 下游 may be defined, located on the trailing edge BF. Thus, the downstream blade height H 下游 is the height h BF from the root BF P to the trailing edge BF (between the root BF P and the tip BF T): H BF = h 下游 / H BF . Thus, the downstream blade height H BF may be expressed in percentage and varies between 0% (position at the root BF P) and 100% (position at the tip BF T). 下游

[0051] Furthermore, the propeller 106 has an outer radius Re, defined as equal to the height or distance between the main axis X and the point on the rotor blade 108 that is the most distant from the main axis X, in particular for at least one value of the pitch angle C within the interval [50°; 80°]. In the example shown, this most distant point is the tip BA T of the leading edge BA.

[0052] Figure 3 is the cross section of the rotor blade 108 at a certain height, perpendicular to the radial component of the pitch axis Y (also called aerodynamic profile).

[0053] It can be seen that the rotor blade 108 has a pressure side 302 and a suction side 304, respectively concave and convex, connected to each other by the leading edge BA and the trailing edge BF. Thus, the leading edge BA separates the pressure side 302 from the suction side 304 in the upstream portion of the rotor blade 108, while the trailing edge BF separates the pressure side 302 from the suction side 304 in the rear portion of the rotor blade 108.

[0054] The leading edge BA is for example a point of the cross section in the upstream portion of the rotor blade 108, with a locally minimum radius of curvature. Similarly, the trailing edge BF is for example a point of the cross section in the downstream portion of the rotor blade, presenting a locally minimum value in the radius of curvature, when this downstream portion is rounded. In order 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 this truncated portion.

[0055] ​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.

[0056] 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.

[0057] 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%.

[0058] 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 .

[0059] 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.

[0060] 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}).

[0061] 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}).

[0062] The stator blade 114 can also be truncated, as in the example shown, i.e. there is a truncated section 602, for example straight, connecting the tips BA'_T, BF'_T. In this case, there is a curvature discontinuity at the tip BA'_T between the leading edge BA' and the truncated section 602, and also at the tip BF'_T between the truncated section 602 and the trailing edge BF'. Alternatively, the stator blade can be non-truncated, in which case the tips BA'_T, BF'_T would be merged.

[0063] In the following, the term "height" when applied in the context of the stator blade 114 will mean the distance between two points along the radial component of the pitch axis Y', i.e. the distance between the orthogonal projections of these points on the radial component of the pitch axis Y'.

[0064] Therefore, an upstream blade height H 上游 can be defined for the position on the leading edge BA'. The upstream blade height H 上游 is therefore a ratio between the height h BA from the root BA'_P and the total height H BA of the leading edge BA' (between the root BA'_P and the tip BA'_T): H 上游 = h BA / H BA . The upstream blade height H 上游 may therefore be expressed in percentage and varies between 0% (position at the root BA'_P) and 100% (position at the tip BA'_T). Similarly, a downstream blade height H 下游 can be defined for the position on the trailing edge BF'. The downstream blade height H 下游 is therefore a ratio between the height h BF from the root BF'_P and the total height H BF of the trailing edge BF' (between the root BF'_P and the tip BF'_T): H 下游 = h BF / H BF . The downstream blade height H 下游 may therefore be expressed in percentage and varies between 0% (position at the root BF'_P) and 100% (position at the tip BF'_T).

[0065] Moreover, each variable pitch stator blade 114 of the rectifier 112 has an outer radius Re', defined as equal to the height or distance between the main axis X and the point on the stator blade 114 that is farthest from the main axis X, particularly for at least one value of the pitch angle C' within the interval [70°; 90°]. In the example shown, this farthest point is the tip BF'_T of the trailing edge BF'. Alternatively, this farthest point can be the tip BA'_T of the leading edge BA'.

[0066] Each variable pitch stator blade 114 also has an inner radius Ri' at the leading edge BA' BA BA which is the distance between the main axis X and the root BA'_P of the leading edge BA, and an inner radius Ri' at the trailing edge BF' BF BF which is the distance between the main axis X and the root BF'_P of the trailing edge BF'.

[0067] Figure 7 and Figure 13 Cross sections of the stator blade 114 at different heights are shown, perpendicular to the radial component of the pitch axis Y'.

[0068] It can be seen that the stator blade 114 has a pressure side 702 and a suction side 704, respectively concave and convex, which are connected to each other by the leading edge BA' and the trailing edge BF'. Thus, the leading edge BA' separates the pressure side 702 from the suction side 704 in the upstream portion of the stator blade 114, while the trailing edge BF' separates the pressure side 702 from the suction side 704 in the rear portion of the stator blade 114.

[0069] The leading edge BA' is for example the point of the cross section in the upstream portion of the stator blade 114 that has a locally minimum radius of curvature. Similarly, the trailing edge BF' is for example the point of the cross section in the downstream portion of the stator blade that presents a locally minimum value in the radius of curvature, when this downstream portion is rounded. In order 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 this truncated section.

[0070] When the leading edge BA' and the trailing edge BF' are present in the cross section under consideration (i.e. for example, below the truncated section 602 in the example shown), the leading edge BA' and the trailing edge BF' can be connected by a chord line 706, the orientation of which varies according to the height under consideration. The leading edge BA' and the trailing edge BF' are separated on the chord line 706 by a distance called chord length L', which can vary according to the height under consideration.

[0071] ​​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.

[0072] 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%.

[0073] 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' .

[0074] The shape of the stator blades 114 of the rectifier 112 is designed to reduce noise pollution while ensuring good aerodynamic performance.

[0075] Therefore, for at least one value of the pitch angle C' within the interval [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 is moved away from the propeller 106, which reduces the noise over a wide range of pitch angles C'. The positioning of the free end of the stator blade 114 downstream enables to reduce the interaction noise between the wake of the propeller 106 and the leading edge BA' of the stator blade, by increasing the distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114, so that the noise sources along the leading edge BA' are decorrelated and the wake of the propeller 106 is dissipated.

[0076] Preferably, in order to facilitate the positioning of the free end of the stator blade 114 downstream, 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 one another 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, it is possible to increase the sweep angle F' at the upper portion of the stator blade 114, in particular near the free end of the stator blade 114. When the pitch axis Y' is inclined or not perpendicular to the main axis X, x Y' corresponds to the axial position of the pitch axis Y' of the stator blade at the casing 102. Moreover, 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 tip BA'_T preferably follow one another in this order from upstream to downstream along the main axis X.

[0077] Even more preferably, in order to facilitate the positioning of the free end of the stator blade 114 downstream, the belly BA'_V is located between 20% and 70% of the total blade height H' BA , preferably between 30% and 60% of 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.

[0078] 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.

[0079] 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 ).

[0080] 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.

[0081] 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.

[0082] 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'}.

[0083] 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'}.

[0084] 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.

[0085] 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even more preferably greater than 50°. This reduces the component of flow velocity normal to the trace of the leading edge BA' of the cross section, thus reducing interaction noise.

[0086] Even more preferably, in order to facilitate the positioning of the free end of the stator blade 114 downstream, 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, itself 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 .

[0087] With reference to Figure 10 , a non-truncated stator blade 114 is shown, having a rounded tip.

[0088] With reference to Figure 11 , preferably, the chord length L' is strictly decreasing from the upstream blade height H' 上游 and / or the downstream blade height H' 下游 of 40% to 100%, preferably from 50% to 100% (thus in Figure 11 , the reference H' can denote H' 上游 or H' 下游 ). This aspect makes it possible, on the one hand, to increase the distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114, and on the other hand, to increase the sweep angle F' towards the free end of the stator blade 114, in particular when there are integrated or mechanical constraints that prevent the trailing edge BF' of the stator blade 114 from being modified or offset. Indeed, offsetting the trailing edge BF' to the upper portion of the blade (for example on the tip cross section 602) can increase the moment of the aerodynamic forces around the pitch axis Y' and thus have a significant impact on the mechanical dimensions of the pitch variation system. A parameter providing a first estimate of the chord length distribution along the span of the stator blade 114 is its activity factor (AF), defined as follows: where Ri' is the inner radius Ri BA of the stator blade 114 at the leading edge BA' or the inner radius Ri BF of the stator blade 114 at the trailing edge BF' (see Figure 6 ); Re' is the outer radius Re BA of the stator blade 114 at the leading edge BA' or the outer radius Re BF ; denoting the radial distance from the main axis X, other than the outer radius Re'; L'(ξ) denotes the chord length at said radial distance the chord length between the leading edge BA' and the 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'.

[0089] The activity factor of the stator blade 114 is preferably between 50 and 200, more preferably between 90 and 150. With values such as these, it is possible to ensure 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, as well as to reduce the chord length L' in the upper portion of the stator blade 114, which increases the sweep angle in the upper portion of the blade and thus reduces the noise.

[0090] Even more preferably, the chord length L' at 95% of the upstream blade height H' 上游 and / or of the downstream blade height H' 下游 is less than or equal to half of the maximum chord length L'max{L'} of the stator blade 114: L'(H' = 95%) < 0.5 * max{L'}, with H' = H' 上游 or H' 下游 This makes it possible to increase the sweep angle F' with respect to the position in the middle of the span and close to the blade belly, which is beneficial from an aerodynamic acoustic point of view, as well as to reduce the mass of the blade in the upper portion, which is beneficial from a mechanical point of view, as well as to reduce the inertia in the event of a blade tip loss (for example, in the event of bird ingestion) or a blade loss event (Fan Blade Out, FBO).

[0091] Even more preferably, the chord length L' at 95% of the upstream blade height H' 上游 and / or of the downstream blade height H' 下游 is less than or equal to half of the chord L' at 10% of the upstream height H' 上游 and / or of the downstream height H' 下游 : L'(H' = 95%) < 0.5 * L'(H' = 10%), with H' = H' 上游 or H' 下游 This reduces the inertia in the event of a blade tip loss (for example, in the event of bird ingestion) or in the event of a blade loss.

[0092] With reference to Figure 12 , the positioning of the free end of the stator blade 114 downstream makes it possible to maintain a large distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114, thus reducing the noise of the aeronautical propulsion unit 100. In particular, for at least one value of the pitch angle C in the interval [50°; 80°] and at least one value of the pitch angle C' in the interval [70°; 90°], the distance between the trailing edge BF of the rotor blade 108 and the leading edge BA' of the stator blade 114 is greater than 10% of the chord L' at 95% of the upstream blade height H' 上游 and / or of the downstream blade height H'下游 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, at 95% of the outer radius Re', is preferably greater than 0.35 times the Reynolds number (Re) of the propeller 106, even more preferably greater than 0.5 times the Reynolds number.

[0093] Figure 14 The projection y Figure 14 of the trailing edge BF of the rotor blade 108 on a plane perpendicular to the main axis X (plane of the sheet) BF and the projection y BA' of the leading edge BA' of the stator blade 114 on the same plane are shown.

[0094] It can be seen that the leading edge BA' of at least one stator blade 114 has a dihedral angle D BA' for at least one value of the pitch angle C' in the interval [70°; 90°], the dihedral angle D BA' has an absolute value greater than 1°, preferably 3°, and even more preferably 10°.

[0095] Preferably, for at least one value of the pitch angle C' in the interval [70°; 90°], the dihedral angle D BA' at 95% of the outer radius Re' has an absolute value at least 1° greater than the dihedral angle D BA' of the leading edge BA' of the stator blade 114 at 50% of the outer radius Re', preferably at least 3°, or even more preferably at least 10°.

[0096] Even more preferably, for at least one value of the pitch angle C' in the interval [70°; 90°], the dihedral angle D BA' on the leading edge BA' of the stator blade 114 is strictly monotonic for radial positions greater than 90% of the outer radius Re'.

[0097] Even more preferably, for at least one value of the pitch angle C' in the interval [70°; 90°], the projection y BA' of the leading edge BA' of the stator blade 114 on a plane perpendicular to the main axis X has at least one local maximum and / or minimum.

[0098] Even more preferably, for at least one value of the pitch angle C' in the interval [70°; 90°], the projection y BA' of the leading edge BA' of the stator blade 114 on a plane perpendicular to the main axis X has at least one inflection point PI.

[0099] In addition, the projection y BF of the trailing edge BF of the rotor blade 108 on a plane perpendicular to the main axis X (plane of the sheet) 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.

[0100] 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 |

[0101] 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%.

[0102] 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.

[0103] 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 phase shift is relatively large at the blade tip, which is useful for reducing the sound level by increasing the phase shift of the noise source.

[0104] 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' .

[0105] 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.

[0106] 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 wake of the propeller 106 (generated at the trailing edge BF of the rotor blades 108) and the leading edge BA' of the stator blades 114 downstream. In fact, the deviation Ay BA' The greater the deviation Ay, the greater the dihedral angle on the blades, in particular at the blade tips.

[0107] In any case, it should be noted that the present application is not limited to the above-described embodiments. In fact, various modifications can be made to the above-described embodiments, according to the teachings just disclosed, for the person skilled in the art.

[0108] In the foregoing detailed description of the application, the terms used are not to be interpreted as limiting the application to the embodiments disclosed in the specification, but as including all equivalents the person skilled in the art is able to obtain by applying their common knowledge 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) is mounted on the housing (102) downstream of the propeller (106) along the main axis (X) and the fixed rectifier (112) extends about the main axis (X); The fixed rectifier (112) is characterized in that at least one stator blade (114) has an activity factor between 50 and 200, preferably between 90 and 150.

2. The aviation propulsion unit (100) according to claim 1, wherein, At least one stator blade (114) of the fixed rectifier (112) has a variable pitch about a pitch axis (Y'), and each variable pitch stator blade (114) has 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 chord (706) being obtained at 75% of the outer radius (Re') of the stator blade (114) relative to the main axis (X).

3. The aviation propulsion unit (100) according to claim 2, wherein, For at least one value of the pitch angle (C') within the range [70°; 90°], the leading edge (BA') of at least one pitch-variable stator blade (114) has a tip (BA'_T) located downstream of the pitch axis (Y').

4. The aviation propulsion unit (100) according to any one of claims 1 to 3, wherein, The propeller (106) includes at least one rotor blade (108) with a variable pitch.

5. The aviation propulsion unit (100) according to any one of claims 1 to 4, wherein, At least one stator blade (114) has a leading edge (BA') having a root (BA'_P), a belly (BA'_V), and a tip (BA'_T), the belly (BA'_V), the root (BA'_P), and the tip (BA'_T) following each other in this order from upstream to downstream along the main axis (X) for at least one value of the pitch angle (C') in the range [70°; 90°].

6. The aviation propulsion unit (100) according to any one of claims 1 to 5, 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 total blade height (H') located at the leading edge (BA'). BA The ventral part (BA'_V) is located between 20% and 70% of the total blade height at the leading edge, preferably between 25% and 55% of the total blade height.

7. The aviation propulsion unit (100) according to any one of claims 1 to 6, wherein, At least one stator blade (114) has a belly (BA'_V) at the leading edge (BA'), the height and / or radius of the belly from the main axis (X) being smaller than the height and / or radius of the belly (BF'_V) from the main axis (X) at the trailing edge (BF').

8. The aviation propulsion unit (100) according to any one of claims 1 to 7, wherein, The chord length (L') of the cross section of at least one stator blade (114) at the tip (BA'_T) closest to the leading edge (BA') is less than the chord length (L') of the cross section at the root (BA'_P) closest to the leading edge (BA'), and the chord length of the cross section at the root closest to the leading edge is itself less than the chord length (L') at the belly (BA'_V) of the leading edge (BA').

9. The aviation propulsion unit (100) according to any one of claims 1 to 8, wherein, The chord length (L') of at least one stator blade (114) is preferably from the total blade height (H') of the leading edge (BA') and / or trailing edge (BF'). BA H' BF Strictly decreasing from 50% to 100% of the total blade height, preferably from 40% to 100% of the total blade height of the leading and / or trailing edges.

10. The aviation propulsion unit (100) according to any one of claims 1 to 9, wherein, For at least one stator blade (114), the total blade height (H') at the leading edge (BA') or trailing edge (BF') BA The chord length (L') at 95% of the maximum chord length is less than or equal to half of the maximum chord length (L').

11. The aircraft propulsion unit (100) according to any one of claims 1 to 10, wherein, For at least one stator blade (114), the total blade height (H') at the leading edge (BA') BA ) or the total blade height at the trailing edge (H') BF The chord length (L') at 95% of the leading edge (BA') is less than or equal to the total blade height (H') at the leading edge (BA'). BA ) or the total blade height (H') at the trailing edge BF Half of the chord length (L') at 10% of the chord length.

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 sweep angle (F') of at least one stator blade (114) at the upstream blade height (H') 上游 More than 80% of the positions are greater than 20°, preferably greater than 35°.

13. The aircraft propulsion unit (100) according to any one of claims 1 to 12, wherein, For at least one value of the pitch angle (C') within the interval [70°; 90°], the sweep angle (F') of at least one stator blade (114) at the upstream blade height (H') 上游 More than 90% of the position is greater than 45°, and / or at the upstream blade height (H') 上游 More than 95% of the positions are greater than 50°.

14. The aircraft propulsion unit (100) according to any one of claims 1 to 13, wherein, For at least one stator blade (114), for a pitch angle (C') between 70° and 90°, the axial distance along the main axis (X) between the tip (BF'_T) of the trailing edge (BF') and the belly (BA'_V) of the leading edge (BA') is greater than or equal to a coefficient K multiplied by the maximum chord length (L'), wherein K is between 1 and 2, preferably between 1.2 and 1.

6.

15. The aircraft propulsion unit (100) according to any one of claims 1 to 14, wherein, For at least one stator blade (114), for at least one value of the pitch angle (C') between 70° and 90°, the axial distance along the main axis (X) between the tip (BA'_T) and the belly (BA'_V) of the leading edge (BA') is less than or equal to a coefficient B multiplied by the maximum chord length (L'), wherein B is between 0.5 and 1.

2.

16. The aircraft propulsion unit (100) according to any one of claims 1 to 15, wherein, For at least one stator blade (114), for at least one value of the pitch angle (C') between 70° and 90°, the axial distance along the main axis (X) between the tip (BF'_T) and root (BF'_P) of the trailing edge (BF') is less than or equal to a coefficient E multiplied by the maximum chord length (L'), wherein E is between 0.05 and 0.7, preferably between 0.25 and 0.

6.

17. The aircraft propulsion unit (100) according to any one of claims 1 to 16, wherein, The trailing edge (BF) of at least one rotor blade (108) and the leading edge (BA') of at least one stator blade (114) are separated along the main axis (X) by a distance (s), which is taken as the total blade height (H') of the leading edge (BA') of the stator blade (114). BA ) or the total blade height at the trailing edge (H') BF 95% of the distance between 0.35*Re, preferably greater than 0.5*Re, for at least one value of the pitch angle (C) of the rotor blade (108) between 50° and 80° and at least one value of the pitch angle (C') of the stator blade (114) between 70° and 90°.

18. The aircraft propulsion unit (100) according to any one of claims 1 to 17, wherein, At least two stator blades (114) are at least equal to the outer radius (Re') of the stator blade (114), the maximum chord length (L'), the activity factor (FA), and the upstream blade height (H'). 上游 The sweep angle (F') at 90% of the pitch angle (C') has at least one different geometric element.

19. An aircraft comprising an aviation propulsion unit (100) according to any one of claims 1 to 18.

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