Aircraft propeller

Abstract

An aeronautical thruster (10) comprising a hub (12) comprising a radially external face, a first platform (20) and a second platform (20) arranged in a housing (13) of the hub (12) and comprising a radially external face (21) delimited by a peripheral edge (22), a first stator blade (16) secured to the first platform (20), a second stator blade (16) secured to the second platform (20), the aeronautical thruster (10) having a first configuration in which a pitch angle of the first stator blade (16) is different from a pitch angle of the second stator blade (16) and in which the edges (22) of the first platform (20) and of the second platform (20) are each radially flush with the radially external face (15) of the hub (12). Abstract figure: Figure 7

Description

Title of the invention: Aeronautical propeller Technical field

[0001] The present description relates to the field of aeronautical propellers. Prior art

[0002] Reference will only be made hereinafter to the case of turbomachines, since the type(s) of engine included in the aeronautical propeller is not decisive here.

[0003] A turbomachine with an “unducted” fan (or turboprop type "Propfan" or "Open Fan" or "Open rotor" or "Counter-Rotating Open Rotor") is a type of turbomachine in which the fan (or propeller) extends outside the engine casing (or nacelle), unlike conventional turbomachines (of the "Turbofan" type) in which the fan is ducted. An example of such a turbomachine is shown in [Fig.l]. The turbomachine 10 comprises a hub 12, defining the engine casing, and on which is mounted an annular row of unducted upstream blades 14 and an annular row of unducted downstream blades 16 which are spaced from each other along a longitudinal axis X of the turbomachine 10. The annular row of upstream blades 14 and the annular row of downstream blades 16 respectively define an upstream propeller and a downstream propeller or stator.

[0004] In the remainder of the description, unless otherwise specified, the orientation qualifiers, such as “longitudinal”, “radial” or “circumferential”, are defined with reference to the longitudinal axis X of the turbomachine 10. The relative qualifiers “upstream” and “downstream” are defined with respect to each other with reference to the flow of gases in the turbomachine 10 along the longitudinal axis X.

[0005] The turbomachine 10 comprises, from upstream to downstream inside the engine casing, one (or more) compressor(s), at least one combustion chamber, one (or more) turbine(s) and at least one exhaust nozzle.

[0006] Among these unducted fan turbomachines, there are known “Unducted Single (or Stator) Fan” (USF) type turbomachines in each of which, as illustrated in [Fig.l], the unducted upstream annular row of blades 14 is mounted to rotate about the longitudinal axis X and the unducted downstream annular row of blades 16 is fixed. In other words, the upstream annular row of blades 14 is of the rotor type and the downstream annular row of blades 16 is of the stator type. The direction of rotation of the upstream rotor blades 14 is not decisive. The downstream annular row of stator blades 16 may be centered on an axis coinciding or not with the longitudinal axis X. The upstream rotor blades 14 and the downstream stator blades 16 may have variable pitch. As illustrated in [Fig.l], the annular row of stator blades downstream 16 is centered on the longitudinal axis X. Such a USF type configuration makes it possible to utilize, through the downstream propeller, the turning energy of the air flow coming from the upstream propeller. The efficiency of the turbomachine 10 is thus improved, in particular compared to a conventional turbomachine comprising a single rotating propeller. The unducted upstream rotor blades 16 are rotated around the longitudinal axis X by the turbine(s) 6 which in turn drive(s) the compressor(s) 2. The turbomachine 10 generally comprises a speed reduction box ("gearbox" in English) in order to decouple the rotational speed of the turbines 6 from the rotational speed of the upstream propeller.Furthermore, one of the advantages of a USF type turbomachine compared to a “Counter-Rotating Open Rotor” type turbomachine is to reduce the tonal noise emitted by the turbomachine due to the fact that the non-ducted downstream stator blades 16 are not driven in rotation around the longitudinal axis X.

[0007] The turbomachine 10 may have a so-called “pusher” configuration in which the upstream annular row of rotor blades 14 and the downstream annular row of stator blades 16 are located at a downstream end portion of the turbomachine 10 (configuration shown in [Fig. 1]), or the turbomachine 10 may have a so-called “puller” configuration in which the upstream annular row of rotor blades 14 and the downstream annular row of stator blades 16 are located at an upstream end portion of the turbomachine 10.

[0008] In the puller configuration, the upstream annular row of rotor blades 14 and the downstream annular row of stator blades 16 may surround a section of the compressor(s) 2 of the turbomachine or of the speed reduction box. In the pusher configuration, the upstream annular row of blades 14 and the downstream annular row of stator blades 14 may surround a section of the turbine(s) 6 of the turbomachine 10.

[0009] The absence of fairing leads to an increase in the noise level emitted by the turbomachine 10 if the row of rotor blades and the row of stator blades are not correctly matched. Indeed, the noise generated by the annular rows of unfairly shrouded upstream rotor blades 14 and downstream stator blades 16 propagates in a free field. A main cause of the noise emitted is linked on the one hand to the interaction of the wake of the upstream rotor blades 14 on the downstream stator blades 16, and on the other hand, to vortex structures generated in the air flow at the free radially external ends of the upstream rotor blades 14 which impact the downstream stator blades 16.

[0010] However, too high a noise level is detrimental to the comfort of the passengers of the aircraft on which the turbomachine is installed. In addition, current standards impose a maximum noise threshold, particularly in areas close to the ground, that is, during the takeoff and landing phases.

[0011] Furthermore, when the upstream airflow perceived by the turbomachine 10 is not parallel to the longitudinal axis X (in particular during the landing and takeoff phases), the forces generated on each upstream rotor blade 14 vary according to the position around the longitudinal axis X of the upstream rotor blade 14 during its rotation around the longitudinal axis X. Thus the directivity of the acoustic radiation in the far field is not axisymmetric. Also, the incidence of the airflow perceived by the turbomachine 10 is modified by the upstream propeller in a heterogeneous manner around the longitudinal axis X.Consequently, the aerodynamic load applied to each of the downstream stator blades 16 differs depending on the position around the longitudinal axis X of the downstream stator blade 16, which can lead to thrust provided by the downstream propeller or stator which is not satisfactory during the incidence operating phases of the turbomachine 10, in particular during the landing and takeoff phases.

[0012] Furthermore, in operation, the presence of aircraft structural elements (mast, fuselage, wing, slat, flaps, etc.) located near the downstream propeller or stator can modify the airflow conditions (pressure, longitudinal component of the flow speed, etc.) locally around the longitudinal axis X, at the level of the annular row of downstream stator blades 16. However, a heterogeneous airflow around the longitudinal axis X at the level of the downstream propeller or stator also has the disadvantage of causing an aerodynamic load applied to each of the downstream stator blades 16 which differs according to the position around the longitudinal axis X of the downstream stator blade 16.

[0013] In order to overcome these drawbacks, it has been proposed in documents FR 3 133 367 and FR 3 133 368 to adjust the pitch angle of each downstream stator blade to take into account the local aerodynamic, acoustic and installation constraints of the aeronautical thruster. Each downstream stator blade can thus be rotated around a respective pitch axis to change the angle of incidence of the air flow on the downstream stator blade.The rotational adjustment of each downstream stator blade around the respective pitch axis can be carried out as a function of an operating phase of the aeronautical propeller (for example cruise phase, landing phase or take-off phase), and / or as a function of the airflow conditions taken locally at the level of the downstream stator blade, these being able to depend, according to the position of the downstream stator blade around the longitudinal axis, on the wake of the upstream rotor blades and / or on the presence of structural elements of an aircraft on which the aeronautical propeller is mounted (mast, fuselage, wing, slat, flaps, etc.).

[0014] To do this, as seen in [Fig.2], each downstream stator blade 16 is mounted at its lower end on a platform 20 which forms a surface air flow at the lower exterior of the downstream stator blade. However, the radially outer surface of the hub is generally rounded around the longitudinal axis X so that when the pitch of one of the downstream stator blades 16 is changed, rising steps 100a and falling steps are formed between the corresponding platform 20 of the downstream stator blade 16 and the hub 12. Such rising steps 100a and falling steps 100b are shown in Figures 3 and 4. These rising or falling steps 100a; 100b generate aerodynamic losses, which reduces the performance of the aeronautical propeller. Summary

[0015] There is provided a longitudinal axis aeronautical thruster, the aeronautical thruster comprising: - a hub comprising a radially external face, - an annular row of unducted stator blades which comprises at least a first stator blade and a second stator blade, - a plurality of platforms which comprise at least a first platform and a second platform, each platform being arranged in a corresponding housing of the hub and comprising a radially external face delimited by a peripheral edge, — the first stator blade being secured to the first platform, the first platform being centered and rotatable around a first axis of alignment of the first stator blade relative to the hub, — the second stator blade being secured to the second platform, the second platform being centered and rotatable around a second axis of alignment of the second stator blade relative to the hub, and the aeronautical thruster having at least a first configuration in which a pitch angle of the first stator blade is different from a pitch angle of the second stator blade and in which the edge of the first platform and the edge of the second platform are each radially flush over the entire periphery with the radially external face of the hub.

[0016] Each platform can be received by complementary shapes in the corresponding housing of the hub. The peripheral edge of each platform can be circular around the alignment axis of the corresponding stator blade.

[0017] Each stator blade may extend radially between a root and a head. At least one of the platforms, preferably each of the platforms, may comprise a first part and a second part which are structurally independent and between which the root of the corresponding stator blade is disposed, or even clamped.

[0018] The first part and the second part of each platform may have a half-disc shape.

[0019] The root of each stator blade may comprise a leading edge upstream and a trailing edge downstream between which extend a pressure face and an extrados face. The first part of each platform may comprise an internal face complementary to the pressure face and opposite, or even resting on, the pressure face of the corresponding stator blade and the second part of each platform may comprise an internal face complementary to the extrados face and opposite, or even resting on, the extrados face of the corresponding stator blade.

[0020] The internal face of the first part and the internal face of the second part of each platform may each have a recess receiving by complementary shape a part of the foot of the corresponding stator blade.

[0021] The internal face of the first part and the internal face of the second part of each platform may be opposite each other, or even resting on each other, upstream and / or downstream of the root of the corresponding stator blade.

[0022] The pitch angle of each of the stator blades in the first configuration of the aeronautical propeller can be between 65° and 95°, preferably between 73° and 87°.

[0023] A peripheral clearance may be formed between each platform and the corresponding housing of the hub radially relative to the setting axis of the corresponding stator blade, the peripheral clearance being less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm.

[0024] A first internal clearance may be formed between the first part of each platform and the root of the corresponding stator blade and / or a second internal clearance may be formed between the second part of each platform and the root of the corresponding stator blade, the first internal clearance and / or the second internal clearance being less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm. Brief description of the drawings

[0025] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0026] [Fig-1] is a partial schematic sectional view of a fan turbomachine unfaired according to the prior art.

[0027] [Fig.2] is a schematic sectional view of a stator blade and a corresponding platform of the turbomachine of [Fig.l], in a first pitch configuration.

[0028] [Fig.3] is a schematic sectional view of the stator and platform blade of [Fig.2], in a second wedging configuration.

[0029] [Fig.4] is a schematic top view of the stator and platform blade of [Fig.3] which illustrates descending and ascending steps formed between the platform and the hub.

[0030] [Fig.5] is a partial schematic sectional view of an aeronautical propeller according to the present description.

[0031] [Fig.6] includes figures 6a to 6c which illustrate a configuration of the timing of the aeronautical propeller according to several variants.

[0032] [Fig.7] is a schematic sectional view of a stator blade and a corresponding platform of the aeronautical propeller of [Fig.5].

[0033] [Fig.8] a schematic view of the downstream stator blade [Fig.7] in section plane VIII-VIII.

[0034] [Fig.9] is a schematic top view illustrating a first variant embodiment of the platform of [Fig.7].

[0035] [Fig. 10] is a schematic top view illustrating a second variant embodiment of the platform of [Fig.7].

[0036] [Fig. 11] is a schematic top view illustrating a third variant embodiment of the platform of [Fig.7].

[0037] [Fig. 12] is a schematic top view illustrating parametric features of the platform of [Fig.7]. Description of the embodiments

[0038] There is now described, with reference to figures 5 to 12, an aeronautical propeller 10 with longitudinal axis X visible as a whole in [Fig.5].

[0039] The aeronautical propeller 10 comprises: - a hub 12 comprising a radially external face, - an annular row of non-ducted stator blades 16 which comprises at least a first stator blade 16a and a second stator blade 16b, - a plurality of platforms 20 which comprise at least a first platform 20a and a second platform 20b, each platform 20 being arranged in a corresponding housing 13 of the hub 12 and comprising a radially external face 21 delimited by a peripheral edge 22.

[0040] The first stator blade 16a is secured to the first platform 20a. The first platform 20a is centered and rotatable about a first setting axis AC of the first stator blade 16a relative to the hub 12. Similarly, the second stator blade 16b is secured to the second platform 20b. The second platform 20b is centered and rotatable about a second setting axis AC of the second stator blade 16b relative to the hub 12.

[0041] Remarkably in Figure 6a, the aeronautical propeller 10 has at at least a first configuration in which a pitch angle y of the first stator blade 16a is different from a pitch angle y of the second stator blade 16b and in which the edge 22 of the first platform 20a and the edge 22 of the second platform 20b are each radially flush over the entire periphery with the radially external face 15 of the hub 12. According to an equivalent formulation of the term "flush", in the first configuration of the aeronautical thruster 10, the edge 22 of the first platform 20a and the edge 22 of the second platform 20b are each radially edge-to-edge with an edge of the corresponding housing 13 of the hub 12. The first and second platforms may be geometrically different.

[0042] In the first configuration of the aeronautical propeller 10, an optimal aerodynamic profile is obtained due to the continuity of surfaces between the radially external face 15 of the hub 12 and the radially external faces of the first and second platforms 20a, 20b, which makes it possible to limit, or even avoid, reductions in performance due to aerodynamic losses associated with possible upward or downward steps.

[0043] The pitch angle y of each of the stator blades 16 in the first configuration of the aeronautical propeller 10 may be between 65° and 95°, preferably between 73° and 87°. Such ranges of values ​​make it possible to obtain a pitch configuration for different flight points.

[0044] Generally, each stator blade 16 may be rigidly connected to a corresponding platform 20 among the plurality of platforms 20. Each platform 20 may be centered and movable in rotation about a setting axis AC of the corresponding stator blade 16. Each platform 20 may be arranged in a corresponding housing 13 of the hub 12. The hub 12 may therefore comprise a plurality of housings 13. In particular, the hub 12 may comprise at least a first housing 13 receiving the first platform 20a and a second housing 13 receiving the second platform 20b. The radially external face 21 of one or more of the platforms 20, or even each of the platforms 20, may have a rounded shape about the longitudinal axis X.

[0045] The plurality of platforms 20 and the plurality of housings 13 may be distributed around the longitudinal axis X, for example in a regular manner. In other words, the aeronautical thruster 10 may comprise an annular row of platforms 20 and the radially external face 15 of the hub 12 may have an annular row of housings 13.

[0046] Each stator blade 16 may be integral with the corresponding platform 20 as seen in [Fig. 11]. Alternatively, each stator blade 16 may be rigidly connected to the corresponding platform 20, by any fixing means known, for example by bolting.

[0047] According to a particular example shown in Figure 6b, the aeronautical thruster 10 may comprise at least a third stator blade 16c and a fourth stator blade 16d that are not ducted. The aeronautical thruster 10 may comprise a third platform 20c and a fourth platform 20d. The third stator blade 16c may be secured to the third platform 20c, the third platform 20 being centered and rotatable about a third pitch axis AC of the third stator blade 16c relative to the hub 12. The fourth stator blade 16d may be secured to the fourth platform 20d, the fourth platform 20d being centered and rotatable about a fourth pitch axis AC of the fourth stator blade 16d relative to the hub 12.In the first configuration of the aeronautical thruster 10, pitch angles of the first, second, third and fourth stator blades 16a; 16b; 16c; 16d may each be different from each other, and the edges 22 of the first, second, third and fourth platforms 20a; 20b; 20c; 20d may each be radially flush over the entire periphery with the radially external face 15 of the hub 12. Each of the first, second, third and fourth platforms may be geometrically different.

[0048] Alternatively, according to a variant not shown of the first configuration of the aeronautical thruster 10, the first stator blade 16a and the third stator blade 16c may have an identical first pitch angle y and the second stator blade 16b and the fourth stator blade 16d may have an identical second pitch angle y which is different from the first pitch angle y. In this variant, the edges 22 of the first, second, third and fourth platforms 20a; 20b; 20c; 20d may also each be radially flush over the entire periphery with the radially external face 15 of the hub 12. The first and third platforms may be different from the second and fourth platforms.

[0049] According to another variant not shown of the first configuration of the aeronautical thruster 10, the first stator blade 16a, the third stator blade 16c and the fourth stator blade 16d may have an identical first pitch angle y and the second stator blade 16b may have a second pitch angle y which is different from the first pitch angle y. In this variant, the edges 22 of the first, second, third and fourth platforms 20a; 20b; 20c; 20d may also each be radially flush over the entire periphery with the radially external face 15 of the hub 12. The first, second and third platforms may be different from the fourth platform.

[0050] According to another variant of the first configuration of the aeronautical propeller 10 shown in FIG. 6c, each stator blade 16 may have a respective pitch angle y which differs from a pitch angle y of one or more other of the stator blades. toric blades 16 of the annular row of stator blades 16, or even of each of the other stator blades 16 of the annular row of stator blades 16. Here too, the edge 22 of each platform 20 may be radially flush over the entire periphery with the radially external face 15 of the hub 12. Each of the platforms associated with a stator blade having a different pitch angle may be geometrically different from the other platforms.

[0051] The aeronautical thruster may have at least one second configuration in which the pitch angle y of the first stator blade 16a and the pitch angle y of the second stator blade 16b are different respectively from the pitch angle y of the first stator blade 16a and the pitch angle y of the second stator blade 16b in the first configuration of the aeronautical thruster. In other words, said at least first and second configurations of the aeronautical thruster may be characterized by the pitch angle of said at least first and second stator blades 16a; 16b, preferably also by the pitch angle of said at least third and fourth stator blades 16c; 16d, more preferably by the pitch angle of each of the stator blades 16.

[0052] With reference to [Fig.7], for each point Pi of the peripheral edge 22 of each platform 20, there may be associated a point Pj of the radially external face 15 of the hub 12 which is radially aligned with said point Pi of the peripheral edge 22 with respect to the pitch axis AC of the corresponding stator blade 16 and which delimits the corresponding housing 13 of the hub 12. In other words, said associated point Pj of the radially external face may be located on the contour of said housing. Also, for each point Pi of the peripheral edge 22 of each platform 20, there may be defined on the one hand a first distance DI which separates said point Pi of the peripheral edge 22 from an intersection between the longitudinal axis X and the pitch axis AC of the associated stator blade 16, and on the other hand a second distance D2 which separates said associated point Pj from the radially external face 15 of the hub 12 from said intersection.When it is described that the peripheral edge 22 of a platform 20 is radially flush over the entire periphery with the radially external face 15 of the hub 12, it can be understood that the difference between the first distance DI and the second distance D2 for each point Pi of the edge 22 of the platform 20 is as small as possible, for example, in particular according to the manufacturing tolerances, this can be less than or equal to 2 mm, preferably less than or equal to 1 mm.

[0053] Furthermore, as can be seen in [Fig. 5], the aeronautical thruster 10 may comprise an annular row of non-ducted rotor blades 14. The annular row of stator blades 16 may comprise said at least first and second stator blades 16b, or even the third stator blade 16c and the fourth stator blade 16d. It is not excluded that the annular row of stator blades 16 has one or several stator blades 16 of another type which differs from the stator blades 16 as described above and below in the present description, for example whose geometry is different for one or more blades, or for example still with fixed pitch, whose geometry is different or even whose assembly to the hub 12 is different. The annular row of rotor blades can be arranged upstream of the annular row of stator blades 16 along the longitudinal axis X. Also, the rotor blades 14 can be described as upstream rotor blades 14 and the stator blades 16 can be described as downstream stator blades 16.

[0054] The annular row of rotor blades 14 is rotatable about the longitudinal axis X. The annular row of stator blades 16 is locked in rotation about the longitudinal axis X. The annular row of stator blades 16 is therefore fixed about the longitudinal axis X. In other words, the stator blades 16 are not driven in rotation about the longitudinal axis X. The annular row of rotor blades 14 and the annular row of stator blades 16 may respectively define an upstream propeller and a downstream propeller. The annular row of stator blades 16 may be a rectifier. The aeronautical thruster 10 may comprise between 2 and 25 rotor blades 14, preferably between 4 and 16 rotor blades 14, more preferably between 10 and 14 rotor blades 14.The aeronautical propeller 10 may comprise between 2 and 25 stator blades 16, preferably between 4 and 16 stator blades 16, more preferably between 8 and 14 stator blades 16.

[0055] The term "unducted" used in reference to the rotor blades 14 and the stator blades 16 indicates that the rotor blades 14 and the stator blades 16 are not surrounded by a nacelle, unlike conventional aeronautical thrusters in which the fan is ducted inside a nacelle.

[0056] The aeronautical propeller may be a turbomachine with an “unducted” fan (or turboprop of the “Propfan” or “Open fan” type, or “Open rotor” or “Counter-Rotating Open Rotor” type). As in the example shown in [Fig. 5], the aeronautical propeller 10 may be in a “puller” configuration. Alternatively, the aeronautical propeller 10 according to the present description may be in a “pusher” configuration. It is not excluded that the aeronautical propeller may comprise (at least) a thermal engine, in particular a turbomachine, a turbo-engine, a turbojet, a turbofan, and / or (at least) an electric motor, and / or (at least) a hydrogen engine, and / or (at least) a hybrid engine: thermal and / or electric and / or hydrogen.

[0057] A stator blade is now described in more detail with reference to [Fig. 7]. Each stator blade 16 may extend radially. Each stator blade 16 may extend between a radially inner end, this being located at the level of the, i.e., closest to the hub 12 of the aeronautical propeller 10, and a radially outer end 31. The radially inner end may be, longitudinally, at a leading edge 32 of the blade or at the pitch axis AC of the stator blade 16 in question. Each stator blade 16 may comprise a root 30 at the radially inner end. The radially outer end 31 of each stator blade 16 is the opposite end of the radially inner end of the stator blade 16. The radially outer end 31 may be the free end of the stator blade 16, in particular in that the stator blade 16 is unducted. The radially inner end and the radially outer end of each of the stator blades 16 may be radially aligned and / or at the same longitudinal position.It is not excluded that the radially inner end and the radially outer end of each of the blades may be longitudinally and / or circumferentially offset relative to each other.

[0058] Each stator blade 16 may have an aerodynamic profile. For this purpose, each stator blade 16 may comprise a stack of sections 40 in the radial direction. Such a section 40 is visible in [Fig. 8]. For each blade, a stacking line may be defined which passes through the center of gravity of each section 40 of the blade. It is not excluded that the stacking line of one or more of the stator blades 16 forms a non-linear curve. In a particular case, the stacking line may extend radially in a rectilinear manner. Each section 40 extends in a respective section plane 40 which is perpendicular to the radial direction of extension of the corresponding stator blade 16. Each section 40 may comprise a leading edge 41 upstream and a trailing edge 42 downstream between which extend a lower surface line 43 and an upper surface line 44. Each section 40 may define an aerodynamic profile.Each section 40 may comprise a chord C defined by a straight portion connecting the leading edge 41 to the trailing edge 42. When reference is made to the aerodynamic profile of a section 40 or of a blade, it is understood to mean the two-dimensional conformation of the section, or respectively three-dimensional conformation of the blade, intended to optimize the airflow over the blade, independently of the pitch angle y of the blade or the angular position of the blade around the longitudinal axis X.

[0059] The leading edge 41 and the trailing edge 42 of the set of sections 40 of the stack of sections 40 may respectively form, for each stator blade 16, a leading edge 32 and a trailing edge 33 of the blade. Similarly, the intrados line 43 and the extrados line 44 of the set of sections 40 of the stack of sections 40 may respectively form, for each stator blade 16, an intrados face 34 and an extrados face 35 of the stator blade 16. Whatever the setting configuration of each of the stator blades 16, the intrados face 34 and the extrados face 35 may be, for each of the stator blades 16, positioned relative to each other in the same direction in the circumferential direction. can be defined for each stator blade 16 an intrados side and an extrados side on either side of the stator blade 16, the intrados and extrados sides coinciding with the intrados and extrados faces of the blade.

[0060] Each stator blade 16 has a respective pitch axis AC. The pitch axis AC of each stator blade 16 may be included in a plane perpendicular to the longitudinal axis X. In other words, the pitch axis AC of each stator blade 16 may extend in a direction of which a longitudinal component is zero. The pitch axis AC of each stator blade 16 may extend radially. It is not excluded that the pitch axis AC comprises a radial component and / or a longitudinal component and / or a circumferential component.

[0061] The pitch angle y of each stator blade 16 may correspond to the angle formed between, on the one hand, a first axis Al which is defined by the intersection O between the section plane of a reference section among the stack of sections of the blade and a plane perpendicular to the longitudinal axis X which may comprise the pitch axis AC of the stator blade 16, and on the other hand, the chord C of the reference section of the stator blade 16. The angle may be measured on the upstream side of the plane perpendicular to the longitudinal axis X. The angle may be measured positively in a direction going from the first axis Al to the chord C of the reference section, and more particularly in a direction coinciding with the direction going from the intrados line 43 to the extrados line 44.

[0062] The reference section of each stator blade 16 may be located at the radially inner end of the stator blade 16. Alternatively, the reference section of each stator blade 16 may be located, on the corresponding stator blade 16, at a radial distance from the longitudinal axis X which corresponds for example to 75% of a radially outer radius of the corresponding stator blade 16. Alternatively again, the reference section of each stator blade 16 may be located, on the stator blade 16, at a radial distance from the longitudinal axis X which corresponds to 75% of the radially outer radius of the stator blade 16 which has the minimum radially outer radius among the annular row of stator blades 16.

[0063] A stator blade 16 among the annular row of stator blades 16 may be said to have a “closed pitch” relative to another stator blade 16 of the annular row of stator blades 16 when it has a pitch angle y less than the pitch angle y of the second stator blade 16, preferably at least 0.1°, more preferably at least 1°. Conversely, a stator blade 16 of the annular row of stator blades 16 may be said to have an “open pitch” relative to another stator blade 16 of the annular row of stator blades when it has a pitch angle y greater than the pitch angle y of the second stator blade 16, preferably at least 0.1°, more preferably at least 1°.

[0064] The aeronautical propeller 10 may further comprise means for driving independently or together each of the platforms 20 in rotation around the respective setting axis AC. In particular, each platform 20 can be connected, at a radially internal face 23, to a setting arm which is adapted to rotate around the setting axis AC of the corresponding stator blade 16.

[0065] Finally, the hub 12 may be axisymmetrical about the longitudinal axis X. For example, a portion of the hub 12 longitudinally at the level of the annular row of stator blades 16 may be cylindrical of revolution about the longitudinal axis X. A diameter of the cylindrical portion of revolution may be greater than or equal to 1 m, preferably greater than or equal to 3 m. The hub 12 may radially delimit inside an air flow vein V around the aeronautical propeller 10, said being shown in [Fig.5].

[0066] In the following, reference is made more particularly to Figures 9 to 12.

[0067] Each platform 20 can be received by shape complementarity in the corresponding housing 13 of the hub 12. The peripheral edge 22 of each platform 20 may be circular around the pitch axis AC of the corresponding stator blade 16. This makes it possible to ensure the rotational mobility of each platform 20 around the pitch axis AC of the corresponding stator blade 16 relative to the hub 12 while reducing a clearance formed between each platform 20 and the hub 12. In other words, the peripheral edge 22 of each platform 20 and the corresponding housing 13 of the hub 12 may be circular around the pitch axis AC of the stator blade 16 secured to said platform 20.

[0068] At least one of the platforms 20, preferably each of the platforms 20, may comprise a first part 24 and a second part 25 which are structurally independent and between which the root 30 of the corresponding stator blade 16 is arranged, or even clamped. This makes it easier to assemble each platform 20 and the corresponding stator blade 16. The peripheral edge 22 of said at least one of the platforms 20 may therefore be discontinuous and be formed in part by the first part 24 and the second part 25 of the platform 20.

[0069] The first part 24 and the second part 25 of each platform 20 may have a half-disc shape.

[0070] According to a variant shown in [Fig. 9], the root 30 of each stator blade 16 may comprise a leading edge 32 upstream and a trailing edge 33 downstream between which extend a pressure face 34 and an extrados face 35. The first part 24 of each platform 20 may comprise an internal face complementary to the pressure face and opposite, or even resting on, the pressure face 34 of the corresponding stator blade 16 and the second part 25 of each platform 20 comprises an internal face complementary to the extrados face 35 and opposite, or even resting on, the extrados face 35 of the corresponding stator blade 16. This makes it possible to limit a clearance formed by each platform 20 and the corresponding stator blade 16 on either side of the foot 30.

[0071] According to the variant shown in [Fig. 10], the internal face of the first part 24 and the internal face of the second part 25 of each platform 20 may each comprise a recess receiving by complementary shape a part of the root 30 of the corresponding stator blade 16. This makes it possible to limit a clearance formed by each platform 20 and the corresponding stator blade 16 on either side of the root 30. The root 30 of each stator blade 16 may have any shape, in particular parallelepiped, cylindrical or elliptical. More specifically, the root of each stator blade 16 may have a shape which differs from the aerodynamic profile of the stator blade 16. It is therefore not excluded that the root of each stator blade 16 has a shape other than parallelepiped, cylindrical or elliptical.Also, the internal face of the first part 24 and the internal face of the second part 25 of each platform 20 may be opposite each other, or even bearing on each other, upstream and / or downstream of the root 30 of the corresponding stator blade 16. This makes it possible to further limit the clearance formed by each platform 20 and the corresponding stator blade 16 on either side of the root 30.

[0072] A peripheral clearance jp may be formed between each platform 20 and the corresponding housing 13 of the hub 12 radially relative to the pitch axis AC of the corresponding stator blade 16. The peripheral clearance jp may be less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm. For each platform 20, the aeronautical thruster 10 may comprise a peripheral sealing gasket housed in the peripheral clearance jp, preferably clamped between the platform 20 and the corresponding housing 13 of the hub 12 radially relative to the pitch axis AC of the corresponding stator blade 16.

[0073] A first internal clearance jil may be formed between the first part 24 of each platform 20 and the root 30 of the corresponding stator blade 16 and / or a second internal clearance ji2 may be formed between the second part 25 of each platform 20 and the root 30 of the corresponding stator blade 16. The first internal clearance jil and / or the second internal clearance ji2 may be less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm. For each platform 20, the aeronautical thruster 10 may comprise a first internal seal and / or a second internal seal housed respectively in the first internal clearance j11 and the second internal clearance j2, preferably clamped respectively between the first part 24 of the platform 20 and the root 30 of the corresponding stator blade 16 and between the second part 25 of the platform 20 and the root 30 of the corresponding stator blade 16..

[0074] With reference to [Fig. 12], each platform 20 may have a leading edge 26 which corresponds to the point of the peripheral edge 22 coinciding with an upstream end of the platform 20. The leading edge 26 of each platform 20 may be on the intrados side or the extrados side of the corresponding stator blade 16 depending on the pitch angle y of the corresponding stator blade 16. Each platform 20 may have a trailing edge which corresponds to the point of the peripheral edge 22 coinciding with a downstream end of the platform 20.

[0075] The leading edge 41 of the root section of one or more stator blades 16, or even of each of the blades, may be longitudinally at the same level or longitudinally downstream of the leading edge 26 of the corresponding platform 20. Alternatively, the leading edge 41 at the root section of one or more stator blades 16, or even of each of the stator blades 16, may be longitudinally upstream of the leading edge 26 of the corresponding platform 20. The root section may be defined as the section 40, complete or truncated, of the stator blade 16 which is radially aligned with the platform 20. Alternatively, the root section may be defined as the section 40, complete or truncated, of the stator blade 16 radially outside the platform 20 which is closest to the platform.In other words, the root section can be defined as the first section 40, or the lower section 40, of the stator blade 16 radially outside the platform 20.

[0076] The trailing edge 33 at the level of the root profile 30 of one or more stator blades 16, or even of each of the stator blades 16, may be longitudinally at the same level, downstream or upstream relative to the trailing edge of the corresponding platform 20.

[0077] For each platform 20, the peripheral edge 22 comprises an upstream point radially aligned with the chord C of the root section of the corresponding stator blade 16 and a downstream point aligned with the chord C of the root section 30 of the corresponding stator blade 16. For each platform 20, there may be defined on the one hand an upstream arc Aam on the peripheral edge 22 between the leading edge 26 of the platform 20 and the upstream point of the peripheral edge 22, and on the other hand a downstream arc Aav on the peripheral edge 22 of the platform 20 between the leading edge 26 of the platform 20 and the downstream point of the peripheral edge 22. In the first configuration of the aeronautical thruster 10, the first platform 20a may have a ratio of the upstream arc Aam relative to the downstream arc Aav different from that of the second platform 20b.

[0078] The peripheral edge 22 of each platform 20 may have a radius Rp relative to the pitch axis AC of the corresponding stator blade 16. A ratio of the upstream arc Aam of each platform 20 relative to the radius Rp of the peripheral edge 22 may be between -0.3 and 0.3, preferably between 0.12 and 0.12. Such ranges of values ​​are adapted to different flight points.

Claims

Claims

1. Aeronautical thruster (10) with a longitudinal axis (X), the aeronautical thruster (10) comprising: - a hub (12) comprising a radially external face, - an annular row of non-ducted stator blades (16) which comprises at least a first stator blade (16a) and a second stator blade (16b), - a plurality of platforms (20) which comprise at least a first platform (20a) and a second platform (20b), each platform (20) being arranged in a corresponding housing (13) of the hub (12) and comprising a radially external face (21) delimited by a peripheral edge (22), — the first stator blade (16a) being integral with the first platform (20a), the first platform (20a) being centered and rotatable about a first setting axis (AC) of the first stator blade (16a) relative to the hub (12), — the second stator blade (16b) being integral with the second platform (20b),the second platform (20b) being centered and rotatable about a second pitch axis (AC) of the second stator blade (16b) relative to the hub (12), and the aeronautical thruster (10) having at least a first configuration in which a pitch angle (y) of the first stator blade (16a) is different from a pitch angle (y) of the second stator blade (16b) and in which the edge (22) of the first platform (20a) and the edge (22) of the second platform (20b) are each radially flush over the entire periphery with the radially external face (15) of the hub (12).,

2. Aeronautical thruster (10) according to the preceding claim, in which each platform (20) is received by complementary shape in the corresponding housing (13) of the hub (12) and in which the peripheral edge (22) of each platform (20) is circular around the pitch axis (AC) of the corresponding stator blade (16).

3. An aeronautical thruster (10) according to any one of the preceding claims, each stator blade (16) extending radially between a root (30) and a head, and wherein at least one of the platforms (20), preferably each of the platforms (20), comprises a first part (24) and a second part (25) structurally independent and between which is arranged, or even clamped, the foot (30) of the corresponding stator blade (16).

4. An aeronautical propeller (10) according to the preceding claim, claim 2 applying, wherein the first part (24) and the second part (25) of each platform (20) have a half-disc shape.

5. Aeronautical thruster (10) according to claim 3 or 4, the root (30) of each stator blade (16) comprising a leading edge (32) upstream and a trailing edge (33) downstream between which extend a lower surface face (34) and an upper surface face (35) and in which the first part (24) of each platform (20) comprises an internal face complementary to the lower surface face and opposite, or even resting on, the lower surface face (34) of the corresponding stator blade (16) and the second part (25) of each platform (20) comprises an internal face complementary to the upper surface face (35) and opposite, or even resting on, the upper surface face (35) of the corresponding stator blade (16).

6. Aeronautical thruster (10) according to any one of claims 3 to 5, in which the internal face of the first part (24) and the internal face of the second part (25) of each platform (20) each have a recess receiving by complementary shape a part of the foot (30) of the corresponding stator blade (16).

7. Aeronautical thruster (10) according to any one of claims 3 to 6, in which the internal face of the first part (24) and the internal face of the second part (25) of each platform (20) are opposite each other, or even bearing on each other, upstream and / or downstream of the root (30) of the corresponding stator blade (16).

8. Aeronautical propeller (10) according to any one of the preceding claims, in which the pitch angle (y) of each of the stator blades (16) in the first configuration of the aeronautical propeller (10) is between 65° and 95°, preferably between 73° and 87°.

9. A thruster according to any one of the preceding claims, in which a peripheral clearance (jp) is formed between each platform (20) and the corresponding housing (13) of the hub (12) radially relative to the pitch axis (AC) of the corresponding stator blade (16), the peripheral clearance (jp) being less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm.

10. A thruster according to any preceding claim, claim 3 applying, wherein a first internal clearance (ji1) is formed between the first portion (24) of each platform (20) and the root (30) of the corresponding stator blade (16) and / or a second internal clearance (ji2) is formed between the second portion (25) of each platform (20) and the root (30) of the corresponding stator blade (16), the first internal clearance (ji1) and / or the second internal clearance (ji2) being less than 15 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1 mm.

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