Aeronautical thruster

Abstract

The invention relates to an aeronautical thruster (10) comprising a hub (12) that comprises a radially outer face, a first platform (20) and a second platform (20) arranged in a cavity (13) of the hub (12) that each comprise a radially outer face (21) delimited by a peripheral edge (22), a first stator vane (16) secured to the first platform (20), and a second stator vane (16) secured to the second platform (20), the aeronautical thruster (10) having a first configuration in which a pitch angle of the first stator vane (16) is different from a pitch angle of the second stator vane (16), and in which the edges (22) of the first platform (20) and the second platform (20) are each radially flush with the radially outer face (15) of the hub (12).

Description

Description Title: Aeronautical propeller Technical field

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

[0002] Below, we will only refer to the case of turbomachines, since the type(s) of engine included in the aeronautical propeller is not decisive here.

[0003] An "unducted" fan turbomachine (or "Propfan" or "Open Fan" or "Open rotor" or "Counter-Rotating Open Rotor" turboprop) 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 Figure 1. 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, we know the “Unducted Single (or Stator) Fan” (USF) type turbomachines in each of which, as illustrated in figure 1, the annular row of unducted upstream blades 14 is mounted to rotate about the longitudinal axis X and the annular row of unducted downstream blades 16 is fixed. In other words, the annular row of upstream blades 14 is of the rotor type and the annular row of downstream blades 16 is of the stator type. The direction of rotation of the upstream rotor blades 14 is not decisive. The annular row of downstream stator blades 16 can be centered on an axis coinciding or not with the longitudinal axis X. The upstream rotor blades 14 and the downstream stator blades 16 can be of variable pitch. As illustrated in Figure 1, the annular row of downstream stator blades 16 is centered on the longitudinal axis X.Such a USF type configuration makes it possible to exploit, 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 driven in rotation. around the longitudinal axis X by the turbine(s) 6 which itself drives the compressor(s) 2. The turbomachine 10 generally comprises a speed reduction box ("gearbox" in English) in order to decouple the rotation speed of the turbines 6 from the rotation 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 because 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 a shroud results in 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 unshrouded 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 airflow at the free radially external ends of the upstream rotor blades 14 which impact the downstream stator blades 16.

[0010] However, excessive noise levels are detrimental to the comfort of passengers on the aircraft on which the turbomachine is installed. In addition, current standards impose a maximum noise threshold, particularly in areas close to the ground, i.e. during takeoff and landing.

[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 according to the position around the longitudinal axis X of the downstream stator blade 16, which can lead to a thrust provided by the downstream propeller or stator which is not not satisfactory during the incidence operating phases of the turbomachine 10, particularly 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 propeller or downstream 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 propeller or downstream stator also has the disadvantage of causing an aerodynamic load applied to each of the downstream stator blades 16 which differs depending on the position around the longitudinal axis X of the downstream stator blade 16.

[0013] In order to overcome these drawbacks, it was 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 visible in Figure 2, each downstream stator blade 16 is mounted at its lower end on a platform 20 which forms an airflow surface at the lower exterior of the downstream stator blade. However, the radially external 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 modified, 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 thruster. Summary

[0015] A longitudinal axis aeronautical thruster is proposed, 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 integral with the second platform, the second platform being centered and rotatable about a second pitch axis 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 tip. At least one of the platforms, preferably each of the platforms, may comprise a first portion and a second portion that 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 can have a half-disc shape.

[0019] The root of each stator blade may comprise a leading edge on the upstream side and a trailing edge on the downstream side 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 first part and / or the second part may extend upstream of the root of the blade so that the leading edge of the root may be axially downstream of the internal face of the first part and / or the internal face of the second part, and preferably in which the ratio between on the one hand an axial distance between the leading edge of the root and the peripheral edge of the first part or the second part and on the other hand a radius of the peripheral edge of the platform relative to the setting axis is between 2% and 8%.

[0021] 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.

[0022] 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 foot of the corresponding stator blade.

[0023] The first part and the second part may each comprise one or more holes, the aeronautical thruster further comprising attachment means, such as screws, each passing through a respective hole in the first part and the second part, the attachment means being adapted for fixing the first part and the second part to a wedging arm.

[0024] The first portion and the second portion may each comprise a radially outer face, the radially outer face of the first portion having a first surface, the radially outer face of the second portion having a second surface, the ratio of the maximum surface area among the first surface and the second surface to the minimum surface area among the first surface and the second surface being between 1.01 and 1.15.

[0025] 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°.

[0026] A peripheral clearance may be formed between each platform and the corresponding housing of the hub radially relative to the alignment 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.

[0027] 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.

[0028] Each platform can have a parameter P between 0.88 and 0.98, the parameter P being defined by p=TT*Rn / ((N+1 )*Rp) where - Rn is the radius of the hub (in this case the radially external face of the hub) relative to the longitudinal axis X, - N is the number of stator blades on the annular row, - Rp is the radius of the peripheral edge of the platform relative to the alignment axis.

[0029] According to another aspect, there is provided a propulsion assembly for an aircraft comprising an aeronautical propeller as described above and a pylon adapted to fix the aeronautical propeller to the aircraft, the pylon comprising an upstream portion arranged circumferentially between the first stator blade and the second stator blade, the first stator blade and the second stator blade being circumferentially adjacent. Brief description of the drawings

[0030] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which:

[0031] Figure 1 is a partial schematic sectional view of a prior art unducted fan turbomachine.

[0032] Figure 2 is a schematic sectional view of a stator blade and a corresponding platform of the turbomachine of Figure 1, in a first pitch configuration.

[0033] Figure 3 is a schematic cross-sectional view of the stator and platform blade of Figure 2, in a second pitch configuration.

[0034] Figure 4 is a schematic top view of the stator blade and platform of Figure 3 that illustrates descending and ascending steps formed between the platform and the hub.

[0035] Figure 5 is a partial schematic sectional view of an aeronautical propeller according to the present description.

[0036] Figure 6 includes Figures 6a to 6c which illustrate a timing configuration of the aeronautical propeller according to several variants.

[0037] Figure 7 is a schematic sectional view of a stator blade and corresponding platform of the aeronautical thruster of Figure 5.

[0038] Figure 8 a schematic view of the downstream stator blade figure 7 in section plane VIII-VIII.

[0039] Figure 9 is a schematic top view illustrating a first variant embodiment of the platform of Figure 7.

[0040] Figure 10 is a schematic top view illustrating a second alternative embodiment of the platform of Figure 7.

[0041] Figure 11 is a schematic top view illustrating a third alternative embodiment of the platform of Figure 7.

[0042] Figure 12 is a schematic top view illustrating parametric features of the platform of Figure 7.

[0043] Figure 13 is a schematic top view illustrating an alternative to the first embodiment of the platform of Figure 9. Description of the embodiments

[0044] There is now described, with reference to figures 5 to 12, an aeronautical propeller 10 with longitudinal axis X visible as a whole in figure 5.

[0045] The aeronautical propellant 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.

[0046] 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.

[0047] Remarkably in Figure 6a, the aeronautical thruster 10 has 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.Furthermore, the first stator blade 16a and the second stator blade may be circumferentially adjacent (or in other words, circumferentially consecutive in the annular row of stator blades 16). However, this is not mandatory.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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. An embodiment is not excluded in which the circumferential spacing between two platforms 20 is different between two pairs of platforms 20. 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.

[0052] Each stator blade 16 may be integral with the corresponding platform 20 as seen in Figure 11. Alternatively, each stator blade 16 may be rigidly connected to the corresponding platform 20, by any known fixing means, for example by bolting.

[0053] 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 which are not ducted. The third stator blade 16c may be circumferentially adjacent to the first stator blade 16a. The fourth stator blade 16d may be circumferentially adjacent to the second stator blade 16b. The aeronautical thruster 10 may comprise a third platform 20c and a fourth platform 20d. The third stator blade 16c may be integral with the third platform 20c, the third platform 20 being centered and rotatable about a third setting axis AC of the third stator blade 16c relative to the hub 12.The fourth stator blade 16d may be integral with 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 one another, 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.

[0054] 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.

[0055] According to another variant not shown of the first configuration of the aeronautical propeller 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.

[0056] According to another variant of the first configuration of the aeronautical thruster 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 stator 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.

[0057] 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.

[0058] With reference to Figure 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 D1 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 D1 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, more preferably less than 0.5 mm, more preferably less than 0.2 mm.

[0059] Furthermore, as seen in Figure 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 more 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.

[0060] 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 thruster 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.

[0061] 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.

[0062] The aeronautical thruster may be a “non-ducted” fan turbomachine (or “Propfan” or “Open fan” type turboprop, or “Open rotor” or “Counter-Rotating Open Rotor” type turboprop). As in the example shown in FIG. 5, the aeronautical thruster 10 may be in a “puller” configuration. Alternatively, the aeronautical thruster 10 according to the present description may be in a “pusher” configuration. It is not excluded that the aeronautical thruster may comprise (at least) a thermal engine, in particular a turbomachine, a turboshaft engine, a turbojet engine, a turbofan engine, and / or (at least) an electric engine, and / or (at least) a hydrogen engine, and / or (at least) a hybrid engine: thermal and / or electric and / or hydrogen.

[0063] 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, the latter 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 the level of a leading edge 32 of the blade or at the level of the pitch axis AC of the stator blade 16 in question. Each stator blade 16 may comprise a root 30 at the level of 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.

[0064] 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 Figure 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 pressure line 43 and an extrados line 44. Each section 40 may define an aerodynamic profile. Each section 40 may comprise a chord C defined by a straight line portion connecting the leading edge 41 at the trailing edge 42. When reference is made to the aerodynamic profile of a section 40 or 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.

[0065] The leading edge 41 and the trailing edge 42 of all the 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 all the 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 pitch 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. For each stator blade 16, a lower surface side and an upper surface side can be defined on either side of the stator blade 16, the lower surface and upper surface sides coinciding with the lower surface and upper surface faces of the blade.

[0066] 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.

[0067] The pitch angle y of each stator blade 16 may correspond to the angle formed between, on the one hand, a first axis A1 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 A1 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.

[0068] 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.

[0069] 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°.

[0070] The aeronautical thruster 10 may further comprise means for independently or together driving each of the platforms 20 in rotation about the respective pitch axis AC. In particular, each platform 20 may be connected, at a radially internal face 23, to a pitch arm which is adapted to rotate about the pitch axis AC of the corresponding stator blade 16. Each platform may comprise attachment means, such as screws, for being fixed to the corresponding pitch arm.

[0071] 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 thruster 10, said being shown in FIG. 5.

[0072] In the following, reference is made more particularly to Figures 9 to 12.

[0073] Each platform 20 can be received by complementary shape in the corresponding housing 13 of the hub 12. The peripheral edge 22 of each platform 20 can be circular around the setting axis AC of the corresponding stator blade 16. This makes it possible to ensure the rotational mobility of each platform 20 around the setting 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 can be circular around the setting axis AC of the stator blade 16 secured to said platform 20.

[0074] 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.

[0075] Unless otherwise specified, the following description relating to Part 1 24 and Part 25 applies to one or more platforms, or even each of the platforms.

[0076] The first part 24 and the second part 25 may each have a half-disc shape.

[0077] Each of the first part 24 and the second part 25 may comprise one or more holes 27 adapted for the passage of attachment means, such as screws, for fixing the corresponding part to a wedging arm (which may be common to the parts 24, 25 of the platform 20 in question). In this sense, each hole 27 may be radially through. The aeronautical thruster may comprise attachment means, such as screws, each passing through a respective hole 27 in the first part 24 and the second part 25. For each platform, the aeronautical thruster comprises an attachment means, such as a screw, for each hole through the first part 24 and for each hole through the second part 25.Thus, it is possible to dismantle the parts 24, 25 of each platform 20 easily radially from the outside, which represents a significant time saving for maintenance and a reduction in costs and ultimately facilitates accessibility to the systems under the platforms.

[0078] Each hole may extend substantially radially through the corresponding portion 24, 25. The number of holes may vary between 3 and 6 for each portion 24, 25, which is sufficient to ensure their mechanical strength. The first portion and the second portion 25 of each platform 20 may have an identical number of holes. Each hole may have a radius. The radius of each hole may vary between 2% and 30% of a radius Rp of the peripheral edge of the corresponding platform, and preferably between 5% and 25%.

[0079] Each of the first portion 24 and the second portion 25 may comprise a radially outer face 28. The radially outer faces 28 of the first portion 24 and the second part 25 can each be said to be "wet" in that they are in contact with the flow of air around the aeronautical thruster, circumferentially on a respective side of the root of the corresponding stator blade 16. The radially external face 28 of the first part 24 may have a first surface S1. The radially external face 28 of the second part 25 may have a second surface S2. The ratio between the maximum surface area among the first surface S1 and the second surface S2 and the minimum surface area among the first surface S1 and the second surface S2 may be between 1.01 and 1.15. This makes it possible to have wetted surfaces and therefore relatively similar friction forces between the first part 24 and the second part 25, which better distributes the mechanical forces between the first part 24 and the second part 25.Said wetted surface ratio may be different for two platforms 20 whose stator blades are circumferentially adjacent and have a different pitch angle from each other. Generally, the wetted surface ratio may be different for at least two platforms 20, and preferably for each of the platforms (in this sense, the wetted surface ratio may be unique for each platform).

[0080] In one embodiment, the first surface is greater than the second surface for at least one of the platforms 20. The first surface S1 is located on the intrados side (concavity of the profile of the stator blade near the hub) and the second surface S2 is located on the extrados side. Having a first surface greater than the second surface therefore makes it possible to better adapt the wetted surface of each of the platforms according to the shape of the aerodynamic profile near the hub and therefore to reduce aerodynamic losses by friction.

[0081] According to a variant shown in Figure 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 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 may comprise 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 root 30.

[0082] According to an alternative shown in Figure 13, the leading edge 32 of the root 30 may be axially downstream of the inner face of the first part 24 (case illustrated in Figure 13) and / or the inner face of the second part 25. In other words, the first part 24 and / or the second part 25 may extend upstream of the root 30 of the blade 16. In this sense, the root 30 may be, upstream (in particular at the level of the leading edge 32) surrounded axially and circumferentially by the first part 24 and the second part 25. An axial distance L may be defined between the leading edge 32 of the root 30 and the peripheral edge of the first part 24 (case of Figure 13) or the peripheral edge of the second part 25. The ratio between the axial distance L and the radius Rp of the peripheral edge of the platform relative to the axis of The stall can be between 2% and 8%. The axial distance can be measured along the longitudinal direction X of the propeller or along the direction defined by the chord of foot 30, that is to say the line which passes through the points corresponding to the leading edge and the trailing edge of foot 30.

[0083] According to the variant shown in Figure 10, the inner face of the first part 24 and the inner face of the second part 25 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 may be opposite each other, or even bearing on each other, upstream and / or downstream of the foot 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 foot 30.

[0084] 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 seal 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.

[0085] A first internal clearance ji1 may be formed between the first portion 24 and the root 30 of the corresponding stator blade 16 and / or a second internal clearance ji2 may be formed between the second portion 25 and the root 30 of the corresponding stator blade 16. The first internal clearance ji1 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 ji1 and the second internal clearance ji2, preferably clamped respectively between the first portion 24 of the platform 20 and the root 30 of the corresponding stator blade 16 and between the second portion 25 of the platform 20 and the root 30 of the corresponding stator blade 16.

[0086] With reference to Figure 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.

[0087] 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.

[0088] 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.

[0089] 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.Generally speaking, the ratio of the upstream arc Aam to the downstream arc Aav may vary for at least two or more platforms 20, or even for each of the platforms 20 (in this sense, the ratio of the upstream arc Aam to the downstream arc Aav may be unique for each platform).

[0090] 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 suitable for different flight points.

[0091] For one or more platforms 20, or even for each platform 20, a parameter P can be defined which varies between 0.88 and 0.98, the parameter P being defined by p=TT*Rn / ((N+1 )*Rp) where - Rn is the radius of the hub 12 (in this case the radially external face of the hub) relative to the longitudinal axis X, - N is the number of stator blades 16 on the annular row, - Rp is the radius of the peripheral edge 22 of the platform 20 relative to the alignment axis AC.

[0092] This provides a spacing between the adjacent platforms 20 in the circumferential direction which allows easy access to the installation and facilitates dismantling of the platforms, for example to access screws on the platforms. This setting therefore simplifies maintenance operations while ensuring adequate spacing to ensure good aerodynamic performance.

[0093] With reference to Figure 6, a propulsion assembly for an aircraft is described which comprises an aeronautical propeller as described above and a pylon 50 adapted to fix the aeronautical propeller 10 to the aircraft, here at the level of a wing of the aircraft (in other words, the wing). Alternatively, the pylon can be adapted to fix the aeronautical propeller 10 at the level of a fuselage, in particular the rear, of the aircraft.

[0094] The pylon 50 has a radially internal end by which it is connected to the hub 12 of the aeronautical propeller. The pylon 50 extends generally radially in that it extends in a direction comprising at least one radial component. It is not excluded that the pylon 50 extends in a direction also comprising a longitudinal component and / or a circumferential component. In the example of FIG. 6, the pylon extends in a direction comprising a radial component and a longitudinal component. The pylon 50 comprises a leading edge 51 and a trailing edge between which extend on each side in the circumferential direction an extrados face 52 and an intrados face 53.The extrados face 52 and the intrados face 53 of the pylon 50 are, at least on an upstream portion of the pylon 18, arranged circumferentially on each side of a radial plane defined by the longitudinal axis X and a radial axis passing through the leading edge 51 of the radially internal end of the pylon 18. In the example illustrated, the pylon 50 has an aerodynamic profile.

[0095] Also, the pylon 50 is arranged longitudinally in part downstream of the annular row of stator blades 16. Indeed, in the example of FIG. 6, the pylon 50 (at an upstream end portion) is also arranged circumferentially, in part, between two circumferentially adjacent downstream stator blades 16. Said two circumferentially adjacent downstream stator blades 16 may correspond to the first stator blade 16a and the second downstream stator blade 16b having a pitch angle y that is different from each other and whose platform edges 20a, 20b are each radially flush over the entire periphery with the radially external face 15 of the hub 12. Adapting the pitch angle y around the pylon allows the flow to better bypass the pylon and therefore avoid separations and / or impacts that could reduce aerodynamic performance.More generally, the propulsion assembly may comprise the pylon and the aeronautical propeller as described above according to any one of the variants described with reference to figures 6a, 6b and 6c.

Claims

Claims

1. Aeronautical thruster (10) with 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 secured to the first platform (20a), the first platform (20a) being centered and rotatable around 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 propeller (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. 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 in which 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 root (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 extrados face (35) and opposite, or even resting on, the extrados face (35) of the corresponding stator blade (16).

6. Aeronautical propeller (10) according to the preceding claim, in which the first part (24) and / or the second part (25) extend upstream of the root (30) of the blade (16) so that the leading edge (32) of the root (30) can be axially downstream of the internal face of the first part (24) and / or of the internal face of the second part (25), and preferably in which the ratio between on the one hand an axial distance (L) between the leading edge (32) of the root (30) and the peripheral edge (22) of the first part (24) or of the second part (25) and on the other hand a radius (Rp) of the peripheral edge (22) of the platform (20) relative to the setting axis is between 2% and 8%.

7. Aeronautical thruster (10) according to any one of claims 5 or 6, 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).

8. Aeronautical thruster (10) according to any one of claims 5 to 7, 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).

9. An aeronautical thruster (10) according to any one of claims 3 to 8, wherein the first part (24) and the second part (25) each comprise one or more holes (27), the aeronautical thruster further comprising fastening means, such as screws, each passing through a respective hole (27) in the first part (24) and the second part (25), the fastening means being adapted for fixing the first part (24) and the second part (25) to a wedging arm.

10. An aeronautical thruster (10) according to any one of claims 3 to 9, wherein the first portion (24) and the second portion (25) each comprise a radially outer face (28), the radially outer face (28) of the first portion (24) having a first surface (S1), the radially outer face 28 of the second portion (25) having a second surface (S2), the ratio between the maximum surface area among the first surface (S1) and the second surface (S2) and the minimum surface area among the first surface (S1) and the second surface (S2) being between 1.01 and 1.

15.

11. Aeronautical thruster (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 thruster (10) is between 65° and 95°, preferably between 73° and 87°.

12. Aeronautical thruster (10) 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 setting 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.

13. An aeronautical thruster (10) according to any one of the preceding claims, claim 3 applying, wherein a first internal clearance (ji1) is 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) is formed between the second part (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.

14. An aeronautical thruster (10) according to any one of the preceding claims, each platform (20) has a parameter (P) of between 0.88 and 0.98, the parameter P being defined by p=TT*Rn / ((N+1 )*Rp) where - Rn is the radius of the hub (12) relative to the longitudinal axis X, - N is the number of stator blades (16) on the annular row, - Rp is the radius of the peripheral edge (22) of the platform (20) relative to the alignment axis (AC).

15. A propulsion assembly for an aircraft comprising an aeronautical propeller (10) according to any one of the preceding claims and a pylon (50) adapted to fix the aeronautical propeller (10) to the aircraft, the pylon comprising an upstream portion arranged circumferentially between the first stator blade (16a) and the second stator blade (16b), the first stator blade (16a) and the second stator blade (16b) being circumferentially adjacent.

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