Unfaired turbomachine comprising stator blades having different chords

Abstract

An aircraft comprising at least one unfaired turbomachine for aircraft propulsion, the turbomachine comprising a rotor and a stator comprising a plurality of stator blades extending radially about the longitudinal axis, each stator blade being defined, in a plane transverse (PT) to the longitudinal axis, by an angular position (θ). The stator of the turbomachine comprising stator blades having a first chord, called conventional blades (51), and at least one stator blade having a second chord, larger than the first chord, called an elongated blade (52), the rotor being configured to rotate in a predetermined direction of rotation about the longitudinal axis (X), said at least one elongated blade (52) being at an angular position (θ) belonging to a climb range (PM) defined between 180° and 360°. (Shortcut Figure: Figure 4)

Description

Title of the invention: Unducted turbomachine comprising stator blades having different chords Technical field

[0001] The present invention relates to the field of turbomachines used for the propulsion of an aircraft and more particularly relates to a stator of an unducted turbomachine.

[0002] In a known manner, an aircraft comprises a turbomachine extending longitudinally along an axis and making it possible to move the aircraft from an air flow circulating from upstream to downstream. Subsequently, the terms "upstream" and "downstream" are defined relative to the longitudinal axis oriented from upstream to downstream. Similarly, the terms "inner" and "outer" are defined according to the radial direction relative to the longitudinal axis.

[0003] The turbomachine comprises a primary vein delimited by a casing, designated "inter-vein casing", and supplied by an upstream fan. The fan makes it possible to produce a primary air flow inside the inter-vein casing and a secondary air flow around the inter-vein casing. The fan, also designated "rotor", is mounted to rotate around the longitudinal axis and makes it possible to accelerate the air flow from upstream to downstream.

[0004] The turbomachine comprises an unducted fan, without an external casing, known to those skilled in the art under the designation "open rotor". Such a turbomachine has the advantage of having a reduced mass in the absence of an external casing. In other words, the secondary air flow circulating outside the inter-vein casing circulates in a secondary vein open to the outside.

[0005] In a known manner, the turbomachine comprises, downstream of the fan, a stator for straightening the air flow accelerated by the fan. The stator comprises a plurality of stator blades, also called "straighteners", extending radially between a root connected to the inter-flow casing and a free head.

[0006] A main function of a stator is to deflect the direction of the air flow in order to modify the kinetic energy so that it can be used for the thrust of the turbomachine. The stator thus makes it possible to reduce aerodynamic losses, ensure good efficiency of the turbomachine and guarantee robustness to the incidence of the air flow in order to ensure the operating stability of the turbomachine. In a known manner, the stator blades have a precise and predefined geometry allowing the aforementioned functions to be best performed. The stator blades are dimensioned so as to have a predefined section and orientation for optimize the airflow deflection. In practice, all stator blades have the same length, the same chord and, at all times, the same pitch.

[0007] An unducted turbomachine has the disadvantage of being sensitive to the impact of the external airflow compared to a ducted turbomachine such as a turbojet. In particular, the airflow passing through the turbomachine causes aerodynamic effects on the rising and falling blades of the rotor, which results in a heterogeneous airflow that can affect the performance of the turbomachine. Indeed, the blades are more loaded when they rise (moving from a low point to a high point during rotation) and, conversely, less loaded when they descend (moving from a high point to a low point during rotation).

[0008] The invention thus aims to eliminate at least some of these drawbacks by proposing an unducted turbomachine having optimal thrust, even when the air flow entering the turbomachine is heterogeneous.

[0009] Document FR3092868 discloses a turbojet (ducted turbomachine) comprising in a secondary vein a stator wheel comprising blades having different chords. The different chords make it possible to characterize each blade in a precise function. In particular, each blade of the stator wheel described in document FR3092868 has the purpose, for example, of improving the recovery and transmission of forces in the turbomachine or even of improving the heat exchange between a flow of hot primary air circulating in the primary vein and a flow of cold secondary air circulating in the secondary vein. PRESENTATION OF THE INVENTION

[0010] The invention relates to an aircraft comprising at least one unducted turbomachine for propelling the aircraft, the turbomachine extending along a longitudinal axis and being configured to accelerate an airflow flowing from upstream to downstream, the turbomachine comprising a rotor and a stator, mounted downstream of the rotor, the stator comprising a plurality of stator blades for straightening the airflow from the rotor, extending radially with respect to the longitudinal axis and distributed angularly around the longitudinal axis, each stator blade comprising a leading edge and a trailing edge defining between them a chord in a plane of revolution defined with respect to the longitudinal axis, each stator blade being defined, in a plane transverse to the longitudinal axis, by an angular position, the rotor being configured to rotate in a predetermined direction of rotation with respect to the longitudinal axis,the angular positions of the stator blades being defined over an angular range of 0-360°, the angular position 0° being defined in the high position relative to a vertical axis, the angular positions being defined in an increasing manner according to the predetermined direction of rotation of the rotor.

[0011] The aircraft is remarkable in that the stator of the turbomachine comprises stator blades having a first chord, called conventional blades, and at least one stator blade having a second chord, larger than the first chord, called elongated blade, said at least one elongated blade being positioned in a climb range defined between 180° and 360°.

[0012] Such an aircraft makes it possible to adapt the geometry of each stator blade according to its angular position on the stator, so as to adapt the load distribution of each stator blade according to the rising and falling blades of the rotor positioned opposite the stator. The rising and falling blades of the rotor are defined when the rotor is rotating and in a front view upstream of the aircraft. An elongated blade in fact allows it to support a greater load due to the rising blades of the rotor opposite which disturb the air flow passing through the turbomachine. Such a turbomachine thus makes it possible to limit the risk of local overloading of the stator and therefore the risk of aerodynamic separation. The turbomachine is thus more efficient and allows a greater thrust force while limiting its consumption. Thus, the rotor advantageously compensates for the load variations of the rotor blades to obtain the optimal thrust.

[0013] In a first embodiment, the rotor being configured to rotate in a clockwise direction of rotation, the climb range corresponds to a left half of the stator, in a front view upstream of the aircraft.

[0014] In a second embodiment, the rotor being configured to rotate in a counterclockwise direction of rotation, the climb range corresponds to a right half of the stator, in a front view upstream of the aircraft.

[0015] Preferably, the stator comprises at least two elongated vanes positioned in the rise range, allowing the chord of several stator vanes to be adapted to optimize the overall geometry of the stator and adapt the chord of several stator vanes to the loading they experience.

[0016] Preferably, the rise range is defined between 210° and 330°, making it possible to position said at least one elongated blade in an angular range corresponding to the rotor blades generating a greater flow.

[0017] Preferably, the rise range is defined between 225° and 315°, making it possible to ensure the positioning of the elongated blade opposite the rising blades of the rotor which generate the greatest air flow. In other words, the angular range opposite the blades of the rotor generating the greatest air flow comprises at least one elongated blade, making it possible to maximize the straightening of the air flow downstream of the turbomachine, which is then more efficient.

[0018] Preferably, the stator of the turbomachine comprises at least one stator blade having a third chord, called a shortened blade, the third chord being more smaller than the first chord so as to limit the risk of underloading a blade, said at least one shortened blade is positioned in a descent range, the descent range being defined between 0° and 180°. Each blade thus having a third reduced chord makes it possible to limit the risk of underloading a blade whose chord would be too large in relation to the air flow it receives, underloading being in fact a non-optimal operating condition.

[0019] In one embodiment, each shortened blade is diametrically opposed to an elongated blade, allowing for optimal geometry of the entire stator to enable optimal performance of the turbomachine.

[0020] Preferably, the diametrically opposite term is determined relative to the axis of the turbomachine.

[0021] Preferably, the first chord having a length, the third chord having a length between 70% and 95% of the length of the first chord. Such a third chord makes it possible to optimize the chord of the blade at loading while limiting the difference in chord and therefore the risk of local disturbances.

[0022] Preferably, the first chord having a length, the second chord having a length between 105% and 130% of the length of the first chord. Such a second chord makes it possible to optimize the chord of the blade at loading while limiting the difference in chord and therefore the risk of local disturbances.

[0023] Preferably, the chord difference between two adjacent stator blades is less than or equal to 25%. A limited chord difference for two adjacent blades makes it possible to limit the risks of local disturbances of the flow which could harm the operation of the stator.

[0024] Preferably, each stator blade having a maximum thickness in the plane of revolution, the relative thickness of a stator blade corresponding to the ratio of the maximum thickness to the chord, the difference in relative thickness between two adjacent stator blades having different chords is less than or equal to 25%. Such a difference in relative thickness makes it possible to limit local disturbances of the flow between two adjacent blades of different chords. PRESENTATION OF FIGURES

[0025] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0026] [Fig.l] is a schematic representation of an aircraft comprising an unducted turbomachine according to one embodiment of the invention.

[0027] [Fig.2] is a schematic representation of the unducted turbomachine of [Fig.l] comprising a rotor and a stator.

[0028] [Fig.3] is a schematic representation of blades of the stator of [Fig.2], in section in a plane of revolution around a longitudinal axis X.

[0029] [Fig.4] is a schematic representation in a plane transverse to the longitudinal axis X, of the blades of the stator of [Fig.2] in the example of a rotor rotating in a clockwise direction of rotation.

[0030] [Fig.5] is a schematic representation of the chord of each blade of the stator of [Fig.4] in the plane of revolution.

[0031] [Fig.6] is a graph representing the evolution of the chord of each blade of the stator of [Fig.4] as a function of their angular position in the transverse plane.

[0032] [Fig.7] is a schematic representation of a second example of distribution of elongated and shortened blades as a function of their angular position in the case of a rotor rotating in a counterclockwise direction of rotation.

[0033] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0034] The invention is described in this document with reference to a turbomachine mounted in an aircraft, however it goes without saying that it applies to any type of aircraft.

[0035] The aircraft A according to the invention is shown in Figures 1 and 2. For this purpose, with reference to [Fig.l], the aircraft A (in this example an airplane) comprises a turbomachine 1 extending longitudinally along an axis X and making it possible to move the airplane from an air flow F entering the turbomachine 1 and circulating from upstream to downstream. Subsequently, the terms “upstream” and “downstream” are defined relative to the longitudinal axis X oriented from upstream to downstream.

[0036] In a known manner, with reference to [Fig. 2], the turbomachine 1 comprises a primary vein delimited by a casing, designated “inter-vein casing” 2 and supplied by an upstream fan, designated rotor 3, mounted to rotate around the axis X. The rotor 3 makes it possible to accelerate the air flow F from upstream to downstream. In practice, the acceleration of the air flow F makes it possible to generate a thrust force allowing the aircraft A to move.

[0037] In a first embodiment, the rotor 3 is configured to rotate in a clockwise direction of rotation (as shown in [Fig. 4]). The direction of rotation of the rotor 3 is understood in a front view of the aircraft A, i.e. seen from upstream. As is known, the rotor 3 comprises a plurality of rotor blades which extend radially with respect to the longitudinal axis X and rotates about this axis. Each blade rotor evolves over 360° and is therefore successively descending and ascending in a plane PT transverse to the longitudinal axis X. The terms "rising" and "descending" are understood in relation to the vertical axis Z in a front view from upstream.

[0038] According to the invention, the turbomachine 1 is unducted, that is to say it has no external casing. Such a configuration of the turbomachine 1 is known to those skilled in the art under the generic designation “open rotor” and will not be described in more detail in this document.

[0039] Still with reference to [Fig. 2], the turbomachine 1 comprises a stator 4, mounted downstream of the rotor 3 and making it possible to straighten the air flow F accelerated by the rotor 3. The stator 4 comprises a plurality of stator vanes 5, also called “straighteners”, extending radially relative to the longitudinal axis X between a root 5P connected to the inter-flow casing 2 and a free head 5T. In the example shown, the air inlet of the primary flow is located between the rotor 3 and the stator 4.

[0040] In this embodiment, the turbomachine 1 comprises only a rotor 3 and a stator 4 in order to have a simple and lightweight structure. In addition, the rotor 3 / stator 4 pair is mounted upstream of the turbomachine 1 in order to form a turbomachine of the “puller” type (meaning “tractor” in English). It goes without saying that the rotor 3 / stator 4 pair could be mounted downstream of the turbomachine 1 in order to form a turbomachine of the “pusher” type (meaning “pusher” in English).

[0041] In a known manner, with reference to [Fig. 3], each stator blade 5 comprises a leading edge 5A, corresponding to the end located upstream and first coming into contact with the air flow F, and a trailing edge 5B, located downstream. Each stator blade 5 has a profile which is determined, in section, in a plane of revolution PR around the longitudinal axis X of the turbomachine 1. The plane of revolution PR is determined for a predetermined radial distance. In practice, each stator blade 5 comprises a plurality of characteristic profiles, determined in a plurality of planes of revolution around the longitudinal axis X of the turbomachine, along the turbomachine 1.

[0042] In the plane of revolution PR, with reference to [Fig. 3], each stator blade 5 has a profile P elongated from the leading edge 5A to the trailing edge 5B. In a known manner, the profile P is defined according to a plurality of geometric characteristics such as, for example, a length and a thickness. In this example, the profile P of a stator blade 5 is characterized by the distance between the leading edge 5A and the trailing edge 5B, designated chord C, and the maximum thickness Ep. In this example, the maximum thickness Ep is defined orthogonally to the direction of the mean line LMA of the blade. As illustrated in [Fig. 3], this mean line LMA (also known to those skilled in the art under its designation of skeleton line or camber line) connects the leading edge 5A to the trailing edge 5B and is equidistant from the intrados and the extrados. Similarly, still with reference to [Fig.3], a stator blade 5 is characterized by the inclination of its chord C relative to the longitudinal axis X of the turbomachine 1. Subsequently, for a profile P, a setting angle a is defined between the longitudinal axis X and the chord C. Finally, a stator 4 is characterized by its pitch PAS corresponding to the spacing between the trailing edges 5B of two adjacent stator blades 5 as illustrated in [Fig.3].

[0043] With reference to [Fig. 4], the stator blades 5 are distributed angularly around the longitudinal axis X in a plane PT transverse to the longitudinal axis X, shown in [Fig. 2]. Each stator blade 5 is defined, in the transverse plane PT, by an angular position 0, included in an angular range extending between 0° and 360°. In this example, the angular position 0° is defined in the high position relative to a vertical axis Z extending from the bottom to the top, as shown in [Fig. 4]. Similarly, the angular positions 0 are defined in an increasing manner between 0° and 360° according to the clockwise direction of rotation of the rotor 3 around the longitudinal axis X from the 0° position.

[0044] In the angular range between 0° and 360°, a descent angular range PD is defined, corresponding to the stator blades 5 positioned opposite the descending blades of the rotating rotor 3, and an ascent angular range PM, corresponding to the stator blades 5 positioned opposite the ascending blades of the rotating rotor 3.

[0045] In this example in which the rotor 3 rotates in a clockwise direction of rotation, the lowering range PD is defined between 0° and 180° on the right half of the stator and the raising range PM is defined between 180° and 360°, on the left half of the stator. The terms "left" and "right" are understood according to a view from upstream as illustrated in [Fig. 4]. Alternatively, in the case of a rotor rotating in a counterclockwise direction of rotation, the lowering ranges PD and the raising range PM would be reversed.

[0046] With reference to Figures 4 and 5, the stator 4 comprises, in the transverse plane PT, a plurality of stator blades 5 having a first chord C1. Such stator blades 5 are called “conventional blades” 51. The first chord C1 preferably has a length of between 200 and 600 mm.

[0047] The stator 4 of the turbomachine 1 according to the invention further comprises a plurality of stator blades 5 having a second chord C2, the second chord C2 being larger than the first chord C1 in the transverse plane PT, as shown in [Fig. 5]. Such stator blades 5 are called “elongated blades” 52. Preferably, the second elongated chord C2 has a length of between 105% and 130% of the length of the first chord C1. More preferably, the length of the second elongated chord C2 is between 105% and 115% of the length of the first string Cl. In this example, the stator 4 comprises a plurality of elongated blades 52, however it goes without saying that the stator 4 could just as well comprise a single elongated blade 52.

[0048] According to the invention, each elongated blade 52 is angularly positioned at least partly in the rise range PM, defined between 180° and 360°, corresponding to the stator blades 5 positioned opposite the rising rotor blades when the rotor 3 is rotated. Preferably, the rise range PM is defined between 210° and 330°, so as to take into account only the stator blades 5 which are particularly loaded compared to the adjacent stator blades 5.

[0049] More preferably, as shown in [Fig. 4], the rise range PM is defined between 225° and 315°, making it possible to increase the chord of the stator blades 5 only in a restricted angular range, making it possible to limit the complexity of the stator 4 and the manufacturing costs. Such a rise range PM also makes it possible to increase the chord C by only a limited number of stator blades 5.

[0050] The elongated blades 52 make it possible to increase the straightening of the air flow from the rotor 3 in the rise range PM, so as to limit the disturbances of the air flow F downstream of the turbomachine 1. The geometry of each stator blade 5 is thus adapted according to its loading. A longer chord C makes it possible to avoid overloading a stator blade 5 which would be particularly stressed.

[0051] In this example, as shown in [Fig.4], the stator 4 comprising ten stator blades 5, distributed angularly around the longitudinal axis X, the elongated blades 52 covering an angular range between 225° and 315° depending on the clockwise direction of rotation, the stator 4 comprises two elongated blades 52.

[0052] This document presents the example of a stator 4 comprising two elongated blades 52, however it goes without saying that the stator 4 could just as well comprise a different number of elongated blades 52. In other words, it goes without saying that the rise range PM could just as well comprise a single elongated blade 52 or a number greater than two elongated blades 52.

[0053] Preferably, the stator 4 of the turbomachine 1 also comprises a plurality of stator blades 5 having a third chord C3, the third chord C3 being smaller than the first chord C1 in the transverse plane PT, as shown in [Fig. 5]. Such stator blades 5 are called “shortened blades” 53. Preferably, the shortened third chord C3 has a length of between 70% and 95% of the length of the first chord C1. More preferably, the length of the shortened third chord C3 is between 85% and 95% of the length of the first chord C1.

[0054] In this example, with reference to [Fig.4], each shortened blade 53 is positioned angularly, in the transverse plane PT, so as to belong to an angular range diametrically opposite to the ascent range PM. The shortened blades 53 thus belong to an angular range called “descent” PD and corresponding to the angular range opposite the descending blades of the rotor 3, when the latter is rotating. In other words, the descent range PD is defined between 0° and 180° depending on the direction of rotation of the rotor 3. In particular, each shortened blade 53 is diametrically opposite to an elongated blade 52. In one embodiment, the stator 4 comprises a shortened blade 53 for each elongated blade 52. The shortened blades 53 make it possible to balance the entire stator 4 while limiting the risk of underloading a stator blade 5 which would be particularly less stressed. Indeed, underloading is a non-optimal operating condition.This document presents the example of a shortened blade 53 positioned diametrically opposite each elongated blade 52, however it goes without saying that the stator 4 could also comprise one (or more) shortened blades 53 which would not be diametrically opposite an elongated blade 52. In particular, in the case of a stator 4 comprising an odd number of blades, no diametrically opposite positioning would be achieved.

[0055] Preferably, the descent range PD is defined between 30° and 150°, so as to take into account only the stator blades 5 which are particularly lightly loaded compared to the adjacent stator blades 5.

[0056] More preferably, as shown in [Fig. 4], the descent range PD is defined between 45° and 135°, making it possible to shorten the chord C of the stator blades 5 only in a restricted angular range, making it possible to limit the complexity of the stator 4. Such a descent range PD also makes it possible to reduce the chord of only a limited number of stator blades 5.

[0057] In this example, as shown in [Fig.4], the stator 4 comprises in the descent range PD, two shortened blades 53, each positioned diametrically opposite one of the two elongated blades 52.

[0058] This document presents the example of a stator 4 comprising two shortened blades 53, since it comprises two elongated blades 52. However, it goes without saying that the stator 4 could just as well comprise a different number of shortened blades 53, for example a single shortened blade 53 or a number greater than two shortened blades 53.

[0059] By way of example, as illustrated in [Fig.4], the stator 4 comprises ten stator blades 5 distributed angularly around the longitudinal axis X, the elongated blades 52 corresponding to the stator blades 5 positioned in an angular range between 225° and 315°, the shortened blades 53 cover an angular range between 45° and 135°.

[0060] [Fig.6] is a graph representing the evolution of the chord C1, C2, C3 of each stator blade 5 as a function of its angular position 0, in an exemplary embodiment. In summary in this example, over the angular range from 0° to 360°: • each stator blade 5 whose angular position is between 0° and 45° is a conventional blade 51, • each stator blade 5 whose angular position is between 45° and 135° is a shortened blade 53, • each stator blade 5 whose angular position is between 135° and 225° is a conventional blade 51, • each stator blade 5 whose angular position is between 225° and 315° is an elongated blade 52, and • each stator blade 5 whose angular position is between 315° and 360° (therefore 0°) is a conventional blade 51.

[0061] This document presents the example in which each angular range as defined above comprises similar conventional blades 51, elongated 52 or shortened 53, however it goes without saying that each angular range could just as well alternatively comprise a combination of conventional blades 51 and elongated blades 52 or a combination of conventional blades 51 and shortened blades 53. In other words, it goes without saying that the angular range between 45° and 135° could comprise both one or more conventional blade(s) 51 and one or more shortened blade(s) 53 and the angular range between 225° and 315° could comprise both one or more conventional blade(s) 51 and one or more elongated blade(s) 52.

[0062] Preferably, the chord difference C1, C2, C3 between two adjacent stator blades 5 is less than 50%, more preferably less than 25%. Such a characteristic makes it possible not to affect the performance of the turbomachine 1, in particular, the local performance of the flow in the vicinity of each stator blade 5.

[0063] This document presents the example of a rotor 3 rotating in a clockwise direction of rotation, however it goes without saying that the rotor 3 could just as easily rotate in a direction of rotation opposite to the clockwise direction of rotation, as shown in [Fig.7],

[0064] The angular positions 0 of the stator blades 5 being defined in an increasing manner between 0° and 360° according to the clockwise direction of rotation of the rotor 3 around the longitudinal axis X from the 0° position, the angular ranges of ascent PM and descent PD remain unchanged according to the direction of rotation of the rotor 3. In this example, as shown in [Fig.7], the descent range PD between 0° and 180° is then defined on half left of stator 4 and the PM climb range between 180° and 360°, on the right half of stator 4, in a front view upstream of aircraft A.

[0065] This document presents the example of angular ranges comprising each of the stator blades 5 having the same chord C1, C2, C3, however it goes without saying that the stator 4 could just as well comprise a plurality of stator blades 5 each having a specific chord C that is elongated or shortened. In such a configuration, the stator 4 would comprise as many values ​​of chords C as there are stator blades 5. Such a stator 4 would have optimal performance since each stator blade 5 would have a chord C adapted to its own environment.

[0066] Preferably, the pitch PAS (shown in [Fig.3]) between two stator blades 5 is independent of the chord C, so if the pitch PAS is identical but the chord C is different between two adjacent stator blades 5, then the relative pitch (i.e. the ratio between the pitch PAS and the chord C varies as a function of the chord C) is different between two stator blades 5. Alternatively, the pitch PAS between two stator blades 5 having different chords C could be different.

[0067] Preferably, the maximum thickness Ep (shown in [Fig. 3]) of the stator blades 5 is different depending on whether it is a conventional blade 51, an elongated blade 52 or a shortened blade 53 so as to have a constant relative thickness (i.e. a ratio between the maximum thickness Ep and the chord C of the stator blade 5). Such a characteristic makes it possible to guarantee the mechanical characteristics of each stator blade 5 (flexibility, natural frequency, etc.). Alternatively, the conventional blades 51, the elongated blades 52 and the shortened blades 53 have the same maximum thickness Ep so as to limit the variation in section between two adjacent stator blades 5, which limits local disturbances of the flow.

[0068] Optionally, the variation in chord C between two stator blades 5 can be coupled with a variation in the pitch angle a (shown in [Fig. 3]) of the stator blades 5 as described previously. Such a modification advantageously makes it possible to limit the aerodynamic distortion of an air flow applied from downstream to upstream of the turbomachine 1 on the stator 4, for example when the aircraft is in flight.

[0069] The variable chords on the stator of an unducted turbomachine advantageously make it possible to take into account the effects of the airflow from the rotor on the stator blades. Lengthening the chord of the blades present opposite the rising rotor blades makes it possible to significantly improve the performance of each stator blade so as to load more heavily the blades most impacted by the rotor airflow and thus to improve the straightening of the airflow from the rotor and therefore the thrust of the aircraft. A distribution of conventional blades, elongated blades and reduced blades by angular ranges makes it possible to limit the industrial constraints of production and assembly of the stator by limiting the number of blades presenting different chords while allowing the loading of each blade to be adapted according to its direct environment.

[0070] This document describes an aircraft in which a turbomachine comprises stator blades whose chord is elongated to adapt the blades subjected to a greater load in relation to the rising blades of the rotor, however it goes without saying that the chord of the stator blades could just as well be adapted according to the load that the blades see during takeoff or landing or even according to the load due to the presence of an aerodynamic obstacle for example.

Claims

1.

2.

3.

4. Claims Aircraft (A) comprising at least one unducted turbomachine (1) for propelling the aircraft (A), the turbomachine (1) extending along a longitudinal axis (X) and being configured to accelerate an airflow (F) flowing from upstream to downstream, the turbomachine (1) comprising a rotor (3) and a stator (4), mounted downstream of the rotor (3), the stator (4) comprising a plurality of stator blades (5) for straightening the airflow from the rotor (3), extending radially with respect to the longitudinal axis (X) and distributed angularly around the longitudinal axis (X), each stator blade (5) comprising a leading edge (5A) and a trailing edge (5B) defining between them a chord (C) in a plane of revolution (PR) defined with respect to the longitudinal axis (X), each stator blade (5) being defined, in a transverse plane (PT) at the longitudinal axis (X), by an angular position (0),the rotor (3) being configured to rotate in a predetermined direction of rotation relative to the longitudinal axis (X), the angular positions (0) of the stator blades (5) being defined over an angular range of 0-360°, the angular position 0° being defined in the high position relative to a vertical axis (Z), the angular positions (0) being defined in an increasing manner according to the predetermined direction of rotation of the rotor (3), the angular range comprising a descent range (PD) defined between 0° and 180° and an ascent range (PM) defined between 180° and 360°, the aircraft (A) being characterized in that the stator (4) of the turbomachine (1) comprises stator blades (5) having a first chord (Cl), called conventional blades (51), and at least one stator blade (5) having a second chord (C2), larger than the first chord (Cl), called elongated blade (52), said at least one elongated blade (52) being angularly positioned in the climb range (PM),the descent range (PD) being free of elongated blade (25)., Aircraft (A) according to claim 1, wherein the stator (4) comprises at least two elongated blades (52) positioned in the climb range (PM). Aircraft (A) according to one of claims 1 and 2, in which the climb range (PM) is defined between 210° and 330°. Aircraft (A) according to one of claims 1 to 3, in which the climb range (PM) is defined between 225° and 315°.

5. Aircraft (A) according to one of claims 1 to 4, wherein the stator (4) of the turbomachine (1) comprises at least one stator blade (5) having a third chord (C3), called shortened blade (53), the third chord (C3) being smaller than the first chord (Cl) so as to limit the risk of underloading of a blade, said at least one shortened blade (53) is positioned in a descent range (PD), the descent range (PD) being defined between 0° and 180°.

6. Aircraft (A) according to claim 5, wherein each shortened blade (53) is diametrically opposed to an elongated blade (52).

7. Aircraft (A) according to one of claims 5 and 6, in which, the first chord (Cl) having a length, the third chord (C3) having a length between 70% and 95% of the length of the first chord (Cl).

8. Aircraft (A) according to one of claims 1 to 7, in which, the first chord (Cl) having a length, the second chord (C2) having a length between 105% and 130% of the length of the first chord (Cl).

9. Aircraft (A) according to one of claims 1 to 8, in which the chord difference (C) between two adjacent stator blades (5) is less than or equal to 25%.

10. Aircraft (A) according to one of claims 1 to 9, in which, each stator blade (5) having a maximum thickness (Ep) in the plane of revolution (PR), the relative thickness of a stator blade (5) corresponding to the ratio of the maximum thickness (Ep) to the chord (C), the difference in relative thickness between two adjacent stator blades (5) having different chords (Cl, C2, C3), is less than or equal to 25%.

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