Patent ID: 12215607

It should be noted that the figures set out the invention in detail in order to implement the invention, said figures of course being able to be used to better define the invention if necessary.

DETAILED DESCRIPTION

The invention is described in this document with reference to a turbine engine mounted in an aircraft, but it goes without saying that it can be applied to any type of aircraft.

The aircraft A according to the invention is shown inFIGS.1and2. To this end, with reference toFIG.1, the aircraft A (in this example an aeroplane) comprises a turbine engine1extending longitudinally along an axis X and allowing the aeroplane to be moved by an air flow F entering the turbine engine1and circulating from upstream to downstream. Hereafter, the terms “upstream” and “downstream” are defined in relation to the longitudinal axis X running from upstream to downstream.

Still referring to the example inFIG.1, the aircraft A also comprises an aerodynamic obstacle OA close to the turbine engine1, mounted downstream of the latter. The aerodynamic obstacle OA is positioned at least partly in relation with the turbine engine1. The expression “in relation with” means that the aerodynamic obstacle OA and the turbine engine1are aligned with respect to the axis X. The term “aerodynamic obstacle” describes any device or system mounted in the vicinity of the turbine engine1and likely to disturb the air flow F coming from the turbine engine1and circulating from upstream to downstream. By way of a non-limiting example, such an aerodynamic obstacle OA may be a portion of the fuselage, a wing of the aircraft A or any structural device mounted on the aircraft A. In this document, as shown inFIGS.1and2, the aerodynamic obstacle OA is, for example, a connecting pylon connecting the turbine engine1to the aircraft A. This document presents the example of an aerodynamic obstacle OA mounted downstream of the turbine engine1, however it goes without saying that the aerodynamic obstacle OA could be mounted upstream of the turbine engine1.

In a known way, with reference toFIG.2, the turbine engine1comprises a primary vein delimited by a casing, designated “inter-vein casing”2, and supplied by an upstream fan, designated rotor3, mounted so as to rotate about the axis X. The rotor3allows to accelerate the air flow F from upstream to downstream. In practice, the acceleration of the air flow F allows to generate a thrust force that allows the aircraft A to move.

According to the invention, the turbine engine1is unducted, i.e. it has no outer casing. Such a configuration of the turbine engine1is known to those person skilled in the art under the generic name of “open rotor” and will not be described in larger detail in this document.

Still referring toFIG.2, the turbine engine1comprises a stator4, mounted downstream of the rotor3and allowing the air flow F accelerated by the rotor3to be straightened. The stator4comprises a plurality of stator vanes5, also referred to as “flow straightener”, extending radially with respect to the longitudinal axis X between a root5P connected to the inter-vein casing2and a free head5T. In the example shown, the flow air inlet in the primary vein is located between the rotor3and the stator4.

In this embodiment, the turbine engine1comprises only a rotor3and a stator4, to give it a simple, lightweight structure. In addition, the rotor3/stator4pair is mounted upstream of the turbine engine1to form a “puller” type turbine engine. It goes without saying that the rotor3/stator4pair could be mounted downstream of the turbine engine1so as to form a “pusher” type turbine engine.

In a known manner, with reference toFIG.3, each stator vane5comprises a leading edge5A, corresponding to the end located upstream and first coming into contact with the air flow F, and a trailing edge5B, located downstream. Each stator vane5has a profile that is determined, in cross-section, in a plane of revolution PR about the longitudinal axis X of the turbine engine1. The plane of revolution PR is determined for a predetermined radial distance. In practice, each stator vane5comprises a plurality of characteristic profiles, determined in a plurality of planes of revolution about the longitudinal axis X of the turbine engine, along the length of the turbine engine1.

In the plane of revolution PR, with reference toFIG.3, each stator vane5has an elongated profile P from the leading edge5A to the trailing edge5B. In a known way, the profile P is defined according to a plurality of geometric characteristics such as a length and a thickness. In this example, the profile P of a stator vane5is characterised by the distance between the leading edge5A and the trailing edge5B, designated chord C, and the maximum thickness Ep. In this example, the maximum thickness Ep is defined orthogonally to the mean line direction of the vane LMA. As illustrated inFIG.3, this mean line LMA (also known to the person skilled in the art as the skeleton line or camber line) connects the leading edge5A to the trailing edge5B and is equidistant from the pressure side and from the suction side. Similarly, still with reference toFIG.3, a stator vane5is characterised by the inclination of its chord C with respect to the longitudinal axis X of the turbine engine1. Subsequently, for a profile P, a pitch angle α is defined between the longitudinal axis X and the chord C. Finally, a stator4is characterised by its pitch PAS corresponding to the distance between the trailing edges5B of two adjacent stator vanes5as illustrated inFIG.3.

With reference toFIG.4, the stator vanes5are angularly distributed around the longitudinal axis X in a plane PT transverse to the longitudinal axis X, shown inFIG.2. Each stator vane5is defined, in the transverse plane PT, by an angular position θ, within an angular range extending between 0° and 360°. In this example, the angular position 0° is defined as the top position relative to a vertical axis Z extending from bottom to top, as shown inFIG.4. Similarly, the angular positions θ are defined as increasing between 0° and 360° in a clockwise direction of rotation about the longitudinal axis X from the position 0°.

With reference toFIGS.4and5, the stator4comprises, in the transverse plane PT, a plurality of stator vanes5having a first chord C1. Such stator vanes5are referred to as “conventional vanes”51. The first chord C1is preferably between 200 and 600 mm.

The stator4of the turbine engine1according to the invention further comprises a plurality of stator vanes5having a second chord C2, the second chord C2being larger than the first chord C1in the transverse plane PT, as shown inFIG.5. Such stator vanes5are referred to as “elongated vanes”52. Preferably, the second elongated chord C2has a length of between 105% and 130% of the length of the first chord C1. Even more preferably, the length of the elongated second chord C2is between 105% and 115% of the length of the first chord C1. In this example, the stator4comprises a plurality of elongated vanes52, although it goes without saying that the stator4could just as easily comprise a single elongated vane52.

According to the invention, as shown inFIG.4, each elongated vane52is angularly positioned at least partly within an interference angular range PAI, defined in relation with the aerodynamic obstacle OA. In other words, the aerodynamic obstacle OA and the elongated vanes52are aligned, at least partially, with respect to the longitudinal axis X. The elongated vanes52increase the straightening of the air flow from the rotor3in the interference angular range PAI in relation with the aerodynamic obstacle OA, so as to limit disturbances to the air flow F downstream of the turbine engine1in the axis of the aerodynamic obstacle OA. The geometry of each stator vane5is thus adapted according to its load. A longer chord C allows to avoid the overloading of a stator vane5which would be particularly stressed.

In other words, preferably no elongated vane52is positioned entirely within an angular range outside the interference angular range PAI. When a vane is not facing the aerodynamic obstacle OA, it is not subjected to larger disturbances and the air flow does not have to be straightened to a larger extent.

In this example shown inFIG.4, the aerodynamic obstacle OA, i.e. the connecting pylon, extends vertically and is attached to an upper portion of the turbine engine1along a vertical axis Z, i.e. at an angular position of 0°.

In this example, as shown inFIG.4, the stator4comprises three elongated vanes52in the interference angular range PAI, which are either entirely or partially in relation with the aerodynamic obstacle OA.

This document presents the example of a stator4comprising three elongated vanes52, however it goes without saying that the stator4could just as easily comprise a different number of elongated vanes52. In other words, it goes without saying that the interference range PAI could just as easily comprise a single elongated vane52, two elongated vanes52or a number larger than three elongated vanes52. It also goes without saying that the interference range PAI could comprise both conventional vanes51and elongated vanes52.

By way of example, the stator4comprising ten stator vanes5, angularly distributed around the longitudinal axis X, the elongated vanes52corresponding to the stator vanes5in relation with the aerodynamic obstacle OA, cover an angular range of between 315° and 45° in the clockwise direction of rotation as illustrated inFIG.4.

Preferably, the stator4of the turbine engine1also comprises a plurality of stator vanes5having a third chord C3, the third chord C3being smaller than the first chord C1in the transverse plane PT, as shown inFIG.5. Such stator vanes5are referred to as “shortened vanes”53. Preferably, the shortened third chord C3has a length of between 70% and 95% of the length of the first chord C1. Even more preferably, the length of the shortened third chord C3is between 85% and 95% of the length of the first chord C1.

In this example, with reference toFIG.4, each shortened vane53is angularly positioned, in the transverse plane PT, so as to belong to an angular range diametrically opposed to the interference angular range PAI. In particular, in this example, each shortened vane53is diametrically opposed to an elongated vane52. In one embodiment, the stator4comprises a shortened vane53for each elongated vane52. The shortened vanes53allow to balance the assembly of the stator4while limiting the risk of underloading a stator vane5which would be particularly less stressed. This document presents the example of a shortened vane53positioned diametrically opposite each elongated vane52, however it goes without saying that the stator4could also comprise one (or more) shortened vane53which would not be diametrically opposite with an elongated vane52. In particular, in the case of a stator4comprising an odd number of vanes, no diametrically opposed positioning would be achieved.

Preferably, the interference angular range PA1has no shortened vane53, so as to avoid the presence in the interference angular range PAI of a stator vane5which would be overloaded by an air flow disturbed by the presence of the aerodynamic obstacle OA. In other words, each stator vane5positioned in the interference angular range PAI has a chord at least equal to the chord of a conventional vane51and the assembly of the shortened vanes53is positioned outside the interference angular range PAI.

Even more preferably, each vane positioned outside the interference angular range PAI has a chord less than or equal to the chord of a conventional vane51. In other words, the assembly of the stator vanes5positioned outside the interference angular range PAI are conventional vanes51or shortened vanes53. In other words, no elongated vane52is positioned outside the interference angular range PAI.

In this example, as shown inFIG.4, the stator4comprises, in the angular range diametrically opposite with the interference angular range PAI, three shortened vanes53, each positioned diametrically opposite one of the three elongated vanes52.

This document presents the example of a stator4comprising three shortened vanes53, since it comprises three elongated vanes52. However, it goes without saying that the stator4could just as easily comprise a different number of shortened vanes53, for example a single shortened vane53, two shortened vanes53or a number larger than three shortened vanes53.

In one embodiment, the number of elongated vanes52represents less than 50% of the total number of stator vanes5, in the same transverse plane. Preferably, the number of elongated vanes52represents less than 40% of the total number of stator vanes5, in the same transverse plane, preferably less than 30%, even more preferably less than 20% of the total number of stator vanes5in the same transverse plane. In this way, only the stator vanes5present at least partially in relation with the aerodynamic obstacle OA are elongated vanes52, which means that the chord of a stator vane5is not lengthened unnecessarily,

By way of example, as illustrated inFIG.4, the stator4comprises ten stator vanes5angularly distributed around the longitudinal axis X, the elongated vanes52corresponding to the stator vanes5positioned in an angular range between 315° and 45° in the clockwise direction of rotation, the shortened vanes53cover an angular range between 135° and 225° in the clockwise direction of rotation.5FIG.6is a graph showing the change in the chord C1, C2, C3of each stator vane5as a function of its angular position θ, in an example of embodiment. In summary, in this example, over the angular range from 0° to 360°:each stator vane5whose angular position is between 0° and 45° is an elongated vane52,each stator vane5whose angular position is between 45° and 135° is a conventional vane51,each stator vane5whose angular position is between 135° and 225° is a shortened vane53,each stator vane5whose angular position is between 225° and 315° is a conventional vane51, andeach stator vane5whose angular position is between 315° and 360° (i.e.) 0° is an elongated vane52.

This document presents the example in which each angular range comprises similar conventional vanes51, elongated vanes52or shortened vanes53, however it goes without saying that each angular range, as defined above, could just as easily comprise a combination of conventional vanes51and elongated vanes52or a combination of conventional vanes51and shortened vanes53.

Preferably, the chord difference C1, C2, C3between two adjacent stator vanes5is less than 50%, and even more preferably less than 25%. This characteristic means that the performance of the turbine engine1, and in particular the local performance of the flow in the vicinity of each stator vane5, is not affected.

This document presents the example of an aerodynamic obstacle OA extending vertically and being attached to an upper portion of the turbine engine1, i.e. extending around the angular position 0°. However, it goes without saying that the aerodynamic obstacle OA could just as easily extend differently in relation to the turbine engine1, i.e. extend around an angular position β different from 0°, for example to an angular position of the order of 270° (shown inFIG.7).

By way of example, as shown inFIG.7, in the case of a turbine engine1installed under a right wing of the aircraft A for example (the term “right” being understood along a transverse axis Y, in a front view upstream of the aircraft A), the aerodynamic obstacle OA may correspond for example to the fuselage of the aircraft, present to the left of the turbine engine1. In this case, the interference angular range PAI is, for example, between 225° and 315° in the clockwise direction of rotation.

So in this example, over the angular range from 0° to 360°:each stator vane5whose angular position is between 0° and 45° is a conventional vane51,each stator vane5whose angular position is between 45° and 135° is a shortened vane53,each stator vane5whose angular position is between 135° and 225° is a conventional vane51,each stator vane5whose angular position is between 225° and 315° is an elongated vane52, andeach stator vane5whose angular position is between 315° and 360° (i.e.) 0° is a conventional vane51.

This document presents F example of angular ranges comprising vanes of the same type (conventional51, elongated52or shortened53), however it goes without saying that the angular range between 45° and 135° could comprise both one or more conventional vanes51and one or more shortened vanes53and the angular range between 225° and 315° could comprise both one or more conventional vanes51and one or more elongated vanes52.

Similarly, this document presents the example of angular ranges each comprising stator vanes5having the same chord C1, C2, C3, although it goes without saying that the stator4could just as easily comprise a plurality of stator vanes5each having an elongated or shortened chord C of its own. In such a configuration, the stator4would comprise as many values of chords C as there are stator vanes5. Such a stator4would offer optimum performance because each stator vane5would have a chord C adapted to its own environment.

Preferably, the pitch PAS (shown inFIG.3) between two stator vanes5is independent of the chord C, so if the pitch PAS is the same but the chord C is different between two adjacent stator vanes5, then the relative pitch (i.e. the ratio of the pitch PAS to the chord C varies with the chord C) is different between two stator vanes5. Alternatively, the pitch PAS between two stator vanes5with different chords C could be different.

Preferably, the maximum thickness Ep (shown inFIG.3) of the stator vanes5is different depending on whether it is a conventional vane51, an elongated vane52or a shortened vane53so as to present a constant relative thickness (i.e. a ratio between the maximum thickness Ep and the chord C of the stator vane5). This characteristic guarantees the mechanical characteristics of each stator vane5(flexibility, natural frequency, etc.). Alternatively, the conventional vanes51, the elongated vanes52and the shortened vanes53have the same maximum thickness Ep so as to limit the variation in cross-section between two adjacent stator vanes5, thereby limiting the local flow disturbances.

Optionally, the variation in chord C between two stator vanes5can be coupled to a variation in the pitch angle α (shown inFIG.3) of the stator vanes5as described above. Advantageously, such a modification allows to limit the aerodynamic distortion of an airflow applied from downstream to upstream of the turbine engine1on the wheel of the stator4, for example when the aircraft is in flight.

The variable chords on the stator of an unducted turbine engine allow to take advantage of the effects of an aerodynamic obstacle in the vicinity of the turbine engine and its outgoing air flow. Lengthening the chord of the vanes in relation with this aerodynamic obstacle significantly allows to improve the performance of each stator vane, so that the vanes facing the aerodynamic obstacle are more heavily loaded, thereby improving the straightening of the air flow from the rotor and therefore the thrust of the aircraft. A distribution of the conventional vanes, elongated vanes and shortened vanes by angular ranges allows to limit the industrial constraints of stator production and assembly by limiting the number of vanes with different chords, while allowing the loading of each vane to be adapted to its direct environment.

This document describes an aircraft in which a turbine engine comprises stator vanes whose chord is lengthened to adapt the vanes to a larger load due to the presence of an aerodynamic obstacle, but it goes without saying that the chord of the vanes could just as easily be adapted as a function of the load seen by the vanes during the take-off or landing phase or as a function of the load seen by the vanes positioned opposite the rising blades of the rotor during their rotation.