STATOR RING OF A TURBOMACHINE WHICH HAS STATOR BLADES WITH DIFFERENT CHORD LENGTHS

Description

DOMAINE TECHNIQUE DE L'INVENTION

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

[0002] As known, with reference to the figure 1 , an aircraft turbomachine 1 extends longitudinally along an axis X and makes it possible to move the aircraft from an air flow 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. Similarly, the terms “inner” and “outer” are defined in the radial direction relative to the axis X.

[0003] The turbomachine 1 comprises a compressor, a combustion chamber and an upstream fan 2, mounted to rotate around the X axis and allowing a flow of air to be sucked into the turbomachine 1. As shown in figure 1 , the turbomachine 1 comprises an outer casing 11 in which the fan 2 is mounted and an intermediate casing 12, delimiting a primary vein V1, internal to the intermediate casing 12, and a secondary vein V2 between the intermediate casing 12 and the outer casing 11. During operation of the turbomachine 1, the fan 2 makes it possible to generate an air flow from upstream to downstream which is decomposed into a first air flow F1 circulating in the primary vein V1 and making it possible to supply the compressor and a second air flow F2 circulating in the secondary vein V2 so as to be ejected downstream of the turbomachine 1.

[0004] In a known manner, in order to straighten the second air flow F2 which has been twisted by the rotation of the fan 2, the turbomachine 1 comprises at least one stator wheel comprising a plurality of stator vanes 3, also referred to as “straighteners”, mounted radially and spaced regularly in the secondary duct V2 of the turbomachine 1 between the intermediate casing 12 and the outer casing 11. These stator vanes 3 are known to those skilled in the art by their English acronym OGV for “Outlet Guide Vane”. Such a stator wheel is for example known from patent application FR3004749. FR2681644A1, US2011 / 255964A1 and FR3032495A1 also disclose a stator wheel.

[0005] A main function of a stator wheel is to modify the direction of the second air flow F2 in order to modify the kinetic energy so that it can be used for the thrust of the turbomachine 1. The stator wheel thus makes it possible to reduce aerodynamic losses, ensure good efficiency of the turbomachine 1 and guarantee robustness to the incidence of the air flow in order to ensure the operating stability of the turbomachine 1. In a known manner, the stator blades 3 have a precise and predefined geometry making it possible to best ensure the aforementioned functions. The stator blades 3 are dimensioned so as to have a predefined section and orientation to optimize the deflection of the second air flow F2.

[0006] However, a stator wheel can also fulfill a structural, thermal or aerodynamic role. Indeed, the latter can for example be used to improve the recovery and transmission of forces in the turbomachine or the heat exchange between the hot primary air flow F1 circulating inside the intermediate casing 12 and a cold secondary air flow F2 circulating outside said intermediate casing 12.

[0007] In order to ensure these complementary functions, it is necessary to increase the cross-section of the stator blades 3 so as to increase their mechanical stiffness and thus reduce the stresses applied to each one. It is also necessary to increase the surface area in contact with the second air flow F2 so as to maximize the heat flow. The profile of a stator blade 3 determined to ensure heat exchanges thus diverges from the profile enabling optimal aerodynamic performance to be ensured. In a known manner, a stator wheel comprises a plurality of identical stator blades 3 whose profile results from a compromise between aerodynamic and thermal performance. Such a solution is not optimal because it affects the performance of the turbomachine.

[0008] Also, to limit these drawbacks, the invention aims to propose a stator wheel, making it possible to ensure both the rectification function and an aerodynamic, structural and / or thermal function, while avoiding a penalty on the performance of the turbomachine.

[0009] Incidentally, patent application FR3004749 discloses a stator wheel comprising stator blades and thickened stator arms which include ancillaries. Such stator arms cannot be confused with stator blades and have a very significant thickness.

[0010] Patent application FR2681644A1 discloses a turbojet engine for a supersonic aircraft comprising a splitter plane to reduce acoustic waves. The thickness and chord of certain stator blades can be modified. In particular, the length of a blade can be doubled. Documents US 2011 / 255964 A1 and FR3032495 A1 also teach providing some blades whose length is at least doubled. PRESENTATION DE L'INVENTION

[0011] To this end, the invention relates to a stator wheel of a turbomachine according to claim 1.

[0012] Preferably, the chord difference applies to all adjacent blades, i.e., over the entire revolution of the stator blade. The chord difference between two adjacent blades 2 by 2 is thus limited overall.

[0013] Such a stator wheel advantageously allows both a role of straightening the second air flow in the secondary vein and a structural, aerodynamic and / or thermal role to be ensured, while limiting the penalty on the performance of the turbomachine. The integration of blades of different chords in fact allows a single blade or a limited number of blades of the wheel to fulfill a secondary role in a specialized manner. In addition, the reduced difference in chords ensures that no local disturbance impacts the flow of the second air flow in the secondary vein. In other words, the wheel according to the invention allows the chord of a limited number of blades to be adapted according to the role it fulfills, without requiring the modification of all the blades which could impact the operation and overall performance of the turbomachine.

[0014] Such a stator wheel goes against established practices which aimed to equip the stator wheel with blades of identical chord values at the same radial distance.

[0015] Preferably, at least one blade has a first minimum chord and at least one blade has a second maximum chord. The stator wheel comprises at least one intermediate blade, mounted between said blades, having a third chord between said first chord and said second chord. The integration of an intermediate blade having an intermediate chord makes it possible to ensure a regular transition of the length of the blades, advantageously making it possible to limit local disturbances of the flow of the second air flow in the secondary vein. Thus, the performance of the stator is not impacted by the geometry of the wheel and the air flow passing through the secondary vein is optimal at the outlet of the turbomachine, making it possible to guarantee good efficiency of the turbomachine.

[0016] More preferably, the stator wheel comprises at least two intermediate blades, mounted between said blades, having different chords between said first chord and said second chord. The use of several intermediate blades is advantageous in order to smooth the transitions between blades having large differences in chords.

[0017] Preferably, the chords increase between said first chord and said second chord so as to allow a progressive transition between the different blade profiles so as to limit local disturbances.

[0018] According to one aspect, the difference in chords between two adjacent blades is greater than or equal to 5%, preferably greater than or equal to 10%, so as to allow the blades to be specialized according to their main role (aerodynamic, thermal, structural, etc.).

[0019] In one aspect, the maximum thickness difference between two adjacent blades having different chords is less than or equal to 5%.

[0020] According to another aspect, the relative thickness of a blade corresponding to the ratio of the maximum thickness to the chord, the difference in relative thickness, between the two adjacent blades having different chords, is less than or equal to 10%.

[0021] The invention also relates to a turbomachine intended to be mounted in an aircraft, the turbomachine extending along an axis, said turbomachine comprising a primary flow stream for circulating a first air flow and a secondary flow stream for circulating a second air flow in which a stator wheel, as presented previously, is mounted along the axis.

[0022] The invention also relates to an aircraft comprising a turbomachine as described previously. PRESENTATION DES FIGURES

[0023] The invention will be better understood on reading the following description, given solely by way of example, and referring to the appended drawings given as non-limiting examples, in which identical references are given to similar objects and in which: There figure 1 is a schematic representation in longitudinal section of a turbomachine according to the prior art; The figure 2 is a schematic representation in longitudinal section of a turbomachine according to the invention; The figure 3 is a sectional view along a plane of revolution of two stator blades; The figure 4 is a sectional view along a plane of revolution of the stator blades of a first embodiment of a stator wheel according to the invention and The figure 5 is a sectional view along a plane of revolution of the stator blades of a second embodiment of a stator wheel according to the invention.

[0024] It should be noted that the figures set out the invention in detail for implementing the invention, said figures can of course be used to better define the invention where appropriate. DESCRIPTION DETAILLEE DE L'INVENTION

[0025] 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.

[0026] A turbomachine according to the invention is presented in the figure 2 . For the sake of clarity and conciseness, identical references are used between the figures 1 et 2 to identify identical or similar characteristics. For this purpose, with reference to the figure 2 , the aircraft turbomachine 1 extends longitudinally along an axis X and makes it possible to move the aircraft from an air flow 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. Similarly, the terms “inner” and “outer” are defined in the radial direction relative to the longitudinal axis X.

[0027] As is known, the turbomachine 1 comprises a compressor, a combustion chamber and an upstream fan 2, mounted to rotate around the X axis and allowing an air flow to be sucked in. As shown in figure 2 , the turbomachine 1 comprises an outer casing 11 in which the fan 2 is mounted and an intermediate casing 12, delimiting a primary vein V1, internal to the intermediate casing 12, and a secondary vein V2 between the intermediate casing 12 and the outer casing 11. During operation of the turbomachine 1, the fan 2 makes it possible to generate an air flow from upstream to downstream which is decomposed into a first air flow F1 circulating in the primary vein V1 and making it possible to supply the compressor and a second air flow F2 circulating in the secondary vein V2 so as to be ejected downstream of the turbomachine 1.

[0028] In reference to the figure 2 , in order to straighten the second air flow F2 which has been twisted by the rotation of the fan 2, the turbomachine 1 comprises a stator wheel 4 comprising a plurality of stator vanes 40, also called “straighteners”, mounted radially and spaced regularly in the secondary flow V2 of the turbomachine 1 between the intermediate casing 12 and the outer casing 11. These stator vanes 40 are known to those skilled in the art by their English acronym OGV for “Outlet Guide Vane”. In this example, the stator wheel 4 comprises an outer shroud 41, belonging to the outer casing 11, and an inner shroud 42, belonging to the intermediate casing 12. The stator vanes 40 extend radially between the outer shroud 41 and the inner shroud 42 as illustrated in figure 2 .

[0029] As known, with reference to the figure 3 , each stator blade 40 comprises a leading edge 40A, corresponding to the end located upstream and first coming into contact with the second air flow F2, and a trailing edge 40B, located downstream. In a known manner, a blade 40 has a profile which is determined, in section, in a plane of revolution PR around the axis X of the turbomachine 1 shown in the figure 2 . A plane of revolution PR is determined for a predetermined radial distance.

[0030] By stator blade 40, we mean a conventional stator blade and not a passage member of a rotating shaft crossing the secondary vein V2.

[0031] In the PR revolution plan, with reference to the figure 3 , each blade 40 has a profile P elongated from the leading edge 40A to the trailing edge 40B. 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 blade 40 is characterized by the distance between the leading edge 40A and the trailing edge 40B, 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 blade LMA. As illustrated in figure 3 , this mean line LMA (also known to those skilled in the art as the skeleton line or camber line) connects the leading edge 40A to the trailing edge and is equidistant from the intrados and the extrados. Similarly, still with reference to the figure 3 , a blade 40 is characterized by the inclination of its chord P relative to the axis X of the turbomachine 1 (the axis of revolution). Subsequently, for a profile P, a setting angle θ is defined between the axis X and the chord C. Finally, a stator wheel 4 is characterized by its pitch PAS corresponding to the spacing between the trailing edges 40B of two adjacent stator blades 40 as illustrated in figure 3 .

[0032] Subsequently, a first profile P1 of a blade 40 is defined which is determined to fulfill an aerodynamic function and straighten the air flow and a second profile P2 of a blade 40 is defined which is determined to fulfill a thermal function and improve the heat exchanges between the primary air flow F1 circulating inside the intermediate casing 12 and the second air flow F2 circulating outside the intermediate casing 12 of the turbomachine 1.

[0033] As presented in the prior art, when a stator wheel 4 is configured to fulfill only an aerodynamic role, it comprises only blades having a first aerodynamic profile P1. Similarly, when a stator wheel 4 is configured to fulfill only a thermal role, it comprises only blades having a second thermal profile P2. In such a stator wheel, the pitch PAS is also identical between two adjacent blades 40.

[0034] According to the invention, in order for the stator wheel 4 to fulfill a thermal and aerodynamic role, while limiting the impact on the performance of the turbomachine 1, the stator wheel 4 comprises at least two blades 40 having a different chord C. The profile P of a blade 40 is directly proportional to the chord C of such a blade 40. Also, an increase in the chord C leads to an increase in the section, making it possible, for example, to lower the mechanical stresses on the blades 40 of the wheel. Similarly, an increase in the chord C leads to an increase in the volume of the blade 40, which advantageously makes it possible to increase the surface area in contact with the air flow entering the turbomachine 1, thus maximizing heat exchanges.

[0035] According to one aspect, the profile P of the blades 40 between the leading edge 40A and the trailing edge 40B has a maximum thickness Ep that is substantially identical for the two blades 40 having different chords C. Preferably, the maximum thickness Ep is defined at a position between 20% and 70% of the chord C, considering that 0% corresponds to the position of the leading edge 40A and that 100% corresponds to the position of the trailing edge 40B. By maximum thickness Ep that is substantially identical, we mean a variation in the maximum thickness Ep that is less than 5%. Thus, a variation in chord with constant maximum thickness is obtained.

[0036] According to another aspect, the profile P of the blades 40 between the leading edge 40A and the trailing edge 40B has a substantially identical relative thickness for the two blades 40 having different chords C. The relative thickness is defined as the ratio of the maximum thickness Ep to the chord C. By substantially identical relative thickness, we mean a variation in the relative thickness which is less than 10%. Thus, a chord variation with constant relative thickness is obtained. Preferably, the ratio of the relative thickness of a blade with an elongated chord to the relative thickness of a blade with a normal chord is less than 1.1. Such a ratio makes it possible to limit local disturbances of the flow between two adjacent blades with different chords.

[0037] In reference to the figure 4 , in the plane of revolution PR, there are shown 7 blades 40 having a first aerodynamic profile P1 of first chord C1 and a single blade 40 having a second thermal profile P2 of second chord C2. In this example, the second chord C2 is longer than the first chord C1 so as to maximize heat exchanges. Contrary to the general practice which required always using blades 40 having an identical chord, the present invention takes the opposite view of the prior art and proposes to specialize certain blades 40 so that they implement their function optimally.

[0038] Preferably, the difference in chord C1, C2 between two adjacent blades 40 is less than 50%, more preferably less than 25%. Such a characteristic allows a variation of the aerodynamic / thermal characteristics that is substantially continuous, which makes it possible not to affect the performance of the turbomachine 1, in particular the local performance of the flow in the vicinity of the blade 40 having a second thermal profile P2 of second chord C2. Preferably, the difference in chord C1, C2 between two adjacent blades 40 is greater than 5%, more preferably greater than 10% so as to specialize the blades 40.

[0039] Depending on the type of turbomachine, when the first chord C1 of the first aerodynamic profile P1 is too far from the second chord C2 of the second thermal profile P2, one solution is to provide intermediate blades 40 having intermediate profiles P31, P32.

[0040] Two profiles, P1 and P2, were presented to optimize, on the one hand, aerodynamic performance and, on the other hand, thermal performance. It goes without saying that other specialized profiles could be planned, in particular, to optimize mechanical and structural performance.

[0041] In reference to the figure 5 , there are presented intercalary blades 40 having a first intercalary profile P31 of first intercalary chord C31 and intercalary blades 40 having a second intercalary profile P32 of second intercalary chord C32. In this embodiment, the chords are ordered in increasing order according to this sequence: C1 (smallest chord), C31, C32, C2 (largest chord). The chord variation is increasing between the minimum chord C1 and the maximum chord C2. In this example, the chord difference between two adjacent blades 40 is less than 50%, more preferably less than 25%.

[0042] In practice, as will be presented later, the number of intermediate blades 40 between a blade 40 of first profile P1 and a blade 40 of second profile P2 is defined as a function of the difference between the first chord C1 and the second chord C2 and the acceptable difference in chord C between two adjacent blades 40.

[0043] As illustrated in the figure 5 , the profiles of the blades 40 are arranged consecutively according to the following sequence of chords: C1, C1, C31, C32, C2, C32, C31, C1, C1. Such a sequence is advantageous because it makes it possible to integrate a blade 40 having a second thermal profile P2 among a set of blades 40 having a first aerodynamic profile P1 which is distant from the second thermal profile P2. The use of intermediate blades 40 advantageously makes it possible to avoid any discontinuity in the thermal and aeronautical treatment so as not to disturb the operation of the turbomachine 1. The evolution of chord is advantageously progressive.

[0044] The stator wheel 4 according to the invention advantageously makes it possible to ensure the straightening of the air flow and to guarantee the required mechanical role, while limiting the difference in chords C between two adjacent blades 40. This advantageously makes it possible to ensure a regular transition between the profiles of the blades 40 making it possible to limit the disturbances of the second air flow F2.

[0045] In this example, two types of intercalary blades 40 have been presented but it goes without saying that their number could be different.

[0046] Preferably, a stator wheel 4 according to the invention comprises a limited number of blades 40 having a different chord C. Indeed, in order to advantageously limit manufacturing and assembly constraints, such a stator wheel 4 comprises a maximum of ten blades 40 having different chords C.

[0047] A first aerodynamic profile P1 and a second thermal profile P2 having different chords C1, C2 have been presented. It goes without saying that the first aerodynamic profile P1 and the second thermal profile P2 could comprise one or more other different characteristics, in particular, the maximum thickness Ep, the pitch PAS, the pitch angle θ.

[0048] According to one aspect, the first aerodynamic profile P1 and the second thermal profile P2 have chords C1, C2 which are different but have the same maximum thickness Ep so as to limit the variation in section between two adjacent blades 40, which limits local disturbances of the flow.

[0049] According to another aspect, the first aerodynamic profile P1 and the second thermal profile P2 have chords C1, C2 which are different and maximum thicknesses Ep which are different so as to have constant relative thicknesses, that is to say a ratio between the maximum thickness EP and the chord C of the blade 40, which is constant. Such an alternative makes it possible to guarantee the mechanical characteristics of the profiles P1, P2 (flexibility, natural frequency, etc.).

[0050] In the preceding example, the chord of a blade 40 is defined as a function of the chords C of the adjacent blades 40. However, it goes without saying that the chord C of each blade 40 could just as well be fixed independently of the chord C of the adjacent blades 40 on the stator wheel 4. According to such an alternative, the geometry of each blade 40 is unique and allows an optimal configuration of the stator wheel 4 according to the performance requirements.

[0051] Preferably, the pitch PAS between two blades 40 is independent of the chord C, so if the pitch PAS is identical but the chord C is different between two adjacent blades 40, 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 blades 40. Alternatively, the pitch PAS between two blades 40 having different chords C may be different (as shown in the figure 5 presenting a first step PAS1 and a second step PAS2).

[0052] Optionally, the variation of chord C between two blades 40 can be coupled with a variation of the pitch angle θ of the blades 40 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 wheel of the stator 4, for example when the aircraft is in flight.

[0053] It was presented with reference to the figure 5 a stator wheel 4 comprising several blades 40 of first aerodynamic profile P1 and a single blade 40 of second thermal profile P2. It goes without saying that the invention also applies to a stator wheel 4 comprising several blades 40 of second thermal profile P2 and a single blade 40 of first aerodynamic profile P1. Similarly, two profiles P1, P2 have been presented in order to optimize, on the one hand, the aerodynamic performances and, on the other hand, the thermal performances. It goes without saying that other specialized profiles could be provided, in particular, to optimize the mechanical and structural performances.

[0054] The integration of a stator wheel 4 comprising blades 40 having different chords C has the advantage of allowing the wheel to perform an aerodynamic, structural, and thermal role, while limiting the penalty on the performance of the turbomachine 1, which would appear if all of the blades 40 were identical.

Claims

1. Stator wheel (4) of a turbomachine (1) configured to be mounted in an aircraft, the turbomachine (1) extending along an axis (X), the turbomachine (1) comprising a core flow stream (V1) for a first air flow and a bypass flow stream (V2) for a second air flow, wherein the stator wheel (4) is configured to be mounted along the axis (X), the stator wheel (4) comprising a plurality of vanes (40) extending radially from the axis (X), each vane (40) comprising a leading edge (40A) and a trailing edge (40B) that together define a chord (C1, C2, C31, C32) in a plane of revolution (PR) defined relative to the axis (X), the stator wheel (4) being characterized by the fact that at least two vanes (40) have different chords (C1, C2, C31, C32) at a same radial distance, the difference in chords (C1, C2, C31, C32) between each vanes (40) of the plurality of vanes (40) and the adjacent vane (40) to said vane (40) being less than or equal to 25%.

2. Wheel according to claim 1, wherein at least one vane (40) has a first minimum chord (C1) and at least one vane (40) has a second maximum chord (C2), the stator wheel (4) comprises at least one interleaved vane (40), mounted between said vanes (40), having a third chord (C31, C32) between said first chord (C1) and said second chord (C2)3. Wheel according to claim 2, wherein the stator wheel (4) comprises at least two interleaved vanes (40) having different chords (C31, C32) between said first chord (C1) and said second chord (C2).

4. Wheel according to one of claims 2 to 3, wherein the chords (C1, C31, C32, C2) increase between said first chord (C1) and said second chord (C2).

5. Wheel according to one of claims 1 to 4, wherein the difference in chords (C1, C2, C31, C32) between two adjacent vanes (40) is greater than or equal to 5%.

6. Wheel according to one of claims 1 to 5, wherein the difference in chords (C1, C2, C31, C32) between two adjacent vanes (40) is greater than or equal to 10%.

7. Wheel according to one of claims 1 to 6, wherein the difference in the maximum thickness between two adjacent vanes with different chords (C1, C2, C31, C32) is less than or equal to 5%.

8. Wheel according to one of claims 1 to 7, wherein, the relative thickness of a vane corresponding to the ratio of the maximum thickness Ep and the chord (C1, C2, C31, C32), the difference in the relative thickness between two adjacent vanes with different chords (C1, C2, C31, C32) is less than or equal to 10%.

9. Wheel according to one of claims 1 to 8, wherein the difference in chords (C1, C2, C31, C32) applies to all adjacent vanes, in other words to the entire revolution of the stator wheel (4).

10. Turbomachine (1) configured to be mounted in an aircraft, the turbomachine (1) extending along an axis (X), said turbomachine (1) comprising a core flow stream (V1) for circulation of a first air flow (F1) and a bypass flow stream (V2) for circulation of a second air flow (F2) wherein a stator wheel (4) according to one of claims 1 to 9, is mounted along the axis (X).

11. Aircraft comprising a turbomachine (1) according to claim 10.