FR3103231A1 - Turbomachine with wavy blades - Google Patents

Abstract

The invention relates to a turbomachine (1) comprising a first bladed wheel (2) of first vanes (21) and a second bladed wheel (3) of second vanes (31), the first bladed wheel (2) being located directly upstream of the second bladed wheel (3), the first vanes (21) comprising a leading edge (21a) and a trailing edge (21b), the second vanes (31) comprising a leading edge (31a) ) and a trailing edge (31b), characterized in that the trailing edge (21b) of at least a first vane (21) comprises a first corrugated zone (22), and in that at least one of the leading edge (31a) and the trailing edge (31b) of at least one second vane (31) comprises a second corrugated zone (32). Figure for the abstract: Fig. 3

Description

Wave blade turbomachine

The present invention relates to the general field of turbomachines, and in particular turbomachines for aircraft.

In turbomachines, the bladed wheels, also called rows of blades, or even paddle wheels, perceive the fluctuations of the aerodynamic field caused by the rotation of the adjacent bladed wheels. The aerodynamic fluctuations come in particular from the wake of the upstream bladed wheel.

These fluctuations in the aerodynamic field excite the blades. When the excitation frequency approaches a natural frequency of one of the blade modes, a resonance phenomenon may appear and thus lead to premature wear of said blades.

The main purpose of the present invention is therefore to reduce the vibratory response of the blades by proposing a turbomachine comprising a first bladed wheel with first blades and a second bladed wheel with second blades, the first bladed wheel being located directly upstream of the second bladed wheel, the first vanes comprising a leading edge and a trailing edge, the second vanes comprising a leading edge and a trailing edge, characterized in that the trailing edge of at least one first vane comprises a first corrugated zone, and in that at least one of the leading edge and the trailing edge of at least one second blade comprises a second corrugated zone.

The wavy zones formed on the first bladed wheel and the second bladed wheel make it possible on the one hand to reduce the excitation of the second bladed wheel by the first bladed wheel by mixing the wake of said first bladed wheel, and on the other hand to reducing the sensitivity of the second bladed wheel to the wake of said first bladed wheel.

In addition, the first corrugation zone and the second corrugation zone make it possible to reduce the flutter, the flutter being the phenomenon caused by the air which enters into resonance around the blades due to the aeroelastic coupling. The reduction of the flutter makes it possible on the one hand to limit the damage to the blades, and on the other hand to reduce the noise caused by the flutter.

The turbomachine may also include the following characteristics, taken alone or in combination according to the technical possibilities:

- the first bladed wheel is mobile and the second bladed wheel is fixed, the second corrugated zone extending between 30% and 70% of a height of the second blades, from a root to a top of said second blades;

- the first bladed wheel is mobile and the second bladed wheel is fixed, the first corrugated zone extending between 70% and 100% of a height of the first blades, from a root to a top of said first blades;

- the first bladed wheel is formed by a fan, and the second bladed wheel is formed by outlet guide vanes;

- which the fan is located upstream of a primary stream and a secondary stream, the outlet guide vanes being located in the secondary stream, the fan comprising a first portion located opposite the primary stream and a second portion located opposite the secondary stream, the first corrugated zone being located only on the second portion of said fan;

- the first corrugated zone has corrugations of variable shape over a height of the at least one first blade;

- the second corrugated zone has corrugations of variable shape over a height of the at least one second blade;

- the first wavy zone has a sinusoidal wave pattern;

- the second wavy zone has a sinusoidal wave pattern;

- a plurality of first vanes comprises a trailing edge which comprises a first corrugated zone;

- all the first blades comprise a trailing edge which comprises a first corrugated zone;

- at least one of the leading edge and the trailing edge of a plurality of second blades comprises a second corrugated zone;

- at least one of the leading edge and the trailing edge of all the second blades comprises a second corrugated zone.

The plurality of first blades comprising its trailing edge having a first corrugated zone may be chosen so that said blades are angularly distributed to avoid unbalance, for example by being diametrically opposed or for example by being angularly separated by sixty degrees of angle or for example one blade out of two or one blade out of three or one blade out of five, for example depending on the number of blades of the first bladed wheel. Even without the appearance of unbalance, a distribution of the same type can be considered for the second blades when they are not all provided with undulation in the second bladed wheel.

Other characteristics and advantages of the present invention will become apparent from the description given below, with reference to the appended drawings which illustrate an example of embodiment devoid of any limiting character.

FIG. 1 is a schematic representation of a first possible embodiment of a turbomachine according to the invention.

FIG. 2 is a schematic representation of a second possible embodiment of a turbomachine according to the invention.

FIG. 3 is a schematic representation of a third possible embodiment of a turbomachine according to the invention.

FIG. 4a schematically represents possible undulation variants.

FIG. 4b schematically represents possible undulation variants.

As illustrated in FIGS. 1, 2 and 3, a turbine engine 1 comprises a first bladed wheel 2 formed by a plurality of first blades 21, and a second bladed wheel 3 formed by a plurality of second blades 31. The first blades 21 and the second vanes 31 are arranged radially around an axis θ of the turbomachine.

The first blades 21 of the first bladed wheel 2 comprise a leading edge 21a, a trailing edge 21b, a root 21c and a crown 21d. The second blades 31 of the second bladed wheel 3 also include a leading edge 31a, a trailing edge 31b, a root 31c and a crown 31d.

The first vanes 21 also comprise a height H2 which corresponds to the distance between the root 21c and the top 21d of said first vanes 21. Similarly, the second vanes 31 comprise a height H3 which corresponds to the distance between the root 31c and the top 31d of said second vanes 31.

The first bladed wheel 2 is located directly upstream of the second bladed wheel 3. The downstream and upstream terms are considered according to the flow of the air flow in the turbomachine 1. Thus, the air flow coming from the trailing edge 21b of the first blades 21 of the first bladed wheel 2 arrives directly on the leading edge 31a of the second blades 1 of the second bladed wheel 3.

In the exemplary embodiments illustrated in FIGS. 1, 2 and 3, the turbomachine 1 is a dual-flow turbomachine with a fan at the air inlet and in particular comprising a secondary-flow stator vane. However, the invention is not limited to a bypass turbomachine, and can be used in other types of turbomachine.

As illustrated in FIGS. 1, 2 and 3, the trailing edge 21b of at least one first blade 21 of the first bladed wheel 2 comprises a first corrugated zone 22. According to a possible variant, a plurality of first blades 21, or well all the first blades 21, may include a first corrugated area 22 on their trailing edge 21b. The wavy zone 22 is formed by local modifications of the length of the chord of the first blades 21 so as to make the trailing edge 21b of said first blades 21 wavy. The chord of the first blades 21 corresponds to the line connecting the edge of attack 21a at the trailing edge 21b.

The first corrugated zone 22 of the trailing edge 21b of the first blades 21 makes it possible to mix the wake of said first blades 21, thus limiting the excitation of the second blades 31 of the second stage 3.

Furthermore, in order to further reduce the risk of resonance of the second blades 31 of the second bladed wheel 3, at least one of the leading edge 31a and the trailing edge 31b of at least one second blade 31 comprises a second corrugated zone 32. According to a possible variant, a plurality of second vanes 31, or else all the second vanes 31, can comprise a second corrugated zone 32 on at least one of the leading edge 31a and the trailing edge 31b. Similar to the first undulating zone 22, the second undulating zone 32 is formed by local modifications of the length of the chord of the second blades 31, so as to undulate the leading edge 31a and/or the trailing edge 31b. The chord of the second blades 3 corresponds to the line connecting the leading edge 31a to the trailing edge 31b. Such wavy edge vanes are sometimes referred to as “serration” vanes.

In a first embodiment illustrated in FIG. 1, the second corrugated zone 32 is located only on the trailing edge 31b of the second blade(s) 31 of the second bladed wheel 3.

In a second embodiment illustrated in FIG. 2, the second corrugated zone is located only on the leading edge 31a of the second blades 31 of the second bladed wheel 3. This configuration is a particularly effective compromise, in particular for the first zone corrugated 22 of blades of a fan and for the second corrugated zone 23 of secondary flow straightener vanes downstream of the fan. The compromise is on the aerodynamic, acoustic efficiency and mechanical strength of the blades. Advantageously, the undulations will be of smaller amplitude in the immediate vicinity of the blade root and/or blade tip serving as a blade attachment connection. Reduced undulation at the fixing connection promotes the mechanical strength of the blade.

In a third embodiment illustrated in FIG. 3, the second corrugated zone is located both on the leading edge 31a and on the trailing edge 31b of the second blades 31 of the second stage 3.

The second corrugated zone 32 makes it possible to limit the sensitivity of the second blades 31 to the vibrations transmitted by the wake of the first blades 21. The corrugations make it possible to generate a phase shift along the height H3 of the second blades 31 in the excitation of said second blades 31 by the pressure waves coming from the first blades 21 of the first stage 2.

The third embodiment illustrated in FIG. 3 and in which the second corrugated zone 32 is located both on the leading edge 31a and the trailing edge 31b of the second blades 31 of the second stage 3 is a preferred embodiment. , the fact that the second corrugated zone 32 is located both on the leading edge 31a and the trailing edge 31b making it possible to transfer the sensitivity of the vibratory response to modes of higher frequencies. The attenuated modes are in particular bending or torsion modes.

In addition, the first corrugated zone 22 and the second corrugated zone 32 make it possible to reduce the flutter phenomenon, thus reducing the wear of the first and second blades 21 and 31, as well as the noise generated by the flutter.

As illustrated in FIGS. 4a and 4b, several corrugation shapes are possible to form the first corrugated zone 22 and the second corrugated zone 32. leak 21a of the first vanes 21. However, FIGS. 4a and 4b could also represent the second corrugated zone 32, the first corrugated zone 22 and the second corrugated zone 32 being similar.

In the first variation illustrated in Figure 4a, the first wavy area 22 has a sinusoidal wave pattern, while in the second variation shown in Figure 4b, the first wavy area 22 has a triangular wave pattern, also called herringbone shape.

Similarly the second corrugated area 32 may also have a sinusoidal wave pattern or may also have a triangular wave pattern.

The sinusoidal pattern of the undulations of the first undulating zone 22 and of the second undulating zone 32 is preferred because such a pattern limits the presence of edges.

The line T illustrated in Figures 4a and 4b is a theoretical line representing the trailing edge 21b if said trailing edge 21b remains straight instead of undulating.

As illustrated in Figures 4a and 4b, the first corrugated zone 22 may have corrugations of variable shape over the height H2 of the first blades 21. In other words, the corrugations are not constant along the first corrugated zone 22.

Similarly, the second corrugated zone 32 may also have corrugations of variable shape over the height H3 of the second blades 31.

The shape of the corrugations of the first corrugated zone 22 and of the second corrugated zone 32 can be modified by varying various parameters. These parameters include ripple pattern, ripple amplitude, and ripple frequency (the inverse of the ripple period). Such a variation of the ripple shape over the height of the blades allows a better adaptation of the wavy zones to the resonance modes to be attenuated.

The first bladed wheel 2 can be mobile, the first blades 21 being driven in rotation around the axis θ, while the second bladed wheel 3 is fixed, the second blades 31 being kept fixed during the operation of the turbine engine 1.

Advantageously, when the first bladed wheel 2 is mobile and the second bladed wheel 3 is fixed, the first corrugated zone 22 extends over the upper part of the first blades 21, between 70% and 100% of the height H21 of said first blades 21 starting from the foot 21c to the top 21d. In other words, 0% of the height H21 corresponds to the root 21c of the first blades 21, and 100% corresponds to the top 21d of said first blades 21.

Such a characteristic makes it possible to provide a compromise between the reduction in performance caused by the first corrugated zone 22, and the effectiveness of the mixing of the wake of the first blades 21.

When the first bladed wheel 2 is mobile and the second bladed wheel 3 is fixed, advantageously the second corrugated zone 32 extends over a median part of the second blades 31, between 30% and 70% of the height H31 of said second blades 31 starting from the foot 31c to the top 31d. In other words, 0% of the height H31 corresponds to the root 31c of the second blades 31, and 100% corresponds to the top 31d of said second blades 31. Thus the undulation is for example over approximately 40% of the height of the second blade being centered about halfway up dawn.

Such a characteristic makes it possible to position the second corrugated zone 32 at the level of the maximum of the deformation of the first modes of resonance of the second blades 32, thus reducing the sensitivity of the second blades 32 to the phenomenon of resonance.

In addition, as illustrated in Figures 1, 2 and 3, the first bladed wheel 2 is formed by a fan and the second bladed wheel 3 is formed by an outlet guide vane wheel (also called "OGV" for "Outlet Guide Vane” according to the Anglo-Saxon terminology). The first vanes 21 are therefore fan vanes, and the second vanes 31 are outlet guide vanes (OGV).

The turbomachine 1 being a dual-flow turbomachine, said turbomachine comprises a primary stream 4 through which the air is compressed before being burned in a combustion chamber, and a secondary stream 5 through which the air bypasses the combustion chamber .

The outlet guide vanes (OGV) are located in the secondary stream 5, thus straightening part of the airflow generated by the rotation of the fan. The turbomachine 1 also includes a low pressure compressor 6 located in the primary stream.

The fan comprises a first portion A which is located opposite the primary vein 4, and a second portion B which is located opposite the secondary vein 5. Thus, the first portion A of the fan is located opposite the low compressor pressure 6, while the second portion B of said fan is located opposite the outlet guide vanes (OGV).

In order to ensure a compromise between the reduction in performance caused by the first corrugated zone 22, and the effectiveness of the mixing of the wake of the blades of the fan, the first corrugated zone 22 is located only on the second portion B of the fan.

Claims (11)

Turbomachine (1) comprising a first bladed wheel (2) of first blades (21) and a second bladed wheel (3) of second blades (31), the first bladed wheel (2) being located directly upstream of the second bladed wheel (3), the first vanes (21) comprising a leading edge (21a) and a trailing edge (21b), the second vanes (31) comprising a leading edge (31a) and a trailing edge (31b) , characterized in that the trailing edge (21b) of at least a first blade (21) comprises a first corrugated zone (22), and in that at least one of the leading edge (31a) and the trailing edge (31b) of at least one second blade (31) comprises a second corrugated zone (32). Turbomachine (1) according to claim 1, in which the first bladed wheel (2) is movable and the second bladed wheel (3) is fixed, the second corrugated zone (32) extending between 30% and 70% of a height (H3) of the at least one second blade (31), from a root (31c) to a top (31d) of said at least one second blade (31). Turbomachine (1) according to any one of Claims 1 to 2, in which the first bladed wheel (2) is movable and the second bladed wheel (3) is fixed, the first corrugated zone (22) extending between 70% and 100% of a height (H2) of the at least one first vane (21), from a root (21c) to a top (21d) of said at least one first vane (21). Turbomachine (1) according to any one of claims 1 to 3, in which the first bladed wheel (2) is formed by a fan, and the second bladed wheel (3) is formed by outlet guide vanes. Turbomachine (1) according to claim 4, in which the fan is located upstream of a primary stream (4) and a secondary stream (5), the outlet guide vanes being located in the secondary stream (5), the fan comprising a first portion (A) located facing the primary stream (4) and a second portion (B) located facing the secondary stream (5), the first corrugated zone (22) being located only on the second portion (B) of said fan. Turbomachine (1) according to any one of Claims 1 to 5, in which the first undulating zone (22) has undulations of variable shape over a height (H2) of the at least one first blade (21). Turbomachine (1) according to any one of Claims 1 to 6, in which the second corrugated zone (32) has corrugations of variable shape over a height (H3) of the at least one second blade (31). A turbomachine (1) according to any one of claims 1 to 7, wherein the first undulating area (22) has a sinusoidal undulating pattern. A turbomachine (1) according to any one of claims 1 to 8, wherein the second corrugated area (32) has a sinusoidal corrugation pattern. A turbomachine (1) according to any of claims 1 to 9, wherein a plurality of first vanes (21) includes a trailing edge (21b) which includes a first corrugated area (22). A turbomachine (1) according to any one of claims 1 to 10, wherein at least one of the leading edge (31a) and the trailing edge (31b) of a plurality of second vanes (31) comprises a second corrugated area (32).