FR3079552A1 - TURBOMACHINE COMPRISING AT LEAST ONE UPPER DAWN COMPRISING A BLOWING PORTION TO LIMIT THE RESONANCE OF A DAWN AVAL - Google Patents

Abstract

An aircraft turbine engine (1) extending longitudinally along an axis (X) and configured to allow the circulation of an air flow (F) in the turbomachine (1) from upstream to downstream, the turbomachine (1) ) comprising at least one row of upstream vanes (2B) and at least one row of downstream vanes (3A) arranged directly downstream of the upstream vane row (2B), at least one downstream vane (3A) comprising at least one least one resonance portion (4), each resonance portion (4) having structure modes defining a plurality of eigenfrequencies, the turbomachine (1) inducing a vibratory excitation frequency on the resonance portion (4), the vibratory excitation frequency being a function of the speed of the turbomachine (1), each upstream blade (2B) comprising at least one blowing portion (5) configured to modify the wake of the upstream blade (2B).

Description

TURBOMACHINE HAVING AT LEAST ONE UPSTREAM VANE PROVIDED WITH A BLOWING PORTION TO LIMIT THE RESONANCE OF A DOWNSTREAM VANE

GENERAL TECHNICAL AREA AND PRIOR ART

The present invention relates to a turbomachine and, more particularly, upstream blades of a turbomachine whose structure is improved to avoid the vibrational resonance of the downstream blades.

In known manner, a turbomachine extends longitudinally and makes it possible to move an aircraft from an air flow entering the turbomachine and circulating from upstream to downstream. Thereafter, the terms “upstream” and “downstream” are defined with respect to the axis of the turbomachine oriented from upstream to downstream. A turbomachine comprises a plurality of rows of blades which are axially spaced apart, in particular, an alternation of rows of moving blades and rows of fixed blades.

During the operation of the turbomachine, each row of blades perceives fluctuations in the aerodynamic field caused by the row of blades located directly upstream. These aerodynamic fluctuations can in particular come from wakes from the upstream row of blades. These fluctuations in the aerodynamic field induce a vibrational oscillation force on the row of downstream blades. This oscillation force is correlated with the speed of rotation of the turbomachine. When the speed of rotation is zero, there is no vibrational oscillation force.

The vibrational oscillation force has an excitation frequency which depends on the speed of rotation of the turbomachine. When the excitation frequency is close to a natural frequency of one of the modes of the structure of the downstream row of blades, a resonance phenomenon appears and the amplitudes of the vibratory oscillation force increase sharply, which can lead to a premature wear or rupture of the downstream vanes, which has a drawback in terms of the performance of the turbomachine.

One objective is to reduce the resonance phenomena over the range of rotational speed of the turbomachine in order to guarantee a long lifetime of the blades of the turbomachine.

Incidentally, there are known in the prior art from patent applications EP2806156B1, US5791601, US5480284, US6004095 FR2927674, several technical solutions making it possible to improve the aerodynamic behavior of a predetermined blade, in particular, in order to reduce the noise generated by a row of movable blades. However, these technical solutions do not allow the blades located upstream and / or downstream to be taken into account and cannot guarantee an aerodynamic flow devoid of resonances over the range of rotational speed of the turbomachine.

GENERAL PRESENTATION OF THE INVENTION

To this end, the invention relates to an aircraft turbomachine extending longitudinally along an axis X and configured to allow the circulation of an air flow in the turbomachine from upstream to downstream, the turbomachine comprising at least one row. upstream blades and at least one row of downstream blades disposed directly downstream of the row of upstream blades.

The invention is remarkable in that, each downstream vane comprising at least one resonance portion, each resonance portion having structural modes defining a plurality of natural frequencies, the turbomachine inducing a vibratory excitation frequency on the resonance portion , the vibratory excitation frequency being a function of the speed of the turbomachine, at least one upstream blade comprises at least one blowing portion, located substantially at the same radial distance from the axis X of the turbomachine of the resonance portion. The blowing portion is advantageously configured to modify the wake of the upstream vane in order to distance the vibratory excitation frequency from the natural frequencies of the resonance portion of the downstream vane and / or reduce the amplitude of the frequency d vibratory excitation.

Since the blowing portion is located substantially at the same radial distance from the resonance portion, the blowing portion and the resonance portion are located in the same portion of current line in the air flow in row d 'upstream blade and the row of downstream blades considered.

It should be noted that the vibrational excitation frequencies result from the vibratory excitation forces produced by the wake of the upstream dawn.

Thanks to the blowing portion, the pressure losses associated with the wake of the upstream vane are limited, which reduces pressure fluctuations downstream of the downstream vane. Thanks to the invention, the phenomenon of resonance is treated indirectly by acting on the source of excitation. In addition, the blowing portion makes it possible to modify the pressure around the upstream vane, which makes it possible to stabilize it and reduce the floating phenomenon.

Preferably, the upstream vane having a leading edge and a trailing edge, the blowing portion is formed on the trailing edge. Thus, the wake of the upstream dawn is modified, which only impacts the aerodynamic flow for the downstream dawn.

More preferably still, the trailing edge comprising a lower surface and an upper surface, the blowing portion comprises a plurality of orifices connecting the lower surface to the upper surface so as to allow air to be blown from the upper surface to the lower surface . Such a solution makes it possible not to require additional sampling of air in the turbomachine, which improves performance. Thus, the trailing edge considered is on a blade end section, over a certain length of blade line, without considering only a simple trailing edge edge of the blade.

Still preferably, the upstream blade has a main body and a trailing edge which is attached to said main body. An added trailing edge makes it possible to form through orifices without constraint, in particular when the main body is made of composite material. Just choose the appropriate trailing edge to limit the resonances.

Advantageously, each downstream vane having a leading edge and a trailing edge, the resonance portion is formed on the leading edge.

In one aspect, the upstream vanes are stator vanes while the downstream vanes are rotor vanes. Preferably, each upstream stator blade comprising a foot mounted in an internal casing and a head mounted in an external casing, the blowing portion comprises a plurality of elementary pipes which are supplied with air by a pressurized air enclosure of the casing outside.

According to another aspect, the upstream blades are rotor blades while the downstream blades are stator blades. Preferably, each upstream rotor blade comprising a foot mounted in a rotary disc of the turbomachine, the blowing portion comprises a plurality of elementary channels which are supplied with air by supply channels of the rotary disc.

In general, it has been indicated that at least one upstream vane comprises at least one blowing portion, located substantially at the same radial distance from the axis of the turbomachine of the resonance portion, the blowing portion being configured to modify the wake of the upstream dawn regarding the number of blades affected by the change. In particular, this wake treatment by blowing portion may relate to an upstream blade, a plurality of upstream blades or all of the upstream blades in a row considered.

Thus, according to one aspect of the invention, a plurality of upstream vanes comprises at least one blowing portion, preferably, each upstream vane comprises at least one blowing portion.

Advantageously, the number of blades comprising a blowing portion as well as the arrangement of the blades comprising a blowing portion can be advantageously configured. For example it is possible to consider a pattern on 360 degrees: for example 1 dawn on 2 or 1 dawn on 3. The pattern can be periodic or non-periodic. It is thus possible to modify the excitation spectrum and therefore to attenuate the vibratory response for the row of downstream vanes.

Preferably, each downstream blade has a blowing portion. Thus, a downstream blade can, on the one hand, be protected against the phenomenon of resonance by an upstream blade and, on the other hand, protect another blade located downstream against the phenomenon of resonance. The protection against resonances is applicable to several stages of the turbomachine.

PRESENTATION OF THE FIGURES

The invention will be better understood on reading the description which follows, given solely by way of example, and referring to the appended drawings in which:

FIG. 1 is a sectional representation of a turbomachine with an upstream rotor blade and a downstream stator blade according to the invention,

FIG. 2 is a sectional representation of a turbomachine with an upstream stator blade and a downstream rotor blade according to the invention,

FIG. 3 is a sectional representation of a turbomachine with an upstream stator blade, an intermediate rotor blade and a downstream stator blade according to the invention, FIG. 4 is a schematic representation of a trailing edge with an orifice crossing to carry out the blowing,

FIG. 5 is a schematic representation of a trailing edge with an internal tube opening into the trailing edge,

FIG. 6 is a schematic representation of a blowing portion for a stator blade and

Figure 7 is a schematic representation of a blowing portion for a rotor blade.

It should be noted that the figures show the invention in detail to implement the invention, said figures can of course be used to better define the invention if necessary.

DESCRIPTION OF ONE OR MORE MODES OF IMPLEMENTATION AND IMPLEMENTATION

Referring to Figure 1, there is shown an aircraft turbomachine 1 extending longitudinally along an axis X and configured to allow the circulation, from upstream to downstream, of an air flow F entering the turbomachine according to the X axis. In a known manner, a turbomachine 1 alternates between rotor blades and stator blades to accelerate an air flow (compressor) or capture its energy (turbine). Each blade has a leading edge and a trailing edge.

According to a first embodiment of the invention, the turbomachine 1 comprises a row of upstream rotor blades 2B and a row of downstream stator blades 3A disposed directly downstream of the row of upstream rotor blades 2B.

In this example, still with reference to FIG. 1, each downstream vane of stator 3A comprises a resonance portion 4.

By resonance portion 4 is meant a portion sensitive to a vibratory oscillation force induced by the wake of a blade located directly upstream. The resonance portion 4 has several modes of structure having at least one natural frequency which is close to an excitation frequency of the vibratory oscillation force over the operating range of the turbomachine. By close, we mean a difference of less than 10% between said natural frequency and the excitation frequency. As indicated previously, when the excitation frequency is close to a natural frequency of one of the modes of the structure of the downstream row of blades, a resonance phenomenon appears and the amplitudes of the vibratory oscillation force increase sharply which can lead to premature wear or rupture of the downstream blades 3A, which has a drawback in terms of the performance of the turbomachine via, for example, the problems of dimensioning and / or predicting the service life of the blades.

Preferably, for each downstream vane 3A, the resonance portion or portions 4 are determined by comparing the excitation frequency over the operating range of the turbomachine 1 with the natural frequencies of the resonance portions 4 of the downstream vane 3A.

A resonance portion 4 potentially forms a weakness for the downstream dawn 3A. An immediate solution would be to modify the structure of each resonance portion 4 so that the natural frequencies of its modes of structure are far from the resonance range. However, such a modification is generally not possible from an aerodynamic or structural point of view. According to the invention, the phenomenon of resonance is treated indirectly by acting on the source of excitation.

Thereafter, each resonance portion 4 is located at a determined radial distance R4 from the axis X of the turbomachine 1 and receives an incident air flow F4 from the blade located directly upstream as illustrated in FIG. 4. In the air flow of the blowing portion and the resonance portion, the radial distance corresponds in particular to the same portion of the air flow stream line in the upstream blade row and the blade row downstream considered.

According to the invention, with reference to FIG. 1, each upstream vane 2B comprises a blowing portion 5 configured to emit a plurality of elementary air flows F _e and thus modify the wake of each upstream vane 2B. The blowing portion 5 and the resonance portion 4 are located substantially at the same radial distance R4 from the axis X of the turbomachine 1, that is to say in the same portion of the current line, so that the elementary fluxes F _e form a vibratory oscillation force whose excitation frequency is distant from the natural frequency or frequencies of the structure of the resonance portion 4 over the operating range of the turbomachine 1. In addition, the amplitude of the excitation frequency is reduced.

In this example, with reference to FIG. 1, the downstream vane of stator 3A comprises a resonance portion 4 situated halfway up the downstream vane of stator 3A, in particular, at a radial distance R4. The upstream rotor blade 2B has a blowing portion 5 which is located at the same radial distance R4, that is to say, in the same portion of the current line. During the rotation of the upstream rotor blade 2B, the upstream air flow F is accelerated, which induces a wake impacting the downstream blade of stator 3A and, more particularly, its resonance portion 4. Advantageously , the blowing portion 5 generates a plurality of elementary flows F _e at the radial distance R4 from the resonance portion 4 in order to modify the wake of the upstream rotor blade 2B, which advantageously avoids any phenomenon of vibrational resonance on the portion resonance 4 which is thus protected. The vibration excitation frequency is distant from the natural frequencies of the resonance portion 4 of the downstream vanes 3A while decreasing the amplitude of the vibration excitation frequency.

In this example, the blowing portion 5 is formed on the trailing edge of the upstream rotor vane 2B so as to directly modify the wake of the upstream rotor vane 2B, which effectively limits any resonance phenomenon . In general, the trailing edge considered can be on a blade end section, over a certain length of blade chord, without only considering a trailing edge edge of the blade.

According to a second embodiment of the invention, with reference to FIG. 2, the turbomachine 1 comprises a row of upstream stator vanes 3B and a row of downstream rotor vanes 2A disposed directly downstream of the row of upstream stator vanes 3B.

For the sake of clarity and conciseness, the turbomachine 1 according to the second embodiment is not described again in detail. The elements of the second embodiment, of functions identical or analogous to the first embodiment, are not described again. Only the structural and functional differences between the embodiments are presented below.

In this example, analogously to the first embodiment, each downstream rotor blade 2A comprises a resonance portion 4 at a radial distance R4 from the axis X of the turbomachine 1. Similarly, each upstream stator blade 3B comprises a blowing portion 5 configured to emit a plurality of elementary air flows F _e . The blowing portion 5 and the resonance portion 4 are located at the same radial distance R4 from the axis X of the turbomachine 1, in the same portion of the current line, so that the elementary flows F _e form a vibratory oscillation force whose excitation frequency is far from the natural frequency or frequencies of the structure of the resonance portion 4 of the downstream rotor blade 2A over the operating range of the turbomachine 1.

When the upstream air flow F is deflected by the upstream stator vane 3B, this induces a wake impacting the downstream rotor vane 2A during its rotation and, more particularly, its resonance portion 4. From advantageously, the blowing portion 5 generates a plurality of elementary flows F _e at the same radial distance R4 as the resonance portion 4 in order to modify the wake of the upstream stator vane 3B, which advantageously avoids any resonance phenomenon vibration on the resonance portion 4 which is thus protected.

In other words, the invention makes it possible to protect both a downstream stator blade 3A (Figure 1) and a downstream rotor blade 2A (Figure 2).

According to a third embodiment of the invention, with reference to FIG. 3, the turbomachine 1 comprises a row of upstream stator vanes 3B and a row of intermediate rotor vanes 2C disposed directly downstream of the row of upstream stator vanes 3B. The turbomachine 1 further comprises a row of downstream stator vanes 3A disposed directly downstream of the row of intermediate rotor vanes 2C.

For the sake of clarity and conciseness, the turbomachine according to the third embodiment is not described again in detail. The elements of the third embodiment, of functions identical or analogous to the first embodiment, are not described again. Only the structural and functional differences between the embodiments are presented below.

This third embodiment is presented in order to highlight the fact that an intermediate blade can include both a resonant portion and a blowing portion. In this example, the intermediate blade is a rotor blade but it goes without saying that the invention also applies to a stator blade.

Still with reference to FIG. 3, the intermediate rotor blade 2C comprises, at its leading edge, a resonance portion 4 at a radial distance R4 and, at its trailing edge, a blowing portion 5 'at a radial distance R4'.

In this example, analogously to the second embodiment, each upstream stator blade 3B comprises a blowing portion 5 configured to emit a plurality of elementary air flows F _e , the blowing portion 5 and the resonance portion 4 of the intermediate rotor blade 2C are located at the same radial distance R4 from the axis X of the turbomachine 1, in the same portion of the current line, so that the elementary flows F _e form a force d 'vibration oscillation, the excitation frequency of which is distant from the natural frequency or frequencies of the structure of the resonance portion 4 of the intermediate rotor blade 2C over the operating range of the turbomachine 1.

Similarly to the first embodiment, the downstream vane of stator 3A has a resonance portion 4 'situated halfway up the downstream vane of stator 3A, in particular, at a radial distance R4'. The intermediate rotor blade 2C has a blowing portion 5 'situated at a radial distance R4'. During the rotation of the intermediate rotor blade 2B, the upstream air flow is accelerated, which induces a wake impacting the downstream blade of stator 3A and, more particularly, its resonance portion 4 '. Advantageously, the blowing portion 5 ′ generates a plurality of elementary flows F _e ′ at the radial distance R4 ′ in order to modify the wake of the intermediate rotor blade 2C, which advantageously avoids any phenomenon of vibrational resonance on the resonance portion 4 'which is thus protected.

Advantageously, the invention is applied to several successive blades spaced along the axis X so as to limit any resistance phenomenon during the circulation of an air flow F from upstream to downstream in the turbomachine 1.

Each blowing portion 5 is configured to emit a plurality of elementary flows F _{e in} order to form an incident air flow F4 for the resonance portion 4 which is not likely to cause it to vibrate.

Each blowing portion 5 can have a diverse structure to accomplish its function. By way of example, there is shown in FIG. 4 a blowing portion 5 for an upstream stator vane 3B. The trailing edge 33B of the upstream stator vane 3B comprises an intrados INT and an extrados EXT. The trailing edge considered is on a blade end section, over a certain length of blade chord, without considering only one edge of the trailing edge of the blade. The blowing portion 5 comprises a plurality of orifices 34 connecting the intrados INT to the extrados EXT so as to allow the circulation of an elementary air flow F _e from the extrados EXT towards the intrados INT. Such a modification of the trailing edge 33B makes it possible to locally modify the wake of the upstream stator vane 3B. Preferably, the upstream stator vane 3B has a trailing edge 33B which is mounted in an attached manner on a main body forming the upstream stator vane 3B. This advantageously makes it possible to form the main body of the stator vane 3B without stress linked to blowing (main body made of composite material in particular) and to be able to adapt a trailing edge 33D comprising orifices 34 placed judiciously to reduce the aerodynamic impact on the blades located downstream. In other words, this implementation offers increased flexibility to limit the vibrational excitation of the downstream blades.

The through holes 34 have been presented for a downstream stator vane 3B but this embodiment also applies to a downstream rotor vane 2B. The advantage of such an embodiment is that it does not require air to be drawn from the turbomachine 1, which would reduce performance.

Alternatively, with reference to FIG. 5, there is shown a downstream vane of stator 3B comprising an internal tube 51 opening onto the trailing edge 33B at an outlet orifice 510. Unlike the embodiment of the FIG. 4, each internal pipe 51 takes air outside the upstream incident air flow in order to modify its wake.

FIG. 6 shows a blowing portion 5 comprising a plurality of elementary pipes 51 for an upstream vane of the stator 3B. In Figure 7, there is shown a blowing portion 5 comprising a plurality of elementary channels 52 for an upstream rotor blade 2B.

With reference to FIG. 6, the stator vane 3B comprises a foot 30B mounted in an internal casing 6 and a head 31B mounted in an external casing 7. The stator vane 3B comprises a leading edge 32B and an edge leakage 33B. The stator vane 3B comprises a blowing portion 5 which comprises a plurality of elementary tubes 51 which open, on the one hand, into the trailing edge 33B via a plurality of orifices 510 and, on the other hand, into the outer casing 7, in particular in a pressurized air enclosure 70, so as to supply the elementary pipes 51 with a flow of pressurized air modifying the wake of the stator vane 3B.

Advantageously, the plurality of elementary supply pipes 51 of the blowing portion 5 advantageously makes it possible to provide flexibility for dimensioning the radial length AR of the blowing portion 5. In other words, it suffices to adapt the positioning of the outlet orifices 510 of the elementary pipes 51 in order to correct the influence of the wake on the resonance portion 4 of the downstream rotor blade 2A situated directly downstream as illustrated in FIG. 2. According to a preferred aspect, the turbomachine comprises a activation system, electronic or mechanical, of the air sampling by the elementary supply pipes 51. Preferably, the activation system is selective and allows an air sampling to be carried out by a selection of elementary pipes in order to achieve optimal blowing according to the conditions of use of the turbomachine.

With reference to FIG. 7, the rotor blade 2B comprises a foot 20B mounted in a housing 80 of a rotary disc 8 and a free head 21B facing the outer casing 7. The rotor blade 2B has an edge d attack 22B and a trailing edge 23B. The rotor blade 2B comprises a blowing portion 5 which comprises a plurality of elementary channels 52 which open, on the one hand, into the trailing edge 23B via a plurality of orifices 520 and, on the other hand, at the inside the disc 8 for connecting to supply channels 81 formed in the disc 8 so as to supply the elementary channels 52 with a flow of pressurized air modifying the wake of the rotor blade 2B.

Similarly to FIG. 6, the plurality of elementary channels 52 of the blowing portion 5 advantageously makes it possible to provide flexibility for dimensioning the radial length AR of the blowing portion 5. In other words, it suffices to adapt the positioning outlet orifices 520 of the elementary channels 52 in order to correct the influence of the wake on the resonance portion 4 of the downstream rotor blade 2A downstream as illustrated in FIG. 2.

The drawback of the embodiments of FIGS. 5 to 7 is that it requires an air intake from the turbomachine 1, which decreases the performance. 510/520 outlet ports have been shown which are circular but it goes without saying that 510/520 outlet ports in the form of a slot 10 could be suitable.

Thanks to the invention, the resonance phenomenon impacting resonance parts 4 of a downstream vane of a turbomachine 1 is corrected by modifying the vibration oscillation force in a localized manner. In addition, the blowing portion 5 makes it possible to modify the pressure around the upstream blade, which makes it possible to stabilize it and reduce any floating phenomenon.

Claims (11)

1. Aircraft turbomachine (1) extending longitudinally along an axis (X) and configured to allow the circulation of an air flow (F) in the turbomachine (1) from upstream to downstream, the turbomachine ( 1) comprising at least one row of upstream blades (2B, 3B) and at least one row of downstream blades (2A, 3A) disposed directly downstream of the row of upstream blades (2B, 3B), turbomachine (1 ) characterized in that, each downstream vane (2A, 3A) comprising at least one resonance portion (4), each resonance portion (4) having structural modes defining a plurality of natural frequencies, the turbomachine (1) inducing a vibrational excitation frequency on the resonance portion (4), the vibratory excitation frequency being a function of the speed of the turbomachine (1), at least one upstream blade (2B, 3B) comprises at least one blowing portion (5), located substantially at the same radial distance from the axis (X) of the turbomachine (1) of the a resonance portion (4), the blowing portion (5) being configured to modify the wake of the upstream vane (2B, 3B). 2. A turbomachine according to claim 1, in which the upstream vane (2B, 2C, 3B) comprising a leading edge (22B, 32B) and a trailing edge (23B, 33B), the blowing portion (5) is formed on the trailing edge (23B, 33B). 3. A turbomachine according to claim 2, in which the trailing edge (23B, 33B) comprising a lower surface (INT) and an upper surface (EXT), the blowing portion (5) comprises a plurality of orifices (34) connecting the '' pressure surface (INT) to the pressure surface (EXT) so as to allow air to be blown from the pressure surface (EXT) to the pressure surface (INT). 4. The turbomachine according to claim 3, wherein each upstream blade (2B, 3B) comprises a main body and a trailing edge (23B, 33B) which is attached to said main body. 5. Turbomachine according to one of claims 1 to 4, in which each downstream vane (2A, 3A) having a leading edge and a trailing edge, the resonance portion (4) is formed on the leading edge . 6. Turbomachine according to one of claims 1 to 5, in which the upstream vanes (3B) are stator vanes while the downstream vanes (2A) are rotor vanes. 7. A turbomachine according to claim 6, in which each upstream stator blade (3B) comprising a foot (30B) mounted in an internal casing (6) and a head (31 B) mounted in an external casing (7), the blowing portion (5) comprises a plurality of elementary pipes (51) which are supplied with air by a pressurized air enclosure (70) of the external casing (7). 8. Turbomachine according to one of claims 1 to 5, wherein the upstream blades (2B) are rotor blades while the downstream blades (3A) are stator blades. 9. A turbomachine according to claim 8, in which each upstream rotor blade (2B) comprising a foot (20B) mounted in a rotary disc (8) of the turbomachine (1), the blowing portion (5) comprises a plurality elementary channels (52) which are supplied with air by supply channels (81) of the rotary disc (8). 10. Turbomachine according to one of claims 1 to 9, in which a plurality of upstream blades (2B, 3B) comprises at least one blowing portion (5), preferably, each upstream blade (2B, 3B) comprises at least one blowing portion (5). 11. Turbomachine according to one of claims 1 to 10, in which at least one downstream blade (2C) has a blowing portion (5 ’).