BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood upon reading the detailed description given hereafter of different embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended drawings, in which:

FIG. 1 shows schematically a partial section view of a ducted turbine engine according to the prior art,

FIG. 2 shows schematically a partial section view of an unducted turbine engine according to the prior art,

FIG. 3A shows schematically a partial section view of a ducted turbine engine according to a first embodiment conforming to the invention, and FIG. 3B shows schematically a partial section view of an unducted turbine engine according to the first embodiment,

FIG. 4 shows schematically a side view of an exhaust nozzle of the turbine engine of FIG. 3A,

FIG. 5 shows schematically a side view and a rear view, with respect to the central axis of the turbine engine, of an example of an unducted turbine engine conforming to the first embodiment,

FIGS. 6A to 6H show schematically rear views of the unducted turbine engine of FIG. 5, according to different examples conforming to the first embodiment,

FIGS. 7A to 7F show schematically side views of the exhaust nozzle of the unducted turbine engine of FIG. 5, according to different examples conforming to the first embodiment,

FIG. 8 shows schematically side views of an exhaust nozzle illustrating alternative examples conforming to the first embodiment,

FIG. 9 shows schematically a rear view of the turbine engine of FIG. 3A, according to an example conforming to the first embodiment,

FIG. 10 shows schematically side view of an exhaust nozzle of a turbine engine conforming to a second embodiment,

FIG. 11 shows schematically side views of an exhaust nozzle of a turbine engine conforming to a third embodiment,

FIG. 12 shows schematically side views of an exhaust nozzle of a turbine engine conforming to a fourth embodiment.

DESCRIPTION OF THE EMBODIMENTS

A first embodiment conforming to the present disclosure will be described with reference to FIGS. 3A to 9. In the non-limiting examples described below, the aeronautical propulsion systems are turbine engines. Subsequently in the disclosure, the terms “upstream,” “downstream” and their derivatives are defined with respect to the direction of flow of the gases in the turbine engine along the central axis A of the turbine engine. In addition, the terms “radial,” “circumferential,” “azimuthal direction” and their derivatives are also defined with respect to the central axis A.

FIGS. 3A and 3B show respectively a ducted (of the UHBR or VPF type for example) and unducted (of the CROR or USF type for example) turbine engine, to which a device conforming to the present disclosure can be applied.

In particular, FIG. 3A shows a ducted double flow turbine engine 1, with central rotation axis A. In the same manner as for the turbine engine according to the prior art described with reference to FIG. 1, it comprises in particular a casing 10 of which the inner surface delimits a primary internal flow, and a nacelle 20 of which the inner surface delimits a secondary internal flow. A first exhaust nozzle 12 is arranged at a downstream end of the casing 10, the primary internal flow being ejected through said first exhaust nozzle 12. A second exhaust nozzle 22 is arranged at a downstream end of the nacelle 20, the secondary internal flow being ejected through said second exhaust nozzle 22.

At least one fixed blade of the exhaust casing 40 (called a TRF blade in the rest of the description) is arranged in the primary internal flow, upstream of the first exhaust nozzle 12, more precisely upstream of a trailing edge 122 of the first exhaust nozzle 12. The TRF is the last bladed wheel in the primary internal flow of the turbine engine 1, located downstream of the low-pressure turbine and allowing removing the high-temperature air originating in the combustion chamber and in the high/low pressure turbine stages. The number of TRF blades 40 is typically on the order of 10.

At least one outlet guide vane 30 (called OGV in the rest of the description) is arranged in the secondary internal flow, upstream of the second exhaust nozzle 22, more precisely upstream of a trailing edge 222 of the second exhaust nozzle 22. The OGV is a fixed wheel arranged downstream of the fan 2, in the secondary internal flow of the ducted turbine engine 1, and allowing straightening the gyration of the flow. The number of blades 30 that the OGV wheel comprises can be comprised between 30 and 60. This example is not limiting, the invention being able to be applied to exhaust nozzles arranged downstream of the structural arms, themselves arranged downstream of the OGVs, or integrated with the OGVs.

Moreover, S1 represents the distance between the trailing edge of a blade 40 at its connexion on the inner face of the casing 10, and the point on the trailing edge 122 of the first exhaust nozzle 12 closest to the blade 40, in the direction of the central axis A. C1 is the chord of the blade 40 measured at said connexion. In other words, C1 is the axial distance between the leading edge and the trailing edge of the blade 40 at said connexion. S2 represents the distance between the trailing edge of a blade 30 at its connexion in the outer face of the casing 10, and the point on the leading edge 122 of the first exhaust nozzle 12 closest to the blade 30. C2 is the chord of the blade 30 measured at said connexion. Finally, S2′ represents the distance between the trailing edge of the blade 30 at its connexion on the inner face of the nacelle 20, and the point on the trailing edge 222 of the second exhaust nozzle 22 closest to the blade 30. C2′ is the chord of the blade 30 measured at said connexion.

FIG. 3B shows an unducted double flow turbine engine 1′, with central axis of rotation A. It comprises a casing 10′ the inner surface of which delimits a primary internal flow, and the outer surface of which delimits a secondary outer flow. An exhaust nozzle 12′ is arranged at a downstream end of the casing 10′, the primary inner flow being ejected through said exhaust nozzle 12′.

The turbine engine 1′ comprises an unducted propeller having a plurality of rotor blades 31, preferably with pitch variable around a pitch change axis X1. In the present example, the unducted turbine engine 1′ is of the USF type comprising stator blades 32 arranged downstream of the rotor blades 31. The stator blades 32 (or straighteners, or SRV for “swirl recovery vanes”) are preferably attached with pitch variable around a pitch change axis X2. The invention is nevertheless applicable to fixed pitch stator blades 32. The number of blades 32 is preferably comprised between 5 and 20.

In addition, in the same manner as the ducted turbine engine, at least one fixed TRF blade 40 is arranged in the primary internal flow, upstream of the exhaust nozzle 12′, more precisely upstream of a trailing edge 122′ of the exhaust nozzle 12′.

Moreover, S1 represents the distance between the trailing edge of a blade 40 at its connexion on the inner face of the casing 10′, and the point of the trailing edge 122′ of the exhaust nozzle 12′ closest to the blade 40, in the direction of the central axis A. C1 is the chord of the blade 40 measured at its connexion. Likewise, S2 represents the distance between the trailing edge of a blade 32 at its connexion on the outer face of the casing 10′, and the point on the trailing edge 122′ of the exhaust nozzle 12′ closest to the blade 32. C2 is the chord of the blade 32 measured at said connexion.

Each of the turbine engines conforming to the present disclosure and shown in FIGS. 3A and 3B are large diameter turbine engines, having a main diameter D, which can be the diameter of the fan in the case of the ducted turbine engine, or the diameter of the upstream rotor in the case of the unducted turbine engine, such that D≥1.5 m. In addition, the dimensions Si (where Si=S1, S2 or S2′) and Ci (where Ci=C1, C2 or C2′) are such that the ratio Si/Ci is comprised between 0 and 15. Preferably Si/Ci<5. The value of this ratio allows reducing the distance between the stator blades 30, 32, 40 and the outlet plane of the nozzles. Nevertheless, this also favors an increase in the jet noise.

Thus, for reducing the jet noise, the exhaust nozzles conforming to the present disclosure comprise, along their trailing edge, a plurality of chevrons 4 distributed circumferentially around the central axis A, showing both the central axis of the nozzle 12, 12′, 22 and the axis of rotation of the turbine engine 1, 1′. FIG. 4 shows a trailing edge 122 of the exhaust nozzle 12 of FIG. 3A. This example is not limiting and could be applied in the same manner to the exhaust nozzle 22 of the nacelle 20, or to the exhaust nozzle 12′ of the unducted turbine engine 1′.

A chevron 4 corresponds to an irregularity along the trailing edge 122, characterized by the presence of a protrusion and/or of a notch, with respect to a reference plane P defined by the trailing edge 122 in the case where the latter would not comprise any chevron. It will be noted that the reference plane P forms an angle α with respect to the central axis A, the angle α being able to be equal to 90° or different from 90°, in such a manner that the outlet plane of the nozzle can be inclined relative to the central axis A. Preferably, the angle α is comprised between 40° and 140°. In addition, the chevrons 4 can extend downstream parallel to the central axis A, or be inclined relative to the latter. In particular, the angle between the axis along which the chevron 4 extends downstream and the central axis A can be comprised between −60° and 60°, preferably between −15° and 15°.

Thus, in the example shown in FIG. 4, the chevrons 4 are protrusions projecting downstream from the reference plane P. The geometry of the chevrons 4 is not limited, the latter can have a triangular (as in FIG. 4), corrugated or serrated shape, for example. The chevrons 4 can also vary in their amplitude, i.e. their axial length from the reference plane P, their width, i.e. their azimuthal length along the trailing edge 122 at the plane P, or their spacing, i.e. the azimuthal distance between the tips (or the hollows) of two adjacent chevrons 4. In this regard, an amplitude h of the chevrons 4 is defined, and in particular an amplitude h(θ), which is the amplitude of a chevron 4 as a function of the azimuthal position θ along the trailing edge 122. Also defined is a spacing λ between two chevrons, and in particular a spacing λ(θ), which is the spacing between the tips of two adjacent chevrons 4 as a function of the azimuthal position θ along the trailing edge 122. It is thus understood that the geometry, the amplitude, the width or the spacing of the chevrons can vary as a function of the azimuthal position θ along the trailing edge.

It will be noted that the function h(θ) can be a combination of linear, parabolic, sinusoidal, hyperbolic, exponential or logarithmic functions. For example, the amplitude of the chevrons can be defined by the following function: h(θ)/h_max=180−∥θ∥/180*sin(θM+δ)+1/2.

Where h_maxis a maximum amplitude, δ is a dephasing angle, M the total number of chevrons, and θ is the azimuthal angle in degrees, which can vary between −180° and 180°. In this configuration, θ=0° corresponds to the azimuthal position at 12 H (12 o'clock) and θ=+/−180° corresponds to the azimuthal position at 6 H (6 o'clock).

Moreover, the trailing edge 122 comprises at least one first trailing edge pattern M1, and at least one second trailing edge pattern M2. In the example shown in FIG. 4, two first patterns M1 and three second patterns M2 are visible. In the present disclosure, the first pattern M1 is characterized by a portion of the trailing edge 122 comprising at least one chevron 4, or a portion of the trailing edge 122 not having a chevron. In the example illustrated in FIG. 4, the first pattern M1 corresponds to a portion of the trailing edge 122 not comprising a chevron 4. In other words, the trailing edge 122 remains comprised in the reference plane P in this portion. Moreover, the second pattern M2 is characterized by a portion of the trailing edge 122 comprising at least one chevron 4, and is distinct from the first pattern M1.

The first and second patterns M1 and M2 alternate one after the other around the axis A in the azimuthal direction. Thus, a first pattern M1 is necessarily arranged between two second patterns M2, and conversely. It will also be noted that not only are the patterns M1 and M2 different from one another, but each of the first patterns M1 are not necessarily to each other, and each of the second patterns M2 are also not necessarily identical to each other. Thus, the two first patterns M1 visible in FIG. 4 are identical and are portions of the trailing edge 122 with no chevrons 4. On the other hand, the second patterns M2 are different from one another. In particular, among the second patterns M2 visible in FIG. 4, two comprise two chevrons 4, with different amplitudes h, and another comprises a single chevron 4, with a different amplitude h and width from the two other patterns M2.

It is thus possible to determine suitable arrangements and structures of the patterns M1, M2 allowing improving the reduction of the jet noise, depending on the local specificities of the turbine engine and of the flow. FIG. 5 illustrates in more detail the manner in which the first patterns M1 and the second patterns M2 are respective arranged relative to the stator blades.

The non-limiting example shown in FIG. 5 is an unducted turbine engine 1′ of the USF type, the characteristics of which, identical to the turbine engine shown in FIG. 3B, will not be repeated. It will be noted that the distance S between the trailing edge of the blades 32 and the point of the trailing edge 122′ of the exhaust nozzle 12′ closest to the blade 32, and the chord C of the blades 32 measured at their connexion, satisfy S/C<5. In this example, the trailing edge 122′ comprises a plurality of chevrons 4 protruding from the reference plane P.

According to the invention, the number and the structure of the patterns are determined as a function of the number N and of the azimuthal position of the stator blades, in particular the blades satisfying the relation Si/Ci<5. In the examples shown in FIG. 5, N=10, where N is the number of blades 32. The number of first patterns M1 different from one another is comprised between 1 and N. Likewise, the number of different patterns M2 different from one another is comprised between 1 and N. In other words, the total number of different patterns can be comprised between 2 and 2*N. Thus, in the example illustrated in FIG. 5, there are only two different patterns, the first patterns M1 all being identical to one another, and the all the second patterns M2 also being identical to one another. Nevertheless, as previously indicated, this configuration is not limiting, the patterns M1 and M2 respectively being able to be different from one another.

Moreover, the first patterns M1 are arranged in such a manner that each of them extends in the azimuthal direction over an angular range Δθ, preferably centered on the pitch change axis X2 of a blade 32, including this blade 32. In other words, in a rear view of the turbine engine parallel to the central axis A, corresponding to the right view of FIG. 5, each blade 32 is arranged inside the interval delimited by the angular range Δθ, defining the first pattern M1. It will be noted, moreover, that Δθ is such that Δθ_min≤Δθ≤Δθ_max, where Δθ_min=360/(36*N) and Δθ_max=360/(N+1), in order to provide optimal operation regardless of the variation of the pitch angle of the blades 32 around the pitch change axis X2 of each blade.

Likewise, the second patterns M2 are arranged in such a manner that each of them extends in the azimuthal direction over an angular range Δθ′ not including a blade 32. In other words, in a rear view parallel to the central axis A, no blade 32 is arranged inside the interval delimited by the angular range Δθ′, defining the second pattern M2. It will also be noted that N*Δθ+N*Δθ ′=360°.

In the example illustrated in FIG. 5, the first patterns M1 are all identical to one another as indicated above, and characterized by a portion of the trailing edge 122′ not comprising a chevron 4. In other words, over the angular ranges Δθ including the blades 32, i.e. at the azimuthal positions corresponding to the blades 32, the trailing edge 122′ does not comprise a chevron 4. In addition, the second patterns M2, also all identical to one another, are characterized by a portion of the trailing edge comprising three chevrons 4. In other word, over the angular ranges 40′ not including the blades 32, i.e. at the azimuthal positions corresponding to the space between two blades 32, the trailing edge 122′ comprises three chevrons 4.

It will also be noted that for each second pattern M2, the three chevrons 4 are identical to one another, and have in particular the same amplitude, the same geometric shape and the same width. This configuration, however, is not limiting, as indicated in the rest of the description, describing different exemplary embodiments conforming to the invention, with reference to FIGS. 6A to 6H, 7A to 7F and 8.

FIG. 6A shows a configuration in which the first patterns M1 are identical to one another and correspond to portions of the trailing edge with no chevron. On the other hand, the second patterns M2 are not all identical to one another, the latter being able to comprise three or four chevrons 4. It will be noted that, in this example, the chevrons 4 correspond to notches along the trailing edge.

FIG. 6B shows a configuration in which the first patterns M1 are identical to one another and correspond to portions of the trailing edge with no chevron, the angular range Δθ of which over which the first patterns M1 extend in the azimuthal direction is greater than in the examples illustrated in FIGS. 5 and 6A. Moreover, the second patterns M2 are also all identical to one another, and each comprises one chevron 4. It will be noted that, alternatively, the first patterns M1 could each comprise one chevron 4, the second patterns M2 then having no chevron.

FIG. 6C shows an alternative example similar to the example of FIG. 5, but of which one angular range Δθ at 12 H (12 o'clock) is locally greater, and corresponds to a third pattern. The latter is arranged at an azimuthal position corresponding to the pylon or mast attaching the turbine engine to the aircraft, in order to take into account the presence of this pylon which could also interact with the jet and increase the jet noise. A fourth pattern comprises a single chevron is also arranged on either side of the third pattern.

FIG. 6D shows a configuration applicable in particular to an unducted turbine engine, particularly the turbine engine illustrated in