Chevron-equipped outlet nozzle for aircraft propulsion

Abstract

Chevron-equipped outlet nozzle for aeronautical propulsion system. Outlet nozzle (12') for aeronautical propulsion system disposed downstream of at least one stator blade (32) of the propulsion system, a trailing edge (122') of the outlet nozzle comprising a plurality of chevrons (4) distributed circumferentially around a central axis, said trailing edge (122') comprising a first trailing edge pattern (M1) extending over an angular range Δθ including at least one stator blade (32), the first pattern (M1) being a portion of the trailing edge comprising at least one chevron (4) or being a portion of the trailing edge not having a chevron, and a second trailing edge pattern (M2) extending over an angular range Δθ' not including at least one stator blade (32), the second pattern (M2) being a portion of the trailing edge comprising at least one chevron (4) or being a portion of the trailing edge not having a chevron (4), and being distinct from the first pattern (M1).Figure for the abridged version: Fig. 5.

Description

Title of the invention: Chevron-equipped outlet nozzle for an aeronautical propulsion system technical field

[0001] The present invention relates to the general field of aeronautical propulsion, and applies more particularly to aircraft turbojets and turboprops, especially but not exclusively of the large-diameter type. The invention relates in particular to a gas ejection nozzle equipping an aeronautical turbomachine, and specifically concerns the reduction of jet noise at the outlet of such an ejection nozzle. Prior art

[0002] For new generations of commercial aircraft, it is envisaged that aeronautical propulsion systems with a high bypass ratio (BPR), for example, bypass ratios greater than 10, and a large diameter, i.e., diameters greater than 1.5 m, will be used in order to increase the propulsive efficiency of turbojets and reduce their fuel consumption, as well as pollutant emissions. Aeronautical propulsion systems may be internal combustion engines, in particular turboshaft engines, turbojets, high bypass ratio turbofans, geared or gearbox turbofans, counter-rotating turbine turbojets, electric motors, hydrogen engines, or hybrid internal combustion and / or electric and / or hydrogen engines.Aircraft propulsion systems can include several engines, and the energy sources for these engines can be kerosene-based fuels, aviation gasoline, diesel, aviation biofuels, electricity, or hydrogen. It should be noted that the term "turbojet" refers to a gas turbine device that provides thrust, through reaction to the high-speed ejection of hot gas, which contributes to propulsion.

[0003] Furthermore, different types of aeronautical propulsion systems, including ducted and unducted turbojets, can be used: - “Ultra High Bypass Ration” (UHBR): ducted 100 turbojet as illustrated in [Fig. 1], with a fixed-pitch fan wheel, with or without a fan speed reduction gearbox, - "Variable Pitch Fan" (VPF): a ducted turbojet engine with a variable pitch fan, - “Counter Rotating Open Rotor” (CROR): an unfaired turbojet engine with two (or more) counter-rotating propellers with variable pitch, - "Unducted Stator Fan" (USF): 100' unducted turbojet engine as illustrated on the [Fig.2], with a propeller wheel 31 with variable pitch and a rectifier wheel 32 (stator) with fixed or variable pitch.

[0004] Unfaired turboprops can also be used. It should be noted that the term "turboprop" refers to a gas turbine aircraft whose thrust is primarily obtained by the traction of the variable-pitch propeller.

[0005] However, a major drawback of these integrated architectures on commercial aircraft is their acoustic impact, i.e., noise levels. Aircraft noise levels are subject to increasingly stringent international regulations during takeoff and landing phases, in order to limit the noise footprint in the vicinity of airports. Although increasing the bypass ratio and reducing the fan or propeller rotational speed on unfaired architectures has made it possible to reduce the secondary flow ejection velocity and improve flow mixing downstream of the turbomachine, and thus improve jet noise reduction, the latter remains a significant source of noise that must be taken into account in the design process of an aircraft turbomachine.

[0006] In Figures 1 and 2, the generated jet noise is represented by dashed arcs. With reference to [Fig. 1] representing a shrouded turbomachine 100, the jet noise is primarily due to the high-speed airflow exit from the primary flow Fl (and / or the secondary flow F2), which produces broadband noise that dominates at low frequencies. In addition, the jet interacts with the boundary layer CL that develops on the internal / external surface of the nacelle 20 (or the casing 10) of the turbomachine, resulting in a shear layer CS.

[0007] Furthermore, the jet can also interact with the wakes at the top or bottom of stator blades or structural arms, for example, outlet guide vanes 30 (OGVs), or exhaust casing blades 40 (TRFs) downstream of the low-pressure turbine, near the outlet plane of one or more exhaust nozzles 12, 22 of the turbomachine gases. Indeed, the flow at the bottom or top of a blade can exhibit flow separation (known as "detached" flows or recirculation zones) at certain engine speeds or operating points of the turbomachine. These phenomena can also contribute to jet noise.In addition, the aforementioned large-diameter turbomachine architectures feature a short nacelle 20 in the ducted engines, in order to reduce drag, which reduces the distance between the stator blades 30, 40 and the nozzle exit plane 12, 22 and promotes phenomena inducing jet noise.

[0008] A known solution per se consists of arranging chevrons along the trailing edge of the outlet nozzles, thereby reducing jet noise by promoting mixing of the shear layer at the interface of two flows with different velocities. In addition, they serve to reduce trailing edge noise, which is related to the passage of a turbulent boundary layer through the trailing edge of the casing or nacelle.

[0009] However, despite their advantages, these solutions are not suitable for all types of turbomachinery, and improvements are still needed. Therefore, there is a need for a solution that further improves jet noise reduction and at least partially mitigates the aforementioned drawbacks. Description of the invention

[0010] The present description relates to an outlet nozzle for an aeronautical propulsion system, the outlet nozzle being intended to extend around a central axis and to be disposed downstream of at least one stator blade of the propulsion system, a trailing edge of the outlet nozzle comprising a plurality of chevrons distributed circumferentially around the central axis, said trailing edge comprising: - at least one first trailing edge pattern intended to extend, in an azimuthal direction, over an angular range A0 including at least one stator blade, the first pattern being a portion of the trailing edge comprising at least one chevron or being a portion of the trailing edge not having a chevron, and - at least one second trailing edge pattern intended to extend, in the azimuthal direction, over an angular range A0' not including at least one stator blade, the second pattern being a portion of the trailing edge comprising at least one chevron or being a portion of the trailing edge not having a chevron and being distinct from the first pattern.

[0011] In the present description, the terms "upstream," "downstream," and their derivatives are defined according to a normal airflow direction through the turbomachine, along the central axis, i.e., along the axis of rotation of the turbomachine. Similarly, the terms "radial," "circumferential," "azimuthal direction," and their derivatives are considered with respect to the central axis of the nozzle, in other words, with respect to the axis of rotation of the turbomachine with which the central axis of the nozzle can be coincident.

[0012] The term "chevron" is understood to mean an irregularity along the trailing edge of the nozzle, characterized by the presence of a protuberance (or apex) and / or a notch (or hollow), relative to a reference plane defined by the trailing edge in the case where the latter does not include any chevron.

[0013] Furthermore, a trailing edge pattern is a portion of the trailing edge perimeter extending over an azimuthal length, in other words over a predetermined angular range, and having a predetermined geometry. A first pattern is defined as extending over an angular range A0 including a blade of stator arranged upstream of the trailing edge. In other words, in a front view of the outlet nozzle, perpendicular to the reference plane defined by the trailing edge and parallel to the central axis, the stator blade, then arranged behind the trailing edge according to this view, is within the angular range A0 delimiting the first pattern.

[0014] Similarly, according to this same view, the angular range A0' delimiting the second pattern does not include any stator blade. Thus, when several stator blades are arranged upstream of the outlet nozzle, each first pattern extends over a range A0 including one of the stator blades, and each second pattern extends over a range A0' not including a stator blade.

[0015] Furthermore, the first or second trailing edge pattern is defined as a portion of the trailing edge comprising at least one chevron, or no chevrons. It is understood that in the case where the first or second trailing edge pattern is a portion of the trailing edge without a chevron, this portion is straight, that is, contained within the reference plane defined above. In a preferred embodiment of the invention, the first trailing edge pattern is a portion of the trailing edge without a chevron, and the second trailing edge pattern is a portion of the trailing edge having at least one chevron.

[0016] Thus, according to the present description, the various trailing edge patterns, including or not including chevrons, are positioned taking into account the azimuthal position of the stator blades located upstream of the outlet nozzle, which can generate jet noise as described above. In particular, the first and second patterns are different so as to account for the presence or absence of a blade upstream of the trailing edge. It is therefore possible to adapt the pattern structure, in particular the number and / or shape of the chevrons, according to the position, orientation, or shape of the blades, in order to improve noise reduction. In particular, it is possible to adapt the pattern structure according to the local characteristics of the turbomachine and the flow specifics at the outlet nozzle.

[0017] In some embodiments, a trailing edge curve is a curve describing the shape of the trailing edge of the nozzle in a view perpendicular to the central axis, a portion of the trailing edge comprising at least one chevron being an interval of the trailing edge curve in which said curve comprises at least one maximum between the two ends of the interval, and a portion of the trailing edge not having a chevron being an interval of the trailing edge curve in which said curve is constant.

[0018] In some embodiments, the first trailing edge pattern is a portion of the trailing edge comprising at least one chevron, the second trailing edge pattern being different from the first trailing edge pattern by at least one, preferably to minus two among the number, amplitude, width, spacing or geometry of the chevrons.

[0019] The presence of structural arms, for example, in the internal airflow upstream of the outlet nozzle can impact the axisymmetry of the jet. Thus, having the second patterns differ by at least one, preferably at least two parameters, for example by increasing the number of chevrons and / or increasing the amplitude and / or reducing the spacing or width of the chevrons locally, near the blades or elements that can interact with the jet (for example, a pylon, a wing and / or a high-lift device on the wing) makes it possible to improve the mixing of the jet and therefore to break up large vortex structures before interacting with neighboring elements.

[0020] In certain embodiments, the first trailing edge pattern and / or the second trailing edge pattern are not homothetic geometric patterns. In this case, it is understood that the second trailing edge pattern is not obtained by a transformation of the first trailing edge pattern resulting from an enlargement or reduction thereof, but preferably from a modification of the number of chevrons or their geometry, for example.

[0021] In some embodiments, the second trailing edge pattern is a portion of the trailing edge comprising at least two chevrons. In a preferred embodiment of the invention, the first trailing edge pattern is a portion of the trailing edge without a chevron, the second trailing edge pattern being a portion of the trailing edge comprising at least two chevrons.

[0022] In certain embodiments, the at least one first pattern and / or the at least one second trailing edge pattern comprises at least two chevrons of different amplitudes and / or widths and / or geometries.

[0023] In other words, a single pattern can comprise chevrons that are distinct from one another and differ in particular in their amplitude and / or width, and / or geometry. It is thus possible to adapt the structure of a pattern according to the local flow structure.

[0024] In certain embodiments, when at least one first pattern and / or at least one second trailing edge pattern comprise two chevrons so as to form at least one gap between said at least two chevrons, the at least one gap is filled at least in part by a porous material.

[0025] In other words, a porous material is arranged in said space in at least one interval, so as to occupy at least part of the space left free between the two rafters. Porous materials, for example, metallic foams, have the advantage of possessing good sound absorption properties. In particular, these porous materials make it possible to effectively reduce broadband and low-frequency noise. These characteristics are particularly advantageous with regard to jet noise and allow for its further reduction. In addition, the porous materials allow for quiet jet operation.

[0026] In certain embodiments, where at least one first pattern and / or at least one second trailing edge pattern comprises two chevrons arranged to form at least one gap between said at least two chevrons, the at least one gap is filled at least partially by a plurality of metal strips. In other words, metal strips are arranged in said at least one gap so as to occupy at least part of the space left free between the two chevrons.

[0027] In some embodiments, the metal strips have an amplitude h and a width E such that h / E>10.

[0028] As an alternative to porous materials, it is possible to promote a gradual mixing of the jet and thus to attenuate the noise of the jet by visco-thermal phenomena thanks to metallic lamellae formed by a plurality of grooves, or slots, made along the trailing edge of the nozzle, thus forming a metallic brush structure allowing to reduce the noise of the jet.

[0029] In some embodiments, the outlet nozzle comprises an upstream portion, and an annular hood configured to be detachably attached to the upstream portion, a downstream end of the annular hood comprising the plurality of chevrons.

[0030] In other words, the annular cowling comprising the trailing edge of the outlet nozzle and the plurality of chevrons is detachable from the rest of the nozzle, particularly the upstream portion. This makes it possible to easily remove and replace the chevrons during maintenance operations or in case of damage to the chevrons.

[0031] The present description also relates to an aeronautical propulsion system configured to accommodate at least one internal airflow, comprising at least one outlet nozzle according to any of the preceding embodiments and through which at least one internal airflow is ejected, and at least one stator blade disposed upstream of the outlet nozzle.

[0032] In some embodiments, S / C < 5, where S is the distance between the trailing edge of at least one stator blade at the point where the stator blade is fixed to a housing, hub, or nacelle of the propulsion unit and the point on the trailing edge of the outlet nozzle closest to the stator blade in the direction of the central axis, and C is the chord of the stator blade measured at the point where it is fixed.

[0033] These ratios make it possible to make the propulsion system more compact, in particular by reducing the length of the casing or the nacelle, which also reduces drag.

[0034] In certain embodiments, the aeronautical propulsion system comprises N stator blades, where N>2, distributed circumferentially around the central axis, N first trailing edge patterns each extending over an angular range A0 including one of the N blades, and N second trailing edge patterns distinct from the first patterns and each extending over an angular range A0' not including any of the N blades, the number of first patterns distinct from each other being between 1 and N, and the number of second patterns distinct from each other being between 1 and N. It should be noted that N can be between 3 and 80.

[0035] In other words, the first motifs are arranged at the azimuthal positions corresponding to the stator blades, and the second motifs are arranged in an interval between two first motifs, corresponding to azimuthal positions not including any stator blade.

[0036] In certain embodiments, each angular range A0 including one of the N blades is centered on a principal axis of the blade, and is such that A0min < A0 < A0max, where A0min = 360 / (36*N) and A0max=360 / (N+l), A0min, A0 and A0max are expressed in degrees.

[0037] In some embodiments, the main axis of the blade is the pitch change axis when the blades are variable pitch stator blades.

[0038] The stator blade pitch angle can vary depending on the propulsion system's operating conditions, particularly during cruise, landing, or takeoff. Consequently, a change in the blade pitch angle can lead to a change in the flow direction downstream of the stator blades (if, for example, the flow is not completely straightened by the stators), or to a change in the width of the stator wakes or their azimuthal positions at the nozzle exit plane. Therefore, these angular range values ​​A0 ensure optimal operation regardless of the variation in the stator blade pitch angle.

[0039] In some embodiments, the main axis of the blade is the axis perpendicular to the central axis and passing through the trailing edge of the blade at the point where the stator blade is embedded in a housing, a hub, or a nacelle of the propulsion unit, when the blades are fixed-pitch stator blades.

[0040] In some embodiments, the aeronautical propulsion system is a turbofan engine.

[0041] In certain embodiments, the aircraft propulsion system is a ducted turbofan engine comprising a first outlet nozzle through which a first internal airflow is ejected and a second outlet nozzle through which a second internal airflow is ejected, a trailing edge of each of the first and second outlet nozzles comprising a plurality of chevrons, at least one first stator blade being disposed in the first internal airflow upstream of the first outlet nozzle, and at least a second stator blade being disposed in the second internal airflow upstream of the first outlet nozzle and the second outlet nozzle, the trailing edge of each of the first and second outlet nozzles comprising at least a first pattern and at least a second trailing edge pattern.

[0042] In other words, each of the first and second outlet nozzles comprises first motifs arranged at azimuthal positions corresponding to the positions of the first and second stator blades, respectively. It is thus possible to adapt the trailing-edge pattern structures on each outlet nozzle, according to the local specificities of each internal flow and each nozzle, thereby reducing the jet noise of the shrouded turbofan engine.

[0043] In certain embodiments, the aircraft propulsion system is an unfaired turbofan engine comprising an outlet nozzle whose internal surface delimits the internal airflow and whose external surface delimits an external airflow, a trailing edge of the outlet nozzle comprising a plurality of chevrons, at least one first stator blade being disposed in the internal airflow upstream of the outlet nozzle. It is understood that in this case, the first stator blade is a fixed TRF blade of the exhaust casing.

[0044] In some embodiments, the aeronautical propulsion system includes at least one second stator blade disposed in the external airflow upstream of the outlet nozzle, the trailing edge of the outlet nozzle comprising at least one first pattern and at least one second trailing edge pattern, the at least one first pattern being disposed such that the angular range A0 over which it extends includes the blade closest axially to the trailing edge, among the at least one first stator blade and the at least one second stator blade.

[0045] In certain embodiments, at least one first pattern is arranged such that the angular range A0 over which it extends includes the blade with the lowest S / C ratio among at least one first stator blade and at least one second stator blade. In this case, the stator blades fixed to the outer and inner faces of a housing, hub, or nacelle of the unfaired propulsion unit are likely to generate jet noise at the outlet nozzle upstream of which they are located. Arranging the various trailing-edge patterns, particularly the first patterns, according to the azimuthal positions of the blades closest to the trailing edge of the outlet nozzle, or those with the lowest S / C ratio, optimizes jet noise reduction.

[0046] In certain embodiments, when the outlet nozzle comprises more than two distinct patterns, the variation of the patterns according to the azimuthal direction is not monotonic. For example, when the thruster includes N stator blades, N distinct first patterns and N distinct second patterns, in other words a total of 2*N distinct patterns, the variation of the patterns along the circumference of the trailing edge is not only a decrease in the amplitude of the chevrons, for example, but may alternate between increases and decreases in amplitude, and also include variations in the width and / or spacing and / or geometry of the chevrons.

[0047] In some embodiments, the outlet nozzle includes a third trailing edge pattern extending over an angular range including a propeller attachment pylon to an aircraft wing, the third trailing edge pattern being a portion of the trailing edge without a chevron.

[0048] When the propulsion system is installed in an aircraft, the presence of a pylon (or mast) and / or the wing can also affect the jet's expansion. Therefore, incorporating a third trailing edge pattern, preferably without a chevron, improves jet noise reduction. Brief description of the drawings

[0049] The invention and its advantages will be better understood upon reading the following detailed description of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figure pages, on which:

[0050] [Fig-1] Fig. 1 schematically represents a partial cross-sectional view of a tur- streamlined boat according to prior art

[0051] [Fig.2] Fig.2 schematically represents a partial cross-sectional view of a tur- unfaired boat according to prior art

[0052] [Fig. 3A-3B] Figure 3A schematically represents a partial cross-sectional view of a ducted turbomachine according to a first embodiment of the invention, and Figure 3B schematically represents a partial cross-sectional view of an unducted turbomachine according to the first embodiment,

[0053] [Fig. 4] [Fig. 4] schematically represents a side view of an outlet nozzle of the turbomachine in Figure 3A,

[0054] [Fig.5] Fig.5 schematically represents a side view and a rear view, relative to the central axis of the turbomachine, of an example of an unfaired turbomachine conforming to the first embodiment,

[0055] [Fig. 6A-6H] Figures 6A to 6H schematically represent rear views of the unfaired turbomachine of [Fig. 5], according to various examples conforming to the first embodiment,

[0056] [Fig. 7A-7F] Figures 7A to 7F schematically represent side views of the unfaired turbomachine outlet nozzle of [Fig. 5], according to various examples conforming to the first embodiment,

[0057] [Fig. 8] Fig. 8 schematically represents side views of an outlet nozzle illustrating alternative examples conforming to the first embodiment,

[0058] [Fig. 9] Fig. 9 schematically represents a rear view of the turbomachine of Figure 3A, according to an example conforming to the first embodiment,

[0059] [Fig. 10] Figure 10 schematically represents lateral views of an outlet nozzle of a turbomachine according to a second embodiment,

[0060] [Fig. 11] Figure 11 schematically represents lateral views of an outlet nozzle of a turbomachine according to a third embodiment,

[0061] [Fig. 12] Figure 12 schematically represents side views of an outlet nozzle of a turbomachine according to a fourth embodiment. Description of embodiments

[0062] A first embodiment conforming to the present description will be described with reference to Figures 3A to 9. In the non-limiting examples described below, the aeronautical propulsion systems are turbomachines. In the remainder of this description, the terms "upstream," "downstream," and their derivatives are defined with respect to the direction of gas flow in the turbomachine along the central axis A of the turbomachine. Furthermore, the terms "radial," "circumferential," "azimuthal direction," and their derivatives are also defined with respect to the central axis A.

[0063] Figures 3A and 3B respectively represent a shrouded turbomachine (for example of the UHBR or VPF type) and an unshrouded turbomachine (for example of the CROR or USF type), on which a device conforming to this description can be applied.

[0064] In particular, Figure 3A represents a shrouded, twin-flow turbomachine 1 with a central axis of rotation A. Similar to the prior art turbomachine described with reference to [Fig. 1], it includes, in particular, a casing 10 whose internal surface defines a primary internal flow, and a nacelle 20 whose internal surface defines a secondary internal flow. A first outlet nozzle 12 is disposed at a downstream end of the casing 10, the primary internal flow being ejected by said first outlet nozzle 12. A second outlet nozzle 22 is disposed at a downstream end of the nacelle 20, the secondary internal flow being ejected by said second outlet nozzle 22.

[0065] At least one fixed blade of the exhaust casing 40 (referred to as the TRF blade in the following description) is disposed in the primary internal flow, upstream of the first outlet nozzle 12, more precisely upstream of a trailing edge 122 of the first outlet nozzle 12. The TRF is the last blade wheel in the primary internal flow of the turbomachine 1, located downstream of the low-pressure turbine and enabling to evacuate high-temperature air from the combustion chamber and the high / low pressure turbine stages. The number of TRF 40 blades is typically around 10.

[0066] At least one outlet guide vane 30 (hereafter referred to as an OGV vane) is disposed in the secondary internal flow, upstream of the second outlet nozzle 22, more precisely upstream of a trailing edge 222 of the second outlet nozzle 22. The OGV is a fixed wheel disposed downstream of the fan 2, in the secondary internal flow of the shrouded turbomachine 1, and serves to correct the flow's gyration. The number of vanes 30 comprising the OGV wheel can be between 30 and 60. This example is not limiting; the invention can be applied to outlet nozzles disposed downstream of structural arms, themselves disposed downstream of the OGV vanes, or integrated into the OGV.

[0067] Furthermore, S1 represents the distance between the trailing edge of a blade 40 at its mounting on the inner face of the housing 10, and the point on the trailing edge 122 of the first outlet 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 mounting. In other words, C1 is the axial distance between the leading edge and the trailing edge of the blade 40 at said mounting. S2 represents the distance between the trailing edge of a blade 30 at its mounting on the outer face of the housing 10, and the point on the trailing edge 122 of the first outlet nozzle 12 closest to the blade 30. C2 is the chord of the blade 30 measured at said mounting.Finally, S2' represents the distance between the trailing edge of the blade 30 at the point where it is fitted to the inner face of the nacelle 20, and the point on the trailing edge 222 of the second outlet nozzle 22 closest to the blade 30. C2' is the chord of the blade 30 measured at said fitting.

[0068] Figure 3B shows an unshrouded, twin-flow turbomachine 1' with a central axis of rotation A. It comprises a casing 10' whose inner surface defines a primary internal flow, and whose outer surface defines a secondary external flow. An outlet nozzle 12' is disposed at a downstream end of the casing 10', the primary internal flow being ejected by said outlet nozzle 12'.

[0069] The turbomachine 1' comprises an unshod propeller having a plurality of rotor blades 31, preferably with variable pitch about a pitch-change axis XI. In the present example, the unshod turbomachine 1' is of the USF type comprising stator blades 32 arranged downstream of the rotor blades 31. The stator blades 32 (or stator, or SRV for "swirl recovery vane") are preferably fixed with variable pitch about a pitch-change axis X2. The invention is nevertheless applicable to stator blades 32 with fixed pitch. The number of blades 32 is preferably between 5 and 20.

[0070] In addition, in the same way as the shrouded turbomachine, at least one fixed blade 40 of TRF is disposed in the primary internal flow, upstream of the outlet nozzle 12', more precisely upstream of a trailing edge 122' of the outlet nozzle 12'.

[0071] Furthermore, S1 represents the distance between the trailing edge of a blade 40 at its mounting on the inner face of the housing 10', and the point on the trailing edge 122' of the outlet 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 mounting. Similarly, S2 represents the distance between the trailing edge of a blade 32 at its mounting on the outer face of the housing 10', and the point on the trailing edge 122' of the outlet nozzle 12' closest to the blade 32. C2 is the chord of the blade 32 measured at said mounting.

[0072] Each of the turbomachines conforming to this description and shown in Figures 3A and 3B are large-diameter turbomachines, having a principal diameter D, which may be the diameter of the fan in the case of the shrouded turbomachine, or the diameter of the upstream rotor in the case of the unshrouded turbomachine, such that D > 1.5 m. Furthermore, 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 between 0 and 15. Preferably, Si / Ci < 5. The value of this ratio makes it possible to reduce the distance between the stator blades 30, 32, 40 and the nozzle exit plane. However, this also contributes to an increase in jet noise.

[0073] Thus, to reduce jet noise, the outlet nozzles according to this description comprise, along their trailing edge, a plurality of chevrons 4 distributed circumferentially around the central axis A, representing both the central axis of the nozzle 12, 12', 22 and the axis of rotation of the turbomachine 1, 1'. Figure 4 shows a trailing edge 122 of the outlet nozzle 12 of Figure 3A. This example is not limiting and could be applied in the same way to the outlet nozzle 22 of the nacelle 20, or to the outlet nozzle 12' of the unfaired turbomachine 1'.

[0074] A chevron 4 corresponds to an irregularity along the trailing edge 122, characterized by the presence of a protrusion and / or a notch, relative to a reference plane P defined by the trailing edge 122 in the case where the latter does not include any chevrons. It should be noted that the reference plane P forms an angle α with respect to the central axis A, the angle α being either equal to 90° or different from 90°, such that the nozzle outlet plane can be inclined with respect to the central axis A. Preferably, the angle α is between 40° and 140°. Furthermore, the chevrons 4 can extend downstream parallel to the central axis A, or be inclined with respect to it. In particular, the angle between the axis along which a chevron 4 extends downstream and the central axis A can be between -60° and 60°, preferably between -15° and 15°.

[0075] Thus, in the example shown in [Fig.4], the chevrons 4 are protrusions projecting downstream from the reference plane P. The geometry of the rafters 4 is not limited; they can be triangular (as in [Fig. 4]), corrugated, or crenellated, for example. The rafters 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 level of plane P, or their spacing, i.e., the azimuthal distance between the peaks (or troughs) of two adjacent rafters 4. In this regard, we define an amplitude h of the rafters 4, and in particular an amplitude h(0), which is the amplitude of a rafter 4 as a function of the azimuthal position 0 along the trailing edge 122. We also define a spacing X between two rafters, and in particular a spacing X(0), which is the spacing between the vertices of two adjacent rafters 4 as a function of the azimuthal position 0 along the trailing edge 122.It is thus understood that the geometry, amplitude, width or spacing of the chevrons can vary depending on the azimuthal position 0 along the trailing edge.

[0076] It should be noted that the function h(0) 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:

[0077] h(V) _ 180-Hf?|| *sin(&W+Ô)+l hm^ “180 2

[0078] Where hmax is a maximum amplitude, ô is a phase angle, M the total number of chevrons, and 0 is the azimuthal angle in degrees which can vary between -180° and 180°. In this configuration, 0 = 0° corresponds to the azimuthal position at 12H and 0 = + / -180° corresponds to the azimuthal position at 6H.

[0079] Furthermore, 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 description, 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 lacking a chevron. In the example illustrated in [Fig. 4], the first pattern M1 corresponds to a portion of the trailing edge 122 lacking a chevron 4. In other words, the trailing edge 122 remains contained within the reference plane P over this portion. Furthermore, 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 ML

[0080] The first and second patterns M1 and M2 alternate one after the other around the axis A in the azimuthal direction.Thus, a first motif M1 is necessarily situated between two second motifs M2, and vice versa. It should also be noted that not only are motifs M1 and M2 different from each other, but each of the first motifs M1 is not necessarily identical to the others, and each of the... The second M2 patterns are not necessarily identical to each other. Thus, the first two M1 patterns visible in [Fig. 4] are identical and are portions of the trailing edge 122 without chevrons 4. In contrast, the second M2 patterns are different from each other. In particular, among the second M2 patterns visible in [Fig. 4], two include two chevrons 4, of different amplitudes h, and another includes a single chevron 4, of a different amplitude h and width than the other two M2 patterns.

[0081] It is thus possible to determine the appropriate arrangements and structures of the M1 and M2 motifs to improve jet noise reduction, depending on the local characteristics of the turbomachine and the flow. Figure 5 illustrates in more detail how the first M1 motifs and the second M2 motifs are respectively arranged with respect to the stator blades.

[0082] The non-limiting example shown in [Fig. 5] is an unfaired turbomachine 1' of type USF, the characteristics of which, identical to the turbomachine shown in Figure 3B, will not be repeated. It should be noted that the distance S between the trailing edge of the blades 32 and the point on the trailing edge 122' of the outlet nozzle 12' closest to the blade 32, and the chord C of the blades 32 measured at their fixed end, satisfy S / C < 5. In this example, the trailing edge 122' comprises a plurality of chevrons 4 projecting from the reference plane P.

[0083] According to the invention, the number and structure of the motifs are determined as a function of the number N and the azimuthal position of the stator blades, in particular the blades having a Si / Ci ratio < 5. In the example shown in [Fig. 5], N = 10, where N is the number of blades 32. The number of first motifs M1, which are different from each other, is between 1 and N. Similarly, the number of second motifs M2, which are different from each other, is between 1 and N. In other words, the total number of different motifs can be between 2 and 2*N. Thus, in the example shown in [Fig. 5], there are only two different motifs, the first motifs M1 being all identical to each other, and the second motifs M2 also being all identical to each other. However, as previously stated, this configuration is not exhaustive, as the M1 and M2 patterns may be different from each other.

[0084] Furthermore, the first motifs M1 are arranged such that each of them extends in the azimuthal direction over an angular range A0, preferably centered on the axis X2 of pitch change of a blade 32, including this blade 32. In other words, in a rear view of the turbomachine parallel to the central axis A, corresponding to the right-hand view in [Fig. 5], each blade 32 is arranged within the interval delimited by the angular range A0, defining the first motif ML. It should also be noted that A0 is such that A0min < A0 < A0max, where A0min = 360 / (36*N) and A0max = 360 / (N+1), in order to ensure optimal operation regardless of the variation in the angle of the blades 32 around the axis X2 of change of the angle of each blade.

[0085] Similarly, the second motifs M2 are arranged such that each of them extends in the azimuthal direction over an angular range A0' not including a blade 32. In other words, in the rear view parallel to the central axis A, no blade 32 is arranged within the interval delimited by the angular range A0', defining the second motif M2. It should also be noted that N* A0 + N* A0' = 360°.

[0086] In the example illustrated in [Fig. 5], the first motifs M1 are all identical to each other as indicated above, and are characterized by a portion of the trailing edge 122' not including a chevron 4. In other words, on the angular ranges A0 including the blades 32, i.e., on the azimuthal positions corresponding to the blades 32, the trailing edge 122' does not include a chevron 4. Furthermore, the second motifs M2, also all identical to each other, are characterized by a portion of the trailing edge including three chevrons 4. In other words, on the angular ranges A0' not including the blades 32, i.e., on the azimuthal positions corresponding to the space between two blades 32, the trailing edge 122' includes three chevrons 4.

[0087] It should also be noted that for each second motif M2, the three chevrons 4 are identical to each other, and in particular have the same amplitude, the same geometric shape and the same width. This configuration is not, however, limiting, as indicated in the remainder of the description, which describes various embodiments according to the invention, with reference to Figures 6A to 6H, 7A to 7F and 8.

[0088] Figure 6A shows a configuration in which the first motifs M1 are identical to each other and correspond to portions of the trailing edge without chevrons. In contrast, the second motifs M2 are not all identical to each other, as they may include three or four chevrons 4. It should be noted that in this example, the chevrons 4 correspond to notches along the trailing edge.

[0089] Figure 6B represents a configuration in which the first motifs M1 are identical to each other and correspond to portions of the trailing edge without a chevron, and in which the angular range A0 over which the first motifs M1 extend in the azimuthal direction is greater than in the examples illustrated in Figures 5 and 6A. Furthermore, the second motifs M2 are also all identical to each other, and each includes a chevron 4. It should be noted that alternatively, the first motifs M1 could each include a chevron 4, the second motifs M2 then being without a chevron.

[0090] Figure 6C represents an alternative example similar to the example in [Fig. 5], but with a locally larger angular range A0 to 12H, and corresponds to a third motif. This motif is positioned at an azimuthal location corresponding to the pylon, or mounting mast of the turbomachine to the aircraft, in order to The presence of this pylon must be taken into account, as it can also interact with the jet and increase jet noise. A fourth motif, consisting of a single chevron, is also positioned on either side of the third motif.

[0091] Figure 6D shows a configuration applicable in particular to an unshod turbomachine, notably the turbomachine illustrated in Figure 3B. In this case, the stator blades 32 and the TRF blades 40 satisfy the relationships Sl / Cl < 5 and S2 / C2 < 5, respectively, with Sl / Cl < S2 / C2. In this case, the first motifs M1 are preferably arranged taking into account the azimuthal position of the blades closest to the trailing edge 122', or those with the lowest S / C ratio. The choice of one or the other of these criteria can be made according to the noise source considered dominant, and for which the acoustic gain is greatest. Thus, in Figure 6D, the first motifs M1 are all identical and without chevrons, and extend over an angular range A0 including the TRF blades 40. The second M2 patterns extend over an angular range not including any 40 TRF blades.The second M2 patterns are all identical and include three chevrons 4 having a geometry different from that illustrated in figures 6A to 6C, notably a wavy geometry.

[0092] Figure 6E shows a configuration in which the first motifs M1 are identical to each other and correspond to portions of the trailing edge without chevrons. The second motifs M2 are also identical to each other and correspond to portions of the trailing edge comprising three chevrons 4, said chevrons not being identical to each other. More precisely, for the same second motif M2, one of the chevrons 4 has a greater amplitude and width than the other two chevrons 4 of that same second motif M2.

[0093] Figure 6F shows a configuration in which the first motifs M1 are identical to each other and correspond to portions of the trailing edge comprising two chevrons 4. The second motifs M2 are also identical to each other and correspond to portions of the trailing edge comprising one chevron 4, the amplitude of this chevron being greater than the amplitude of the chevrons 4 of the first motifs ML

[0094] Figure 6G shows a configuration in which the first motifs M1 are not all identical. For example, the first motif M1 located at 12H comprises two triangular chevrons 4, while other first motifs M1 comprise two wavy chevrons 4. Furthermore, the first motif M1 located at 6H comprises a greater number of chevrons 4, with smaller widths and spacings than the other first motifs M1. The second motifs M2 are identical and correspond to portions of the trailing edge comprising a chevron 4.

[0095] Figure 6H represents a configuration in which the first motifs M1 are identical to each other and correspond to portions of the trailing edge without chevrons. The second motifs M2 are not identical to each other, and correspond to portions of the trailing edge comprising three chevrons 4, of different amplitudes from one motif M2 to another, and decreasing in particular towards the bottom, i.e. from 12H to 6H.

[0096] Figures 7A to 7F show alternative examples of first pattern M1 and second pattern M2 structures. In Figure 7A, the first pattern M1 comprises a chevron 4, and the second pattern M2 comprises two chevrons 4 with a larger amplitude than the amplitude of the chevron 4 in the first pattern M1. The configuration in Figure 7B is similar to that in Figure 7A, but differs in the shape of the chevrons 4, the chevrons 4 having a curved or sinusoidal, rather than pointed, end. In Figure 7C, the first pattern M1 and the second pattern M2 each comprise a chevron 4, identical in shape at the tip, but with a different amplitude. In Figure 7D, the first pattern M1 and the second pattern M2 each comprise a chevron 4, identical in shape at the crenellation, but with a different amplitude. In Figure 7E, the chevrons 4 have a wavy shape.The first patterns M1 include a chevron 4, and the second patterns M2 include two chevrons 4 of greater amplitude. In Figure 7F, the chevrons 4 have a wavy shape. The first patterns M1 and the second patterns M2 each include a chevron 4, of a different amplitude.

[0097] Figure 8 shows alternative examples of first and second patterns M1, M2 distributed along the trailing edge of the outlet nozzle 12', whose chevrons 4 have different geometries and / or amplitudes. The advantage of chevrons with different geometries is that they can reduce the correlation of noise sources along the nozzle's trailing edge. This is useful for reducing noise generated during the passage of the boundary layer through the nozzle's trailing edge, as well as for promoting jet mixing.

[0098] Fig. 9 corresponds to the case of a shrouded twin-flow turbomachine 1 shown in Figure 3A, comprising a first outlet nozzle 12 and a second outlet nozzle 22. Each of the outlet nozzles 12, 22 comprises, along its respective trailing edge 112, 222, first motifs M1 and second motifs M2. In particular, the first motifs M1 of the second nozzle 22 are chevron-free and extend over an angular range A0, corresponding to the azimuthal positions of the OGV blades 30, and the second motifs M2 of the second nozzle 22 extend over an angular range A0' and include three chevrons 4, corresponding to notches along the trailing edge 222. Furthermore, the chevrons 4 of the trailing edge 122 of the first nozzle 12 correspond to undulations of the trailing edge, the first patterns Ml' of the first nozzle 12 corresponding to the hollows of the undulations extend over an angular range A02, corresponding to the azimuthal positions of the blades 40 of TRF.

[0099] A second embodiment according to the present description is then shown with reference to [Fig. 10], representing, on the one hand (on the left side of [Fig. 10]), three trailing edges of nozzle 12 comprising chevrons 4, and on the other hand (on the right side of [Fig. 10]), two examples of a detailed view of the trailing edge 122, 122' in a radial section plane AA'. In order to simplify the description of this embodiment, the chevrons 4 are shown identical to each other, without any distinct patterns. It will nevertheless be understood that the description of the second embodiment below applies to the various examples described previously with reference to the first embodiment.

[0100] In this embodiment, the space between two rafters 4 is filled at least in part, in this example totally filled, by a porous material 13. In an alternative example, corresponding to the leftmost nozzle on [Fig. 10], the rafters 4 themselves comprise the porous material 13. The porous material can be a metallic foam that can be permeable between the inner faces 12a and outer faces 12b of the trailing edge 122 of the nozzle 12 in order to promote the mixing of the flow and to attenuate the noise by visco-thermal effects in the cavities of the porous material. Alternatively, the porous material 13 can be located on the inner face 12a of the trailing edge 122', delimiting the primary flow, and / or on the outer face 12b of the trailing edge 122', delimiting the secondary flow, being isolated from the inner face 12a or outer face 12b by an extension 123 of the trailing edge 122'.This helps to limit the interference of the porous material 13 on the boundary layer on the secondary flow and / or on the jet.

[0101] A third embodiment according to the present exposition is described with reference to [Fig. 11], which shows, on the one hand (on the left side of [Fig. 11]), two trailing edges of nozzles 12 comprising chevrons 4, and on the other hand (on the right side of [Fig. 11]), a detailed view of a trailing edge according to the third embodiment. In order to simplify the description of this embodiment, the chevrons 4 are shown to be identical to one another, without any distinct patterns. It will nevertheless be understood that the description of the third embodiment below applies to the various examples described previously with reference to the first embodiment.

[0102] In this embodiment, the space between two rafters 4 is filled at least partially, in this example completely filled, by metal strips 14, the latter being able to be formed by slots made along the trailing edge. In an alternative example, corresponding to the lower nozzle in [Fig. 10], the The chevrons 4 themselves comprise metal strips 14. The plurality of metal strips 14 thus forms a metal brush in which each strip 14 extends axially over a distance h from the trailing edge, and has a width E in the azimuthal direction. Furthermore, each metal strip 14 is spaced a distance L from an adjacent metal strip 14, L and E preferably being substantially equal to each other, and L and E being between 10 and 9h. It should be noted that the distances h, E, and L, in other words h(0), E(0), and L(0), can vary depending on the azimuthal position 0. Preferably h(0) / E(0) > 10.

[0103] A fourth embodiment according to the present description will be described with reference to [Fig. 12], representing a trailing edge of a nozzle 12 comprising chevrons 4. In this embodiment, the outlet nozzle 12 comprises an upstream portion 124, and an annular cowl 126 detachably attached to the upstream portion 124 by fastening means 128. The fastening means 128 may comprise a first flange disposed at a downstream end of the upstream portion 124, and a second flange disposed at an upstream end of the annular cowl 126, the first and second flanges being fastened together by screw / nut assemblies, for example, arranged at different azimuthal positions. In order to prevent delamination and limit aerodynamic losses, a protective cowl 129 having a profiled structure may be installed to cover the fastening means 128.The number of screws / nuts along the flanges can vary between 2 and 500 depending on the perimeter of the outlet nozzle 12.

[0104] In this embodiment, the trailing edge 122 comprising the plurality of chevrons 4, is disposed on the annular cover 126, the latter being removable and able to be replaced, in particular in the event of damage to the chevrons 4, or simply removed for repair.

[0105] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims

Claims

1. Aeronautical thruster (1, 1') configured to accommodate at least one internal air flow, comprising N stator vanes (40, 32, 30), where N > 2, distributed circumferentially around a central axis (A), at least one outlet nozzle (12, 12', 22) through which the at least one internal air flow is ejected, extending around the central axis (A) and being arranged downstream of the stator vanes (30, 32, 40), a trailing edge (122, 122', 222) of the outlet nozzle comprising a plurality of chevrons (4) distributed circumferentially around the central axis, said trailing edge (122, 122', 222) comprising: - N first trailing edge patterns (Ml) each extending, in a azimuthal direction, over an angular range A0 including one of the N stator blades (30, 32, 40), the first patterns (Ml) being portions of the trailing edge comprising at least one chevron (4) or being portions of the trailing edge not having a chevron (4),and - N second trailing edge patterns (M2) distinct from the first trailing edge patterns (Ml) and extending, in the azimuthal direction, over an angular range A0' not including any of the N stator blades (30, 32, 40), the second patterns (M2) being portions of the trailing edge comprising at least one chevron (4) or being portions of the trailing edge not having a chevron (4), the number of first patterns (Ml) distinct from one another being between 1 and N, and the number of second patterns (M2) distinct from one another being between 1 and N, each angular range A0 including one of the N stator blades being centered on a main axis (X2) of the blade which is the pitch change axis when the stator blades are variable pitch stator blades, and being such that A0min < A0 < A0max, where A0min = 360 / (36*N) and A0max=36O / (N+l), A0min, A0 and A0maxexpressed in degrees.,

2. An aeronautical thruster (1, 1') according to claim 1, wherein the first trailing edge pattern (M1) is a portion of the trailing edge (122, 122', 222) comprising at least one chevron (4), the second trailing edge pattern (M2) being different from the first trailing edge pattern (M1) by at least one, preferably at least two of the number, amplitude, width, spacing or geometry of the chevrons (4).

3. Aeronautical propeller (1, 1') according to claim 1 or 2, in in which the first trailing edge pattern (M1) and / or the second trailing edge pattern (M2) are not homothetic geometric patterns.

4. An aeronautical propeller (1, 1') according to any one of claims 1 to 3, wherein the second trailing edge pattern (M2) is a portion of the trailing edge (122, 122', 222) comprising at least two chevrons (4).

5. Aeronautical thruster (1, 1') according to any one of claims 1 to 4, in which the at least one first trailing edge pattern (M1) and / or the at least one second trailing edge pattern (M2) comprises at least two chevrons (4) of different amplitudes and / or widths and / or geometries.

6. An aeronautical thruster (1, 1') according to any one of claims 1 to 5, wherein, when the at least one first trailing edge pattern (M1) and / or the at least one second trailing edge pattern (M2) comprise two chevrons (4) so as to form at least one gap between said at least two chevrons (4), the at least one gap is filled at least in part with a porous material (13).

7. An aeronautical thruster (1, 1') according to any one of claims 1 to 5, wherein, when the at least one first trailing edge pattern (M1) and / or the at least one second trailing edge pattern (M2) comprise two chevrons (4) so as to form at least one gap between said at least two chevrons (4), the at least one gap is filled at least in part by a plurality of metal lamellae (14).

8. An aeronautical thruster (1, 1') according to any one of claims 1 to 7, comprising an upstream portion (124), and an annular cover (126) configured to be detachably attached to the upstream portion (124), a downstream end of the annular cover (126) comprising the plurality of chevrons (4).

9. An aeronautical thruster (1, 1') according to any one of claims 1 to 8, wherein S / C < 5, where S is the distance between the trailing edge of the at least one stator blade (40, 32, 30) at a recess of the stator blade on a casing (10, 10', 20) of the thruster and the point of the trailing edge of the outlet nozzle closest to the stator blade in the direction of the central axis (A), and C is the chord of the stator blade measured at the recess.

10. Aeronautical propeller (1, 1') according to any one of the claims- dications 1 to 9, the aeronautical propeller being a ducted twin-flow turbojet comprising a first outlet nozzle (12) through which a first internal air flow (F1) is ejected and a second outlet nozzle (22) through which a second internal air flow (F2) is ejected, a trailing edge (122, 222) of each of the first and second outlet nozzles (12, 22) comprising a plurality of chevrons (4), at least one first stator vane (40) being arranged in the first internal air flow upstream of the first outlet nozzle (12), and at least one second stator vane (30) being arranged in the second internal air flow upstream of the first outlet nozzle (12) and the second outlet nozzle (22), the trailing edge (122, 222) of each of the first and second outlet nozzle (12, 22) comprising at least one first pattern (M1) and at least one second trailing edge pattern (M2).

11. Aeronautical propeller (1, 1') according to any one of claims 1 to 9, the aeronautical propeller being an unducted dual-flow turbojet comprising an outlet nozzle (12') of which an internal surface delimits the internal air flow and of which an external surface delimits an external air flow, a trailing edge (122') of the outlet nozzle (12') comprising a plurality of chevrons (4), at least a first stator vane (40) being arranged in the internal air flow upstream of the outlet nozzle (12').

12. An aeronautical thruster (1, 1') according to claim 11, comprising at least one second stator vane (32) arranged in the external air flow upstream of the outlet nozzle (12'), the trailing edge (122') of the outlet nozzle (12') comprising at least one first pattern (M1) and at least one second trailing edge pattern (M2), the at least one first trailing edge pattern (M1) being arranged such that the angular range A0 over which it extends includes the stator vane axially closest to the trailing edge (122'), among the at least one first stator vane (40) and the at least one second stator vane (32).

Images