RU2789369C2 - Profiled structure for aircraft or gas-turbine engine - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to a profiled structure elongated in a direction, in which the structure has a length blown with an airflow, and transversely to which the structure contains front edge (164) and/or rear edge, at least one of which is profiled and has, in the specified direction, elongations of serration (28a), formed with cogs (30) and recesses (32) following each other. Along the profiled front edge and/or rear edge, cogs (30) and recesses (32) following each other are made only on part of the specified length blown with an air flow, on which an amplitude and/or an interval between cogs monotonously alternate, except for several cogs nearest to each end of the specified part, while remaining part (280) of the specified length is smooth.

EFFECT: invention provides reduction in noise, decrease in aerodynamic losses, reduction in mechanical stresses.

14 cl, 25 dwg

Description

This invention relates to the field of aeroacoustic testing of aerodynamically shaped structures or profiles of aerodynamic elements, such as, for example, fixed blades or rotor blades in a gas turbine engine for an aircraft or on a test bench for such gas turbine engines, or at the nose of an airflow intake the first circuit of a gas turbine engine.

This type of fixed vane is represented, for example, by fan outlet guide vanes (EDA) or straightening vanes located downstream of the working stage to straighten the air flow.

This type of rotor blade is present, for example, on a rotor wheel in a gas turbine engine, such as a fan or an unhooded wheel, for example.

Thus, the invention relates to both canned gas turbine engines (turbofan engines) and non-hooded gas turbine engines (open rotors). An example will be presented for a bypass gas turbine engine with a (front) fan and a straightening vane located in the secondary circuit flow path.

In particular, in Ultra-High Bypass Ratio (UHBR: cowl-fan engine configuration with a very high bypass ratio greater than 15) turbojet engines, it has been proposed to increase the fan diameter and reduce the length of the nacelle on the aircraft, resulting in a reduction in the distance between fan and inlet guide vanes (VDA) of the compressors, VSA blades and the toe of the air intake of the primary flow. In this type of engine, the interaction of the fan outlet jet with the VHA blades, VSA blades, and nose is one of the sources of the predominant noise.

In addition to this noted shortcoming in a gas turbine engine, other areas of gas turbine engines, as well as aerodynamically profiled structures (wings, open rotor blades - open rotor, pylon, etc.) face the aeroacoustic problem of interaction with the air flow.

Therefore, in the field of aircraft, it has been proposed to use aerodynamically shaped structures comprising a shaped leading and/or trailing edge, which have a serrated profile along the leading and/or trailing edge line having successive teeth and troughs.

This toothed profile is thus formed along the leading edge and/or trailing edge, in other words, in the direction of extension of the structure at the leading and/or trailing edge.

In particular, on profiles with a small chord, as well as on closed profiles, - (line) of the leading and / or trailing edge, elongated along a closed line or length direction, a perimetric line, as on the toe of the air intake of the primary air circuit of a gas turbine engine, - noise in mainly appears at the level of the leading and/or trailing edge, in particular, in the depressions of the serrations, where the pressure drops are more intense.

With regard to the term "chord" used in this text, it should be noted that if there is no "chord", as in the case of the toe (hereinafter referred to as 16) of the separation between the flows of the primary and secondary circuits, it will be considered that the expression "in the direction of the chord (hereinafter referred to as 16) of the profile" corresponds to the direction that will hereinafter be referred to as the "common axis (X)" or "X-axis", i.e. the axis along which the flow of fluid mainly flows on the corresponding profiled structure , and this axis is usually transverse and even perpendicular to the length of the shaped structure, which is located along the specified "direction of extension".

It is clear that the expression "transverse(s)" does not necessarily imply strict perpendicularity.

The invention aims to provide a compromise between noise reduction on this structure, limitations on aerodynamic losses on it, as well as mechanical stresses and integration of the profiled structure into its environment.

In particular, one can take into account the fact that in a number of situations such a shaped structure is subjected to an inhomogeneous and/or anisotropic air flow.

Within the scope of the present invention, several heterogeneous profiles are proposed, in particular with the presence of serrations along a partial extent of the leading and/or trailing edge line.

In particular, a profiled design is proposed:

- elongated in the direction in which the structure has a length exposed to the airflow, and

- transversely to which the structure comprises a leading edge and/or a trailing edge, at least one of which is profiled and has tooth extensions in the indicated direction, formed by successive teeth and cavities,

wherein said profiled structure is characterized in that along the profiled leading edge and/or trailing edge:

- consecutive teeth and depressions are made only on the part of the specified length blown by the air flow, while the rest of the specified length is smooth, and

- on the specified part of the length, with the exception of zones containing no more than three consecutive teeth located at each end (in the immediate vicinity of each end) of the specified part of the length, the serrations have changes in amplitude (d) and / or gap (L2) between two successive peaks of teeth or depressions, while these changes are monotonous.

The advantage is the ability to follow the turbulence cumulative scale rule in the outlet jet, also called the attack stream (see FIG. 19 below). For example, on a VSA blade, the integral scale is usually large near the body and small near the hub (outside the boundary layer). This avoids the wandering nature of the aforementioned real scale change rule.

With such a change(s), developing(s) in accordance with at least one numerical function, which remains either strictly increasing or strictly decreasing, in the corresponding section (essentially on a sequence of at least three teeth or along at least three depressions), where the direction of change is constant, it is also possible to eliminate possible aerodynamic losses or to limit mechanical stresses, or to facilitate the integration of the profiled structure into its environment.

In order to limit mechanical stress and cracking at the level of the valleys and/or reduce manufacturing limitations while still maintaining sufficient attenuation of acoustic levels, it has also been proposed that, at least in the portion of the airflow length where serrations are present, and

- either relative to the mean chord (arithmetic mean of the chord over the length L1; see Figs. 20-25 below),

- either for each chord on each tooth in the indicated direction,

these serrations were observed transversely to the direction of elongation by the ratio: 0.005≤d/c≤0.5, where “d” is the amplitude of the serrations in m, and “c” is the local or average chord of the profiled structure at the place of the serrations in m.

In order to limit mechanical stresses and cracking at the level of troughs and/or reduce manufacturing constraints and/or reduce aerodynamic losses while still maintaining sufficient attenuation of acoustic levels, it has also been proposed that, at least over the portion of said length where serrations are present, the amplitude ( d) and/or the gap (L2) between two successive tooth tops or troughs changed:

- not periodically, or

- in particular, linear (ascending or decreasing), quadratic, hyperbolic, exponential and/or logarithmic.

In order to smooth out mechanical and acoustic transitions between zones and thereby reduce some manufacturing constraints, it has been proposed:

— that along the profiled leading edge and/or trailing edge of the serrations there are monotonous changes in amplitude or spacing between two successive serration tops or troughs, and/or

- that along the profiled leading edge and / or trailing edge and when changing the amplitude and / or the gap between three successive tooth peaks and / or troughs of a wavelength, the serrations smoothly match with the indicated smooth part of the length that is not having them, blown by the air flow , and/or

- so that the serrations end (at the end of the interface with the smooth part) with a transitional section passing along the specified smooth part.

To solve a comparable problem of providing a transition, where there is a trade-off between maximizing acoustic effect and minimizing mechanical stresses, it is proposed that a row of at least two consecutive teeth and two cavities, starting from a specified part of the length, blown by the air flow and not having serrations, has:

- the increasing distance along the specified direction of elongation between two successive tooth tops or troughs, and/or

- increasing amplitude,

moreover, in the direction from the smooth part to the serrations, which will be explained below.

For the same purpose, it has also been proposed that, along the airflow length, the serrations start and/or end with a serration at the level of the fasteners (except in the case of a "toe" design).

In order to promote mechanical structuring and the effect of acoustic limitation, it was also proposed that at the specified smooth part of the length of the specified structure had a longer chord than at the bottom of the nearest cavity.

Depending on the cases, it is provided that along the specified length blown by the air flow, serrations may be absent:

- at least one of the two ends of the specified length, or

- in the intermediate part between these ends and in this case were present at the said two ends,

- in several places of length, separated from each other, for example, were absent at one end and in the section of the intermediate zone.

The first case should ensure the limitation of possible mechanical stresses at the level of boundaries / connections between the specified profiled structure and the area of installation / attachment of the working blade, for example, on a propeller or in a place between two walls of the air flow path.

The second case is to limit serrations where turbulence is greatest and exclude them elsewhere so as not to interfere with aerodynamic behavior in these areas.

The same approach is proposed if several shaped structures are provided that can influence each other, and the object of the invention is a set of shaped structures, each of which has all or part of the above features, in which the respective directions of elongation run radially around the axis of the body of revolution and in which the distance between two successive tooth tops or troughs and/or the amplitude is greater (and therefore longer) at the radially outward end of the airflow length than at the radially inward end of that length.

So, for example, in the case when these profiled structures are ICA blades located at the fan outlet, and with such amplitudes and / or wavelengths (distances between two successive tooth tops or troughs) of serrations, more significant (and, therefore, longer ) near the outer casing (at the top of the ICA blades) than on the stem near the zone between the flow paths, it is possible to compensate for the disadvantages associated with the fact that the vortices at the end of the fan blades are larger and are quite energetic on many turbojet engines.

With this in mind, the subject of the invention is also:

- a canned or non-hooded gas turbine engine with an inlet fan, having a common axis (which may be the aforementioned axis of the body of rotation) and containing a rotor that can rotate about the specified common axis, and a stator, while the stator and / or rotor contain profiled structures, each of which has all or part of the above characteristics,

- and in particular a gas turbine engine in which the stator comprises (or the profiled structure belongs to):

- an annular dividing wall (between the ducts) for dividing the air flow at the fan outlet into the flow of the first circuit and the flow of the second circuit,

- stationary blades of the VCA for directing the flow of the secondary circuit, forming the indicated profiled structures,

- fixed VHA blades for directing the flow of the primary circuit at the compressor inlet, forming the indicated profiled structures, and/or

- a boxed or non-boxed gas turbine engine (whose common axis may be the aforementioned axis of the body of rotation), containing two rotors that can rotate in parallel (about at least one parallel axis) about the specified common axis, and / or one and / or the other of rotors contains the specified profiled structures, each of which has all or part of the above features.

The invention and its other details, features and advantages will be more apparent from the following description, presented by way of non-limiting example with reference to the accompanying drawings.

Brief description of the drawings

In FIG. 1 schematically shows a known aircraft gas turbine engine, a longitudinal sectional view (along the x-axis);

in fig. 2 schematically shows the inlet zone (toe) of the dividing wall between the flows of the first and second circuits using the claimed solution;

in fig. 3 may show either detail III shown in FIG. 2, or a local pattern of a toothed profile that may be present on a helicopter blade, on a fan blade, on a part of a rotor or directing vane, on a leading edge toe, or on an aircraft wing flap;

in fig. 4 shows detail IV, indicated in FIG. 1;

in fig. 5 schematically shows an aircraft containing the claimed structures;

in fig. 6-14 show various tooth profile shapes according to the invention, which may correspond, for example, to zone I in FIG. 1 or 5;

in fig. 15-16 schematically show two other gear profiles according to the invention, in particular with the gears offset in the angular direction (angle α);

in fig. 17 shows a localized enlargement of an example of a zone with serrations according to the invention at the outlet of a fan;

in fig. 18-19 respectively show an axial sectional view illustrating the intensity of swirl in the outlet jet of a fan of a bypass turbojet engine up to the blades of the ICA, and a graph of the corresponding radial change in the integral scale of turbulence (∧) depending on the radius (r) between the inner radius rint and the outer radius rext air flow path, hereinafter referred to as 20;

in fig. 20-22 show parts of the length of the leading and/or trailing edge having serrations with (strictly) monotonic changes in amplitude (d) or spacing (L2); in these figures, the solid lines show the real serration profiles, the thinner wavy lines show the imaginary serration profiles calculated to determine the average chord and representing the control profile, from which the monotonic changes in amplitude and/or gap are determined;

in fig. 23-25 show length portions of a leading or trailing edge with serrations where the serration transformations follow non-periodic and (at least partially) monotonic variation rules such as linear, logarithmic, and parabolic rules, respectively.

Implementation of the invention

Even if this is clearly and not visible to the eye, it should be considered that in all Figs. 2-17 and 23-25, changes in amplitude (d) and/or spacing (L2) between two successive tooth peaks or troughs are monotonic under the above conditions.

In FIG. 1 schematically shows a turbojet 10 of an aircraft 100, which can be defined as follows:

Gondola 12 serves as an outer casing for various organs, among which - in front (on the left in Fig. 1) the input (AM) fan 14.

At the outlet (AV) of the fan 14, the air flow (schematically shown locally in FIG. 4 at 38) is divided by the dividing toe 16 of the annular wall 160 into a primary air flow and a secondary air flow. The air flow of the primary circuit passes through the internal annular air passage or flow path 18 of the primary circuit into the low pressure compressor 22 at the level of the inlet guide vanes 24 VNA. The air flow of the second circuit is deflected by the dividing toe 16 into the outer annular air passage 20 (the flow path of the second circuit) in the direction of the outlet guide vanes 26 of the VSA, then towards the engine outlet.

In FIG. 2 and 3 more specifically shows the front part 161 of the separation toe 16, containing the leading edge 164 closest to the entrance, at which the outer wall 162 of the separation toe 16 is connected to the inner wall 163 of the separation toe 16, while the upper wall 162 forms the inner shell flow path 20 of the second circuit.

In any case, it should be clarified that what will be called axial is that which runs along or parallel to the longitudinal axis (X) of rotation of the corresponding part of the gas turbine engine, while this axis will a priori be the common axis of rotation of this gas turbine engine. Radial (Z-axis) will be called what is located radially to the X-axis, and circumferential will be called what is around it. Inner or outer will be that located radially, that is, opposite the X axis. Thus, the inner wall 163 is the radially inner wall of the separating toe 16. In addition, the definitions of "inlet" and "outlet" should be considered in relation to the passage of gases in the corresponding gas turbine engine (or part of it): these gases enter at the inlet and exit at the outlet, generally running parallel to the aforementioned longitudinal axis of rotation.

In addition, the attached drawings and descriptions related thereto are presented with reference to a conventional X-Y-Z orthogonal coordinate system in which the X-axis is the axis defined above.

The separating nose 16 is formed by two sides: the outer side of the wall 162 serving as a radially inner boundary for the outer annular air passage 20 into which the secondary flow Fs enters, while the inner side of the wall 163 serves as a radially outer boundary for the inner annular passage 18 into which flow Fp of the primary circuit.

The bottom wall 163 of the separating toe 16 forms the outer shell of the low pressure compressor 22.

Even if the axial (X) displacement of the blades BHA 24 towards the outlet relative to the leading edge 164 of the separating nose 16 is smaller compared to the axial displacement of the blades BCA 26 relative to the same leading edge 164, the section of the front part 161 immediately adjacent to the leading edge 164 of the separating toe 16 is open.

In order to reduce the noise produced by the leading edge, for example nose 16, OGV blades 26, BHA blades 24, this leading edge 164 can be provided with a profile with serrations 28 having a sequence of teeth 30 and cavities 32 as shown in the examples in FIG. 6-17.

However, the inventive solution can be applied to designs other than turbine engine designs, such as turbojet 10, and can have a leading edge 164 having a profile with serrations 28 comprising a sequence of teeth 30 and troughs 32.

In FIG. 5 schematically shows an aircraft 100, on which profiled structures with such a toothed profile 28 are present on the leading edge on the wings 39, on the pylon 41 of the engine 42 of the aircraft, on the keel 44, stabilizer 46, blade or blade 48 of an unhooded propeller or on fixed blades 49 (stator) at the outlet of a non-hooded propeller. In this FIG. 5 shows two traction gas turbine engines of an aircraft, containing two unhooded screw groups, each with two rotors 480a, 480b, successive and co-axial, which can rotate parallel to the specified common axis (X), while one and/or the other of these rotors contains profiled structures 1.

In addition, in FIG. 3 is a schematic partial view of a toothed profile 28 that may be present on a helicopter blade, fan blade, part of a rotor or guide vane, leading edge toe or wing shield of an aircraft.

A common feature of all these airfoils is the generation of a boundary layer on the exit surface and hence turbulent flow.

Regardless of the application of the gear profile 28, it can be considered:

- that this airfoil belongs to a profiled structure 1 (or to an airfoil) around which (which) passes air, which is elongated(s) in the Z direction, in which the structure (or profile) has a length L1, which is blown air flow, and

- that, transverse to the Z direction, the structure (or profile) comprises a leading edge 164 and/or a trailing edge 165 (separating toe 16 has no trailing edge), at least one of which is profiled and therefore has a serration in the indicated direction of elongation Z (profile 28) formed by the indicated teeth 30 and depressions 32 following one after another.

Teeth 30 and cavities 32 follow each other in alternation.

To optimize efficiency, the number of teeth 30 and cavities 32 is between 3 and 100.

In order, as indicated above, to take into account that in a number of situations said profile structure 1 is exposed to a non-uniform and/or anisotropic air flow, and in order to provide a compromise between the desired noise reduction, limitation of aerodynamic losses and integration of the profile structure into its environment, it has been proposed so that along the profiled leading edge(s) 164 and/or trailing edge 165, serrations 28 are present in a limited area of length L1 (see FIGS. 7-14).

To complement the decision and for the same purpose, it has also been proposed that:

- at least in the area of the part of the length where there are serrations 28,

- and in particular, with the exception of zones (such as 33 and 35 in Fig. 6) containing no more than three consecutive teeth located at each end of the specified part of the length:

serrations 28 had (see, in particular, Fig. 6, 10, 16 and 20-25):

- transverse to the direction of elongation Z - the amplitude d of the serrations, which varies monotonously, and/or

- in the indicated direction of elongation - the distance L2 between two successive peaks (300, 320 respectively) of teeth 30 or troughs 32, which varies monotonically.

The amplitude d can be measured along the X-axis between the top 300 of the tooth 30 and the bottom 320 of the immediately adjacent valley 32 following it in this direction.

With a ratio between the highest amplitude and the lowest amplitude ranging from 1.2 to 20, including, if necessary, taking into account the transition/interface zone 28a indicated below, the serrations 28 will be simultaneously effective in terms of acoustics, mechanical strength and integration (attachment) into their immediate environment.

In order to supplement this requirement for d and L2 for the same purposes, it is possible to make serrations of 28 profiles from all the solutions indicated below, that is, with radial changes in these serrations; see fig. 7-10.

In particular, successive teeth 30 and depressions 32 will only be located on the part L1a of this length L1 blown by the air flow. The rest of L1b of length L1 will be smooth (i.e. will not have serrations): part 280.

In order to improve this compromise, and in particular to prevent the formation of cracks at the level of the valleys, as shown in FIG. 6, transverse to the direction of elongation Z, the serrations 28 must comply with the ratio: 0.005 ≤ d/c ≤ 0.5, where:

- “d” denotes the amplitude of the serrations in m, and

- “c” denotes the chord of the profiled structure at the place of these serrations in m.

This chord c will either be the middle chord over length L1a or the chord at each serration (one tooth followed by a trough) in the indicated Z direction; see fig. 6, 10 and 20-22.

The search for the aforementioned compromise led to the provision of a transition, also called transition zone 28a:

- where, with a monotonous change and, in particular, as the smooth part 280 is approached, with a general decrease in the amplitude d and/or the gap L2 between two peaks, respectively, 300, 320 consecutive teeth 30 or depressions 32 of the serrations smoothly mate (transition/conjugation zone 28a) with said smooth portion 280; see fig. 7-8, and/or

- where the serrations 28 end (at their end of mating with the smooth part) in a zone 280a which will extend along said smooth non-serrated part 280; see fig. 7-8.

In particular, in this situation, at least a constructive advantage is obtained in that, along the length L1, the serrations 28 begin and end with a serration 30 at the level of the bonds of the zones having serrations, as shown in FIG. 6, 7. Fasteners refer to the insertion of structures into their supports, for example, at the end(s) of the outer casing 53 and/or the central hub 55.

The search for this compromise can even lead to the fact that, in particular, in the transition zone 28a, a row of at least two (preferably three) successive teeth 30 and of two (preferably three) successive depressions 32, starting from the specified part L1b of length, does not containing gears, has:

- increasing distance L2 in the indicated direction of elongation between two successive tooth tops or troughs, and/or

- increasing amplitude d, as shown in FIG. 7, 8.

In addition, providing a longer chord c at the smooth portion 280 than at the bottom (at the tops 320) of the troughs 32 enhances the mechanical structuring and acoustic confinement effect, contributing to the formation of the transition zone 28a.

Further explanations will be focused on the example of the blades VCA 26, since usually we are talking about a critical zone located immediately at the outlet of the fan 14. However, the features under consideration can be extrapolated to other cases of toothed profile 28.

The serrations 28 at the level of the leading edge 164 of the ICA blades 26 may impair the aerodynamic properties of the ICA blade or complicate the mechanical integration of the ICA blade into the flow path 20 (FIG. 1). In order to limit the effect of these gear on the aerodynamic efficiency of the HIS blades, on local mechanical stresses and on their integration, it is provided that such galette is overlapped only from 0.05L to 0.95L of active scope (L1 length) of the VSA blade.

Fig. 11-14 illustrates various situations of such partial zones of gear 28 on the front 164 and/or rear 165 edges.

So:

- in Fig. 11: The serrations 28 are missing from the inner end 281 of the profiles (in this case missing from the blade root of the BCA). This makes it possible to reduce mechanical and/or aerodynamic stresses at the inner end and at the same time maintain sufficient attenuation of the acoustic levels at the outer end 283 (near the outer casing 53 in this example), where the intensity of turbulence and the integrated turbulence scale or characteristic scale of turbulence are large. The serrations near the outer hull could also be useful in order to avoid possible separation of the boundary layer under certain modes or flight conditions.

- in Fig. 12: gear 28 are absent at the outer end of 283 profiles (in this case, they are absent at the top of the VSA blade). This allows you to weaken mechanical and/or aerodynamic stresses at the top and at the same time maintain a sufficient weakening of acoustic levels at the rest of the profile length or avoid a possible breakdown of the boundary layer at some modes at the level of the structure of the structure (support, for example, the central hub 55, to which the ring wall 160, Fig. 2.4).

- in Fig. 13: Serrations 28 are present at the level of the intermediate part of the profile, but absent at the outer 283 and inner 281 ends. This makes it possible to eliminate possible mechanical stresses at the level of connections between the structure under consideration and, in this case, the walls of the flow path 20 (in this example, the outer casing 53 and the hub 55) by eliminating the serrations on the stem 281 and at the top 283 of the ICA blade, while maintaining them. for straightening intermediate turbulent jets.

- in Fig. 14: Garkets 28 are present at the outer 283 and the inner 281 ends, but are absent in the intermediate part of the profile. This allows you to limit the execution of gear in areas where turbulence is the largest, and exclude these gear in other places so as not to violate aerodynamic behavior in these areas. In particular, in the average mode of operation between the small gas mode and the full gas mode, this allows you to limit the breakdown of the boundary layer towards the external 283 and the inner 281 ends.

With regard to the shape of the serrations 28, they may be rounded waves such as sine waves or other shapes such as herringbone as shown in FIG. 16. In FIG. 15, 16, as well as in Fig. 5 (some) teeth 28 have an acute angle of attack α with respect to the X axis.

Depending on the cases, it is also possible to adapt the deflection of the structure 1 (in English “sweep angle”): an acute angle relative to the perpendicular to the X-axis, at the place of the structure.

To enhance decorrelation or phase shift between noise sources along the span, the shaped leading edge 164 and/or trailing edge 165 may be provided to extend along a common curved line with a concavity facing the inlet, as shown, for example, in FIG. 6 or 10.

It is also clear from the foregoing that the considered structure may, as in the non-limiting case of application for ICA blades, belong to a set of profiled structures, each of which has all or part of the above features and whose respective directions of elongation Z run radially around the X axis.

In particular, in the non-limiting case of such BCA 1/26 blades, disadvantages associated with turbulence at the tip of the fan blades 14 can also be compensated for, where they are larger than elsewhere and are sufficiently energetic.

To do this, the distance L2 between two successive teeth or valley peaks 300, 320 and/or the amplitude d are greater (or therefore longer) at the radially outer end 283 of the length L1 than at the radially inner end 281, thus monotonic change rule.

Thus, the amplitudes and/or wavelengths of the respective serrations 26 will be greater (or longer) near the outer casing 53 than near the area between the paths (hub 55/wall 160).

It should also be noted that the invention makes it possible to take into account the local properties of the considered turbulent flow U, for example, at the inlet of the VSA blades, in order to determine the geometry of the waves depending on the radial distribution of the integral scale of turbulence (∧ in Fig. 19) in the outlet jet of the fan 14. In this case, it is possible clarify that the exit jet shown in FIG. 4 can interact with both the ICA vanes (above the toe) and the VCA vanes (below the toe).

In this regard, in FIG. 6 shows a BCA 1/26 blade with waviness optimized depending on the integral scale ∧ of local turbulence along the span. It should be noted that the waviness amplitude d and "wavelength" L2 are much larger near the casing 55 than at the BCA blade root (support/hub 55), outside of the boundary layers. This is due to the turbulence at the end of the fan blade 14.

In FIG. 18 and 19 schematically show the intensity of turbulence and the radial change in the integral scale of turbulence in the outlet jet of the fan 14 at the inlet of the blades of the VSA 26. In this example, starting from 2/3 of the outer radii, the integral scale (∧) of turbulence increases sharply and reaches its culmination just before the outer radius rext. In practice, parabolic or linear variation may be used, as shown by dashed and dashed lines respectively in FIG. 19 to determine the monotonic change in serrations.

In the solutions shown in Fig. 20-22, situations are shown where, in order to account for non-uniform and/or anisotropic airflow and achieve the aforementioned acoustic/aerodynamic/mechanical compromise, it has been proposed that along the shaped leading edge 164 and/or trailing edge 165, at least a portion of the length L1 serrations had a repeating geometric pattern, the shape of which is still stretched or compressed:

- transversely to the direction of elongation (in this case, a varying amplitude is obtained: see d1, d2, ... in Fig. 20; see also Fig. 22), and/or

- in the direction of extension (in this case, a varying length of the repeating pattern in the direction of extension is obtained: see lengths L21-L23 in Fig. 22; see also Fig. 21).

Thus, along the leading edge 164 and/or the trailing edge 165, the serrations (28, 28a) will have, at least on the part of the specified length (L1) blown by the air flow, a geometric pattern transformed by successive scaling through factors, moreover, in the direction of elongation (L2, L21, L22, L23,…) and/or transverse to the extension direction (d, d1, d2,…).

In the first two cases (FIGS. 20-21) of stretching or compressing a repeating "control" geometric pattern, the pattern is retained either in amplitude or in frequency, following the rule of monotonic change (length L2 of the pattern in the direction of extension).

So, in Fig. 20, if we take as a control pattern the gray pattern in the figure (limited by a dash-dotted line), it is seen that along the length L1 the length or frequency L2 of the pattern is preserved and that, on the other hand, the amplitude d varies (d1, d2, ... ). In the situation shown in FIG. 21, everything happens in reverse: the amplitude d is preserved, but the length or frequency L2 of the pattern changes.

In FIG. 20-21, a periodic tooth profile has been modified, formed by a repeating geometric pattern (the "control" pattern, an example of which is shown in gray) having two characteristic directions (see X,r directions in the respective figures, where r ≠ X and, for example, r=Z), through the following transformation: the generic pattern has been brought to the desired scale by a factor in the characteristic direction, while in the other characteristic direction the dimensions of the pattern may remain unchanged (Fig. 20-21) or may follow scaling (Fig. 22) .

Indeed, for heavily acoustically influenced areas, stretches and/or compressions that vary in amplitude and frequency may be preferred, as in the example of FIG. 22: frequency L2 and amplitude d of the repeating geometric pattern change together: L21, L22, L23,… and d1, d2, d3….

Once the relationship between "amplitude" and "frequency" is established, the proportions of the repeating geometric pattern can be maintained; see homothety in FIG. 22.

In FIG. 23-25 schematically represent three situations in which at least a part of the specified length (L1) blown by the air flow, the transformation of the gears follow the rules, respectively:

- linear (Fig. 23),

- logarithmic (Fig. 24),

- parabolic (Fig. 25).

You can also choose a quadratic, hyperbolic, or exponential rule; moreover, by "amplitude" (d1, d2, d3 ...) and / or by "frequency" (L21, L22, L23, ...).

In general, due to the same considerations mentioned above, a non-periodic and monotonic variation in amplitude (d) and/or frequency (L2) of the serrations 28 can be chosen.

Claims (24)

1. Profiled structure for an aircraft or for an aircraft gas turbine engine, - extended in the direction of extension, in which the structure has a length (L1) blown by the air flow, and - transversely to which the structure comprises a front edge (164) and/or a rear edge (165), at least one of which is profiled and has tooth extensions (28, 28a) in the indicated direction, formed by successive teeth (30) and depressions (32), characterized in that along the profiled leading edge (164) and/or trailing edge (165): - successive teeth (30) and depressions (32) are made only on the part of the specified length blown by the air flow, while the rest (280) of the specified length is smooth, and - on the specified part of the length, with the exception of zones (33, 35) containing no more than three consecutive teeth located at each end of the specified part of the length, the serrations (28, 28a) have changes in amplitude (d) and / or gap (L2) between two successive peaks of teeth (30) or troughs, while these changes are monotonous. 2. Profiled structure according to claim 1, in which, at least on the part of the length (L1) blown by the air flow, where the serrations are present, and either with respect to the middle chord, or for each chord on each serration in the indicated direction, these serrations are observed transversely to direction of elongation ratio: 0.005≤d/c≤0.5, where "d" is the amplitude of the serrations in meters and "c" is the chord of the shaped structure at the place of the serrations in meters. 3. Profiled design according to any one of paragraphs. 1 or 2, in which along the shaped(s) leading edge (164) and/or trailing edge (165) and when changing the amplitude and/or the gap between two successive tops of the teeth (30) or tooth troughs (28, 28a) are smoothly mated with the specified smooth part (280) of the length. 4. Profiled design according to any one of paragraphs. 1-3, in which the serrations end in a transition (280a) extending along said smooth portion (280). 5. Profiled design according to any one of paragraphs. 1-4, in which on said smooth length part (280) said structure has a longer chord (c) than on the bottom of the cavity (32). 6. Profiled design according to any one of paragraphs. 1-5, in which, on the specified part of the length, with the exception of the indicated zones, a row of at least three consecutive teeth (30) and three troughs (32) has a strictly increasing distance (L2) along the indicated direction of elongation between two successive tooth tops ( 30) or depressions (32). 7. Profiled design according to any one of paragraphs. 1-6, in which on the specified part of the length, with the exception of the indicated zones, a row of at least three consecutive teeth (30) and three depressions (32) has a strictly increasing amplitude (d). 8. Profiled design according to any one of paragraphs. 1-7, in which along the specified length blown by the air flow, the serrations (28, 28a) are absent: - at least one of the two ends of the specified length, or - in the intermediate part between these ends and are present at the said two ends. 9. Profiled design according to any one of paragraphs. 1-8, in which at least part of the length where the serrations are present, the amplitude (d) and/or the gap (L2) between two successive serration tops (30) or troughs does not change periodically. 10. Profiled design according to any one of paragraphs. 1-9, in which at least on the part of the length where the serrations are present, the amplitude (d) and/or the gap (L2) between two successive tooth tops (30) or troughs varies linearly, quadratically, hyperbolically, exponentially and/or logarithmically . 11. A set of profiled structures, each of which is made according to any one of paragraphs. 1-10, in which the respective directions of elongation run radially around the axis of the body of revolution, while the distance (L2) between two successive tooth tops (30) or troughs (32) and/or amplitude is greater at the radially outer end of the length (L1) , blown by the air stream (U) than at the radially inner end of this length. 12. A gas turbine engine having a common axis (X) and containing a rotor configured to rotate around the specified common axis (X) and a stator, while the stator and / or rotor contain profiled structures (1), each of which is a design according to any of paragraphs. 1-10. 13. Gas turbine engine according to claim 12, in which the profiled structure is: - an annular dividing wall (160) for dividing the air flow at the outlet of the fan of the gas turbine engine into the flow of the primary circuit and the flow of the second circuit, - or fixed blades (26, BCA) for directing the flow (Fs) of the second circuit, forming the indicated profiled structures, - or fixed blades (24, VNA) for directing the flow (Fp) of the primary circuit, forming the indicated profiled structures. 14. A gas turbine engine according to claim 12 or 13, containing two rotors (480a, 480b), which can rotate in parallel about the specified common axis (X), while one and / or the other of the rotors contains profiled structures (1), each of which is the design according to any one of paragraphs. 1-10.

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