A structure having a profile with inclined serrations

Abstract

An aircraft turbine engine comprising an annular wall (160) for separating the flow downstream of an upstream fan (14), first stationary vanes (24) for directing the main flow and second stationary vanes (26) attached to the annular separating wall (160), said wall having a profiled section of at least one flow, the profiled section having a leading edge with a profile (28) presenting a sawtooth profile (28) exhibiting successive teeth (30) and grooves such that, along the leading edge, from a first position (21) to a second position (23), the teeth are inclined respectively towards the second position or towards the direction of inclination of the flow or along the direction of the camber line (240) of the first vane. Alternatively, the grooves (32) are angularly interposed between two first circumferentially successive vanes.

Description

Technical Field

[0001] This invention relates to the field of aeroacoustic management of aerodynamic irregular structures, such as in aircraft turbines or test benches of such turbines, or on stationary or rotating blades on the main inlet slats of a turbine (in this case, a dual-flow turbine engine). Background Technology

[0002] A dual-flow turbine equipped with a fan (referred to as upstream, and thus partially located upstream of the turbine) and a rectifier arranged in the secondary flow and having fixed blades of the type described above (guide vanes) found on the rectifier, for example, on an OGV (outlet guide vane) or on a rectifier arranged downstream of the rotating body to rectify the airflow.

[0003] For some turbine engines, it is anticipated that the fan diameter will be increased and the length of the suspension pods fixed to the aircraft will be shortened, thereby reducing the distance between the fan and the inlet guide vanes of the IGV (Inlet Gas Ventilation Vehicle), and the distance between the OGV (Outlet Gas Ventilation Vehicle) and the main inlet slats. In this type of engine, the wake of the fan with IGV, OGV, and slats is one of the major and widespread sources of noise.

[0004] In addition to this observation on turbines, other areas of turbines, as well as aerodynamic irregularities (wings, open rotor blades-open rotors, etc.), face the problem of aeroacoustic management.

[0005] Therefore, particularly in the field of aircraft, it has been proposed to use aerodynamic irregular structures with irregular leading and / or trailing edges, which have a serrated profile with continuous teeth and recesses after the leading and / or trailing edge lines.

[0006] Therefore, the serrated profile extends along the leading and / or trailing edges, that is, it extends along the elongation direction of the structure at the leading and / or trailing edges.

[0007] While the "sawtooth" profile can reduce the emitted broadband noise, it does affect the flow around the profile. As a result, aerodynamic characteristics (aerodynamic losses, lift, boundary layer stall, etc.) are significantly affected.

[0008] In addition, airflow generated axially (hereinafter referred to as the X-axis, also known as the total axis) downstream of rotating structures (such as downstream of turbine fans towards the main airflow slats), or airflow that may be affected by interfering structures (such as the wings of an aircraft fuselage, or the stabilizers of the tail), is a vortex and is strongly influenced by the rotational direction of the air or fan. Summary of the Invention

[0009] One goal here is to optimize the implementation of the sawtooth pattern in order to reduce the noise level by minimizing the impact on aerodynamic characteristics.

[0010] Therefore, a turbine for an aircraft is proposed, wherein the turbine is:

[0011] - It has a main shaft (X), around which the rotating components of the turbine rotate, the rotating components including the blades of the front fan.

[0012] -Including those with a leading edge:

[0013] --An annular airflow partition wall downstream of the front fan divides the airflow into a main stream and a secondary stream.

[0014] --The first guide vane (called IGV) used to guide the main flow (Fp) in a turbine, and

[0015] --A second guide vane (referred to as an OGV) for guiding secondary flow in the turbine, the first and second guide vanes being connected to the annular airflow partition wall, and

[0016] - It is provided with at least one irregular structure, wherein the irregular structure is:

[0017] --The leading edge has a serrated profile, the serrated profile being provided with continuous teeth and recesses, and

[0018] --This causes the teeth of the serrated profile to tilt towards the second position along the leading edge, from the first position to the second position.

[0019] The turbine is characterized in that at least one of the following features a), b), and c) has been verified;

[0020] a) The teeth are circumferentially surrounding the main shaft (X) and downstream of the front fan, and are respectively inclined (angle β) relative to the main shaft (X) in the normal tilt direction of airflow (hereinafter U), so as to generally face the main shaft (X).

[0021] b) On the annular airflow partition wall where the teeth are present, the teeth are oriented along the arcuate direction of the first guide vane (IGV) at the leading edge.

[0022] c) Around the total axis (X), at least some of the recesses of the sawtooth profile are angularly offset relative to the angular position of the first guide vane, such that the at least some recesses are angularly inserted between two circumferentially continuous first guide vanes.

[0023] In fact, considering the geometry of the contour structure currently considered effective and suitable, the teeth of the sawtooth contour will be advantageously asymmetrical with respect to the perpendicular line passing through the leading edge line of the tooth tip in question.

[0024] For this type of inclined tooth, the above phenomena should be better taken into account, so that the surface of the clamp can be as fully effective as possible in achieving the desired acoustic effect.

[0025] Another advantage is that the airflow generated axially downstream of the fan is then considered as a vortex, and is strongly influenced by the fan's rotation direction and speed.

[0026] Typically, at least for a profile with a periodic elementary geometry without excessive distortion (see above), it must be found at the leading edge that the generated airflow or flow bypasses the profile at the tooth (or top) and accelerates near the recess.

[0027] In this case, as mentioned above, one advantage of specifying that at least some of the recesses are angledly inserted between two circumferentially continuous first guide vanes (IGVs) is to avoid excessive turbulence and / or overspeed regions in the leading edge shell region of the first guide vanes (IGVs).

[0028] Furthermore, one advantage of orienting the teeth along the arc of the IGV at the leading edge is the mechanical simplicity of the solution.

[0029] However, the direction of the rotating airflow changes with the fan speed (i.e., the engine speed).

[0030] Therefore, two attractive approaches are proposed:

[0031] (a) From an aeroacoustic perspective, the tooth inclination was fixed under the most attractive operating conditions; then, the common inclination for all teeth of the same structure was fixed; or

[0032] (b) On a turbine or aircraft equipped with at least one of the airfoil structures described above, the angle of the sawtooth airfoil teeth varies according to the engine speed of the turbine.

[0033] Solution (b) is more technically relevant because it allows for optimization of the tooth tilt based on the operating phase of the engine and / or aircraft.

[0034] Solution (a) is mechanically simpler, and its compromises are satisfactory.

[0035] Another approach, which can be applied to another part of an aircraft or turbine, can be used to provide a wing structure in which the wave (or corrugated) shape will remain periodic, but with different teeth and / or different recesses between them in at least some cycles (sequential sets of teeth).

[0036] Therefore, under fixed conditions, the profile teeth at the leading and / or trailing edges can be more precisely adapted to the complexity and variability of the received airflow.

[0037] In terms of shape, it has been suggested that the teeth and recesses of the serrated profile should each have a wave-like (wavy) shape with a rounded or more pointed top.

[0038] The rounded top reduces the localized high concentration of mechanical stress, thereby extending the service life of the component.

[0039] The pointed tip offers the potential for increased noise reduction.

[0040] Furthermore, sidewalls that provide locally straight lines for separately shaped teeth and recesses can generate a certain degree of anti-correlation between noise sources along the leading and / or trailing edges.

[0041] Understandably, irregular structures other than the main air inlet nozzle, IGV, or OGV can benefit from the considerations outlined here.

[0042] The wing structure can be one of the aircraft structures (i.e. components), including aircraft wings, aircraft wing slats or flaps, aircraft engine support towers, vertical tail fins, aircraft stabilizers, helicopter blades, propellers, and turbojet engine blades.

[0043] In fact, in the above-mentioned cases, the existence of such a proposed sawtooth profile allows for the handling of a fine problem related to both static (with the presence of intake structures, blades, etc.) and dynamic (blade rotation, considering certain flight configurations, etc.) aero-acoustic management issues, especially for front fan turbines, where the acoustic / aerodynamic interference problems are very complex and the resulting noise is very noticeable. Attached Figure Description

[0044] The invention will be better understood by referring to the accompanying drawings and by reading the following description, which is given by way of non-limiting example, and other details, features and advantages will become apparent if needed, wherein:

[0045] - Figure 1 This is a longitudinal cross-sectional view (X-axis) of a conventional turbine in an aircraft.

[0046] Regarding the solution according to the invention, Figure 2 The upstream region (slat) of the partition wall between the main and secondary flows is shown;

[0047] - Figure 3 It can be Figure 2 Detailed drawing III, or possibly a partial serrated outline of a helicopter blade, fan blade, rotor or downstream guide vane, leading edge slat, or aircraft flap.

[0048] - Figure 4 Corresponding to Figure 1 Detailed drawing IV;

[0049] - Figure 5-9 Various forms of the fixed tooth serration profile according to the present invention are shown;

[0050] - Figure 10-11 The illustration depicts an assumption of a variable-orientation sawtooth tooth profile, and

[0051] - Figure 12 The figure shows a schematic diagram of the aircraft support structure according to the present invention. Detailed Implementation

[0052] refer to Figure 1 A turbojet engine 10 of an aircraft 100 is schematically shown and defined as follows:

[0053] The pod 12 serves as the outer shell for various components, including the front ( Figure 1 The front fan 14 (located upstream: AM) on the left side of the middle section has blades that rotate around axis X.

[0054] Downstream of fan 14 (AV), the airflow (partial illustration in...) Figure 4 The airflow (38 in the middle) is divided into primary and secondary airflow by the separator flaps 16 of the annular wall 160. When entering the low-pressure compressor 22 at the inlet guide vane IGV 24, also known as the first guide vane, the primary airflow flows through the internal annular air passage or main pulse 18. The secondary airflow flows toward the outlet guide vane OGV 26 (also known as the secondary guide vane), and then toward the engine outlet by the separator slats 16 into the external annular air passage 20 (secondary pulse).

[0055] exist Figure 2 In the image, we can see more precisely the front part 161 of the separator slat 16, which includes a leading edge 164a located at the uppermost point, and at the leading edge 164a, the outer wall 162 of the separator slat 16 meets the inner wall 163 of the separator slat 16, with the upper wall 162 forming the inner shell of the secondary pulse 20.

[0056] For all practical purposes, in this document, axial direction refers to any object extending along or parallel to the longitudinal axis (X) of rotation of the relevant components of the turbine, which in principle is the main axis of rotation of the turbine and the longitudinal axis of the aircraft, for example... Figure 12 The diagram shows the longitudinal axis of the aircraft. Any object in the radial (Z-axis) and circumferential directions is an object that extends radially to and around the X-axis, respectively. All objects radially relative to the X-axis are both internal and external. Therefore, inner wall 163 is the radially inner wall of separator slat 16. Moreover, any references to upstream and downstream should be considered in conjunction with the airflow in the turbine (or its components) under consideration: these gases enter upstream and exit downstream, generally circulating parallel to the X-axis.

[0057] Furthermore, the accompanying drawings and related specifications have been defined with reference to the conventional orthogonal reference numerals XYZ, wherein the X-axis is as described above.

[0058] The separator slats 16 are hollow, with the outer surface of wall 162 serving as the inner boundary of the outer annular air passage 20 for receiving secondary flow, and the inner surface of wall 163 serving as the outer boundary of the inner annular air passage 18 for receiving mainstream flow.

[0059] The inner wall 163 of the separator slat 16 forms the outer casing of the low-pressure compressor 22.

[0060] Although the axial offset (X) of the leading edge 164a of the separator slat 16 downstream of IGV 24 is smaller than that of the OGV 26 with the same leading edge 164a, the portion of the upstream component 161 directly adjacent to the leading edge 164a of the separator slat 16 is obvious.

[0061] As described above, in order to limit the aeroacoustic management of noise generated in this region, the leading edge 164a is therefore expected to have a serrated profile 28 with continuous teeth 30 and recesses 32, for example, as Figure 5-6 The example is shown in the image.

[0062] However, structures other than turbines, such as turbojet engines 10, may be relevant to the solutions of the present invention and benefit from all or part of the features of the claimed invention having a leading and / or trailing edge with a serrated profile 28 having continuous teeth 30 and recesses 32, features which would then be applied to them rather than turbines, as claimed.

[0063] Figure 12 An aircraft 100 is shown, on which irregular structures with this profile 28 are present on the leading edge, on the wing 38, on the pylon 41 supporting the engine 42 of the aircraft, on the tail fin 44 of the turbine engine, the stabilizer 46, the propeller or blade 48 (typically an open rotor), and the profile is serrated.

[0064] also, Figure 3 The image shows a partial serrated profile 28 on a helicopter blade, fan blade, leading edge slat, or aircraft flap of a rotor or rectifier, which can be identified as 50.

[0065] What all these aerodynamic profiles have in common is that they generate a boundary layer on the downstream surface, and thus generate turbulence.

[0066] Regardless of the application, for any profile 28 with jagged edges, we will consider it to have the following defined fluctuations:

[0067] - Along the elongation direction (L) of the leading or trailing edge, a basic geometry that repeats itself, two identical (or quasi-identical, when the two consecutive elementary geometries have a small variation of + / -30% in terms of geometry) undulations, for example Figure 5 , 7 34 and 36, along the direction L, have the same distance λ between them in that direction, and

[0068] - The maximum amplitude h perpendicular to the direction L.

[0069] Furthermore, the L direction is the direction in which the leading edge extends, and when viewed along its entire length, the leading edge may be confused with the leading edge 164a. This direction L may be straight (e.g., for a wing, a fin, a stabilizer), or curved, or even self-enclosed (possibly for a propeller, fan blade, rotor, or rectifier blade (guide vane) or separator slat 16).

[0070] According to the present invention, in order to reduce strong local pressure fluctuations, it is therefore specified in the relevant profile structure that, along the leading edge 164a and / or trailing edge 164b (see... Figure 12 And therefore extending in the direction L, from the first position 21 to the second position 23, the teeth 30 of the sawtooth profile are inclined toward the second position respectively: Figure 12 Angle α, in addition to the influence of the fan, and Figure 6-7 Angle β.

[0071] Figure 6 , 7 A schematic diagram of the above suggestion is shown, with IGV 24 tilted at an angle β in the XY plane relative to the X-axis. Circumferentially around this X-axis, each tooth 30, tilted at the same angle β (but this angle may vary), is aligned with the common IGV 24. The effect of fan 14 rotation has been considered here, assuming that fan 14 rotates in the positive direction of the Y-axis (see...). Figure 1 and along Figure 2 (The arrow pointing in the L direction).

[0072] Based on the initial results of the experiments, an angle α or β between 30° and 60° with respect to the X-axis, preferably between 35° and 45°, would be suitable. Therefore, this does not constitute a limitation.

[0073] Therefore, the leading edge of IGV 24 and the leading edge of tooth 30 are actually generally facing the airflow 38, and their overall tilt orientation (here relative to the X-axis) U is the synthesis of its X-component Ux and Y-component Uy, taking into account the rotation direction of fan 14 as agreed here.

[0074] The teeth 30 are axially asymmetrical with respect to the parallel line of the total axis X, which again passes through the top 31 of the tooth in question.

[0075] The purpose of these guidelines can be considered twofold.

[0076] First, to avoid the interaction between the accelerated flow and turbulence generated in the recess 32 and the leading edge 25 of the IGV. This can significantly reduce the broadband noise of the low-pressure compressor 22. Second, this technical solution can be used to optimize the inlet of the low-pressure compressor 22 and reduce potential aerodynamic losses.

[0077] like Figure 6-7 Similarly, these first guide vanes / IGV 24 can each display an average arc line 240 along their chord to explain the effect of the fan 14 rotation.

[0078] The angle of inclination of the airflow generated by fan 14 depends on the engine speed, i.e., the fan speed.

[0079] Therefore, it is considered to orient the teeth 30 at the leading edge 25 of these guide vanes along the average IGV radian or in the direction of that radian. The selected angle value can be averaged along the span or extension of the IGV, or obtained from the IGV radian value at the blade tip, or fixed under the turbine operating conditions most attractive from an aeroacoustic perspective.

[0080] As shown in the figure, and in this example, the upper surface 241 is guided in the positive Y direction, and the lower surface is guided on the opposite side.

[0081] To further limit the acoustic impact of the rotating airflow generated downstream by fan 14 on IGV 24, particularly as Figure 6-7 As shown, it is also suggested that tooth 30 should be circumferentially oriented around the overall axis X, and horizontally integrally oriented at its leading edge 25 along the direction of the tangent 43 of the average arc line 240 of the IGV24 guide vane. This tangent forms a non-zero angle (β) with the direction of the turbine's overall axis (X).

[0082] One advantage is that it allows for the alignment of these teeth 30 along the direction of the IGV curvature, and again enables the geometry of the compressor 22's intake port to be adapted to its environment. The airflow direction downstream of the fan 12 depends on its rotational speed, so aligning these teeth along the direction of the IGV (which is a stationary component) may be a good trade-off between variable speed and fixed geometry.

[0083] like Figure 7 It can be seen that tooth 30 may be specifically positioned upstream of the leading edge of guide vane IGV 24.

[0084] However, given the size limitations (typically approximately 1-5 cm) that may exist between the slat leading edge and the IGV guide vane, and the possibility of increasing the size / amplitude of the tooth 30, it is recommended that, at least some of the bottom 320 of the recess 32 of the serrated profile 28, along the X-axis, belong to a first surface transverse to the X-axis, the first surface being in... Figure 6 The middle is marked as Y1 and Figure 7 Marked as Y2, the first surface is positioned at ( Figure 6 ) or further downstream than the second surface, which is also transverse to the X-axis (AV); Figure 9 The second surface is Figure 6 The middle is marked as Y'1 and in Figure 7 Marked as Y'2, at least some of the leading edges 25 of the guide vane IGV 24 belong to the second surface. Although illustrated, this is a priori independent of the shapes of the teeth 30 (top) and the recess 32 (bottom 320).

[0085] In this respect, the teeth 30 and recesses 32 of the serrated tooth shape 28 will respectively exhibit rounded tops (such as... Figure 6 , 9 Or 11) or sharp top ( Figure 7 The waveform shape is designed to facilitate effective noise reduction by minimizing the mechanical stress supported by that geometry.

[0086] Regarding the sidewall shape of these teeth 30 and recesses 32 (one of which is in Figure 7 The denoted 300) can be represented individually or locally as flat ( Figure 7 This facilitates decorrelation of noise sources along the leading edge and makes the geometry easier to manufacture.

[0087] Figure 10 The dashed lines in the diagram illustrate that the inclination of tooth 30, with its serrated profile, can vary depending on the turbine's engine speed and / or the aircraft's operational phase (typically flight phase). In this example, this is OGV 26.

[0088] By pivoting these teeth 30, a conventional mechanism, controlled by control logic, for example, coupled to a servo system taking into account engine speed, can then move along the elongation direction L, around axes that are parallel to each other but perpendicular to that elongation direction L (see in...). Figure 10 and Figure 11 These axes (marked as 30a) change their tilt.

[0089] Therefore, as Figure 11As shown, depending on the engine speed, a slat geometry 28 with a wave-shaped leading edge can be achieved, for example, where the angle of the tooth 30 is variable. The figure shows a simplified representation of the airflow line 38 and the IGV24 guide vane, where the orientation here is “angularly relative” between the orientation of the IGV and the tooth 30: in this example, the tooth 30 is oriented at an angle toward side 23, and the IGV24 is oriented at an angle toward side 21.

[0090] Furthermore, since the teeth 30 are arranged periodically along the elongation direction L, they can be completely identical, such as... Figure 6 or Figure 7 As shown. However, while maintaining the irregular structure with a periodic undulating shape, such as Figure 9 As shown, it is foreseeable that (sequential) teeth (groups) 30 will be different from each other (e.g., see teeth 301 and 302) at least in certain cycles; the same applies to the recesses between them (e.g., see recesses 321 and 322).

[0091] Therefore, this elementary geometry will have several waves, two in this example.

[0092] Therefore, under fixed conditions, profile teeth can be more precisely adapted to the complexity and variability of the received airflow.

[0093] Still on slat 16, in order to benefit from favorable aerodynamics, particularly at the intake of low-pressure compressor 22, at least some recesses 32 of the serrated profile 28 around the X-axis are also specified, which can be angularly offset relative to the angular position (circumferentially) of guide vane IGV 24, so that these recesses 32 are inserted along the L direction between two circumferentially continuous first guide vanes IGV 24, as... Figure 8-9 As shown.

[0094] In these figures, the IGV 24 is even placed axially (X) within the continuous teeth 30; more precisely, each chord 242 of the IGV 24 is placed substantially aligned with the top of the tooth 30 preceding the upstream (AM) of the IGV, according to the general direction U of the airflow 38 impacting it.

[0095] If the above explanation and commentary have already been made with reference to the leading edge in relation to the accompanying drawings, the trailing edge can be considered alternatively or additionally in the wing sawtooth pattern, for example, the trailing edge 164b (line) with profile 28, as... Figure 12 As shown.

[0096] At the trailing edge, noise sources are typically associated with the interaction between turbulence in the boundary layer of the profile and the trailing edge.

[0097] It should be understood that, generally, the solutions proposed above have the objective of reducing broadband noise generated by these profiles (blades, OGV, IGV, slats, etc.) by minimizing the impact on the aerodynamic characteristics of the structures that carry them and / or surround them, especially those located downstream.

Claims

1. A turbine (10) for an aircraft, said turbine: - Having a common axis (X), the rotating components of the turbine rotate about the common axis, the rotating components including the blades of a front fan (14), -Including those with a leading edge (164a): --An annular airflow partition wall (160) downstream of the front fan (14) divides the airflow into a main flow and a secondary flow. --The first guide vane (IGV 24) used to guide the main flow (Fp) in the turbine, and --The second guide vane (OGV 26) for guiding the secondary flow in the turbine, the first guide vane (IGV 24) for guiding the main flow (Fp) and the second guide vane (OGV 26) for guiding the secondary flow (Fs) are connected to the annular airflow partition wall (160), and -Having at least one irregular structure, the irregular structure being: --A serrated profile (28) is provided at the leading edge (164a), the serrated profile having continuous teeth (30) and recesses (32), and --so that, along the leading edge (164a), from the first position (21) to the second position (23), the teeth (30) of the serrated profile are inclined toward the second position, respectively. Its features are: a) The teeth (30) are circumferentially positioned around the total axis (X) and downstream of the front fan, each inclined (β) relative to the total axis (X) in a generally inclined direction (U) toward the airflow (38) to generally face it. The individual inclination angle (β) of the serrated profile teeth (30) varies according to the engine speed of the turbine, and b) On the annular airflow partition wall (160) where the tooth is located, the tooth is oriented at the leading edge along the arc line (240) of the first guide vane (IGV 24).

2. The turbine according to claim 1, wherein, The teeth (30) and recesses (32) of the serrated profile each have a shape with locally straight sidewalls (300).

3. The turbine according to claim 1, wherein, The teeth (30) and recesses (32) of the serrated profile are respectively wavy in shape, with rounded or more pointed tops (31).

4. The turbine according to claim 3, wherein, The waveform shape is periodic and has teeth (30) and / or recesses (32) that are different from each other in at least some periods.

5. Aircraft (100), including: - At least one turbine (10) for movement, and - The irregular structure according to any one of claims 1 to 4.

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