Turbine engine blade with leading-edge slots

Abstract

Disclosed is a blade (120) for a turbine engine, in particular for an unducted propulsion fan, having a plurality of slots (200). A radial distance (Δri), in the spanwise direction (Z), from the blade root (123) to at least one slot (200) of said plurality of slots (200) is less than a radial distance (Δre), in the spanwise direction (Z), from the blade head (124) to any slot (200) of said plurality of slots (200).

Description

Description Title of the invention: Turbomachine blade with leading edge slots Technical Field

[0001] The technical field of this presentation is that of turbomachinery and in particular that of propulsive blowers, such as those intended to be driven by a gas turbine engine in aeronautical propulsion. Previous technique

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by different countries. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] The search for minimizing polluting emissions related to air transport involves, in particular, improving all the efficiencies of propulsion systems, and more specifically the propulsive efficiency which characterizes the efficiency with which the energy used is converted into useful thrust effort.

[0007] The primary factors influencing propulsive efficiency are those that directly contribute to thrust generation, notably the propulsive fans. The known guiding principle for improving propulsive efficiency is to reduce the fan's compression ratio, thereby decreasing the airflow velocity at the fan outlet and the associated kinetic energy losses.

[0008] To achieve the same thrust, this decrease in flow velocity at the outlet of the propulsion fan must normally be compensated for by a greater mass flow rate of air, and therefore a larger fan diameter. When this fan is driven by a gas turbine engine, this also normally implies a higher bypass ratio (BPR), which is the ratio between the mass flow rate of the fan's secondary flow and that of the primary flow feeding the combustion chamber of the gas turbine engine.

[0009] To allow for a greater dilution rate, several types of unfaired propulsive fans have been considered, including those known by the English acronyms "USF" and "CROR". In both types, the propulsive fan comprises two rows of blades arranged radially around one or more central axes, one upstream and the other downstream. For the purposes of this discussion, "upstream" and "downstream" are defined in relation to the usual direction of airflow through the fan. The fan. However, in "USF" (Unducted Single Fan) type propulsive fans, only the upstream row rotates around the central axis, while in "CROR" (Counter-Rotating Open Rotor) type propulsive fans, both rows rotate in opposite directions. However, in both types, the blades of each of the two rows can have variable pitch.

[0010] However, increasing the fan's mass flow rate can also lead to a significant increase in its noise emissions, which cannot be mitigated by shortening, thinning, or even removing its shroud. These noise emissions are largely due to interactions between successive rows of fan blades and / or vanes, particularly harmonics of the blade passing frequency (BPF). Significant research and development efforts, notably by the Applicant, have therefore been directed towards reducing these noise emissions. To this end, it has been proposed, notably in US patent 11,560,796, to incorporate teeth or corrugations on the leading edge of the downstream blades or vanes. It has also been proposed, along the same lines, to incorporate slots on the leading edge of fan stator vanes. Description of the invention

[0011] This presentation is the result of technological research aimed at significantly improving aircraft performance and, in this respect, contributing to the reduction of their environmental impact, particularly in terms of noise emissions. To this end, the first aspect of this presentation concerns a turbomachine blade comprising an upper and lower surface extending, in a span direction, over a span from a blade root to a blade tip and, perpendicular to the span direction, from a leading edge to a trailing edge. This blade is defined by a stack of airfoils perpendicular to the span direction where, in each airfoil, the leading edge is separated from the trailing edge by a local chord line following a local chord direction perpendicular to the span direction, and exhibits a plurality of leading-edge slots, each delimited by two lateral slot surfaces.

[0012] In at least one embodiment, a radial distance, along the span direction, from the blade root to at least one slot among said plurality of slots may be less than a radial distance, along the span direction, from the blade tip to any slot among said plurality of slots, or even less than half, or even one-third, of a radial distance, along the span direction, from the blade tip to any slot among said plurality of slots. In particular, the leading edge may be slot-free for less than 25%, or even 35%, of the blade tip span in the span direction. For the purposes of this description, "slot" means a narrow, deep opening, for example, with a ratio of depth, in the local chord direction, to width, in the span direction, greater than or equal to 0.5, or even 1.

[0013] Indeed, leading-edge slots can be more effective in reducing noise emissions near the blade root, since they are more exposed at this point, particularly in unfaired propulsion fans, to the highly energetic boundary layer around the hub. Furthermore, they may present fewer mechanical and / or aerodynamic disadvantages near the blade root than at the blade tip, where the blade chord and / or thickness can be reduced, while the sweep can typically be more pronounced.

[0014] In at least one embodiment, the local chord and / or maximum profile thickness can decrease monotonically towards the blade tip to less than 25%, or even 35%, of the blade tip span in the span direction. This limits the blade mass near the blade tip, which is beneficial from a mechanical point of view, for example, for meeting bird ingestion criteria.

[0015] In at least one embodiment, the maximum profile thickness can even decrease monotonically across the entire span from the blade root to the blade tip. This simplifies the manufacturing process and avoids discontinuities in the maximum profile thickness along the span, which can create points of mechanical weakness. It also helps to minimize discontinuities on the blade surface near the slots.

[0016] In at least one embodiment, no leading-edge sweep angle within 5% of the blade head span along the span direction is less than 40°, or even 45°, or 50°. Indeed, a large leading-edge sweep angle helps reduce noise by increasing the decorrelation of noise sources along the leading edge.

[0017] In at least one embodiment, the blade can have a comparatively low activity factor, for example between 35 and 230, or even between 85 and 165. This allows for a larger chord near the blade foot, which maximizes the depth of the slots in this area and thus reduces noise.

[0018] In at least one embodiment, the leading edge may, in particular, have a negative sweep angle on a proximal portion adjacent to the blade root and a positive sweep angle on a distal portion adjacent to the blade tip. One of the leading-edge slots may then be located in a leading-edge sulcus between said proximal and distal portions, where noise generation could be more pronounced due to the substantially zero sweep angle, in order to more effectively reduce noise emissions.

[0019] A second aspect of this presentation concerns an unfaired propulsive fan, comprising a first row of blades arranged to rotate around a central axis and a second row of blades, located downstream of the first row and including the turbomachine blade described in the first aspect. Indeed, leading-edge slots are particularly effective in reducing the noise emissions of unfaired propulsive fans, especially those due to the interaction of downstream blades with the wake of upstream blades and / or with the boundary layer adjacent to the fan hub.

[0020] The boundary layer around the blades of the first row can become particularly thick, and the wake of these blades can therefore be particularly energetic, at the location of their maximum local chord. Consequently, in at least one embodiment, a slot in the plurality of leading-edge slots of the blade of the second row of blades can be arranged at a radial distance from the central axis substantially identical to a radial distance, relative to the central axis, a maximum local chord profile of at least one blade from the first row of blades is used to more effectively restrict interaction noise with this wake. "Virtually identical" in this discussion means a value that is identical to within ±5%, or even ±2%.

[0021] To reduce noise emissions from unfaired propulsion fans, it is already known to use sawtooth trailing edges in rotating blades. However, in this case, their wake can be particularly energetic at the gaps between adjacent teeth. Consequently, in at least one embodiment, at least one slot from the plurality of leading-edge slots of the second-row blade, or even any slot from the plurality of leading-edge slots of the second-row blade, can be arranged at a radial distance from the central axis substantially equal to the radial distance, relative to the central axis, from a gap between adjacent teeth in a sawtooth trailing edge of at least one blade of the first-row blade, so as to more effectively restrict noise emissions caused by interaction with these wakes.

[0022] The lessons learned from this presentation are applicable to both unfaired propulsion fans of the "USF" type and those of the "CROR" type. Consequently, the second row of blades can, in particular, be counter-rotating with respect to the first row of blades, or stator-like.

[0023] A third aspect of this presentation concerns a propulsion system comprising the propulsive blower of the second aspect and a gas turbine engine for actuation of the propulsive blower.

[0024] A fourth aspect of this presentation concerns an aircraft comprising the propulsion system of the third aspect.

[0025] Individual characteristics of the various aspects and embodiments mentioned above can be combined in additional embodiments. Brief description of the drawings

[0026] The invention will be better understood and its advantages will become clearer upon reading the following detailed description of embodiments shown by way of non-limiting examples. The description refers to the accompanying schematic drawings, which are primarily intended to illustrate the principles presented.

[0027] In these drawings, identical or equivalent elements (or parts of elements) are identified by the same reference symbols from one figure to the next. In these attached drawings:

[0028] [Fig. 1] Fig. 1 schematically illustrates an aircraft.

[0029] [Fig. 2] Fig. 2 schematically illustrates a propulsion system, suitable for the propulsion of the aircraft in Fig. 1, equipped with a propulsive blower according to a first embodiment.

[0030] [Fig. 3A] Fig. 3A is a side view of a downstream blade of the propulsive blower of Fig. 2.

[0031] [Fig. 3B] Fig. 3B is a cross-sectional view of the blade of Fig. 3A in the IIIB-IIIB plane.

[0032] [Fig. 4A] Fig. 4A is a graph schematically illustrating a local chord distribution over the span of the blade in Fig. 3A.

[0033] [Fig. 4B] Fig. 4B is a graph schematically illustrating a maximum profile thickness distribution over the span of the blade in Fig. 3A.

[0034] [Fig. 5] Fig. 5 is a schematic perspective view of a leading edge slot of the blade in Fig. 3A.

[0035] [Fig. 6] Fig. 6 is a schematic side view of a propulsive blower according to a second embodiment.

[0036] [Fig. 7] Fig. 7 is a schematic side view of a propulsive blower according to a third embodiment. Description of the implementation methods

[0037] To make the explanation more concrete, embodiments are described in detail below, with reference to the attached drawings. It should be noted, however, that the invention is not limited to these embodiments.

[0038] As illustrated in Figure 1, an aircraft 1 can incorporate one or more propeller 10s with a propulsive fan 100 as described herein. These propellers 10 can, in particular, be arranged, as illustrated, under the wings 2, but other alternative arrangements, for example at the rear of the fuselage of the aircraft 1, are also conceivable.

[0039] As illustrated in Figure 2, the propulsion unit 10 can also include a gas turbine engine 11 and a reduction gear 12. In the direction of airflow, this gas turbine engine 11 can include a low-pressure compressor 13, a high-pressure compressor 14, a combustion chamber 15, a high-pressure turbine 16, a low-pressure turbine 17, and a nozzle 18, surrounded by a shroud 19 leading into the nozzle 18. The high-pressure turbine 16 can be connected to the high-pressure compressor 14 by a first rotating shaft 21 for driving the latter, while the low-pressure turbine 17 can be connected to the low-pressure compressor 13 by a second rotating shaft 22 coaxial with the first rotating shaft 21, in a similar manner. The reduction gear 12 can connect the second rotating shaft 22 to the propulsion fan 100 for actuation of the latter.Although in the illustrated example the propulsive blower 100 is positioned at the front of the thruster 10, in a so-called "puller" configuration, it is also possible to position it at the rear of the thruster, in a "pusher" configuration.

[0040] In addition to or as a replacement for the gas turbine engine 11, the thruster 10 could, however, include another type of engine, and in particular another type of combustion engine and / or an electric motor, for the actuation of the blower, directly and / or through a transmission such as the reducer 12. The thruster 10 could therefore thus be a hybrid thruster, in series or parallel, or even purely electric.

[0041] The propulsion fan 100 may comprise a rotor with a first row of blades 110, each constituting a rotor blade, and a stator with a second row of blades 120, downstream of the row of blades 110, each blade 120 thus constituting a guide blade. Alternatively, however, the propulsion fan 100 may comprise, instead of the stator, a second rotor, counter-rotating with respect to the first rotor, such that the blades 120 of the second row also each constitute a rotor blade. arranged downstream of the row of blades 110 of the first rotor. The two rows can in particular be coaxial, with the blades of the two rows 110, 120 arranged radially around the same central axis X, but it is also conceivable that they have different central axes, and in particular parallel ones.

[0042] Each of the blades 110, 120 can include a profiled body extending radially, with respect to the central axis X, from an inner diameter to an outer diameter of the corresponding row, as illustrated in Figs. 2 and 3A. The inner diameters Di and / or outer diameter De of the second row can also be different from those of the first row.

[0043] The streamlined body of each blade 110, 120 can be formed by stacked airfoils along a radial stacking axis in a corresponding span direction Z, so as to form, as illustrated in Fig. 3B, an intrados 121 and an extrados 122, each extending from a leading edge BA to a trailing edge BF and from a blade root 123 to a blade tip 124. For example, for a cross-section or airfoil of the blade 120, the leading edge BA can be defined as the upstream end along the fluid flow direction. The leading edge BA can be characterized by a local minimum on the radius of curvature defining the airfoil in its upstream portion. The trailing edge BF can be defined as the downstream end along the fluid flow direction. These cross-sections or airfoils can, in particular, be cambered.Each of the stacked profiles has a local chord c which is defined as the distance between the leading edge BA and the trailing edge BF on a straight line connecting them and having a pitch angle y with respect to a plane perpendicular to the central axis X, as well as a variable thickness between the lower surface 121 and the upper surface 123, perpendicular to a median line LS between the two (also known as the skeleton line or mean camber line), with a maximum value emax for each profile.

[0044] Conventionally, the angle of incidence y of an aerodynamic profile corresponds to the angle formed between, on the one hand, a first axis 150 which is defined by the intersection between the plane of the aerodynamic profile at the radial distance r and a plane T perpendicular to the central axis X, and on the other hand, a straight line connecting the leading edge BA and the trailing edge BF in the plane of the aerodynamic profile. The y-angle is measured on the upstream side of the plane T perpendicular to the central axis X. The y-angle is measured positively in a direction from the first axis 150 to the straight line connecting the leading edge BA and the trailing edge BF, and more particularly in a direction from the intrados 121 to the extrados 122.

[0045] As illustrated in Figs. 2 and 3A, the inner diameter Di and outer diameter De of the blade row 120 correspond, respectively, to the radial positions of the blade roots and tips 123 and 124. The local chord c and / or the maximum thickness emax of the profiles can decrease monotonically towards the blade tip 124 by less than 25%, or even 35%, of the span H of the blade tip 124 in the span direction Z, as illustrated in the graphs of Figs. 4A and 4B. It is even conceivable, as illustrated in Fig. 4B, that the maximum thickness emax decreases monotonically over the entire span H from the blade root 123 to the blade tip 124.

[0046] In the context of this invention, the leading edge sweep angle α of the leading edge BA is defined as the angle of a straight line tangent to the leading edge BA with the transverse plane T. The sweep angle α is measured relative to the transverse plane T in the flow direction. Thus, a positive sweep angle corresponds to a downslope pitch, and a negative sweep angle corresponds to an upslope pitch. When the blade 120 has a variable pitch, the leading edge sweep angle α of the leading edge BA can be measured with the blade 120 positioned at any pitch angle that allows the usual direction of airflow through the fan. For example, when the pitch angle α is equal to 80° for an airfoil profile of the blade 120 located at a radial position corresponding to approximately 75% of the outer radius D e / 2, which can be representative of the blade pitch angle 120 in cruise. As illustrated in Fig. 3A, the leading edge BA can notably exhibit a negative sweep angle α on a proximal part BA P , adjacent to the blade root 123 and a positive sweep angle α on a distal portion BAd, adjacent to the blade tip 124. In particular, the sweep angle α could be greater than or equal to 40°, or even 45°, or even 50° over the entire leading edge segment within 5% of the span H of the blade tip 124 along the span direction Z. The transition between the proximal portion BA P and the distal part BAd can be formed by a belly BA V where the angle of deflection a is close to zero.

[0047] One or more of the blades 120, or even all of the blades 120 in the second row, may each have several leading-edge slots 200. As illustrated in Fig. 5, each of the leading-edge slots 200 may be delimited by two lateral slot surfaces 210. As illustrated in particular in Fig. 3A, the slots 200 may be distributed on the leading edge BA of the blade 120 such that a radial distance An, along the span direction Z, from the blade root 123 to at least the slot 200 closest to the blade root 123 among said plurality of slots 200 is less than a radial distance Ar e , along the span direction Z, from the blade head 124 to the slot 200 closest to the blade head 124 among said plurality of slots 200. In particular, the leading edge BA may be devoid of any slot 200 at a radial distance Ar eCompared to the blade tip 124, in the span direction Z, the span is less than 25%, or even 35%, of the span H. This optimizes the acoustic performance of the blade 120 with 200 slots at the leading edge. Indeed, this allows for slots close to the blade root 123, thus limiting interaction with the hub boundary layer in a region with a low and negative sweep angle. This also avoids the presence of 200 slots at the leading edge near the blade tip 124, where the sweep angle is high and positive, and the airfoil profiles have a reduced chord, incompatible with a 200 slot depth sufficient to provide significant acoustic gains.

[0048] In at least one embodiment, the blade can have a comparatively low activity factor, for example between 35 and 230, or even between 85 and 165. For the purposes of this discussion, "activity factor" means a parameter defined by the equation: 100,000 r 1 c(£) where FA represents the activity factor, represents a radial distance r from the central axis X, divided by half the outside diameter De, and c(f) represents the local chord between the leading and trailing edges of the airfoil at said radial distance r. A relatively low activity factor FA therefore implies a relatively large local chord c near the foot of blade 123, which can facilitate flow straightening, with a consequent aerodynamic advantage, while also facilitating the integration of deeper 200 slots in this area.

[0049] As also illustrated in Fig. 3A, one 200 slot of the plurality of 200 leading-edge slots can be located in the belly BA V of the leading edge BA between said proximal parts BA Pand distal BAd, where noise generation could be more pronounced due to the near-zero sweep angle, in order to more effectively reduce noise emissions. In particular, the radial distance r of this slot 200 from the central X axis can differ by less than 5%, or even by less than 2%, from the radial distance r from the central X axis of a zero sweep angle position of the leading edge BA.

[0050] Alternatively or in addition to this, in an embodiment illustrated in Fig. 6, a slot 200 of the plurality of leading-edge slots 200 of the blade 120 can be disposed at a radial distance r from the central axis X substantially identical to a radial distance r C max, with respect to the central axis X, of a profile Pcmax of maximum local chord Cmax of at least one blade 110 of the first row of blades 110.

[0051] However, it is also conceivable that at least one blade 110 of the first row of blades 110 has a sawtooth trailing edge BF' (in English: "serrations"), which may, for example, have a sinusoidal shape. In this case, at least one slot 200, or even each slot 200 of the plurality of leading-edge slots 200 of the blade 120 of the second row of blades 120, can be arranged at a radial distance r from the central axis X substantially identical to a radial distance rbfc, with respect to the central axis X, of a groove 111 between adjacent teeth in the sawtooth trailing edge BF' of at least one blade 110 of the first row of blades 110, as in the embodiment illustrated in Fig. 7.

[0052] Although the present invention has been described with reference to specific embodiments, it is evident that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, The individual characteristics of the various embodiments mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Demands

1. A turbomachine blade (120) comprising an intrados (121) and an extrados (122) extending, in a span direction (Z), over a span (H) from a blade root (123) to a blade tip (124) and, perpendicular to the span direction, from a leading edge (BA) to a trailing edge (BF), defined by a stack of profiles in the span direction (Z) where in each profile the leading edge is separated from the trailing edge by a local chord (c) along a local chord direction (CL) perpendicular to the span direction (Z), and having a plurality of leading-edge slots (200) each delimited by two lateral slot surfaces (210), characterized in that a radial distance (An), along the span direction (Z), from the blade root (123) to at least one slot (200) among said plurality of slits (200) is less than a radial distance (Ar e), along the span direction (Z), from the blade head (124) to any slot (200) among said plurality of slots (200).

2. Turbomachine blade (120) according to claim 1, wherein the leading edge (BA) is devoid of slots (200) at less than 25%, or even 35%, of the span (H) of the blade head (124) in the span direction (Z).

3. Turbomachine blade (120) according to any one of claims 1 or 2, wherein the local chord (c) and / or a maximum thickness (e ma x) profiles decrease in a strictly monotonic way towards the blade head (124) to less than 25%, or even 35%, of the span (H) of the blade head (124) in the span direction (Z).

4. Turbomachine blade (120) according to claim 3, wherein the maximum thickness (e max) profiles decrease in a strictly monotonic way over the entire span (H) from the blade foot (123) to the blade head (124).

5. Turbomachine blade (120) according to any one of claims 1 to 4, wherein no leading edge (BA) sweep angle (a) within 5% of the span (H) of the blade head (124) along the span direction (Z) is less than 40°, or even 45°, or even 50°.

6. Turbomachine blade (120) according to any one of claims 1 to 5, with an activity factor between 35 and 230, or even between 85 and 165.

7. Turbomachine blade (120) according to any one of claims 1 to 6, wherein the leading edge (BA) has a negative sweep angle (a) on a proximal portion (BA P), adjacent to the vane foot (123) and a positive sweep angle (a) on a distal portion (BAd), adjacent to the vane head, and a slot (200) of the plurality of leading edge slots (200) is located in a belly (BA V ) of the leading edge (BA) between said proximal parts (BA P ) and distal (BAd).

8. Unshod propulsion blower (100) comprising a first row of blades (110) arranged to rotate about a central axis (X) and a second row of blades (120), located downstream of the first row of blades (110) and comprising the turbomachine blade (120) according to any one of claims 1 to 7.

9. An unfaired propulsive blower (100) according to claim 8, wherein a slot (200) of the plurality of leading-edge slots (200) of the blade (120) of the second row of blades (120) is disposed at a radial distance from the central axis (X) substantially identical to a radial distance (r cm ax), with respect to the central axis (X), of a profile (Pcmax) of maximum local chord (c ma x) of at least one blade (110) of the first row of blades (110).

10. An unfaired propulsive blower (100) according to any one of the features 8 or 9, in which at least one slot (200) of the plurality of leading-edge slots (200) of the blade (120) of the second row of blades (120) is disposed at a radial distance from the central axis (X) substantially equal to a radial distance (rbft), with respect to the central axis (X), of a hollow (111) between adjacent teeth in a sawtooth trailing edge (BF') of at least one blade (110) of the first row of blades (110).

11. Unfaired propulsive blower (100) according to claim 10, wherein any slot (200) of the plurality of leading edge slots (200) of the blade (120) of the second row of blades (120) is disposed at a radial distance from the central axis (X) substantially identical to a radial distance (rbfc), relative to the central axis (X), of a hollow (111) between adjacent teeth in a sawtooth trailing edge (BF') of at least one blade (110) of the first row of blades (110).

12. Unfaired propulsive blower (100) according to any one of the features 8 to 11, in which the second row of blades (120) is contra-rotating with respect to the first row of blades (HO).

13. Unshod propulsive blower (100) according to any one of the features 8 to 11, in which the second row of blades (120) is stator.

14. Propeller (10) comprising the propulsion blower (100) according to any one of claims 8 to 13 and a gas turbine engine (11) for actuation of the propulsion blower.

15. Aircraft (1) comprising the propulsion unit (10) of claim 14.

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