Turbomachine blade with leading edge slots

Abstract

Turbomachine blade with leading edge slots. Turbomachine blade (120), in particular of an unfaired propulsion fan, having a plurality of slots (200). A radial distance (Δri), along the span direction (Z), from the blade root (123) to at least one slot (200) among said plurality of slots (200) is less than a radial distance (Δre), along the span direction (Z), from the blade tip (124) to any slot (200) among said plurality of slots (200). Figure for the abstract: Fig. 3A.

Description

Title of the invention: Turbomachine blade with leading edge slots. Technical field

[0001] The technical field of the present exposition 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 various states. 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 aeronautical components and products that are less energy-intensive, more environmentally friendly, and 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 lightening of aircraft, in particular 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 the efficiency of all systems of propulsion, and more specifically propulsive efficiency which characterizes the effectiveness with which the energy used is converted into useful thrust effort.

[0007] The elements influencing this propulsive efficiency to the first order are those that contribute directly to thrust generation, including, in particular, the propulsive fans. The known guiding principle for improving propulsive efficiency consists of reducing the fan's compression ratio, thereby decreasing the airflow velocity at the fan outlet and the associated kinetic energy losses.

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

[0009] To allow for a greater dilution ratio, several types of unducted propulsion fans have been considered, including those known by the English acronyms "USF" and "CROR". In both types, the propulsion 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 with respect to the usual direction of airflow through the fan. However, in "USF" ("Unducted Single Fan") propulsion fans, only the upstream row rotates around the central axis, whereas in "CROR" ("Counter-Rotating Open Rotor") propulsion fans, both rows rotate in opposite directions. However, in both types, blades in each of the two rows may 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 contained 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] The present description is the result of technological research aimed at significantly improving aircraft performance and, in this respect, contributes to reducing their environmental impact, particularly in terms of noise emissions. To this end, a first aspect of this description 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 profiles perpendicular to the span direction where, in each profile, the leading edge is separated from the trailing edge by a local chord along a local chord direction perpendicular to the span direction, and has 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 near the blade tip, where the chord and / or thickness of the blade can decrease, while the sweep can typically be more pronounced.

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

[0015] In at least one embodiment, the maximum thickness of the profiles can even decrease in a strictly monotonic manner over 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 limit 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 even 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 belly 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 the present disclosure concerns an unshod propulsion fan, comprising a first row of blades arranged to rotate about a central axis and a second row of blades, located downstream of the first row of blades and comprising the turbomachine blade according to the first aspect. Indeed, leading-edge slots are particularly effective in reducing the noise emissions of unshod propulsion fans, and in particular 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, with respect to the central axis, from a maximum local chord profile of at least one blade of the first row of blades, in order to more effectively restrict the interaction noise with this wake. By "substantially identical", in the context of this presentation, we mean a value that is identical to within ±5%, or even ±2%.

[0021] In order to reduce the noise emissions of 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 of the plurality of leading-edge slots of the blade in the second row of blades, or even any slot of the plurality of leading-edge slots of the blade in 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, from a gap between adjacent teeth in a sawtooth trailing edge of at least one blade in the first row of blades, so as to more effectively restrict the noise emissions caused by interaction with these wakes.

[0022] The principles of 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-shaped.

[0023] A third aspect of the present exposition relates to a propulsion unit comprising the propulsion blower of the second aspect and a gas turbine engine for actuation of the propulsion blower.

[0024] A fourth aspect of the present exposition relates to an aircraft comprising the propulsion system of the third aspect.

[0025] Individual features 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 drawings, which are schematic and intended primarily to illustrate the principles presented.

[0027] In these drawings, from one figure to another, identical or equivalent elements (or parts of elements) are identified by the same reference numerals. 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 of [Fig.1], equipped with a propulsive blower according to a first embodiment.

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

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

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

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

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

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

[0036] [Fig.7] The [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 accompanying drawings. It should be noted, however, that the invention is not limited to these embodiments.

[0038] As illustrated in [Fig. 1], an aircraft 1 can incorporate one or more propellers 10 with a propulsive fan 100 according to the present description. 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 [Fig. 2], the propulsion unit 10 may also include a gas turbine engine 11 and a reduction gear 12. In the direction of airflow, this gas turbine engine 11 may 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 may be connected to the high-pressure compressor 14 by a first rotating shaft 21 for driving the latter, while the low-pressure turbine 17 may 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 may 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 propeller 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 propeller 10 could therefore thus be a hybrid propeller, 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 may, 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 may have different central axes, and in particular parallel ones.

[0042] Each of the blades 110, 120 may 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 may 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 intrados 121 and the extrados 123, perpendicular to a median line. LS between the two (also known as skeleton line or mean camber line), with a maximum value emax for each profile.

[0044] Conventionally, the angle of incidence y of an airfoil corresponds to the angle formed between, on the one hand, a first axis 150, which is defined by the intersection of the airfoil plane at a 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 airfoil plane. The angle of incidence y is measured on the upstream side of the plane T perpendicular to the central axis X. The angle of incidence y 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 lower surface 121 to the upper surface 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, 124. The local chord c and / or the maximum thickness emax of the profiles can decrease in a strictly monotonic manner towards the blade tip 124 to 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 in a strictly monotonic manner over the entire span H from the blade root 123 towards the blade tip 124.

[0046] In the context of the present 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, with respect 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 De / 2, which can be representative of the pitch angle of the blades 120 in cruise. As illustrated in the [Fig.3A], the leading edge BA may in particular have a negative sweep angle a on a proximal part BAP, adjacent to the blade foot 123 and a positive sweep angle a on a distal part BAd, adjacent to the blade head 124. In particular, the sweep angle a could be greater than or equal to 40°, or even 45°, or even 50° over the entire segment of the leading edge within 5% of the span H of the blade head 124 according to the . Z-span direction. The transition between the proximal part BAP and the distal part BAd can be formed by a BAV antinode where the slant angle a is close to zero.

[0047] One or more of the blades 120, or even all of the blades 120 of 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 Ar, 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 Are, along the span direction Z, from the blade tip 124 to the slot 200 closest to the blade tip 124 among said plurality of slots 200.In particular, the leading edge BA can be devoid of any slots 200 at a radial distance Are from the blade tip 124, in the span direction Z, less than 25%, or even 35%, of the span H. This optimizes the acoustic performance of the blade 120 with slots 200 at the leading edge. Indeed, this allows for slots close to the blade root 123 and thus limits interaction with the hub boundary layer in a region with a low and negative sweep angle, while avoiding the presence of slots 200 at the leading edge near the blade tip 124, where the sweep angle is high and positive and the airfoils present have a reduced chord incompatible with a slot depth 200 sufficient to provide significant acoustic gains.

[0048] In at least one embodiment, the blade may 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 according to the equation: 100,000 f1. where FA represents the activity factor, ç represents a radial distance r relative to 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 profiled body at said radial distance r. A relatively low activity factor FA therefore implies a relatively large local chord c near the blade root 123, which can facilitate flow straightening, with a consequent aerodynamic advantage, while also facilitating the integration of deeper slots 200 in this area.

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

[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 rcmax, 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 may have 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, may be disposed at a radial distance r from the central axis X substantially identical to a radial distance rbf c>i, 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, individual features 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 (Aq), along the span direction (Z), from the blade root (123) to at least one slot (200) among said plurality of slots (200) is less than a radial distance (Are), along the span direction (Z),from the dawn 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 (emax) of the profiles decreases in a strictly monotonic manner 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 (emax) of the profiles decreases in a strictly monotonic manner 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 part (BAP), adjacent to the blade foot (123) and a positive sweep angle (a) on a distal part (BAd), adjacent to the blade head, and a slot (200) of the plurality of leading edge slots (200) is located in a belly (BAV) of the leading edge (BA) between said proximal (BAP) and distal (BAd) parts.

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. 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 (rcmax), relative to the central axis (X), of a maximum local chord (cmax) profile (Pcmax) of at least one blade (110) of the first row of blades (110).

10. 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 identical to a radial distance (rbf cj), with respect to the central axis (X), of a groove (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 (rbf Cji), with respect to the central axis (X), of a hollow (111) between adjacent teeth in a trailing edge (BF') sawtooth pattern 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 (110).

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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