Fan for aeronautical propulsion

Abstract

The invention relates to a propulsive fan (100) comprising at least a first row of blades (110) that are able to rotate about a central axis (X). Each of the blades (110) of the first row comprises a profiled body extending radially from an inner radius Ri to an outer radius Re in relation to the central axis (X) and comprising a pressure side (111) and a suction side (112) connecting a leading edge (BA) to a trailing edge (BF). The trailing edge (BF) of the profiled body of each blade (110) of the first row of blades (110) has sawteeth and the profiled body of each blade (110) of the first row of blades (110) has an activity factor FA between 225 and 300.

Description

Description Title of the invention: Fan for aeronautical propulsion Technical Field

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

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those already in operation, requiring the implementation of technological solutions to ensure their compliance with current regulations. Civil aviation has been mobilizing 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 consideration the impact factors in all phases of design and development to obtain less energy-intensive, 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 and minimizing 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 ensure propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

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

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

[0008] To achieve the same thrust, this reduction in flow velocity at the outlet of the propulsive fan must normally be compensated 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 normally also implies a greater bypass ratio (BPR), which is the ratio between the mass flow rate of the cold fan flow (secondary flow) and that feeding the combustion chamber of the gas turbine engine (primary flow).

[0009] When the fan is shrouded, the increase in the fan diameter also implies an increase in the external dimensions of the retention casing surrounding it, as well as of the nacelle constituting the aerodynamic envelope of the casing in question, and therefore its drag, as well as that of their mass. In order to avoid these disadvantages, it is possible to shorten the axial length of the nacelle and to thin it, which reduces the space available for acoustic treatments which serve to reduce noise.

[0010] Furthermore, the interactions between successive rows of blades and vanes can aggravate these noise emissions, in particular at the harmonics of the blade passing frequency (BPF). Significant research and development efforts have therefore been directed, in particular by the Applicant, towards reducing these noise emissions. To this end, it has been proposed, in particular in the publications of international patent applications WO 2023 / 007098 A1 and WO 2019 / 158875 A1, to form teeth or undulations on the trailing edge of the blades of unducted propulsive fans, so as to reduce or distribute their marginal vortices. This solution has also been proposed for ducted fans, for example in the publications of French patent applications FR 2 986 285 A1 and FR 3 103 231 A1.Furthermore, it has also been proposed to incorporate teeth or undulations into the leading edge for similar reasons, for example in European patent application publication EP 2 760 737 A1 and in US patents 11,560,796 and US 11,047,238. Statement of the invention

[0011] This disclosure is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributing to reducing their environmental impact, particularly in terms of noise emissions. For this purpose, a first aspect of this disclosure relates to a propulsive fan, comprising at least one row of blades capable of rotating around a central axis, each of the blades in the row of blades comprising a profiled body extending radially from an inner radius R to an outer radius R erelative to the central axis and comprising a lower surface and an upper surface connecting a leading edge to a trailing edge. The profiled body of each blade of the row of blades has an activity factor FA between 225 and 300, preferably between 240 and 300, said activity factor FA being defined according to the equation: îoo ooo r 1 c(f) c , j r where represents a radial distance from the central axis, divided by the outer radius R e , and c(f) represents a local chord between the leading and trailing edges of the profiled body at said radial distance. Furthermore, the trailing edge of the profiled body of at least one blade of the row of blades has saw teeth.

[0012] The activity factor FA between 225 and 300, relatively high, is conducive to better propulsive efficiency, but implies that the chord is relatively large in the upper part of the blade, that is to say close to its external radius R e . Since the boundary layer thickness at the trailing edge normally increases with chord, such a relatively high FA activity factor is normally associated with an increase in the inherent, broadband fan noise and the characteristic width or scale of the blade wake vortices. The inventors have found, however, that the teeth at the trailing edge make it possible to limit noise emissions even with such a high FA activity factor, so as to combine high propulsive efficiency with moderate noise emissions.

[0013] The trailing edge may in particular have spacings between adjacent tooth apexes which decrease monotonically in the radial direction towards the outer radius R e . By "monotonic" decrease, in the context of this disclosure, it is meant that the spacing between the apexes of adjacent teeth located most radially to the outside is less than that between the apexes of adjacent teeth located most radially to the inside and that, from the spacing between the apexes of adjacent teeth located most radially to the inside to the spacing between the apexes of adjacent teeth located most radially to the outside, each spacing is equal to or less than the preceding adjacent spacing. However, it is alternatively envisaged that the spacings between apexes of adjacent teeth are increasing in the radial direction towards the outer radius R e .

[0014] Thus, it is conceivable that each spacing among said spacings between adjacent tooth apexes is different, that is to say that, from the spacing between the apexes of the adjacent teeth located most radially on the inside to the spacing between the apexes of the adjacent teeth located most radially on the outside, each spacing is less than the preceding adjacent spacing if the spacings between adjacent tooth apexes decrease towards the outer radius R e .

[0015] However, it is alternatively conceivable that at least two adjacent spacings, but preferably not more than five, or even three, among said spacings between adjacent tooth tips, preferably in an upper part of the blade, close to its outer radius, are substantially identical, in particular in order to simplify the production of the blades.

[0016] Each of the blades in the row of blades can have an elongation equal to the outer radius R e multiplied by a coefficient between 1, 2 rrr 1 and 2.6 rm 1 , preferably between 1 and 6 ITT 1 and 2.2 r 1 . Such an elongation, normalized by the outer radius R e of the blade, and therefore the diameter D of the row of blades, allows for good distribution of the aerodynamic load.

[0017] Although the spacings between adjacent tooth tips decrease monotonically from the inner radius R to the outer radius R e, it is conceivable that a ratio between a maximum spacing and a minimum spacing among said spacings between adjacent tooth apices is less than 15, preferably less than 8, and even more preferably less than 5, so as to limit the number of teeth and / or the number of different spacings and thus simplify the production of the blades. This ratio between the maximum spacing À max and the minimum spacing A min may also be greater than 1.25.

[0018] A maximum spacing among said spacings between adjacent tooth tips may be between 0.05 and 0.4 times the height of the profiled body of the blade, i.e., the difference between said outer radii R eand interior R,, preferably between 0.1 and 0.35 times said height, more preferably between 0.15 and 0.3 times said height. It is thus possible to obtain a maximum spacing which can be of the order of magnitude of the wavelength of the second harmonic r2 of the blade passage frequency ("BPF") during the take-off phase of the aircraft, which can be particularly important in terms of acoustic nuisance. This wavelength of the second harmonic of the BPF can be estimated according to the equation: 30c o r2 = “^“in which c0 represents the speed of sound (in m / s), B the number of blades and Q the rotational speed of the first row of blades (in revolutions per minute). In addition, a minimum spacing among said spacings between vertices of adjacent teeth is between 0.01 and 0.2 times a difference between said outer radii R eand interior Ri, preferably between 0.02 and 0.15 times the difference between said exterior radii R e and interior R,, still preferably between 0.04 and 0.12 times the difference between said exterior radii R e and interior Ri-

[0019] The trailing edge may be formed such that any ratio between adjacent spacings among said spacings between adjacent tooth tips is between 1 and 2, preferably between 1.03 and 1.5. In particular, each ratio between adjacent spacings may be approximately equal to one plus the inverse of a positive integer. By "approximately" is meant that it may be subject to a margin of error of ±30%, or preferably ±10%. This allows for decreasing adjacent spacings depending on the wavelength of the blade passing frequency ("BPF") or its harmonics.

[0020] The trailing edge may be configured such that each of the trailing edge teeth has a height between 0.1 and 2 times a spacing between the top of the same tooth and the top of an adjacent tooth, preferably between 0.2 and 1.6 times the spacing between the top of the same tooth and the top of the adjacent tooth, more preferably between 0.3 and 1.2 times the spacing between the top of the same tooth and the top of the adjacent tooth. The choice of this ratio makes it possible to better reduce noise emissions, while ensuring good mechanical strength.

[0021] Said trailing edge teeth may take the form of undulations, in particular sinusoidal, although other forms are also conceivable. The trailing edge may be configured such that each spacing between adjacent tooth apexes is equal to the square of the height of one of the adjacent teeth, multiplied by a coefficient between 0.005 mm' 1 and 1 mm' 1 , preferably between 0.01 mm'1 and 0.8 mm' 1 , still preferably between 0.02 mm' 1 and 0.6 mm' 1 , especially if the teeth are sinusoidal. Indeed, when the teeth are sinusoidal, the radius of curvature at the hollows between adjacent teeth is proportional to the ratio between the spacing and the square of the height. However, a radius of curvature that is too small at the hollows increases the mechanical constraints and makes the manufacture of the blade difficult, while a radius of Too large a curvature would be less effective in reducing noise emissions.

[0022] The propulsive fan may have pitch angles, at the radial positions of the tooth tips, which decrease monotonically in the radial direction towards the outer radius R e. In addition or alternatively to this, the radial position of each tooth tip may correspond substantially to a radial position of a local maximum or local minimum of pitch angle. "Substantially" may be understood in this context to mean that the radial positions of tooth tips and the radial positions of local maxima or minima of pitch angle correspond to within 5%, preferably within 2%, of the height of the profiled body of the blade.

[0023] Said trailing edge of the at least one blade of the row of blades may comprise at least one portion without teeth, and in particular two portions without teeth separated from each other in the radial direction.

[0024] For example, when an air inlet, in particular a gas turbine engine air inlet, is arranged downstream of the row of blades, and in particular of a lower part of the blades of the part of the blades, adjacent to their inner radius R,, it is conceivable that this part of the blades arranged upstream of the air inlet is devoid of teeth, thus preventing them from being able to enter the air inlet in the event of breakage of one or more teeth. Furthermore, it is also conceivable that a middle part of the blades, extending for example between the lower quarter and the upper quarter of the height of the blades, is devoid of teeth on the trailing edge, in order to reduce the mechanical stresses in this particularly stressed area.

[0025] As indicated previously, a row of outlet guide vanes or OGVs (from the English “Outlet Guide Vanes”) may be arranged downstream of the row of blades, in particular according to a configuration in which this row of guide vanes is not rotatable about the central axis. At least one blade of the row of blades and / or one guide vane of the row of guide vanes may be of variable pitch. A leading edge of at least one guide vane of the row of guide vanes may have a belly, and the trailing edge of at least one blade of the row of blades may then have at least one tip tooth at a radial distance from the central axis approximately equal to a radial distance of said belly from the central axis. By "approximately equal" can be understood, in this context, that the radial distance of the tooth tip is equal to that of the belly, ±20% (or even only ±10%) of the height of the blade of the first row.

[0026] The propulsive fan may in particular be a ducted propulsive fan, further comprising a nacelle surrounding at least the row of blades.

[0027] A second aspect of the present disclosure relates to a thruster that may comprise the propulsive fan according to the first aspect and a gas turbine engine for actuating the propulsive fan. The thruster may in particular also comprise a reduction gear interposed between the gas turbine engine and the propulsive fan, in order to reduce the rotational speed of the propulsive fan relative to an output speed of the gas turbine engine. However, other actuation means are also conceivable, such as for example a hybrid thruster in which the gas turbine engine would be combined with an electric motor, which could be interposed in series between the gas turbine engine and the fan, or be arranged in parallel with the gas turbine engine in a transmission line. An electric thruster, comprising only an electric motor for actuating the propulsive fan, is also conceivable.

[0028] A third aspect of the present disclosure relates to an aircraft comprising a propellant as described above. Brief description of the drawings

[0029] The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown as non-limiting examples. The description refers to the appended drawings which are schematic and aim above all to illustrate the principles of the disclosure.

[0030] In these drawings, from one figure to another, identical or equivalent elements (or parts of elements) are identified by the same reference signs. In these attached drawings:

[0031] [Fig. 1] Figure 1 schematically illustrates an aircraft.

[0032] [Fig. 2] Figure 2 schematically illustrates a propeller, suitable for propelling the aircraft of Figure 1, equipped with a ducted propulsive fan according to a first embodiment.

[0033] [Fig. 3A] Figure 3A shows a side view of a blade of the propulsive fan of the first embodiment.

[0034] [Fig. 3B] Figure 3B represents a sectional view of the blade of Figure 3A along plane BB.

[0035] [Fig. 3C] Figure 3C illustrates an evolution of the chord of the blade of Figure 3A as a function of the radial distance from the central axis of the propulsive fan.

[0036] [Fig. 3D] Figure 3D illustrates the evolution of the pitch angle of the blade of Figure 3A as a function of the radial distance from the central axis of the propulsive fan.

[0037] [Fig. 3E] Figure 3E illustrates an alternative shape of the trailing edge of the blade of Figure 3A.

[0038] [Fig. 4] Figure 4 represents a side view of a blade of a propulsive fan according to a second embodiment.

[0039] [Fig. 5] Figure 5 illustrates a propulsive fan according to a third embodiment.

[0040] [Fig. 6] Figure 6 illustrates a propulsive fan according to a fourth embodiment.

[0041] [Fig. 7] Figure 7 illustrates a propulsive fan according to a fifth embodiment. Description of the embodiments

[0042] In order to make the disclosure more concrete, embodiments are described in detail below, with reference to the accompanying drawings. It is recalled, however, that the invention is not limited to these embodiments.

[0043] As illustrated in FIG. 1, an aircraft 1 may incorporate one or more propellers 10 with a propulsive fan 100 according to the present description. These propellers 10 may 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.

[0044] As illustrated in Figure 2, the propellant 10 may also comprise a gas turbine engine 11 and a reduction gear 12. In the direction of air flow, this gas turbine engine 11 may comprise 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 fairing 19 terminating in the nozzle 18. The high-pressure turbine 16 may be connected to the high-pressure compressor 14 by a first rotary shaft 21 for driving the latter, while the low-pressure turbine 7 may be connected to the low-pressure compressor 3 by a second rotary shaft 22 coaxial with the first rotary shaft 21, in a similar manner. The reduction gear 12 may connect the second rotary shaft 22 to the propellant fan 100 for actuating the latter.

[0045] In addition to or replacing the gas turbine engine 11, the thruster 10 could however comprise another type of motor, and in particular an electric motor, for actuating the fan, directly and / or through a transmission such as the reducer 12. The thruster 10 could therefore be a hybrid thruster, in series or parallel, or even purely electric.

[0046] The propulsive fan 100 may comprise a row of blades 110 and a row of guide vanes 120, downstream of the row of blades 110. The two rows may in particular be coaxial, with the blades 110 and the guide vanes 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. The row of blades 110 may contain, for example, between 8 and 24 blades, in particular between 10 and 22. The row of guide vanes 120 may contain, for example, between 10 and 44 blades, in particular between 12 and 40. The blades 110 may be fewer in number than the blades 120 to comply with the rules of acoustic cut-off in the duct and therefore to minimize the noise emitted by the propulsive fan 100. For example, the number of guide vanes 120 may be greater than twice the number of blades 110.

[0047] The propulsive fan 100 may in particular be a ducted fan, also comprising a nacelle 130 surrounding at least the blades 110. This nacelle 130 may also comprise a retention casing 140 around the blades 110, with an abradable material to limit damage in the event of contact between the radially external end of the blades 110 and the casing, and / or acoustic treatments for noise reduction.

[0048] Each of the blades 110 and vanes 120 may comprise a profiled body extending radially, relative to a profiled body, from an inner radius to an outer radius of the corresponding row, as illustrated in Figures 2 and 3A. However, the inner radii R, and / or outer radii R e of the first row may be different from the inner radii R,' and / or outer radii R e ' from the second row.

[0049] The profiled body of each blade 110 and each vane 120 may be formed by aerodynamic profiles stacked along a corresponding radial stacking axis Z, Z', so as to form, as illustrated in FIG. 3B, a lower surface 111 and an upper surface 112, each extending from a leading edge BA to a trailing edge BF. For example, for a section or aerodynamic profile of the blade 110, the leading edge BA may be defined as the upstream end along the direction of flow of the fluid. The leading edge BA may be characterized by a local minimum on the radius of curvature defining the profile in its upstream portion. The trailing edge BF may be defined as the downstream end along the direction of flow of the fluid.The trailing edge BF may also be characterized by a local minimum on the radius of curvature defining the profile in its rear part when the trailing edge BF is rounded, although, to simplify the manufacturing process, the trailing edge BF may alternatively be truncated, as illustrated in Figure 3E. These airfoils or sections may in particular be cambered. Each of the stacked profiles has a 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. The chord c and the pitch angle y may be. variables depending on the radial distance r from the central axis X of the propulsive fan.

[0050] Conventionally, the pitch angle 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 perpendicular to the central axis X, and on the other hand, a straight line connecting the leading edge BA and the trailing edge BF of the aerodynamic profile at the radial distance r. The pitch angle y is measured on the upstream side of the plane perpendicular to the central axis X. The pitch angle y is measured positively in a direction going 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 coinciding with the direction going from the intrados line 111 to the extrados line 112.

[0051] As illustrated in Figure 3A, the inner radii R, and outer radii R eof a blade 110 can be measured on the trailing edge BF and correspond, respectively, to the minimum and maximum radial positions relative to the central axis X. When the blade 110 is of variable pitch, the radial distances can be measured with the blade 110 placed at any pitch angle allowing the usual direction of air circulation through the fan. For example when the pitch angle y is equal to 60° for a section of the blade 110 located approximately 75% of R e , which may be representative of the blade pitch angle 110 in cruise. Similarly, the inner radii R,' and outer radii R e' of a blade 120 can be measured on the leading edge BA' and correspond, respectively, to the minimum and maximum radial positions relative to the central axis X. When the blade 120 is of variable pitch, the radial distances can be measured with the blade 120 placed at any pitch angle allowing the usual direction of air circulation through the fan. For example when the pitch angle y' is equal to 80° for a section of the blade 120 located approximately 75% of R e '.

[0052] At least one of the two rows may have a strength less than, for example, 3.0 over the entire height H, H' of the respective blades 110, or vanes 120, or even less than 1.2 and greater than 0.5 at the outer radius R e , R e ' of the row. By "height" is meant, in the context of this presentation, the difference between the external radius R e , and the inner radius R,, R,' of the profiled body, and by “solidity”, the ratio between the chord c of each blade 110 or vane 120 of a row and the distance between two adjacent blades or vanes in the same row at the same radial distance r from the central axis X. Each of the blades 110 may have an elongation equal to the outer radius R e multiplied by a coefficient between 1, 2 r 1 and 2.6 rm 1 , preferably between 1 and 6 ITT 1 and 2.2 r 1 . In the context of this presentation, "elongation" means the ratio between the height H and the mean chord C of the blade. As for the mean chord C, it can be calculated from the distribution c(r) of the local chord c as a function of the radial distance, according to the equation:

[0053] The axial distance between the stacking axes Z, Z' of the two rows may be, for example, between 0.05 and 1.2, in particular between 0.36 and 0.6 times the outer radius R eof the first row of blades 110, and above all sufficient to prevent interference of the trailing edges BF of the blades 110 with the leading edges of the vanes 120. Each of the blades 110 and vanes 120 may be rotatable about a radial axis or pitch change axis, which may in particular be the corresponding stacking axis Z, Z', in order to adjust its pitch and therefore its incidence relative to the direction of air flow according to the flight phase. This pitch change axis may preferably be perpendicular to the central axis X, alternatively inclined relative to the central axis X.When the blades 110 and the vanes 120 are fixed-pitch, the axial distance between the trailing edge BF of the blades 110 and the leading edge BA' of the vanes 120 may be between 1 and 4 times the chord c of the blade 110 at the radial position 0.95*Re relative to the central axis X, preferably between 1.5 and 3 times the chord c of the blade at the radial position 0.95*Re relative to the central axis X.

[0054] As illustrated in Figure 2, the row of blades 110 may be able to rotate around the central axis X, and in particular be mechanically connected, for its rotational drive around the central axis X, to the gas turbine engine 11, possibly by means of a reducer 12. Furthermore, in order to take advantage of the increase in the dynamic pressure of the air downstream of this first row of blades 110, an air inlet 20 of the gas turbine engine 11 may in particular be arranged between the blades 110 and the vanes 120. This air inlet 20 can for example be annular, with a spout 23 separating the air inlet 20 from the fairing 19.

[0055] On the other hand, the blades 120 may be, as also illustrated in FIG. 2, non-rotating around the central axis X.

[0056] The trailing edge BF of the profiled body of each blade 110 of the may have a number N of teeth with tooth heights hj where j=1, 2,... N in increasing order in the radial direction from the inner radius Ri to the outer radius R e , and a number M of spacings À k between adjacent tooth apices, where k=1, 2,...M and M < N-1 in ascending order in the radial direction from the inner radius Ri to the outer radius R e. In the context of this presentation, "tooth apex" means a local maximum of the chord c in the radial direction and "tooth height" means the difference between the chord at the tooth apex and the chord at a trough, i.e. a local minimum of the chord, located between the apex of this tooth and that of the adjacent tooth. It should be noted that a tooth apex can be characterized by a zero derivative of c(r) and a negative second derivative of c(r), while a trough can be characterized by a zero derivative of c(r) and a positive second derivative of c(r).

[0057] Following the camber of the stacked profiles of the blade 110, the variations of the chord c may be accompanied by variations of the pitch angle y, as illustrated in Figure 3C and 3D, in order to optimize the aerodynamic operation of the blade 110. In particular, the pitch angle y may have a local maximum or a local minimum at the radial position q of each tooth tip, more or less up to, for example, 5%, preferably 2%, of the height H of the profiled body of the blade 110.

[0058] The ratio between a maximum spacing To max and a minimum spacing To min among said spacings To k for k=1, 2,...M between adjacent tooth apices can be less than 15, preferably less than 8, and even more preferably less than 5. This ratio between the maximum spacing À max and the minimum spacing A min may also be greater than 1.25. The maximum spacing A maxmay also be between 0.05 and 0.4 times the height H of the profiled body of the blade 110, preferably between 0.1 and 0.35 times said height, more preferably between 0.15 and 0.3 times said height.

[0059] Each of the teeth can have a height hj between 0.1 and 2 times a spacing À k between the top of the same tooth and the top of an adjacent tooth, preferably between 0.2 and 1.6 times the spacing A k between the top of the same tooth and the top of the adjacent tooth, preferably still between 0.3 and 1.2 times the spacing A k between the top of the same tooth and the top of the adjacent tooth.

[0060] As illustrated in Figures 2 and 3A, the teeth may take the form of undulations, and in particular substantially sinusoidal undulations, although other alternative shapes such as triangular teeth are also conceivable. The trailing edge may be configured such that each spacing A k between the tops of adjacent teeth can be equal to the square of the height of one of the adjacent teeth, multiplied by a coefficient between 0.005 mm' 1 and 1 mm' 1 , preferably between 0.01 mm' 1 and 0.8 mm' 1 , still preferably between 0.02 mm' 1 and 0.6 mm' 1 , especially if the teeth are sinusoidal. Thus, a compromise can be obtained, for the radius of curvature of the teeth, between aerodynamic efficiency and mechanical strength.

[0061] As also illustrated in Figures 2 and 3A, the succession of teeth can extend over the entire height H of the profiled body of the blade 110, from the inner radius Ri to the outer radius R e . In particular, the trailing edge BF may have a last hollow or tooth crest at a radial distance, relative to the outer radius R e, of less than 30%, or even 20%, of the height H, in particular to redirect the flow of the blade tip vortices radially outwards and thus avoid undesirable interactions with the blades 120 of the second row downstream. In addition, the trailing edge BF may have a first hollow or tooth crest at a radial distance, relative to the inner radius Ri, of less than 30%, or even 20%, of the height H, in particular to avoid or limit boundary layer separation near the root of the blade 110 which could also have an undesirable interaction with the blades 120 downstream or degrade the aerodynamic performance of the air inlet 20.

[0062] Furthermore, when the leading edge BA' of the blades 120 of the has a belly V at a radial distance r v of the central axis X, between the inner radius Ri' and the outer radius R e' of this second, the trailing edge BF of the blades 110 of the first row may have at least one tooth tip at a distance radial from the central axis X equal to the radial distance r v, more or less at most 20%, or even 10%, of the height H, in order to reduce the undesirable interactions between the wake of the blades 110 and the belly zone V of the blades 120. Indeed, at the belly zone V of the blades 120, the axial distance between the trailing edge BF of the blades 110 and the leading edge BA' of the blades 120 can be reduced, and the leading edge BA' of the blades 120 has a reduced or zero sweep angle, which can increase the interaction noise. From an aerodynamic point of view, the tips of the teeth make it possible to reduce the speed deficit locally in the wake of the blades 110, hence the advantage of placing a tip of a tooth of the trailing edge BF of the blades 110 at the radial position of the belly V of the leading edge BA' of the blades 120 to reduce the interaction noise. By "belly" of the leading edge of a blade or vane, we mean, in the context of this disclosure, the most advanced point of the leading edge in the upstream axial direction.

[0063] The spacings To k can vary, and in particular decrease monotonically in the radial direction towards the outer radius R e , in such a way that À! > À2^3 — ■ ■■ ÀM-I AM- Thus, any ratio between adjacent spacings A k and To k+1 may be between 1 and 2, preferably between 1.03 and 1.5. Furthermore, as illustrated in Figure 3D, the alignment angles y at the radial positions q of the vertices may also decrease monotonically in the radial direction towards the outer radius R e , such that v( r i ) > y(r2) > y(r3)... y(r N .-i) > y(r N ), in order to adapt them to a relative flow angle which decreases towards the outer radius R e due to the rotation of the blades. As shown in Figures 2 and 3A, all spacings can be different, so that A^2> A3... A M -i>A M. In particular, each ratio between adjacent spacings A k and To k+1 can be approximately equal to one plus the reciprocal of a positive integer.

[0064] Alternatively, it is nevertheless conceivable that some of the spacings are identical, while maintaining a monotonous decrease, or growth, over all of the spacings. Thus, according to a second embodiment illustrated in FIG. 4, at least two, for example two to five, in particular two, three or four spacings may be substantially identical. The identical spacings may in particular be located in an upper part BFh of the trailing edge BF of the blade 110, adjacent at the outer radius R e, and extending for example over the upper 45% or 20% of the height H of the profiled body of the blade 110. The other characteristics of the propulsive fan may however be identical or equivalent to those of the first embodiment and consequently receive the same references in figure 4 as in the previous figures.

[0065] Furthermore, although in the two previous embodiments the teeth extend over the entire height H of the profiled body of the blade 110, it is also conceivable that at least a portion of the trailing edge is devoid of teeth. Thus, according to a third embodiment illustrated in FIG. 5, a lower portion BFb of the trailing edge BF may also be devoid of teeth. This lower portion BFb of the trailing edge BF may in particular extend from the inner radius R, and up to a radial distance r which may be, for example, equal to or greater than the radial position R bof the nozzle 23 of an air inlet 20 arranged downstream of the blades 110, and this in particular in order to prevent that in the event of tooth fracture these could come to engulf themselves in the air inlet 20, which could degrade the operation of the propellant. The other characteristics of the propulsive fan can however remain identical to those of the previous embodiments, and consequently receive the same references in figure 5 as in the previous figures.

[0066] Alternatively, however, at least one toothless portion may be a central portion BFc of the trailing edge BF of the blade 110, extending neither to the inner radius Ri nor to the outer radius R e, as in the fourth and fifth embodiments respectively illustrated in figures 6 and 7. This central part BFc without teeth can in particular extend between two tooth tops, as in the fifth embodiment illustrated in figure 6, or alternatively between two hollows, as in the sixth embodiment illustrated in figure 7.

[0067] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes may 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 discussed may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. A ducted propulsive fan (100) comprising at least one row of blades (110) capable of rotating about a central axis (X) and a nacelle (130) surrounding at least the row of blades (110), each of the blades (110) comprising a profiled body extending radially from an inner radius R to an outer radius R e relative to the central axis (X) and comprising a lower surface (111) and an upper surface (112) connecting a leading edge (BA) to a trailing edge (BF), in which the profiled body of each blade (110) has an activity factor FA between 225 and 300, preferably between 240 and 300, said activity factor FA being defined according to the equation: _ îoo ooo r 1 c«)3 FA = Ï6 JR d ^where represents a radial distance from the central axis (X), divided by the outer radius R e, and c(f) represents a local chord between the leading (BA) and trailing (BF) edges of the profiled body at said radial distance, and in which the trailing edge (BF) of the profiled body of at least one blade (110) has saw teeth.

2. A propellant fan (100) according to claim 1, wherein the trailing edge (BF) has spacings (À k ) between adjacent tooth apexes which decrease monotonically in the radial direction towards the outer radius R e .

3. A propellant fan (100) according to claim 2, wherein each spacing (A k ) among said spacings (At k ) between adjacent tooth apexes is different.

4. A propellant fan (100) according to claim 2, wherein at least two adjacent spacings of said spacings (A k) between adjacent tooth tops are substantially identical.

5. A propellant fan (100) according to any one of claims 2 to 4, wherein a ratio of a maximum spacing to a minimum spacing among said spacings (A k ) between adjacent tooth apexes is less than 15, preferably less than 8, and more preferably less than 5 and greater than 1.

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6. A propellant fan (100) according to any one of claims 2 to 5, wherein a maximum spacing among said spacings (A k ) between adjacent tooth apexes is between 0.05 and 0.4 times a difference between said outer radii R e and interior R iz preferably between 0.1 and 0.35 times the difference between said outer radii R e and interior R iz still preferably between 0.15 and 0.3 times the difference between said outer radii R eand interior R,.

7. A propellant fan (100) according to any one of claims 2 to 6, wherein a minimum spacing among said spacings (A k ) between adjacent tooth apexes is between 0.01 and 0.2 times a difference between said outer radii R e and interior R iz preferably between 0.02 and 0.15 times the difference between said outer radii R e and interior R iz still preferably between 0.04 and 0.12 times the difference between said outer radii R e and interior R,.

8. A propellant fan (100) according to any preceding claim, wherein any ratio between adjacent ones of said spacings (A k ) between adjacent tooth apexes is between 1 and 2, preferably between 1.03 and 1.5

9. A propellant fan (100) according to any one of claims 2 to 8, having pitch angles (Yj), at the radial positions (q) of the apexes of the teeth, which decrease monotonically in the radial direction towards the outer radius R e .

10. A propulsive fan (100) according to any preceding claim, wherein each of the blades (110) has an aspect ratio equal to the outer radius R e multiplied by a coefficient between 1.2 nr 1 and 2.6 rrr 1 , preferably between 1.6 nr 1 and 2.2 rrr 1 .

11. A propellant fan (100) according to any preceding claim, wherein each of the trailing edge teeth (BF) has a height (hj) between 0.1 and 2 times a spacing (À k ) between the top of the same tooth and the top of an adjacent tooth, preferably between 0.2 and 1.6 times the spacing (Àk ) between the top of the same tooth and the top of the adjacent tooth, preferably still between 0.3 and 1.2 times the spacing (À k ) between the top of the same tooth and the top of the adjacent tooth.

12. A propulsive fan (100) according to any preceding claim, wherein the radial position (q) of each tooth tip substantially corresponds to a radial position of a local maximum or a local minimum of pitch angle.

13. A propellant fan (100) according to any preceding claim, wherein each spacing (A k ) between adjacent tooth tops is equal to the square of a tooth height (hj) of one of the adjacent teeth, multiplied by a coefficient between 0.005 mm 1 and 1 mm, preferably between 0.01 mm 4 and 0.8 mm 4 , still preferably between 0.02 mm 4 and 0.6 mm 4 .

14. A propulsive fan (100) according to any preceding claim, wherein said trailing edge (BF) of the at least one blade (110) comprises at least one toothless portion, in particular two toothless portions separated from each other in the radial direction.

15. A propulsive fan (100) according to any one of the preceding claims, comprising a row of guide vanes (120), non-rotating around the central axis (X), arranged downstream of the row of blades (110).

16. A propulsive fan (100) according to claim 15, wherein a leading edge (BA 7 ) of at least one blade (120) of the row of blades (120) has a belly (V) and the trailing edge (BF) of at least one blade (110) of the row of blades (110) has at least one tooth tip at a radial distance (q) from the central axis (X) approximately equal to a radial distance (r v ) of said belly (V) relative to the central axis (X).

17. Propellant (10) comprising the propulsive fan (100) according to any one of the preceding claims and a gas turbine engine (11) for driving the propulsive fan (100).

18. An aircraft (1) comprising the propellant of claim 17.

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