Optimized fan section of an aeronautical propulsion system

Abstract

A fan section in which the ratio of the product of the average axial chord of the blade by the axial chord at the blade root to the product of the square of a blade height (47) by the axial chord at the blade tip (21) is less than the difference between the product of a maximum speed by the value 2.047 x 10⁻³ s / rad and the value 1.3403 x 10⁻¹, and the stiffness of a lower portion (55) of the blade is greater than the stiffness of an upper portion (57), and / or the ratio of the axial chord at the blade root to the product of the square of the average axial chord by the blade height and by the axial chord at the blade tip is less than the difference between the product of a maximum speed by the value 2.757 x 10⁻¹ s / rad and the value 67.4, and the stiffness of an upstream portion of the blade is greater than Steepness of the downstream portion. Figure for the abbreviation: Fig. 6

Description

Title of the invention: Optimized fan section of an aeronautical propulsion system. FIELD OF THE INVENTION

[0001] The present application relates generally to the field of propulsion systems, and more particularly to aeronautical propulsion systems exhibiting a high, or even very high, dilution rate. STATE OF THE ART

[0002] An aeronautical propulsion system generally comprises, from upstream to downstream in the direction of gas flow, a blower section, a compressor section which may include a low pressure compressor and a high pressure compressor, a combustion chamber and a turbine section which may include a high pressure turbine and a low pressure turbine.

[0003] When the propulsion system is in operation, the high-pressure compressor is driven in rotation by the high-pressure turbine via a high-pressure shaft. The blower and, where applicable, the low-pressure compressor are driven in rotation by the low-pressure turbine via a low-pressure shaft.

[0004] 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.

[0005] 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.

[0006] Consequently, the Applicant is constantly working to reduce its negative climate impact through the use of methods and the operation of virtuous development and manufacturing processes that minimize greenhouse gas emissions. greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0007] 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.

[0008] One of the objectives of technological research is thus to improve the environmental performance of aircraft. This is why, in all phases of design and development, the relevant factors are taken into account 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.

[0009] Thus, in order to improve the propulsive efficiency of the propulsion system and reduce its specific fuel consumption as well as the noise emitted by the fan section, propulsion systems with a high bypass ratio (also known as the "bypass ratio," abbreviated as BPR) have been proposed. The bypass ratio is the ratio of the secondary airflow rate to the primary airflow rate. To achieve high bypass ratios, the fan section can be decoupled from the low-pressure turbine, thereby allowing their respective rotational speeds to be optimized independently. Generally, decoupling is achieved using a reduction mechanism placed between the upstream end of the low-pressure shaft and a rotor of the fan section.The fan section rotor is then driven by the low-pressure shaft via the reduction mechanism at a rotational speed lower than that of the low-pressure shaft. Improving the system's propulsive efficiency can also be achieved by optimizing the fan section size. Indeed, due to its large diameter (designed in particular to achieve high bypass ratios and low fan pressure ratios), the fan section represents a significant portion of the propulsion system in terms of mass and therefore specific fuel consumption. Simultaneously, the fan section generates a very large part of the propulsion system's thrust. Summary of the invention

[0010] One objective of this application is to optimize the blower cross-section of the propulsion system, in particular to reduce its mass. To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.

[0011] This objective is achieved within the framework of the present application by means of a fan section of an aeronautical propulsion system, the fan section comprising:

[0012] - an interior platform,

[0013] - a blower rotor comprising a blade, the blade comprising a blade and a blade root fixed to the fan rotor, the blade extending over a blade height radially outwards relative to an axis of the propulsion system from an internal radial limit (37) located at the interface of the inner platform to a blade tip,

[0014] the dawn comprising a leading edge and a trailing edge,

[0015] the blade comprising a composite material structure including a fibrous reinforcement obtained by three-dimensional weaving of weft and warp strands and a matrix in which the fibrous reinforcement is embedded,

[0016] dawn presenting:

[0017] a lower portion comprising the foot of the blade,

[0018] an upper portion comprising the dawn peak,

[0019] an upstream portion comprising the leading edge and

[0020] a downstream portion including the trailing edge,

[0021] dawn presenting: - an axial chord at the base of the blade extending along an axis of the fan from the leading edge to the trailing edge, - an axial chord at the apex of the blade extending along the axis from the leading edge to the trailing edge, and - an average axial chord equal to the average between the axial chord at the base of the blade and the axial chord at the tip of the blade,

[0022] in which the dawn presents: - a first axial chord parameter corresponding to a ratio of a product of the average axial chord by the axial chord at the blade root to a product of the square of the blade height by the axial chord at the blade tip, - a first speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor expressed in rad / s by the value 2.047x103 s / rad and the value 1.3403x10 ', - a second axial chord parameter corresponding to a ratio of the axial chord at the blade root to a product of the square of the average axial chord by the blade height and by the axial chord at the blade tip, and - a second speed parameter corresponding to a difference of a product of the maximum permissible speed of the blower rotor expressed in rad / s by the value 2.757x10 1 s / rad and the value 67.4,

[0023] the blower section being configured so that the blower rotor has a maximum permissible speed greater than or equal to 280 rad / s,

[0024] the dawn being configured so that

[0025] the first axial chord parameter is less than or equal to the first velocity parameter and a stiffness of the lower portion is greater than a stiffness of the upper portion, and / or

[0026] the second axial chord parameter is less than or equal to the second velocity parameter and a stiffness of the upstream portion is greater than a stiffness of the downstream portion.

[0027] Such a blower section is advantageously and optionally complemented by the following various features taken alone or in combination: - the blade has a third speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor expressed in rad / s by the value 1.41x103 s / rad and the value 9.52x10', a fourth speed parameter corresponding to a difference of a product of the maximum permissible speed of the blower rotor expressed in rad / s by the value 2.067x10 1 s / rad and the value 50.5, the blade being configured so that the first axial chord parameter is greater than or equal to the third speed parameter, and / or the second axial chord parameter is greater than the fourth speed parameter; - the first axial chord parameter is less than or equal to the first velocity parameter and the stiffness of the lower portion is greater than the stiffness of the upper portion, the fan section comprising an intermediate portion extending from the lower portion to the upper portion, the lower portion extending from the internal radial limit towards the blade tip to the intermediate portion over a height greater than or equal to 15% and less than or equal to 25% of the blade height, the intermediate portion extending over a height greater than or equal to 5% and less than or equal to 30% of the blade height, the weft strands comprising first weft strands and second weft strands, the lower portion comprising first weft strands and no second weft strands, the upper portion comprising second weft strands and no first weft strands,a stiffness of the first weft strands being greater than a stiffness of the second strands of , weft, a density of the first strands increasing progressively in the intermediate portion from the lower portion towards the upper portion, a density of the second strands increasing progressively in the intermediate portion from the upper portion towards the lower portion; the second axial chord parameter is less than or equal to the second velocity parameter and a stiffness of the upstream portion is greater than a stiffness of the downstream portion, the fan blade having at each blade height a direct chord extending from the leading edge to the trailing edge, the fan section comprising a central portion extending from the upstream portion to the downstream portion, the upstream portion extending from the leading edge to the trailing edge to the central portion over a length greater than or equal to 25% and less than or equal to 40% of the direct chord length, the central portion extending over a length greater than or equal to 5% and less than or equal to 10% of the direct chord length, the warp strands comprising first warp strands and second warp strands,the upstream portion comprising more first chain strands than second chain strands and the downstream portion comprising second chain strands and no first chain strands, a stiffness of the first chain strands being greater than the stiffness of the second chain strands, a density of first strands decreasing progressively in the central portion of the upstream portion towards the downstream portion, a density of second strands increasing progressively in the central portion of the upstream portion towards the downstream portion; , a diameter of the blower rotor is, when the blower is shrouded, greater than or equal to 177.8 cm and less than or equal to 304.8 cm, in particular greater than or equal to 213.36 cm and less than or equal to 266.7 cm and preferably greater than or equal to 215.9 cm and less than or equal to 266.7 cm, and, when the blower is unshrouded, greater than or equal to 203.2 cm and less than or equal to 469.9 cm, in particular greater than or equal to 254 cm and less than or equal to 469.9 cm, and preferably greater than or equal to 304.8 cm and less than or equal to 396.2 cm; the blade being the first blade of a plurality of blades included in the blower rotor, a number of the plurality of blades being greater than or equal to 16 and less than or equal to 22; the blower rotor includes a blower hub, each blade being pivotally mounted relative to the blower hub so as to present a variable pitch; - the fan blade has a direct chord at the blade tip extending from the leading edge to the trailing edge along the blade tip, the axial chord at the blade tip being a projection along the X-axis of the direct chord at the blade tip, the fan rotor having a strength greater than or equal to 0.9 and less than or equal to 1.3, preferably greater than or equal to 1.0 and less than or equal to 1.3, where the strength is equal to a ratio between the direct chord at the blade tip and an inter-blade pitch at the blade tip; and - the fan blade has a direct chord at the blade apex extending from the leading edge to the trailing edge along the blade apex, the axial chord at the blade apex being a projection along the X-axis of the direct chord at the blade apex, the fan rotor having a strength strictly less than 1.0, where the strength is equal to a ratio between the direct chord at the blade apex and an inter-blade pitch at the blade apex.

[0028] The presentation also relates to an aeronautical propulsion system comprising:

[0029] - a movable drive shaft rotating around an axis;

[0030] - a blower shaft;

[0031] - a blower section such as has been presented so far, the rotor of the blower being driven in rotation by the blower shaft; and

[0032] - a reduction mechanism coupling the drive shaft and the blower shaft in order to drive the blower shaft at a rotational speed lower than the rotational speed of the drive shaft

[0033] Such a system is advantageously and optionally complemented by the following features:

[0034] - the system is configured to provide a thrust between 80,068 N and 331 374 N, preferably between 88,964 N and 155,688 N;

[0035] - a dilution ratio of the propulsion system is greater than or equal to 10, when the If the fan section is ducted, the dilution ratio is preferably greater than or equal to 10 and less than or equal to 35, or greater than or equal to 10 and less than or equal to 18; and if the fan section is unducted, the dilution ratio is greater than or equal to 40 and less than or equal to 80; and

[0036] - the blower rotor has a hub-to-head ratio greater than or equal to 0.22 and less than or equal to 0.32.

[0037] The exposition further relates to a method for dimensioning a fan section of an aeronautical propulsion system, the fan section comprising:

[0038] - an internal platform,

[0039] - a blower rotor comprising a blade including a blade and a blade root attached to the blower rotor, the blade extending over a blade height radially towards the exterior relative to an axis of the propulsion system from an internal radial limit located at the interface of the inner platform to a blade tip,

[0040] the dawn comprising a leading edge and a trailing edge,

[0041] the blade comprising a composite material structure including a fibrous reinforcement obtained by three-dimensional weaving of weft and warp strands and a matrix in which the fibrous reinforcement is embedded,

[0042] dawn presenting:

[0043] a lower portion comprising the foot of the blade,

[0044] an upper portion comprising the dawn peak,

[0045] an upstream portion comprising the leading edge and

[0046] a downstream portion including the trailing edge,

[0047] dawn presenting: - an axial chord at the base of the blade extending along an axis of the fan from the leading edge to the trailing edge, - an axial chord at the apex of the blade extending along the axis from the leading edge to the trailing edge, and - an average axial chord equal to the average between the axial chord at the base of the blade and the axial chord at the tip of the blade,

[0048] in which the dawn presents: - a first axial chord parameter corresponding to a ratio of a product of the average axial chord by the axial chord at the blade root to a product of the square of the blade height by the axial chord at the blade tip, - a first speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor expressed in rad / s by the value 2.047x103 s / rad and the value 1.3403x10 ', - a second axial chord parameter corresponding to a ratio of the axial chord at the blade root to a product of the square of the average axial chord by the blade height and by the axial chord at the blade tip, and - a second speed parameter corresponding to a difference between a product of the maximum permissible speed of the blower rotor expressed in rad / s by the value 2.757x10 1 s / rad and the value 67.414,

[0049] the blower section being configured so that the blower rotor has a maximum permissible speed greater than or equal to 280 rad / s,

[0050] the method comprising a step of dimensioning the blower cross-section such that

[0051] the first axial chord parameter is less than or equal to the first velocity parameter and a stiffness of the lower portion is greater than a stiffness of the upper portion, and / or

[0052] the second axial chord parameter is less than or equal to the second velocity parameter and a stiffness of the upstream portion is greater than a stiffness of the downstream portion.

[0053] The presentation finally relates to a manufacturing process for a fan section of an aeronautical propulsion system, including the dimensioning of the fan section as presented so far and the manufacturing of the section. PRESENTATION OF DRAWINGS

[0054] Other features and advantages will become apparent from the following description, which is purely illustrative and not exhaustive, and should be read in conjunction with the accompanying figures, among which:

[0055] - Figure 1 schematically represents an aircraft comprising systems propulsive,

[0056] - [Fig.2] schematically represents, in partial view and in section, a example of a propulsion system in which the fan section is enclosed,

[0057] - [Fig. 3] schematically represents, in partial view and in section, a example of a propulsion system in which the fan section is unfaired,

[0058] - Figure 4 schematically represents a first example of a mechanism planetary reduction,

[0059] - Figure 5 schematically represents a first example of a mechanism epicycloidal reduction

[0060] - Figure 6 schematically represents, in partial view and in section, a example of a blower section in which the blower section is enclosed,

[0061] - [Fig. 7] schematically represents, in partial view and in section, a example of a blower section in which the blower section is unshrouded,

[0062] - Figure 8 schematically illustrates a partial weft plane of the fibrous reinforcement of the [Fig.7]

[0063] - Figure 9 schematically represents, in partial view and in section, a example of a blower section in which the blower section is unshrouded,

[0064] - Figure 10 schematically illustrates a partial chain plane of the fibrous reinforcement of the [Fig.9],

[0065] - Fig. 11 schematically represents a cross-section of two blades in a blower section, and

[0066] - [Fig. 12] schematically represents in partial view and perspective cavalière an example of a blower section. DETAILED DESCRIPTION OF A METHOD OF IMPLEMENTATION

[0067] In the example illustrated in [Fig. 1], the aircraft is an airplane 100 comprising a fuselage 101 and two wings 102. In this example, the aircraft comprises two propulsion systems 1, each propulsion system 1 being attached to a respective wing 102 of the airplane 100 by means of a pylon. In another embodiment, the aircraft could comprise one or more propulsion system(s) attached to the fuselage 101.

[0068] Fig. 2 schematically represents, in partial view and in section, a first example of a propulsion system 1.

[0069] In this example, the propulsion system 1 is a twin-body gas turbine engine with a shrouded fan.

[0070] In [Fig. 2], the propulsion system 1 has a principal direction extending along a longitudinal axis X. The propulsion system 1 comprises a fan section 2 and a primary body 3, often called the "gas generator". The direction X also defines the principal direction of gas flow through the propulsion system 1.

[0071] The blower section 2 comprises a blower 22 and a blower housing 12. The blower 22 comprises a blower rotor 9. The blower housing 12 surrounds the blower rotor 9. The blower rotor 9 is rotatably mounted relative to the blower housing 12.

[0072] In the example illustrated in [Fig.2], the fan section 2 is enclosed. The propulsion system 1 comprises a fan casing 12 which surrounds the fan section 2 or, alternatively, a nacelle 28 which surrounds the fan section 2.

[0073] With reference to [Fig. 6], which shows an example where the fan section 2 is enclosed, the fan section 2 comprises an inner platform 34 and an inner face 35 of the fan housing 12 or nacelle 28, defining between them a gas flow channel 36. The flow channel 36 thus extends from the inner platform 34 to the inner face 35. The term "platform" here refers to any element of the propulsion system 1 from which a fan blade can be mounted, or at the very least, any element of the propulsion system from which a fan blade can extend substantially radially. The platform may, in particular, be a hub or a housing that surrounds the axis X of the propulsion system 1. The inner face 35 of the fan housing or nacelle is also referred to as the "outer platform 35" in the following text.The inner face 35 surrounds the inner platform 34, such that the inner platform 34 lies radially between the X-axis of the propulsion system and the inner face 35. The inner platform 34 and the inner face 35 each define a flow-stream side surface.

[0074] These surfaces can be at variable distances from the X-axis of the propulsion system 1, as illustrated in [Fig. 6]. The inner surface defined by the inner platform 34 can move away from the X-axis of the propulsion system 1 when traversing this inner surface in the direction of gas flow. The outer surface defined by the outer platform 35 can move towards the X-axis of the propulsion system 1 when traversing this outer surface in the direction of gas flow.

[0075] The outer surface defined by the outer platform 35 and the inner surface defined by the inner platform 34 can alternatively be cylindrical surfaces, each at a constant radial distance from the X-axis of the propulsion system 1.

[0076] The fan rotor 9 comprises at least one blade 14 extending in the duct 36.

[0077] The fan blade 14 has a leading edge 14a and a trailing edge 14b (see, for example, [Fig. 6]). The leading edge 14a is configured to extend in relation to the flow of gases entering the blower rotor 9.It corresponds to the forward part of an airfoil that faces the airflow and divides the airflow into an intrados flow and an extrados flow. The trailing edge 14b, on the other hand, corresponds to the rear part of the airfoil, where the intrados and extrados flows meet. Note here that, when the blade 14 includes a leading edge and / or trailing edge shield, the leading edge 14a (respectively the trailing edge 14b) of the blade 14 corresponds to the forward part of the shield profile that reconstitutes the leading edge (respectively the rear part of the shield profile that reconstitutes the trailing edge 14b) and whose function is to divide the flow into an intrados flow and an extrados flow (respectively to join the flows).

[0078] The blade 14 comprises a blade root 25 fixed to the fan rotor and a blade extending in the groove 36 over a blade height 47 radially outward with respect to the X-axis of the propulsion system 1. The blade comprises an internal radial boundary 37 located at the interface of the blade and the inner platform 34. The blade extends over the blade height 47 from the internal radial boundary 37 to a blade tip 21 located on the outer platform 35. The blade height 47 is measured along a radial axis R orthogonal to the X-axis of the propulsion system 1 and passing through the X-axis of the propulsion system 1. Preferably, and with reference to [Fig. 6], the blade height 47 is measured between an intersection 43 between the inner platform 34 and the leading edge 14a and an upstream point 45 of the tip dawn 21 located on the leading edge 14a.When the fan section is faired, blade 14 extends into channel 36, blade apex 21 is located on outer platform 35 and upstream point 45 is located at the intersection between outer platform 35 and leading edge 14a.

[0079] The blower blade 14 further has a straight chord at the blade apex 39 extending from the leading edge 14a to the trailing edge 14b along the blade apex 21 and a straight curve at the blade root 38 extending from the leading edge 14a to the trailing edge 14b along the blade root 37. These are referred to as a straight chord or normal chord. designate the distance of the segment between the leading edge and the trailing edge without the segment being projected.

[0080] The direct rope at dawn summit 39 extends from the upstream point 45 of dawn summit 21 located on the leading edge 14a to a downstream point 46 of dawn summit 21 located on the trailing edge 14b.

[0081] When the blower section is faired, the direct chord at the top of the blade 39 extends along the outer platform 35 and corresponds to the length of the straight segment which connects on the one hand the upstream intersection point 45 between the outer platform 35 and the leading edge 14a and on the other hand the downstream intersection point 46 between the outer platform 35.

[0082] Similarly, the direct chord at the base of the blade 38 extends from point 43 of the internal radial boundary 37 located on the leading edge 14a to point 44 of the internal radial boundary 37 located on the trailing edge 14b. The direct chord at the base of the blade 38 extends from the leading edge 14a to the trailing edge 14b along the inner platform 34. The direct chord at the base of the blade 38 corresponds to the length of the straight segment that connects, on the one hand, the point of intersection 43 between the inner platform 34 and the leading edge 14a and, on the other hand, the downstream point of intersection 44 between the inner platform 34.

[0083] It should be noted that the straight segments mentioned above are not necessarily contained in a radial plane defined by the X axis of the propulsion system and a radial direction X. Similarly, the points of the chord are not necessarily all at the same distance from the X axis of the propulsion system.

[0084] The fan blade 14 further has an axial chord at the blade apex extending along the X axis from the leading edge 14a to the trailing edge 14b and an axial chord at the blade root extending along the X axis from the leading edge 14a to the trailing edge 14b. The term axial chord at the blade apex (respectively at the blade root) refers to the length of the projection along the X axis of the direct chord at the blade apex (respectively at the blade root).

[0085] We can define an average axial chord equal to the average between the axial chord at the base of the blade and the axial chord at the top of the blade.

[0086] D is the diameter of the fan rotor, measured in a plane normal to the X-axis of the propulsion system 1 from the X-axis to the intersection point 45 between the blade tip 21 and the leading edge 14a of the blade. The diameter D is expressed in meters. The diameter D of the fan rotor 9 can be between 70 inches (177.8 cm) and 120 inches (304.8 cm) inclusive, in particular between 84 inches (213.36 cm) and 105 inches (266.7 cm) inclusive, and preferably between 85 inches (215.9 cm) and 105 inches (266.7 cm) inclusive. For example, the diameter D of the fan rotor 9 is approximately 90 inches (228.6 cm). These different values ​​of the diameter D allow for integration of the propulsion system 1 in a conventional manner, in particular under a wing of aircraft 100. Parameters of the invention

[0087] The blade 14 has a first axial chord parameter corresponding to a ratio of the product of the mean axial chord by the axial chord at the blade root to the product of the square of the blade height 47 by the axial chord at the blade tip. The first axial chord parameter is calculated by expressing its constituent terms in meters; the value of the first axial chord parameter is considered dimensionless. The first axial chord parameter can be denoted Pci.

[0088] It respects the relation p _ c^cxo in which Cxm denotes the axial chord tu — n xc.H00 average, designates the axial chord, h designates the blade height 47 and CxiOo designates the axial chord at the blade apex.

[0089] The blade 14 has a first speed parameter corresponding to the difference between the product of the maximum permissible speed of the blower rotor 9, expressed in rad / s, and the value 2.047 x 10³ s / rad, and the value 1.3403 x 10'. The maximum permissible speed corresponds to the maximum speed of the blower in normal operation. This term is also known by the English name "Maximum Permissible Rotational Speed". The first speed parameter can be denoted Pvl.

[0090] It respects the relation pv\ = 2,047 x 10'3 x Xn-1,3403 x 10 1 which can also be written Pvl = 0,002047 x X„ - 0,13403 and in which Xn designates the maximum permissible regime.

[0091] The blade 14 has a second axial chord parameter corresponding to a ratio of the axial chord at the blade root to a product of the square of the average axial chord, the blade height 47, and the axial chord at the blade tip. The second axial chord parameter is calculated by expressing its constituent terms in meters; the value of the second axial chord parameter is considered dimensionless. The second axial chord parameter can be denoted Pc2.

[0092] He respects the relationship.

[0093] The blade 14 has a second speed parameter corresponding to a difference of a product of the maximum permissible speed of the blower rotor 9 expressed in rad / s by the value 2.757x10 1 s / rad and the value 67.414. The second speed parameter can be noted Pv2.

[0094] It respects the relation p^2 — 2, 757 x 10'1 x Xn - 67.414 which can also be written Pvl = 0,2757 x Xn - 67,414.

[0095] In order to optimize the performance of propulsion system 1:

[0096] - the first axial chord parameter is less than or equal to the first parameter of speed, or

[0097] - the second axial chord parameter is less than or equal to the second parameter speed.

[0098] At least one of the first or second axial chord parameters is chosen to be sufficiently small to significantly increase the axial chord at the blade tip relative to the other blade parameters. The blade tip corresponds to the part of the blade where the axial and tangential velocities are highest. It is therefore the part of the blade that contributes most to the engine efficiency. By increasing the axial chord at the blade tip, the blade efficiency is increased.

[0099] We can also define a third speed parameter pv3 and a fourth speed parameter pv4.

[0100] The blade 14 has the third speed parameter pv3 which corresponds to a difference of a product of a maximum permissible speed of the blower rotor 9 expressed in rad / s by the value ]5 4] x 10' s / rad and the value 9.52 x 10'1-

[0101] The third speed parameter complies with the relation Pv3 = 1.41 x 103 x X„-9.52 x 10'1 which can also be written Pv3 = 0.00141 xl„- 0.952.

[0102] The blade 14 has the fourth speed parameter pv4 which corresponds to a difference of a product of the maximum permissible speed of the blower rotor 9 expressed in rad / s by the value 2067 X 104 s / rad and the value 50.5.

[0103] It respects the relation pv4 — 2.067 X 104 x Xn - 50.5 which can also be written Pv4 = 0.2067 xXn- 50.5.

[0104] Advantageously, the first axial chord parameter is greater than or equal to the third velocity parameter and / or the second axial chord parameter is greater than or equal to the fourth velocity parameter. Initial parameters and flexural margin

[0105] Choosing a relatively low value for the first axial chord parameter tends to decrease the margin with the natural mode of vibration in bending of the blade, known as the bending margin. Bending here refers to a deformation of the blade during which the blade tip approaches the internal radial limit, the blade curving around a direction parallel to the drive axis, i.e., the X-axis of the propulsion system. The margin depends in particular on the difference between the blade's rotational frequency in maximum permissible operating conditions and the frequency of the natural mode of vibration in bending.

[0106] In order to increase the bending margin in the case where the first axial chord parameter is less than or equal to the first velocity parameter, the blade includes a composite material having a stiffness of a lower portion 55 greater than a stiffness of an upper portion 57. Second parameters and torsional margin

[0107] Choosing a relatively low value for the second axial chord parameter tends to decrease the margin with the blade's natural torsional vibration mode, known as the torsional margin. Torsion here refers to a deformation of the blade during which the blade tip rotates about a radial axis relative to the blade root, the blade curving about a direction radial to the drive axis, i.e., the X-axis of the propulsion system. The margin with the blade's natural torsional mode depends, in particular, on the difference between the blade's rotational frequency at maximum permissible operating conditions and the frequency of its natural torsional vibration mode.

[0108] In order to increase the torsional margin in the case where the second axial chord parameter is less than or equal to the second velocity parameter, the blade comprises a composite material having a stiffness of an upstream portion 75 greater than a stiffness of a downstream portion 77. Fiber reinforcement

[0109] With reference to Figures 6 and 7, the blade 14 comprises a material structure composite comprising a fibrous reinforcement obtained by three-dimensional weaving of weft strands 53 and warp strands 54 and a matrix in which the fibrous reinforcement is embedded.

[0110] Three-dimensional weaving is understood to mean that the warp yarns follow sinuous paths in order to link together weft yarns belonging to different weft yarn layers, with the exception of unlinking. It should be noted that a three-dimensional weave, particularly an interlock weave, may include 2D surface weaves. Different three-dimensional weaves may be used, such as interlock, multi-satin, or multi-silk weaves, for example, as described in particular in WO 2006 / 136755.

[0111] In relation to [Fig.6], the direction of a warp strand 54 goes from the foot of the blade 37 to the top of the blade 21 and the direction of a weft yarn goes from the leading edge 14a to the trailing edge 14b.

[0112] In the fibrous reinforcement, warp planes and weft planes can be defined. A warp plane is a plane globally orthogonal to the principal directions of extension of a plurality of columns of warp strands from the blade root 35 to the blade tip 21, each warp strand crossing the warp plane. A weft plane is a plane globally orthogonal to the principal directions of extension of a plurality of lines of weft strands from the leading or trailing edge, each weft strand crossing the weft plane. A warp plane is formed of a plurality of Weft strands are defined by rows of warp strands, each row separated from the immediately adjacent row by a warp plane. A weft plane is formed by a plurality of warp strand columns, each column separated from the immediately adjacent column by a weft plane. A strand density can be defined within the composite material structure, corresponding to the number of strands per unit volume of the structure.

[0113] The fibrous reinforcement can be formed from a one-piece fibrous preform obtained by three-dimensional weaving. It comprises fibers that may be made of carbon, glass, basalt, or aramid, among other things. A carbon fiber may, in particular, have a Young's modulus greater than or equal to 230 GPa and less than or equal to 450 GPa, and preferably greater than or equal to 250 GPa and less than or equal to 300 GPa, and even more preferably greater than or equal to 275 GPa and less than or equal to 280 GPa. A glass fiber may, in particular, have a Young's modulus greater than or equal to 160 GPa and less than or equal to 170 GPa, for example, 165 GPa. A basalt fiber may, in particular, have a Young's modulus greater than or equal to 200 GPa and less than or equal to 250 GPa, for example, 227 GPa. An aramid fiber can, in particular, have a Young's modulus greater than or equal to 280 GPa and less than or equal to 320 GPa, for example 302 GPa.

[0114] The matrix, for its part, is typically a polymer matrix, for example epoxy, bismaleimide or polyimide. The blade 14 is then formed by molding using a vacuum resin injection process of the RTM type (for "Resin Transfer Moulding" i.e. resin transfer moulding) or VARTM type (for "Vacuum Resin Transfer Moulding" i.e. vacuum resin transfer moulding).

[0115] The fibrous reinforcement is formed by three-dimensional weaving of warp strands and weft strands.

[0116] The weft strands 53 and the warp strands 54 are interlaced in the same plane. Different weaving patterns are possible for creating the interlacing.

[0117] Within the composite material structure, a density of crossing between warp strands and weft strands can be defined, corresponding to the number of crossings of warp strands and weft strands per unit volume of the structure. Stiffness in the case of the first parameters

[0118] In the case where the first axial chord parameter is less than or equal to the first velocity parameter, the blade comprises a lower portion 55 which includes the blade root 25. Referring to Figures 6 and 7, the lower portion 55 extends radially outwards from the blade root 25 to the internal radial limit. 37 and beyond the internal radial limit 37 to a first intermediate level 56 located between the internal radial limit 37 and the blade tip 21. For example, the lower portion 55 extends from the internal radial limit 37 to the blade tip 21 over a height hl greater than or equal to 15% and less than or equal to 25% of the blade height. In this case, the first intermediate level 56 is separated from the internal radial limit 37 by a length greater than or equal to 15% and less than or equal to 25% of the blade height, and the first intermediate level 56 is separated from the blade tip 21 by a length greater than or equal to 75% and less than or equal to 85% of the blade height.

[0119] In the case where the first axial chord parameter is less than or equal to the first velocity parameter, the blade 14 has an upper portion 57. The upper portion 57 extends radially towards the X axis of the propulsion system from the blade tip 21 to a second intermediate level 59 located between the first intermediate level 56 and the blade tip 21.

[0120] In the case where the first axial chord parameter is less than or equal to the first speed parameter, the blade 14 may have an intermediate portion 58 located between the lower portion 55 and the upper portion 57. The intermediate portion extends from the lower portion 55 to the upper portion 57, that is to say, the intermediate portion extends from the first intermediate level 56 to the second intermediate level 59. For example, the intermediate portion 58 extends over a height h3 greater than or equal to 5% and less than or equal to 30% of the blade height.

[0121] When the intermediate portion 58 extends over a height h3 greater than or equal to 5% and less than or equal to 30% of the blade height and when the lower portion 55 extends from the internal radial limit 37 towards the blade tip 21 over a height hl greater than or equal to 15% and less than or equal to 25% of the blade height, then the upper portion 57 extends from the blade tip 21 over a height h2 greater than or equal to 45% and less than or equal to 80% of the blade height, and the second intermediate level 59 is separated from the blade tip 21 by a length greater than or equal to 45% and less than or equal to 80% of the blade height.

[0122] In the case where the first axial chord parameter is less than or equal to the first velocity parameter, the stiffness of the lower portion 55 is greater than the stiffness of the upper portion 57.

[0123] By stiffness, we understand here the Young's modulus (E). In one embodiment, the stiffness of the lower portion 55 is between 1.2 and 1.5 times the stiffness of the upper portion 57.

[0124] The difference in stiffness between the lower portion 55 and the upper portion 57 can be obtained in different ways.

[0125] In a first option, the weft strands 53 comprise first weft strands and second weft strands, the lower portion 55 comprising first weft strands and no second weft strands, and the upper portion 57 comprising second weft strands and no first weft strands, the stiffness of the first weft strands being greater than the stiffness of the second weft strands. The first and second weft strands extend continuously from the leading edge to the trailing edge.

[0126] According to this first option, the density of the first strands gradually decreases in the intermediate portion 58 from the lower portion 55 towards the upper portion 57, and the density of the second strands gradually decreases in the intermediate portion 58 from the upper portion 57 towards the lower portion 55. These gradual decreases can, for example, be achieved by successively removing the first strands from the weave of the preform, at the level of the different warp and / or weft planes constituting the parts of the intermediate portion 58 and by cutting them at the level of the surface of the fibrous reinforcement before injection, and by simultaneously introducing the second strands between these warp and / or weft planes, as described in document FR3087701.

[0127] With reference to Figures 7 and 8, the warp planes C2 and C3 are located in the intermediate portion 58, the warp plane Cl is located in the lower portion 55 and the warp plane C4 is located in the upper portion 57. [Fig. 8] illustrates a cross-sectional view of the fibrous preform along a weft plane including the stacking axis of the blade 14, the weft plane being substantially parallel to the radial axis R. It should be noted that in [Fig. 8], only the weft strands have been shown, the warp strands having been omitted in order to simplify the reading of the figure.

[0128] As can be seen in [Fig.8], the first two lines of weft strands L1 and L2, which are part of the internal portion 11 of the fibrous reinforcement 5, comprise only first strands 60. These first two lines of weft strands L1, L2 are located in the lower portion 55.

[0129] The third weft strand line L3 is part of the intermediate portion 58, near the first intermediate level 56. This third weft strand line L3 includes a single second strand 61. The following weft strand lines L4-L10 each include a second strand 61 in addition to the weft strand line immediately preceding it, up to the eleventh weft strand line L11 and the following ones which include only second strands 61 and therefore form part of the upper portion 57.

[0130] In this way, the lower portion 55, the upper portion 57, and the intermediate portion 58 are formed as a single piece during the three-dimensional weaving of the blade 14. In order to ensure the transition of mechanical properties between the portion lower 55 and upper portion 57 at the level of the intermediate portion 58, the percentage relative to the total number of weft strands in a line of second strands 61 introduced between two immediately adjacent weft strand lines, i.e., separated by only one column of warp strands of the intermediate portion 58, is at most 30%. Preferably, this percentage is between 5% and 15%.

[0131] The first weft strands have a relatively high Young's modulus, for example greater than 250 GPa, preferably greater than 270 GPa, and are designed to meet the blade design criteria related to the blade's frequency status, particularly regarding the margin between, on the one hand, the blade's rotational frequency and, more generally, the driving harmonics, and on the other hand, the natural frequency of the blade's bending modes. For example, the first weft strands may comprise carbon fibers, typically HS* T300 carbon fibers (E = 284 GPa, A = 1.5%), HS TR30S (E = 356 GPa, A = 1.9%), or HS T700 (E = 395 GPa, A = 2.1%), or even high-modulus aramid fibers of the Dupont Kevlar 49 type (E = 302, A = 2.4%). E here denotes Young's modulus E and A is the elongation at break.

[0132] The second weft strands can, for example, comprise glass fibers, typically E-GLASS type glass fibers (E = 165 GPa, A = 4.4%) or S-2 GLASS type glass fibers (E = 267 GPa, A = 5.2%), or basalt fibers (E = 227 GPa, A = 3%), or polyester fibers (E = 268 GPa, A = 3.5%).

[0133] In a second option, a weft strand density in the lower portion 55 is greater than a weft strand density in the upper portion 57.

[0134] In a third option, a crossing density between warp strands and weft strands in the lower portion 55 is greater than a crossing density between warp strands and weft strands in the upper portion 57.

[0135] The three options can be combined two by two or all three simultaneously.

[0136] Generally, to ensure the transition of mechanical properties between the lower portion 55 and the upper portion 57, at most 30% of the warp and / or weft strands are preferably modified between two immediately adjacent warp planes (i.e., separated by only one weft line) or between two immediately adjacent weft planes (i.e., separated by only one warp column). Preferably, between 5% and 15% of the strands are modified between two immediately adjacent planes. For example, in the first option, between two successive warp planes, at most 30% of the first strands 60 removed from the fiber preform and an equal number of second strands 61 introduced into the fiber preform from the surface can replace the first strands 60 removed. For example, in the second option, a maximum of 30% strands can be added between two successive warp planes. For example, in the third option, a maximum of 30% interlacing can be added between two successive warp planes. Stiffness values ​​in the case of the second parameters

[0137] In the case where the second axial chord parameter is less than or equal to the second velocity parameter, the blade 14 has an upstream portion 75 which includes the leading edge 14a. The upstream portion 75 extends axially downstream from the leading edge 14a of the blade 25 to a third intermediate level 76 located between the leading edge 14a and the trailing edge 14b.

[0138] The upstream portion 75 extends over the entire height h of the blade 14, from the foot 25 to the apex 21. The upstream portion 75 extends substantially axially over a portion of the direct chord length of the composite material structure. This direct chord length varies between the foot 25 and the apex 21 of the blade 14. For example, at the blade foot 25, the upstream portion 75 can extend axially over a length between 25% and 40% of the chord length L, for example, over a length equal to approximately one-third of the direct chord length at the blade foot 25. At mid-height h / 2 of the blade, the upstream portion 75 can extend axially over a length between 10% and 30% of the direct chord length, for example over a length equal to about a quarter of the direct chord length at mid-height of the blade 14. At the top 21, the upstream portion 75 can be narrower or even have a length of zero.

[0139] In the case where the second axial chord parameter is less than or equal to the second velocity parameter, the blade 14 has a downstream portion 77 which includes the trailing edge 14b. With reference to [Fig.9], the downstream portion 77 extends radially upstream from the trailing edge 14b to a fourth intermediate level 79 located between the third intermediate level 76 and the trailing edge 14b.

[0140] In the case where the second axial chord parameter is less than or equal to the second velocity parameter, the blade 14 may have a central portion 78 located between the upstream portion 75 and the downstream portion 77. With reference to [Fig.9], the central portion extends from the upstream portion 75 to the downstream portion 77, that is to say that the intermediate portion extends from the third intermediate level 76 to the fourth intermediate level 79.

[0141] The central portion 78 extends axially over a length between 5% and 10% of the direct chord length. The axial length of the central portion 78 can be constant over the entire blade height to ensure a smooth transition between the upstream portion 75 and the downstream portion 77. Alternatively, the length of the central portion 78 can be roughly proportional to the length of the upstream portion 75. In this embodiment, the length of the central portion 78 is maximum at the foot 25 of dawn 14, then from 40% to 50% of height h, the length of the central portion 78 can gradually decrease until it becomes substantially zero at the top 21.

[0142] In the case where the second axial chord parameter is less than or equal to the second velocity parameter, the stiffness of the upstream portion 75 is greater than the stiffness of the downstream portion 77.

[0143] By stiffness, we understand here the Young's modulus (E). In one embodiment, the stiffness of the lower portion 55 is between 1.2 and 1.5 times the stiffness of the upper portion 57.

[0144] The difference in stiffness between the upstream portion 75 and the downstream portion 77 can be obtained in different ways.

[0145] In a first option, the chain strands 54 comprise first and second chain strands, the upstream portion 75 comprising more first chain strands than second chain strands and the downstream portion 77 comprising second chain strands and no first chain strands, the stiffness of the first chain strands being greater than the stiffness of the second chain strands. The first and second chain strands extend continuously from the leading edge to the trailing edge.

[0146] According to this first option, the density of the first strands gradually decreases in the central portion 78 from the upstream portion 75 towards the downstream portion 77, and the density of the second strands gradually decreases in the central portion 78 from the downstream portion 77 towards the upstream portion 75. These gradual decreases can, for example, be achieved by successively removing the first strands from the weaving of the preform, at the level of the different warp and / or weft planes constituting the parts of the central portion 78 and by cutting them at the level of the surface of the fibrous reinforcement before injection, and by simultaneously introducing the second strands between these warp and / or weft planes, as described in document FR3087701.

[0147] A schematic example of the warp plane C0 of the fibrous reinforcement of blade 14 in [Fig. 9] is shown in [Fig. 10]. The warp plane C0 is a cross-sectional view of the fibrous preform along a plane normal to the stacking axis Z, at the foot 25 of blade 14 (see section plane EE in [Fig. 9]). Note that [Fig. 10] illustrates a warp plane C0 in which only the warp strands (i.e., in the stacking direction of the sections) are shown, the weft strands having been omitted to simplify the reading of the figure. This [Fig. 10] thus schematically illustrates a first example of warp strand hybridization.

[0148] As can be seen in [Fig. 10], within the upstream portion 75 which here extends over approximately one-third of the length of the rope L at the foot 25 of the blade 14, between 70% and 90% of the warp strands are first strands 83, the remainder being made up of second strands 84. Within the central portion 78, the density of first strands 84 gradually decreases from the upstream portion 75 towards the downstream portion 77, until it becomes zero (the density of second strands 83 gradually increasing in a complementary manner).

[0149] The first chain strands have a relatively high Young's modulus, for example, greater than 250 GPa, preferably greater than 270 GPa, and are designed to meet the blade design criteria related to the blade's frequency status, particularly regarding the margin between, on the one hand, the blade's rotational frequency and, more generally, the driving harmonics, and on the other hand, the natural frequency of the blade's bending modes. For example, the first chain strands may include carbon fibers, typically HS* T300 carbon fibers (E = 284 GPa, A = 1.5%), HS TR30S (E = 356 GPa, A = 1.9%), or HS T700 (E = 395 GPa, A = 2.1%), or even high-modulus aramid fibers of the Dupont Kevlar 49 type (E = 302, A = 2.4%). E here denotes Young's modulus E and A is the elongation at break.

[0150] The second warp strands may, for example, comprise glass fibers, typically E-GLASS type glass fibers (E = 165 GPa, A = 4.4%) or S-2 GLASS type glass fibers (E = 267 GPa, A = 5.2%), or basalt fibers (E = 227 GPa, A = 3%), or polyester fibers (E = 268 GPa, A = 3.5%).

[0151] In a second option, a warp strand density in the upstream portion 75 is greater than a warp strand density in the downstream portion 77.

[0152] In a third option, a crossing density between warp strands and weft strands in the upstream portion 75 is greater than a crossing density between warp strands and weft strands in the downstream portion 77.

[0153] The three options can be combined two by two or all three simultaneously.

[0154] Generally, in order to ensure the transition of mechanical properties between the upstream portion 75 and the downstream portion 77, at most 30% of the warp and / or weft strands are preferably modified between two immediately adjacent warp planes (i.e., separated by only one weft line) or between two immediately adjacent weft planes (i.e., separated by only one warp column). Preferably, between 5% and 15% of the strands are modified between two immediately adjacent planes. For example, in the first option, between two successive weft planes, at most 30% of the first strands 83 removed from the fiber preform and an equal number of second strands 84 are introduced into the fiber preform from the surface to replace the first strands 83 removed. For example, in the second option, at most 30% of the warp strands may be added between two successive frame planes. For example, in the third option, a maximum of 30% overlap can be added between two successive frame planes. Number of blades

[0155] The fan rotor 9 may comprise a plurality of fan blades 14. Each of the fan blades 14 may be fixed relative to the fan hub 13 or have a variable pitch. In the latter case, each of the fan blades 14 is pivotally mounted relative to the fan hub 13 about a pitch axis and is connected to a pitch-changing mechanism (not shown) mounted in the propulsion system 1. The pitch-changing mechanism allows the pitch angle of the fan blades 14 to be adjusted according to the flight phases.

[0156] The blower rotor 9 comprises at least ten blower blades 14 and at most twenty-four blower blades 14, preferably at least sixteen blower blades 14 and at most twenty-four blower blades 14, and even more preferably at least seventeen blower blades 14 and at most twenty-two blower blades 14. [Fig. 12] illustrates the case where the blower rotor 9 comprises twenty-two blades.

[0157] The fan section 2 may also include a fan stator 16 fixedly mounted on the fan housing 12. The fan stator 16 includes fixed blades 17 generally referred to as "outlet guide vanes" (or "OGV"). This set of fixed blades serves to straighten and regulate the airflow downstream of the fan rotor 9 to contribute to engine thrust. This set of fixed blades also acts as a noise reducer.

[0158] Alternatively, the outlet blades 17 could have variable pitch. If so, and similarly to the fan blades 14 of the fan rotor 9, the base of the outlet blades 17 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism (not shown), the pitch being adjusted according to the flight phases by the pitch-changing mechanism.

[0159] The number of outlet blades 17 depends on the acoustic criteria defined for the propulsion system 1 and is at least equal to the number of fan blades 14. Engine architecture

[0160] In relation to [Fig.2], the primary body 3 comprises a compressor section 29, a combustion chamber 6 and a turbine section 30.

[0161] Compressor section 29 includes a low pressure compressor 4 and a high pressure compressor 5.

[0162] The low-pressure compressor 4 includes a rotor 41 suitable for being driven in rotation relative to the housing 31 of the propulsion system 1 and a stator 42 fixedly mounted on the housing 31.

[0163] The rotor 41 of the low-pressure compressor 4 comprises movable wheels 4a and the stator 42 of the low-pressure compressor 4 comprises fixed wheels 4b. The movable wheels 4a are arranged alternately with the fixed wheels 4b, thus forming a succession of low-pressure compressor stages.

[0164] Similarly, the high-pressure compressor 5 includes a rotor 51 suitable for being driven in rotation relative to the housing 31 of the propulsion system 1 and a stator 52 fixedly mounted on the housing 31.

[0165] The rotor 51 of the high-pressure compressor 5 includes movable wheels 5a and the stator 52 of the high-pressure compressor 5 includes fixed wheels 5b. The movable wheels 5a are arranged alternately with the fixed wheels 5b, thus forming a succession of high-pressure compressor stages.

[0166] The turbine section 30 comprises a high-pressure turbine 7 and a low-pressure turbine 8.

[0167] The high-pressure turbine 7 comprises a rotor 71 suitable for being driven in rotation relative to the housing 31 of the propulsion system 1 and a stator 72 fixedly mounted on the housing 31.

[0168] The rotor 71 of the high-pressure turbine 7 comprises rotating wheels 7a and the stator 72 of the high-pressure turbine 7 comprises fixed wheels 7b. The rotating wheels 7a are arranged alternately with the fixed wheels 7b, thus forming a succession of high-pressure turbine stages.

[0169] Similarly, the low-pressure turbine 8 comprises a rotor 81 suitable for being driven in rotation relative to the housing 31 of the propulsion system 1 and a stator 82 fixedly mounted on the housing 31.

[0170] The rotor 81 of the low-pressure turbine 8 comprises rotating wheels 8a and the stator 82 of the low-pressure turbine 8 comprises fixed wheels 8b. The rotating wheels 8a are arranged alternately with the fixed wheels 8b, thus forming a succession of low-pressure turbine stages.

[0171] The propulsion system 1 includes a low-pressure shaft 11 connecting the rotor 41 of the low-pressure turbine 4 to the rotor 81 of the low-pressure compressor 8, the low-pressure shaft 11 being mounted rotatably relative to the housing 31 around the longitudinal axis X.

[0172] When the propulsion system 1 is in operation, the rotor 81 of the low-pressure turbine 8 drives the rotor 41 of the low-pressure compressor 4 through the low-pressure shaft 11.

[0173] The propulsion system 1 further comprises a blower shaft 20 and a reduction mechanism 19. The blower rotor 9 is fixedly mounted on the blower shaft 20. The reduction mechanism 19 has an inlet and an outlet. The inlet of the reduction mechanism 19 is connected to the low-pressure shaft 11 and the outlet of the reduction mechanism 19 is connected to the blower shaft 20. Thus, when the system propulsion 1 is in operation, the rotor 81 of the low pressure turbine 8 drives in rotation not only the rotor 41 of the low pressure compressor 4, but also the blower rotor 9, via the low pressure shaft 11, the reduction mechanism 19 and the blower shaft 20.

[0174] Thanks to the reduction mechanism 19, the blower rotor 9 is driven into rotation at a speed lower than the rotational speed of the rotor 41 of the low pressure turbine 4.

[0175] The reduction mechanism 19 thus makes it possible to independently control the rotation speed of the blower 22 and the rotation speed of the low pressure turbine 8 and the low pressure compressor 4.

[0176] The low-pressure turbine 8, the low-pressure shaft 11, the low-pressure compressor 4, the blower shaft 20, the reduction mechanism 19 and the blower 22 together form the "low-pressure body" of the propulsion system 1.

[0177] The propulsion system 1 further comprises a high-pressure shaft 10 connecting the rotor 51 of the high-pressure turbine 5 to the rotor 71 of the high-pressure compressor 7, the high-pressure shaft 10 being rotatably mounted relative to the housing 31 about the longitudinal axis X. The high-pressure shaft 10 is coaxial with the low-pressure shaft 11 and extends around the low-pressure shaft IL

[0178] When the propulsion system 1 is in operation, the rotor 81 of the low-pressure turbine 8 drives the rotor 51 of the low-pressure compressor 5 through the low-pressure shaft IL

[0179] The high-pressure turbine 7, the high-pressure shaft 10 and the high-pressure compressor 4 together form the "high-pressure body" of the propulsion system 1.

[0180] The low-pressure shaft 11 and the high-pressure shaft 10 can be co-rotating, i.e., driven in the same direction of rotation around the longitudinal axis X. Alternatively, the low-pressure shaft 11 and the high-pressure shaft 10 can be contra-rotating, i.e., driven in opposite directions of rotation around the longitudinal axis X.

[0181] The dual-body propulsion system 1 may in particular include a single-stage high-pressure turbine 7, i.e. comprising exactly one stage, or a two-stage high-pressure turbine 7, i.e. comprising exactly two stages (as illustrated in the example in [Fig.2]).

[0182] The high-pressure compressor 5 comprises at least eight stages (as illustrated in the example in [Fig.2]) and at most eleven stages.

[0183] The low-pressure turbine 8 comprises at least three stages (as illustrated in the example in [Fig.2]) and at most seven stages.

[0184] The low-pressure compressor 4 comprises at least two stages and at most four stages.

[0185] When the propulsion system 1 is in operation, an airflow F entering the propulsion system 1 passes through the blower 22 and is then divided between a primary airflow Fl and a secondary airflow F2, which flow upstream to downstream in the propulsion system 1 in the direction of gas flow through the propulsion system 1.

[0186] The secondary airflow F2, also called the "bypass airflow", flows in the secondary vein, around the primary body 3. The secondary airflow F2 cools the periphery of the primary body 3 and is used to generate most of the thrust provided by the propulsion system 1.

[0187] The primary airflow Fl flows in a primary channel inside the primary body 3, passing successively through the compressor section 29 (low-pressure compressor 4 and high-pressure compressor 5), the combustion chamber 6 where it is mixed with fuel to serve as an oxidizer, and the turbine section 30 (high-pressure turbine 7 and low-pressure turbine 8). The passage of the primary airflow Fl through the turbine section 30, receiving energy from the combustion chamber 6, causes rotation of the impellers 7a, 8a of the turbine section 30, which in turn drive the impellers 4a, 5a of the compressor section 29 and the blower rotor 9.

[0188] In order to improve the propulsive efficiency of the propulsion system 1 and to reduce its specific fuel consumption as well as the noise emitted by the fan section 2, the propulsion system 1 may have a high bypass ratio. By "high" bypass ratio, it is meant a bypass ratio greater than or equal to 10, for example, between 10 and 80 inclusive, preferably between 10 and 35 inclusive, preferably between 10 and 18 inclusive. The bypass ratio is defined as a ratio between the mass flow rate of the secondary airflow F2 and the mass flow rate of the primary airflow Fl, these mass flow rates being measured when the propulsion system 1 is stationary, uninstalled, in takeoff mode in a standard atmosphere (as defined by the International Civil Aviation Organization (ICAO) Manual, Doc 7488 / 3, 3rd edition) and at sea level.By "not installed", it is meant that the measurements are carried out when the propulsion system 1 is on a test bench (and not installed on an aircraft), the measurements being then simpler to perform.

[0189] In a propulsion system 1 including a reduction mechanism 19 such as that illustrated in [Fig. 2], decoupling the rotational speed of the fan 22 and the rotational speed of the low-pressure turbine 8 makes it possible to reduce the rotational speed and the pressure ratio of the fan rotor 9 while increasing the power extracted by the low-pressure turbine 8. Indeed, the overall efficiency of the propulsion system 1 is primarily determined by the propulsion efficiency, which is favorably influenced by minimizing the variation in the kinetic energy of the air as it passes through the propulsion system 1. In a propulsion system 1 with a rate With high dilution, the majority of the flow generating the propulsive force is made up of the secondary airflow F2 of the propulsion system 1, the kinetic energy of the secondary airflow F2 being mainly affected by the compression which the secondary airflow F2 undergoes when passing through the blower section 2. The propulsive efficiency and the pressure ratio of the blower section 2 are therefore linked: the lower the pressure ratio of the blower section 2, the better the propulsive efficiency. In order to improve the propulsive efficiency of the propulsion system 1, the blower pressure ratio, which corresponds to the ratio between the average pressure at the outlet of the blower stator 16 (or, in the absence of a stator 16, of the blower rotor 9) and the average pressure at the inlet of the blower rotor 9, is less than or equal to 1.70, preferably less than or equal to 1.50, for example between 0.90 and 1.45.The average pressures are measured here over the height of at least one of the fan blades 14, that is to say from the surface which radially delimits inside the airflow duct at the inlet of the fan rotor 9 to the top 21 of the fan blade 14. .

[0190] The peripheral velocity at the tip 21 of the fan blades 14 can also be between 260 meters per second (m / s) and 400 meters per second (m / s) inclusive. The fan pressure ratio can then be between 1.20 and 1.45.

[0191] In a direct-drive propulsion system 1, the fan rotor 9 can alternatively be directly coupled to the low-pressure shaft 11, i.e., without a reduction mechanism. The low-pressure shaft 11 is then combined with the fan shaft 20 so that the fan rotor 9 is driven by the low-pressure shaft 11 at the same rotational speed as the rotor 81 of the low-pressure turbine 8.

[0192] The propulsion system 1 is configured to provide a thrust of between 18,000 Ibf (80,068 N) and 70,000 Ibf (331,374 N), preferably between 20,000 Ibf (88,964 N) and 51,000 Ibf (226,859 N), or even between 20,000 Ibf (88,964 N) and 35,000 Ibf (155,688 N).

[0193] Thrust is measured when the propulsion system 1 is stationary, uninstalled, in takeoff mode in a standard atmosphere (as defined by the International Civil Aviation Organization (ICAO) Manual, Doc 7488 / 3, 3rd edition) and at sea level. "Uninstalled" here means that the measurements are taken when the propulsion system 1 is in a test stand (and not installed on an aircraft 100), as the measurements are then simpler to perform. Unenclosed fan

[0194] Figure 3 schematically represents, in partial view and in section, a second example of a propulsion system 1.

[0195] In [Fig.3], the components are identical or similar to those of the propulsion system of [Fig.2] are designated by identical references.

[0196] In the example illustrated in [Fig. 3], the propulsion system 1 is a twin-shaft gas turbine engine with an unducted fan. It may be an "Open Rotor" or "Unducted Single Fan" type gas turbine engine.

[0197] Unlike the first example in [Fig. 2], the blower rotor 9, which can also be referred to as the "propeller," is not surrounded by a blower housing. In this case, the blower section does not include an external platform.

[0198] Since the fan section 2 is unfaired, the fan blades 14 have variable pitch. Thus, each fan blade 14 is pivotally mounted about a pitch axis relative to the fan hub 13 and is connected to a pitch-changing mechanism 15 mounted in the propulsion system 1. The pitch-changing mechanism allows the pitch angle of the fan blades 14 to be adjusted according to the flight phases. Similarly, the outlet blades 17 have variable pitch, the base of the outlet blades 17 being pivotally mounted about a pitch axis and connected to a pitch-changing mechanism 15, the pitch being adjusted according to the flight phases by the pitch-changing mechanism.

[0199] Alternatively, the propulsion system 1 could comprise two unducted, counter-rotating fan rotors 9. Such a propulsion system 1 is known, in Anglo-Saxon terminology, by the acronym "CROR" for "Contra-Rotating Open Rotor" or "UDF" for "Unducted Double Fan". The fan rotors 9 can be positioned at the rear of the primary body 3 so as to be of the pusher type or at the front of the primary body 3 so as to be of the puller type.

[0200] The absence of a fairing around the fan rotor 9 allows for a significant increase in the bypass ratio without the propulsion system 1 being negatively impacted by the mass of the housings 12 (or nacelles) intended to surround the fan section 2. The bypass ratio of the propulsion system 1, including an unfaired fan section 2, is thus greater than or equal to 40, for example, between 40 and 80 inclusive. The peripheral velocity at the tip 21 of the fan blades 14 of the fan rotor(s) 9 can also be between 210 meters per second (m / s) and 260 meters per second (m / s) inclusive. The fan pressure ratio can then preferably be between 0.90 and 1.20 inclusive.

[0201] When the rotor 9 is unshod, the diameter D of the blower rotor 9 may be between 80 inches (203.2 cm) and 185 inches (469.9 cm) inclusive. The diameter D is preferably greater than or equal to 100 inches (254 cm), for example between 120 inches (304.8 cm) and 156 inches (396.2 cm). The diameter of the blower rotor 9 is measured here in a plane normal to the longitudinal axis X, which is the axis of rotation of the blower rotor 9, at the intersection between a vertex 21 and a leading edge 22 of the blower blades 14.

[0202] It should be noted that, since [Fig.2] and [Fig.3] are partial views, the diameter D is only partially visible. Reduction mechanism

[0203] The reduction mechanism 19 may include an epicycloidal or planetary reduction mechanism, single-stage or two-stage.

[0204] For example, [Fig. 4] illustrates a planetary (or "star") type reduction mechanism 19. The reduction mechanism 19 comprises a sun pinion 19a (input of the reduction mechanism 19), centered on an axis of rotation of the reduction mechanism 19 generally coincident with the longitudinal axis X and configured to be driven in rotation by the low-pressure shaft 11, a ring gear 19b (output of the reduction mechanism 19) coaxial with the sun pinion 19a and configured to drive the blower shaft 20 in rotation about its axis X of rotation, and a series of satellites 19c distributed circumferentially around the axis X of rotation of the rotor 9 of the blower section 2, between the sun pinion 19a and the ring gear 19b, each satellite gear 19c being internally meshed with the sun pinion 19a and externally with the ring gear 19b.The series of satellites 19c is mounted on a satellite carrier 19d which is fixed relative to a stator part 19e of the propulsion system 1, for example relative to a housing of the compressor section 4, 5.

[0205] In another example, [Fig.5] illustrates an epicycloidal (or "planetary" in English) type reduction mechanism 19, in which case the ring 19b is fixedly mounted on the stator part 19e of the propulsion system 1 and the blower shaft 20 is driven in rotation by the planet carrier 19d.

[0206] Regardless of the configuration of the reduction mechanism 19, the diameter of the ring gear 19b and the planet carrier 19d are greater than the diameter of the solar pinion 19a, so that the rotational speed of the rotor 9 of the blower section 2 is less than the rotational speed of the low pressure shaft 11.

[0207] Regardless of the configuration of the reduction mechanism 19, the diameter of the ring gear 19b and the planet carrier 19d are greater than the diameter of the solar pinion 19a, so that the rotational speed of the rotor 9 of the blower section 2 is less than the rotational speed of the low pressure shaft 11.

[0208] The reduction ratio of the reduction mechanism 19 is greater than or equal to 2.5 and less than or equal to 11. The reduction ratio may be greater than or equal to 2.7 and less than or equal to 3.5, typically around 3.0. Solidity

[0209] In order to further optimize the performance of the propulsion system 1, a strength of the blower rotor 9 can be greater than or equal to 0.9 and less than or equal to 1.3. The strength is equal to the ratio between the direct chord at the tip of the blade 39 and an inter-blade pitch 23.The blade pitch 23 corresponds to the angular distance between the upstream intersection points PI and P2 of two adjacent blades 14, i.e., the distance along the circumferential axis 0 from point PI to point P2; the blade pitch 23 is therefore equal to the external radius Re of the fan rotor 9 (half-diameter) multiplied by the angle between a first straight line D1, lying in a plane normal to the X-axis, which originates from the upstream intersection point PI (see figures 11 and 12) of a first blade 14 and intersects the X-axis, and a second straight line D2, lying in the plane normal to the X-axis, which originates from the upstream intersection point P2 of a second blade 14 immediately adjacent to the first blade 14 and intersects the X-axis. Since strength is a ratio of distances, it is measured when the propulsion system 1 is cold.

[0210] The fan rotor 9 may also have a hub-to-head ratio of between 0.22 and 0.32. In the case of a fan rotor with fixed pitch, the hub-to-head ratio may be between 0.24 and 0.32. In the case of a fan rotor with variable pitch, the hub-to-head ratio is preferably between 0.24 and 0.32 in order to allow the integration of the pitch change mechanism 15. The hub-to-head ratio corresponds to the ratio between the internal radius Ri and the external radius Re of the fan rotor 9. The internal radius Ri corresponds to the distance between the axis of rotation X and the point of intersection between the leading edge 14a and the inner platform 34 at the inlet of the fan rotor 9 (and corresponds to the point of connection of the leading edge 14a with the aerodynamic surface of a platform of the fan rotor 9).The external radius Re corresponds to the distance between the axis of rotation X and the point of intersection between the leading edge 14a and the blade tip 21 (and corresponds to half the fan diameter D). The lower the hub-to-head ratio, the more efficient the fan rotor 9. However, decreasing the hub-to-head ratio of the fan rotor 9 implies an increase in the mechanical load on the hub 13 of the fan rotor 9.

[0211] In a first option, the strength can be greater than or equal to 1.0 and less than or equal to 1.3. This first option is particularly suitable for a rotor 9 comprising twenty-two blades 14. In a propulsion system 1 with a reduction mechanism 19, the rotational speed of the blower rotor 9 is reduced, for example, to between 260 m / s and 400 m / s. Its pressure ratio can also be reduced and is, for example, between 1.05 and 1.5, or even between 1.1 and 1.45, so that the velocity difference between the outlet of the blower rotor 9 and the inlet of the blower rotor 9 is reduced while optimizing the efficiency of the blower section 2. The flow The supersonic shock at the tip of the fan blade 14, passing through the fan rotor 9, is then supersonic. In particular, a supersonic shock is generated at the fan blades 14. However, this supersonic shock cannot be eliminated, especially during cruise: it must therefore be controlled to prevent it from degrading the efficiency of the fan section 2. By dimensioning and manufacturing the fan rotor 9 with twenty-two blades such that its strength is greater than or equal to 1.0 and less than or equal to 1.3, the inter-blade pitch 23 and the direct chord at the tip of the fan blade 39 are such that the supersonic shock is stable at maximum permissible speed and propagates only in the divergent part of the inter-blade channel.The inter-blade channel corresponds to the passage between two adjacent blades 14, extending from an inlet plane, which is normal to the airflow F at the inlet of the fan rotor 9 and passes through the leading edge 14a of the first blade 14, to an outlet plane, which is parallel to the inlet plane and passes through the trailing edge 14b of the second blade 14. This channel has, from upstream to downstream through the fan rotor 9, a convergent section, which extends from the inlet plane to an intermediate plane corresponding to the minimum cross-section of the channel, and a divergent section, which extends from the intermediate plane to the outlet plane. The Applicant has observed that when the supersonic shock reaches the convergent section of the inter-blade channel 24, it becomes unstable and reduces the efficiency of the fan section 2.Conversely, when the supersonic shock remains in the diverging section, for example, near the intermediate plane, the supersonic shock is stable at maximum permissible speed. The longer the inter-blade channel, that is, the greater the distance between the inlet and outlet planes, the easier it is to design a convergent-divergent channel and thus maintain the supersonic shock in the diverging section of the channel. However, increasing the length of the inter-blade channel results in an increased direct chord at the blade tip 39, and therefore an increase in the mass of the fan rotor 9 (and consequently the specific fuel consumption of the propulsion system 1) and a reduction in the efficiency of the fan section 2. It should be noted in particular that the length of the inter-blade channel and the direct chord are related to the inter-blade pitch by the strength of the fan rotor 9.For a 9-bladed fan rotor with twenty-two blades, a strength between 1.0 and 1.3 is then a good compromise between the length of the inter-blade channel 24 in order to control the supersonic shock in the fan rotor 9 and the efficiency of the fan section 2.

[0212] In a second option, the strength can be strictly less than 1.0. This second option is particularly suitable for a fan rotor 9 comprising between seventeen and twenty blades 14. Indeed, the direct chord at the blade tip 39 is then reduced relative to the available space (high inter-blade pitch 23), which makes it possible to reduce the mass of the blade 14 and modify its frequency placement, Because modifying the direct chord at the tip of blade 39 has a significant impact on the first deformation mode of blade 14 (at the same operating range). Indeed, when the deformation mode of the blades 14 occurs in a stabilized operating regime of the fan rotor 9 (in particular, the maximum permissible regime), one solution could be to increase the thickness of the blade root to improve margins and shift this deformation mode. However, increasing the thickness of the blades 14 at the root implies increasing the overall size of the root, which influences the circumferential dimensions of the recesses that receive the root and therefore the design for managing the mechanical resistance of the disc. Increasing the thickness of the blades 14 is thus likely to increase the hub-to-head ratio of the fan rotor 9. However, increasing the hub-to-head ratio negatively impacts the aerodynamic efficiency of the fan rotor 9.On the contrary, dimensioning the blower rotor 9 so that its strength is less than 1.0 makes it possible to reduce the direct chord at the tip of the blade 39 and to move the first mode of deformation of the blades 14 into an unstabilized operating range or outside the operating range of the blower rotor, without thickening the blades 14. It is therefore not necessary to increase the hub-to-head ratio.

[0213] The distances (length, radius, diameter, etc.) are measured at ambient temperature (approximately 20°C) when the propulsion system 1 is cold, i.e. when the propulsion system 1 has been stopped for a sufficient period for the parts of the propulsion system 1 to be at ambient temperature, it being understood that these dimensions vary little with respect to the conditions in which the propulsion system 1 is in takeoff mode. Example of a completed project

[0214] We now present two examples of the realization of a propulsion system, each comprising a blower section.

[0215] Common to both examples, the propulsion system 1 is a twin-shaft gas turbine engine with a shrouded fan. The fan rotor comprises 18 composite material blades that are fixed relative to the fan hub.

[0216] The blower rotor 9 has a hub-to-head ratio of 0.27

[0217] The blower section includes a blower stator fixedly mounted on the housing of blower. The blower stator comprises 40 fixed blades which are fixed relative to the blower housing.

[0218] The low pressure shaft and the high pressure shaft are co-rotating.

[0219] The propulsion system includes a two-stage high-pressure turbine.

[0220] The high-pressure compressor comprises 10 stages.

[0221] The low pressure turbine comprises 6 stages.

[0222] The low pressure compressor comprises 3 stages.

[0223] The propulsion system has a dilution ratio equal to 10

[0224] The propulsion system provides a thrust of 120,000 N

[0225] The diameter of the blower rotor is 1.98 m. In the first example, the motor does not meet the requirements for blades made with an improved composite material to achieve acceptable vibration behavior. The fan blade of this engine must therefore be made with a standard composite material.

[0226] In the second example, the engine meets the conditions requiring blades made of an improved composite material to achieve acceptable vibration behavior. If a standard composite material is used, the blade frequency response will not be acceptable.

[0227] Between the two examples, the increase in rotational speed allowed makes it possible to reduce the aerodynamic load of the fan rotor and therefore to improve its efficiency, thus allowing a reduction in specific consumption. First Example Second Example D Fan rotor diameter 198.12 cm (78 inches) 198.12 cm (78 inches) Xn Maximum permissible speed 387 rad / s 448 rad / s Ue Blade tip speed 383 m / s 444 m / s Cxm Mean axial chord 215.5 mm 215.5 mm Cx0% Axial chord at blade root 277 mm 277 mm Cxl00% Axial chord at blade tip 154 ​​mm 154 mm RE Outer radius of fan rotor 0.99 m 0.99 m RI Inner radius of fan rotor 0.265 m 0.265 mh Blade height 0.725 m 0.725 m Pci First axial chord parameter 0.7353 0.7353 Pvl First speed parameter 0.66 0.783 Pc2 second axial chord parameter 53.24 53.24 Pv2 second velocity parameter 39.025 56.1

[0228] According to this table, the inequality Pvl> Pci is respected in the case of the second example but not in the case of the first example and the inequality Pv2> Pc2 is respected in the case of the second example but not in the case of the first example.

Claims

Demands

1. Fan section (2) of an aeronautical propulsion system (1), the fan section (2) comprising: - an inner platform (34), - a fan rotor (9) comprising a blade (14), the blade (14) comprising a blade and a blade root (25) fixed to the fan rotor (9), the blade extending over a blade height (47) radially outward from an axis (X) of the propulsion system (1) from an internal radial limit (37) located at the interface of the inner platform (34) to a blade tip (21), the blade (14) comprising a leading edge (14a) and a trailing edge (14b), the blade (14) comprising a composite material structure comprising a fibrous reinforcement obtained by three-dimensional weaving of weft strands (53) and warp strands (54) and a matrix in which is embedded in the fibrous reinforcement, the blade (14) presents: a lower portion (55) including the leaf spring foot (25), an upper portion (57) including the leaf spring apex (21), an upstream portion (75) including the leading edge (14b) and a downstream portion (77) including the trailing edge (14a), the leaf spring (14) having: - an axial chord at the base of the blade extending along an axis (X) from the blower of the leading edge (14a) to the trailing edge (14b), - an axial chord at the apex of the blade extending along the axis (X) from the leading edge (14a) to the trailing edge (14b), and - an average axial chord equal to the average between the axial chord at the base of the blade and the axial chord at the tip of the blade, in which dawn (14) presents: - a first axial chord parameter corresponding to a ratio of a product of the average axial chord by the axial chord at the base of the blade to a product of the square of the blade height (47) by the axial chord at the tip of the blade,

2. - a first speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor (9) expressed in rad / s by the value 2.047x103 s / rad and the value 1.3403x10 - a second axial chord parameter corresponding to a ratio of the axial chord at the blade root to a product of the square of the average axial chord by the blade height (47) and by the axial chord at the blade tip, and - a second speed parameter corresponding to a difference of a product of the maximum permissible speed of the blower rotor (9) expressed in rad / s by the value 2.757x10 1 s / rad and the value 67.4, the blower section being configured so that the blower rotor has a maximum permissible speed greater than or equal to 280 rad / s, the vane (14) being configured such that the first axial chord parameter is less than or equal to the first velocity parameter and a stiffness of the lower portion (55) is greater than a stiffness of the upper portion (57), and / or the second axial chord parameter is less than or equal to the second velocity parameter and a stiffness of the upstream portion (75) is greater than a stiffness of the downstream portion (77). Blower section (2) according to claim 1, wherein the blade (14) has: - a third speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor (9) expressed in rad / s by the value 1.41x103 s / rad and the value 9.52x10 ', - a fourth speed parameter corresponding to a difference of a product of the maximum permissible speed of the blower rotor (9) expressed in rad / s by the value 2.067x10 1 s / rad and the value 50.5, the blade (14) being configured so that the first axial chord parameter is greater than or equal to the third velocity parameter, and / or the second axial chord parameter being greater than the fourth velocity parameter.

3.

4. A fan section (2) according to any one of claims 1 and 2, wherein the first axial chord parameter is less than or equal to the first velocity parameter and a stiffness of the lower portion (55) is greater than a stiffness of the upper portion (57), the fan section comprising an intermediate portion (58) extending from the lower portion (55) to the upper portion (57), the lower portion (55) extending from the internal radial limit (37) to the blade tip (57) to the intermediate portion (58) over a height greater than or equal to 15% and less than or equal to 25% of the blade height, the intermediate portion (58) extending over a height greater than or equal to 5% and less than or equal to 30% of the blade height, the weft strands (53) comprising first weft strands and second weft strands, the lower portion (55) comprising first weft strands and no second weft strand,the upper portion (57) comprising second weft strands and no first weft strand, the stiffness of the first weft strands being greater than the stiffness of the second weft strands, the density of the first strands increasing progressively in the intermediate portion (58) from the lower portion (55) towards the upper portion (57), the density of the second strands increasing progressively in the intermediate portion (58) from the upper portion (57) towards the lower portion (55). A fan section (2) according to any one of claims 1 to 3, wherein the second axial chord parameter is less than or equal to the second velocity parameter and a stiffness of the upstream portion (75) is greater than a stiffness of the downstream portion (77), the fan blade (14) having at each blade height a direct chord extending from the leading edge (14a) to the trailing edge (14b), the fan section comprising a central portion (78) extending from the upstream portion (75) to the downstream portion (77), the upstream portion (75) extending from the leading edge (14a) to the trailing edge (14b) to the central portion (78) over a length greater than or equal to 25% and less than or equal to 40% of the direct chord length, the central portion (78) extending over a length greater than or equal to 5% and less than or equal to 10% of the direct rope length,the warp strands comprising first warp strands and second warp strands, the portion, upstream (75) comprising more first chain strands than second chain strands and the downstream portion (77) comprising second chain strands and no first chain strands, a stiffness of the first chain strands being greater than a stiffness of the second chain strands, a density of first strands decreasing progressively in the central portion (78) of the upstream portion (75) towards the downstream portion (77), a density of second strands increasing progressively in the central portion (58) of the upstream portion (75) towards the downstream portion (77).

5. Blower section (2) according to any one of claims 1 to 4, wherein a diameter (D) of the blower rotor (9) is, when the blower is shrouded, greater than or equal to 177.8 cm and less than or equal to 304.8 cm, in particular greater than or equal to 213.36 cm and less than or equal to 266.7 cm and preferably greater than or equal to 215.9 cm and less than or equal to 266.7 cm, and, when the blower is unshrouded, greater than or equal to 203.2 cm and less than or equal to 469.9 cm, in particular greater than or equal to 254 cm and less than or equal to 469.9 cm, and preferably greater than or equal to 304.8 cm and less than or equal to 396.2 cm.

6. Blower section (2) according to any one of claims 1 to 5, the blade (14) being a first blade of a plurality of blades included in the blower rotor (9), a number of the plurality of blades being greater than or equal to 16 and less than or equal to 22.

7. Blower section (2) according to any one of claims 1 to 6, wherein the blower rotor (2) comprises a blower hub (13), each blade (14) being pivotally mounted relative to the blower hub (13) so as to have variable pitch.

8. Fan section (2) according to any one of claims 1 to 7, wherein the fan blade (14) has a direct chord at blade tip (39) extending from the leading edge (14a) to the trailing edge (14b) along the blade tip (21), the axial chord at blade tip being a projection along the X-axis of the direct chord at blade tip, the fan rotor (9) having a strength greater than or equal to 0.9 and less than or equal to 1.3, preferably greater than or equal to 1.0 and less than or equal to 1.3, where the strength is equal to a ratio between the direct chord at blade tip and an inter-blade pitch (23) at blade tip.

9. Fan section (2) according to any one of claims 1 or 7, wherein the fan blade (14) has a direct chord at blade tip (39) extending from the leading edge (14a) to the trailing edge (14b) along the blade tip (21), the axial chord at blade tip being a projection along the X-axis of the direct chord at blade tip, the fan rotor (9) having a strength strictly less than 1.0, where the strength is equal to a ratio between the direct chord at blade tip (39) and an inter-blade pitch (23) at blade tip.

10. Aeronautical propulsion system (1) comprising: - a drive shaft (11) movable in rotation about an axis (X); - a fan shaft (20); - a fan section (2) according to any one of claims 1 to 9, the fan rotor (9) being driven in rotation by the fan shaft (20); and - a reduction mechanism (19) coupling the drive shaft (11) and the fan shaft (20) in order to drive the fan shaft (20) at a rotational speed lower than the rotational speed of the drive shaft (11).

11. Propulsion system (1) according to claim 10, configured to provide a thrust of between 80,068 N and 331,374 N, preferably between 88,964 N and 155,688 N.

12. Propulsion system (1) according to any one of claims 10 and 11, wherein a dilution ratio of the propulsion system (1) is greater than or equal to 10, when the fan section is shrouded the dilution ratio is preferably greater than or equal to 10 and less than or equal to 35 or greater than or equal to 10 and less than or equal to 18, and when the fan section is unshrouded the dilution ratio is greater than or equal to 40 and less than or equal to 80.

13. Propulsion system (1) according to any one of claims 10 to 12, wherein the blower rotor (9) has a hub-to-head ratio greater than or equal to 0.22 and less than or equal to 0.

32.

14. Method for dimensioning a fan section (2) of an aeronautical propulsion system (1), the fan section (2) comprising: - an internal platform (34), - a fan rotor (9) comprising a blade (14) comprising a blade and a blade root (25) fixed to the fan rotor (9), the blade extending radially outwards over a blade height (47) relative to an axis (X) of the propulsion system (1) from an internal radial limit (37) located at the interface of the inner platform (34) to a blade tip (21), the blade (14) comprising a leading edge (14a) and a trailing edge (14b), the blade (14) comprising a composite material structure comprising a fibrous reinforcement obtained by three-dimensional weaving of weft strands (53) and warp strands (54) and a matrix in which the fibrous reinforcement is embedded, the blade (14) having: a lower portion (55) including the leaf spring foot (25), an upper portion (57) including the leaf spring apex (21), an upstream portion (75) including the leading edge (14b) and a downstream portion (77) including the trailing edge (14a), the leaf spring (14) having: - an axial chord at the base of the blade extending along an axis (X) from the blower of the leading edge (14a) to the trailing edge (14b), - an axial chord at the apex of the blade extending along the axis (X) from the leading edge (14a) to the trailing edge (14b), and - an average axial chord equal to the average between the axial chord at the base of the blade and the axial chord at the tip of the blade, in which dawn (14) presents: - a first axial chord parameter corresponding to a ratio of a product of the average axial chord by the axial chord at the blade root to a product of the square of the blade height (47) by the axial chord at the blade tip, - a first speed parameter corresponding to a difference of a product of a maximum permissible speed of the blower rotor (9) expressed in rad / s by the value 2.047x103 s / rad and the value 1.3403x10 ', - a second axial chord parameter corresponding to a ratio of the axial chord at the blade root to a product of the square of the average axial chord by the blade height (47) and by the axial chord at the blade tip, and - a second speed parameter corresponding to a difference of a product of the maximum permissible speed of the fan rotor (9) expressed in rad / s by the value 2.757x10 1 s / rad and the value 67.414, the fan section being configured so that the fan rotor has a maximum permissible speed greater than or equal to 280 rad / s, the process comprising a step of dimensioning the fan section (2) such that the first axial chord parameter is less than or equal to the first speed parameter and a stiffness of the lower portion (55) is greater than a stiffness of the upper portion (57),and / or the second axial chord parameter is less than or equal to the second velocity parameter and the stiffness of the upstream portion (75) is greater than the stiffness of the downstream portion (77).

15. Method of manufacturing a fan section (2) of an aeronautical propulsion system (1) comprising dimensioning the fan section according to claim 14 and manufacturing the fan section.

Images