PROPULSION SYSTEM

Abstract

Propulsion system (10) comprising: - a streamlined body (12) elongated along an axis (A) and comprising at least one upstream end section (18) having an external annular surface (18a) centered on the axis (A) and converging upstream, and a downstream end section (22) having an external annular surface (22a) centered on the axis (A) and converging downstream, - a propulsion propeller (14) mounted on the body (12) and rotatable about the axis (A), and - blades (30, 30') mounted on the body (12) downstream of the propeller (14) and extending radially outwards from at least one of said sections (22). Figure 2

Description

Title of the invention: PROPULSION SYSTEM Technical field of the invention

[0001] The present invention relates to a propulsion system, for example aeronautical or naval. Technical Downstream Plan

[0002] In this application, the term propulsion system means a system 10 as illustrated in [Fig. 1] and comprising:

[0003] - a tapered body 12 of elongated shape along an axis A, and

[0004] - a propulsion propeller 14 which is mounted on the body 12 and which is movable in rotation around axis A.

[0005] A propulsion system of this type is for example a turbomachine or aircraft electric machine, an aircraft, a naval propulsion system or a submarine.

[0006] The propeller 14 includes blades or vanes 16 which extend radially outwards from the body 12 and which generate in operation a flow of fluid F which can be air or water depending on the aeronautical or naval application of the system 10.

[0007] The tapered body 12 is for example the nacelle of an aircraft turbomachine or the fuselage of an aircraft. The tapered body 12 comprises several successive sections 18, 20, 22 along the axis A. The tapered body 12 comprises at least one upstream end section 18 having an external peripheral surface 18a, for example annular, which is centered on the axis A and converges upstream, a downstream end section 22 having an external peripheral surface 22a, for example annular, which is centered on the axis A and converges downstream, and an intermediate section 20 which is axially intercalated between the end sections 18, 20 and which comprises an external peripheral surface 20a, for example annular, centered on the axis A and defining a maximum diameter Dmax of the body 12. The external surfaces 18a, 20a, 22a of the sections 18, 20, 22 can extend continuously one after the other.Body 12 may, however, include, for example at section 18, an air intake for engine operation. Similarly, there may be an exhaust of burnt gases on body 12 downstream of propeller 14.

[0008] The terms "upstream" and "downstream" refer to the flow of fluid F around and along the propulsion system 10.

[0009] The propeller 14 produces traction and induces on the flow F an increment of axial velocity as well as an increment of tangential velocity.

[0010] Downstream of the tapered body 12 there is a zone Z (delimited by dotted lines in [Fig.1]) in which the frontal section is reduced and which results in a slowing of the flow and a recompression.

[0011] However, due to the rotation of the flow F by the propeller 14 (tangential speed), whether it is installed on a nacelle or a fuselage, this zone Z in which the flow should undergo recompression sees, on the contrary, in some cases a significant decrease in local pressure, all the more so as the tangential component of the flow speed in the wake of the propeller 14 is greater than its axial component.

[0012] Given the shape of the body 12 in this zone Z, a pressure lower than the ambient pressure results in a force that opposes the advancement of the system (drag).

[0013] It follows that the drag of the streamlined body 12, that is to say the integration over its surface of the forces exerted on it, equipped with the propeller 14 can increase significantly with the increase in the traction of the propeller 14, thus degrading the overall propulsive efficiency.

[0014] One solution to this problem, using current technology, is to design the propeller 14 so that it generates very little tangential velocity at the outlet. However, this is an extremely significant constraint that risks severely penalizing the performance of the propulsion system 10, particularly during flight phases such as takeoff for an aeronautical system.

[0015] Another solution to solve this problem in current technology is to place rectifiers (stators) or a second helix in the opposite direction of rotation to the first, directly downstream of the first helix 14. These are architectures of the type USF (Unducted Single Fan) or CROR (acronym for Contra Rotative Open Rotor) for example.

[0016] In the case of rectifiers as in the case of a second helix, their external diameter is equivalent to or slightly less (up to about -15%) than that of the first helix 14.

[0017] In the case of a second helix, it produces traction and straightens the flow F. This is also the case with straighteners which transform all or part of the tangential velocity into axial velocity, even if the traction generated is weaker.

[0018] However, in order to adapt to the different operating regimes of the first propeller 14 and to the aircraft's forward speed, for example, these stators or this second propeller must be steerable, that is, have variable angular pitch. Such a mechanism adds complexity, mass, and a source of noise.

[0019] Moreover, in the event of failure of the propulsion system 10, these straighteners or this second propeller are no longer of use and instead represent a significant additional drag.

[0020] The present invention proposes a solution to at least some of the problems of the prior art, which is simple, effective and economical. Summary of the invention

[0021] The invention relates to a propulsion system comprising:

[0022] - a tapered body with an elongated shape along an axis and comprising at least one an upstream end segment comprising an external annular surface centered on the axis and converging upstream, a downstream end segment comprising an external annular surface centered on the axis and converging downstream, and an intermediate segment axially intercalated between the end segments comprising an external annular surface centered on the axis and defining a maximum body diameter, the external surfaces of the segments extending continuously one after the other, and

[0023] - a propulsion propeller which is mounted on the body and which is rotatable around the axis, this propulsion propeller includes blades or vanes that extend radially outwards from the body.

[0024] The propulsion system further comprises blades which are mounted on the body downstream of the propeller and which extend radially outwards from at least one of said sections, such as the downstream end section. These blades are preferably at least four in number and distributed, preferably regularly, around the axis.

[0025] The maximum external diameter of the fins preferably represents at most 50% of the maximum external diameter of the propulsion propeller.

[0026] The fins can be rotor fins or stator fins.

[0027] The proposed technical solution thus consists of locally introducing fins to limit the additional drag due to the combination of a rotating flow and a decreasing frontal area. The fins are arranged around the periphery of the streamlined body, downstream of the propeller, so as to straighten the flow set in rotation by the propeller. These fins differ from the straighteners of the prior art, for example, in their size and / or their position on the body.

[0028] The propulsion system according to the invention may comprise one or more of the following features, taken individually or in combination with each other: • the number of fins is greater than or equal to 5, preferably greater than or equal to 8 and more preferably greater than or equal to 12; • The blades have a maximum radial dimension that represents at least 10%, preferably at least 20%, and more preferably at least 30% of a maximum radial dimension of the blades or vanes, each dimension maximum radial being measured with respect to the axis and from the corresponding external surface; • the fins have a maximum external diameter which represents at least 20%, preferably at least 30%, and more preferably at least 40% of a maximum external diameter of the propulsion propeller; • the maximum external diameter of the fins represents at most 30% of the maximum external diameter of the propulsion propeller; • the fins have a maximum axial dimension measured along the axis which represents at least 20%, preferably at least 30%, and more preferably at least 50% of a maximum axial dimension of the propulsion propeller, each maximum axial dimension being measured from the upstreammost point of a leading edge of a fin or of a blade or propeller blade to the downstreammost point of a trailing edge of that fin or of that blade or propeller blade; • the maximum axial dimension of the fins represents at least 100%, preferably at least 200%, and more preferably at least 300% of the maximum axial dimension of the propulsion propeller; • the stator fins extend radially outwards from the upstream or downstream end section; • the stator fins extend radially outwards also from the intermediate section; • the propulsion propeller extends radially outwards from the upstream end section, or from the downstream end section; • the propulsion propeller extends radially outwards from the intermediate section;

[0029] — the propulsion propeller extends radially outwards from the sections upstream and intermediate; • the propulsion propeller is not shrouded; • The propulsion propeller is enclosed by an annular casing that extends around of the axis and the body and which is connected to the body by radial arms; • the annular casing extends only around the upstream end section and / or the intermediate section;

[0030] — the annular casing extends only around the downstream end section; • the system is chosen from an aircraft turbomachine, an aircraft, or a boat or ship propulsion system; • the fins are not faired;

[0031] — the fins are all identical; alternatively, the fins could be different;

[0032] — the fins have variable pitch;

[0033] — the fins are movable from a stowed position, for example in the or along of the body, up to a deployed position and are therefore of the retractable type;

[0034] — the fins are distributed in a single annular row or in two or more annular rows around the axis;

[0035] — the blades can be one piece with the propeller except when they are of the type with variable calibration;

[0036] — the fins comprise upstream ends which are located in the same plane perpendicular to the axis; - the fins have different axial dimensions along the axis and have downstream ends located in the same plane perpendicular to the axis, and upstream ends which are not located in the same other plane perpendicular to the axis; - the blades have radial dimensions which vary along the axis and are close to zero at their upstream ends to be flush with the external surface of the corresponding section; this helps to limit the risk of damage to the blades by impact (ice, debris, bird, etc.); this limits the acoustic impact of the blades because the propeller wake does not directly impact the upstream ends (leading edges) of the blades; - the fins have an external diameter that decreases continuously from the upstream ends of the fins to their downstream ends; - the fins have an external diameter that is constant between the upstream and downstream ends of the fins; - the fins each have a circumferential thickness which is maximum at the radially inner end of the fin;

[0037] — the fins each have a circumferential thickness which is constant over the entire radial extent of the fin; - each of the fins has a general curved shape between its upstream end and its downstream end, the fins thus having concavities which are all oriented in circumferential or tangential directions with respect to the axis; - each of the fins has a general curved shape between its radially internal end and its radially external end, the fins thus having concavities which are all oriented in circumferential or tangential directions with respect to the axis; - the concavities are oriented in the direction of rotation of the helix around the axis; - the propulsion system further includes at least one heat exchanger which includes at least one fluid circuit, this fluid circuit being at least partly formed in at least some of the fins, and / or in the section(s) of the body containing these fins; the fins can then be used to enhance the cooling provided by the exchanger; this complicates the manufacture of the fins, but allows significant gains in heat exchanged by reducing the distance to be traveled by the heat flux by conduction in the fins; the fins are in this case preferably formed from a heat-conducting material, if possible the lightest possible such as aluminium;

[0038] — each of the fins comprises a single fluid circulation channel for said circuit of fluid;

[0039] — each of the fins comprises at least two or three circulation channels fluid of said fluid circuit;

[0040] — the fluid circuit is an oil circuit; and

[0041] — the number of fins is less than 72. Brief description of the figures

[0042] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0043] [Fig-1] [Fig.1] is a very schematic view of a propulsion system of the technique previous;

[0044] [Fig.2] [Fig.2] is a very schematic view of a propulsion system according to a first embodiment of the invention;

[0045] [Fig.3] [Fig.3] is another very schematic view of the propulsion system of [Fig.2];

[0046] [Fig.4] [Fig.4] is a very schematic view of a propulsion system according to a second embodiment of the invention;

[0047] [Fig.5] [Fig.5] is a very schematic view of a propulsion system according to a third embodiment of the invention;

[0048] [Fig.6] [Fig.6] is a very schematic view of a propulsion system according to a fourth embodiment of the invention;

[0049] [Fig.7] [Fig.7] is a very schematic view of a propulsion system according to a fifth embodiment of the invention;

[0050] [Fig.8] [Fig.8] is a very schematic view of a propulsion system according to a sixth embodiment of the invention;

[0051] [Fig.9] [Fig.9] is a very schematic view of a propulsion system according to a seventh embodiment of the invention.

[0052] [Fig. 10] [Fig. 10] is a very schematic view of a propulsion system according to an eighth embodiment of the invention;

[0053] [Fig. 11] [Fig. 11] is a very schematic view of a propulsion system according to a ninth embodiment of the invention;

[0054] [Fig. 12] [Fig. 12] is a very schematic view of a propulsion system according to one tenth embodiment of the invention;

[0055] [Fig. 13] [Fig. 13] is a very schematic view of a propulsion system according to an eleventh embodiment of the invention;

[0056] [Fig. 14] [Fig. 14] is a very schematic view of a propulsion system according to a twelfth embodiment of the invention;

[0057] [Fig. 15a-15b] Figures 15a and 15b are very schematic views of a system propulsive according to a thirteenth embodiment of the invention;

[0058] [Fig. 16a-16b] Figures 16a and 16b are further very schematic views of the system propulsive according to the thirteenth embodiment of the invention;

[0059] [Fig. 17a-17b] Figures 17a and 17b are very schematic views of a system propulsive according to a fourteenth embodiment of the invention;

[0060] [Fig. 18a-18b] Figures 18a and 18b are further very schematic views of the system propulsive according to the fourteenth embodiment of the invention;

[0061] [Fig. 19] [Fig. 19] is a very schematic view of a propulsion system according to a fifteenth embodiment of the invention;

[0062] [Fig.20] [Fig.20] is a very schematic view of a fin comprising a fluid circuit of an exchanger;

[0063] [Fig. 21] [Fig. 21] is a very schematic view of a fin comprising another fluid circuit of a heat exchanger; and

[0064] [Fig.22] [Fig.22] is a very schematic view of a propulsion system according to a sixteenth embodiment of the invention. Detailed description of the invention

[0065] The [Fig. 1] has been described above and illustrates the prior art of the invention.

[0066] Figures 2 to 9 illustrate several embodiments of the invention relating to a propulsion system 10 which can, for example, be selected from an aircraft turbomachine, an aircraft, or a boat or ship propulsion system. The propulsion system 10 can thus have an aeronautical or naval application.

[0067] The propulsion system 10 according to the invention comprises a streamlined body 12 and a propulsion propeller 4.

[0068] The tapered body 12 has an elongated shape along an axis A and comprises, from upstream to downstream with reference to the flow of the fluid flow F along the axis A, an upstream end section 18, an intermediate section 20 and a downstream end section 22.

[0069] The section 18 comprises an external peripheral surface 18a, preferably annular, which is centered on the axis A and which converges upstream.

[0070] The downstream end section 22 has an external peripheral surface 22a, preferably annular, which is centered on the axis A and which converges downstream.

[0071] The intermediate section 20 is axially intercalated between the end sections 18, 22 and includes an external peripheral surface 20a, preferably annular, centered on the axis A and defining a maximum external diameter Dmax of the body 12.

[0072] The external surfaces 18a, 20a, 22a of the sections 18, 20, 22 extend continuously one after the other.

[0073] The propulsion propeller 14 is mounted on the body 12 and is movable in rotation around the axis A.

[0074] The propeller 14 comprises blades or vanes 16 which extend radially outwards from the body 12.

[0075] The distinctive feature of the propulsion system 10 is that it includes stator fins 30 which are mounted on the body 12 downstream of the propeller 14.

[0076] These fins 30 extend radially outwards from at least one of the sections 18, 20, 22. There are at least four of these fins 30, and they are distributed, preferably regularly, around the axis A. Furthermore, the maximum external diameter Da of the fins 30 represents at most 50% of the maximum external diameter Dh of the propulsion propeller 14.

[0077] The number of fins 30 can be greater than or equal to 5, preferably greater than or equal to 8 and more preferably greater than or equal to 12.

[0078] The number of fins 30 is preferably less than 72.

[0079] Even when straighteners are already present downstream of the propeller 14, the presence of the fins on the downstream end section 22 is advantageous. Indeed, the design of the straighteners results from a compromise between different flight points. They cannot therefore completely straighten the flow over the entire flight envelope. It is thus advantageous to supplement them with the fins 30, which can also allow for a relaxation of constraints during the design of the straighteners.

[0080] In the first embodiment of Figures 2 and 3, the fins 30 extend radially outwards only from the downstream end section 22. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0081] The fins 30 can have a maximum radial dimension Ra which represents at least 10%, preferably at least 20%, and more preferably at least 30% of a maximum radial dimension Rh of the blades or vanes 16. Each maximum radial dimension is measured with respect to the axis A and from the corresponding external surface (i.e. from the surface 22a for the fins 30 and the surface 18a for the blades or vanes 16).

[0082] The fins 30 can have a maximum external diameter Da which represents at least 20%, preferably at least 30%, and more preferably at least 40% of a maximum external diameter Dh of the propulsion propeller 14.

[0083] This maximum external diameter Da of the fins 30 can represent at most 30 or 40% of the maximum external diameter Dh of the propulsion propeller 14.

[0084] The fins 30 may have a maximum axial dimension La measured along the axis A which represents at least 20%, preferably at least 30%, and more preferably at least 50% of a maximum axial dimension Lh of the propulsion propeller 14, each maximum axial dimension La, Lh being measured from the upstreammost point of a leading edge of a fin 30 or of a blade or vane 16 of the propeller 14 to the downstreammost point of a trailing edge of this fin 30 or of this blade or vane 16 of the propeller 14.

[0085] This maximum axial dimension La of the fins 30 can be less than or equal to 100% of the maximum axial dimension Lh of the propulsion propeller 14.

[0086] In the embodiment of [Fig. 4], the fins 30 extend radially outwards from the downstream end section 22 as well as from the intermediate section 20. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0087] The fins 30 can have a maximum radial dimension Ra and a maximum external diameter Da as described above in relation to the first embodiment of the invention.

[0088] The fins 30 can have a maximum axial dimension La measured along axis A which represents at least 100%, preferably at least 200%, and more preferably at least 300% of the maximum axial dimension Lh of a blade or vane 16 of the propeller 14.

[0089] In the embodiment of [Fig. 5], the fins 30 extend radially outwards from the downstream end section 22 only. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is faired in this version.

[0090] The propulsion propeller 14 is surrounded by an annular housing 40 which extends around the axis A and the body 12 and which is connected to the body 12 by radial arms 42. The housing annular 40 can extend only around the upstream end section 18, or both around the upstream end section 18 and the intermediate section 20.

[0091] The fins 30 can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0092] In the embodiment of [Fig. 6], the fins 30 extend radially outwards from the downstream end section 22 only. The fins 30 are unfaired. The propulsion propeller 14 is located on the downstream end section 22 and is also unfaired in this instance.

[0093] The fins 30 can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0094] The propulsion systems 10 in Figures 2 to 6 can be considered as aeronautical turbomachinery, naval propulsion systems or submarines, for example.

[0095] In the embodiment of [Fig. 7], the fins 30 extend radially outwards from the downstream end section 22 only. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is also unfaired in this instance.

[0096] The fins 30 can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0097] The propulsion system 10 of [Fig. 7] can be considered as an aircraft, that is to say, the streamlined body 12 is formed by the fuselage of the aircraft. This aircraft can be, for example, an airplane or a drone.

[0098] The propulsion system 30 may include at least one wing 50 which extends, for example, radially outwards from the axis A, from the intermediate section 20.

[0099] In the embodiment of [Fig. 8], the fins 30 extend radially outwards from the downstream end section 22 only. The fins 30 are unfaired. The propulsion propeller 14 is located on the downstream end section 22 and is also unfaired in this instance.

[0100] The fins 30 can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0101] The propulsion system 10 of [Fig. 8] can be considered as an aircraft, i.e., the streamlined body 12 is formed by the fuselage of the aircraft. This aircraft can be, for example, an airplane or a drone.

[0102] The propulsion system 30 may include at least one wing 50 which extends, for example, radially outwards from the axis A, from the intermediate section 20.

[0103] In the embodiment of [Fig. 9], the fins 30 extend radially outwards from the upstream end section 18. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0104] The fins 30 can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0105] Figures 10 and following illustrate other embodiments of the invention, the particularity of which is that the stator fins are replaced by rotor fins 30'. The rotor fins 30' are mounted on the body 12 downstream of the propeller 14.

[0106] These 30' fins extend radially outwards from at least one of the sections 18, 20, 22. There are at least four of these 30' fins, and they are distributed, preferably regularly, around the axis A. Furthermore, the maximum external diameter Da of the 30' fins represents at most 50% of the maximum external diameter Dh of the propulsion propeller 14. The number of 30' fins can be greater than or equal to 5, preferably greater than or equal to 8, and more preferably greater than or equal to 12.

[0107] In the embodiment of [Fig. 10], the fins 30' extend radially outwards from the upstream end section 18. The fins 30' are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0108] The fins 30' can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0109] The propeller 14 and the fins 30' are preferably co-rotating.

[0110] The propeller 14 and the fins 30' can form a single unit and be by example carried by the same inlet cone 51 of the propulsion assembly.

[0111] The embodiment of [Fig. 11] differs from that of [Fig. 10] in that the propulsion assembly includes an air inlet 52 offset from the longitudinal axis A of the propulsion assembly.

[0112] In the embodiment of [Fig. 12], the fins 30' extend radially outwards from the downstream end section 22 only. The fins 30' are unfaired. The propulsion propeller 14 is located on the downstream end section 22 and is here unfaired.

[0113] The fins 30' can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0114] The propeller 14 and the fins 30' are preferably co-rotating.

[0115] The propeller 14 and the fins 30' can form a single unit.

[0116] The propulsion systems 10 in Figures 10 to 12 can be considered as aeronautical turbomachinery, naval propulsion systems or submarines, for example.

[0117] In the embodiment of [Fig. 13], the fins 30' extend radially outwards from the downstream end section 22 only. The fins 30' are unfaired. The propulsion propeller 14 is located on the downstream end section 22 and is here unfaired.

[0118] The fins 30' can have a maximum radial dimension Ra, a maximum external diameter Da, and a maximum axial dimension La as described above in relation to the first embodiment.

[0119] The propulsion system 10 of [Fig. 13] can be considered as an aircraft, i.e., the streamlined body 12 is formed by the fuselage of the aircraft. This aircraft can be, for example, an airplane or a drone.

[0120] The propulsion system 10 may include at least one wing 50 which extends for example radially outwards with respect to the axis A, from the intermediate section 20.

[0121] The propeller 14 and the fins 30' are preferably co-rotating.

[0122] The propeller 14 and the fins 30' can form a single unit and be by example carried by the same outlet or exhaust cone 54 of the propulsion assembly.

[0123] In the embodiment of [Fig. 14], the fins 30' extend radially outwards from the intermediate section 20. The fins 30' are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0124] The 30' fins can have a maximum radial dimension Ra and a maximum external diameter Da as described above in relation to the first embodiment of the invention.

[0125] The 30' fins may have a maximum axial dimension La measured along axis A which represents at least 100%, preferably at least 200%, and more preferably at least 300% of the maximum axial dimension Lh of a blade or vane 16 of the propeller 14.

[0126] The propeller 14 and the fins 30' are preferably co-rotating.

[0127] The propeller 14 can be axially separated from the fins 30'.

[0128] The propulsion system 10 of [Fig. 14] can be considered as an aeronautical turbomachine, a naval propulsion system or a submarine for example.

[0129] In the embodiment shown in Figures 15a-15b and 16a-16b, the fins 30 extend radially outwards from the downstream end section 22 and also from a portion of the intermediate section 20. The fins 30 are unfaired. The propulsion propeller 14 is located on the upstream end section 18 and is unfaired.

[0130] In previous embodiments, the fins 30 include upstream ends 30a which are located in the same plane perpendicular to the axis A. This is not the case in Figures 15a-15b and 16a-16d. The fins 30 have different axial dimensions Li along the axis A and have downstream ends 30b located in the same plane P perpendicular to the axis A, and upstream ends 30a which are not located in the same other plane perpendicular to the axis A (Figure 15b).

[0131] In this variant, the fins 30 have radial dimensions Ri which vary along the axis A and which are close to zero at their upstream ends 30a to be flush with the external surface of the corresponding section 20, 22.

[0132] It can also be seen that the fins 30 have an external diameter Di which decreases continuously from the upstream ends 30a of the fins 30 to their downstream ends 30b.

[0133] Each of the fins 30 preferably has a general curved shape between its upstream end 30a and its downstream end 30b (figure 15b), the fins 30 thus having concavities Cl which are all oriented in circumferential or tangential directions with respect to the axis A.

[0134] Each of the fins 30 can have a general curved shape between its radially internal end 30c and its radially external end 30d (Figure 16b), the fins 30 thus having concavities C2 which are all oriented in circumferential or tangential directions with respect to the axis A.

[0135] The concavities Cl, C2 are oriented in the direction of rotation of the helix 14 around the axis A, which is represented by the arrow F.

[0136] In this example, the fins 30 each have a thickness Ei in the circumferential direction which is constant over the entire radial extent of the fin 30 (figure 16b).

[0137] The embodiment of figures 17a-17b and 18a-18b differs from the previous embodiment essentially in that the fins 30 have an external diameter Di which is constant between the upstream 30a and downstream 30b ends of the fins 30.

[0138] The embodiment of [Fig.19] is based on that of figures 15a-15b and 16a-16b but could be based on any other embodiment described above.

[0139] In this embodiment, the propulsion system 10 further comprises at least one heat exchanger 60 which includes at least one fluid circuit 62. This fluid circuit 62 is at least partly formed in at least some of the fins 30, and / or in the section(s) of the body 12 comprising these fins 30, as schematically represented in Figures 20 and 21.

[0140] In this case, the fins 30 serve to cool the fluid in the circuit 62, and therefore complement the cooling carried out by the exchanger 60.

[0141] It is therefore understood that the fluid circuit can be formed only in the fins 30, or only in the section(s) carrying the fins 30, or both in the section(s) and the fins 30.

[0142] The fluid circuit is, for example, an oil circuit. The heat exchanger 60 is, for example, of the ACOC type.

[0143] In the case of a heat transfer fluid circulation that does not penetrate the fins 30, the fin thickness can be optimized to maximize conductive heat transport and thus fin efficiency. For this purpose, the fin thickness can be greater at its base than at its apex.

[0144] In the case of a heat transfer fluid circulation entering the fins 30, the thickness of the fins must be sufficiently large to accommodate the circuit 62.

[0145] Each of the fins 30, or at least a portion thereof, may include a single fluid circulation channel 64 for the fluid circuit 62 ([Fig. 20]). The channel 64 may have a generally corrugated or serpentine shape within the fin 30.

[0146] In this case, the oil channels 64 arranged in the fins 30 are designed to occupy as much surface area as possible in order to maximize heat exchange. For applications where the oil pressure drop is not limiting, a single oil channel 64 can thus be arranged in each fin 30, and meander to occupy the surface of the fin.

[0147] Alternatively, each of the fins 30, or at least part of them, may include at least two or three channels 64 for fluid circulation of the fluid circuit 62 ([Fig.21]).

[0148] For applications where it is necessary to reduce the oil pressure drop, the oil circuit is distributed across several channels 64. This reduces the length of the channels 64 and increases the total cross-sectional area, thereby decreasing the pressure drop at a constant flow rate. It is thus possible to adjust the length of the different sub-circuits to homogenize the pressure drop between the different channels and thus ensure an equitable flow distribution.

[0149] The embodiment of [Fig.22] is a combination of the embodiments of [Fig.5] on the one hand, with the housing 40 and the arms 42, and that of figures 15a-15b and 16a-16b.

[0150] In variants not shown, the fins 30, 30' may have variable pitch to maximize drag reduction at different flight phases. The fins 30, 30' may be foldable so as to be deployed only in flight phases where their presence is beneficial to performance. Furthermore, the propulsion system 10 may comprise several successive rows of fins 30, 30'.

[0151] The axial and azimuthal position, the number and shape of the fins 30, 30' giving the best drag reduction are potentially different for each application case and can therefore give rise to dedicated optimization.

[0152] The invention offers several advantages, including:

[0153] - the small diameter and therefore the small wetted surface of the fins 30, 30' allows to limit the drag penalty in flight phases where propeller 14 produces little thrust or where the engine driving the propeller is out of service, and

[0154] The fact that it is not necessary to generate thrust with the 30, 30' fins to obtain a drag reduction greatly simplifies their design compared to straighteners,

[0155] - etc.

Claims

Demands

1. Propulsion system (10) comprising: - a streamlined body (12) of elongated shape along an axis (A) and comprising at least one upstream end section (18) having an external peripheral surface (18a) which is centered on the axis (A) and which converges upstream, a downstream end section (22) having an external peripheral surface (22a) which is centered on the axis (A) and which converges downstream, and an intermediate section (20) which is axially intercalated between the end sections (18, 22) and which comprises an external peripheral surface (20a) centered on the axis (A) and defining a maximum diameter (Dmax) of the body (12), the external surfaces (18a, 20a, 22a) of the sections (18, 20, 22) extending continuously one after the other, and - a propulsion propeller (14) which is mounted on the body (12) and which is mobile in rotation around the axis (A),this propulsion propeller (14) comprising blades (16) extending radially outwards from the body (12), characterized in that it comprises vanes (30, 30') mounted on the body (12) downstream of the propeller (14) and extending radially outwards from at least one of said sections (18, 20, 22), these vanes (30) being at least four in number and distributed around the axis (A), and the maximum external diameter (Da) of the vanes (30) representing at most 50% of the maximum external diameter (Dh) of the propulsion propeller (14).

2. Propulsion system (10) according to claim 1, wherein the fins (30) are stator fins.

3. Propulsion system (10) according to claim 1, wherein the fins (30') are rotor fins.

4. Propulsion system (10) according to any one of the preceding claims, wherein the number of fins (30, 30') is greater than or equal to 5, preferably greater than or equal to 8 and more preferably greater than or equal to 12.

5. Propulsion system (10) according to any one of the preceding claims, wherein the blades (30, 30') have a maximum radial dimension (Ra) which represents at least 10%, preferably at least 20%, and more preferably at least 30% of a maximum radial dimension (Rh) of the blades or vanes (16), each radial dimension maximum (Ra, Rh) being measured with respect to the axis (A) and from the corresponding external surface (18a, 20a, 22a).

6. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') have a maximum external diameter (Da) which represents at least 20%, preferably at least 30%, and more preferably at least 40% of a maximum external diameter (Dh) of the propulsion propeller (14).

7. Propulsion system (10) according to the preceding claim, wherein the maximum external diameter (Da) of the fins (30, 30') represents at most 30% of the maximum external diameter (Dh) of the propulsion propeller (14).

8. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') have a maximum axial dimension (La) measured along the axis (A) which represents at least 20%, preferably at least 30%, and more preferably at least 50% of a maximum axial dimension (Lh) of the propulsion propeller (14), each maximum axial dimension (La, Lh) being measured from a leading edge of a fin (30, 30') or of a blade (16) of the propeller (14) to a trailing edge of such fin (30, 30') or of such blade (16) of the propeller (14).

9. Propulsion system (10) according to the preceding claim, wherein the maximum axial dimension (La) of the fins (30, 30') represents at least 100%, preferably at least 200%, and more preferably at least 300% of the maximum axial dimension (Lh) of the propulsion propeller (16).

10. Propulsion system (10) according to any one of the preceding claims, wherein the stator fins (30, 30') extend radially outwards from the upstream end section (18) or downstream end section (22).

11. Propulsion system (10) according to the preceding claim, wherein the stator fins (30, 30') extend radially outwards also from the intermediate section (20).

12. Propulsion system (10) according to any one of the preceding claims, wherein the propulsion propeller (14) extends radially outwards from the upstream end section (18), or from the downstream end section (22).

13. Propulsion system (10) according to any one of claims 1 to 11, wherein the propulsion propeller (14) extends radially outwards from the intermediate section (20).

14. Propulsion system (10) according to any one of the preceding claims, wherein the propulsion propeller (14) is unfaired.

15. Propulsion system (10) according to any one of claims 1 to 13, wherein the propulsion propeller (14) is enclosed by an annular housing (40) which extends around the axis (A) and the body (12) and which is connected to the body (12) by radial arms (42).

16. Propulsion system (10) according to the preceding claim, wherein the annular housing (40) extends only around the upstream end section (18) and / or the intermediate section (20).

17. Propulsion system (10) according to any one of the preceding claims, the system being selected from an aircraft turbomachine, an aircraft, or a boat or ship propulsion system.

18. Propulsion system (10) according to the preceding claim, wherein the fins (30, 30') are unfaired.

19. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') have different axial dimensions (Li) along the axis (A) and have downstream ends (30b) located in the same plane (P) perpendicular to the axis (A), and upstream ends (30a) which are not located in the same other plane perpendicular to the axis (A).

20. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') have radial dimensions (Ri) which vary along the axis (A) and which are close to zero at their upstream ends (30a) to be flush with the external surface of the corresponding section.

21. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') have an external diameter (Di) which decreases continuously from the upstream ends (30a) of the fins (30) to their downstream ends (30b).

22. Propulsion system (10) according to any one of claims 1 to 20, wherein the fins (30, 30') have an external diameter (Di) which is constant between the upstream (30a) and downstream (30b) ends of the fins (30).

23. Propulsion system (10) according to any one of the preceding claims, wherein the fins (30, 30') each have a thickness (Ei) in circumferential direction which is maximal at the radially internal end (30c) of the fin (30).

24. Propulsion system (10) according to any one of the preceding claims, wherein each of the fins (30, 30') has a generally curved shape between its upstream end (30a) and its downstream end (30b), the fins (30) thus having concavities (Cl) which are all oriented in circumferential or tangential directions with respect to the axis (A).

25. Propulsion system (10) according to any one of the preceding claims, wherein each of the fins (30, 30') has a generally curved shape between its radially inner end (30c) and its radially outer end (30d), the fins (30) thus having concavities (C2) which are all oriented in circumferential or tangential directions with respect to the axis (A).

26. Propulsion system (10) according to claim 24 or 25, wherein the concavities (Cl, C2) are oriented in the direction of rotation of the propeller (14) around the axis (A).

27. ​​Propulsion system (10) according to any one of the preceding claims, further comprising at least one heat exchanger (60) which includes at least one fluid circuit (62), this fluid circuit (62) being at least partly formed in at least some of the fins (30), and / or in the section or sections of the body (12) comprising these fins (30).

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