Blade for a fan of a turbomachine, notably of the unducted fan type, corresponding fan and corresponding turbomachine

Abstract

A blade for a fan of a turbomachine, for example of unducted fan type, a corresponding fan, and a corresponding turbomachine. The blade includes a mechanism arranged, at a single location, to locally, as the fan rotates, disturb a distribution of flow around the blade so as to form two independent main vortices downstream.

Claims

1. A turbomachine with an unducted fan, comprising: two coaxial and contra-rotating fans, respectively upstream and downstream, the upstream and downstream fans comprising a plurality of blades, wherein the blades of the upstream fan comprise means arranged, at a single location, to locally disturb, as the upstream fan rotates, distribution of flow around the blade, to form two independent main vortices downstream, wherein the means consists of a single protuberance formed on a leading edge of the blade, and which is defined by a span position h such that 0.75 H<h<0.85 H, H being a height of the blade.

2. The turbomachine as claimed in claim 1, wherein the single protuberance is defined by its span height d such that 0.05 H<d<0.2 H, H being the height of the blade.

3. The turbomachine as claimed in claim 1, wherein the single protuberance is defined by a chord width l such that c/16<l<c/8, c being a length of a local chord of the blade at the span position h of the single protuberance.

4. The turbomachine as claimed in claim 1, further comprising a notch formed in the leading edge of the blade and which is adjacent to the single protuberance.

5. The turbomachine as claimed in claim 1, wherein a trailing edge of the blades of the upstream fan is free of any protuberance or concavity.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The figures of the attached drawing will give a good understanding as to how the invention can be produced. In these figures, identical references designate similar elements.

(2) FIG. 1 is a schematic view in longitudinal cross section of a turbomachine with unducted fan equipped with upstream blades according to an embodiment conforming to the invention.

(3) FIG. 2 is an enlarged schematic view in elevation of an upstream blade of FIG. 1.

(4) FIGS. 3 to 5, similar to FIG. 2, represent three variant embodiments of the upstream blade of FIG. 2, conforming to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows, schematically, a turbomachine with unducted fan 1, conforming to the invention, which comprises, from upstream to downstream, in the direction of flow of the gases (symbolized by the arrow F) inside the turbomachine of longitudinal axis L-L, a compressor 2, an annular combustion chamber 3, a high-pressure turbine 4 and two low-pressure turbines 5 and 6 which are contra-rotating, that is to say that they rotate in two opposite directions about the longitudinal axis L-L.

(6) Each of the low-pressure turbines 5 and 6 is secured in rotation to an outer fan 7, 8 extending radially outside the nacelle 9 of the turbomachine 1, the nacelle 9 being substantially cylindrical and extending along the axis L-L around the compressor 2, the combustion chamber 3 and the turbines 4, 5 and 6. The combustion gases outgoing from the turbines are expelled through a nozzle 10 to increase the thrust.

(7) The fans 7 and 8 are arranged coaxially one behind the other and comprise a plurality of blades 11A and 11B which are distributed equi-angularly about the longitudinal axis L-L. The blades 11A and 11B extend substantially radially and are of the type with variable setting, that is to say that they can rotate about their longitudinal axis so as to optimize their angular position according to the desired operating conditions of the turbomachine 1. Obviously, as a variant, the blades of the fans could also be of fixed setting.

(8) Each upstream 7 or downstream 8 fan comprises a rotating hub 12, 13 supporting the blades 11A, 11B and arranged concentrically to the longitudinal axis L-L of the turbomachine 1, at right angles thereto.

(9) The upstream 11A and downstream 11B blades are each formed by a blade body 14 and a blade foot 15, mounted to rotate on the corresponding hub 12, 13.

(10) In the embodiment of FIG. 2 conforming to the invention, each blade 11A of the upstream fan 7 comprises a single protuberance 16 formed on the leading edge 17 of said blade 11A concerned.

(11) Furthermore, the single protuberance 16, of rounded form, is advantageously defined by the following parameters: its span position h, which is between 0.75 H and 0.85 H, with H being the height of the upstream blade 11A; its span height d, which is between 0.05 H and 0.2 H; and its chord width l, which is between c/16 and c/8, with c being the length of the local chord of the blade at the span position h of said protuberance 16.

(12) Thus, the single protuberance makes it possible to disturb the distribution of the flow around the upstream blade 11A, which provokes two co-rotating main vortices: a first natural vortex (or marginal vortex) being formed at the free end 18 of the upstream blade 11A; a distinct second forced vortex (or supplementary main vortex) occurring in the vicinity of the single protuberance 16.

(13) Furthermore, the single protuberance 16 also causes the formation of contra-rotating auxiliary vortices (that is to say of a direction contrary to the two marginal and supplementary vortices) which are inserted between the two co-rotating main vortices, thus preventing them from merging.

(14) In other words, as the upstream fan 7 rotates, the single protuberance 16 locally disturbs the distribution of the flow around the upstream blade 11A, so as to form two independent main vortices downstream which remain independent as far as the downstream fan 8.

(15) Moreover, FIGS. 3 to 5 show three variant embodiments of the protuberance of the upstream blade 11A, conforming to the invention.

(16) In particular, the protuberances 16A and 16B of FIGS. 3 and 4 are of respectively triangular and rectangular form. The associated parameters h, d and l are similar to those of the protuberance 16 of FIG. 2.

(17) Furthermore, in another variant conforming to the invention, as shown in FIG. 5, a notch 19 formed in the leading edge 17 of the upstream blade 11A is associated with the protuberance 16. The notch 19, which is adjacent to the protuberance 16, is arranged between the latter and the free end 18 of the upstream blade 11A. As a variant, it would be possible to envisage having the protuberance arranged between the notch and the free end of the upstream blade.