Air-gap fins for a turbine engine compressor

Abstract

A vane stage with a longitudinal axis designed to be fitted in a turbine engine compressor. The van stage has an annular row of mobile vanes arranged upstream from an annular row of stator vanes. The annular row of stator vanes has a radially internal annular platform bearing radial blades, an upstream annular portion of which is arranged upstream from the blades and is surrounded radially outwards by a downstream annular portion of an annular platform of the upstream row of mobile vanes. The upstream annular portion of the annular platform of the annular row of stator vanes has a radially external annular face from which fins extend, which are distributed around the longitudinal axis and extend radially outwards towards the downstream annular portion of the platform of the annular row of mobile vanes.

Claims

1. A vane stage extending around a longitudinal axis and designed to be fitted in a turbine engine compressor, the vane stage comprising an annular row of mobile vanes arranged upstream from an annular row of stator vanes, wherein the annular row of stator vanes comprises a radially internal annular platform bearing radial blades, an upstream annular portion of which is arranged upstream from said blades and is surrounded radially outwards by a downstream annular portion of an annular platform of the upstream row of mobile vanes, wherein the upstream annular portion of the annular platform of the annular row of stator vanes comprises a radially external annular face from which fins extend, said fins are distributed around the longitudinal axis and extend radially outwards towards the downstream annular portion of the platform of the annular row of mobile vanes, characterised in that the fins each comprise an intrados face and an extrados face oriented circumferentially in an identical manner to the intrados faces and extrados faces of the blades of the stator vanes.

2. The vane stage of claim 1, wherein an angle between the longitudinal axis and the tangent to the mean camber line at the leading edge of the fins is between 45° and 90°.

3. The vane stage of claim 1, wherein an angle between the longitudinal axis and the tangent to the mean camber line at the trailing edge of the fins is on the order of the leading angle between the longitudinal axis and the tangent to the mean camber line at the leading edge of a blade in the row of stator vanes.

4. The vane stage of claim 3, wherein the angle is between 10° and 75°.

5. The vane stage of claim 1, wherein the external annular face of the upstream annular portion is tapered with a section increasing in the downstream direction.

6. The vane stage of claim 5, wherein said annular face is inclined by an alpha angle relative to the longitudinal axis of between 0° and 90°.

7. The vane stage of claim 1, wherein the relative pitch defined by the ratio S/C is between 0.3 and 0.9, where S is the distance between two leading edges of two circumferentially adjacent fins and C is the string of a fin.

8. A turbine engine compressor comprising at least one stage of claim 1, wherein a downstream annular row of mobile vanes is arranged axially downstream from the annular row of stator vanes and is connected to the annular row of mobile vanes upstream by means of an annular shroud extending radially inside the annular row of stator vanes and bearing lips sealedly interacting with a ring of abradable material borne by a radially internal annular platform of the annular row of stator vanes.

9. A turbine engine comprising the compressor of claim 8.

10. The vane stage of claim 1, wherein the angle between the longitudinal axis and the tangent to the mean camber line at the leading edge of the fins is on the order of 85°.

11. The vane stage of claim 3, wherein the angle is on the order of 55°.

12. The vane stage of claim 5, wherein said annular face is inclined by an alpha angle relative to the longitudinal axis of the order of 30°.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1, already described above, is a schematic illustration of a portion of a compressor of a turbine engine;

(2) FIG. 2 is a schematic illustration of a portion of a compressor according to the invention;

(3) FIG. 3 is a schematic view along the longitudinal axis of the annular row of stator vanes in FIG. 2;

(4) FIG. 4 is a schematic top view of fins according to the invention;

(5) FIG. 5 is a schematic view of the air flow through fins in the configuration according to the invention.

DETAILED DESCRIPTION

(6) In the present document, the terms internal and external in addition to interior and exterior are to be interpreted in relation to the longitudinal axis X. Also, the terms upstream and downstream are to be interpreted in relation to the direction of flow of the air flow. Likewise, the term annular denotes components extending angularly around the longitudinal axis X without these components necessarily being formed of a single piece. Hence, an annular platform, i.e. one that extends in a ring shape, may comprises a plurality of elementary platforms arranged end to end without the ends of said platforms necessarily being mutually contiguous. The overall shape of the platform is nevertheless annular.

(7) FIG. 2 illustrates a stage 16 of a compressor 10 with a longitudinal axis X comprising an annular row of rotor vanes 12 upstream and an annular row of stator vanes 14 downstream. The annular row of stator vanes 14 is mounted upstream from the annular row of rotor vanes 12 of the downstream stage 16. As clearly shown, the blades 24 of the mobile vanes 12 and the blades 18 of the stator vanes 14 extend radially outwards from a radially internal annular platform 20, 26. The internal annular platform 20 of the annular row of stator vanes 14 comprises an upstream annular portion 20c arranged upstream from the stator blades 18 and a downstream annular portion 20d arranged downstream from said stator blades 18. Likewise, the annular platform 26 of the upstream annular row of rotor vanes 12 in addition to the annular platform 26 of the downstream annular row of rotor vanes 12 each comprise upstream 26c and downstream 26d annular portions arranged upstream and downstream, respectively from the blades 24. As can be seen in FIG. 2, it is noticed that the upstream annular portion 20c of the annular platform 20 of the annular row of stator vanes is arranged radially inside the downstream annular portion 26b of the annular platform 26 of the upstream annular row of mobile vanes.

(8) Likewise, it is noticed that the annular rows of rotor vanes 12 are connected to each other by an annular shroud 30 bearing annular lips 32 sealedly interacting by friction with a ring 34 made of abradable material, so as to limit downstream to upstream air circulations as mentioned previously in connection with FIG. 1 of the prior art.

(9) As illustrated in FIG. 2 as well as in FIG. 3, the upstream annular portion 20c of the annular stator platform 20 features a radially external annular face 48 that is obliquely inclined relative to the longitudinal axis X. More specifically, this radially external annular face 48 is tapered, i.e. has the shape of a truncated cone of revolution, having a section increasing in the downstream direction. The alpha angle of the external annular face relative to the longitudinal axis is between 5° and 90°, preferably between 10° and 45° and more preferably on the order of 30°.

(10) Likewise, fins 50 are formed on the upstream annular portion 20c of the stator platform 20, with these fins 50 being regularly distributed around the longitudinal axis X and extending radially outwards in the direction of the downstream annular portion 26d of the upstream mobile platform 26.

(11) During operation, the parasitic air 42 circulating in the annular gap between the downstream end 20b of the stator platform 20 and of the annular platform 26 of the downstream annular row of mobile vanes 12 and circulating through the sealing device with lips 32, thus flows with an angle α greater than zero which makes it possible to control the angular orientation relative to the longitudinal axis (i.e. the axis of the turbine engine) and in a radial plane of the reinjected flow rate and limits introductions of air into the annular gap between the downstream end 26b of the annular platform 26 of the upstream annular row of mobile vanes 12 and the upstream end 20a of the annular row of stator vanes 14.

(12) Likewise, as illustrated in FIG. 4, each fin 50 has an intrados face 52 and an extrados face 54 connected to each other by a leading edge 56 and a trailing edge 58. These vanes therefore do not have a symmetrical profile according to their string, which is represented by the letter C in FIG. 4. The orientation of the fins can be defined by the angle β1 in relation to the leading edge and the angle β2 in relation to the trailing edge. These angles β1 and β2 are determined in a plane P perpendicular to a normal N on the external annular face 48 of the upstream annular portion 20c of the annular platform 20, with this plane P passing through the leading edge 56 of the fin (FIG. 2).

(13) According to the given definition of said plane P, it is understood that the latter is parallel to a generator of the external annular face 48, which is tapered in this case. It is clearly understood that the term generator is used with reference to the general geometric definition of the face but does not indicate that it is continuous over 360° as already explained above.

(14) When the external annular face 48 is concave curved with a concavity turned radially outwards, the full value of the overall definition of the aforementioned plane P will be understood.

(15) Measured in the aforementioned plane p, the angle β1 is that defined between the longitudinal axis X and the tangent to the mean camber line 60 at the leading edge 56 of the fins 50 and is between 45° and 90°, preferably on the order of 80° to 90°, preferably on the order of 85°. This choice of angle makes it possible to adapt the incidence of the fins to the recirculation flow, which has a major tangential component.

(16) Also measured in the aforementioned plane P, the angle β2 is that defined between the longitudinal axis X and the tangent to the mean camber line at the trailing edge 58 of the fins 50 and is on the order of the leading angle between the longitudinal axis X and the tangent to the mean camber line at the leading edge 56 of a blade 18 in the row of stator vanes 14. It can be seen that a specific orientation of the leading edge 56 makes it possible to orient the outgoing air flow of the grid of fins 50 with an ideal incidence in the direction of the grid of stator vanes 14. The angle β2 is between 10° and 75° and preferentially on the order of 55°.

(17) The invention thus reduces the risks of air separation at the root 46 of the blade 18 of the stator vanes 14, thereby increasing the pumping margin of the compressor 10. The reintroduced air also has an orientation that facilitates its flow through the stator vane grid 14.

(18) From a practical point of view, the fins 50 could be executed either by welding on to the annular portion 20c upstream from the stator platform 20 or be executed in a single piece with the latter.

(19) In a practical embodiment, the relative pitch defined by S/C will preferably be determined so as not to cause sonic cutoff, between 0.3 and 0.9, wherein S is the circumferential distance between two leading edges 56 of two circumferentially consecutive fins 50 and C is the string of a fin 50.

(20) In an embodiment not specifically shown in the figures, an annular track made of abradable material can be formed on the internal annular face of the downstream annular portion 26b of the upstream annular platform 26 of the annular row 10 of rotor vanes. The radially external ends of the fins will therefore be adapted to establish contact with the abradable ring. This configuration will prove interesting in cases in which it is difficult to guarantee absence of contact between the stator fins and the rotor radially opposite.