Turbine blade comprising a cooling circuit

Abstract

An aviation turbine blade extending in the radial direction and presenting a pressure side and a suction side, including a plurality of pressure side cavities extending radially at the pressure side of the blade, a plurality of suction side cavities extending radially at the suction side of the blade, and at least one central cavity located in the central portion of the blade and surrounded by pressure side cavities and by suction side cavities, the blade further including a plurality of cooling circuits, in which at least a first cooling circuit comprises: a first cavity and a second cavity, the first and second cavities communicating with each other at a radially inner end and at a radially outer end of the blade.

Claims

1. An aviation turbine blade extending in the radial direction and presenting a pressure side and a suction side, including a plurality of pressure side cavities extending radially at the pressure side of the blade, a plurality of suction side cavities extending radially at the suction side of the blade, and at least one central cavity located in a central portion of the blade and surrounded by the plurality of pressure side cavities and by the plurality of suction side cavities, the blade including a plurality of cooling circuits independent from one another, in which at least a first cooling circuit comprises: a first cavity and a second cavity, the first and second cavities communicating with each other at a radially inner end and at a radially outer end of the blade; a third cavity communicating with the second cavity at the radially outer end; and a fourth cavity communicating with the third cavity at the radially inner end; the first and second cavities being configured to be fed jointly with cold air through a common air intake opening at the radially inner end, and so that the air flows radially therein in a same direction; the first cavity being a pressure side cavity of the plurality of pressure side cavities, the second cavity being the at least one central cavity, and the third and fourth cavities being suction side cavities of the plurality of suction side cavities.

2. The blade according to claim 1, including a plurality of pressure side orifices, each communicating with the first cavity and opening out in the pressure side of the blade.

3. The blade according to claim 1, including a plurality of suction side orifices, each communicating with the fourth cavity and opening out onto the suction side of the blade.

4. The blade according to claim 1, including at least a second cooling circuit including two pressure side cavities of the plurality of pressure side cavities, communicating with each other via a plurality of passages distributed in the radial direction along the blade between the two pressure side cavities, one of the two pressure side cavities being fed with cold air via an air intake opening at the radially inner end of the blade.

5. The blade according to claim 4, including at least a third cooling circuit including a suction side cavity of the plurality of suction side cavities and a trailing edge cavity extending radially both on the suction side and on the pressure side of the blade near the trailing edge, both the suction side cavity and the trailing edge cavity being fed with cold air via an air intake opening at the radially inner end of the blade, the suction side cavity forming an angle at the radially outer end of the blade, in such a manner as to extend until it reaches the trailing edge of the blade.

6. The blade according to claim 1, including two thin cavities or less, wherein, in a section perpendicular to the radial direction, a thin cavity has a first length that is greater than or equal to at least seven times a second length.

7. A gas turbine including blades according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages can be better understood on reading the following detailed description of various embodiments of the invention given as non-limiting examples. The description refers to the accompanying sheets of drawings, in which:

(2) FIG. 1 is a perspective view of a turbine blade of the present invention;

(3) FIG. 2 is a perspective view representing symbolically the cavities of the various cooling circuits of the blade;

(4) FIG. 3 is a perspective view representing symbolically the cavities of the first cooling circuit of the blade;

(5) FIGS. 4A to 4E are cross sections as shown in FIG. 3 for various radial positions going from the blade root to the blade tip; and

(6) FIG. 5 is a cross section of the blade, showing the zones in which heat transfer is the greatest.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) The invention is described below with reference to FIGS. 1 to 5. It should be observed that FIGS. 2 and 3 do not show portions of the blade as such, but show the cavities within the blade. In other words, the lines shown in FIGS. 2 and 3 represent the internal walls of the blade defining these cavities.

(8) FIG. 1 shows a rotor blade 10, e.g. made of metal, for a high-pressure turbine of a turbine engine. Naturally, the present invention may also apply to other blades or vanes of a turbine engine.

(9) The blade 10 has an aerodynamic surface 12 (or airfoil that extends radially between a blade root 14 and a blade tip 16.

(10) The blade root 14 is adapted to be mounted on a disk of the rotor of the high-pressure turbine, the blade tip 16 being radially opposite from the blade root 14.

(11) The aerodynamic surface 12 presents four distinct zones: a leading edge 18 placed facing the flow of hot gas coming from the combustion chamber of the turbine engine; a trailing edge 20 opposite from the leading edge 18; a pressure side face 22; and a suction side face 24; the pressure and suction side faces 22, 24 connecting the leading edge 18 to the trailing edge 20.

(12) At the blade tip 16, the aerodynamic surface 12 of the blade is closed by a transverse wall 26. In addition, the aerodynamic surface 12 extends radially slightly beyond the transverse wall 26 in such a manner as to form a recess 28, hereafter referred to as a bathtub of the blade. This bathtub 28 therefore has a base formed by the transverse wall 26, an edge formed by the aerodynamic surface 12, and is open towards the blade tip 16.

(13) In the example described, the blade 10 includes three mutually independent cooling circuits designed for cooling the blade: a first cooling circuit 1, a second cooling circuit 2, and a third cooling circuit 3.

(14) The first cooling circuit 1 includes a first cavity A, a second cavity B, a third cavity C, and a fourth cavity D. The first cavity A is a pressure side cavity, the second cavity B is a central cavity, the third and fourth cavities C and D are suction side cavities.

(15) The first cooling circuit is fed with cold air by the cavities A and B at the blade root 14. The cold air is air acting as a heat transfer fluid that is taken from other circuits of the engine and that is colder than the air flowing over the pressure and suction side faces 22, 24. The first and second cavities A et B communicate with each other at the blade root 14, in the bottom 40% of the blade, preferably in the bottom 25%, more preferably in the bottom 10% in the radial direction, so as to form a first common chamber 31 (FIGS. 3 and 4E) extending radially at the blade root 14 over a length L1. The length L1 may represent not more than 40% of the total length of the blade. The first and second cavities A et B also communicate with each other at the blade tip 16, in the top 20% of the blade, preferably in the top 15%, more preferably in the top 10% in the radial direction, so as to form a second common chamber 32 (FIGS. 3 and 4A) extending radially over a length L2. The length L2 may represent not more than 20% of the total length of the blade. Between the common chambers 31 and 32, the cavities A and B are isolated from each other by a wall P extending radially along the blade 10. Consequently, the air coming from the first common chamber 31 then flows upwards in the cavities A and B (arrows in FIG. 3) separately and in parallel, until it reaches the second common chamber 32.

(16) In addition, the first cavity A communicates with the pressure side face 22 of the blade 10 via a plurality of pressure side orifices 40, distributed radially along the blade 10. Thus, a portion of the air flowing in the first cavity A is discharged through the orifices 40, in such a manner as to create a cooling film on the pressure side face 22, as well as through a blade tip orifice 42 located on the blade tip, in such a manner as to create a cooling film on the wall 26 of the bathtub 28. The air flowing in the first cavity A, which air is not discharged through the orifices 40 or 42 mixes with the air coming from the second cavity B, in the second common chamber 32.

(17) In addition, the cavity A may be defined, in its top portion, by a curved wall A extending over 20%, preferably 15%, more preferably 10% of the length of the blade in the radial direction, the curve of the wall A being directed towards the leading edge 18. This curved shape of the wall makes it possible to guide the air flowing in the cavity A towards the following cavities, and to ensure that air is distributed uniformly in the cavities while limiting head losses. Furthermore, the wall P separating the cavities A and B may comprise, in its top portion, a curved portion P, forming an angle relative to the rest of the wall P, in such a manner that this curved portion P is directed towards the leading edge 18. This curved portion P makes it possible to guide the air flowing in the cavity B towards the cavity C. The curved wall A and the curved portion P make it possible to facilitate causing the air coming from the cavities A and B to turn about into the cavity C, i.e. facilitating the change of airflow direction, passing from moving upwards in the cavities A and B to moving downwards in the cavity C. This also makes it possible to limit head losses during this about turn.

(18) The second and third cavities B and C communicate with each other at the blade tip 16, in the top 20% of the blade, preferably in the top 15%, more preferably in the top 10% in the radial direction, so as to form a third common chamber 33 (FIGS. 3 and 4B) extending radially over a length L3. The second and third chambers 32 and 33 therefore communicate with each other at the blade tip 16 (FIGS. 3 and 4A), in such a manner that the first cavity A may also communicate with the third cavity C. The air flowing in the third cavity C therefore comes from the cavities A and B, and flows downwards.

(19) Preferably, the length L3 may be greater than the length L2. Thus, the air flowing in the third cavity C comes mainly from the second cavity B. In addition, most of the air coming from the first cavity A has been discharged through the pressure side orifices 40 and the blade tip orifice 42. More precisely, at least 75%, preferably at least 80%, more preferably at least 85% of the air flowing in the third cavity C comes from the second cavity B. That presents the advantage of conserving cold air inside the third cavity C, in such a manner as to cool the suction side face 24 of the blade more effectively. Since the second cavity B is a central cavity, the air coming from it is colder than the air coming from the first cavity A, said first cavity being heated by heat transfer, in particular by forced convection, with the pressure side face 22.

(20) The third and fourth cavities C and D communicate with each other at the blade root 14, in the bottom 10% of the blade, preferably in the bottom 8%, more preferably in the bottom 6% in the radial direction, so as to form a fourth common chamber 34 (FIGS. 3 and 4E). The air flowing in the fourth cavity D therefore comes from the third cavity C, and flows upwards, i.e. from the blade root 14 to the blade tip 16. The fourth cavity D communicates with the suction side via a plurality of suction side orifices 44 distributed radially along the blade 10. Thus, a portion of the air flowing in the fourth cavity D is discharged through the orifices 44, in such a manner as to create a cooling film on the suction side face 24, as well as through a blade tip orifice 46 located on the blade tip 16, in such a manner as to create a cooling film on the wall 26 of the bathtub 28.

(21) The first cooling circuit 1 thus extends from the pressure side face 22, on the side of the trailing edge 20, until it reaches the suction side face 24, on the side of the leading edge 18. This configuration makes it possible to take advantage of the various effects associated with the fast rotation of the blade 10, in particular Coriolis force, in order to press the air against places requiring heat transfer to be optimized, in particular the walls defining the pressure side or suction side faces of the inside of the blade. The hatched areas in FIG. 5 show the areas in which the air does the least work, i.e. in which less heat transfer takes place. However, the arrows in FIG. 5 show the orientation of the Coriolis force, in other words the areas in which the air is pressed and in which heat transfer is optimized. This configuration thus makes it possible to reduce the flow of cold air required for cooling the blade 10, by targeting heat transfer on the desired areas.

(22) The central cavity B thus acts like a mechanically flexible core of the blade. The central cavity makes it possible to compensate for the mechanical deformation in the walls of the blade 10 adjacent to the pressure side and suction side faces 22, 24, which deformation is generated by thermal expansion due to high temperatures on the faces. This thus makes it possible to limit external excess stress on the blade 10.

(23) The second cooling circuit 2, independent from the first cooling circuit 1, comprises two pressure side cavities E and F. The cavity E, adjacent to the cavities A, B, C, and D of the first cooling circuit, is fed with cold air at the blade root 14 (FIG. 4E). The cavity F is located on the side of the leading edge 18 of the blade 10. The cavities E and F communicate with each other by means of a plurality of passages 52 distributed in the radial direction along the blade 10 between these two cavities (FIGS. 4B and 4D).

(24) The cavity E communicates with the pressure side face 22 of the blade 10 via orifices 50 that are distributed in the radial direction over at least a portion of the cavity E. Thus, when the cold air flows in the cavity, it exchanges heat by forced convection with the wall separating the cavity from the hot air on the pressure side, and it is also discharged through the orifices 50, generating a cooling film on the pressure side of the blade, while also penetrating into the other cavity via the plurality of passages 52. The air flowing in the cavity F is discharged through orifices 54 distributed in the radial direction over at least a portion of the cavity F.

(25) The third cooling circuit 3, independent from the first and second cooling circuits 1 and 2, includes a suction side cavity G adjacent to the cavities A, B, and C, and a trailing edge cavity H extending radially both on the suction side 24 and on the pressure side 22 of the blade on the trailing edge side 20. The cavities G and H are both fed with cold air by an air intake opening out at the blade root 14.

(26) The suction side cavity G extends firstly radially in a first cavity portion G, from the blade root 14 until it reaches the blade tip 16 along the suction side face 24, and it extends secondly in a direction that is substantially perpendicular to the radial direction in a second cavity portion G, along the bathtub 28, by forming an angle in the trailing edge direction 20 (FIG. 2), the second cavity portion G making it possible to cool the transverse wall 26 at the trailing edge 2. In other words, the cavity G extends from the blade root 14 to the trailing edge 20.

(27) In addition, the first cavity portion G presents a large aspect ratio such that, in cross-section (FIGS. 4C and 4D for example), one dimension (length) is at least three times greater than another dimension (width), giving it a slender, or elongate shape. That makes it possible to maximize the surface area for exchange between the air flowing in the cavity G and the suction side face 24. Apart from the trailing edge cavity H, the shape of which is determined by the shape of the blade 10 at the trailing edge 20, the suction side cavity G of the third cooling circuit 3 is the only cavity, from among all of the cavities within the blade 10, to present such an aspect ratio. By limiting the number of cavities that present such an aspect ratio, it is possible to facilitate the process of manufacturing the blade.

(28) The trailing edge cavity H does not extend radially over the entire length of the blade 10, and is limited in length by the second cavity portion G. In addition, the cavities of the third cooling circuit 3 communicate with trailing edge orifices 56 opening out on the pressure side face 22 at the trailing edge 20, the trailing edge orifices 56 being distributed radially along the blade 10. These orifices 56 make it possible to discharge the cold air flowing in both of these cavities.

(29) Although the present invention is described with reference to specific embodiments, it is clear that various modifications and changes may be undertaken on those embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, the number of cooling circuits and the number of cavities making up each of the circuits is not limited to the numbers presented in this example. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.

(30) It is also clear that all of the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all of the characteristics described with reference to a device can be transposed, alone or in combination, to a method.