EP1726783B1 - Hollow rotor blade for the turbine of a gas turbine engine, provided with a tip cup - Google Patents

Description

The invention relates to a hollow rotor blade for the turbine of a gas turbine engine, in particular for a high pressure type turbine.

More specifically, the present invention relates to the production of a hollow blade of the type which comprises an internal cooling passage, an open cavity located at the free end of the blade and delimited by a bottom wall extending over the entire free end of the blade and a flange extending between the leading edge and the trailing edge along at least the upper surface, and cooling channels connecting the internal cooling passage and the free end on the side of the intrados wall, the cooling channels being inclined relative to the intrados wall, the intrados wall having a projecting end portion whose outer face is inclined with respect to the outer face of the intrados wall, the bottom wall being connected to the intrados wall at the location of the end portion and the cooling channels being disposed in the end portion parallel to the an outer face of the end portion so that they open on the top of the end portion towards the free end of the blade, at least a portion of the top of the end portion being in the same plane as the outer face of the bottom wall, so that at least a portion of the cooling channels open from the intrados wall at the front of the cavity.

Cooling channels of this type are intended to cool the free end of the blade because they allow to discharge a jet of cooling air from the internal cooling passage, towards the end of the blade at the level of the blade. the upper end of the outer face of the intrados wall. This air jet creates "thermal pumping", that is to say a decrease in the temperature of the metal by absorption of calories in the heart of the metal wall, and a cooling air film that protects the end of the vanes on the intrados side.

In fact, because of the high working speeds at the end of these blades and the temperatures at which these blades are subjected, it is necessary to cool them so that their temperature remains lower than that of the gases in which they work.

It is for this reason that, conventionally, the blades are hollow to allow their cooling by the air present in an internal cooling passage.

In addition, it is known to provide, at the end of the blade, an open cavity, also called "bath": this blade end shape limits the facing surfaces between the end of the blade and the corresponding annular surface of the turbine casing, to protect the body of the blade against damage caused by the possible contact with an annular segment.

The documents US 6,231,307 , EP0816636 and FR 2,858,650 have such a hollow blade further provided with cooling channels connecting the internal cooling passage and the face external of the rim of the cavity at the intrados wall, these cooling channels opening, at their outlet, on the outer face of the intrados wall towards the top of said flange.

These cooling channels located on the side of the intrados wall thus allow the outlet, from the internal cooling passage, of a jet of air colder than that surrounding the intrados wall, this air jet forming a cooling air film located on the outside face of the intrados wall, which is sucked in the direction of the extrados wall, passing over the end of the blade.

In the document US 6,231,307 these inclined cooling channels connect the inner cooling passage and the outer face of the cavity flange at the intrados wall by being arranged (see FIG. figure 2 of this document) so as to pass through the bottom wall of the cavity and the rim of the cavity at the intrados wall, passing through said cavity.

This solution therefore requires a significant material thickness, either for the bottom wall of the cavity or for the rim of the cavity, so as not to call into question the performance of thermomechanical resistance at the end of the blade. In addition, this solution greatly limits the flow of cooling air that reaches the top of the rim because most of the flow exits the internal cooling passage through the first section of the cooling channels and enters directly into the cavity without success. on the outside face of the intrados wall.

The solution of the document EP 0 816 636 , visible on the figure 5 of this document, consists in arranging these cooling channels so that they pass through the intrados wall by opening on the outside face of this intrados wall at the base of the rim of the cavity.

Again, this solution requires a significant material thickness, either for the bottom wall of the cavity or for the rim of the cavity, so as not to call into question the performance of thermomechanical resistance at the end of the blade.

The document FR 2 858 650 a proposed a solution (see figure 5 ) which consists in providing a reinforcement of material between the rim and the bottom wall of the cavity along at least a portion of the intrados wall, whereby said rim is widened at its base adjacent to said wall; bottom so that the cooling channels open near the top of the rim without altering the mechanical strength of the end of the blade. In this way, by the presence of the material reinforcement, the cooling channels can thus emerge closer to the top of the rim without modifying the distance between these cooling channels and the bottom wall of the cavity.

However, given the operating temperatures of the turbines always higher, these solutions do not currently allow the realization of a hollow blade whose cooling at the end is sufficient.

Indeed, to maintain sufficient thermomechanical resistance around the cooling channels, the use of large wall thicknesses leads to a very significant increase of the (or) wheel (s) mobile (s) of the turbine. Consequently, since the greater the material thicknesses, the more the temperature increases because of a slower cooling, these large thicknesses of material do not allow the realization of a sufficient cooling at the end of the blade to allow a functioning of the turbine at the higher temperatures desired.

It should be noted that if there is insufficient cooling at the end of the blade, local burns can occur which can lead to loss of metal which increases the play, which affects the aerodynamic efficiency of the turbine. Also, when the rim of the cavity sees its temperature increase too strongly, there is a risk of burns with degradation of the metal wall.

The document US 2002/0182074 discloses a turbine blade whose end is in the form of a bath with a bottom surrounded by flanges, the intrados wall of the flange located at the intrados comprising an excrescence traversed by cooling channels parallel to the outer surface of this protrusion. In one embodiment, the intrados flange is such that the upper surface of this protrusion is in the same plane as the bottom of the bath.

The present invention seeks to solve the aforementioned problems.

Accordingly, the present invention aims to provide a hollow rotor blade for the turbine of a gas turbine engine, of the type mentioned above, to cool the end of the blade sufficiently to improve its reliability without reducing the aerodynamic and thermomechanical performance of dawn.

For this purpose, according to the present invention, the inner face of the rim of the upper surface is inclined by widening the flange towards the free end of the blade.

In this way, it is understood that by the presence of the end portion projecting from the intrados wall, the cooling channels opening directly to the top of this end portion, the cooling air is directly sent at the free end of the dawn, just upstream of the open cavity or "bathtub".

This solution also has the additional advantage of allowing, in addition to feeding the outlet of the cooling channels to the free end of the blade, to achieve, in that the outer face of the end portion is sloping, an intrados surface of the dawn which is made concave at the top of the blade.

This particular shape is preferably present all along the profile, from the leading edge to the trailing edge. It prevents the flow in the game at the top of dawn. Indeed, the inclination of the wall towards the intrados, at the top of the blade, makes it possible to cause a strong detachment of the boundary layer at the top of the blade. Thus, the passage section "seen" by the flow between the head of the blade and the housing will be all the lower as the separation of the boundary layer will be important: thus reduces the flow "lost" in the gap between the blade head and the crankcase.

Thus, this projecting end portion with its inclined outer face provides not only thermal but also hydraulic improvements at the blade tip, and a mechanical reinforcement of the blade tip at the location of the cavity open or "bathtub".

In addition, the inclination of the inner face of the rim of the extrados wall in the direction of the intrados wall improves the limitation of the flow passing through the game.

Overall, thanks to the solution according to the present invention, it is possible to increase the overall performance of the turbine.

It should be noted that one can consider several orientations for the bottom wall.

According to a first variant, the outer face of the bottom wall is substantially perpendicular to the intrados wall and the extrados wall, that is to say that the outer face of the bottom wall has a parallel orientation to the axis of dawn, which can be described as horizontal.

According to a second variant, the outer face of the bottom wall is inclined with respect to the intrados wall and the extrados wall, forming an acute angle with the rim of the cavity extending the extrados wall. Here, the outer face of the bottom wall moves away from the free end of the blade-or approaches the axis of the blade-from the pressure wall to the extrados wall.

• la figure 1 montre une vue en perspective d'une aube de rotor creuse pour turbine à gaz conventionnelle,
• la figure 2 montre en perspective, de manière agrandie, l'extrémité libre de l'aube de la figure 1,
• la figure 3 est une vue simplifiée selon la direction III de la figure 2, de l'extrémité libre de l'aube,
• la figure 4 est une vue analogue à celle de la figure 2, après que le bord de fuite de l'aube ait été retiré par une coupe longitudinale,
• la figure 5 est une vue en coupe longitudinale selon la direction V-V de la figure 3 ou de la figure 4, et
• les figures 6 et 7 sont respectivement des vues analogues à celles des figures 3 et 5 montrant les adaptations apportées à l'aube, selon la présente invention ;
• la figure 8 est une vue analogue à celle de la figure 7 montrant une version légèrement différente ;
• la figure 9 est une vue d'extrémité simplifiée similaire à celle de la figure 3 pour une aube combinant différentes formes, dont une conforme à la présente invention, pour l'extrémité libre de l'aube ;
• les figures 10 et 11 sont des vues analogues à celle de la figure 5, selon les directions X-X et XI-XI de la figure 9, montrant les deux autres formes de l'extrémité de l'aube de la figure 9 ; et,
• la figure 12 représente une variante de la figure 7 avec les perçages débouchants décalés sous la base du rebord d'extrados.

Other advantages and characteristics of the invention will become apparent on reading the following description given by way of example and with reference to the appended drawings in which:

• the figure 1 shows a perspective view of a hollow rotor blade for a conventional gas turbine,
• the figure 2 shows in perspective, in an enlarged way, the free end of the dawn of the figure 1 ,
• the figure 3 is a simplified view in direction III of the figure 2 , from the free end of dawn,
• the figure 4 is a view similar to that of the figure 2 after the trailing edge of the blade has been removed by a longitudinal section,
• the figure 5 is a longitudinal sectional view along the direction VV of the figure 3 or from figure 4 , and
• the Figures 6 and 7 are respectively views similar to those of figures 3 and 5 showing the adaptations made to the dawn, according to the present invention;
• the figure 8 is a view similar to that of the figure 7 showing a slightly different version;
• the figure 9 is a simplified end view similar to that of the figure 3 for a blade combining different shapes, including one according to the present invention, for the free end of the blade;
• the Figures 10 and 11 are views similar to that of the figure 5 , according to directions XX and XI-XI of the figure 9 , showing the other two forms of the end of the dawn of the figure 9 ; and,
• the figure 12 represents a variant of the figure 7 with the outgoing holes staggered under the base of the extrados rim.

On the figure 1 An example of a conventional hollow rotor blade for a gas turbine is visible in perspective. Cooling air (not shown) flows inside the blade from the bottom of the blade root 12 in the radial (vertical) direction towards the free end 14 of the blade (in high on the figure 1 ), then this cooling air escapes through an outlet to join the main gas flow.

In particular, as Figures 2 to 5 this cooling air circulates in an internal cooling passage 24 situated inside the vane 10 and which ends at the free end 14 of the vane at the level of through bores 15.

The body of the blade is profiled so that it defines a lower surface wall 16 (on the left in all the figures) and an extrados wall 18 (on the right in all the figures). The intrados wall 16 has a generally concave shape and is the first face to the flow of hot gases, that is to say the gas pressure side, while the extrados wall 18 is convex and is presented by following the flow of hot gases, that is to say the suction side of the gas.

The intrados and extrados walls 18 are joined at the location of the leading edge 20 and at the location of the trailing edge 22 which extend radially between the free end 14 of the blade and the top of the foot 12 of dawn.

As can be seen from the enlarged views of figures 2 , 4 and 5 , at the free end 14 of the blade, the internal cooling passage 24 is delimited by the inner face 26a of a bottom wall 26 which extends over the entire free end 14 of the blade, between the intrados wall 16 and the extrados wall 18, from the leading edge 20 to the trailing edge 22.

The through holes 15 are distributed so as to optimize the cooling, from the leading edge 20 to the edge of leak 22, radially crossing the entire thickness of the bottom wall 26.

At the free end 14 of the blade, the intrados and extrados walls 16, 18 form the rim 28 of a "bath" or open cavity 30 in the opposite direction to the internal cooling passage 24, radially outward (upwards in all figures).

This rim 28 is formed of an extrados rim 281 and a lower face flange 282 respectively extending radially outwards (upwards in all the figures) the extrados wall 18 and the lower surface wall. 16, beyond the bottom wall 26 and to the free end 14 of the blade.

As it appears on figures 2 , 4 and 5 this open cavity 30 is therefore delimited laterally by the inner face of this flange 28 and in the lower part by the outer face 26b of the bottom wall 26.

The flange 28 thus forms a thin wall along the profile of the blade which protects the free end 14 of the blade 10 from contact with the corresponding annular surface of the turbine casing.

As can be seen more precisely on the sectional view of the figure 5 , inclined cooling channels 32 pass through the intrados wall 16 to connect the internal cooling passage 24 to the outside face of the intrados wall 16, below the outer face 28a of the intrados flange 282.

These cooling channels 32 are inclined so that they open towards the top 28b of the lower edge 282 in order to cool as much as possible this vertex 28b, along the intrados wall 16, or more precisely the along the outer face 28a of the underside 282.

As can be seen on the figure 5 by the arrow 33, at the outlet of the cooling channels 32, an air jet is directed towards the top 28b of the intrados flange 282 along the intrados wall 16.

In the case of known blades, as is shown more precisely on the figure 5 in order to maintain a sufficient thermomechanical resistance at the free end of the blade 14, a sufficient distance B must be left between the outlet of the cooling channels 32 (the reference point being the axis of these channels) and the intersection (B1) between the inner face 28c of the intrados flange 282 at the intrados wall wall 16 and the outer face 26b of the bottom wall 26 facing towards said cavity 30.

This situation, which results from a necessity of mechanical construction, causes the distance A, measured between the exit of the cooling channels 32 (the reference point being the axis of these channels) and the top 28b of the flange 28 on the wall side. intrados, which is much greater than the distance B above, is too important to sufficiently cool the top 28a.

In order to overcome this drawback, the intrados wall 16 has a projecting end portion 34 whose external face is inclined with respect to the outside face of the intrados wall 16, the cooling channels 32 being arranged through this end portion 34.

• le sommet de la portion d'extrémité 34 est dans le même plan que la face extérieure de la paroi de fond 26, de sorte que lesdits canaux de refroidissement 32 débouchent de la paroi d'intrados 16 à l'avant de la cavité 30 : ceci signifie que selon l'invention, puisque la portion d'extrémité en saillie 34 s'arrête à la même hauteur que la face extérieure 26b de la paroi de fond 26 alors l'extrémité de l'aube 14 et la paroi d'intrados 16 ne comportent pas de rebord d'intrados 282, et
• la face intérieure 28c dudit rebord 281 de la paroi d'extrados 18 est inclinée en élargissant ledit rebord 281 en direction de l'extrémité libre 14 de l'aube 10.

In addition, according to the present invention, it is provided that:

• the top of the end portion 34 is in the same plane as the outer face of the bottom wall 26, so that said cooling channels 32 open from the intrados wall 16 at the front of the cavity 30: this means that according to the invention, since the protruding end portion 34 stops at the same height as the outer face 26b of the bottom wall 26 then the end of the blade 14 and the lower surface 16 have no underside 282, and
• the inner face 28c of said flange 281 of the extrados wall 18 is inclined by widening said flange 281 in the direction of the free end 14 of the blade 10.

As it appears in particular on figures 7 and 8 , the intrados wall 16 is outwardly projecting at the location of the end portion 34 located at the free end 14 of the blade, so that the outer face of the end portion 34 is inclined is forms an acute angle α with the radial direction (vertical on the figures 7 and 8 ) of the outer face of the remainder of the intrados wall 16, this angle α being preferably between 0 and 45 °, in particular between 10 and 35 °, advantageously between 15 and 30 °, and preferably of the order 30 °.

In this way, if one follows the outer face of the intrados wall 16 from the root of the blade 12 towards the free end 14, the general direction of the intrados wall 16 is radial (vertical) then finally forms, at the end portion 34, a very open concave contour at an obtuse angle complementary to the acute angle α.

This end portion 34 extends over a height such that the bottom wall 26 is connected to the intrados wall 16 at the location of the end portion 34, the apices of the bottom wall 26 and the end portion 34 being aligned. Thus, the base of the end portion 34, opposite to the free end 14, is located at a location radially between the inner face 26a of the bottom wall 26 and 75% of the height of the lower surface. 16 from the 12th foot of dawn.

In addition, the cooling channels 32 are always inclined but in this configuration according to the invention, since they pass through the end portion 34, they can lead directly to the bottom of the open cavity 30 forming a bath through the portion of end 34 all the way up.

In this way, the cooling air emerging through the channels 32 emerges (arrow 33) into the open cavity 30, so that a colder air flow remains constantly present at the top of the blade, at the level of the free end 14, upstream of the open cavity 30, which contributes to improving the thermomechanical resistance of the blade.

In addition, the presence of the cooling channels 32 inside the end portion 34 to cool these areas of material by thermal conduction.

The variant represented on the figure 8 is only different from the figure 7 in that the bottom wall 26 is no longer orthogonal (horizontal) with respect to the intrados and extrados walls 18, but the bottom wall 26 is inclined. More precisely, the outer face 26b of the bottom wall 26 of the open cavity 30 forms an acute angle, in other words less than 90 °, with the outer face 28a of the extrados rim 281 or even of the extrados wall 18 .

In this way the outer face 26b moves away from the free end 14 of the blade from the intrados wall 16 towards the extrados wall 18.

This configuration allows the cooling air from the channels 32 (arrow 33) to be directed inside the open cavity 30 to the bottom wall 26, coming to combine with the cooling air from holes 15.

According to the embodiment of the figure 7 the top of the end portion 34 is orthogonal to the intrados and extrados walls 16, in a direction parallel to the top of the extrados rim 281.

Also, the extrados rim 281 forms a wall located in the radial extension of the extrados wall 18, its outer face 28a being vertical ( figures 7 and 8 ).

On the other hand, as it appears on figures 7 and 8 , the extrados rim 281 has an inner face 28c, turned towards the intrados wall 16 and facing the open cavity 30, not vertical but extending inclined, forming an acute angle, that is to say less than 90 °, with the outer face 26b of the bottom wall 26, or with the extrados wall.

In this case, the upper edge 281 is therefore wider at its top 28b.

This inclination of the inner face 28c of the extrados rim 281 in the direction of the intrados wall wall 16 makes it possible to improve the limitation of the flow passing through the game. This limitation of flow comes in fact to add to that generated by the end portion 34 projecting from the intrados wall 16.

Moreover, since there is no underside (see 282 on the figure 11 ) in the case of figures 7 and 8 this inclination of the inner face 28c of the extrados flange 281 in the direction of the intrados wall wall 16 makes it possible to obtain a flow limitation without outgrowth outside the geometry defined by the aerodynamic calculations.

It should be noted that the embodiment illustrated and described above in relation to the figures 7 and 8 can be combined on the same dawn with other forms.

• à l'avant de l'aube, en aval du bord d'attaque 20, on retrouve la conformation de la figure 7 avec une portion d'extrémité 34 en saillie côté paroi d'intrados 16, sans rebord d'intrados et avec un rebord d'extrados 281 élargi à son sommet 28b ;
• à l'arrière de l'aube, en amont du bord de fuite 22, on retrouve une disposition conforme à celle de la figure 11 avec, du côté de la paroi d'intrados 16, une portion d'extrémité 34 en saillie comprenant un rebord d'intrados 282 élargi à son sommet 28b (en fait il y a une face extérieure 28a du rebord d'intrados 282 qui est inclinée et une face intérieure 28b du rebord d'intrados 282 qui est verticale) et du côté de la paroi d'extrados 18, un rebord d'extrados 281 non élargi à son sommet, le sommet des rebords d'intrados 282 et d'extrados 281 étant perpendiculaires à la direction verticale des parois d'intrados 16 et d'extrados 18.

So, for example, the figure 9 illustrates the free end 14 of a blade 10 which has several configurations between its leading edge 20 and its trailing edge 22:

• at the front of the dawn, downstream of the leading edge 20, we find the conformation of the figure 7 with an end portion 34 projecting from the intrados wall side 16, without a soffit flange and with an extrados rim 281 enlarged at its top 28b;
• at the rear of the dawn, upstream of the trailing edge 22, there is a disposition in conformity with that of the figure 11 with, on the side of the intrados wall 16, a protruding end portion 34 comprising a bottom flange 282 enlarged at its top 28b (in fact there is an outer face 28a of the lower flange 282 which is inclined and an inner face 28b of the intrados flange 282 which is vertical) and the side of the extrados wall 18, an extrados rim 281 not widened at its top, the top of the flanges 28 and 28 extrados 281 being perpendicular to the vertical direction of the intrados and extrados walls 18.

• côté paroi d'intrados 16, cette partie médiane est identique à la configuration de la figure 7 ou de l'avant de l'aube de la figure 9, à savoir qu'il n'y a pas de rebord d'intrados est que la portion d'extrémité en saillie 34 s'arrête à la hauteur de la face extérieure 26b de la paroi de fond 26 ;
• côté paroi d'extrados, le rebord d'extrados 281 est vertical, ses faces extérieure 28a et intérieure 28c étant parallèles entre elles comme pour la la configuration de la figure 11.

Moreover, as we see on the figure 10 , the middle part, between the front and the back of the dawn of the figure 9 is different:

• side wall 16, this middle portion is identical to the configuration of the figure 7 or before the dawn of the figure 9 that there is no underside rim is that the protruding end portion 34 stops at the height of the outer face 26b of the bottom wall 26;
• the extrados wall side, the extrados rim 281 is vertical, its outer 28a and inner 28c faces being parallel to each other as for the configuration of the figure 11 .

According to an embodiment variant visible on the figure 12 , there is provision for a development in relation to the figure 7 , in that the holes 15 are offset towards the upper wall 18, opening under the base of the extrados rim 281, at the inner face 28c inclined.

Claims (8)

1. A hollow rotor blade (10) for the turbine of a gas turbine engine, the blade including an internal cooling passage (24), an open cavity (30) situated at the free end (14) of the blade (10) and defined by an end wall (26) extending over the entire free end of the blade (14), by a rim (28, 281, 282) extending between the leading edge (20) and the trailing edge (22) along at least the suction side wall (18), and cooling channels (32) connecting said internal cooling passage (24) and the free end (14), beside the pressure side wall (16), said cooling channels (32) being inclined relative to the pressure side wall (16), the pressure side wall (16) presenting a projecting end portion (34) whose outside face is inclined relative to the outside face of the pressure side wall (16), the end wall (26) being connected to the pressure side wall (16) at the location of said end portion (34), and said cooling channels (32) being disposed in said end portion (34), being parallel to the outside face of said end portion (34) so that they open out into the tip of said end portion (34) towards the free end (14) of the blade (10), at least a part of the tip of the end portion (34) lying in the same plane as the outside face of the end wall (26), such that at least a part of said cooling channels (32) open out into the pressure side wall (16) into the bottom of the cavity (30), the blade being characterized in that the inside face of said rim (281) of the suction side wall (18) is inclined at least for a portion so as to enlarge said rim (281) radially towards the free end (14) of the blade (10).
2. A turbine blade (10) according to claim 1, characterized in that the outside face (26b) of the end wall (26) is substantially perpendicular to the pressure side wall (16) and to the suction side wall (18).
3. A turbine blade (10) according to claim 1, characterized in that the outside face (26b) of the end wall (26) is inclined relative to the pressure side wall (16) and to the suction side wall (18), forming an acute angle with the rim (281) of the cavity extending the suction side wall (18).
4. A turbine blade (10) according to any one of claims 1 to 3, characterized in that:

   · in a portion of the blade extending upstream from the leading edge, the tip of the end portion (34) lies in the same plane as the outside face of the end wall (26), and the inside face of said rim (281) of the suction side wall (18) is inclined so as to enlarge said rim (281) radially towards the free end (14) of the blade (10) ; while

   · in a portion of the blade extending downstream from the trailing edge, beside the pressure side wall (16), there is a projecting end portion (34) having a pressure side rim (282) that is enlarged at its tip (28b) in the radial direction towards the free end of the blade, and beside the suction side wall (18) there is a suction side rim (281) that is not enlarged at its tip in the radial direction towards the free end of the blade.
5. A turbine blade (10) according to any one of claims 1 to 4, characterized in that through holes (15) pass through the end wall (26) between the internal cooling passage (24) and the base of the rim (281) of the suction side wall (18).
6. A turbine blade (10) according to any one of claims 1 to 5, characterized in that it is used for a high pressure turbine.
7. Turbine comprising a blade according to any of claims 1 to 5.
8. Gas turbine engine comprising a blade according to any of claims 1 to 5.

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