EP2350441B1 - Guide blade for a gas turbine and associated gas turbine - Google Patents

Description

Technical area

The present invention relates to the field of gas turbine technology. It relates to a guide vane for a gas turbine according to the preamble of claim 1.

State of the art

Gas turbines with sequential combustion are known and have proven themselves in industrial use.
Such a gas turbine, which has become known in the art as GT24 / 26, for example, from an article of Joos, F. et al., "Field Experience of the Sequential Combustion System for the ABB GT24 / GT26 Gas Turbine Family", IGTI / ASME 98-GT-220, 1998 Stockholm , The local Fig. 1 shows the basic structure of such a gas turbine, where the local Fig. 1 in the present application as Fig. 1 is reproduced. Furthermore, such a gas turbine goes out EP-B1-0 620 362 out.

Fig. 1 shows a gas turbine 10 with sequential combustion, in which along an axis 19, a compressor 11, a first combustion chamber 14, a high pressure turbine (HDT) 15, a second combustion chamber 17 and a low pressure turbine (NDT) 18 are arranged. The compressor 11 and the two turbines 15, 18 are part of a rotor which rotates about the axis 19. The compressor 11 sucks in air and compresses it. The compressed air flows into a plenum and flows from there into premix burners, where this air is mixed with at least one fuel, fuel supplied at least via the fuel feed 12. Such Premix burners go out basically EP-A1-0 321 809 or EP-A2-0 704 657 out.
The compressed air flows into the premix burners, where the mixing, as stated above, takes place with at least one fuel. This fuel / air mixture then flows into the first combustion chamber 14, into which this mixture passes to form a stable flame front for combustion. The resulting hot gas is partially relaxed in the subsequent high-pressure turbine 15 under working performance and then flows into the second combustion chamber 17, where a further fuel supply 16 takes place. Due to the high temperatures, which still has the hot gas partially released in the high-pressure turbine 15, combustion takes place in the second combustion chamber 17, which combustion is based on autoignition. The hot gas reheated in the second combustion chamber 17 is then expanded in a multistage low-pressure turbine 18.

The low-pressure turbine 18 comprises a plurality of rows of blades and vanes arranged alternately in the flow direction, which are arranged alternately. The vanes of the third directional blade row in the flow direction are in Fig. 1 provided with the reference numeral 20 '.

With the high hot gas temperatures in gas turbines of the new generations, it has become indispensable to sustainably cool the guide vanes and rotor blades of the turbine. For this purpose, a gaseous cooling medium (eg compressed air from the compressor of the gas turbine is shown or supplied with steam.) In all cases, the cooling medium is sent through cooling channels formed in the blade (often in serpentines) and / or at different points of the blade through holes (holes, Slits) to form a cooling film, in particular on the outside of the blade (film cooling) An example of such a cooled blade is in the document US-A-5,813,835 described and illustrated.

As part of the blade cooling is often the trailing edge of the blade cooled by the cooling medium by a on the pressure side of the blade in front of the Rear edge arranged, substantially parallel to the trailing edge extending slot-shaped opening (cooling slot) is ejected and sweeps over the trailing edge and lying between the opening and trailing edge region of the blade surface. Such cooling of the trailing edge is in Fig. 3 the US-A-5,813,835 represented by the reference numerals 208 and 210.

EP 1 630 350 A1 . US 5,358,379 A. and EP 1 101 898 A2 disclose vanes with means for reducing thermal stresses. EP 1 630 350 A1 discloses all features of the preamble of claim 1. US 2005/232777 discloses a similar slot as claimed in claim 1 on a blade.

The guide vane 20 'according to Fig. 1 has an airfoil extending radially between a blade head and a cover plate, wherein the airfoil extends transversely to the direction of the hot gas flow having a pressure side and a suction side between a leading edge and a trailing edge and on the pressure side before the trailing edge extending parallel to the trailing edge Cooling slot of the type described above is provided, through which a cooling medium over the entire length of the guide vane exit from the vane and can cool the trailing edge of the vane.

By virtue of the cooling slot which is integrated into the airfoil and in particular produced by casting, the trailing edge of the vane must be made comparatively thin. If, during operation, the blade end of the vane, which abuts the rotor as a result of sealing, is subjected to considerable mechanical forces on the trailing edge of the airfoil, resulting in cracks at the junction between the trailing edge and the inner platform and due to the small thickness of the trailing edge so that an undesirable limitation of the life can lead.

Presentation of the invention

The invention aims to remedy this situation. It is therefore an object of the invention to provide a guide vane of the type mentioned, in which the disadvantages of the previous solution can be avoided, and which is characterized overall by a not impaired due to the thin trailing edge life.

The object is solved by the entirety of the features of claim 1. Essential for the inventive solution is that means for reducing the thermal stresses are provided below the trailing edge and the cooling slot on the inner platform. By this means it is ensured that without changing the blade geometry, in particular without increasing the wall or material thicknesses, solely by a "decoupling" between the blade head and blade trailing edge, the life of the vane can be favorably influenced.

According to the invention, the means for reducing the thermal stresses comprise a slot passing through the inner platform, oriented substantially parallel to the plane of the inner platform and having a cross-sectional profile of the shape of a keyhole, with a wall portion with parallel sides and one on the bottom arranged the slot, round, in particular circular, end portion.

Another embodiment is characterized in that the blade head has a quadrangular base surface, that the trailing edge opens into the blade head with the cooling slot arranged in front of it at one of the four corners, and that the slot intersects this corner. Preferably, the end portion of the slot encloses an acute angle with the side walls of the inner platform, in particular between 30 ° and 40 °.

The slot has a width of less than 1 mm in the region of the wall section, and the end section is formed circular with a radius greater than 1 mm. In particular, the slot portion of the wall portion has a width of about 0.4 mm, and the end portion is formed circular with a radius of about 1.25 mm.

According to a further embodiment of the invention, the cooling slot in the guide vane is produced by casting.

The guide vane according to the invention is advantageously used in a gas turbine, wherein the vane is arranged in a turbine of the gas turbine.

The gas turbine is preferably a gas turbine with sequential combustion, which has a first combustion chamber with a downstream high-pressure turbine and a second combustion chamber with a downstream low-pressure turbine, wherein the guide vane is arranged in the low-pressure turbine. In particular, the low-pressure turbine has a plurality of rows of guide vanes downstream of one another in the flow direction, and the guide vane is arranged in a middle row of guide vanes.

Brief explanation of the figures

Fig. 1

den prinzipiellen Aufbau einer Gasturbine mit sequentieller Verbrennung nach dem Stand der Technik;

Fig. 2

in einer perspektivischen Seitenansicht eine Leitschaufel für die dritte Leitschaufelreihe in der Niederdruckturbine einer Gasturbine mit sequentieller Verbrennung nach Fig. 1 gemäss einem bevorzugten Ausführungsbeispiel der Erfindung;

Fig. 3

eine andere perspektivische Seitenansicht der Schaufel aus Fig. 2;

Fig. 4

in einem Ausschnitt den Blick auf die innere Plattform entgegen der Strömungsrichtung (IV in Fig. 2);

Fig. 5

den Schnitt durch die innere Plattform in der Ebene V-V in Fig. 4, und

Fig. 5a

das prinzipielle Querschnittsprofil des Schlitzes in der inneren Plattform.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. All elements not essential to the immediate understanding of the invention have been omitted. The same elements are provided in the various figures with the same reference numerals. The flow direction of the media is indicated by arrows. Show it:

Fig. 1

the basic structure of a gas turbine with sequential combustion according to the prior art;

Fig. 2

in a perspective side view of a guide vane for the third row Leitschaufelreihe in the low-pressure turbine of a gas turbine with sequential combustion after Fig. 1 according to a preferred embodiment of the invention;

Fig. 3

another perspective side view of the blade Fig. 2 ;

Fig. 4

in a section of the view of the inner platform against the flow direction (IV in Fig. 2 );

Fig. 5

the section through the inner platform in the plane VV in Fig. 4 , and

Fig. 5a

the basic cross-sectional profile of the slot in the inner platform.

Ways to carry out the invention

In Fig. 2 and 3 For example, in various perspective side views, a third vane row vane in the low pressure turbine of a sequential combustion gas turbine is shown in FIG Fig. 1 illustrated according to a preferred embodiment of the invention. The vane 20 comprises a curved in space airfoil 22 extending in the longitudinal direction (in the radial direction of the gas turbine) between a blade head 23 and a cover plate 21 and extends in the direction of the hot gas stream 30 from a leading edge 27 to a trailing edge 28. Between the two edges 27 and 28, the airfoil 22 is outwardly through a pressure side 31 (in Fig. 2 facing the viewer) and an (opposite) suction side 32 (in Fig. 3 facing the viewer) limited. On the pressure side 31, a cooling slot 29 extending parallel to the trailing edge 28 is arranged shortly before the trailing edge 28, through which cooling air exits from the blade interior and cools the blade area between the cooling slot 29 and the trailing edge 28 and the trailing edge 28 itself. The vane 20 is secured by means of the formed on the top of the cover plate 21 hook-shaped fastening elements 24 and 25 on the turbine housing, while it rests sealingly with the blade head 23 on the rotor. In the side surfaces of the cover plate 21, sealing grooves 26 are arranged, which receive strip seals for sealing the gaps between adjacent guide vanes.

In the blade head 23, a slot 33 is arranged substantially parallel to the platform plane, the in Fig. 4 can be seen more accurately. The slot 33 has according to Fig. 5a a keyhole-like cross-sectional profile having a wall portion 33a (with parallel sides or walls) of width b and a circular end portion 33b of radius r placed at the bottom of the slot 33. The width b of the wall portion 33a is less than 1 mm, preferably about 0.4 mm, while the radius r of the end portion 33b is greater than 1 mm, preferably about 1.25 mm. The aim in the dimensioning of the slot is to reduce the mechanical load on the trailing edge of the thermally bending blade head 23, without creating stress concentrations at the bottom of the slot 33 and large volumes in the slot, which result in additional thermal stresses when filled with cooling air could.

How out Fig. 5 can be seen, the blade has a square (in particular diamond-shaped) base. The trailing edge 28 with the cooling slot 29 arranged in front opens at one of the four corners (in FIG Fig. 5 bottom left) in the blade head 23 a. The slot 33 intersects this corner with a depth which ensures a sufficient distance of the slot bottom to the trailing edge, wherein the end portion 33b of the slot 33 with the side walls of the inner platform 23 includes an acute angle w, in particular between 30 ° and 40 ° ,

Essential for the invention in the illustrated embodiment is a slot through the blade head 23, which changes the resulting due to thermal bending of the end-side part voltage flow and relieves the thin trailing edge of the blade with the pressure-side edge cooling. The baseline (end portion 33b) of the slot is not perpendicular to the trailing edge line of curvature, and makes an acute angle with the side surface of the blade head 23 to balance the stresses at both ends of the slot, at the side and rear sides thereof. The slot has the cross-sectional contour of a "keyhole" to reduce the stresses at the bottom of the slot and minimize the overall volume of the slot because a large cavity filled with cooling air would increase the temperature gradient and thus the stresses on the trailing edge.

The invention can be used with all turbine vanes. It is preferably used in large stationary gas turbines with sequential combustion, such as e.g. the Applicant's GT24 / 26, used in the third row of vanes of the low-pressure turbine.

Due to the voltage-reducing slot, it is possible to achieve the desired service life, even with guide vanes with a thin trailing edge, as they are in the case of cooling on the pressure side by an integrated cooling slot.

LIST OF REFERENCE NUMBERS

10

gas turbine

11

compressor

12.16

fuel supply

13

EV burner

14.17

combustion chamber

15

High-pressure turbine

18

Low-pressure turbine

19

axis

20.20 '

vane

21

cover plate

22

airfoil

23

Blade head (shroud)

24.25

Fastening element (hook-shaped)

26

seal groove

27

leading edge

28

trailing edge

29

cooling slot

30

Hot gas flow

31

pressure side

32

suction

33

slot

33a

wall section

33b

End section (bore)

b

Width (slot)

r

Radius (end section)

w

corner

Claims (9)

1. Guide blade (20) for a gas turbine (10), in particular for the low-pressure turbine (18) of a gas turbine (10) with sequential combustion,
   which guide blade (20) comprises a turbine blade (22) extending in the radial direction between a blade tip (23) and a cover plate (21),
   wherein the turbine blade (22) extends transversely to the direction of the hot gas stream (30) between a leading edge (27) and a trailing edge (28) and has a pressure side (31) and a suction side (32), and
   wherein a cooling slot (29) is provided on the pressure side (31) in front of the trailing edge (28) and running parallel to the trailing edge (28), through which slot a cooling medium can flow out from the guide vane (20) over the entire length of the guide vane (20) and thus the trailing edge (28) of the guide vane (20) can be cooled, wherein means (33; 33a, 33b) for reducing thermal stresses are provided on the blade tip (23) below the trailing edge (28) and the cooling slot (29),
   characterised in that the means for reducing thermal stresses comprise a slot (33; 33a, 33b) running through the blade tip (23),
   that the slot (33; 33a, 33b) is oriented substantially parallel to the plane of the blade tip (23), and
   that the slot (33; 33a, 33b) has a cross-sectional profile in the form of a keyhole with a wall portion (33a) with parallel sides and a round, in particular circular end portion (33b) arranged at the base of the slot (33; 33a, 33b).
2. Guide blade according to claim 1, characterised in that the blade tip (23) has a quadrangular base area, that the trailing edge (28) with the cooling slot (29) arranged in front of it opens into the blade tip (23) at one of the four corners, and that the slot (33; 33a, 33b) intersects this corner.
3. Guide blade according to claim 2, characterised in that the end portion (33b) of the slot (33; 33a, 33b) forms an acute angle (w), in particular an angle between 30° and 40°, with the side walls of the blade tip (23).
4. Guide blade according to claim 2 or 3, characterised in that in the region of the wall portion (33a), the slot (33; 33a, 33b) has a width (b) of less than 1 mm, and the end portion (33b) is formed circular with a radius (r) of more than 1 mm.
5. Guide blade according to claim 4, characterised in that in the region of the wall portion (33a), the slot (33; 33a, 33b) has a width (b) of around 0.4 mm, and the end portion (33b) is formed circular with a radius (r) of around 1.25 mm.
6. Guide blade according to any of claims 1 to 5, characterised in that the cooling slot (29) is produced in the guide blade (20) in a casting process.
7. Gas turbine (10) with a guide blade according to any of claims 1 to 6, characterised in that the guide blade (20) is arranged in a turbine (15, 18) of the gas turbine (10).
8. Gas turbine according to claim 7, characterised in that the gas turbine (10) is a gas turbine with sequential combustion which has a first combustion chamber (14) with a downstream high-pressure turbine (15) and a second combustion chamber (17) with a downstream low-pressure turbine (18), and that the guide blade (20) is arranged in the low-pressure turbine (18).
9. Gas turbine according to claim 8, characterised in that the low-pressure turbine comprises several rows of guide blades arranged behind each other in the flow direction, and that the guide blade (20) is arranged in a middle guide blade row.

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