EP2611990B1 - Turbine blade for a gas turbine - Google Patents

Description

The invention relates to a turbine blade with an airfoil which can be flowed around by a hot gas and which comprises a suction sidewall and a pressure sidewall which extend in the direction of flow of the hot gas from a common leading edge to a trailing edge, wherein at the rear edge at least one opening for blowing out a previously cooling the blade Coolant is arranged, which is in flow communication with at least one opening with a arranged in the airfoil cavity by means of a channel, wherein the channel is also bounded by an inwardly facing surface of the suction side wall and an inwardly facing surface of the pressure side wall and for adjusting the from the Opening exiting coolant amount is provided a throttle element.

An aforementioned turbine blade and a casting core for producing such a turbine blade are, for example, from WO 2003/042503 A1 known. The known turbine blade has a cooled trailing edge at which a plurality of openings for blowing out the cooling air by interposed webs = which are also known in English as "tear drops" - are separated from each other. The arranged at the trailing edge of a common cavity is preceded by in the three rows of columnar sockets - also known under the name "Pin-Fins" - are arranged, which increases the heat transfer of them passing cooling air and to increase the Pressure loss are provided there.

The casting core required for producing such a turbine blade is shown in FIG WO 2003/042503 A1 shown in perspective. The space occupied by the casting core remains after production of the cast turbine blade as Cavity in the turbine blade, wherein arranged in the casting core openings are filled with casting material. In this respect, the casting core represents the negative image of the interior of the turbine blade.

The from the WO 2003/042503 A1 known pin-fins have a cylindrical shape and connect the opposite inner surfaces of the suction side wall and pressure side wall of the blade of the turbine blade.

It is known to set the exiting at the trailing edge of the turbine blade cooling air amount by a suitable choice of the maximum pressure drop and / or the smallest, to be flowed through by the cooling air cross-sectional area near the trailing edge. However, this procedure can lead to casting cores, in which the openings provided at the casting core trailing edge become so large that only comparatively thin separating webs remain between them. During the handling of the casting core, however, the casting core may break precisely at this point, so that it is subsequently useless.

Furthermore, from the WO 2003/042503 A1 C-shaped guide elements for cooling air arranged in turning areas of cooling channels are known, which are intended to bring about low-loss deflection and guidance of the cooling air into downstream areas.

Next is from the EP 1 091 092 A2 an air-cooled turbine blade known. In order to achieve a particularly efficient cooling of a hollow-walled suction or pressure side of the airfoil, pins are arranged in the form of a grid in the cavity of the double wall. The pins have a diamond shape in principle, with their corners rounded and their edges are concave inward. Between the pins thus creates a network of passages for cooling air, each having a narrowed inlet and a narrowed outlet opening, between which a diffuser and nozzle section is arranged.

The sections aim to slow down and accelerate the cooling air for efficient cooling.

Furthermore, from the US 5,752,801 an internally cooled turbine blade known whose trailing edge cooling channels are designed zigzag by cast c-shaped ribs. This can be achieved a better cooling effect. In addition, the casting cores required for the production can be stiffened with it.

Further, from the documents EP 1 327 747 and WO 2010/086419 Turbine blades with trailing edge channels known in which staggered tubulators or ribs are arranged.

The object of the invention is therefore to provide an initially mentioned turbine blade for a gas turbine, which is efficient and sufficiently coolable with the smallest possible amount of coolant.

The object directed to the turbine blade is achieved with a turbine blade according to the features of claim 1, with advantageous solutions being specified in claims 2 to 6.

The turbine blade for a gas turbine comprises an airfoil which can be flowed around by a hot gas and which comprises a suction sidewall and a pressure sidewall which extend from a common leading edge to a trailing edge in the direction of flow of the hot gas, at least one opening for blowing out the airfoil at or in the trailing edge previously cooling coolant is arranged, which is at least one opening in fluid communication with an arranged in the airfoil cavity by means of a channel, wherein the channel is also bounded by an inwardly facing surface of the suction side wall and an inwardly facing surface of the pressure side wall and adjusting the is provided from the opening exiting cooling air amount, a throttle element, according to the invention, the throttle element upstream - in relation to the flow direction of the channel - the respective opening is arranged and comprises two surveys, each a n one of the two inwardly facing surfaces are arranged.

In other words, the throttle element comprises on the inwardly facing surfaces arranged elevations which extend transversely to the flow direction of the channel and between which the minimum flow cross-section of the channel is arranged. To determine the minimum flow cross section, the minimum vertical distance between each of the neutral fibers of the coolant flow and one of the two side surfaces in the cooling channel is to be detected.

The invention is based on the finding that the coolant consumption with the proposed construction is particularly simple and precisely adjustable, in which the throttle element is arranged in the blade interior upstream of the trailing edge opening. In this case, the throttle element is to be formed by two mutually related elevations, each of which are arranged on the inwardly facing surface of the suction side wall and pressure side wall. None of the elevations connects the suction side wall with the pressure side wall. This embodiment of the throttle element is particularly advantageous for turbine blades produced in the casting process. As is known, turbine blades are usually produced in casting processes in which so-called lost casting cores are used to produce the internal cooling system. The production of these cores is usually done with the help of a core tool. The core tool comprises two slider elements which can be moved towards and away from each other. When pushed together, these slide elements surround a cavity which has the same contour as the cavity of the turbine blade to be cast. To produce the casting core, the casting core material is inserted into the cavity of the slider elements. After the casting core material has dried, the casting core is available for producing the turbine blade.

According to the invention, the slide elements for producing a first prototype of the turbine blade series to be produced are designed such that in the turbine blade prototype to be produced the throttling, minimum distance between the surveys is definitely smaller than the theoretically required. The first turbine blade prototype produced therewith is then subjected to a coolant flow measurement. Desirably, due to the first time too small distance between the surveys, the throttle effect is too large, which initially leads to a low flow rate. Depending on the result of the flow measurement then the slide elements are changed. Their elevations are slightly changed, which increases in the collapsed state whose minimum distance. Subsequently, another casting core is produced with it. With this another turbine blade prototype is produced, the flow rate is then determined again and compared with the desired amount. If the determined flow rate corresponds to the desired flow rate, the manufacturing process of the slide elements is completed. The slide elements are then designed so that casting cores are always produced with them, which can be used to manufacture serial turbine blades in series. In the event that the last determined flow rate does not correspond to the desired flow rate, all steps for the production of a further turbine blade prototype are again carried out, the minimum distance of which is slightly larger than the previous prototype.

The particular advantage of the proposed solution is that each of the two slides can be processed by itself - such as by grinding the survey arranged thereon - without fundamentally changing the construction of the turbine blade and its cooling system. It is possible that only one of the slide elements or both slide elements are processed during an iteration step.

This method is also particularly suitable for modifications of existing blades in the event that more cooling air is needed for sufficient cooling. In this case, there are only minor changes in the blade design required. An additional qualification because of an otherwise required casting change is therefore not necessary.

In this case, the two elevations - seen in the flow direction of the cooling channel - offset from one another. By staggered placement, the vertical distance between the inner surface of the pressure sidewall and the inner surface of the suction sidewall can be further reduced, resulting in particularly narrow trailing edge regions of airfoils. This reduces aerodynamic losses in hot gas flowing around the airfoil.

Overall, the invention leads to the reduction of the scrap rate in the manufacture of turbine blades, which significantly improves the production costs and the production time of turbine blades.

Advantageously, that elevation, which is arranged on the inwardly facing surface of the pressure side wall, arranged downstream of that elevation, which is arranged on the inwardly facing surface of the suction side wall. This construction forces coolant flow in the channel, which flows more intensively past the inwardly facing surface of the suction sidewall. As a result, in particular with the so-called cut-back trailing edges, an extended film cooling effect of the unprotected end of the suction-side trailing edge can be achieved, which reduces wear phenomena there and extends the service life of the turbine blade.

Preferred dimensions, a plurality of openings are arranged at the trailing edge, wherein the cooling channel jointly connects a plurality of openings with the cavity.

If the elevations are formed as ribs, with the help of this angular contour of the inwardly facing surfaces of the side walls of the airfoil in operation and turbulence be generated in the coolant. On the one hand, these turbulences can contribute to the throttle effect and, on the other hand, to increase the heat transfer due to more turbulent coolant flow.

The interior of the turbine blade proposed by the invention can be used both for turbine blades with (for the side walls) common trailing edge and for turbine blades with a so-called cut-back trailing edge.

A further advantageous embodiment of the invention will be explained in more detail with reference to the drawing.

FIG 1

eine Turbinenlaufschaufel in einer perspektivischen Darstellung,

FIG 2

einen Längsschnitt durch den Bereich der Hinterkante der aus dem Stand der Technik bekannten Turbinenlaufschaufel,

FIG 3

einen Querschnitt durch den Hinterkantenbereich einer erfindungsgemäßen Turbinenschaufeln nach einer ersten Ausgestaltung und

FIG 4

einen Querschnitt durch den Hinterkantenbereich einer erfindungsgemäßen Turbinenschaufeln nach einer zweiten Ausgestaltung.

Show it:

FIG. 1

a turbine blade in a perspective view,

FIG. 2

a longitudinal section through the region of the trailing edge of the known from the prior art turbine blade,

FIG. 3

a cross section through the trailing edge region of a turbine blades according to the invention according to a first embodiment and

FIG. 4

a cross section through the trailing edge region of a turbine blades according to the invention according to a second embodiment.

Identical features are provided in all figures with identical reference numerals.

A gas turbine blade 10 relating to the invention is shown in FIG FIG. 1 shown in perspective. The gas turbine blade 10 is according to FIG. 1 designed as a blade. The invention can also be used in a guide vane not shown a gas turbine. The turbine blade 10 comprises a cross-sectionally fir-tree-shaped blade root 12 and a platform 14 arranged thereon. The platform 14 is adjoined by an aerodynamically curved blade 16, which has a leading edge 18 and a trailing edge 20. Provided at the front edge 18 are cooling holes arranged as so-called "shower heads", from which a coolant flowing inside, preferably cooling air, can emerge. The airfoil 16 includes a - with respect FIG. 1 - Rear suction side wall 22 and a front side pressure side wall 24. Along the trailing edge 20 a plurality of openings 28 are provided, which are separated by interposed webs 30 from each other. The trailing edge 20 is designed as a so-called cut-back trailing edge, so that the openings 28 are located on the pressure side rather than centrally in the trailing edge 20th

FIG. 2 shows the interior of a turbine blade known in the prior art in a longitudinal section along a plane, spanned by a center line extending from the leading edge 18 to the trailing edge 20 of the airfoil 16, and the blade longitudinal direction extending from the blade root 12 to the blade tip extends.

In FIG. 2 are further to the right arranged the trailing edge openings 28 shown, between which the webs 30 are arranged. The webs 30 extend substantially parallel to a hot gas flow which, during operation, flows around the airfoil 16 from the front edge 18 to the rear edge 20. In FIG. 2 shown on the left is a plurality of arranged in a grid column or sockets 32 are provided. Both the sockets 32 and the webs 30 extend from an inner surface 34 of the suction side wall 22 to an in FIG. 2 Consequently, the sockets 32 are arranged in a cavity 38 of the turbine blade 10, which is bounded laterally by the suction side wall 22 and the pressure side wall 24.

When using the turbine blade 10 in a gas turbine, a coolant, for example cooling air 40 or cooling steam, flows through the cavity 38 during operation. In general, the in FIG. 2 not shown part of the turbine blade 10 formed in the interior so that the field of sockets 32 is substantially uniformly flowed through by cooling air 40. The uniform flow of the arranged in grid base 32 is shown by the arrows marked 40. The cooling air 40 impinges on individual pedestals 32 and is thereby deflected by them, the main flow direction of which remains essentially unchanged. This creates 40 turbulences in the cooling air. The introduced from the hot gas in the blade walls 22, 24 heat is passed from these further into the base 32. There, the cooling air 40 impinging on the base 32 absorbs the heat and transports it. After the cooling air 40 has flowed through the base field, this enters into passages 41 which connect the cavity 38 with the openings 28. After flowing through the passages 41, the cooling air 40 passes out of the turbine blade 10 through the openings 28 and mixes with the hot gas flowing around the blade 16.

In order to set the quantity of coolant leaving the openings 28, elevations 42, 44 (FIG. 2) are provided on the inner surfaces 34, 36 of the suction side wall 22 and the pressure side wall 24, respectively. 3, FIG. 4 ) intended. One (42) of the two elevations 42, 44 is arranged on the inner surface 34 or part thereof, the other (44) of the two elevations 42, 44 is located on the inner surface 36 or part of this. The inner surfaces 34, 36 define a cavity 38 and a cooling channel 46, which connects the cavity 38 with the openings 28. It is possible that cavity 38 and channel 46 merge into one another. According to the invention, the minimum distance between the inner surface 34 and the inner surface 36 in the region of the two elevations 42, 44 is now provided. This is - in FIG. 3 with respect to the cross section shown therein by the trailing edge 20 of the turbine blade 10 - the neutral fiber 47 of the cooling channel 46, which always has the same vertical distance from the inner surface 34 and inner surface 36. The minimum distance A forming the throttle element is located between the two elevations 42, 44, whereby they are in relation to one another.

The elevations 42, 44 replace neither the base 32 nor the webs 30th

According to FIG. 3 The elevations 42, 44 extend along the blade longitudinal direction (perpendicular to the sheet plane) over the entire height of the cooling channel 46. The contour of the elevations 42, 44 are, as in the cross section shown in FIG FIG. 3 , Such that they allow a stepless and edge-free course of the cooling channel in the flow direction of the coolant to the trailing edge opening 28 out. In this case, the cooling channel 46 converges. Alternatively it can be provided that the elevations are also designed in the form of ribs, as in FIG. 4 shown.

According to FIG. 4 the elevations 42, 44 on a rib-shaped contour with a height H ₁ and H ₂ .

When manufacturing a first prototype of the turbine blade according to the invention the heights H ₁ and H _{2 are} comparatively large, so that a cooling air consumption can be determined, which is below the desired or predetermined consumption. By modifying the core tool, ie the corresponding slide elements, further prototypes can be produced successively, which always consume somewhat more coolant than the previously produced prototype due to reduced rib heights H ₁ , H ₂ . Each iteration comprises producing a turbine blade with a defined rib height H ₁ and H ₂ and determining the coolant consumption of the corresponding turbine blade prototype. As soon as a coolant consumption is determined, which corresponds to the desired or predetermined amount, the production of the slide elements is finished, so that with the then available core tool Gusskerne and thus turbine blades with the desired coolant consumption can be produced to an increased extent, which significantly reduces the reject rate.

In fact, with the proposed embodiment, a turbine blade 10 is provided which allows a simple and inexpensive test phase during the tooling phase to provide, after completion of the iterations for a series of turbine blades 10, precisely manufactured core tooling.

Furthermore, it is even possible that the casting cores required for casting the turbine blade 10 according to the invention more rarely break during handling than the casting cores known from the prior art.

Of course, it is also possible that the throttle element instead of two surveys 42, 44 comprises only a single survey 44 (or 42), so that the flow rate determining minimum distance between a single survey 44 (or 42) and its opposite, then after inside facing surface 34 (or 36) of the suction side wall 22 (or the pressure side wall 36) is located. In this case, the opposing surface 34 or 36 may then also be designed flat in the region of the minimum distance, this embodiment not forming part of the invention.

Overall, the invention specifies a turbine blade 10 whose amount of coolant 40 flowing out of the trailing edge 20 is set comparatively simply and exactly immediately upon casting of the turbine blade 10, without requiring reworking of the cast turbine blade 10 with regard to adjusting the coolant consumption. To achieve this, it is proposed that elevations 42, 44 are located on the inner surfaces 34, 36 of the suction side wall 22 or pressure side wall 24, between which the throttle element is located, by means of which the amount of coolant flowing out is set. This arrangement allows the simple production of a core tool with which the casting cores required for casting the turbine blade 10 can always be produced many times with the desired accuracy.

Claims (6)

1. Turbine blade (10) for a gas turbine,
   comprising a main blade part (16), around which a hot gas can flow and which comprises a suction-side wall (22) and a pressure-side wall (24) which extend in the direction of flow of the hot gas from a common leading edge (18) to a trailing edge (20),
   wherein at least one opening (28) for blowing out a coolant (40) which cools the main blade part (16) beforehand is arranged on the trailing edge (20), which at least one opening is fluidically connected to a cavity (38) arranged in the main blade part (16) by means of a channel (46),
   wherein the channel (46) is also delimited by an inwardly facing face (34) of the suction-side wall (22) and by an inwardly facing face (36) of the pressure-side wall (24) and a throttling element is provided for setting the quantity of coolant emerging from the opening (28), characterized in that
   the throttling element comprises two elevations (42, 44) upstream - in relation to the throughflow direction of the channel (46) - of the opening (28) in question, which are arranged offset in relation to one another - as seen in the throughflow direction of the cooling channel (46) - and between which there is arranged the minimum throughflow cross section of the channel, wherein the two throttling elements are each arranged on one of the two inwardly facing faces (34, 36).
2. Turbine blade (10) according to Claim 1,
   in which that elevation (42, 44) which is arranged on the inwardly facing face (36) of the pressure-side wall (24) is arranged downstream of that elevation (42, 44) which is arranged on the inwardly facing face (34) of the suction-side wall (22).
3. Turbine blade (10) according to Claim 1 or 2,
   in which a plurality of openings (28) are arranged on the trailing edge (20) and the cooling channel (46) collectively connects a plurality of openings (28) to the cavity (38).
4. Turbine blade (10) according to one of the preceding claims,
   in which the elevations (42, 44) are in the form of fins.
5. Turbine blade (10) according to one of Claims 1 to 3,
   in which the cooling channel (46) converges and the two elevations (42, 44) are situated on the inwardly facing faces (34, 36) with a continuous and edge-free profile.
6. Turbine blade (10) according to one of the preceding claims,
   in which the openings (28) are provided on the pressure wall side.

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