EP1331361A1 - Turbine blade and casting device for producing a turbine blade - Google Patents

Abstract

Turbine blade (1) comprises a profiled blade (2) extending along a blade axis (4) and on which is molded in an end region a platform (6) extending perpendicular to the blade axis. The platform has an outer edge (14) which is thicker than the platform base (12). The side wall (16) of the outer edge facing toward the blade axis is angled. A hook base (8) is molded over the platform on the end region of the blade. An Independent claim is also included for a casting system for producing the above turbine blade. Preferred Features: The outer edge of the platform is provided in its base region with a number of cooling bores (20) opening on the outlet side into a common cooling gap (22).

Description

The invention relates to a turbine blade with a profiled, along a blade axis extended Airfoil, to the end one transverse to the blade axis extending platform is formed. It concerns Furthermore, a casting system for producing such a turbine blade.

Gas turbines are used in many areas to drive generators or used by work machines. It is the Energy content of a fuel for generating a rotational movement used a turbine shaft. The fuel will burned in a combustion chamber, being used by an air compressor compressed air is supplied. That in the combustion chamber produced by the combustion of the fuel, under high Pressure and high temperature working medium is doing via a turbine downstream of the combustion unit led, where it relaxes work.

To generate the rotational movement of the turbine shaft are in this case a number of usually in blade groups or blade rows of combined blades arranged, via a momentum transfer from the flow medium drive the turbine shaft. For guiding the flow medium in the turbine unit are also usually between adjacent blade rows with the turbine housing connected Leitschaufelreihen arranged. The turbine blades, in particular the guide vanes, usually have for the suitable guidance of the working medium a profiled, along a blade axis extended blade on, at the end for attachment of the turbine blade on the respective support body a transverse to Blade axis extending, in at least one end as Hook base trained platform is formed.

To achieve a particularly favorable efficiency Such gas turbines for thermodynamic reasons usually for particularly high outlet temperatures of the Combustion off and in the flowing into the turbine unit Working medium from about 1200 ° C to about 1300 ° C. designed. At such high temperatures, the components are the gas turbine, in particular the turbine blades, comparatively exposed to high thermal loads. Around Even with such operating conditions a high reliability and a long life of the respective components to ensure the affected components are common cooled formed.

For this purpose, the turbine blades are common in modern gas turbines designed as a so-called hollow profile. The profiled Airfoil features in its interior too referred to as vane core cavities in which a Cooling medium can be performed. By the thus formed Coolant channels is thus an admission of the thermally stressed areas of the respective Blade with coolant allowed. A particularly cheap Cooling effect and thus a particularly high level of operational safety is achievable by the coolant channels a comparatively large spatial area inside the respective Occupy the airfoil, and by the coolant as possible close to the respective, the hot gas exposed surface is guided. On the other hand, in such a design sufficient mechanical stability and resilience can ensure the particular turbine blade flowed through several channels, wherein inside the blade profile a plurality of coolant, each other by comparatively thin partitions separate coolant channels are provided.

Such turbine blades are usually by casting manufactured. For this purpose, in a first casting step, an in its contour adapted to the desired blade profile mold poured out with wax. For the production of the flow channels for the coolant to be poured in the mold so-called core elements, for example made of ceramic material arranged after the casting from the Wax model can be removed for the blade body, so that the desired for the coolant channels cavities arise. The wax model obtained in the first casting step subsequently becomes by repeated immersion with a ceramic coating Provided. Once this, if necessary after several Dipping operations, has a sufficient thickness is burned out the ceramic model provided with the wax model, where the ceramic solidifies and the wax burned out becomes. This creates a ceramic mold for the blade, in which also the core elements for cooling channels or similar. comprises are. In a second casting step, this ceramic casting mold becomes poured out with blade material. For the production of Wax model and in particular of the airfoil and the molded structural parts such as the Platform or a hook base are shaped accordingly Mask elements or slider such in the mold arranged for the first casting step that during the casting process one of the blade shape to be produced corresponding Cavity for receiving the wax remains.

The invention is based on the object, a turbine blade of the abovementioned type, on the one hand for a designed especially high thermal and mechanical strength is, and on the other hand, a reliable cooling with comparatively low demand for coolant is. Furthermore, a for the production of the turbine blade suitable casting system can be specified.

With respect to the turbine blade, this object is achieved according to the invention solved by the platform one compared to Platform bottom has thickened outer edge, whose the Airfoil facing side wall based on the blade axis is guided bevelled.

The invention is based on the consideration that the turbine blade for a particularly favorable manufacturability in should be configured monocrystalline construction. A turbine blade in single-crystal construction is already due to the material properties comparatively high load capacity. A monocrystalline construction is in particular by the use of also referred to as a slider mask elements cheaper for casting, especially as an alternative usable so-called lost inserts for nucleation polycrystalline material would contribute and thus for monocrystalline blades are not usable. The turbine blade should thus be designed in their contouring be that in a relatively simple manner positioning and after casting a removal of the formation of Platform recesses used masking elements or slides is possible. Even with compliance with these boundary conditions However, the turbine blade should be for a comparatively be designed low demand for coolant. This is achievable, inter alia, by recording the thermal Load-designed platform comparatively thin-walled and thus designed with low material consumption is. This is also achievable under the specified conditions, by prior to casting the turbine blade a plurality is arranged by mask elements in the mold, wherein a mask element for reducing the platform thickness in the for this intended space area can be introduced. To the corresponding propulsion in this area also bypassing from above the platform to be arranged moldings and also in a room area especially close to the vane center into it, the turbine blade is bevelled Side walls in the area of the arranged on the platform Outer ring designed.

For a particularly high mechanical and thermal load capacity the turbine blade is advantageously a function separation between the for the recording of the mechanical Load on the one hand and for absorbing the thermal load on the other hand provided for components. For this purpose, in an advantageous embodiment of the blade of the Turbine bucket in the end area above the platform a hook base formed. Namely with turbine blades at more reliable mechanical suspension a particularly high stability to allow for thermal stress, are advantageously in the area of entanglement of the turbine blade the platform and the hook base from each other structurally decoupled trained. It serves to the Airfoil molded platform for compensation only the thermal load of that in the interior the gas turbine guided hot working medium without it a mechanical load would be connected. For a comparatively low cooling requirement for this component is the Platform preferably comparatively thin-walled, which is particularly made possible by the fact that the platform is not exposed to any mechanical stress. The mechanical load is carried out via a above the Platform arranged hook base, which is in a corresponding Structural part hung on the turbine wall or the turbine shaft is. The hook base is expediently for the assumption of mechanical stress sufficiently dimensioned designed, with an impact on the hook base avoided by thermal stress through the platform is. The cooling requirement for the hook base is thus comparatively low.

The outer edge of the platform can in particular one with regard to guided on the blade axis substantially rectilinear, so aligned in cross section parallel to this have outer side wall. In such an embodiment the outer edge is thus in its platform floor facing area performed comparatively thick and Tapered in cross-section steadily up to his Platform floor facing away from the end. To be reliable in this case To ensure cooling of all room areas of the outer edge, should be special funds for an admission the comparatively thick lower space of the outer edge be provided. This is the outer edge of the platform advantageously in its bottom area with a number provided by cooling holes. For a particularly simple Operation, the cooling holes are in further advantageous Design on the output side in a common Cooling gap led.

The turbine blade can act as a blade for a turbine be provided. Preferably, however, the turbine blade as a guide vane for a gas turbine, in particular for a stationary gas turbine trained.

The casting system for producing such a turbine blade directed task is solved with one in one Mold positionable first mask element having a an interface of the platform floor predetermining recess has, and in which a substantially flat trained second mask element in one at an angle of more as 10 ° and less than 80 °, preferably less than 60 ° tilted against the boundary surface predetermining recess Directed displaced.

Through the interaction of these two mask elements, of which the first mask element as a circumferential slide and the second mask element also referred to as a pocket slide is to make a platform bag with bevelled side walls even without using a "lost Use. "The casting system is thus suitable in particular for the production of single-crystalline turbine blades, especially because of the conscious renunciation of the use of "lost missions" a nucleation for polycrystalline Areas is kept very low. For the production a substantially planar formed platform floor has the second mask element advantageously one compared to its base by an adapted Angle of more than 10 ° and less than 80 ° tilted Face on, which together with the recess of the first Mask element forms a casting mask for the platform floor.

The advantages achieved by the invention are in particular in that through the obliquely guided side wall of Platform bag, which by the in the first mask element or the circumferential slide arranged, obliquely in the circumferential direction sitting second mask element or the separate slide produced is an undercut of the ribbing of the profile can be avoided for entanglement. This is both Mask elements removable after completion of the casting process, so that the use of a "lost mission" is not required. By in the outer edge of the platform arranged cooling holes is also a reliable Cooling of all room areas of the platform with comparatively low coolant requirement allows, in particular by the comparatively broad base of the outer edge of the Platform the significant for coolant consumption impact-cooled Surface can be kept comparatively small. Due to the widening of the outer edge in the area of the platform floor is also comparatively in the operation of the turbine blade warm proportion compared to the colder part especially large, so that by impaired thermal expansions in the blade material induced voltages comparatively are kept low.

An embodiment of the invention will be described with reference to a Drawing explained in more detail. In it, the figure shows a turbine blade in longitudinal section together with schematically indicated Elements of a casting system.

The turbine blade 1 according to the figure has a profiled Airfoil 2, which extends along a blade axis. 4 extends. The blade 2 is suitable for influencing a flowing in an associated turbine unit Fluid medium curved and / or curved.

The turbine blade 1 in the embodiment is as a guide vane designed for a gas turbine; after the following but could also be a blade be designed. This is the end in the presentation after the figure upper end of the airfoil 2 at this is a transverse to the blade axis 4 extending platform 6 molded. In the sense of the representation after the figure is arranged above the platform 6 or overlying In addition, a hook base 8 is formed, which is not shown in detail Way is attachable to a turbine housing. The Hook base 8 is connected to an adjacent structural element in Intervention brought, so that in a particularly simple way a Attachment of the turbine blade 1 to a support body allows is. The turbine blade 1 is for use seen in the direction of flow of the working medium second guide vane row of the gas turbine provided so that the hook base 8 both front and back for a suspension is configured in a structural element.

The turbine blade 1 is for use in a thermal comparatively highly loaded space area of the gas turbine educated. On the one hand, this is a consistent functional Separation of the absorption of thermal loads and mechanical Loads of the turbine blade 1 by different Structural parts provided. This is through the separate Arrangement of the platform 6 and the hook base 8 guaranteed. The platform 6 is in fact the exclusive Recording of the gas turbine flowing through the hot Working fluid outgoing thermal load without the Platform 6 would be exposed to mechanical stress.

Rather, these are structurally from that of platform 6 decoupled hook base 8 recorded, in turn, however by the upstream platform 6 of only a comparatively is exposed to low thermal load. To use the turbine blade 1 in a thermally high burdened room area is even easier to relieve. the turbine blade 1 also formed coolable. That's it Airfoil 2 in the manner of an internal profiling with a Cavity 10 executed via which a coolant such as Cooling air or cooling is feasible.

The platform 6 has a comparatively thin-walled design Platform bottom 12, in its planar design essentially as a radiation shield for those of the Turbines flowing through working fluid output heat output acts. For a possible connection with surrounding Structural elements, for example by entanglement, and / or for a stiffening with regard to a self-supporting mechanical Stability is the platform 6 with a thickened Edge or a ribbing executed and points to it a thickened compared to the platform bottom 12 outer edge 14 on. By the outer edge 14 and the platform floor 12 is formed thus in the manner of a depression a so-called Platform pocket.

For a comparatively simple manufacturability of this Platform bag even without using "lost bets" is the turbine blade 1 designed such that even under Avoiding an undercut with the in the respective Spatial area protruding hook base 8 and thus underpassure the respective hook base 8, the reversible introduction a molding in the space area of the outer edge 14 recess formed together with the platform bottom 12 is possible. To ensure this is the the Blade axis 4 facing side wall 16 of the outer edge 14th With reference to the blade axis 4 seen chamfered out. The angle α characterizing this bevel is too more than 10 ° and less than 80 °, namely in the embodiment to about 45 °, chosen.

The outer edge 14 thus has in its platform bottom 12th facing bottom region a comparatively wide cross-section moving towards his from the platform ground 12 facing away from end 18 towards increasingly tapered. Currently at This upper end region of the outer edge 14 is thus due the comparatively small amount of material with comparatively simple means and in particular using a limited amount of coolant reliable cooled. To such a reliable cooling at only limited use of coolant even in its comparative widely executed, the platform bottom 12 facing lower area, the outer edge 14 is in this Area with a number of acted upon by a coolant Cooling holes 20 provided. These flow into theirs Outlet area in a common cooling gap 22nd

The turbine blade 1 is for a high thermal capacity designed for high mechanical strength. Is to the turbine blade 1 carried out in a single-crystal construction. In compliance with the intended boundary conditions is the turbine blade 1 thereto using a in the figure only partially illustrated casting system 30 produced by casting. The casting system 30, which is essentially when creating a wax model for the turbine blade 1 is used, comprises as a basic element a non-illustrated mold. In this mold a number of mask elements are positionable in their entirety one of the contour of the turbine blade to be produced 1 corresponding cavity release, in a subsequent step fillable with pourable wax is. Among others, for the contouring of the turbine blade 1 required elements includes the casting system 30, in particular a first mask element 32, which in the Art a circumferential slide can be used. The first mask element 32 includes besides other structure defining features one predetermining the interface of the platform floor 12 Recess 34.

The first mask element 32 is for final shaping for the platform 6 is supplemented by a second mask element 36, formed substantially flat and in the first mask element 32 is slidably guided. In the in the figure shown casting position protrudes the second mask member 36 so into the recess 34 of the first mask element 32, that only one to the final shape of the platform 6 adapted space area is released. This gives thus both the platform floor 12 and the outer edge 14 of the Platform 6 in front.

To after casting a wax model for the turbine blade 1 shows a simple removal of the mask elements 32, 36 by simply moving and without "lost missions" too enable, the second mask element 36 in one to one Angle β of about 45 ° with respect to the interface of the Platform floor 12 vorgebenden recess. 34 tipped, displaced by the double arrow 38 direction indicated arranged. In this way is a distance of the second Mask element 36 from the wax model of the turbine blade 1 after its casting by simply moving in the direction of Double Arrow 38 allows without passing through the hook base 8 would be impaired. The hook base 8 is for in its lateral extent dimensioned so that he indicated by the line 40 space area for the second Mask element 36 is not affected.

To the shape for the platform 6 overall suitable allow the second mask member 36 also has an opposite its base 42 by an angle γ of the embodiment about 45 ° tilted end face 44, the together with the recess 34 of the first mask element forms a casting mask for the platform floor 12.

After casting the wax model of the turbine blade 1 can by such a configuration and the interaction of the first mask element 32 with the second mask element 36 the second mask element 36 first by simply moving be removed from the resulting shaped body, without this by an undercut, for example, with the hook base 8 would be hindered. Then that can first mask element 32 by moving in through the Double arrow 46 indicated circumferential direction, ie essentially parallel to the orientation of the platform floor 12, away become. Thus, a reliable casting of the wax model the turbine blade 1 exclusively using sliders and without the use of "lost bets", so that in a particularly favorable manner the production also single-crystalline turbine blades 1 is possible. at Such production may be in the area of the blade axis 4 a nasal-type bordering the platform pocket Leave projection 50 of the platform 6. This lead 50 can in a particularly favorable manner as a support or fixative find use for an impingement cooling plate.

Claims (7)

Turbine blade (1) with a profiled, along a Blade axis (4) extended blade (2) to which in an end region extending transversely to the blade axis (4) Platform (6) is formed, the platform (6) one thickened compared to the platform floor (12) Has outer edge (14), of which the blade axis (4) facing Side wall (16) based on these slanted out is. Turbine blade (1) according to claim 1, on the blade of which (2) in the end area above the platform (6) a hook base (8) is formed. Turbine blade (1) according to claim 1 or 2, wherein the Outer edge (14) of the platform (6) in its bottom portion with a number of cooling holes (20) is provided. Turbine blade (1) according to claim 3, wherein the cooling holes (20) on the output side in a common cooling gap (22). Turbine blade (1) according to one of claims 1 to 4, which as a guide vane for a gas turbine, in particular for a Stationary gas turbine, is formed. Casting system (30) for producing a turbine blade (1) according to one of claims 1 to 5 with one in a casting mold positionable first mask element (32) having a Interface surface of the platform floor (12) predetermining recess (34), and in which a substantially flat trained second mask element (36) in one at an angle (β) more than 10 ° and less than 80 ° to the the interface predefining recess (34) tilted direction slidably guided. Casting system (30) according to claim 6, the second mask element (36) one opposite its base (42) by one Angle (γ) of more than 10 ° and tilted by less than 80 ° End face (44) which, together with the recess (34) of the first mask element (32) has a casting mask for the platform floor (12) forms.

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