EP2805023A1

EP2805023A1 - Turbine blade and associated method for producing a turbine blade

Info

Publication number: EP2805023A1
Application number: EP13713842.6A
Authority: EP
Inventors: Fathi Ahmad; Nihal Kurt; Hans-Thomas Bolms
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-03-29
Filing date: 2013-03-27
Publication date: 2014-11-26
Also published as: EP2644834A1; RU2014143493A; IN2014DN07295A; JP2015517048A; US20150064018A1; WO2013144245A1; CN104204417A

Abstract

The invention relates to a turbine blade (10), comprising a fastening section (14), a platform (16), and a blade (18), which follow one another along a longitudinal axis (12) of the turbine blade (10), wherein the platform (16) - in radial relation to the longitudinal axis (12) - comprises an inner platform part (22) and an outer platform part (24), wherein the outer platform part (24) is designed as a closed platform frame (28) that encloses the outer edge (26) of the inner platform part (22). The invention further relates to an associated method for producing a turbine blade.

Description

description

TURBINE BUCKET AND ASSOCIATED METHOD FOR PRODUCING A TURBINE BUCKET

The invention relates to a turbine blade having a buildin ^¬ actuating portion, a platform for defining a Strö ^¬ mung channel and a blade, which follow one another along a longitudinal axis of the turbine blade. The width ^¬ ren, the invention relates to a method for manufacturing a turbine blade comprising the step of: preparing a mo ^¬ nolithischen Rumpfschaufei comprising fastening portion an airfoil, a platform for defining a flow channel and a loading.

Turbine blades and methods of making turbine blades are known in a variety of ways from the extensive prior art. For example, turbine blades for gas turbines are often in one

Casting produced. During casting, the blade root, platform and blade are formed from the casting material at the same time, so that such turbine blades are in one piece. Subsequently, the surfaces exposed to the hot gas of the turbine - that is to say platform and blade - are provided with a corrosion protection layer and a thermal protection ^{layer in} order to increase the service life of the turbine blade. The cast turbine blades are usually also hollow, so that a means for cooling the blade material can flow inside. Turbine blades of steam engines are mostly milled from solid or forged.

The turbine blades used in stationary turbomachinery are subject to a variety of loads during operation of the turbomachinery which cause the turbine blades to age and wear down in both predictable and unpredictable ways. In detail, both low-cycle and higher cyclic fatigue loads as well as thermo-mechanical loading ^¬ loads occur. Also, turbine blades are to be protected from oxidation and creep. The aforementioned charge loading meet particular the hot gas or superheated steam immediacy ^¬ bar exposed surfaces and components of the turbine blades. On the mounting side, turbine blades are also exposed to so-called "bearing loads" and "friction loads". In the light of these varying loads and requirements, the material of integral turbine blades must be selected so that, if possible, a large number, if not all, loads are absorbed by the material without premature aging or premature end-of-life of the turbine blade being achieved. With regard to the thermal load and in terms of stress corrosion example, it is known to equip Turbi ^¬ nenschaufeln of gas turbines with a layer system, which protects the material from corrosion as well as both prior to an excessive heat input.

Nevertheless, in various areas of the turbine blade wear such as cracks can occur, which jeopardize the operation of the turbomachine. For this reason it is known to inspect turbine blades to a predetermined hardening time upon such defects to and replace the affected turbine acting ^¬ feln at Vorlie ^¬ gene of such a finding, or reprocessing.

It is also known to design turbine blades modular and to produce the corresponding modules from those materials that are tailored to their local requirements. Here, however, there is often a lack of a permanent and reliable connection. For example, US 4,650,399 AI discloses a

Blade with two platform halves, which are arranged on both sides of a blade. In order to prevent a shift of the platform halves entland the airfoil, a positive connection is provided, wherein the ^{¬ at} the platform halves are pinned together. The attachment of the platforms is classified as unsafe. An equally half division of platforms is disclosed by EP 1 905 950 AI and US 4,019,832 AI.

Instead of the platform operations of US Pat. No. 4,650,399 A1, WO 2000/057032 A1 discloses a single platform element between two directly adjacent blades of a rotor blade ring. Here, the assembly of the components on the rotor appears to be disadvantageous.

Other variants of built turbine blades show the US 3,451,654 AI and US 7,762,781 Bl. In both documents, it is proposed to use a one-piece platform for turbine blades, which has a profile of the blade ^¬ blade following recess. The platform loosely show ^¬ felblatt be passed through the platform and secured by means of intermediate pieces in each case for the production position of the turbine blades.

The object of the invention is to provide a turbine blade with a mounting portion, a platform for defining a flow channel and an airfoil, which follow one another along a longitudinal axis of the turbine blade aufein ^¬ , which turbine blade is wiederaufarbeitbar with very little effort. Another object of the invention is to provide a method of manufacturing turbine blades.

Directed onto the turbine blade object is achieved with egg ^¬ ner such according to the features of claim 1. On the method of manufacturing a turbine blade directed overall object is achieved with the method steps according to ^¬ demanding. 9 Advantageous embodiments are disclosed in the per ^¬ weiligen dependent claims. Here are the features the respective dependent claims with the features of other dependent claims readily combinable.

The invention is based on the finding that, in particular in the case of operationally required turbine blades, flaws caused by oxidation can also occur at the outer edge of the platform. These oxidation problems occur, in particular, when the thermal insulation layer, which is often provided there, locally flakes off. Such findings can lead to an increased operating risk in the turbine blade, which is why such turbine blades are replaced or processed. The reprocessing of the turbine blade has been comparatively expensive. At the same time, the work-up rate, i. the proportion of recycled blades that actually continue to qualify for use in the turbomachinery after reprocessing is likely to be low. To counteract these effects is proposed with the invention that the platform - in relation to a central longitudinal axis - an internal

Platform part and an outer platform part, wherein the outer platform part is formed as a the outer edge of the inner platform part encompassing endless platform frame. The platform frame is thus endlessly circulating and one-piece - it could also be called closed.

The invention does not attempt to provide a construction for mo- lar turbine blades, and therefore preferably the überströmbare from the hot gas surface of the inner platforms is substantially larger than the molding flowable from the hot gas via ^¬ surface of the platform frame.

If an operationally-loaded turbine blade is to be worked up in the region of the edge of the platform, the flaws specified above near the edge of the platform must be removed by setting back the edge of the platform, for example by milling or grinding. According to the invention it is provided that when resetting the platform edge not just the local flaw is removed. Rather, the platform edge along the entire circulation is reset so as to produce a monolithic Rumpfschaufei whose platform as the inner part of the platform to be manufactured turbo binenschaufel a contact surface for a platform frame ^¬ be riding up. After attaching an endless platform frame to the inner platform portion, the turbine bucket thus produced then has a platform whose dimensions correspond to the original turbine bucket.

Although not impaired or damaged blade material is removed in this process. However, this has the advantage that the reprocessing does not have to be carried out individually - that is, depending on the defective point - but can be carried out automatically. This reduces the effort for reprocessing and the reject rate.

Naturally it is possible by the method also new components that produce shovel thus not occupied by the turbine operation by a so-called. Rumpfschaufei an airfoil, a platform and a Fixed To ^¬ constriction portion is provided in a monolithic embodiment comprising first. The monolithic Rumpfschaufei can be made on conven ^¬ tionellem way by casting and beispiels- as well as monocrystalline or directionally solidified. After making the fuselage bucket, the platform edge of the fuselage bucket is possibly still to be brought along the entire circulation by slight grinding or milling to the predetermined, ex ^¬ tected measure to the inner platform portion of the turbine blade with a dimensionally bearing surface for the platform ^{¬ form} frame provide. Before, during or after the platform frame as mostly rectangular structure is herzustel ^¬ len. After attaching or mounting the platform frame to the dimensionally stable edge of the inner platform part, the turbine blade is then produced as a new component.

The platform frame may have different shapes in cross section. However, preferred are such forms, the make a positive connection with the edge of the inner platform part. For example, the cross-sectional shape may be diamond-shaped or C-shaped. The edge of the inner platform part is always designed corresponding to the cross-sectional shape.

A particular advantage of the turbine blade according to the invention and of the method that in particular two, can also be used under ^¬ schiedliche materials for the Rumpfschaufei and for the platform frame. Thus, in addition to the different local loads consideration be taken, which possibly leads to an extended life of the turbine blade.

A further advantage of the turbine blade according to the invention is the higher precision with regard to the external dimensions of the platform, since these can be produced more easily when producing the platform frame than when casting a purely monolithic turbine blade.

Different methods can be used for permanently connecting the platform frame to the fuselage bucket. Since the platform frame is designed as an endless frame, it is preferable to shrink the platform frame to the peripheral edge of the inner platform part. Prior to shrinking, the platform frame may be heated and / or the hull blast chilled. After assembly of platform frame and fuselage bucket and a subsequent temperature adjustment of the platform frame then sits firmly on the peripheral edge of the inner platform part. Soldering and welding - selectively as well as along the connecting line from the edge of the inner platform part and platform ^¬ frame - are possible. According to a first advantageous development of the

Platform frame surface on the inner platform part, wherein the contact surface at least partially with the longitudinal axis forms an angle which is greater than 0 ° and smaller than 90 °. Such an arrangement prevents at least in one direction a parallel displacement of the platform frame along the longitudinal axis, which is particularly advantageous when using the invention on turbine blades. In this case, the force acting on the platform frame during operation of the turbomachine centrifugal force is also transmitted by positive engagement due to the inclined with respect to the longitudinal axis contact surface ^¬ in the platform part. This ver ^¬ prevents reliably the loss of the platform frame due to the centrifugal force.

Preferably, the angle is a size between 15 ° and 35 °, for example, the angle is 20 °. According to a second advantageous embodiment of the

Platform frame on at least one laterally outwardly facing surface on a slot for receiving a sealing element. Such an embodiment has the advantage that when worn by existing in the platform edge slots due to the seated therein sheet-shaped sealing elements with the now provided invention is a simple and reliable way to work up such betriebsbean ^¬ blown turbine blades again. In addition, such slots can be produced more cost-effectively than with purely monolithic turbine blades.

Conveniently, the turbine blade can be designed both as Leit ^¬ blade or as a blade. In order that the turbine blade with the inner platform part and the outer platform part in the form of the endless platform frame enclosing the inner platform part can also be used in high-temperature applications, it is advantageous if the inner platform part and the platform frame are coated in a coating process. Thus, a seamless protective coating will be applied to both ^¬ platform parts. Further advantages and features of the invention are given in Figu ^¬ renbeschreibung. Show it:

FIG. 1 is a perspective view of the side view of a turbine blade according to the invention;

FIG. 2 is a perspective view of the plan view of a platform frame;

3 shows the cross section through a turbine blade according to

Figure 1 and

Figure 4 shows a section of the corner of a platform of

Turbine blade according to Figure 1 when assembling fuselage and platform frame.

In all figures, identical features are provided with the identical reference numerals.

1 shows a perspective view of a turbine blade 10. The turbine blade 10 is designed as a rotor blade. However, it could be designed as a guide vane forms ^¬. The turbine blade 10 comprises along its longitudinal axis 12 in immediate succession a Fixed To ^¬ constriction portion 14, a platform 16 and an airfoil 18. The attachment portion 14 is contoured in a typical run ^¬ shovel manner the manner of a fir tree profile. Guide vanes for turbines, instead of the fir-tree-shaped attachment portion 14 mostly a plurality of hooks, which are inserted into a not shown guide vane carrier of the turbomachine.

The attachment portion 14 merges into the platform 16. According to the representation selected in FIG. 1, the platform 16 has an upwardly pointing platform surface 20 on which the blade 18 settles. In the exemplary embodiment illustrated, the platform 16 comprises an inner platform part 22 - in radial relation to the longitudinal axis 12 and an outer platform part 24, wherein the outer platform ^¬ part 24 is formed as a the outer edge 26 of the inner platform part 22 encompassing endless platform frame 28. According to the illustrated embodiment, both attachment portion 14, the inner platform portion 22 and the blade 18 are monolithic - so one piece - ausgebil ^¬ det. This monolithic unit is also referred to as fuselage hoop 19. The facing in accordance with this diagram for airfoil 18 faces 20 of the inner platform member 22 and the outer platform portion 24 are offset-free to each other, so that - in use of the turbine blade 10 in ei ^¬ ner turbomachine - for the flowing in of the turbomachine working fluid an edge- and provide stepless boundary wall.

In this case, the surface of the inner platform part 22 that can be overflowed by the hot gas is substantially larger than the area of the platform frame 28 that can be overflowed by the hot gas. The turbine blade 10 can be designed to be internally cooled in any desired manner with the aid of a cooling medium. Also film ^¬ cool openings and trailing edge openings for the coolant can be provided. Of course, the turbine blade can also be uncooled.

Figure 2 shows a perspective view of the platform frame 28. The platform frame 28 includes two parallel longitudinal struts 30 and two mutually parallel Quer ^¬ struts 32. The platform frame 28 may be made of a different material than the material shown in Figure 1

However, the platform frame 28 may also be made of the same material. The platform frame may also be made by welding the longitudinal struts 30 to the cross struts 32. It can also be cast or milled from solid.

FIG. 3 shows a section through the turbine blade 10 along the longitudinal axis 12. In contrast to that in FIG. 1 shown turbine blade of the attachment portion of Figure 3 is not Tannenbaumförmig formed, but dovetailed. In addition, FIG. 3 shows the platform frame 28 during assembly on the fuselage boom 19, shortly before the platform frame 28 reaches its final assembly position. According to the illustrated embodiment, the platform frame 28 has a diamond shape in cross section. Other shapes are possible.

Each strut 30, 32 of the platform frame 28 has an inwardly facing first abutment surface 34 and a second on ^¬ bearing surface 36. Likewise, the outer edge 26 of the ^inner ren platform part 22 has a laterally outwardly facing first abutment surface 38 and a second abutment surface 40. After mounting the platform frame 28 are the first An ^¬ position surface 34 on the first bearing surface 38 of the inner

Platform part 22 and the second abutment surface 36 on the second abutment surface of the inner platform part 22 to surface. The thus forming first contact surfaces and second contact surfaces are inclined differently with respect to the longitudinal axis 12. The first contact surface is aligned in the transverse ^{¬ section} parallel to the longitudinal axis 12. However, the second contact surface is inclined in cross-section at an acute angle relative to the longitudinal axis 12. This exporting ^¬ approximate shape prevented by form-fit disengagement of the platform frame 28 from the Rumpfschaufei 19 at the door ^¬ binenschaufel 10 acting centrifugal forces.

Figure 4 shows a perspective view of a corner of the inner platform part 22 and the platform frame 28 during assembly. In addition to the features already described, a slot 44 for receiving a sheet-like sealing element is also shown in Figure 4 on a laterally outwardly facing surface 42 of the platform frame 28.

Overall, the invention thus relates to a turbine blade 10 having a mounting portion 14, a platform 16 and an airfoil 18, which along a longitudinal axis 12th the turbine blade immediately follow each other. In order to provide a particularly durable turbine blade 10, it is proposed that the platform 16 - in radial relation to the longitudinal axis 12 - an inner platform portion 22 and an outer platform portion 24 includes, wherein the outer platform ^¬ part 24 as a the outer edge 26 of the inner Platform part 22 encompassing endless platform frame 28 is formed. As for the method it is proposed to use a mo ^¬ nolithisch Rumpfschaufei produced 19 or adjust an already operational claimed turbine blade 10 along the entire revolution of the platform edge or to ^¬ reset and produce an endless platform frame 28 which can be mounted on the platform edge 26, then, so as to produce the original or planned dimensions of the turbine blade 10.

Claims

claims

1. turbine blade (10) having a mounting portion (14), a platform (16) for defining a flow channel and an airfoil (18) along a longitudinal axis (12) of the turbine blade (10) successive fol ^¬ gene

characterized in that

the platform (16) - in radial relation to the longitudinal axis (12) - an inner platform part (22) and an outer one

Platform part (24), wherein the outer platform part (24) as a the outer edge (26) of the inner platform part (22) embracing endless platform frame (28) is formed.

2. turbine blade (10) according to claim 1,

in that the platform frame (28) bears flat against the inner platform part (22) and the contact surface at least partially encloses an angle with the longitudinal axis (12) which is greater than 0 ° and less than 90 °.

3. turbine blade (10) according to claim 2,

in which the angle has a size between 10 ° and 35 ° ^¬ on.

4. turbine blade (10) according to claim 1, 2 or 3,

in the

the inner platform portion (22) and the attachment portion (14) and / or

the inner platform portion (22) and the airfoil (18) are monolithic.

5. turbine blade (10) according to one of the preceding claims,

in which the platform frame (28) has a slot (44) on at least one laterally outwardly facing surface (42). For receiving a sealing element.

Turbine blade (10) according to one of the preceding claims,

wherein the platform frame (28) on the inner platform 'part (22) is shrunk and / or soldered to and / or welded.

7. Turbine blade (10) according to one of the preceding claims,

formed from a vane or as a rotor blade.

8. turbine blade (10) according to one of the preceding claims,

in which the overflowable from the hot gas surface of the inner

Platform member (22) is substantially greater than the überströmbare from the hot gas ^¬ surface of the platform frame (28).

Method for producing a turbine blade (10) comprising the steps:

Producing a monolithic fuselage breech (19) comprises an airfoil (18), a platform (16) as an ^inner platform part (22) for delimiting a flow channel and a fastening section (14),

- Making an endless platform frame (28) and

- Mounting the endless platform frame (28) on the edge (26) of the platform (16).

10. The method according to claim 9,

in the manufacture of the fuselage shed (19)

the platform edge of a powered turbine blade is recessed along its entire circumference to produce an abutment surface (36, 38) for an endless platform frame (28) and for converting the platform (16) into the inner platform (22).

11. The method according to claim 9,

in which the fuselage breech (19) comprises a fastener A platform (16) and a blade ^¬ blade (18) is produced in a casting process and the platform edge (26) as a contact surface (36, 38) for an endless ^¬ loose platform frame (28) is configured.

12. The method according to claim 9, 10 or 11,

with the step that

the platform frame (28) is shrunk onto the inner platform part (22) and / or soldered and / or welded to the fuselage breech (19).

13. The method according to claim 9, 10, 11 or 12,

with the step of coating the inner platform part (22) and the platform frame (28) in a coating process.