KR20080018118A - Singlet welded nozzle hybrid design for a turbine - Google Patents

Abstract

Singlet welded nozzle hybrid design for a turbine is provided to set a singlet in grooves of axial and circumferential directions of an outer carrier directly or by welding the singlet to an outer ring. Singlet welded nozzle hybrid design for a turbine includes a turbine nozzle segment and an outer ring carrier. The turbine nozzle segment has at least one stator airfoil(30), an inner sidewall(132), and an outer sidewall structure. The inner sidewall is placed at a radially inner end part of the stator airfoil. The outer sidewall is placed at a radially outer end part of the stator airfoil. The outer ring carrier has a radially inner open groove. The outer sidewall is restricted from moving in an axial direction with respect to the open groove and is linked with the open groove in at least any one of circumferential and radial directions. The inner sidewall is mechanically coupled with the turbine nozzle segment by an inner ring(152).

Description

SINGLET WELDED NOZZLE HYBRID DESIGN FOR A TURBINE}

The steam turbine design consists of stationary nozzle segments that direct steam flow into a rotating bucket connected to the rotor. In steam turbines, the nozzle configuration is commonly referred to as a diaphragm stage.

Conventional diaphragm stages are constructed using one of two methods. The first method is a "band / ring" method that uses an assembly consisting of a plurality of airfoils contained within the inner and outer bands and then the banded airfoil assembly is welded into the inner (web) and outer rings. The second method involves welding the airfoil directly to the inner and outer rings using a fillet welded at the interface. The second method is typically used for larger airfoils that are accessible for forming welds. However, there are also restrictions on the use of band configurations on smaller stages. One disadvantage is the inherent weld distortion of both the flow path and the vapor path sidewalls. In this regard, the welding used for assembly is of fairly large size and of considerable heat input. These materials and heat inputs distort the flow path, and airfoils often need to be adjusted after welding and stress relief. As a result of the distortion the stage efficiency is reduced.

In turbines, thermally induced stresses always lead to cracking in turbine nozzles. Due to the harsh environment, the art in the above-described field exhibits cracking along the engine axial direction of the nozzle airfoil. If the crack propagates along the entire length of the airfoil and the airfoil fails catastrophically, large debris from the nozzle is pulled out and moved downstream into the turbine's rotating hardware. Subsequent damage to the hardware of the turbine (rotating and stationary) can be severe and expensive.

In dual or triple nozzle designs (two or three airfoils per nozzle segment, respectively), the increased number of airfoils provides some contrast against catastrophic failure through the redundancy of multiple load paths. To provide. However, in monolithic designs (one airfoil per nozzle segment), if not retained on both platforms, a large section of the nozzle (airfoil and / or platform) may be lost into the flow path if the airfoil is completely split into two. have.

The present invention provides, among other things, a monolithic weld nozzle hybrid design that addresses the above-mentioned warpage problems. More specifically, in an exemplary embodiment of the present invention, a monolith (a single airfoil with side walls) is seated directly in the axial and circumferential grooves of the outer carrier or welded to the outer ring to the outer carrier. A configuration is provided that rests within the groove of the. The inner connection is performed with a unique inner sidewall configuration. In one exemplary embodiment, the inner sidewalls are welded to fit in a circumferentially extending ring or to each other via small radial welding between the inner sidewall endfaces (slashfaces). Are welded.

Accordingly, the present invention provides a turbine nozzle segment having at least one stator airfoil, an inner sidewall at the radially inner end of the stator airfoil, and an outer sidewall structure at the radially outer end of the stator airfoil, and formed therein. A complementary ring component having a radially inner surface of the inner sidewall with a circumferential groove and a key portion for receiving within the circumferential groove, the ring component being circumferential in the axial direction of the turbine And at least partially extending to engage an inner sidewall of at least two respective adjacent nozzle inner sidewalls, wherein the ring component may be implemented as a turbine mechanically fixed to the nozzle inner sidewall.

The invention also relates to a turbine nozzle segment having at least one stator airfoil, said turbine nozzle segment comprising an inner sidewall at a radially inner end of said stator airfoil and an outer sidewall structure at a radially outer end of said stator airfoil; An outer ring carrier having an inner open groove, the outer side wall configured to slidably engage the groove in a radial direction, with limited axial movement relative to the groove, the inner side wall being circumferential It can be implemented as a turbine mechanically coupled to a turbine nozzle segment adjacent in the direction.

The invention also includes a turbine nozzle segment having at least one stator airfoil and including an inner sidewall at a radially inner end of the stator airfoil and an outer sidewall structure at a radially outer end of the stator airfoil, Each adjacent nozzle inner sidewall end face may be implemented as a turbine welded or brazed to each other.

According to the present invention, a monolithic weld nozzle hybrid design is provided that addresses the warping problem, wherein the monolith is seated directly in the axial and circumferential grooves of the outer carrier or welded to the outer ring and seated in the groove of the outer carrier.

1 shows a conventional configuration of an impulse type turbine stage using partition walls, bands and rings welded into an assembly. More specifically, this conventional configuration includes a plurality of included in inner and outer bands 14, 16 welded into inner ring (web) 26 and outer ring 28 at reference numerals 18, 20, 22, 24. A diaphragm assembly 10 composed of an airfoil 12 is used.

As can be seen above, the current method of incorporating a single nozzle configuration into a ring has no critical weld depth, no assembly alignment features, and no retention features in case of weld breakage. In addition, one major problem with the current method of diaphragm construction is that the current method can cause significant flow path distortion. Indeed, traditional monolithic nozzle assemblies use a high heat input weld method that causes undesirable flow path distortion.

The present invention improves the vapor flow path of the stator nozzle (diaphragm) component. This is for example in inner sidewall connections such as welded endwalls, low heat seal welds with mechanical locks or miniature ring keys welded to the inner sidewalls as described below. This is done by a simplified and critical low heat input monolithic welding assembly using the novel approach of. The present invention also improves production costs and cycles by adding features that aid the assembly process and aid the machining fixation process. Moreover, the present invention adds features that reduce the risk of unintended turbine shutdown due to hardware weld breakage.

The monolithic weld nozzle hybrid design provided in accordance with an exemplary embodiment of the present invention forms a unitary, ie configuration comprising a single airfoil having respective inner and outer sidewall components. The outer sidewall component is mechanically fitted and then welded to the outer ring carrier.

The connection of the inner sidewalls can be accomplished in several ways. As described in the various embodiments below, the inner sidewall of the monolith of the diaphragm may be mechanically fitted and welded to the seal carrier or the miniature ring, and the small radial weld may be a circumferentially adjacent sidewall end face ( endface) (slashface). This configuration is mainly suitable for nozzle configurations considered as a turbine or “drum” configuration turbine section of the reaction type, characterized by smaller stage axial spacing and typically increased stage number.

2 illustrates an exemplary embodiment of the invention in which a monolithic nozzle slides into a carrier. The monolith consists of an airfoil 30 and inner and outer sidewalls 32 and 34. In the embodiment of FIG. 2, the outer ring carrier 40 is configured to slidably engage the outer sidewall 34 and mechanically lock in the radial and axial directions. For that purpose, in the illustrated embodiment, the outer sidewall 34 is formed to extend radially to be received in a circumferentially extending groove 42 of the outer ring carrier 40. In the exemplary embodiment shown, the axial end faces of the outer sidewall 34 extend first and circumferentially to receive corresponding axial projections 48, 50 in the ring carrier groove 42. Two grooves 44 and 46 are defined. There is no welding between the monolith 34 outer platform and the carrier 40. These nozzles slide into the carrier in the circumferential direction and are welded to the inner ring only on the inner sidewalls, as described in more detail below. These nozzles may be monolithic, duplex, or any other coefficient that slides into groove 42. If these nozzles are at least doubled, the monolith is welded to a partial outer ring having a carrier interface groove therein (to form a subassembly of the doublet abnormality coefficient).

According to an exemplary embodiment, the radially inner sidewalls 32 of the circumferentially adjacent monoliths are joined to each other. According to some exemplary embodiments, the inner ring 52 is keyed and welded 54, 56 to the component. The keyed inner ring defines the seal carrier. According to an exemplary embodiment of another variant, the unitary inner sidewalls 32 are welded to each other at opposite end faces. Examples of the above-described assemblies are described in more detail below with reference to FIGS. 3-6 and 9. These exemplary embodiments will be described using several identical reference numbers (used with reference to FIG. 2), with some corresponding reference numbers incremented by adding 100 as appropriate.

3 shows an exemplary inner ring 152 arranged to extend at least a portion of the rotor in the circumferential direction to join the circumferentially adjacent monoliths. To define an alignment / failsafe interface with the inner sidewall 132, the inner ring 152 includes a keyed protrusion 158 that engages with a corresponding cutout 160 of the inner sidewall 132. do. More specifically, the monolith is held axially by an inner ring interfacing with the keyed cutout 160 of the inner sidewall. As shown, a low heat ring weld (seal weld) 154, 156 is provided between the (respective) nozzle inner sidewall and the seal carrier. Since the mechanical engagement at the radially outer end (FIG. 2) keeps the nozzle end from moving downstream, this welding is not necessarily meant to be a significant structural weld. In this regard, the mechanical design as shown allows welding, which is a very low heat input causing minimal warpage of the airfoil and vapor path surfaces.

In this exemplary embodiment, the inner ring 152 is also configured to include a seal carrier. The seal carrier is designed to be very small so that it can fit in small axial and radial spacings typical of turbine types in drum configurations. This is in contrast to the substantial structure needed to maintain a typical packing segment at the rotor interface. Thus, the proposed carrier will promote more advanced seals, ie brush seals, shingle seals or polishable seals. The carrier can also be coated with a sprayable spray prior to assembly and machined for ring removal when small seal welds require repair (recoating). In the exemplary embodiment of FIG. 3, the inner seal carrier ring 152 holds the brushed seal structure 162.

4 shows a variant inner seal carrier ring 252 with a laminated seal 262. Again, a keyed interface 258/260 is provided between the seal carrier ring 252 and the inner sidewall 232. Low heat ring welding (seal welding) 254 and 256 are also provided upstream and downstream, as shown, to secure the inner seal carrier ring 252 to the inner sidewall 232 of each row of monolithic nozzles.

FIG. 5 shows the inner carrier ring 352 held axially as in the embodiment of FIGS. 3 and 4 by the interface of the inner seal carrier ring 352 with the keyed cutout 360 of the inner sidewall 332. Another embodiment of) is shown. As shown, in this embodiment, rather than providing ring welds 54, 56 as described with reference to the embodiments of FIGS. 2, 3, and 4, the seal carrier ring 352 is a monolithic nozzle. Radial bolts 364 into the inner sidewall 332 and airfoil 330 to hold the carrier ring 352 in place. In this embodiment, the seal carrier ring 352 incorporates a brushed seal 362, although the radial engagement shown may be incorporated into other inner ring structures without departing from the present invention.

6 illustrates another variant embodiment of the present invention in which a key ring 452 is provided but the seal carrier side is omitted entirely. Thus, in this embodiment, the nozzle inner sidewalls each have a defined key notch or groove 460 penetrating in the circumferential direction, and the key ring 452 is seated in the circumferential groove 460 to provide a low heat ring in place. Welded (seal weld) 454, 456. The welded key ring thus integrates the nozzle unit into the welded and mechanical engagement.

As described above with reference to FIG. 3, in the first exemplary embodiment, the nozzle, or more specifically the nozzle outer sidewall, slides into the carrier, respectively, and radially and axially locks at the outer end of the nozzle. To provide. FIG. 7 shows another variant embodiment in which the monolithic nozzle outer sidewall 534 is welded to the solid outer ring 538 using front and rear small axial welds 566 and 568. The assembly of monolith and outer ring is then seated in a corresponding groove 542 of the nozzle carrier 540. The nozzle assembly (outer ring 538 and nozzle (s) welded thereto) is not welded to the carrier, and the nozzle assembly can move radially within the carrier groove 542. Thus, in this embodiment, the carrier 540 does not have a circumferential groove that is typical in reaction turbine designs using slide-in nozzles.

Mechanical features of the interface of the monolith and outer ring 538 are used as assembly and alignment features, allowing for improved reliability and reduced risk. In this regard, the mechanical lock between the ring and the nozzle (s) cannot go downstream because the ring and nozzle have a mechanical interface that prevents the assembly from failing due to pressure in the event of a failure of the airfoil. In addition, the mechanical lock serves as the purpose of a predetermined and repeatable weld stop. In this regard, the welding beam (assuming EB welding) will stop when it hits the radial engagement interface. Another advantage of the embodiment of FIG. 7 is that the radially outer face of the nozzle outer sidewall is configured as a flat end instead of the more expensive circumferential notch end as in the embodiment of FIG. 2.

The exemplary embodiment of FIG. 7 is mechanically locked and brazed or welded to the nozzle inner sidewall 532 as in the embodiments of FIGS. 2-4 and 6, or as in the embodiment of FIG. 5. Only mechanically locked to the nozzle.

8 and 9 show another exemplary embodiment of the present invention. More specifically, FIG. 8 shows a side view of a monolithic nozzle welded to the outer ring 538 at the radially outer sidewall 534 as in the embodiment of FIG. 7. However, on the radially inner ends, rather than providing the ring seal 552 as in the embodiment of FIG. 7, the inner side 632 end faces 670 are welded to each other. Thus, Figure 9 shows an axial view of the inner sidewall end wall / slash surface, each welded together. It will be appreciated that this welding may be a low heat input welding similar to butt welding performed with laser welding or electron beam welding (EBW). Such an interface can also be considered for a braze joint if considered to be more economical. The purpose of this radial welding is to form a continuous bond of the inner sidewalls. This welding does not necessarily need to be a structural weld, but will cause a zero gap between the nozzle segment inner sidewalls (end faces).

A typical monolithic nozzle outer wall interface as described above is a circumferential cutout end, but it should be understood that the variant monolithic nozzle outer sidewall interface can be machined as a flat end that is less expensive than the circumferential cutout end.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments and conversely encompasses various modifications and equivalent arrangements falling within the spirit and scope of the appended claims. It should be understood that it is intended.

1 is a schematic front view of a conventional stage with nozzle diaphragms formed using a band / ring method,

2 is a schematic front view of a unitary configuration in accordance with an exemplary embodiment of the present invention;

3 is a schematic front view of a radially inner end of a monolithic configuration with a brush shaped seal in accordance with an exemplary embodiment of the present invention;

4 is a schematic front view of a radially inner end of a monolithic configuration with a seal in a stacked form according to another exemplary embodiment of the present invention;

5 is a schematic front view of a radially inner end of a monolithic configuration with a brush shaped seal according to another exemplary embodiment of the present invention;

6 is a schematic front view of a radially inner end of a unitary construction according to another exemplary embodiment of the present invention;

7 is a schematic front view of a unitary configuration according to another exemplary embodiment of the present invention;

8 is a schematic front view of a unitary configuration according to another exemplary embodiment of the present invention;

9 is an axial view of an adjacent monolithic nozzle welded to the inner sidewall endface according to another exemplary embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

30: stator air foil 40, 540: outer ring carrier

34,534: outer sidewall structure 42,542: groove

32, 132, 232, 332, 432, 532, 632: inner sidewall

Claims (10)

In the turbine, An inner sidewall (32, 132, 232, 332, 432, 532, 632) and a radially outer end of the stator airfoil, having at least one stator airfoil (30); A turbine nozzle segment comprising outer sidewall structures 34, 534 at An outer ring carrier 40, 540 with radially inward open grooves 42, 542, The outer sidewalls 34, 534 are configured to engage the grooves 42, 542 in at least one of circumferential or radial directions, with limited axial movement relative to the grooves 42, 542. , The inner sidewalls 32, 132, 232, 332, 432, 532, 632 are mechanically coupled 52, 152, 252, 352, 452, 552, 670 to circumferentially adjacent turbine nozzle segments. turbine. The method of claim 1, The radially inner surface of the inner sidewalls 32, 132, 232 has circumferential grooves 160, 260, 360, 460 formed therein, At least a portion 158, 258 of complementary ring components 52, 152, 252, 352, 452, 552 are received in the circumferential groove, the ring component being at least partially in the circumferential direction of the turbine's axis. Extends into an inner sidewall of at least two respective adjacent nozzle inner sidewalls, The ring component is mechanically fixed (54, 56; 154, 156; 254, 256; 364; 454, 456) to the nozzle inner sidewall. turbine. The method of claim 2, The ring component is welded to the nozzle inner sidewalls 54, 56; 154, 156; 254, 256; 454, 456. turbine. The method of claim 2, The ring component includes a seal carrier 52, 152, 252, 352, 552. turbine. The method of claim 4, wherein The seal carrier is a seal carrier (152, 352) in the form of a brush turbine. The method of claim 4, wherein The seal carrier is a stack carrier seal 252. turbine. The method of claim 4, wherein The seals 52, 152, 252 are welded to the nozzle inner sidewalls 54, 56; 154, 156; 254, 256. turbine. The method of claim 2, A radial bolt 364 is arranged to extend through the ring component 352 and into the nozzle inner sidewall 332. turbine. The method of claim 1, The outer sidewall 534 is welded to the outer ring 538 received in the groove with the outer sidewall. turbine. The method of claim 1, Each adjacent nozzle inner sidewall 632 end face of the circumferentially adjacent turbine nozzle segment is welded or brazed 670 to each other. turbine.

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