US20140255194A1

US20140255194A1 - Tip shrouds of turbine rotor blades and methods of manufacture related thereto

Info

Publication number: US20140255194A1
Application number: US13/725,649
Authority: US
Inventors: Mark Andrew Jones
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2012-12-21
Filing date: 2012-12-21
Publication date: 2014-09-11
Also published as: WO2014137441A1; DE112013006128T5

Abstract

A rotor blade for use in a turbine of a turbine engine is described. The rotor blade may include an airfoil that extends from a connection with a root. The airfoil may include a pressure sidewall and a suction sidewall that define an outer periphery and an outboard tip. The rotor blade may further include a tip shroud assembly disposed at the outboard tip of the airfoil. The tip shroud assembly includes a non-integral tip shroud.

Description

BACKGROUND OF THE INVENTION

The present application relates generally to apparatus and assemblies concerning the design and operation of rotor blades in turbine engines. More specifically, but not by way of limitation, the present application relates to apparatus and assemblies pertaining to tip shrouds of turbine rotor blades.
While the examples provided herein are primarily aimed at combustion turbine engines, those of ordinary skill in the art will appreciate that the present invention is applicable to the rotor blades used in combustion or steam turbine engines. In a combustion turbine engine, which may include power generating, aircraft or other engine types, pressurized air is used to combust a fuel so to generate a flow of hot combustion gases, which is then directed through one or more turbines that extract energy. In accordance with such a turbine, generally, rows of circumferentially spaced turbine rotor blades extend radially outwardly from a supporting rotor disc. Each blade typically includes a dovetail that permits assembly and disassembly of the blade in a corresponding dovetail slot in the rotor disc, as well as an airfoil that extends radially outwardly from the dovetail and interacts with the flow of the working fluid through the engine. The airfoil has a pressure side and suction side extending axially between corresponding leading and trailing edges and radially between a root and a tip. It will be understood that the blade tip is spaced closely to a radially outer turbine shroud for minimizing leakage therebetween of the combustion gases flowing downstream between the turbine blades.
Tip shrouds often are implemented on aft stages or rotor blades to provide damping and reduce the over-tip leakage of the working fluid. The design of a tip shroud is challenging because the material is exposed to high temperatures and strong forces for thousands of hours of operation, which leads to fatigue and creep, and design criteria offer few areas for compromise given current material limitations. Aerodynamically, large tip shrouds are desirable because they seal the gas path more effectively, yet larger tip shrouds are difficult because they increase the pull load on the rotor blade, which exacerbates stress and creep issues.
Conventional design of tip shrouds offer several ways to alleviate operational stresses in this region, but these have met with only limited success. Scalloping, or reducing the size of the tip shroud, is one way in which the size of the tip shroud may be reduced so that mechanical stresses are reduced, but generally the necessary trade-off between size and aerodynamic function is an undesirable one. Additionally, as modern turbine engine designs increase the temperatures and the annulus area through the hot gas path so that greater efficiency is achieved, the size of the tip shrouds must further decrease so that creep and fatigue issues associated with the tip shroud do not limit the life of the rotor blade, which is typically tens of thousands of hours long. Cooling tip shrouds with a coolant circulated through the interior of the rotor blade will enable a longer part life for larger tip shrouds, but the manufacturing of the necessary interior passageways introduce additional cost to the manufacturing process. Other solutions, such as coring the tip shroud, adding additional seal rails to it, increasing the fillet sizes attaching it to the rotor blade, and reducing the radial distance of the tip shroud from the axis, have helped mitigate or solve only some issues related to this region of the rotor blade. There remains, however, a need for solutions that offer improved aerodynamic performance while also extending the life of the rotor blade.

BRIEF DESCRIPTION OF THE INVENTION

The present application thus describes a rotor blade for use in a turbine of a turbine engine. The rotor blade may include an airfoil that extends from a connection with a root. The airfoil may include a pressure sidewall and a suction sidewall that define an outer periphery and an outboard tip. The rotor blade may further include a tip shroud assembly disposed at the outboard tip of the airfoil. The tip shroud assembly includes a non-integral tip shroud.
The present application further describes a method of manufacturing a rotor blade for use in a turbine of a combustion turbine engine, the rotor blade comprising an airfoil that extends from a connection with a root, the airfoil including a pressure sidewall and a suction sidewall that define an outer periphery and an outboard tip, the method may include the steps of: manufacturing the rotor blade with connecting means at the outboard tip of the airfoil; manufacturing the tip shroud to have corresponding connecting means at an inboard surface of the tip shroud; and connecting the tip shroud to the airfoil via the connecting means of the airfoil and the corresponding connecting means of the tip shroud. The connecting means of the airfoil and the connecting means of the tip shroud together may have a mechanical interference joint.
These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more completely understood and appreciated by careful study of the following more detailed description of exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic representation of an exemplary combustion turbine engine in which embodiments of the present application may be used;

FIG. 2 is a sectional view of the compressor in the combustion turbine engine of FIG. 1;

FIG. 3 is a sectional view of the turbine in the combustion turbine engine of FIG. 1;

FIG. 4 is a perspective view of an exemplary combustion turbine engine rotor blade having a tip shroud of conventional design;

FIG. 5 is a top or outboard view of a series of installed turbine blades having tip shrouds of conventional design;

FIG. 6 is a side view of a non-integral tip or detachable tip shroud and rotor blade assembly according to embodiments of the present application;

FIG. 7 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 8 is an aft view of the detachable tip shroud and rotor blade assembly of FIG. 7 in a detached condition according to embodiments of the present application;

FIG. 9 is a top or outboard view of the airfoil of FIG. 7 according embodiments of the present application;

FIG. 10 is a side view of the detachable tip shroud and rotor blade assembly of FIG. 7 in a condition during assembly according to embodiments of the present application;

FIG. 11 is a side view of the detachable tip shroud and rotor blade assembly of FIG. 7 in an assembled condition according to embodiments of the present application;

FIG. 12 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 13 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 14 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 15 is a top or outboard view of the rotor blade and a superimposed tip shroud illustrating the direction of sliding engagement of interlocking components compared to the direction of rotation of the rotor blade according to embodiments of the present application;

FIG. 16 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 17 is a front view of the detachable tip shroud and rotor blade assembly of FIG. 16 in a detached condition according to embodiments of the present application;

FIG. 18 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 19 is a front view of the detachable tip shroud and rotor blade assembly of FIG. 18 in a detached condition according to embodiments of the present application;

FIG. 20 is a side view of a detachable tip shroud and rotor blade assembly in a disassembled condition according to embodiments of the present application;

FIG. 21 is a side view of a detachable tip shroud and rotor blade assembly in an assembled condition according to embodiments of the present application; and

FIG. 22 is a front view of the detachable tip shroud and rotor blade assembly of FIG. 21 in a detached condition according to embodiments of the present application.

DETAILED DESCRIPTION OF THE INVENTION

As an initial matter, in order to clearly delineate the invention of the current application, it may be necessary to select terminology that refers to and describes certain parts or machine components within a combustion turbine engine. As mentioned, while the examples provided herein are primarily aimed at combustion turbine engines, those of ordinary skill in the art will appreciate that the present invention is applicable to the rotor blades used in combustion or steam turbine engines. Whenever possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. However, it is meant that any such terminology be given a broad meaning and not narrowly construed such that the meaning intended herein and the scope of the appended claims is unreasonably restricted. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different terms. In addition, what may be described herein as being single part may include and be referenced in another context as consisting of multiple components, or, what may be described herein as including multiple components may be referred to elsewhere as a single part. As such, in understanding the scope of the present invention, attention should not only be paid to the terminology and description provided herein, but also to the structure, configuration, function, and/or usage of the component, particularly as provided in the appended claims.
In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. Accordingly, these terms and their definitions, unless stated otherwise, are as follows. As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of a fluid, such as the working fluid through the turbine engine or, for example, the flow of air through the combustor or coolant through one of the turbine's component systems. As such, the term “downstream” corresponds to the direction of flow of the fluid, and the term “upstream” refers to the direction opposite to the flow. The terms “forward” and “aft”, without any further specificity, refer to directions, with “forward” referring to the forward or compressor end of the engine, and “aft” referring to the aft or turbine end of the engine. The term “radial” refers to movement or position perpendicular to an axis. It is often required to describe parts that are at differing radial positions with regard to a center axis. In cases such as this, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is “radially inward” or “inboard” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. It will be appreciated that such terms may be applied in relation to the center axis of the turbine.
By way of background, referring now to the figures, FIGS. 1 through 3 illustrate an exemplary combustion turbine engine in which embodiments of the present application may be used. It will be understood by those skilled in the art that the present invention is not limited to this type of usage. As stated, the present invention may be used in combustion turbine engines, such as the engines used in power generation and airplanes, steam turbine engines, and other types of rotary engines. The examples provided are not meant to be limiting to the type of the turbine engine.
FIG. 1 is a schematic representation of a combustion turbine engine 10. In general, combustion turbine engines operate by extracting energy from a pressurized flow of hot gas produced by the combustion of a fuel in a stream of compressed air. As illustrated in FIG. 1, combustion turbine engine 10 may be configured with an axial compressor 11 that is mechanically coupled by a common shaft or rotor to a downstream turbine section or turbine 13, and a combustor 12 positioned between the compressor 11 and the turbine 13.
FIG. 2 illustrates a view of an exemplary multi-staged axial compressor 11 that may be used in the combustion turbine engine of FIG. 1. As shown, the compressor 11 may include a plurality of stages. Each stage may include a row of compressor rotor blades 14 followed by a row of compressor stator blades 15. Thus, a first stage may include a row of compressor rotor blades 14, which rotate about a central shaft, followed by a row of compressor stator blades 15, which remain stationary during operation.
FIG. 3 illustrates a partial view of an exemplary turbine section or turbine 13 that may be used in the combustion turbine engine of FIG. 1. The turbine 13 may include a plurality of stages. Three exemplary stages are illustrated, but more or less stages may be present in the turbine 13. A first stage includes a plurality of turbine buckets or turbine rotor blades 16, which rotate about the shaft during operation, and a plurality of nozzles or turbine stator blades 17, which remain stationary during operation. The turbine stator blades 17 generally are circumferentially spaced one from the other and fixed about the axis of rotation. The turbine rotor blades 16 may be mounted on a turbine wheel (not shown) for rotation about the shaft (not shown). A second stage of the turbine 13 also is illustrated. The second stage similarly includes a plurality of circumferentially spaced turbine stator blades 17 followed by a plurality of circumferentially spaced turbine rotor blades 16, which are also mounted on a turbine wheel for rotation. A third stage also is illustrated, and similarly includes a plurality of turbine stator blades 17 and rotor blades 16. It will be appreciated that the turbine stator blades 17 and turbine rotor blades 16 lie in the hot gas path of the turbine 13. The direction of flow of the hot gases through the hot gas path is indicated by the arrow. As one of ordinary skill in the art will appreciate, the turbine 13 may have more, or in some cases less, stages than those that are illustrated in FIG. 3. Each additional stage may include a row of turbine stator blades 17 followed by a row of turbine rotor blades 16.
In one example of operation, the rotation of compressor rotor blades 14 within the axial compressor 11 may compress a flow of air. In the combustor 12, energy may be released when the compressed air is mixed with a fuel and ignited. The resulting flow of hot gases from the combustor 12, which may be referred to as the working fluid, is then directed over the turbine rotor blades 16, the flow of working fluid inducing the rotation of the turbine rotor blades 16 about the shaft. Thereby, the energy of the flow of working fluid is transformed into the mechanical energy of the rotating blades and, because of the connection between the rotor blades and the shaft, the rotating shaft. The mechanical energy of the shaft may then be used to drive the rotation of the compressor rotor blades 14, such that the necessary supply of compressed air is produced, and also, for example, a generator to produce electricity.
FIG. 4 is a perspective view of an exemplary combustion turbine engine rotor blade having a tip shroud of conventional design. The turbine rotor blade 16 generally includes a root 21, which may include means by which the rotor blade 16 attaches to a rotor disc, such as a dovetail configured for mounting in a corresponding dovetail slot in the perimeter of the rotor disc. The root 21 may further include a shank that extends between the dovetail and a platform 24, which is disposed at the junction of the airfoil 25 and the root 21 and defines a portion of the inboard boundary of the flowpath through the turbine engine 10. The airfoil 25 is the active component of the rotor blade 16 that intercepts the flow of the working fluid and that induces the rotor disc to rotate.
As illustrated, at the outboard tip of the rotor blade 16, a tip shroud 37 may be positioned. The tip shroud 37 essentially is an axially and circumferentially extending flat plate or disc that is supported towards its center by the airfoil 25. Positioned along the top of the tip shroud 37 may be one or more seal rails 38. Generally, the seal rails 38 projects radially outward from the outboard surface of the tip shroud 37. The seal rails 38 generally extend circumferentially between opposite ends of the tip shroud 37 in the general direction of rotation. The seal rail 38 is formed to deter the flow of working fluid through the gap between the tip shroud 37 and the inner surface of the surrounding stationary components and helps prevent creep of the tip shroud. In some conventional designs, the seal rails 38 extend into an abradable stationary honeycomb shroud that opposes the rotating tip shroud 37. In some cases, a cutter tooth may be disposed on the seal rail 38 so as to cut a groove in the honeycomb of the stationary shroud that may positioned outboard of the tip shroud 37.
The tip shrouds 37 may be formed such that the tip shrouds 37 of neighboring rotor blades 16 make contact during operation. FIG. 5 is a top or outboard view of a series of turbine rotor blades 16 having tip shrouds 37 according to a conventional design. Specifically, FIG. 5 illustrates neighboring tip shrouds 37 as they might appear when assembled on a turbine rotor disc, and provides an example of a conventional arrangement where neighboring tip shrouds 37 make contact with each other during operation. Two full neighboring tip shrouds 37 are shown with an arrow indicating the direction of rotation. As depicted, the trailing edge of the leading tip shroud 37 may contact or be in close proximity to the leading edge of the trailing tip shroud 37.
Turning now to FIGS. 6 through 23, illustrations are provided in accordance with certain aspects of the present invention. In certain embodiments, the detachable tip shroud 51 is defined as a tip shroud 51 that is not integrally formed with the rotor blade 16. In other embodiments, the detachable tip shroud 51 is a tip shroud that has been joined to the rotor blade 16 by an attachment means that include welding, brazing, and other similar types of connecting processes. In certain preferred embodiments, the detachable tip shroud 51 of the present invention is one that attaches to the rotor blade 16 by a mechanical interference joint, such as a dovetail joint, hook, bolt, rivet, pinning configuration, or other mechanical interference joint, as discussed in detail below. In general, it will be appreciated that, because the detachable tip shroud 51 is not formed integrally to the rotor blade 16, the detachable aspect inherent in any of these various types of connections allow a tip shroud to be removed, replaced, or reused with greater efficiency than would otherwise be possible.
More specifically, as illustrated in FIG. 6, a side view of a non-integral and detachable tip shroud 51 according to embodiments of the present invention is provided. As illustrated, there may be an interface or joint 54 between the detachable tip shroud 51 and the airfoil 25. That is, according to embodiments of the present invention, the detachable tip shroud 51 may be formed separately from the turbine rotor blade 16, and then attached thereto along the joint 54. In certain embodiments, the joint 54 may be a welded connection that is formed between the detachable tip shroud 51 and the airfoil 25. In making this connection, it will be appreciated that any conventional welding process may be employed. The joint 54 may further include a brazed connection according to any conventional brazing process. While a welded or brazed joint may not be as convenient at joining or removing a detachable tip shroud 51 from a rotor blade 16 as some of the more mechanical joining arrangements discussed below, it will be appreciated that the welded or brazed interface or joint 54 would provide a seam along which the tip shroud 51 and airfoil 25 may be disassembled in a manner more efficient than if the two pieces were integrally formed. This readily available manner by which the tip shroud 51 may be removed from the rotor blade 16 may allow the removal, reuse, or replacement of the tip shroud 51 and/or the rotor blade 16. The joint 54, as illustrated, may be disposed at or near the outboard tip 45 of the airfoil 25. It will be appreciated that the present invention is not limited to any specific tip shroud 51 design. That is, unless specifically stated otherwise, the detachable aspects of present invention may be used with larger tip shrouds, scalloped tip shrouds, tip shrouds having one or more seal rails, tip shrouds having a variety of interfaces with neighboring tip shrouds, tip shrouds that do not connect with each rotor blade, tip shrouds with cores or cooling holes, etc.
A feature that is common to many turbine rotor blades 16 is the circulation of coolant through interior cooling passages during operation, particularly within the platform and airfoil regions of the rotor blade. This type of cooling allows turbine rotor blades 16 to withstand the higher temperatures that are common in many of today's combustion turbine engines. Accordingly, the rotor blade 16 may include one or more interior cooling channels 47 that extend from a connection made with a coolant source, which is generally formed through the root 21 of the rotor blade 16, toward the tip shroud 51. A simplified configuration for such a cooling passage is provided in FIG. 6. It will be appreciated that the interior cooling channel 47 may have a variety of configurations and that virtually any configuration may be incorporated into the airfoils 25 and the tip shrouds 51 of the present invention. As illustrated, the interior cooling channel 47 of the airfoil 25 may extend to an outlet formed on the outboard tip of the airfoil and, from there, feed into an interior cooling channel 48 of the tip shroud 51. Specifically, the detachable tip shroud 51 may include an interior cooling passage 48 that extends from an inlet formed on an inboard surface 53 of the tip shroud 51. Additional interior cooling channels 47 and interior cooling passages 48 may be included. It will be appreciated that the outlet formed at the outboard tip 45 of the airfoil 25 and the inlet formed at the inboard surface 53 of the detachable tip shroud 51 may be configured to align once the detachable tip shroud 51 is fitted to the airfoil 25. The interior cooling passage 48 may include one or more outlets formed along the exterior of the tip shroud 51. In this manner, the cooling passages 48 may provide cooling to the interior portions of the tip shroud 51, while also providing cooling ports that allow for cooling outer surfaces of the tip shroud 51.
FIGS. 7 through 11 provide several views of a detachable tip shroud 51 according to a preferred embodiment of the present invention. FIG. 7 shows a side view and FIG. 8 shows a front view of a detachable tip shroud 51 and the outboard tip 45 of an airfoil 25, as these components might be in a disassembled condition. FIG. 9 illustrates a top or outboard view of the outboard tip 45 of the airfoil 25 that is shown in FIGS. 7 and 8. According to aspects of the present invention, the tip shroud 51 assembly may include a mechanical interference joint positioned between the detachable tip shroud 51 and the outboard tip 45 of the airfoil 25. In a preferred embodiment, the mechanical interference joint 55 may include a dovetail joint or the like in which a projection that is flared or has one or more tangs 59 engages a groove or slot. As used herein, a projection of this type will be referred to as a tenon 57, and the corresponding groove or slot will be referred to herein as a mortise 58. It will be appreciated that this type of mechanical interference joint allows engagement via sliding the tenon 57 into the mortise 58 from one direction and then, because of the flared configuration or tangs 59 of the tenon 57 and the profile of the mortise 58, prevents relative movement between the structures in a second direction. In the present usage of this type of joint, the dovetail joint is configure such that the flared tenon 57 engages the mortise 58 via sliding the tenon 57 circumferentially and/or axially, with the engaged joint opposing radial separation between the detachable tip shroud 51 and the outboard tip 45 of the airfoil 25.
As shown most clearly in FIG. 9, the mechanical interference or dovetail joint 55 may include a plurality of the tenon 57/mortise 58 pairings. In certain preferred embodiments, between two and four such pairings are provided.
It will be appreciated that, with certain mechanical interference or dovetail joints, an assembly opening 61 may be necessary for engaging the tenon 57 with the mortise 58. The assembly opening 61 may be positioned adjacent to the mortise 58. The assembly opening 61 is sized such that it may accept the flared tenon 57 so that, during installation, the flared tenon 57 may be brought to the radial height of the mortise 58 and slidably engaged therein. In the example shown, the assembly opening 61 is configured so that the tenon 57 may be brought inboard until it aligns with the mortise 58 so that it may then be slid into place. Once slid into place, it will be appreciated that the narrowing profile of the mortise 58 forms an interlock with the flared tenon 57 that restricts the movement of the tip shroud 51 in the radial direction.
FIG. 10 is a side view of the detachable tip shroud 51 and the rotor blade 16 of FIGS. 7 through 9 as they might be during a point in the assembly process, while FIG. 11 shows the tip shroud 51 and the rotor blade 16 once the assembly is complete. It will be appreciated that, once the detachable tip shroud 51 is properly fitted in its place, it will visibly appear to be a conventional tip shroud since the connecting features are not exposed to the gas path. In addition, it will be appreciated that the interlocking dovetail joint forms effective resistance against the tensional stresses that are applied to the interface between tip shroud and airfoil during operation. Unless specifically stated otherwise herein, the number and placement of the tangs, the flared profile, or other interlocking structure may depend upon design criteria associated with different applications.
FIG. 12 is a side view of a detachable tip shroud 51 and rotor blade 16 assembly in a disassembled condition according to certain alternative embodiments of the present application. In this case, instead of having multiple tenon 57/mortise 58 pairings, the flared tenon 57 is formed as an elongated rail. The mortise 58 in this case may take the form of an elongate groove. In certain aspects, this alternative embodiment may provide a way of maintaining the robustness of the interlocking structure, while also removing the necessity of the assembly openings 61 that were required in the embodiment discussed above.
In certain other preferred embodiments, such as the one shown in FIG. 13, the tenon 57/mortise 58 pairing may take an alternative configuration. In this case, the tenon 57 has a pin-like configuration that includes a flared or wider head, and the mortise 58 has a corresponding profile to allow sliding engagement. An assembly opening 61 would be positioned adjacent thereto. As also shown in FIG. 13, the mortise 58 may be disposed on the outboard tip 45 of the airfoil 25, and the flared tenons 57 project from an inboard surface 53 of the tip shroud 51. In an alternative embodiment, this configuration may be reversed, an example of which is illustrated in FIG. 14. Specifically, the flared tenons 57 project from the outboard tip 45 of the airfoil 25 and the mortises 58 are disposed on the inboard surface 53 of the detachable tip shroud 51. It will be appreciated that, unless otherwise specifically stated, such reversal may be possible with any of the other embodiments described or shown in the other figures.
In FIG. 15, a top or outboard view of the airfoil 25 is provided, which has a profile of a tip shroud 51 superimposed on to it. This illustration is meant to illustrate the direction of sliding engagement of dovetail joint 55 relative to the direction of rotation of the rotor blade 16, which is in accordance with certain preferred embodiments of the present invention. As stated above, the tenon 57 and the mortise 58 may be configured such that the tenon 57 slidably engages the mortise 58 with axial movement, circumferential movement, or movement that has both axial and circumferential components. It will be appreciated that movement that has both axial and circumferential components may include rotational movement in which engagement includes the detachable tip shroud is rotated about a radial axis. In a preferred embodiment, the tenon 57 and the mortise 58 may be configured such that the tenon 57 slidably engages the mortise 58 with circumferential movement (which is indicated by arrow 92) that is opposite the direction of rotation for the rotor blade 16 once it is installed and operating within a turbine engine (which is indicated by arrow 93). It will be appreciated that by configuring the sliding engagement in this manner, the rotation of the rotor blade 16 will naturally resist movement of the detachable tip shroud 51 that would bring the tenons 57 toward the adjacent assembly openings 61. Once the dovetail connections of the detachable tip shrouds 51 are fully engaged, the tip shrouds generally will be locked into place using any conventional method, such as welding, brazing, pinning, peening, bolting or any other method (not shown). The alignment of the sliding engagement of the dovetail connection so that the rotation of the rotor blade resists the tenons 57 from movement toward the assembly openings 61 provides a means to further protect or safeguard against the tip shroud 51 becoming dislodged during engine operation, which can lead to severe damage to the turbine engine.
In accordance with other embodiments of the present invention, as illustrated in FIGS. 16 through 19, the mechanical interference joint 55 may include a pin configuration. The pin configuration may include the tip shroud 51 and the outboard tip 45 of the airfoil 25 having structure that overlaps radially. This overlapping structure may then be pinned via a pin 63 that extends in the circumferential and/or axial direction. FIGS. 16 and 17 illustrate a configuration in which a pin 63 extends circumferentially, while FIGS. 18 and 19 illustrate a configuration in which a pin 63 extends axially. In one preferred embodiment, the pin configuration of the present invention includes one or more tabs 64 that extend or project from the inboard surface 53 of the tip shroud 51. The tabs 64 are configured to engage corresponding slots 65 formed in the outboard tip 45 of the airfoil 25. The tabs 64 may include an aperture formed therethrough. The sidewalls of the slots 65 may also include openings or apertures. The apertures of the tabs 64 and the apertures of the sidewalls of the slots 65 may be configured such that they align once the tabs 64 is fitted or seated into the slots 65. In this manner, the aligned apertures may form a pin channel or channel 66 into which the pin 63 is inserted during assembly. As shown in both FIGS. 16 and 17, the pin channel may include an opening formed through a pressure sidewall 26, a suction sidewall 27, or both the pressure sidewall 26 and the suction sidewall 27. It will be appreciated that the opening of the channel 66 provides an inlet for the pin 63 for assembly. In another embodiment, the pin configuration may include one or more tabs 64 projecting from the outboard tip 45 of the airfoil 25, which is configured to engage corresponding slots 65 formed in an inboard surface 53 of the detachable tip shroud 51. In such embodiments, a pin channel 66 may be formed in the manner described above, i.e., by configuring aligning apertures.
In an alternative arrangement, as illustrated in FIG. 20, the pin configuration may include one or more radial pins 67 that extend through the tip shroud 51 from a position on an outboard surface 52 of the tip shroud 51. Specifically, the radial pins 67 may be configured to engage corresponding opening 68 formed in the outboard tip 45 of the tip shroud 51. In one arrangement, the openings 68 and the radial pins 67 may be threaded such that upon full engagement, the heads of the pins 67 contact the outboard surface 52 of the tip shroud 51, thereby holding the tip shroud 51 secure against the outboard tip 45 of the airfoil 25.
It will be appreciated that in some of the described mechanical interference joints 55, the connection between the detachable tip shrouds 51 and the airfoil 25 may be enhanced via projections or stems that extend radially from the outboard tip 45 of the tip shroud 51 and which are formed integrally thereto. This type of structure will be referred to herein as integral stems 69. Accordingly, in cases where the tenons 57 of the dovetail connection extend from the outboard tip 45 of the airfoil 25, the tenons 57 may be integrally formed as part of the airfoil 25. It will be appreciated that this configuration may be employed to structurally enhance the connection made between the tip shroud 51 and the rotor blade 16. Similarly, in the case of a pin connection type of mechanical interference joint 55, any tabs that extend from the outboard tip 45 of the airfoil 25 may be formed as an integral part of the airfoil 25.
Turning now to FIGS. 21 and 22, an alternative type of mechanical interference joint 55 in accordance with embodiments of the present invention is illustrated. The joint in this case also includes an integral stem 69, which, as stated above, may be employed to enhance the connection made between the airfoil 25 and the rotor blade 16. While the usage of an integral stem 69 may provide a strong connection between the detachable tip shroud 51 and the airfoil 25, it also may be used to provide structure that doubles as a seal rail 38 on the outboard surface 52 of the tip shroud 51. As one of ordinary skill in the art will appreciate, one or more seal rails 38 may be located on the outboard surface 52 of the tip shroud 51 which are used to create a torturous path seal between the outboard surface 45 of the tip shroud 51 and projections that extend from the stationary structure that surrounds the tip shroud. FIG. 21 illustrates a configuration in which two integral stems 69 are used with a locking bar 71 so to form a robust connection between the detachable tip shroud 51 and the airfoil 25. As shown more clearly in FIG. 22, the integral stem 69 may include a looped rail configuration, which will be referred to herein as “looped rail 69”. The looped rail 69, as illustrated, may include two radially extending posts that are connected by a crossbar. The radially extending posts of the looped rail 69 may be formed with a predetermined radial height such that the crossbar is offset a predetermined distance from the outboard tip 45 of the airfoil 25. Shaped as it is in this provided example, the looped rail 69 may define a rectangular opening or a slot therethrough, which will be referred to herein as a “rail slot 70.”
In a preferred embodiment, two parallel looped rails 69 may be included. In the preferred embodiment, the looped rails 69 may be circumferentially aligned, though other alignments are possible. The two looped rails 69 may be approximately parallel to each other and axially spaced apart, though this is not required. The detachable tip shroud 51 may be configured with an opening 72 through which the looped rails 69 may pass. The opening 72 will allow, during assembly, for the detachable tip shroud 51 to slide over the looped rails 69 and attain a seated position upon the outboard tip 45 of the airfoil 25. The configuration of the opening 72 and the posts of the looped rails 69 may be configured so to oppose relative circumferential and axial movement between the detachable tip shroud 51 and the airfoil 25 once the tip shroud 51 is seated. And, once the tip shroud 51 is seated upon the airfoil 25, the locking bar 71 may be inserted through the rail slots 70. Upon insertion, the locking bar 71 may be configured to engage the outboard surface 52 of the tip shroud 51 and the crossbar of the looped rail 69. In this manner, the integral step opposes tension forces between the tip shroud 51 and airfoil 25. It will be appreciated that the locking bar 71 may be fixed circumferentially and axially via any type of conventional means of attachment, such as peening, bolting, brazing, or welding.
As stated, the looped rail 69 may be aligned in the circumferential direction of the combustion turbine engine, as shown in FIG. 21. In an alternative arrangement, the looped rail 69 may be aligned in the axial direction. In either case, as illustrated in FIGS. 21 and 22, the looped rail 69 may be configured to serve as a seal rail or, at least, integrated into the seal rail structure. As mentioned, the seal rail on the tip shroud 51 discourages leakage across the top of the rotor blades 16. It will be appreciated that, in an alternative embodiment, a single looped rail 69/single seal rail may be used.
In another embodiment, the rail slot 70 and the locking bar 71 may be configured such that locking bar 71 slidably engages the rail slot with axial movement, circumferential movement, or movement that has both axial and circumferential components. It will be appreciated that movement that has both axial and circumferential components may include rotational movement.
The present invention also includes a method of manufacturing a rotor blade for use in the turbine of a combustion turbine engine. This method of manufacturing may include the steps of manufacturing a rotor blade 16 and, separately, a tip shroud 51 that is not integral to the rotor blade 16. The rotor blade 16 and the tip shroud 51 may be manufactured having corresponding means for attaching to the other, the several kinds of which are outlined above. That is, the rotor blade 16 may be constructed with connecting means at the outboard tip 45 of the airfoil 25, and the tip shroud 51 may be constructed having corresponding connecting means at an inboard surface 53 of the tip shroud 51. The method of the present invention then may include the step of connecting the tip shroud 51 to the airfoil 25 via the connecting means.
It will be appreciated that the detachable tip shroud 51 of the present invention offer several advantages that are not found in the prior art. For example, tip shrouds, because they are currently an integral component of the rotor blade, must be designed so that they meet the desired part life of the rotor blade. Tip shrouds which are detachable may be replaced at shorter intervals, which may mean the difference in replacing tip shrouds at several thousands of hours of operation instead of several ten thousands of hours of operation. Such flexibility would allow for more aggressive designs. For instance, the tip shroud may be made larger for aerodynamic purposes with the knowledge that they will be replaced before the increased stresses associated with the size bring about issues of fatigue or creep. In addition, the quicker replacement interval may allow the usage of thinner tip shrouds, which, though they may wear quicker, they also cause less stress to the airfoil during operation.
Detachable tip shrouds also may have significant economic advantages. For example, detachable tip shrouds may be manufactured using materials different from those used in the rotor blade (i.e., ceramic based or different alloys), which may allow the usage of cheaper materials. As one of ordinary skill in the art will appreciate, manufacturing tip shrouds separately from rotor blades would allow for less expensive casting techniques for the formation of interior cooling channels within the tip shroud. Specifically, what before was a problematic and delicate casting process, which, essentially, was due to the large size of the one piece rotor blade casting and the intricate cooling channels of the tip shroud, is much less costly if the tip shroud may be cast separately. This also will allow for the creation of more intricate cooling schemes within the tip shroud as well as permitting the use of different casting methods for the manufacture of the tip shroud and the rotor blade. Additionally, detachable tip shrouds allow for efficiencies in repairing rotor blades. Since the tip shroud is not connected to the rotor blade, ease of access is enhanced for certain repairs. And, of course, a worn or damaged tip shroud may be conveniently replaced without replacing or disposing of the rotor blade. It will be appreciated that additive manufacturing processes may be used to manufacture the tip shroud.
While the 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 to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A rotor blade for use in a turbine of a turbine engine, the rotor blade comprising an airfoil that extends from a connection with a root, the airfoil including a pressure sidewall and a suction sidewall that define an outer periphery and an outboard tip, the rotor blade further comprising:

a tip shroud assembly disposed at the outboard tip of the airfoil;

wherein the tip shroud assembly includes a non-integral tip shroud.

2. The rotor blade according to claim 1, wherein the tip shroud assembly includes one of a weld and a braze connection between the non-integral tip shroud and the outboard tip of the airfoil.

3. The rotor blade according to claim 1, wherein the non-integral tip shroud comprises a detachable tip shroud.

4. The rotor blade according to claim 3, wherein the tip shroud assembly includes a mechanical interference joint formed between the detachable tip shroud and the outboard tip of the airfoil.

5. The rotor blade according to claim 4, wherein the mechanical interference joint comprises a dovetail joint in which a flared tenon engages a mortise.

6. The rotor blade according to claim 5, wherein the dovetail joint is configured such that the flared tenon engages the mortise so to oppose radial separation between the detachable tip shroud and the outboard tip of the airfoil;

wherein the flared tenon includes a tang.

7. The rotor blade according to claim 6, wherein an engaged flared tenon and mortise comprise a tenon-mortise pairing; and

wherein the dovetail joint comprises a plurality of tenon-mortise pairings.

8. The rotor blade according to claim 6, wherein the flared tenon comprises an elongated rail and the mortise comprises an elongated groove; and

wherein the flared tenon engages the mortise via sliding in a direction of a longitudinal axis of the elongated rail.

9. The rotor blade according to claim 6, wherein the tenon and the mortise are configured such that the tenon slidably engages the mortise with one of: axial movement; circumferential movement; and movement that has both axial and circumferential components.

10. The rotor blade according to claim 9, further comprising an assembly opening that resides adjacent to the mortise;

wherein the assembly opening comprises an opening configured to accept the flared tenon so that, during installation, the flared tenon may be brought inboard to a radial height of the mortise and slidably engaged therein.

11. The rotor blade according to claim 9, wherein the tenon and the mortise are configured such that the mortise slidably engages the tenon with circumferential movement that is opposite a direction of rotation for the rotor blade in operation.

12. The rotor blade according to claim 6, wherein the mortise is disposed on the outboard tip of the airfoil and the flared tenon projects from an inboard surface of the tip shroud; and

wherein the flared tenons engage the mortises via rotation movement of the tips shroud relative to the airfoil.

13. The rotor blade according to claim 6, wherein the flared tenon projects from the outboard tip of the airfoil and the mortise is disposed on the inboard surface of the tip shroud.

14. The rotor blade according to claim 4, wherein the mechanical interference joint comprises a pin configuration.

15. The rotor blade according to claim 14, wherein the pin configuration comprises a radial pin that extends through the tip shroud from a position on an outboard surface of the tip shroud, the radial pin engaging an opening formed in the outboard tip of the tip shroud.

16. The rotor blade according to claim 14, wherein the pin configuration includes the tip shroud and the outboard tip of the airfoil having structure that overlaps radially, and a pin extends in the circumferential and/or axial direction through the structure that overlaps radially;

wherein the pin configuration comprises a tab projecting from an inboard surface of the tip shroud that is configured to engage a slot formed in the outboard tip of the airfoil;

wherein the tab includes an aperture formed therethrough and the slot includes an aperture formed in a sidewall, the aperture of the tab and the aperture of the sidewall aligning upon fitting the tab in the slot so to form a pin channel;

wherein the pin extends through the pin channel; and

wherein the pin channel includes an opening formed through at least one of the pressure sidewall and the suction sidewall of the airfoil, the opening being configured as an insertion point for the pin during assembly and disassembly of the mechanical interference joint.

17. The rotor blade according to claim 14, wherein the pin configuration includes the tip shroud and the outboard tip of the airfoil having structure that overlaps radially, and a pin extends in the circumferential and/or axial direction through the structure that overlaps radially;

wherein the pin configuration comprises a tab projecting from the outboard tip of the airfoil that is configured to engage a slot formed in an inboard surface of the tip shroud;

wherein the tab includes an aperture formed therethrough and the slot includes an aperture formed in a sidewall of the slot, the aperture of the tab and the apertures of the sidewall aligning upon engagement of the tab in the slot so to form a pin channel; and

wherein the pin extends through the pin channel.

18. The rotor blade according to claim 4, wherein the mechanical interference joint includes an integral stem extending from the outboard tip of the airfoil, wherein the integral stem comprising structure formed integrally to the airfoil that is used to connect the detachable tip shroud to the airfoil; and

wherein the integral stem comprises a tab that includes an aperture formed therethrough, wherein the mechanical interference joint comprises a pin configuration.

19. The rotor blade according to claim 4, wherein the mechanical interference joint includes an integral stem extending from the outboard tip of the airfoil, wherein the integral stem comprising structure formed integrally to the airfoil that is used to connect the detachable tip shroud to the airfoil;

wherein the integral stem comprises a looped rail, the looped rail including two radially extending posts that are connected by a crossbar, the radially extending posts having a predetermined radial height such that the crossbar is offset a predetermined distance from the outboard tip of the airfoil; and

wherein the detachable tip shroud is configured having an opening formed therein through which the looped rail passes, which is configured to allow the detachable tip shroud to slide inboard to a seated position atop the outboard tip of the airfoil

20. The rotor blade according to claim 19, wherein the slot and the posts are configured to oppose relative circumferential and axial movement between the detachable tip shroud and the airfoil once the detachable tip shroud comprises the seated position;

further comprising a locking bar configured to pass between a rail slot of the rail, the locking bar configured to engage an outboard surface of the tip shroud and the crossbar so to oppose radial separation between the detachable tip shroud and the outboard tip of the airfoil.

21. The rotor blade according to claim 20, wherein the looped rail is aligned with a circumferential direction of the turbine engine; and

wherein the looped rail is configured to comprise a seal rail.

22. The rotor blade according to claim 20, further comprising an additional looped rail;

wherein a first looped rail engages a first end of the locking bar and a second looped rail engages a second end of the locking bar.

23. The rotor blade according to claim 3, wherein an interior cooling passage extends through the airfoil from a connection to an air source made through the root of the rotor blade to an outlet formed at the outboard tip of the airfoil; and

wherein the detachable tip shroud includes an interior cooling passage that extends from an inlet formed at an inboard surface of the tip shroud;

wherein the outlet formed at the outboard tip of the airfoil and the inlet formed at the inboard surface of the detachable tip shroud are configured to align once the detachable tip shroud is fitted to the airfoil.

24. A method of manufacturing a rotor blade for use in a turbine of a combustion turbine engine, the rotor blade comprising an airfoil that extends from a connection with a root, the airfoil including a pressure sidewall and a suction sidewall that define an outer periphery and an outboard tip, the method comprising the steps of:

manufacturing the rotor blade with connecting means at the outboard tip of the airfoil;

manufacturing the tip shroud to have corresponding connecting means at an inboard surface of the tip shroud; and

connecting the tip shroud to the airfoil via the connecting means of the airfoil and the corresponding connecting means of the tip shroud;

wherein the connecting means of the airfoil and the connecting means of the tip shroud together comprise a mechanical interference joint.

25. The method according to claim 24, further comprising the steps of:

during the step of manufacturing the rotor blade, casting interior cooling channels within the rotor blade; and

during the step of manufacturing the tip shroud, casting interior cooling channels within the tip shroud.