TURBINE ROTOR BLADES HAVING MID-SPAN SHROUDS
A rotor blade for use in a turbine of a combustion turbine engine is described. The rotor blade may include an airfoil that extends from a connection with a root. The rotor blade may further include a mid-span shroud configured to engage a corresponding mid-span shroud on at least one neighboring rotor blades during operation. Outboard of the mid-span shroud, the airfoil may include an outboard region that is substantially hollow, and inboard of the mid-span shroud, the airfoil may include an inboard region that is substantially solid.
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The present application relates generally to apparatus, methods and/or systems concerning the design and operation of turbine rotor blades. More specifically, but not by way of limitation, the present application relates to apparatus and systems pertaining to turbine rotor blades and configurations of turbine rotor blades having mid-span shrouds.
In a combustion turbine engine, it is well known that air pressurized in a compressor is used to combust a fuel in a combustor to generate a flow of hot combustion gases, whereupon such gases flow downstream through one or more turbines so that energy can be extracted therefrom. 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 generally concave pressure side and generally convex 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 stationary shroud for minimizing leakage therebetween of the combustion gases flowing downstream between the turbine blades.
Shrouds at the tip of the airfoil or tip shrouds often are implemented on aft stages or rotor blades to provide damping and reduce the over-tip leakage of the working fluid. Given the length of the rotor blades in the aft stages, the damping function of the tip shrouds provides a significant performance benefit. However, taking full advantage of the damping function is difficult considering the weight that the tip shroud adds to the assembly and the other design criteria which include enduring thousands of hours of operation exposed to high temperatures and extreme mechanical loads. Thus, while large tip shrouds are desirable because they seal the gas path more effectively and may be designed to provide more significant connection between neighboring rotor blades, which may improves damping, one of ordinary skill in the art will appreciate that larger tip shrouds are troublesome because of the increased pull load on the rotor blade.
Another consideration is that the output and efficiency of gas turbine engines improve as the size of the engine and, and more specifically, the amount of air able to pass through it increase. The size of the engine, however, is limited by the operable length of the turbine blades, with longer turbine rotor blades enabling enlargement of the flow path through engine. Longer rotor blades, though, incur increased mechanical loads, which place further demands on the blades and the rotor disc that holds them. Longer rotor blades also decrease the natural vibrational frequencies of the blades during operation, which increases the vibratory response of the rotor blades. This additional vibratory load place even further demands on rotor blade design, which may further shorten the life of the component and, in some cases, may cause vibratory loads that damage other functions of the turbine engine. One way to address the vibratory load of longer rotor blades is through the use of shrouds that connect adjacent rotor blades to each other. As mentioned, though, the added weight of the shroud may negate much of the benefit.
One way to address this is to position the shroud lower on the airfoil of the rotor blade. That is, instead of adding the shroud to the tip of the rotor blade, the shroud is positioned near the middle radial portion of the airfoil. As used herein, such a shroud will be referred to as a “mid-span shroud.” At this lower (or more inboard) radius, the mass of the shroud causes a reduced level of stress to the rotor blade. However, this type of shroud leaves a portion of the airfoil of the rotor blade unrestrained, which is the portion of the airfoil that extends outboard of the mid-span shroud. This cantilevered portion of the airfoil typically results in lower frequency vibration and increased vibratory loads, which may be damaging to the engine. A novel rotor blade design that reduced or limited these loads would have value in the market for such products.
BRIEF DESCRIPTION OF THE INVENTIONThe present application thus describes a rotor blade for use in a turbine of a combustion turbine engine. The rotor blade may include an airfoil that extends from a connection with a root. The airfoil may include a concave pressure sidewall and a convex suction sidewall extending axially between corresponding leading and trailing edges and radially between a root and an outboard tip. The rotor blade may further include a mid-span shroud configured to engage a corresponding mid-span on at least one neighboring rotor blades during operation. Outboard of the mid-span shroud, the airfoil includes an outboard region that is substantially hollow. Inboard of the mid-span shroud, the airfoil includes an inboard region that is substantially solid.
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.
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:
As an initial matter, it will be appreciated that to discuss the invention of the present application, it may be necessary to select terminology to refer to and describe particular components within a combustion turbine engine. 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, or, when referring to components within a combustor, the center axis of the combustor.
By way of background, referring now to the figures,
In use, 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.
The mid-span shroud 51, according to the present invention, may be defined broadly any shroud that is positioned inboard of an outboard tip 41 of the airfoil 25 and outboard of a platform 24. According to certain embodiments of the present invention, a mid-span shroud 51 is one positioned near the approximate radial center of the airfoil 25.
A mid-span shroud 51 according to present invention also may be defined as a shroud disposed within a range of radial positions on the airfoil 25. According to certain embodiments of the present invention, the range of positions of a mid-span shroud 51 is defined between an inboard boundary of approximately 25% of the radial height of the airfoil 25 and an outboard boundary of approximately 75% of the radial height of the airfoil 25. According to other embodiments of the present invention, as may be defined by the appended claims, the range of positions of a mid-span shroud 51 is defined between an inboard boundary of approximately 33% of the radial height of the airfoil 25 and an outboard boundary of approximately 66% of the radial height of the airfoil 25.
As to other characteristics of the mid-span shroud 51 of the present invention, the mid-span shroud 51 may described as a circumferentially extending projection that protrudes from at least one of the pressure sidewall 26 and the suction sidewall 27 of the airfoil 25. As shown in
As mentioned, the hollow region 61 of the outboard region 59 may include a hollow chamber 65. As illustrated via the dotted lines of
According to the present invention,
The outboard region 59 of the airfoil 25 may be described as having a “hollowness percentage” that defines the percentage or portion of the volume of the outboard region 59 that is comprised of hollow region 61. In a similar manner, the inboard region 58 of the airfoil 25 may be described as having a “solidness percentage” that defines the portion of the volume of the inboard region 58 is comprised of solid region 62. In other embodiments of the present invention, the hollowness percentage of the outboard region 59 is at least 70%, and the solidness percentage of the inboard region 58 is at least 90%. In other embodiments of the present invention, the hollowness percentage of the outboard region 59 is at least 80%, and the solidness percentage of the inboard region 58 is at least 95%. In still other embodiments of the present invention, the hollowness percentage of the outboard region 59 is at least 90%, and the solidness percentage of the inboard region 58 is 100%.
In certain embodiments of the present invention, the solid region 62 of the outboard region 59 is limited to: a) a thin outer wall that along an inner surface defines the hollow chamber 65 in the airfoil 25 and along an outer surface defines the suction sidewall 27 and pressure sidewall 26 of the airfoil 25; and b) connectors 66 that span the hollow chamber 65 structurally connecting the pressure sidewall 26 to the suction sidewall 25. In such cases, the hollow region 61 of the inboard region 58 may be limited to a few interior cooling passages 81 configured to transport coolant across the inboard region 58 from a coolant source formed through the root 21 to the hollow chamber 65 of the outboard region 59. In other embodiments, the solid region 62 of the outboard region 59 is limited to a thin outer wall that along an inner surface defines a hollow chamber 65 in the airfoil 25 and along an outer surface defines the suction sidewall 27 and pressure sidewall 26 of the airfoil 25. In such cases, the inboard region 58 may have no hollow region 61.
In certain embodiments, the outboard tip 41 of the airfoil 25 has a tip plate 76 that encloses the hollow chamber 65 of the airfoil 25, as illustrated in
It will appreciated that, pursuant to the several embodiments discussed above, the present invention provides a manner by which the vibratory response of turbine rotor blades 16 may be reduced so to limit the damaging mechanical loads, which may be used, in particular, to enable the lengthening of rotor blades so that greater engine efficiencies are achieved. That is, the present invention teaches a method by which turbine rotor blades may be snubbed via mid-span shrouds 51 and configured internally to limit the vibratory response of the cantilevered portion that extends beyond the mid-span shroud 51. The method includes increasing the stiffness and decreasing the mass of the portion of the airfoil 25 outboard of the mid-span shroud 51 by hollowing out a significant portion of the region 25 and, in some embodiments, providing connecting structure through the hollowed region, while the region of the airfoil 25 that is inboard of the mid-span shroud 51 remains solid. In this manner, natural frequencies of the structure may be raised and harmful vibratory responses avoided, thereby allowing for longer turbine blades, which, in turn, may be used to enable larger turbine engines having greater output and efficiency.
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 combustion turbine engine, the rotor blade comprising an airfoil that extends from a connection with a root, the airfoil including a concave pressure sidewall and a convex suction sidewall extending axially between corresponding leading and trailing edges and radially between the root and an outboard tip, the rotor blade further comprising:
- a mid-span shroud configured to engage a corresponding mid-span shroud on at least one neighboring rotor blade during operation;
- wherein: outboard of the mid-span shroud, the airfoil includes an outboard region that is substantially hollow; and inboard of the mid-span shroud, the airfoil includes an inboard region that is substantially solid.
2. The rotor blade of claim 1, wherein the mid-span shroud includes a circumferentially extending projection from at least one of the pressure sidewall and the suction sidewall of the airfoil.
3. The rotor blade of claim 1, wherein the mid-span shroud comprises a circumferential projection from each of the pressure sidewall and the suction sidewall of the airfoil;
- wherein the mid-span shroud comprises a pressure side contact face at a distal end of the circumferential projection from the pressure sidewall and a suction side contact face at a distal end of the circumferential projection from the pressure sidewall;
- wherein, upon installation, the pressure side contact face is configured to form a first shroud-to-shroud interface with the suction side contact face of a first neighboring rotor blade of a same design as the rotor blade; and
- wherein, upon installation, the suction side contact face is configured to form a second shroud-to-shroud interface with the pressure side contact face of a second neighboring rotor blade of the same design as the rotor blade.
4. The rotor blade of claim 3, wherein the mid-span shroud comprises a shroud that is positioned inboard of an outboard tip of the airfoil and outboard of a platform of the rotor blade.
5. The rotor blade of claim 3, wherein the mid-span shroud comprises a shroud that is disposed within a range of positions on the airfoil; and wherein the range of positions is defined between an inboard boundary at 25% of a radial height of the airfoil and an outboard boundary at 75% of the radial height of the airfoil.
6. The rotor blade of claim 3, wherein the mid-span shroud comprises a shroud that is disposed within a range of positions on the airfoil; and wherein the range of positions is defined between an inboard boundary at 33% of a radial height of the airfoil and an outboard boundary at 66% of the radial height of the airfoil.
7. The rotor blade of claim 5, wherein the outboard region of airfoil comprises a portion of the airfoil that is outboard of the mid-span shroud, and wherein the inboard region of the airfoil comprises a portion of the airfoil that is inboard of the mid-span shroud;
- wherein a hollow region comprises a region within the airfoil that is hollow; and
- wherein a solid region comprises a region within the airfoil that is solid material.
8. The rotor blade of claim 7, wherein the hollow region of the outboard region of the airfoil comprises a hollow chamber.
9. The rotor blade of claim 8, wherein the hollow chamber comprises a connector extending therethrough that structurally connects the pressure sidewall to the suction sidewall of the airfoil.
10. The rotor blade of claim 9, wherein the connector comprises a plurality of ribs, a plurality of which extends across the hollow chamber from the suction sidewall to the pressure sidewall of the airfoil.
11. The rotor blade of claim 9, wherein the connector comprises a plurality of pins, a plurality of which extends across the hollow chamber from the suction sidewall to the pressure sidewall of the airfoil.
12. The rotor blade of claim 9, wherein the connector comprises an internal wall that divides the hollow chamber into a plurality of hollow chambers.
13. The rotor blade of claim 7, wherein the outboard region of the airfoil comprises a hollowness percentage that defines what portion of a volume of the outboard region is the hollow region; and
- wherein the inboard region of the airfoil comprises a solidness percentage that defines what portion of a volume of the inboard region is the solid region.
14. The rotor blade of claim 13, wherein the outboard region being substantially hollow is defined as the outboard region having a hollowness percentage of at least 70%; and
- wherein the inboard region being substantially solid is defined as the inboard region having the solidness percentage of at least 90%.
15. The rotor blade of claim 13, wherein the outboard region being substantially hollow is defined as the outboard region having a hollowness percentage of at least 80%; and
- wherein the inboard region being substantially solid is defined as the inboard region having the solidness percentage of at least 95%.
16. The rotor blade of claim 13, wherein the outboard region being substantially hollow is defined as the outboard region having a hollowness percentage of at least 90%; and
- wherein the inboard region being substantially solid is defined as the inboard region having the solidness percentage of 100%.
17. The rotor blade of claim 7, wherein the solid region of the outboard region is limited to: a) a thin outer wall that along an inner surface defines a hollow chamber in the airfoil and along an outer surface defines the suction sidewall and pressure sidewall of the airfoil; and b) pins that span the hollow chamber structurally connecting the pressure sidewall to the suction sidewall; and
- wherein the hollow region of the inboard region is limited to narrow interior cooling passages configured to transport coolant across the inboard region from a coolant source formed through the root of the rotor blade to the hollow chamber of the outboard region.
18. The rotor blade of claim 7, wherein the solid region of the outboard region is limited to a thin outer wall that along an inner surface defines a hollow chamber in the airfoil and along an outer surface defines the suction sidewall and pressure sidewall of the airfoil; and
- wherein the inboard region comprises no hollow region.
19. The rotor blade of claim 18, wherein the outboard tip of the airfoil comprises a tip plate that encloses the hollow chamber of the airfoil.
20. The rotor blade of claim 19, wherein the tip plate includes one or more film cooling apertures that, during operation, are configured to meter a release of the coolant flowing through the hollow chamber of the airfoil.
21. The rotor blade of claim 18, wherein the outboard tip of the airfoil comprises an open face opening to the hollow chamber of the airfoil.
22. A combustion turbine engine that includes:
- a rotor blade comprising an airfoil that extends from a connection with a root, the airfoil including a concave pressure sidewall and a convex suction sidewall extending axially between corresponding leading and trailing edges and radially between the root and an outboard tip, the rotor blade further comprising: a mid-span shroud configured to engage a corresponding mid-span shroud on at least one neighboring rotor blade during operation; wherein, outboard of the mid-span shroud, the airfoil includes an outboard region that is substantially hollow, and, inboard of the mid-span shroud, the airfoil includes an inboard region that is substantially solid; wherein a hollow region comprises a region within the airfoil that is hollow, and wherein a solid region comprises a region within the airfoil that is solid material; wherein the outboard region of the airfoil comprises a hollowness percentage that defines what portion of a volume of the outboard region is the hollow region; wherein the inboard region of the airfoil comprises a solidness percentage that defines what portion of a volume of the inboard region is the solid region; and wherein the outboard region being substantially hollow is defined as the outboard region having a hollowness percentage of at least 70% and wherein the inboard region being substantially solid is defined as the inboard region having the solidness percentage of at least 90%.
Type: Application
Filed: Dec 21, 2012
Publication Date: Sep 11, 2014
Applicant: General Electric Company (Schenectady, NY)
Inventor: General Electric Company
Application Number: 13/725,617
International Classification: F01D 5/22 (20060101); F01D 5/18 (20060101);