Buffering shroud configuration

Abstract

The invention is entitled "Buffer Shroud Configuration". The invention discloses a blade (16) comprising an airfoil (25) including a platform (24), a concave pressure side wall (55), and a convex suction side wall (56) extending axially between respective leading and trailing edges and radially between a root (21) and an outboard tip (41). The blade (16) further comprises: an angled outboard buffer shroud (52) positioned on the airfoil (25), the angled outboard buffer shroud (52) disposed at an angle a defined by an arc on the angled outboard buffer shroud (52) and the platform (24) of the blade (16); an angled inboard buffer shroud (53) positioned on the airfoil (25), the angled inboard buffer shroud (53) disposed at an angle defined by an arc on the angled inboard buffer shroud (53) and the platform (24) of the blade (16). The angle a is independently disposed relative to the angle.

Description

BACKGROUND

[0001] The present embodiments relate generally to apparatuses, methods, and / or systems relating to turbine rotor blades. More particularly, but not by way of limitation, the present application relates to apparatuses and assemblies relating to turbine rotor blades having multiple bumper shrouds. SUMMARY

[0002] A blade for a turbine is set forth. The blade includes an airfoil including a platform, a concave pressure side wall, and a convex suction side wall extending axially between corresponding leading and trailing edges and radially between a root and an outboard tip. The blade further includes an angled outboard bumper shroud positioned on the airfoil, the angled outboard bumper shroud disposed at an angle a defined by an arc on the angled outboard bumper shroud and the platform of the blade; an angled inboard bumper shroud positioned on the airfoil, the angled inboard bumper shroud disposed at an angle b defined by an arc on the angled inboard bumper shroud and the platform of the blade; and a platform gap defined between the platform of the airfoil and the angled outboard bumper shroud and the angled inboard bumper shroud. The angle a is independently set. The angle b is independently set.

[0003] A gas turbine engine having a turbine including a row of circumferentially spaced apart blades is further described. Each of the blades can include an airfoil including a platform, a concave pressure side wall, and a convex suction side wall extending axially between corresponding leading and trailing edges and radially between a root and an outboard tip. The blade further includes an angled outboard bumper shroud positioned on the airfoil, the angled outboard bumper shroud disposed at an angle a defined by an arc on the angled outboard bumper shroud and the platform of the blade; an angled inboard bumper shroud positioned on the airfoil, the angled inboard bumper shroud disposed at an angle b defined by an arc on the angled inboard bumper shroud and the platform of the blade; and a platform gap defined between the platform of the airfoil and the angled outboard bumper shroud and the angled inboard bumper shroud. The angle a is independently set. The angle b is independently set.

[0004] These and other features of the present application will become apparent after a careful reading of the detailed description of the preferred embodiments with appropriate Figs. attached.

[0005] The exemplary aspects of the disclosure are designed to address the problems described herein and / or other issues not discussed. BRIEF DESCRIPTION OF DRAWINGS

[0006] These and other features, along with the various advantages of the present embodiments, are more fully understood from the following detailed description of the application when considered in conjunction with the accompanying drawings, in which:

[0007] These and other features, along with the various advantages of the present embodiments, are more fully understood from the following detailed description of the application when considered in conjunction with the accompanying drawings, in which:Figure 1 is a schematic illustration of an exemplary combustion turbine engine in which embodiments of the present application can be used;

[0008] Figure 2 is a side view of an exemplary turbine rotor blade and stationary shroud assembly according to embodiments of the present disclosure, wherein the rotor blade includes dual bumpers independently disposed relative to one another; and

[0009] Figure 3 is a perspective view of an outboard portion of an airfoil of Figure 2

[0010] It should be noted that the drawings of the present disclosure are not necessarily drawn to scale. The drawings are intended to depict only typical aspects of the disclosure and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents similar elements between the drawings. DETAILED DESCRIPTION

[0011] While the following examples of the present embodiments can be described with reference to a particular type of turbine engine, those of ordinary skill in the art will understand that the present embodiments can not be limited to such use and are applicable to other types of turbine engines unless specifically limited thereto. Additionally, it should be understood that in describing the present embodiments, certain terminology is used that can be used to refer to certain machine components within a gas turbine engine. Where possible, generic industry terminology will be used and employed in a manner consistent with accepted meanings of the terminology. However, such terminology should not be construed in a limiting sense as those of ordinary skill in the art will understand that different terminology can often be used to refer to a particular machine component. Additionally, what can be described herein as a single component can in another context be referred to as being made up of multiple components, or what can be described herein as including multiple components can elsewhere be referred to as a single component. Therefore, in understanding the scope of the present embodiments, attention should be directed not only to the particular terminology used, but also to the description as a whole, the context in which the terminology is used, and the structure, configuration, function, and / or purpose of the components as can be understood from the description provided, particularly as can be provided in the appended claims.

[0012] ​A number of descriptive terms can be used regularly herein, and it can be helpful to define these terms at the outset of this section. Thus, unless otherwise stated, these terms and their definitions are as follows. As used herein, "downstream" and "upstream" are terms that indicate a direction relative to a flow of fluid, such as, for example, a working fluid through the compressor, combustor, and turbine sections of a gas turbine, or a flow coolant through one of the component systems of an engine. The term "downstream" corresponds to the direction of the fluid flow, while the term "upstream" refers to a direction opposite or contrary to the direction of fluid flow. Without any particularity, the terms "forward" and "aft" refer to directions relative to the orientation of the gas turbine, with "forward" referring to the forward or compressor end of the engine, and "aft" referring to the aft or turbine end of the engine. Additionally, given the construction of a gas turbine engine about a central axis, and this same type of construction in some of the component systems, terms will similarly be used to describe positions relative to the axis. In this regard, it will be understood that the term "radial" refers to movement or position perpendicular to the axis. Related to this, it can be desirable to describe relative distances from the central axis. In this case, for example, if a first component resides closer to the central axis than a second component, it will be stated herein that the first component is "radially inward" or "inboard" of the second component. On the other hand, if the first component resides further from the axis than the second component, it will be stated herein that the first component is "radially outward" or "outboard" of the second component. Additionally, it will be understood that the term "radial" refers to movement or position parallel to the axis. And finally, the term "circumferential" refers to movement or position about the axis.

[0013] In a combustion turbine engine, air pressurized in a compressor is used to combust a fuel in a combustor to generate a hot combustion gas stream, which such gas then flows downstream through one or more turbines so that energy can be extracted therefrom. According to such turbine engines, generally, a plurality of rows of circumferentially spaced apart blades extend radially outward from a supporting rotor disk. Each blade typically includes a blade mount (e.g., a dovetail that allows the blade to be assembled and disassembled in a corresponding slot in the rotor disk) and an airfoil that extends radially outward from the blade mount and interacts with a working fluid flow through the engine. The airfoil has a concave pressure side and a convex suction side that extend axially between corresponding leading and trailing edges, and radially between a root and a tip. It will be appreciated that the blade tip is closely spaced to a radially outer stationary surface for reducing leakage of the combustion gas flowing downstream therebetween.

[0014] Shrouds at the head end of the airfoils or "head end shrouds" on the aft stages or rotor blades provide a contact point at the head end, manage the grouping frequency, enable a source of damping (i.e., by connecting adjacent rotor blades at the head end), and reduce leakage of working fluid over the head end. The damping function of the head end shroud provides a significant benefit to durability given the length of the rotor blade at the aft stage. However, taking full advantage of these benefits is difficult given the weight added to the assembly by the head end shroud and other construction criteria, including the operational duty time under exposure to high temperatures and extreme mechanical loads. Thus, while large head end shrouds are desirable because of their effective way of sealing the gas path and the robust connection they can make between adjacent blades, large head end shrouds can not be ideal because the pull loads on the disk (particularly at the base of the airfoil) increase because it must support the entire load of the blade.

[0015] Another consideration is that the output and efficiency of a gas turbine engine improves with the size of the engine and more particularly the amount of air that can pass through it. However, the size of the engine can be limited by the operable length of the turbine blades, where longer turbine blades enable the expansion of the flow path through the engine. However, longer blades induce increased mechanical loads, which can place further demands on the blades and the disk that holds them. Longer blades also lower the natural frequency of vibration of the blades during operation, which increases the vibrational response of the blades. This additional vibrational load places even greater demands on the blade construction, which can limit the life of the components and in some cases can induce vibrational loads in the turbine engine. One way to address the vibrational loads of longer blades is by using shrouds that connect adjacent blades to one another.

[0016] One way to modify a blade according to the loads on it is to position a shroud at a lower position on the airfoil of the blade. That is, instead of adding a shroud to the head end of the 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 "buffer shroud." At this lower (or more inboard) radius, the mass of the shroud results in a reduced stress level of the blade. However, this type of shroud can leave a portion of the airfoil of the blade unconstrained (i.e., the portion of the airfoil that extends outboard of the buffer shroud). This cantilevered portion of the airfoil can result in lower frequency vibrations and increased vibrational loads. Thus, a blade construction that reduces or limits the loads would be of value.

[0017] Figure 1 An exemplary combustion turbine engine is shown in which embodiments of the present application can be used. It will be understood by those skilled in the art that the present embodiments are not limited to this type of use. As noted, the present embodiments can be used in combustion turbine engines, such as engines used for power generation and aircraft, steam turbine engines, and other types of rotary engines. Figure 1is a schematic illustration of a combustion turbine engine 10. Generally, combustion turbine engines operate by extracting energy from a pressurized hot gas stream produced by the combustion of fuel in a stream of compressed air. As Figure 1 shown, the combustion turbine engine 10 can be configured with an axial compressor 11 mechanically coupled to a downstream turbine section or turbine 13 by a common shaft, and a combustor 12 positioned between the compressor 11 and the turbine 12. A diffuser 14 can be provided at a transition area between the turbine 12 exhaust and an exhaust system 15. The diffuser 14 directs the exhaust stream from the turbine 12 through a flow path to the exhaust system 15. Flow in the diffuser 14, sometimes referred to as a diffuser profile, is desirably free-turbulent to reduce impingement (or equalize impingement), vibration, and to increase the efficiency of the turbine engine 10.

[0018] Figure 2 and Figure 3 respectively show side and perspective views of an illustrative turbine blade 16 including a buffer shroud 52 and 53 according to the present embodiments. The buffer shroud 52 and 53 are capable of joining to and connecting to an adjacent blade 16 at a complementary buffer interface 54. The joining of the adjacent blade 16 can occur between the buffer shroud and buffer shroud interface 54 at which the pressure side surface 55 of the airfoil and the face 56 of the suction side surface of the airfoil (opposite sides of the airfoil 25) contact each other. The buffer shroud and buffer shroud interface shown herein is schematic and is not shown in any particular configuration. The buffer shroud and buffer shroud interface shown is merely illustrative and is not intended to limit the embodiments in any way. The joining of the blades in this manner can tend to increase the natural frequency of the assembly and dampen operational vibrations, meaning the blades 16 experience less mechanical stress during operation and can degrade slowly if they experience stress and / or degrade completely. Figure 2

[0019] Figure 2 and Figure 3 illustrate aspects of the present embodiments. As Figure 2 shown, the present embodiments describe a blade 16 having an airfoil 25 with dual buffer shrouds, an outboard buffer shroud 52 and an inboard buffer shroud 53. The airfoil 25 extends from a root 21 with a platform 24 that is a substantially planar platform with rounded corners (not shown transitioning from the base 21 to the airfoil 25). Each of the outboard buffer shroud 52 and the inboard buffer shroud 53 are disposed on the blade 16 at an angle a and respectively. The angles a and ​The benefits of this buffer shroud arrangement are several, including a reduced overall head end mass, as some of this mass is repositioned closer to the axis of rotation, which reduces mechanical stresses on the airfoil. Additionally, the angled buffer shroud configuration as embodied herein can provide a reduced or substantially turbulent free flow to the diffuser 14 by the outboard buffer shroud 52 and the inboard buffer shroud 53 to reduce mechanical stresses, impingement (or balance any impingement in the turbine engine 10), vibration, all of which can reduce the operational output and efficiency of the turbine engine 10. Accordingly, the angled outboard buffer shroud 52 and the angled inboard buffer shroud 53, respectively, at angles a and b as embodied herein can improve the efficiency of the turbine engine 10.

[0020] Additionally, due to the angled buffer shroud configuration as embodied herein, the reduction in mechanical stresses on the blade and blade vibration can enable a smaller initial tip clearance between the blade at the head end 41 and its adjacent stationary structure 58, as the airfoil 25 should experience less elongation during operation. The reduced mechanical elongation on the blade 16 can also extend blade life.

[0021] The angled inboard buffer shroud 53 can be configured as a circumferentially extending protrusion from one or both of the pressure side wall 55 and the suction side wall 56 of the airfoil 25. Similarly, the angled outboard buffer shroud 52 can be configured as a circumferentially extending protrusion from one or both of the pressure side wall 55 and the suction side wall 56 of the airfoil 25. As previously discussed, each angled buffer shroud can be configured to engage an adjacent buffer shroud formed on one or both adjacent blades upon installation. It should be appreciated that the dual contact points that can be achieved by the present embodiment can advantageously limit vibration response during blade operation.

[0022] The buffer shroud as embodied in the present disclosure is set at an angle relative to the platform 24. For example, the angled outboard buffer shroud is shown in Figure 2 at an angle a. The angle a is defined between the platform 24 of the blade and a longitudinal axis that is the arc of the angled outboard buffer shroud 52. The angle a is provided in a fixed geometry. The angle a is set in a range between about 0 degrees and about 17 degrees, such as between about 5 degrees and about 15 degrees, and possibly between about 7 degrees and about 11 degrees. Preferably, the angle a is about 9 degrees for good balanced loading on the angled outboard buffer shroud 52 as embodied herein.

[0023] Similarly, the angled inboard buffer shroud 53 is angled as shown in Figure 2 . The angle is provided in a fixed geometry. The angle is defined between the platform 24 of the blade and a longitudinal axis that is the arc of the angled inboard buffer shroud 53. The angle b is provided in a fixed geometry. The angle b is set in a range between about 0 degrees and about 17 degrees, such as between about 5 degrees and about 15 degrees, and possibly between about 7 degrees and about 11 degrees. Preferably, the angle b is about 9 degrees for good balanced loading on the angled inboard buffer shroud 53 as embodied herein.​ is set in a range between about 0 degrees and about 17 degrees, for example, between about 3 degrees and about 14 degrees, and possibly between about 5 degrees and about 10 degrees. Preferably, for a well-balanced load on the angled inboard bumper fairing 53, the angle is about 7 degrees.

[0024] Thus, if as above the angle a = 9 degrees and the angle degrees, then the angle a is not equal to the angle and the angle a is greater than the angle

[0025] The angled outboard bumper fairing 52 and the angled inboard bumper fairing 53 can be formed in an integral configuration with the blade 16. For example, but by no means limiting the present embodiment, each of the angled outboard bumper fairing 52 and the angled inboard bumper fairing 53 can be cast with the blade 16, where the angled outboard bumper fairing 52 and the angled inboard bumper fairing 53 are fixed at the desired angles. Of course, if desired, the angled outboard bumper fairing 52 and the angled inboard bumper fairing 53 can be formed separately from the blade 16 and then attached to the airfoil 25 by means such as, but not limited to, welding, brazing, or other such attachment means now known or hereafter developed to form an integral configuration.

[0026] The angles of the outboard bumper fairing 52 and the inboard bumper fairing 53 are independently set relative to each other. As used herein, independently and independently set (used interchangeably) means that the angle a of the angled outboard bumper fairing 52 can be one value, and the angle of the angled inboard bumper fairing 53 can be another value. The angles and a of the outboard bumper fairing 52 and the inboard bumper fairing 53 need not be the same, and in fact can be different. The angles and a of the outboard bumper fairing 52 and the inboard bumper fairing 53 are set to balance the load on the airfoil 25, which can be able to reduce vibrations and mitigate shocks in and on the airfoil 25.

[0027] The independent angles of the outboard bumper fairing 52 and the inboard bumper fairing 53 And alpha is also able to regulate and smooth the flow over the angled outboard buffer shroud 52 and the angled inboard buffer shroud 53, around the airfoil 25. Thus, when equipped with the angled outboard buffer shroud 52 and the angled inboard buffer shroud 53 as embodied herein, the flow downstream of the airfoil 25 can have a total pressure distribution at the inlet of the diffuser 14 in the turbine engine 10 to reduce loads, stresses, vibrations, and other potentially detrimental operational effects. Due to the airfoil 25 provided with the angled outboard buffer shroud 52 and the angled inboard buffer shroud 53, the total pressure distribution is able to balance the impingement above and below the angled outboard buffer shroud 52 and the angled inboard buffer shroud 53 and smooth the flow therethrough. The balancing of the impingement also enables management of efficiency credits (also known as flow energy) due to the partial span shroud providing smooth flow to the diffuser 14. This smooth flow is uninterrupted to the diffuser 14 and the exhaust system 15, preventing rough flow from degrading operational energy from the turbine engine 10. The partial span shroud configuration is also provided to obtain a balance between turbine and downstream diffuser losses. The circumferential total pressure distribution entering the diffuser is imported into the turbine recovery coefficient. In addition to the blade throat setting, the angle of the dual partial span shroud can be used to configure this distribution. For example, increasing the upper angle can result in a stronger head end profile as more flow is directed to the head end profile, while the lower partial span shroud angle can bias the bottom portion of the blade's pressure distribution. The optimal profile angle of performance balances the impingement losses near the shroud and sets the desired radial pressure distribution in the diffuser over a range of turbine operating conditions.

[0028] As Figure 2As shown, the outboard buffer shroud 52 can be positioned near the outboard tip end 41 of the airfoil 25, while the inboard buffer shroud 53 can be positioned near the radially middle region of the airfoil 25. In alternative embodiments, the outboard buffer shroud 52 is positioned just inside the outboard tip end 41 of the airfoil 25, and the inboard buffer shroud 53 is positioned at approximately the midpoint of the airfoil 25. In another embodiment, the radial positioning of the inboard and outboard buffer shrouds 52 is limited to a range of heights defined relative to the airfoil 25. In one such embodiment, the inboard buffer shroud 53 can be positioned within a radial height range defined between an inboard boundary at 25% of the radial height of the airfoil 25 and an outboard boundary at 75% of the radial height of the airfoil 25, and the outboard buffer shroud 52 can be positioned outside an inboard boundary at 60% of the radial height of the airfoil 25. In alternative embodiments, the inboard buffer shroud 53 can be positioned within a radial height range defined between an inboard boundary at 40% of the radial height of the airfoil 25 and an outboard boundary at 60% of the radial height of the airfoil 25, and the outboard buffer shroud 52 can be positioned within a radial height range defined between an inboard boundary at 75% of the radial height of the airfoil 25 and an outboard boundary at 95% of the radial height of the airfoil 25. In another preferred embodiment, the inboard buffer shroud 53 can be positioned within a radial height range defined between an inboard boundary at 40% of the radial height of the airfoil 25 and an outboard boundary at 60% of the radial height of the airfoil 25, and the outboard buffer shroud 52 can be positioned outside an inboard boundary at 90% of the radial height of the airfoil 25.

[0029] It should be appreciated that in accordance with several of the embodiments discussed above, the present embodiments provide a manner in which the vibrational response of a turbine blade can be reduced in order to limit damaging vibrational mechanical loads, while also allowing for improved aerodynamic / leakage prevention performance. That is, it should be appreciated that in accordance with the present embodiments, the natural frequency of the blade structure can be increased and harmful vibrational responses avoided, thereby enabling longer turbine blades, which in turn can be used to enable larger turbine engines with greater output and efficiency. Additionally, the reduced tip mass and resulting mechanical pull achieved by the present embodiments can allow for tighter clearance between the blade and surrounding stationary structures.

[0030] All means or step plus function elements in the claims that follow on the right-hand side of a “comprising”, “including”, and “having” are intended to mean associated structure, material, or acts for performing functions and not meant to imply that the claimed embodiments necessarily include other inactive elements. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Many modifications and variations will be apparent to practitioners skilled in the art. Embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, and to enable others skilled in the art to understand various embodiments with various modifications as are suited to the particular use contemplated.

Claims

1. A blade (16), comprising: an airfoil (25) including a platform (24), a concave pressure side wall (55), and a convex suction side wall (56) extending axially between respective leading and trailing edges and radially between a root (21) and an outboard tip (41), the blade (16) further comprising: an angled outboard bumper shield (52) positioned on the airfoil (25), the angled outboard bumper shield (52) disposed at an angle a defined by an arc on the angled outboard bumper shield (52) and the platform (24) of the blade (16); an angled inboard bumper shield (53) positioned on the airfoil (25), the angled inboard bumper shield (53) disposed at an angle φ defined by an arc on the angled inboard bumper shield (53) and the platform (24) of the blade (16); wherein the angle a is independently disposed relative to the angle φ, wherein the angle a is not equal to the angle φ.

2. The blade (16) of claim 1, wherein the angle a is greater than the angle φ.

3. The blade (16) of claim 1, wherein the angle a is disposed in a range between about 0 degrees and about 17 degrees.

4. The blade (16) of claim 1, wherein the angle a is about 9 degrees.

5. The blade (16) of claim 1, wherein the angle φ is disposed in a range between about 0 degrees and about 17 degrees.

6. The blade (16) of claim 1, wherein the angle φ is about 7 degrees.

7. The blade (16) of claim 1, wherein the angle a of the angled outboard bumper shield (52) and the angle φ of the angled inboard bumper shield (53) are fixed.

8. The blade (16) of claim 1, wherein the angled inboard bumper shield (53) includes one disposed in a first radial height range defined on the airfoil (25), wherein the first radial height range includes an inboard boundary at 25% of a radial height of the airfoil (25) and an outboard boundary at 75% of the radial height of the airfoil (25); and wherein the angled outboard bumper shield (52) includes one disposed in a second radial height range defined on the airfoil (25), wherein the second radial height range includes an inboard boundary at 60% of the radial height of the airfoil (25).

9. The blade (16) of claim 8, wherein the inboard boundary of the first radial height range includes 40% of the radial height of the airfoil (25) and the outboard boundary of the first radial height range includes 60% of the radial height of the airfoil (25); and wherein the inner boundary of the second radial height range comprises 75% of the radial height of the airfoil (25) and the outer boundary of the second radial height range comprises 95% of the radial height of the airfoil (25).

10. A turbine engine (10) having a turbine (13) including a row of circumferentially spaced apart blades (16), wherein each of the blades (16) includes a platform (24), an airfoil (25) including a concave pressure side wall (55) and a convex suction side wall (56) extending axially between a respective leading edge and a trailing edge and radially between a root (21) and an outer tip (41), the blade (16) further including: an angled outer bumper shroud (52) positioned on the airfoil (25), the angled outer bumper shroud (52) disposed at an angle a defined by an arc on the angled outer bumper shroud (52) and the platform (24) of the blade (16); an angled inner bumper shroud (53) positioned on the airfoil (25), the angled inner bumper shroud (53) disposed at an angle φ defined by an arc on the angled inner bumper shroud (53) and the platform (24) of the blade (16); wherein angle a is independently disposed relative to angle φ, wherein angle a is not equal to angle φ.

11. The turbine engine (10) of claim 10, wherein the angle a is about 9 degrees and the angle φ is about 7 degrees.

12. The turbine engine (10) of claim 10, wherein the angle a of the angled outer bumper shroud (52) and the angle φ of the angled inner bumper shroud (53) are fixed.

13. The turbine engine (10) of claim 10, wherein the angle a is greater than angle φ.

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