Patent Application
20150345314
The present invention is directed to turbine components and turbine systems. More particularly, the present invention is directed to turbine bucket assemblies and turbine systems having one or more turbine bucket assemblies.
At least some known gas turbine engines include a combustor, a compressor, and/or turbines that include a rotor disk that includes a plurality of rotor blades, or buckets, that extend radially outward therefrom. The plurality of rotating turbine blades or buckets channel high-temperature fluids, such as combustion gases or steam, through either a gas turbine engine or a steam turbine engine. The roots of at least some known buckets are coupled to the disk with dovetails that are inserted within corresponding dovetail slots formed in the rotor disk to form a bladed disk, or “blisk.” Because such turbine engines operate at relatively high temperatures and may be relatively large, the operating capacity of such an engine may be at least partially limited by the materials used in fabricating the buckets and/or the length of the airfoil portions of the buckets. To facilitate enhanced performance, at least some engine manufacturers have increased the size of the engines, thus resulting in an increase in the length of the airfoil portion of the buckets. Such an increase can require the size of the dovetails and the dovetail slots to be increased to ensure the longer buckets are retained in position.
With or without repairable and/or replaceable airfoil tip portions, turbine buckets assemblies are subjected to a variety of forces. Such forces require different portions of the turbine bucket assemblies to have different properties. It is known that variation of density can provide benefit, depending upon the position of the material. However, further characterization of properties providing beneficial results, especially relating to specific materials, would provide additional benefits.
A turbine bucket assembly and turbine system having a turbine bucket assembly with improvements would be desirable in the art.
In an embodiment, a turbine bucket assembly includes a single-lobe joint having an integral platform, the joint having a first axial length; a non-segmented airfoil extending radially outward from the integral platform and having a root region and a tip region integral with the root region, the tip region having a tip end with a second axial length, the second axial length being less than the first axial length; and a turbine wheel having a receptacle with a geometry corresponding to the single-lobe joint and being coupled to the single-lobe joint. The turbine wheel includes a turbine wheel material, and the single-lobe joint and the non-segmented airfoil include a turbine bucket material, the turbine bucket material having a higher heat resistance and a lower thermal expansion than the turbine wheel material.
In another embodiment, a turbine bucket assembly includes a single-lobe joint having an integral platform, the joint having a first axial length; a non-segmented airfoil extending radially outward from the integral platform and having a tip end with a second axial length, the second axial length being less than the first axial length; and a turbine wheel defining a receptacle with a geometry corresponding to the single-lobe joint and being removably coupled to the single-lobe joint. The turbine wheel includes a turbine wheel material and the single-lobe joint and the non-segmented airfoil include a turbine bucket material, the turbine wheel material being a superalloy and the turbine bucket material being a ceramic matrix composite.
In another embodiment, a turbine system includes a compressor section, a combustor section configured to receive air from the compressor section, and a turbine section in fluid communication with the combustor section, the turbine section comprising a stator and a turbine bucket assembly. The turbine bucket assembly includes a single-lobe joint having an integral platform, the joint having a first axial length; a non-segmented airfoil extending radially outward from the integral platform and having a tip end with a second axial length, the second axial length being less than the first axial length; and a turbine wheel defining a receptacle with a geometry corresponding to the single-lobe joint and being coupled to the single-lobe joint. The turbine wheel includes a turbine wheel material and the single-lobe joint and the non-segmented airfoil include a turbine bucket material, the turbine bucket material having a higher heat resistance and a lower thermal expansion than the turbine wheel material.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided is a turbine bucket assembly and a turbine system. In addition, methods of assembling and/or producing such turbine bucket assemblies and turbine systems are apparent from the disclosure. Embodiments of the present disclosure, for example, in comparison to similar concepts failing to include one or more of the features disclosed herein, reduce overall operating and maintenance costs, reduce duration of out-of-service periods for repairs, permit other suitable advantages, permit larger or smaller sized engines and/or turbine buckets to be used, permit a turbine bucket assembly to be exposed to higher temperatures, permit properties in a specific portion of a turbine bucket assembly to be resistant to additional forces, permit use of additional materials for portions of turbine bucket assemblies, or a combination thereof.
During operation, the intake section 12 channels air towards the compressor section 14. The compressor section 14 compresses the inlet air to higher pressures and temperatures and discharges the compressed air towards the combustor section 16. The compressed air is mixed with fuel and ignited to generate combustion gases that flow to the turbine section 18, which drives the compressor section 14 and/or the load 28. Specifically, at least a portion of the compressed air is supplied to fuel nozzle assembly 26. Fuel is channeled to the fuel nozzle assembly 26. The fuel is mixed with the air and ignited downstream of fuel nozzle assembly 26 in the combustor section 16. Combustion gases are generated and channeled to the turbine section 18. Gas stream thermal energy is converted to mechanical rotational energy in the turbine section 18. Exhaust gases exit the turbine section 18 and flow through the exhaust section 20 to the ambient atmosphere.
The joint 108, which couples the bucket 30 to the wheel 105, is a dovetail, is multi-lobed, is single-lobed, is a portion of a blisk, is integral with the airfoil 110 (for example, such that there are no seams or inconsistencies in the turbine bucket 30 where the platform 112 transitions to the airfoil 110), is another suitable mechanism or device for securing the turbine bucket 30, or is a combination thereof. The coefficients of thermal expansion of the materials in the components (for example, a wheel 105 and the airfoil 110) dictate the joint type between the respective components. For instance, when the materials have a nearly identical or identical coefficient of thermal expansion over a wide range of temperatures, the joint 108 between the components is capable of being either a single-lobe or a multi-lobe joint. A multi-lobe joint may be preferred in some circumstances. In contrast, when the materials have dissimilar coefficients of thermal expansion, a single-lobe joint between the components may be preferred.
In one embodiment, the turbine bucket 30 couples to the wheel 105 via the joint 108 and extends radially outward from the wheel 105. The joint 108 has a single-lobe geometry corresponding to a respective receptacle in the wheel 105 and is capable of being removably or permanently coupled to the wheel 105 by any suitable technique. One suitable technique includes the joint 108 being removably coupled to the wheel 105 by an axial joint or a circumferential joint. Another suitable technique includes the joint 108 being removably coupled to the wheel 105 by a dovetail joint, a dado joint, a box joint, a tongue-and-groove joint, or a combination thereof.
In one embodiment, the wheel 105 is a turbine wheel having a plurality of receptacles with geometry corresponding to the single-lobe joints 108 of a corresponding plurality of turbine buckets 30, and the geometry of the wheel 105 defines a rim of the turbine wheel. In an alternate embodiment (
In one embodiment, the joint 108 has an axial joint length 114 that facilitates securing. In one embodiment, the platform 112 extends radially outward from the joint 108 and has a platform length 117 that is equal to or approximately equal to the axial joint length 114 (as shown in
In one embodiment, the airfoil 110 extends radially outward from the joint 108, extends radially outward from an outer platform surface of the platform 112, has an initial airfoil length 119 that is approximately equal to the axial joint length 114, and/or decreases in axial length to a tip end length 118 at a tip end 116 of the turbine bucket 30, such that the tip end length 118 is shorter than the axial joint length 114, when viewed from the right-side profile, as shown in
The airfoil 110 is a non-segmented portion of the turbine bucket 30. In one embodiment, as shown in
The tip region 122 includes a tip region length 126 that is comparable to the turbine bucket length 120, for example, by having a relative ratio to the turbine bucket length 120, such as, about 25 percent, about 40 percent, greater than 40 percent, less than about 50 percent, about 50 percent, greater than about 50 percent, about 60 percent, between about 40 percent and about 60 percent, about 75 percent, between about 25 percent and about 75 percent, between about 40 percent and about 75 percent, or any suitable combination, sub-combination, range, or sub-range therein. The tip region length 126 extends to a mid-region of the airfoil 110 having an axial length 129, which is greater than the tip end length 118 and less than the initial airfoil length 119, when viewed from the right-side profile as shown in
The wheel 105, the joint 108, and/or the airfoil 110 include any suitable combination of materials capable of withstanding the operational demands of the system 10 and/or operating in conjunction with the features of the turbine bucket 30. The materials are similar materials, the same materials, or different materials, which are chosen to achieve a balance between considerations of weight and cost and performance at higher temperatures and/or speeds.
Suitable materials for the joint 108 and the airfoil 110 include, but are not limited to, ceramic matrix composite materials, titanium aluminide, materials having a similar or lower thermal expansion than materials in the wheel 105, materials having similar or higher heat resistance than materials in the wheel 105 (for example, to accommodate the tip region 122 being exposed to higher operating temperatures), materials having a similar or lower density than materials in the wheel 105 (for example, resulting in a lower rotating mass in the turbine bucket 30), or a combination thereof. In the exemplary embodiment described herein, the joint 108 and the airfoil 110 include a ceramic matrix composite material.
As used herein, the term “ceramic matrix composite” includes, but is not limited to, carbon-fiber-reinforced carbon (C/C), carbon-fiber-reinforced silicon carbide (C/SiC), and silicon-carbide-fiber-reinforced silicon carbide (SiC/SiC). In one embodiment, the ceramic matrix composite material has increased elongation, fracture toughness, thermal shock, dynamical load capability, and anisotropic properties as compared to a (non-reinforced) monolithic ceramic structure.
As used herein, the term “titanium aluminide” includes, but is not limited to, typical compositions, by weight, of about 45% Ti and about 50% Al (TiAl) and/or a molar ratio of about 1 mole Ti to about 1 mole Al, TiAl2 (for example, at a molar ratio of about 1 mole Ti to about 2 moles Al), TiAl3 (for example, at a molar ratio of about 1 mole Ti to about 3 moles Al), Ti3Al (for example, at a molar ratio of about 3 moles Ti to about 1 mole Al), or other suitable mixtures thereof.
Suitable materials for the wheel 105 include, but are not limited to, cobalt-based superalloys, nickel-based superalloys, steel-based superalloys, materials having a similar or higher thermal expansion than materials in the airfoil 110, materials having similar or lower heat resistance than materials in the airfoil 110, materials having a similar or higher density than materials in the airfoil 110, or a combination thereof.
As used herein, the term “superalloy” includes, but is not limited to, nickel-based alloys, cobalt-based alloys, or steel-based alloys. One typical nickel-based superalloy material, which is sold under the tradename INCONEL® 718 by Special Metal Corporation of New Hartford, N.Y., has a composition, by weight, of about 50.0-55.0% Ni, about 17.0-21.0% Cr, about 4.75-5% Nb, about 2.8-3.3% Mo, about 1.0% Co, about 0.65-1.15% Al, about 0.35% Mn, about 0.35% Si, about 0.2-0.8% Cu, about 0.3% Ti, about 0.08% C, about 0.015% S, about 0.015% P, and about 0.006% B, and a balance of Fe. An exemplary CrMoV (steel-based) superalloy composition has a composition, by weight %, of about 0.90-1.50% Mo, about 0.90-1.25% Cr, about 0.55-0.90% Mn, about 0.35-0.55% Ni, about 0.25-0.33% C, 0.20-0.30% V, no more than about 0.35% Si, no more than about 0.35% Cu, no more than 0.012% P, no more than about 0.012% S, and the balance Fe and trace impurities.
Referring again to
The impact strips 107 are attached by one or more chemical and/or mechanical techniques, for example, based upon physics-based methods (such as geometry) and material science methods (such as through various fabrication steps). In one embodiment, the impact strips 107 are chemically attached, for example, via in-situ material processing, such as cast-in, in-situ extrusion, in-situ forging, other suitable techniques, or a combination thereof. Additionally or alternatively, in one embodiment, the impact strips 107 are chemically attached via post-material initial processing, such as diffusion bonding, alloy brazing, additive manufacturing, other suitable techniques, or a combination thereof. In another embodiment, the impact strips 107 are mechanically attached via glue, rivets, stem pins, buttons, or retention joints (for example, a dado joint, a box joint, and/or a tongue-and-groove joint), other suitable techniques, or a combination thereof.
While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In addition, all numerical values identified in the detailed description shall be interpreted as though the precise and approximate values are both expressly identified.
