Patent Application
20110189022
The invention relates generally to turbo machines such as turbines or compressors, and more particularly, to a turbo machine rotor including a rotor wheel capable of carrying and spacing one or more stages of rotor blades. The rotor wheel is formed using a metal powder as a starting material, and processed using powder metallurgy techniques.
Turbo machines such as turbines and compressors include a rotor, which further includes a rotating shaft with a plurality of axially spaced rotor wheels mounted thereon. Typically, each rotor wheel holds one stage of blades, with the blades mechanically coupled to each rotor wheel and arranged in rows extending circumferentially around each rotor wheel. The axially spaced rotor wheels are typically joined to one another by bolting or welding. These features result in rotors having heavy weights, increased start times, and complex joints. Rotors may also require a spacer rotor wheel to be bolted or welded between each of the plurality of rotor wheels to provide proper spacing between blade stages. Alternatively, rotor wheels have been formed from a single steel monoblock forging, which has limited ranges of operating temperatures and tensile strengths.
A first aspect of the disclosure provides a rotor wheel comprising: a unitary base including a nickel-based superalloy, wherein the unitary base has a shape including: a first disk member for carrying a first stage of rotor blades, and a first spacer member axially extending from a first end face of the first disk member; the first disk member including a plurality of axially spaced, radially outwardly extending slots about an outer circumference of the first disk member for receiving a rotor blade.
A second aspect of the disclosure provides a turbo machine comprising: a rotor including: at least one rotor wheel, each of the at least one rotor wheels including: a unitary base including a nickel-based superalloy, wherein the unitary base has a shape including: a first disk member for carrying a first stage of rotor blades, and a first spacer member axially extending from a first end face of the first disk member; the first disk member including a plurality of axially spaced, radially outwardly extending slots about an outer circumference of the first disk member for receiving a rotor blade; and a plurality of stationary vanes extending circumferentially around the shaft, and positioned axially adjacent to the stage of rotor blades.
A third aspect of the disclosure provides a method comprising: atomizing a nickel-based superalloy to produce a powder; filling a can with the powder and evacuating and sealing the can in a controlled environment; consolidating the can and the powder therein at a temperature, time, and pressure to produce a consolidation; hot working the consolidation to produce a rotor wheel, wherein the rotor wheel includes: a unitary base including a nickel-based superalloy, wherein the unitary base has a shape including: a first disk member for carrying at least one stage of rotor blades, and a first spacer member axially extending from the at least one disk member; and machining a plurality of axially spaced, radially outwardly extending slots into an outer circumference of each of the at least one disk members, each of the plurality of slots being dimensioned to receive a rotor blade.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.
At least one embodiment of the present invention is described below in reference to its application in connection with the operation of a gas or steam turbine. Although embodiments of the invention are illustrated relative to a gas or steam turbine, it is understood that the teachings are equally applicable to other turbo machines including, but not limited to, compressors. Further, at least one embodiment of the present invention is described below in reference to a nominal size and including a set of nominal dimensions. However, it should be apparent to those skilled in the art that the present invention is likewise applicable to any suitable turbo machine. Further, it should be apparent to those skilled in the art that the present invention is likewise applicable to various scales of the nominal size and/or nominal dimensions.
As indicated above, aspects of the invention provide a turbo machine structure.
Referring to the drawings,
Referring to
In various embodiments of the present invention turbine 10 comprises various numbers of stages.
As noted,
In an embodiment, each disk member 36 may have an outer diameter 44 of up to about 3 meters (about 120 inches). The outer diameter 44 is of sufficient thickness to provide the necessary hoop strength to prevent rotor burst. Spacer member 38 may have a second, narrower outer diameter 46 as compared to outer diameter 44 of disk members 36 (
Each disk member 36 includes a plurality of slots 40 machined into an outer circumference of disk member 36 such that slots 40 are axially spaced and radially outwardly extending according to conventional blade 20 attachment techniques. (
As shown in
In various embodiments of the invention, rotor wheel 19 is capable of serving the function of one or more conventional rotor wheels 18 and one or more one conventional spacers 28. In the embodiment depicted in
In the embodiment depicted in
In various embodiments, as depicted in
In the embodiment depicted in
In other embodiments, rotor wheel 19 may carry as many stages of blades 20 as unitary base 34 includes disk members 36, 50, 52, etc. The embodiments depicted in
In various embodiments, unitary base 34 may be made of any of a variety of suitable superalloys, including nickel based super alloys. In some embodiments, the superalloys may be precipitation-strengthened nickel-based superalloys. In various embodiments, the superalloys may have compositions by weight as approximately described in Table 1.
The foregoing superalloy compositions are not intended to be an exhaustive recitation, however, and are merely illustrative of alloy compositions with suitable tensile properties and time dependent crack growth resistance.
The composition of rotor wheel 19 allows turbine 10, and consequently rotor 12 including rotor wheel 19 to operate at much higher temperatures than conventional steel forgings, e.g., at temperatures of up to about 650° C. (about 1200° F.). Rotor wheel 19 further exhibits a tensile yield strength (0.2% yield) of greater than 483 MPa (about 70 ksi) at 538° C. (about 1000° F.). In some embodiments, rotor wheel 19 exhibits a tensile strength (0.2% yield) of about 690 MPa (about 100 ksi) to about 1,069 MPa (about 155 ksi), and further embodiments, about 724 MPa (about 105 ksi) to about 931 MPa (about 135 ksi), allowing for operation at higher speeds.
Further provided is a process for producing rotor wheel 19 using powder metallurgy techniques. The use of powder metallurgy processes to form rotor wheels 19 allows for the formation of more complex geometric shapes, such as depicted in
Under vacuum or in an inert environment, hereinafter referred to as a “controlled environment,” a melt is formed having the chemistry of the desired alloy. While in molten condition and within the desired chemistry specifications, the alloy is converted to powder by atomization or other suitable process to produce approximately spherical powder particles. Because of the large quantity of powder required to produce rotor wheel 19, it may be necessary to blend powders produced from multiple atomization steps. Any powder storage required preferably takes place in a controlled environment.
A can is provided, having a design and material composition that are capable of containing and handling the powder at this stage without distortion. In various embodiments, the can may be made of steel, stainless steel, superalloy, or another suitable material. The can is irregularly shaped substantially in accordance with the desired shape of rotor wheel 19, and includes the geometry necessary to form unitary base 34 including disk members 36 and spacer member 38. In various embodiments, it has an outer diameter of up to about 3 meters (about 120 inches).
The can is filled with the alloy powder in a controlled environment, evacuated to drive off moisture and any volatiles, and sealed while remaining in the controlled environment. The can and the powder are then consolidated at a temperature, time, and pressure sufficient to produce a consolidation. In various embodiments, the consolidation may be accomplished using hot isostatic pressing or any other suitable consolidation method.
The consolidation is then hot worked using any suitable technique to refine the shape of rotor wheel 19. Suitable hot working techniques include, for example, rolled ring forging, extrusion, forging, incremental forging, and die forging, including open die forging, closed die forging, hot die forging, and isothermal forging. The resulting rotor wheel 19 is shaped as described herein. Spacer member 38 may be hollowed out to reduce weight through the can design, a forging process, or machining.
A plurality of slots 40 arranged are then machined in a row into an outer circumference of each of the at least one disk member 36. Each slot 40 is dimensioned to receive a blade 20. Blades 20 are mechanically coupled to rotor wheel 19 via slots 40 using any known technique, such as dovetail attachment. Dovetail connections, including cooperating wheel hooks and bucket hooks, are well known in the art. In various embodiments, rotor wheel 19 may include one, two, three, or more rows of slots 40 machined into as many adjacent disk members 36 to receive one, two, three, or more rows of blades 20, respectively, forming one (
As used herein, the terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals). Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 mm, or, more specifically, about 5 mm to about 20 mm,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 mm to about 25 mm,” etc.).
While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within 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 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.
