First-stage high pressure turbine bucket airfoil

[0003] The present invention relates to a turbine bucket for a gas turbine stage and particularly relates to a first-stage turbine bucket airfoil profile.

[0004] In recent years, advanced gas turbines have trended toward increasing firing temperatures and efforts to improve cooling of the various turbine components. In a particular gas turbine design developed by General Electric Company, a high output turbine that uses a combination of steam and air cooling to meet a 60% combined cycle efficiency is undergoing development. It will be appreciated that the design and construction of the turbine buckets and particularly the buckets of the first turbine stage of that turbine require optimized aerodynamic efficiency, as well as aerodynamic and mechanical bucket loading. Additionally, the interaction between the stages of the turbine is a factor in determining the overall turbine efficiency.

[0005] General Electric Company has developed an optimal first-stage turbine bucket airfoil profile to achieve a 60% combined cycle efficiency in producing 50Hz electrical power in what has become known as the MS9001 turbine system. See, for example, U.S. Pat. No. 6,461,110. Efforts have been made to achieve a 60% cycle combined cycle efficiency in generating 60 Hz electrical power. Meeting system requirements of efficiency and loading in such a first stage turbine bucket in a high output (400MW) turbine producing 60 Hz electrical power, such as the MS7001H turbine developed by General Electric Company, has become a challenge. An airfoil profile that meets the efficiency and stage loading goals of the turbine while avoiding undesirable and even potentially unsafe vibration leading to blade fatigue failure has yet to be achieved.

[0006] In one aspect, there is provided a turbine bucket having a bucket airfoil in an envelope within ±0.100 inches in a direction normal to any bucket surface location wherein the bucket airfoil has an uncoated nominal profile substantially in accordance with Cartesian coordinates values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a perpendicular distance from a plane normal to a radius emanating from the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section and X and Y are coordinates defining the profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form the complete bucket airfoil shape.

[0007] In another aspect, there is provided a turbine bucket having a bucket airfoil shape in an envelope within ±0.100 inches in a direction normal to any airfoil surface location wherein the airfoil has an uncoated nominal profile substantially in accordance with Cartesian coordinates values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a perpendicular distance from a plane normal to a radius emanating from the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form the complete airfoil shape.

[0008] In another aspect, there is provided a turbine bucket having an uncoated nominal airfoil profile substantially in accordance with Cartesian coordinates values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a perpendicular distance from a plane normal to a radius emanating from the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form the complete airfoil bucket shape, the X, Y and Z values being scaled as a function of the same constant or number to provide a scaled-up or scaled-down bucket airfoil.

[0009] In another aspect, there is provided a turbine comprising a turbine wheel having a plurality of buckets, each of said buckets having an airfoil shape in an envelope within ±0.100 inches in a direction normal to any bucket airfoil surface location wherein the airfoil has an uncoated nominal profile substantially in accordance with Cartesian coordinates values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a perpendicular distance from a plane normal to a radius emanating from the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form the complete airfoil shape.

[0010] In a another aspect, there is provided a turbine comprising a turbine wheel having a plurality of buckets, each of said buckets having an uncoated nominal airfoil profile substantially in accordance with Cartesian coordinates values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a perpendicular distance from a plane normal to a radius emanating from the turbine centerline and containing the X and Y values with the Z value commencing at zero in the X, Y plane at the radially innermost aerodynamic section of the airfoil and X and Y are coordinates defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form the complete airfoil shape, the X, Y and Z values being scaled as a function of the same constant or number to provide a scaled-up or scaled-down bucket.

[0011] FIG. 1 is a side elevational view of a turbine bucket including an airfoil, shank and dovetail constructed in accordance with the present invention.

[0012] FIG. 2 is a perspective view thereof.

[0013] FIG. 3 is an enlarged end view of the bucket as viewed radially inwardly.

[0014] FIG. 4 is a perspective view of the bucket.

[0015] FIG. 5 is an axial view of the bucket.

[0016] FIG. 6 is an enlarged view of the bucket illustrated in FIG. 5.

[0017] FIG. 7 is a schematic illustration of the airfoil profile of the bucket.

[0018] FIG. 8 is a schematic illustration of a turbine having a first-stage turbine wheel employing the buckets hereof.

[0019] Referring now to the drawing figures, particularly to FIGS. 1 and 2, there is illustrated a turbine blade particularly suited to meet system requirements of efficiency and loading in an H-series turbine, such as the MS7001H turbine developed by General Electric Company and producing 60 Hz electrical power. It is appreciated, however, that the turbine blade described below may be advantageous in other turbine applications. The description herein is therefore set forth for illustrative purposes only and is not intended to limit application of the invention to a particular turbine, H-series or otherwise.

[0020] In an exemplary embodiment, the turbine blade is includes an airfoil 10 mounted on a platform 12 carried by a shank 14. A radially inner end of the shank 14 carries a dovetail 16 for coupling the blade to a turbine wheel (not shown in FIG. 1). The airfoil 10, platform 12 and dovetail 16 are collectively referred to as a bucket, generally designated 17. The airfoil 10 has a compound curvature with suction and pressure sides 18 and 20, respectively. As conventional, it will be appreciated that the dovetail 16 mates in dovetail openings in a turbine wheel and that a plurality of buckets, preferably sixty buckets, are circumferentially spaced one from the other about the wheel and turbine rotor axis. Additionally, there are wheelspace seals 22, i.e., angel wings, formed on the axially forward and aft sides of shank 14. Preferably, the bucket is integrally cast with cooling, preferably steam-cooling, passages (not shown) internal to the bucket including airfoil 10.

[0021] Via development of source codes, models and design practices, a unique turbine bucket airfoil profile for a turbine stage, preferably the first stage, has been determined. The airfoil profile may be defined by a unique loci of points to achieve the necessary efficiency in loading requirements whereby improved turbine performance is obtained. Specifically, a loci of 1660 points in space that meet the unique demands of the first stage requirements of an H turbine in a 60 Hz power generation system, such as the aforementioned MS7001H turbine, has been determined in an iterative process considering aerodynamic loading and mechanical loading of the blades under applicable operating parameters. The loci of points is believed to achieve a desired interaction between other stages in the high pressure turbine, aerodynamic efficiency of the turbine; and optimal aerodynamic and mechanical loading of the turbine blades in operation. Additionally, the loci of points provides a manufacturable airfoil profile for fabrication of the turbine blades, and allows the MS7001H turbine, for example, to run in an efficient, safe and predictable manner.

[0022] Referring now to FIG. 2, there is shown a Cartesian coordinate system for X, Y and Z values set forth in Table I which follows. The Cartesian coordinate system has orthogonally-related X, Y and Z axes with the Z axis extending perpendicular to a plane normal to a radius emanating from the centerline of the turbine rotor, i.e., normal to a plane containing the X and Y values. The Z distance commences at zero in the X, Y plane at the radially innermost aerodynamic section. The Z axis lies parallel to the turbine rotor centerline, i.e., the rotary axis. By defining X and Y coordinate values at selected locations in a Z direction normal to the X, Y plane, the profile of airfoil 10 can be ascertained. By connecting the X and Y values with smooth, continuing arcs, each profile section at each distance Z is fixed. The surface profiles at the various surface locations between the distances Z are connected smoothly to one another to form the airfoil. Distances Z in Table 1 are provided as non-dimensionalized values, and tabular values for X and Y given in Table I below are in inches for several cross-sections of the bucket. The tabular values represent airfoil profiles at ambient (i.e., room-temperature), non-operating or non-hot conditions and are for an uncoated airfoil. It will also be appreciated that as the bucket heats up in use, the profile will change as a result of stress and temperature. Thus, the cold or room-temperature profile is given by the X, Y, Z coordinates for manufacturing purposes. The sign convention assigns positive and negative values for the X and Y coordinates, as typically used in a Cartesian coordinate system.

[0023] While the Table I values are generated and shown to four decimal places, in view of manufacturing constraints, actual values useful for forming the airfoil are considered valid to three decimal places for determining the profiles of the airfoil. Further, there are typical manufacturing tolerances as well as coatings which must be accounted for in the actual profile of the airfoil. Accordingly, the values for the profile given in Table I are for a nominal airfoil. It will therefore be appreciated that ± typical manufacturing tolerances, i.e., plus or minus values and cooling thicknesses, are additive to the X and Y values given in Table I below. Accordingly, a distance of ±0.100 inches in a direction normal to any surface location along the airfoil profile defines an airfoil profile envelope for this particular bucket design and turbine.

[0024] The coordinate values given in Table I below provide the preferred nominal profile envelope.

[0025] It will also be appreciated that the airfoil disclosed in the above Table may be scaled up or down geometrically for use in other similar turbine designs. Consequently, the coordinate values set forth in Table I may be scaled upwardly or downwardly by the same constant or number such that the airfoil section shape remains unchanged. A scaled version of the coordinates in Table I would be represented by X, Y and Z coordinate values multiplied or divided by the same constant or number to provide a scaled-up or scaled-down version of the bucket airfoil profile, while retaining the airfoil section shape.

[0026] Referring now to FIG. 8, there is illustrated a turbine in which the turbine bucket having the airfoil defined herein may be utilized. In the illustrated turbine, the turbine rotor, designated 40, includes rotor wheels 42 mounting buckets which, in conjunction with stator vanes, form the various stages of the rotor. Particularly, the first stage 46 comprises a first-stage rotor wheel 44 on which the buckets 17 having airfoils 10 hereof are mounted in opposition to first-stage stator vanes 48. It will be appreciated that a plurality of the airfoils 10 are spaced circumferentially one from the other about the first-stage wheel 44 and, in this instance, there are sixty buckets mounted on the first-stage wheel 44. The turbine drives a generator (not shown) for producing 60 Hz electrical power.

[0027] The airfoil profile of the present invention, as described above, is believed to be optimal in the first stage of the gas turbine to achieve desired interaction between other stages in the turbine, improve aerodynamic efficiency of the turbine; and optimize aerodynamic and mechanical loading of the turbine blades in operation.

[0028] While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.