The present invention relates to the art of gas turbines and, more particularly, to an airfoil core shape for a turbine nozzle for a gas turbine.
Many system requirements must be met for each stage of a hot gas path section of a gas turbine in order to meet design goals including an overall improvement in efficiency and airfoil loading. In particular, a stage-one nozzle must meet system requirements including cooling flow and part life. The stage-one nozzle also has a particular set of boundary conditions based on operating conditions of the gas turbine. The nozzle core shape must meet design specifications and also be capable of efficient manufacture.
In accordance with one exemplary embodiment of the invention, an article of manufacture includes an object having an airfoil core shape. The airfoil core shape has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z set forth in TABLE 1 where X and Y are distances in inches which, when connected by smooth continuing arcs, define airfoil profile sections at each distance Z in inches. The profile sections at the Z distances are joined smoothly with one another to form a complete airfoil core shape.
In accordance with another exemplary embodiment of the invention, a turbine includes at least one turbine stage including a plurality of articles of manufacture. Each of the plurality of articles of manufacture includes an airfoil core shape. The airfoil core shape has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z set forth in TABLE 1 where X and Y are distances in inches which, when connected by smooth continuing arcs, define airfoil profile sections at each distance Z in inches. The profile sections at the Z distances are joined smoothly with one another to form a complete airfoil core shape.
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An important aspect of the nozzle is a cold airfoil core profile shape, which in accordance with an exemplary embodiment of the invention, was configured for enhanced turbine performance. A list of X, Y, and Z coordinates for airfoil core 40 is presented in TABLE I, and meets turbine requirements for cooling flow, nozzle casting producibility and impingement tube insertability. Moreover, by maximizing an impingement cooling area, the particular shape of airfoil core 40 substantially eliminates the need for airfoil film cooling introduced downstream of the nozzle throat to still further enhance performance. The points are arrived at by iteration between aerodynamic and mechanical design improvements and are the only loci of points that allow gas turbine 10 to operate in an efficient, smooth manner. As will become more fully evident below, airfoil core 40 is represented as a set of 1440 points listed in TABLE 1. The 1440 points represent 12 sections of airfoil core 40 each containing 120 points. The X, Y, and Z coordinates, which represent a profile of airfoil core 40, are created in a coordinate system which is defined relative to a cold engine centerline axis (not separately labeled) of turbine engine 10. The origin of the coordinate system on the cold centerline axis is X=0.0, Y=0.0 and Z=0.0. The Z coordinate axis is defined as a radial line from the Y coordinate axis; the X coordinate axis is defined as being normal to a plane defined by the Y-Z axis. Airfoil sections are cut normal to the Z coordinate axis. X and Y points, which make up the airfoil core profile shape at each section, are in inches. The radial Z values in inches for the section planes start at bottom section or a point Z0, closest to the cold centerline axis, to Z1, a top section or a point farthest from the cold centerline axis.
The radial distance between each section is 0.6 inches such that a total radial distance of air foil core 40 is 6.6 inches. The bottom and top sections Z0 and Z1, may be obscured by cast-in features that are not included in the X, Y, and Z points that define airfoil core 40. All of the 1440 points are taken from a nominal cold or room temperature for each cross section of airfoil core 40. Each section is joined smoothly with adjacent sections to form the airfoil core profile shape.
It should be appreciated that as each nozzle 16 heats up during operation of turbine engine 10, the airfoil core profile shape will change as a result of stress and temperature. Thus, the X, Y and Z points are provided at cold or room temperature for manufacturing purposes. Since the manufactured airfoil core profile shape may be different from a nominal airfoil core profile shape defined in Table 1, a tolerance of ±0.060 inches from the nominal profile is allowed and thus defines an overall design envelope for the airfoil core profile shape. The overall design is robust to this design envelope without impairment of mechanical or aerodynamic properties of nozzle 16.
It should also be appreciated that the airfoil core 40 can be scaled up or scaled down geometrically for introductions into similar turbine designs, with smaller or larger frame size. Consequently, the X, Y, and Z coordinates in inches may be multiplied or divided by the same constant or number/factor to provide a scaled up or scaled down version of nozzle 16 while retaining the airfoil core profile shape and unique properties.
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In no way limiting of the invention, airfoil core 40 provides an increased efficiency as much as 0.08% compared to previous individual airfoil cores. Moreover, and in no way limiting of the invention, in conjunction with other airfoil cores, which are conventional or enhanced (similar to the enhancements herein), airfoil core 40, as embodied by the invention, provides an increased efficiency as much as 0.08% compared to previous individual sets of airfoil cores. This increased efficiency provides, in addition to the above-noted advantages, a power output with a decrease the required fuel, therefore inherently decreasing emissions to produce energy. Of course, other such advantages are within the scope of the invention.
At this point it should be understood that the points disclosed in Table 1 are exemplary, variations/deviations from the points in Table 1 at one or more sections that do not substantially affect the desired properties obtained by the airfoil core shape of the invention exemplary embodiments fall within the scope of the exemplary embodiments of the invention.
In general, this written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of exemplary embodiments of the present invention if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
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Number | Date | Country | |
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20090324415 A1 | Dec 2009 | US |