Patent Grant
7384243
The present invention relates generally to stator vanes for gas turbines and, more particularly, to a novel and improved profile for a ninth stage compressor stator vane.
In the design, fabrication and use of turbine engines, there has been an increasing tendency toward operating with higher temperatures and higher operating pressures to optimize turbine performance. Also, as existing turbine airfoils and stator vanes reach the end of their life cycle, it is desirable to replace the airfoils, while simultaneously enhancing performance of the gas turbine through redesign of the airfoils to accommodate the increased operating temperatures and pressures.
Airfoil profiles for gas turbines have been proposed to provide improved performance, lower operating temperatures, increased creep margin and extended life in relation to conventional airfoils. See, for example, U.S. Pat. No. 5,980,209 describing an enhanced turbine blade airfoil profile. Advanced materials and new steam cooling systems now permit gas turbines to operate at, and accommodate, much higher operating temperatures, mechanical loading, and pressures than is capable in at least some known turbine engines. As a result, many system requirements must be met for each stage of each compressor used with the turbine engines in order to meet design goals including overall improved efficiency and airfoil loading. Particularly, the airfoils of the stator vanes positioned within the compressors must meet the thermal and mechanical operating requirements for each particular stage.
In one aspect, an airfoil for a stator vane is provided. The airfoil has an uncoated profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I carried only to four decimal places wherein Z is a distance from a platform on which the airfoil is mounted and X and Y are coordinates defining the profile at each distance Z from the platform.
In another aspect, a compressor comprising at least one row of stator vanes is provided. Each of the stator vanes comprises a base and an airfoil extending therefrom. At least one of the airfoils has an airfoil shape. The airfoil shape has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a distance from a platform on which the airfoil is mounted and X and Y are coordinates defining the profile at each distance Z from the platform.
In a further aspect, a stator assembly is provided. The stator assembly includes at least one stator vane including a base and an airfoil extending from the base. The airfoil has an uncoated profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I carried only to three decimal places wherein Z is a distance from a platform on which the airfoil is mounted and X and Y are coordinates defining the profile at each distance Z from the base. The profile is scalable by a predetermined constant n and manufacturable to a predetermined manufacturing tolerance.
In operation, air flows through compressor 12 and compressed air is supplied to combustor 20. Combustion gases 28 from combustor 20 propels turbines 14. Turbine 14 rotates shaft 18, compressor 12, and electric generator 16 about a longitudinal axis 30.
The airfoil profile of the present invention, as described below, is believed to be optimal in the ninth stage of compressor 12 to achieve desired interaction between other stages in compressor 12, improve aerodynamic efficiency of compressor 12; and optimize aerodynamic and mechanical loading of each stator vane during compressor operation.
When assembled within the rotor assembly, each stator vane 40 is coupled to an engine casing (not shown) that extends circumferentially around a rotor shaft, such as shaft 18 (shown in
Each airfoil 60 includes a first sidewall 70 and a second sidewall 72. First sidewall 70 is convex and defines a suction side of airfoil 60, and second sidewall 72 is concave and defines a pressure side of airfoil 60. Sidewalls 70 and 72 are joined together at a leading edge 74 and at an axially-spaced trailing edge 76 of airfoil 60. More specifically, airfoil trailing edge 76 is spaced chord-wise and downstream from airfoil leading edge 74. First and second sidewalls 70 and 72, respectively, extend longitudinally or radially outward in span from a root 78 positioned adjacent base 62 to an airfoil tip 80.
Base 62 facilitates securing stator vanes 40 to the casing. In the exemplary embodiment, base 62 is known as a “square-faced” base and includes a pair of circumferentially-spaced sides 90 and 91 that are connected together by an upstream face 92 and a downstream face 94. In the exemplary embodiment, sides 90 and 91 are identical and are substantially parallel to each other. Moreover, in the exemplary embodiment, upstream face 92 and downstream face 94 are substantially parallel to each other.
A pair of integrally-formed hangers 100 and 102 extend from each respective face 92 and 94. Hangers 100 and 102, as is known in the art, engage the casing to facilitate securing stator vane 40 within the rotor assembly. In the exemplary embodiment, each hanger 100 and 102 extends outwardly from each respective face 92 and 94 adjacent a radially outer surface 104 of base 62.
In the exemplary embodiment, the airfoils 60 are integrally cast with each base 62 from a directionally solidified alloy which is strengthened through solution and precipitation hardening heat treatments. The directional solidification affords the advantage of avoiding transverse grain boundaries, thereby increasing creep life.
Via development of source codes, models and design practices, a loci of 1456 points in space that meet the unique demands of the ninth stage requirements of compressor 12 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 compressor, aerodynamic efficiency of the compressor; and optimal aerodynamic and mechanical loading of the stator vanes during compressor operation. Additionally, the loci of points provide a manufacturable airfoil profile for fabrication of the stator vanes, and allows the compressor to run in an efficient, safe and smooth manner.
Referring to
The X and Y coordinates for determining the airfoil section profile at each radial location or airfoil height Z are tabulated in the following Table I, where Z is a non-dimensionalized value equal to 0 at the upper surface of the platform 62 and equal to 1.593 at airfoil tip portion 80. Tabular values for X, Y, and Z coordinates are provided in inches, and represent actual airfoil profiles at ambient, non-operating or non-hot conditions for an uncoated airfoil, the coatings for which are described below. Additionally, the sign convention assigns a positive value to the value Z and positive and negative values for the coordinates X and Y, as typically used in a Cartesian coordinate system.
The Table I values are computer-generated and shown to three decimal places. However, in view of manufacturing constraints, actual values useful for forming the airfoil are considered valid to only three decimal places for determining the profile of the airfoil. Further, there are typical manufacturing tolerances which must be accounted for in the 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 plus or minus typical manufacturing tolerances are applicable to these X, Y and Z values and that an airfoil having a profile substantially in accordance with those values includes such tolerances. For example, a manufacturing tolerance of about ±0.160 inches is within design limits for the airfoil. Thus, the mechanical and aerodynamic function of the airfoils is not impaired by manufacturing imperfections and tolerances, which in different embodiments may be greater or lesser than the values set forth above. As appreciated by those in the art, manufacturing tolerances may be determined to achieve a desired mean and standard deviation of manufactured airfoils in relation to the ideal airfoil profile points set forth in Table 1.
In addition, and as noted previously, the airfoil may also be coated for protection against corrosion and oxidation after the airfoil is manufactured, according to the values of Table I and within the tolerances explained above. In an exemplary embodiment, an anti-corrosion coating or coatings is provided with a total average thickness of about 0.100 inches. Consequently, in addition to the manufacturing tolerances for the X and Y values set forth in Table I, there is also an addition to those values to account for the coating thicknesses. It is contemplated that greater or lesser coating thickness values may be employed in alternative embodiments of the invention.
As the ninth stage stator vane assembly, including the aforementioned airfoils, heats up during operation, applied stress and temperature on the turbine blades inevitably leads to some deformation of the airfoil shape, and hence there is some change or displacement in the X, Y and Z coordinates set forth in Table 1 as the engine is operated. While it is not possible to measure the changes in the airfoil coordinates in operation, it has been determined that the loci of points set forth in Table 1 plus the deformation in use, allows the compressor to run in an efficient, safe and smooth manner.
It is appreciated that the airfoil profile set forth in Table 1 may be scaled up or down geometrically in order to be introduced into other similar machine designs. It is therefore contemplated that a scaled version of the airfoil profile set fort in Table 1 may be obtained by multiplying or dividing each of the X and Y coordinate values by a predetermined constant n. It is recognized that Table 1 could be considered a scaled profile with n set equal to 1, and greater or lesser dimensioned airfoils could be obtained by adjusting n to values greater and lesser than 1, respectively.
The above-described stator vanes provide a cost-effective and reliable method for optimizing performance of a rotor assembly. More specifically, each stator vane airfoil has an airfoil shape that facilitates achieving a desired interaction between other stages in the compressor, aerodynamic efficiency of the compressor; and optimal aerodynamic and mechanical loading of the stator vanes during compressor operation. As a result, the redefined airfoil geometry facilitates extending a useful life of the stator assembly and improving the operating efficiency of the compressor in a cost-effective and reliable manner.
Exemplary embodiments of stator vanes and stator assemblies are described above in detail. The stator vanes are not limited to the specific embodiments described herein, but rather, components of each stator vane may be utilized independently and separately from other components described herein. For example, each stator vane recessed portion can also be defined in, or used in combination with, other stator vanes or with other rotor assemblies, and is not limited to practice with only stator vane 40 as described herein. Rather, the present invention can be implemented and utilized in connection with many other vane and rotor configurations.
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.
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.
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| Number | Date | Country | |
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| 20070048143 A1 | Mar 2007 | US |
