Patent Application
20100158678
The present invention relates to a turbine nozzle for a gas turbine. In particular, the invention relates to a third stage turbine nozzle airfoil profile.
In a gas turbine, many system requirements should be met at each stage of a gas turbine's flow path section to meet design goals. These design goals include, but are not limited to, overall improved efficiency and airfoil loading capability. For example, and in no way limiting of the invention, a blade of a compressor stator should achieve thermal and mechanical operating requirements for that particular stage. Further, for example, and in no way limiting of the invention, a turbine nozzle airfoil profile should achieve thermal and mechanical operating requirements for that particular stage. Airfoil points have been patented as demonstrated by Bielek et al. in U.S. Pat. No. 6,503,054 B1 on Jan. 7, 2003. The patent identified from 100-150 points per section with each section having a uniform spacing, a stagger angle vs. radius, a throat angle vs. radius and a camber vs. radius. The number of points defined is dependent upon the rate of change of curvature of the section. In other words, for areas with higher curvature more points are used to define that region.
In accordance with a preferred embodiment of the present invention, there is provided a unique airfoil profile for the nozzles of a turbine stage, for example the third stage of a gas turbine. The nozzle airfoil profile is defined by unique loci of points to achieve the necessary efficiency whereby improved turbine performance is obtained. These unique loci of points define the nominal airfoil profile and are identified by the X, Y and Z Cartesian coordinates of Table 1, which follows. The points for the coordinate values shown in Table 1 are for a cold, in other words, room temperature, profile at various planar cross-sections of the nozzle airfoil along its length. The X and Y coordinates are given in distance dimensions, e.g., units of inches, and are joined smoothly at each Z location to form a smooth continuous airfoil cross-section. The Z coordinates are given in length dimension of inches along a nozzle-stacking axis coincident with a radius from the axis of turbine rotation. Each defined cross-section is then joined smoothly with adjacent cross-sections to form the complete airfoil shape.
It will be appreciated that as each nozzle airfoil 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 and Z coordinates for manufacturing purposes. Since the manufactured nozzle airfoil profile may be different from the nominal airfoil profile given by the following table, a distance of plus or minus 0.100 inches from the nominal profile in a direction normal to any surface location along the nominal defines the profile envelope for this nozzle airfoil. The envelope includes any possible airfoil surface coating process. The design is robust to this variation without impairment of the mechanical and aerodynamic functions.
It will also be appreciated that the airfoil can be scaled up or scaled down geometrically for introduction into similar turbine designs. Consequently, the X, Y, and Z coordinates in inches of the nominal airfoil profile given below are a function of the same constant or number. That is, the X and Y and optionally the Z coordinate values in inches may be multiplied or divided by the same constant or number to provide a scaled up or scaled down version of the nozzle airfoil profile while retaining the airfoil section shape.
In one aspect of the present invention, there is provided a turbine nozzle having an airfoil shape in an envelope within ±0.100 inches in a direction normal to any airfoil surface location wherein the airfoil has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table 1. X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape.
In another aspect of the present invention, there is provided a turbine nozzle having an uncoated nominal airfoil profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table 1. Wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape, the X and Y distances being scalable as a function of the same constant or number to provide a scaled-up or scaled-down nozzle airfoil.
In a further aspect of the present invention, there is provided a turbine comprising a turbine nozzle arrangement having a plurality of nozzles, each of said nozzles having an airfoil shape in an envelope within ±0.100 inches in a direction normal to any airfoil surface location wherein the airfoil has a nominal profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table 1. wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape.
In a further aspect of the present invention, there is provided a turbine comprising a turbine nozzle arrangement having a plurality of nozzles, each of said nozzles having an uncoated nominal airfoil profile substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table 1 wherein X and Y are distances in inches defining the airfoil profile at each distance Z, the profiles at the Z distances being joined smoothly with one another to form a complete airfoil shape, the X and Y distances being scalable as a function of the same constant or number to provide a scaled-up or scaled-down nozzle airfoil. 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.
Referring now to
The exemplary third stage comprises a triplet airfoil nozzle arrangement and a rotor assembly whereby the nozzles are upstream of the buckets. It will be appreciated that a plurality of nozzles are spaced circumferentially, one from the other, about the third stage nozzle arrangement and in this instance there are twenty (20) nozzles mounted on the third stage nozzle arrangement.
Referring now to
Referring now to
A Cartesian coordinate system of X, Y and Z values given in Table 1 define profiles of nozzle airfoils. The coordinate values for the X, Y, and Z coordinates are set forth in inches in Table 1, although other units of dimensions may be used. The Cartesian coordinate system has orthogonally-related X, Y and Z-axes with the Z axis extending perpendicular to a plane normal to a plane containing the X and Y values. The Z distance commences at 0 at the turbine centerline. The Y-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, and the profile of the airfoil 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 of the various surface locations between the distances Z are determined by smoothly connecting the adjacent cross-sections to one another to form the airfoil surface. These values represent the airfoil profiles at ambient, non-operating or non-hot conditions and are for an uncoated airfoil. The sign convention assigns a positive value to Z values and positive and negative values for the X and Y coordinates as typically used in Cartesian coordinate systems.
The Table 1 values are generated and shown to three decimal places for determining the profile of the airfoil. There are typical manufacturing tolerances, which may be accounted for in the airfoil profile. Accordingly, the values for the profile given in Table 1 are for a nominal airfoil. It will therefore be appreciated that ±typical manufacturing tolerances are additive to the X and Y values given in Table 1 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 nozzle airfoil design and turbine.
It will also be appreciated that the airfoil disclosed in Table 1 may be scaled up or down geometrically for use in similar turbine designs. Consequently, the coordinate values set forth in Table 1 may be scaled upwardly or downwardly such that the airfoil section shape remains unchanged. A scaled version of the coordinates in Table I would be represented by X, Y and, optionally, Z coordinate values (after the Z values have been converted to inches) multiplied or divided by the same constant or number.
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment. On the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
