Patent Grant
7611326
The invention relates generally to a vane airfoil for a gas turbine engine and, more particularly, to an airfoil profile suited for use in the first stage vane assembly of a two-stage high pressure turbine.
Every stage of a gas turbine engine must meet a plurality of design criteria to assure the best possible overall engine efficiency. The design goals dictate specific thermal and mechanical requirements that must be met pertaining to heat loading, parts life and manufacturing, use of combustion gases, throat area, vectoring, the interaction between stages to name a few. The design criteria for each stage is constantly being re-evaluated and improved upon. Each airfoil is subject to flow regimes which lend themselves easily to flow separation, which tend to limit the amount of work transferred to the compressor, and hence the total thrust or power capability of the engine. The high pressure turbine is also subject to harsh temperatures and pressures, which require a solid balance between aerodynamic and structural optimization. Therefore, improvements in airfoil design are sought.
It is an object of this invention to provide an improved vane airfoil suited for use in a two-stage high pressure turbine vane assembly.
The present invention provides a vane trailing edge, pressure surface cutback, optimized for aerodynamic performances while ensuring a cooling scheme could be fit within the airfoil. The design also minimizes static pressure gradients in the spanwise direction, to minimize secondary losses and to beneficially align the flow entering the downstream high pressure turbine blade stage. The radial distribution of the airfoil sectional throats is optimized for optimum work on the downstream high pressure turbine blades.
In one aspect, the present invention provides a turbine vane for a gas turbine engine comprising an airfoil having an intermediate portion defined by a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z of Sections 5 to 10 set forth in Table 2, wherein the point of origin of the orthogonally related axes X, Y and Z is located at an intersection of a centerline of the gas turbine engine and a stacking line of the turbine vane, the Z values are radial distances measured along the stacking line, the X and Y are coordinate values defining the profile at each distance Z
In another aspect, the present invention provides a turbine vane for a gas turbine engine, the turbine vane having an uncoated intermediate airfoil portion defined by a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z of Sections 5 to 10 set forth in Table 2, wherein the point of origin of the orthogonally related axes X, Y and Z is located at an intersection of a centerline of the gas turbine engine and a stacking line of the turbine vane, the Z values are radial distances measured along the stacking line, the X and Y are coordinate values defining the profile at each distance Z, and wherein the X and Y values are scalable as a function of the same constant or number.
In another aspect, the present invention provides a turbine stator assembly for a gas turbine engine comprising a plurality of vanes, each vanes including an airfoil having an intermediate portion defined by a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z of Sections 5 to 10 set forth in Table 2, wherein the point of origin of the orthogonally related axes X, Y and Z is located at an intersection of a centerline of the gas turbine engine and a stacking line of the turbine vane, the Z values are radial distances measured along the stacking line, the X and Y are coordinate values defining the profile at each distance Z.
In a still further aspect of the present invention, there is provided a high pressure turbine vane comprising at least one airfoil having a surface lying substantially on the points of Table 2, the airfoil extending between platforms defined generally by Table 1, wherein a fillet radius is applied around the airfoil between the airfoil and platforms, and wherein the values of Table 2 are subject to the relevant tolerance.
Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below.
Reference is now made to the accompanying figures depicting aspects of the present invention, in which:
The gas turbine engine 10 further includes a turbine exhaust duct 20 which is exemplified as including an annular core portion 22 and an annular outer portion 24 and a plurality of struts 26 circumferentially spaced apart, and radially extending between the inner and outer portions 22, 24.
The turbine section 18 has two high pressure turbine (HPT) stages located in the gaspath 27 downstream of the combustor 16. Referring to
More specifically, the stator assemblies 32, 34 each include the plurality of circumferentially distributed vanes 40a and 40b respectively which extend radially across the hot gaspath 27. The first HPT stator assembly 32 comprises 32 vanes 40a that are uniformly circumferentially distributed. The vane assembly is preferably made of 8 segments of 4 airfoils each.
The novel airfoil shape of each first stage HPT vane 40a is defined by a set of X-Y-Z points in space. This set of points represents a novel and unique solution to the target design criteria discussed above, and are well-adapted for use in a two-stage high pressure turbine design. The set of points are defined in a Cartesian coordinate system which has mutually orthogonal X, Y and Z axes. The X axis extends axially along the turbine rotor centerline 29, i.e., the rotary axis. The positive X direction is axially towards the aft of the turbine engine 10. The Z axis extends along the HPT vane stacking line 44 of each respective vane 40a in a generally radial direction and intersects the X axis. The positive Z direction is radially outwardly toward the outer vane platform 62. The Y axis extends tangentially with the positive Y direction being in the direction of rotation of the rotor assembly 36. Therefore, the origin of the X, Y and Z axes is defined at the point of intersection of all three orthogonally-related axes: that is the point (0,0,0) at the intersection of the center of rotation of the turbine engine 10 and the stacking line 44.
In a particular embodiment of the first stage HPT vane, the set of points which define the vane airfoil profile relative to the axis of rotation of the turbine engine 10 and stacking line 44 thereof are set out in Table 2 below as X, Y and Z Cartesian coordinate values. Particularly, the vane airfoil profile is defined by profile sections 66 at various locations along its height, the locations represented by Z values. It should be understood that the Z values do not represent an actual radial height along the airfoil 54 but are defined with respect to the engine center line. For example, if the vanes 40a are mounted about the stator assembly 32 at an angle with respect to the radial direction, then the Z values are not a true representation of the height of the airfoils of the vanes 40a. Furthermore, it is to be appreciated that, with respect to Table 2, Z values are not actually radial heights, per se, from the centerline but rather a height from a plane through the centerline—i.e. the sections in Table 2 are planar. The coordinate values are set forth in inches in Table 2 although other units of dimensions may be used when the values are appropriately converted.
Thus, at each Z distance, the X and Y coordinate values of the desired profile section 66 are defined at selected locations in a Z direction normal to the X, Y plane. The X and Y coordinates are given in distance dimensions, e.g., units of inches, and are joined smoothly, using appropriate curve-fitting techniques, at each Z location to form a smooth continuous airfoil cross-section. The vane airfoil profiles of the various surface locations between the distances Z are determined by smoothly connecting the adjacent profile sections 66 to one another to form the airfoil profile.
The coordinate values listed in Table 2 below represent the desired airfoil profiles in a “cold” (i.e. non-operating) condition. However, the manufactured airfoil surface profile will be slightly different, as a result of manufacturing and applied coating tolerances. The coordinate values listed in Table 2 below are for an uncoated airfoil. According to an embodiment of the present invention, the finished HPT vane is coated with a thermal protecting layer.
The Table 2 values are generated and shown to three decimal places for determining the profile of the HPT stage vane airfoil. However, as mentioned above, there are manufacturing tolerance issues to be addressed and, accordingly, the values for the profile given in Table 2 are for a theoretical airfoil. A profile tolerance of ±0.003 inches, measured perpendicularly to the airfoil surface is additive to the nominal values given in Table 2 below. The coating typically applied on the vanes defined in Table 2 is about 0.0010 inch to 0.002 inch thick (preferably between 0.0015 and 0.002 inch) beyond the original dimensions. Some of the coating may also get “diffused” into the metal, about 0,002 inch into it. The total coating thickness then is about 0.0035 inch. A ceramic coating could also be applied in addition to the existing coating, thereby adding 0.002 to 0.01 inch to the existing metallic coating. The first stage HPT vane airfoil design functions well within these ranges of variation. The cold or room temperature profile is given by the X, Y and Z coordinates for manufacturing purposes. It is understood that the airfoil may deform, within acceptable limits, once entering service.
The coordinate values given in Table 2 below provide the preferred nominal first stage HPT vane airfoil profile.
It should be understood that the finished first stage HPT vane 40a does not necessarily include all the sections defined in Table 2. The portion of the airfoil 54 proximal to the platforms 60 and 62 may not be defined by a profile section 66. It should be considered that the vane 40a airfoil profile proximal to the platforms 60 and 62 may vary due to several imposed constraints. However, the HPT vane 40a has an intermediate airfoil portion 64 defined between the inner and outer vane platforms 60 and 62 thereof and which has a profile defined on the basis of at least the intermediate Sections of the various vane profile sections 66 defined in Table 2.
It should be appreciated that the intermediate airfoil portion 64 of the HPT stage vane 40 is defined between the inner and outer gaspath walls 28 and 30 which are partially defined by the inner and outer vane platforms 60 and 62. More specifically, the Z values defining the gaspath 27 in the region of the stacking line 44 fall within the range of Z=5.975 and Z=6.922 which are the z values at the stacking line 44 (see Table 1). Therefore, the airfoil profile physically appearing on HPT vane 40a includes Sections 5 to 10 of Table 2. Sections 11 is only partially located in the gaspath 27. Sections 1 to 4, 12 and 13 are located outside of the gaspath 27, but are provided, in part, to fully define the airfoil surface and, in part, to improve curve-fitting of the airfoil at its radially distal portions. The skilled reader will appreciate that a suitable fillet radius is to be applied between the platforms 60 and 62 and the airfoil portion of the vane.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without department from the scope of the invention disclosed. For example, the airfoil and/or gaspath definitions of Tables 1 and 2 may be scaled geometrically, while maintaining the same proportional relationship and airfoil shape, for application to gas turbine engine of other sizes. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
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