Patent Application
20190071986
The application relates generally to a vane airfoil for a gas turbine engine and, more particularly, to an airfoil profile suited for use in a first stage of compressor turbine (CT) vanes.
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 turbine section 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.
In one aspect, there is provided a compressor turbine vane for a gas turbine engine comprising an airfoil having a portion defined by a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z of Sections 3 to 9 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 compressor 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, there is provided a compressor turbine vane for a gas turbine engine, the compressor turbine vane having a cold coated intermediate airfoil portion defined by a nominal profile substantially in accordance with Cartesian coordinate values of X, Y, and Z of Sections 3 to 9 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, there is provided 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 3 to 9 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, there is provided a compressor 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 coordinates given in Table 1, wherein a fillet radius is applied around the airfoil between the airfoil and platforms.
Reference is now made to the accompanying figures depicting aspects of the present invention, in which:
The compressor turbine 18b has a single high pressure turbine (HPT) stage located in the gaspath 27 downstream of the combustor 16. Referring to
Table 1 provides gaspath definition from upstream to downstream of the CT vane stage 40 relative to its stacking line 44 (X=0 at stacking line 44).
The novel airfoil shape of each CT vane 40 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 single stage CT vane disposed upstream of two power turbine stages. 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 CT vane stacking line 44 of each respective vane 40 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 CT 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” non-operating coated condition (and at nominal restagger). However, the manufactured airfoil surface profile will be slightly different, as a result of manufacturing and applied coating tolerances. According to an embodiment, the coated condition includes a thermal barrier coating (TBC).
The Table 2 values are generated and shown to three decimal places for determining the profile of the CT 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 ±0.018 inches, measured perpendicularly to the airfoil surface is additive to the nominal values given in Table 2 below. The profile tolerance accounts for airfoil profile casting, coating and TBC tolerances. The CT vane airfoil design functions well within these ranges of variation. The cold or room temperature profile (including coating) 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 CT vane airfoil profile.
It should be understood that the finished CT vane 40 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 airfoil profile proximal to the platforms 60 and 62 may vary due to several imposed constraints. However, the CT vane 40 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 CT 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. The airfoil profile physically appearing on CT vane 40a and fully contained in the gaspath may include Sections 3 to 9 of Table 2. 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 vane inner diameter and outside diameter endwall fillets are in the range of about 0.0625″ to about 0.240″.
The above described vane design minimizes static pressure gradients in the spanwise direction, to minimize secondary losses and to beneficially align the flow entering the CT blade stage.
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. 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.
