# Patent

## Title
Airfoil for a compressor blade

## Abstract

The present disclosure provides an improved first stage airfoil for a compressor blade having a unique chord length (CD), stagger angle (γ) and camber angle (Δβ). The stagger angle (γ) and camber angle (Δβ) provide improved aerodynamics while the chord length (CD) provides for reduced airfoil weight.

## Background
FIELD
The present disclosure relates generally to gas turbine compressor airfoils and more particularly to airfoil profiles for first stage compressor blades.
BACKGROUND INFORMATION
There are many design requirements for each stage of a gas turbine compressor in order for the stages to meet design goals including overall efficiency, airfoil loading and mechanical integrity. Of particular concern is the design of the first stage blade of a compressor, since it is the entry blade into the compressor.
Many airfoil profiles for gas turbines have been provided. See, for example EPO 887 513 B1, which discloses the stagger angle and camber angle of an airfoil of a first stage turbine blade. Compressor design is, however, at a constant state of flux due to a desire to improve efficiency. There is therefore an advantage in providing airfoil designs that improve the balance of mechanical integrity and aerodynamic efficiency in these newly developed turbines. There is therefore a desire to achieve airfoil designs to facilitate this development.
SUMMARY
An exemplary embodiment provides an airfoil for a first stage compressor blade. The exemplary airfoil comprises a plurality of chord lengths, a plurality of stagger angles, and a plurality of camber angles at a plurality of divisions, respectively, along an airfoil height starting from a reference point at a first end of the airfoil extending to a second distal end of the airfoil. At a first division starting from the reference point, the airfoil height is 0.000 mm, the stagger angle is 28.594 degrees, the chord length is 216.300, and the chamber angle is 28.919. At a second division between the first division and the second distal end of the airfoil, the airfoil height is 72.059, the stagger angle is 35.305 degrees, the chord length is 217.400 mm, and the chamber angle is 24.761 degrees. At a third division between the second division and the second distal end of the airfoil, the airfoil height is 139.669 mm, the stagger angle is 40.998 degrees, the chord length is 218.800 mm, and the camber angle is 21.093 degrees. At a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 203.900 mm, the stagger angle is 45.857 degrees, the chord length is 220.300 mm, and the camber angle is 17.883 degrees. At a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 265.358 mm, the stagger angle is 50.003 degrees, the chord length is 222.000 mm, and the camber angle is 15.100 degrees. At a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 324.430 mm, the stagger angle is 53.520 degrees, the chord length is 223.900 mm, and the camber angle is 12.714 degrees. At a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 381.390 mm, the stagger angle is 56.478 degrees, the chord length is 225.800 mm, and the camber angle is 10.695 degrees. At an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 436.490 mm, the stagger angle is 58.932 degrees, the chord length is 227.900 mm, and the camber angle is 9.014 degrees. At a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 489.880 mm, the stagger angle is 60.928 degrees, the chord length is 230.00 mm, and the camber angle is 7.644 degrees.



BRIEF DESCRIPTION OF THE DRAWINGS
Additional refinements, advantages and features of the present disclosure are described in more detail below with reference to exemplary embodiments illustrated in the drawings, in which:
FIG. 1 is a cross sectional view along the longitudinal axis of a portion of an exemplary compressor section of a gas turbine;
FIG. 2 is a top view of an exemplary airfoil of a blade of FIG. 1 used to define the characteristic dimensions of stagger angle, camber angle and chord length;
FIG. 3 is a side view of an exemplary blade of FIG. 1 showing airfoil height divisions in the radial direction;
FIG. 4 is a chart showing the chord length versus airfoil height according to an exemplary embodiment of the present disclosure;
FIG. 5 is a chart showing the stagger angle versus airfoil height according to an exemplary embodiment of the present disclosure; and
FIG. 6 is a chart showing the chord length versus airfoil height according to an exemplary embodiment of the present disclosure.



DETAILED DESCRIPTION
Exemplary embodiments of the present disclosure provide an improved airfoil having a unique profile for improved performance of a gas turbine compressor. This is accomplished by a unique airfoil profile defined in terms of stagger angle and camber angle. Further, to reduce the weight of the airfoil, a reduced chord length is provided as compared to known airfoils.
According to an exemplary embodiment, the airfoil height can be scaled down by a factor of 1:1.2. In this way, unscaled and scaled aspects provide airfoils which are suitable for operation at nominally 50 Hz and 60 Hz. respectively.
Other objectives and advantages of the present disclosure will become apparent from the following description, taken in connection with the accompanying drawings which, by way of example, illustrate exemplary embodiments of the present disclosure.
Exemplary embodiments of the present disclosure are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. However, the present disclosure may be practiced without these specific details, and the present disclosure is not limited to the exemplary embodiments disclosed herein.
FIG. 1 illustrates a portion of an exemplary multi-stage compressor 1 according to at least one embodiment of the present disclosure. Each stage of the compressor 1 comprises a plurality of circumferentially spaced blades 6 mounted on a rotor 7, and a plurality of circumferentially spaced vanes 8, which are arranged downstream of an adjacent blade 6 along the longitudinal axis LA of the compressor 1 and mounted on a stator 9. For illustration purposes, only the first stage 5 is shown in FIG. 1. Each of the different stages of the compressor 1 has a uniquely shaped vane 8 and blade 6 airfoils 10.
FIG. 2 is a top view of an airfoil 10 of a blade of FIG. 1 used to exemplarily define the airfoil 10 terms of stagger angle γ, camber angle Δβ and chord length CD used throughout this specification.
The stagger angle γ is defined, as shown in FIG. 2, as the angle between a line drawn between the leading edge LE and the trailing edge TE and a line PA that is perpendicular to the longitudinal axis LA.
The camber angle Δβ, as shown in FIG. 2, is defined by:

    
    
        the camber line CL, which is the mean line of the blade profile extending from the leading edge LE to the trailing edge TE;
        the inlet angle β1m, which is the angle, at the leading edge LE, between the line PA perpendicular to the longitudinal axis LA and a tangent to the camber line CL; and
    
    


the outlet angle β2m, which is the angle, at the trailing edge TE, between the line PA perpendicular to the longitudinal axis LA and a tangent to the camber line CL. As shown in FIG. 2, the camber angle Δβ is the external angle formed by the intersection of tangents to the camber line CL at the leading edge LE and trailing edge TE and is equal to the difference between the inlet angle β2m and the outlet angle β2m. 
As shown in FIG. 2, the chord length CD is defined as the distance between tangent lines drawn perpendicular to the longitudinal axis LA at the leading edge LE and at the trailing edge TE (see FIG. 2).
The stagger angle γ, camber angle Δβ and chord length CD, as defined in FIG. 2, can vary along the airfoil height AH (shown in FIG. 3). In order to define an airfoil 10, references can be made to divisions of the airfoil height AH (see FIG. 3). For example, FIG. 3 shows arbitrary divisions enumerated from a reference point A at the base end of the airfoil 10 and continuing to point I at a distal end of the airfoil.
An embodiment of the disclosure will now be described, by way of example, with reference to the dimensional characteristics defined in FIG. 2 at various airfoil heights AH in the radial direction as shown in FIG. 3 measured from a base end of the airfoil 10. The illustrated embodiment, which is suitable for a gas turbine compressor operating at 50 Hz, for example, comprises an airfoil 10 for the first stage 5 blade 6 of a compressor 1, as shown in FIG. 1, having chord lengths CD as set forth in Table 1 and FIG. 4, stagger angles γ as set forth in Table 1 and FIG. 5, and camber angles Δβ as set forth in Table 1 and FIG. 6, wherein the data in Table 1 and FIGS. 4 to 6 is carried to three decimal places. In another exemplary embodiment, the tolerance value for the chord lengths CD and the airfoil height AH is ±10 millimeters, and the tolerance value for the stagger angles γ and camber angles Δβ is ±1°.











TABLE 1






Airfoil
Stagger
Chord
Camber



height AH
angle γ
length CD
angle Δβ


Divisions
(mm)
(degrees)
(mm)
(degrees)



















A
0.000
28.594
216.300
28.919


B
72.059
35.305
217.400
24.761


C
139.669
40.998
218.800
21.093


D
203.900
45.857
220.300
17.883


E
265.358
50.003
222.000
15.100


F
324.430
53.520
223.900
12.714


G
381.390
56.478
225.800
10.695


H
436.490
58.932
227.900
9.014


I
489.880
60.928
230.000
7.644









In a further embodiment, the airfoil height AH is scaled down by a factor of 1:1.2 in order to be made suitable for operation at 60 Hz.
Although the disclosure has been herein shown and described in what is conceived to be an exemplary embodiment, it will be appreciated by those skilled in the art that the present disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the disclosure is indicated by the appended claims rather that the foregoing description and all changes that come within the meaning and range and equivalences thereof are intended to be embraced therein.
It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
REFERENCE NUMBERS


    1 Compressor
    5 First stage
    6 Blade
    7 Rotor
    8 Vanes
    9 Stator
    10 Airfoil
    γ Stagger angle
    β1m Inlet angle
    β2m Outlet angle
    Δβ Camber angle
    CD Chord length
    CL Camber line
    LE Leading edge
    TE Trailing edge
    LA Longitudinal axis
    PA Line perpendicular to the longitudinal axis
    AH Airfoil height
    A-I Airfoil divisions

## Claims

1. An airfoil for a first stage compressor blade, the airfoil comprising:
a plurality of chord lengths, a plurality of stagger angles, and a plurality of camber angles at a plurality of divisions, respectively, along an airfoil height starting from a reference point at a first end of the airfoil of the first stage compressor blade extending to a second distal end of the airfoil of the first stage compressor blade, wherein for operation at a nominal frequency of 50 Hz:
at a first division starting from the reference point, the airfoil height is 0.000 mm, the stagger angle is 28.594 degrees, the chord length is 216.300 mm±10 millimeters, and the camber angle is 28.919 degrees±1 degree,
at a second division between the first division and the second distal end of the airfoil, the airfoil height is 72.059 mm±10 millimeters, the stagger angle is 35.305 degrees±1 degree, the chord length is 217.400 mm±10 millimeters, and the camber angle is 24.761 degrees±1 degree,
at a third division between the second division and the second distal end of the airfoil, the airfoil height is 139.669 mm±10 millimeters, the stagger angle is 40.998 degrees±1 degree, the chord length is 218.800 mm±10 millimeters, and the camber angle is 21.093 degrees±1 degree,
at a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 203.900 mm±10 millimeters, the stagger angle is 45.857 degrees±1 degree, the chord length is 220.300 mm, and the camber angle is 17.883 degrees±1 degree,
at a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 265.358 mm±10 millimeters, the stagger angle is 50.003 degrees±1 degree, the chord length is 222.000 mm, and the camber angle is 15.100 degrees±1 degree,
at a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 324.430 mm±10 millimeters, the stagger angle is 53.520 degrees, the chord length is 223.900 mm, and the camber angle is 12.714 degrees,
at a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 381.390 mm±10 millimeters, the stagger angle is 56.478 degrees±1 degree, the chord length is 225.800 mm, and the camber angle is 10.695 degrees±1 degree,
at an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 436.490 mm±10 millimeters, the stagger angle is 58.932 degrees±1 degree, the chord length is 227.900 mm, and the camber angle is 9.014 degrees±1 degree, and
at a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 489.880 mm, the stagger angle is 60.928 degrees, the chord length is 230.000 mm, and the camber angle is 7.644 degrees±1 degree, and
wherein for operation at a nominal frequency of 60 Hz measurements the airfoil height is scaled by a factor of 1:1.2.

2. The airfoil of claim 1, wherein the values of the airfoil height, stagger angle, chord length and camber angle are carried to three decimal places.

3. An airfoil for a first stage compressor blade, comprising:
a plurality of chord lengths, a plurality of stagger angles, and a plurality of camber angles at a plurality of divisions, respectively, along an airfoil height starting from a reference point at a first end of the airfoil of the first stage compressor blade extending to a second distal end of the airfoil of the first stage compressor blade, wherein for operation at nominal frequency of 50 Hz:
at a first division starting from the reference point, the airfoil height is approximately 0.000 mm, the stagger angle is 28.594 degrees, the chord length is approximately 216.300 mm, and the camber angle is approximately 28.919 degrees,
at a second division between the first division and the second distal end of the airfoil, the airfoil height is approximately 72.059 mm, the stagger angle is approximately 35.305 degrees, the chord length is approximately 217.400 mm, and the camber angle is approximately 24.761 degrees,
at a third division between the second division and the second distal end of the airfoil, the airfoil height is approximately 139.669 mm, the stagger angle is approximately 40.998 degrees, the chord length is approximately 218.800 mm, and the camber angle is approximately 21.093 degrees,
at a fourth division between the third division and the second distal end of the airfoil, the airfoil height is approximately 203.900 mm, the stagger angle is approximately 45.857 degrees, the chord length is approximately 220.300 mm, and the camber angle is approximately 17.883 degrees,
at a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is approximately 265.358 mm, the stagger angle is approximately 50.003 degrees, the chord length is approximately 222.000 mm, and the camber angle is approximately 15.100 degrees,
at a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is approximately 324.430 mm, the stagger angle is approximately 53.520 degrees, the chord length is approximately 223.900 mm, and the camber angle is approximately 12.714 degrees,
at a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is approximately 381.390 mm, the stagger angle is approximately 56.478 degrees, the chord length is approximately 225.800 mm, and the camber angle is approximately 10.695 degrees,
at an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is approximately 436.490 mm, the stagger angle is approximately 58.932 degrees, the chord length is approximately 227.900 mm, and the camber angle is approximately 9.014 degrees, and
at a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is approximately 489.880 mm, the stagger angle is approximately 60.928 degrees, the chord length is approximately 230.000 mm, and the camber angle is approximately 7.644 degrees,
wherein the approximation of air foil height for the second through ninth divisions is within a range of±10 millimeters, the approximation of chord length for the first through ninth divisions is within a range of±10 millimeters, and the approximation of camber angle and stagger angle for the first through ninth divisions is within±1 degree,
wherein for operation at a nominal frequency of 60 Hz the airfoil height is scaled by a factor of 1:1.2.