# 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
TECHNICAL FIELD
The present disclosure relates generally to gas turbine compressor airfoils and more particularly to improved 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 stage 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 an entry blade into the compressor.
Many airfoil profiles for gas turbines have been provided. See, for example EP0 887 513 B1, which discloses the stagger angle and camber angle of an airfoil of a turbine blade. Compressor design is however at a constant state of flux driven 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 and 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. At a first division starting from the reference point, the airfoil height is 0.000 mm, the stagger angle is 18.300 degrees, the chord length is 128.000 mm, and the camber angle is 33.400 degrees. At a second division between the first division and the second distal end of the airfoil, the airfoil height is 43.890 mm, the stagger angle is 24.100 degrees, the chord length is 131.000 mm, and the camber angle is 28.900 degrees. At a third division between the second division and the second distal end of the airfoil, the airfoil height is 85.070 mm, the stagger angle is 28.778 degrees, the chord length is 133.800 mm, and the camber angle is 24.531 degrees. At a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 142.690 mm, the stagger angle is 34.291 degrees, the chord length is 137.700 mm, and the camber angle is 18.702 degrees. At a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 196.250 mm, the stagger angle is 38.600 degrees, the chord length is 141.000 mm, and the camber angle is 14.300 degrees. At a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 246.520 mm, the stagger angle is 42.215 degrees, the chord length is 143.500 mm, and the camber angle is 11.500 degrees. At a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 294.120 mm, the stagger angle is 45.647 degrees, the chord length is 145.200 mm, and the camber angle is 9.507 degrees. At an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 324.620 mm, the stagger angle is 48.025 degrees, the chord length is 146.000 mm, and the camber angle is 8.255 degrees. At a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 354.290 mm, the stagger angle is 50.500 degrees, the chord length is 354.390 mm, and the camber angle is 7.000 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 of 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.
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. Each stage of the compressor 1 includes a plurality of circumferentially spaced blades 6 mounted on a rotor 7, and a plurality of circumferentially spaced vanes 8, which are downstream of a blade 6 along the longitudinal axis LA of the compressor 1, and are 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 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 perpendicular to the longitudinal axis PA 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 β1m and the outlet angle β2m. 
    
    


As shown in FIG. 2 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.
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 exemplary 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 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
18.300
128.000
33.400


B
43.890
24.100
131.000
28.900


C
85.070
28.778
133.800
24.531


D
142.690
34.291
137.700
18.702


E
196.250
38.600
141.000
14.300


F
246.520
42.215
143.500
11.500


G
294.120
45.647
145.200
9.507


H
324.620
48.025
146.000
8.255


I
354.290
50.500
146.500
7.000









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.
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 than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.










REFERENCE SIGNS
















 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 extending to a second distal end, wherein:
at a first division starting from the reference point, the airfoil height is 0.000 mm ±10 mm, the stagger angle is 18.300 degrees ±1°, the chord length is 128.000 mm ±10 mm, and the camber angle is 33.400 degrees ±1°,
at a second division between the first division and the second distal end of the airfoil, the airfoil height is 43.890 mm ±10 mm, the stagger angle is 24.100 degrees ±1°, the chord length is 131.000 mm ±10 mm, and the camber angle is 28.900 degrees ±1°,
at a third division between the second division and the second distal end of the airfoil, the airfoil height is 85.070 mm ±10 mm, the stagger angle is 28.778 degrees ±1°, the chord length is 133.800 mm ±10 mm, and the camber angle is 24.531 degrees ±1°,
at a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 142.690 mm ±10 mm, the stagger angle is 34.291 degrees ±1°, the chord length is 137.700 mm ±10 mm, and the camber angle is 18.702 degrees ±1°,
at a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 196.250 mm ±10 mm, the stagger angle is 38.600 degrees ±1°, the chord length is 141.000 mm ±10 mm, and the camber angle is 14.300 degrees ±1°,
at a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 246.520 mm ±10 mm, the stagger angle is 42.215 degrees ±1°, the chord length is 143.500 mm ±10 mm, and the camber angle is 11.500 degrees ±1°,
at a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 294.120 mm ±10 mm, the stagger angle is 45.647 degrees ±1°, the chord length is 145.200 mm ±10 mm, and the camber angle is 9.507 degrees ±1°,
at an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 324.620 mm ±10 mm, the stagger angle is 48.025 degrees ±1°, the chord length is 146.000 mm ±10 mm, and the camber angle is 8.255 degrees ±1°and
at a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 354.290 mm ±10 mm, the stagger angle is 50.500 degrees ±1°, the chord length is 354.390 mm ±10 mm, and the camber angle is 7.000 degrees ±1°.

2. 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 extending to a second distal end, wherein:
at a first division starting from the reference point, the airfoil height is 0.000 mm ±8.33 mm, the stagger angle is 18.300 degrees ±1°, the chord length is 128.000 mm ±10 mm, and the camber angle is 33.400 degrees ±1°,
at a second division between the first division and the second distal end of the airfoil, the airfoil height is 36.574 mm ±8.33 mm, the stagger angle is 24.100 degrees ±1°, the chord length is 131.000 mm ±10 mm, and the camber angle is 28.900 degrees ±1°,
at a third division between the second division and the second distal end of the airfoil, the airfoil height is 70.889 mm ±8.33 mm, the stagger angle is 28.778 degrees ±1°, the chord length is 133.800 mm ±10 mm, and the camber angle is 24.531 degrees ±1°,
at a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 118.904 mm ±8.33 mm, the stagger angle is 34.291 degrees ±1°, the chord length is 137.700 mm ±10 mm, and the camber angle is 18.702 degrees ±1°,
at a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 163.535 mm ±8.33 mm, the stagger angle is 38.600 degrees ±1°, the chord length is 141.000 mm ±10 mm, and the camber angle is 14.300 degrees ±1°,
at a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 205.425 mm ±8.33 mm, the stagger angle is 42.215 degrees ±1°, the chord length is 143.500 mm ±10 mm, and the camber angle is 11.500 degrees ±1°,
at a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 245.090 mm ±8.33 mm, the stagger angle is 45.647 degrees ±1°, the chord length is 145.200 mm ±10 mm, and the camber angle is 9.507 degrees ±1°,
at an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 270.506 mm ±8.33 mm, the stagger angle is 48.025 degrees ±1°, the chord length is 146.000 mm ±10 mm, and the camber angle is 8.255 degrees ±1°, and
at a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 295.229 mm ±8.33 mm, the stagger angle is 50.500 degrees ±1°, the chord length is 354.390 mm ±10 mm, and the camber angle is 7.000 degrees ±1°.