Abstract:
The present disclosure provides an improved second 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.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to gas turbine compressor airfoils and more particularly to improved airfoil profiles for second stage compressor blades. 
       BACKGROUND INFORMATION 
       [0002]    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 second stage blade of a compressor since it is an early stage of the compressor. 
         [0003]    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 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 
       [0004]    An exemplary embodiment provides airfoil for a second 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 18.200 degrees, the chord length is 114.000 mm, and the chamber angle is 33.900 degrees. At a second division between the first division and the second distal end of the airfoil, the airfoil height is 39.410, the stagger angle is 22.800 degrees, the chord length is 114.500 mm, and the chamber angle is 29.411 degrees. At a third division between the second division and the second distal end of the airfoil, the airfoil height is 76.380 mm, the stagger angle is 26.986 degrees, the chord length is 115.200 mm, and the camber angle is 25.991 degrees At a fourth division between the third division and the second distal end of the airfoil, the airfoil height is 128.130 mm, the stagger angle is 32.596 degrees, the chord length is 116.300 mm, and the camber angle is 22.076 degrees. At a fifth division between the fourth division and the second distal end of the airfoil, the airfoil height is 176.280 mm, the stagger angle is 37.500 degrees, the chord length is 117.500 mm, and the camber angle is 18.800 degrees. At a sixth division between the fifth division and the second distal end of the airfoil, the airfoil height is 221.540 mm, the stagger angle is 41.805 degrees, the chord length is 118.600 mm, and the camber angle is 15.639 degrees. At a seventh division between the sixth division and the second distal end of the airfoil, the airfoil height is 264.450 mm, the stagger angle is 45.700 degrees, the chord length is 119.700 mm, and the camber angle is 12.629 degrees. At an eighth division between the seventh division and the second distal end of the airfoil, the airfoil height is 291.980 mm, the stagger angle is 48.148 degrees, the chord length is 120.400 mm, and the camber angle is 10.959 degrees. At a ninth division between the eighth division and the second distal end of the airfoil, the airfoil height is 318.750 mm, the stagger angle is 50.500 degrees, the chord length is 121.000 mm, and the camber angle is 9.000 degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    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: 
           [0006]      FIG. 1  is a cross sectional view along the longitudinal axis of a portion of an exemplary compressor section of a gas turbine; 
           [0007]      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; 
           [0008]      FIG. 3  is a side view of an exemplary blade of  FIG. 1  showing airfoil height divisions in the radial direction; 
           [0009]      FIG. 4  is a chart showing the chord length versus airfoil height according to an exemplary embodiment of the present disclosure; 
           [0010]      FIG. 5  is a chart showing the stagger angle versus airfoil height according to an exemplary embodiment of the present disclosure; and 
           [0011]      FIG. 6  is a chart showing the chord length versus airfoil height of an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    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. 
         [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]      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 second 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 . 
         [0017]      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. 
         [0018]    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. 
         [0019]    The camber angle Δβ, as shown in  FIG. 2 , is defined by: 
         [0020]    the camber line CL, which is the mean line of the blade profile extending from the leading edge LE to the trailing edge TE; 
         [0021]    the inlet angle β 1   m  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 
         [0022]    the outlet angle β 2   m , 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 β 1   m  and the outlet angle β 2   m.    
         [0023]    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. 
         [0024]    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. 
         [0025]    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 second 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°. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Airfoil 
                 Stagger 
                 Chord 
                 Camber 
               
               
                   
                 height AH 
                 angle γ 
                 length CD 
                 angle Δβ 
               
               
                 Divisions 
                 (mm) 
                 (degrees) 
                 (mm) 
                 (degrees) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 A 
                 0.000 
                 18.200 
                 114.000 
                 33.900 
               
               
                 B 
                 39.410 
                 22.800 
                 114.500 
                 29.411 
               
               
                 C 
                 76.380 
                 26.986 
                 115.200 
                 25.991 
               
               
                 D 
                 128.130 
                 32.596 
                 116.300 
                 22.076 
               
               
                 E 
                 176.280 
                 37.500 
                 117.500 
                 18.800 
               
               
                 F 
                 221.540 
                 41.805 
                 118.600 
                 15.639 
               
               
                 G 
                 264.450 
                 45.700 
                 119.700 
                 12.629 
               
               
                 H 
                 291.980 
                 48.148 
                 120.400 
                 10.959 
               
               
                 I 
                 318.750 
                 50.500 
                 121.000 
                 9.000 
               
               
                   
               
             
          
         
       
     
         [0026]    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. 
         [0027]    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 
       [0000]    
       
           1  Compressor 
           5  Second stage 
           6  Blade 
           7  Rotor 
           8  Vanes 
           9  Stator 
           10  airfoil 
         γ Stagger angle 
         β 1   m  Inlet angle 
         β 2   m  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