Abstract:
A family of airfoils for a wind turbine blade. Each airfoil may include a blunt trailing edge, a substantially oval shaped suction side, and a substantially S-shaped pressure side.

Description:
TECHNICAL FIELD 
       [0001]    The present application relates generally to wind turbines and more particularly relates to a family of airfoil configurations for an inboard region of a wind turbine blade. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional wind turbines generally include two or more turbine blades or vanes connected to a central hub. Each blade extends from the hub at a root of the blade and continues to a tip. A cross-section of the blade is defined as an airfoil. The shape of an airfoil may be defined in relationship to a chord line. The chord line is a measure or line connecting the leading edge of the airfoil with the trailing edge of the airfoil. The shape may be defined in the form of X and Y coordinates from the chord line. The X and Y coordinates generally are dimensionless. Likewise, the thickness of an airfoil refers to the distance between the upper surface and the lower surface of the airfoil and is expressed as a fraction of the chord length. 
         [0003]    The inboard region, i.e., the area closest to the hub, generally requires the use of relatively thick foils (30%≦t/c≦40%). The aerodynamic performance of conventional airfoil designs, however, degrades rapidly for thicknesses greater than 30% of chord largely due to flow separation concerns. For thicknesses above 40% of chord, massive flow separation may be unavoidable such that the region of the blade may be aerodynamically compromised. 
         [0004]    Thus, there is a need for an airfoil design that provides improved aerodynamic performance particularly with respect to the inboard region. Preferably, such a design would provide improved aerodynamic performance and efficiency while providing improved structural stiffness and integrity. 
       SUMMARY OF THE INVENTION 
       [0005]    The present application thus provides a family of airfoils for a wind turbine blade. Each airfoil may include a blunt trailing edge, a substantially oval shaped suction edge, and a substantially S-shaped pressure side. 
         [0006]    The airfoils may include a chord line extending from a leading edge to the blunt trailing edge. The substantially oval shaped suction sides and the substantially S-shaped pressure sides do not intersect the chord line. The suction sides may include non-dimensional coordinate values of X and positive Y set forth in Tables 1-4. The pressure sides may include non-dimensional coordinate values of X and negative Y set forth in Tables 1-4. Each of airfoils is connected by a smooth curve. 
         [0007]    Each airfoil may include a first width about the blunt trailing edge, a second width moving towards a leading edge, with the second width being smaller than the first width, and a third width moving further towards the leading edge, with the third width being larger than the first width. Each airfoil may include a curved leading edge. 
         [0008]    A first airfoil may include a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 1. A second airfoil may include a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 2. A third airfoil may include a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 3. A fourth airfoil may include a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 4. Each airfoil may be an inboard region airfoil. 
         [0009]    The present application further describes a turbine blade having a number of airfoils. The airfoils may include a first airfoil with a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 1, a second airfoil with a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 2, a third airfoil with a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 3, and a fourth airfoil with a profile substantially in accordance with non-dimensional coordinate values of X and Y set forth in Table 4. The airfoils are connected by a smooth curve. 
         [0010]    The X and Y values may be scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil. The airfoils may include a number of inboard region airfoils. The turbine blade may be a wind turbine blade. 
         [0011]    These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawing and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a blade as is described herein with a number of airfoils shown. 
           [0013]      FIG. 2  is a composite plot of the airfoils as are described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a blade  100  as is described herein. The blade  100  includes the inboard region  110  adjacent to the hub (not shown), an outboard region  120  or the middle portion, and a tip region  130 . The inboard region  110  generally takes up about the first half of the blade  100  or so, the outboard region generally takes up about the next forty percent (40%) or so, and the tip  130  takes up about the final ten percent (10%) or so of the blade  100 . The figures may vary. 
         [0015]      FIG. 2  shows a family of airfoils  140 . The airfoils  140  are designed for the inboard region  110  of the blade  100 . In this example, four (4) airfoils  140  are shown, a first airfoil  150 , a second airfoil  160 , a third airfoil  170 , and a fourth airfoil  180 . An infinite number of the airfoils  140  may be used. A chord line  190  extends from, a leading edge  200  to a trailing edge  210  of each of the airfoils  140 . In this example, the chord line  190  extends through the middle of the airfoils  140 . 
         [0016]    In this example, the trailing edges  210  are blunt or have a “flat back”. The leading edges  200  are curved. Each airfoil  140  also includes a suction side  220  and a pressure side  230 . Each suction side  220  has a substantially oval shape while each pressure side  230  has a substantially S-shape. The suction sides  220  and the pressure sides  230  do not intersect the chord line  190 . Each of the airfoils  140  is connected by a smooth curve. 
         [0017]    The specific shape of the airfoil  150  is given in Table 1 in the form of dimensionless coordinates. The X/C values represent locations on the chord line  190  in relation to the trailing edge  210 . The Y/C values represent heights from the chord line  190  to point on either the suction side  220  or the pressure side  230 . The values are scalable as a function of the same constant or number to provide a scaled up or scaled down airfoil. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 x/c 
                 y/c 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1.00000000 
                 0.03726164 
               
               
                   
                 0.90036720 
                 0.06785235 
               
               
                   
                 0.80067860 
                 0.08990651 
               
               
                   
                 0.70007530 
                 0.10734770 
               
               
                   
                 0.60106600 
                 0.12091980 
               
               
                   
                 0.50066880 
                 0.13214710 
               
               
                   
                 0.40005820 
                 0.14126440 
               
               
                   
                 0.30031070 
                 0.14733190 
               
               
                   
                 0.20042560 
                 0.14654610 
               
               
                   
                 0.10049920 
                 0.12712570 
               
               
                   
                 0.00000000 
                 0.00000000 
               
               
                   
                 0.10065920 
                 −0.12659800 
               
               
                   
                 0.20022940 
                 −0.14866100 
               
               
                   
                 0.30009620 
                 −0.15000300 
               
               
                   
                 0.40096110 
                 −0.13401000 
               
               
                   
                 0.50042920 
                 −0.10618000 
               
               
                   
                 0.60041830 
                 −0.07248480 
               
               
                   
                 0.70074310 
                 −0.03982390 
               
               
                   
                 0.80018960 
                 −0.01648170 
               
               
                   
                 0.90094460 
                 −0.01118480 
               
               
                   
                 1.00000000 
                 −0.03773510 
               
               
                   
                   
               
             
          
         
       
     
         [0018]    As is shown at the X=1 location, the trailing edge  210  of the airfoil  140  has a given width. That width narrows towards the X=0.9 position, continues to narrow and then expands until past the X=0.3 position. The shape again narrows towards the leading edge  200  in a largely oval shape and then returns towards the trading edge  210 . 
         [0019]    The second airfoil  160  is similar but somewhat thicker. As above, the second airfoil  160  also has the narrowing dip between the position X=1 and the position X=0.8. The shape of the second airfoil  160  is defined as follows: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 x/c 
                 y/c 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1.00000000 
                 0.07476157 
               
               
                   
                 0.90046010 
                 0.10220790 
               
               
                   
                 0.80029790 
                 0.12248030 
               
               
                   
                 0.70049780 
                 0.13862410 
               
               
                   
                 0.60022080 
                 0.15149490 
               
               
                   
                 0.50073840 
                 0.16167160 
               
               
                   
                 0.40103380 
                 0.16936190 
               
               
                   
                 0.30001950 
                 0.17332270 
               
               
                   
                 0.20017300 
                 0.16904810 
               
               
                   
                 0.10033560 
                 0.14399980 
               
               
                   
                 0.00000000 
                 0.00000000 
               
               
                   
                 0.10085420 
                 −0.14364800 
               
               
                   
                 0.20034960 
                 −0.17120100 
               
               
                   
                 0.30024750 
                 −0.17597900 
               
               
                   
                 0.40050510 
                 −0.16227900 
               
               
                   
                 0.50051480 
                 −0.13568000 
               
               
                   
                 0.60100430 
                 −0.10275700 
               
               
                   
                 0.70074630 
                 −0.07116550 
               
               
                   
                 0.80063010 
                 −0.04891650 
               
               
                   
                 0.90051680 
                 −0.04553450 
               
               
                   
                 1.00000000 
                 −0.07523460 
               
               
                   
                   
               
             
          
         
       
     
         [0020]    The shape of the third airfoil  170  is similar to those described above, but again thicker. The third airfoil  170  also has the dip between the position X=1 and the position X=0.8. The shape of the third airfoil  170  is defined as follows: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 x/c 
                 y/c 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1.00000000 
                 0.11226081 
               
               
                   
                 0.90063769 
                 0.13652491 
               
               
                   
                 0.80109208 
                 0.15473962 
               
               
                   
                 0.70100077 
                 0.16967702 
               
               
                   
                 0.60050336 
                 0.18158922 
               
               
                   
                 0.50083265 
                 0.19073012 
               
               
                   
                 0.40094014 
                 0.19697082 
               
               
                   
                 0.30087793 
                 0.19867672 
               
               
                   
                 0.20005762 
                 0.19089852 
               
               
                   
                 0.10048941 
                 0.16042992 
               
               
                   
                 0.00000000 
                 0.00000000 
               
               
                   
                 0.10034881 
                 −0.15978302 
               
               
                   
                 0.20060802 
                 −0.19312702 
               
               
                   
                 0.30043493 
                 −0.20132002 
               
               
                   
                 0.40002894 
                 −0.18996502 
               
               
                   
                 0.50060705 
                 −0.16471402 
               
               
                   
                 0.60057116 
                 −0.13303101 
               
               
                   
                 0.70081557 
                 −0.10227001 
               
               
                   
                 0.80004708 
                 −0.08139181 
               
               
                   
                 0.90013649 
                 −0.07984641 
               
               
                   
                 0.90125599 
                 −0.07998141 
               
               
                   
                 1.00000000 
                 −0.11273501 
               
               
                   
                   
               
             
          
         
       
     
         [0021]    The shape of the fourth airfoil  180  is similar to that as described above, but again thicker. The fourth airfoil  180  has the dip between the position X=1 and the position X=0.8. The shape of the fourth airfoil  180  is defined as follows: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 x/c 
                 y/c 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1.00000000 
                 0.13726020 
               
               
                   
                 0.90000000 
                 0.15989241 
               
               
                   
                 0.80000000 
                 0.17787950 
               
               
                   
                 0.70000000 
                 0.19334258 
               
               
                   
                 0.60000000 
                 0.20609266 
               
               
                   
                 0.50000000 
                 0.21607175 
               
               
                   
                 0.40000000 
                 0.22261591 
               
               
                   
                 0.30000000 
                 0.22363103 
               
               
                   
                 0.20000000 
                 0.21369481 
               
               
                   
                 0.10000000 
                 0.17827485 
               
               
                   
                 0.00000000 
                 0.00002100 
               
               
                   
                 0.10000000 
                 −0.17758316 
               
               
                   
                 0.20000000 
                 −0.21583323 
               
               
                   
                 0.30000000 
                 −0.22630101 
               
               
                   
                 0.40000000 
                 −0.21557439 
               
               
                   
                 0.50000000 
                 −0.19017060 
               
               
                   
                 0.60000000 
                 −0.15766700 
               
               
                   
                 0.70000000 
                 −0.12602585 
               
               
                   
                 0.80000000 
                 −0.10435340 
               
               
                   
                 0.90000000 
                 −0.10306262 
               
               
                   
                 1.00000000 
                 −0.13773604 
               
               
                   
                   
               
             
          
         
       
     
         [0022]    By incorporating a relatively thick trailing edge  210 , the extent of the pressure recovery on the airfoil suction surface is alleviated. Such permits the flow to remain attached so as to provide substantial lift performance. Specifically, lift coefficients greater than 3.0 have been measured. The airfoils  140  thus provide improved aerodynamic performance and efficiency with improved structural stiffness (bending moment of inertia). These improvements lead to increase energy capture and reduce blade weight. Indirectly, the airfoils  140  also minimize the aerodynamic compromise due to transportation constraints (max chord). The dip between the 1.0 and the 0.8 positions also reduces the overall weight as compared to known blunt trailing edge designs. 
         [0023]    It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.