Abstract:
The use of a shroud to surround a set of turbine blades works best when the blades are shaped to maximize the unique distribution of velocity of such a shroud. Parameters for the construction of such blades for both water and wind turbines are presented.

Description:
[0001]    This patent application claims the benefit of U.S. Provisional. Patent Application No. 61/028,545, entitled Provisional 2-08: One-directional bearings, Large and Small Wind, Hydro, Blade Design, filed Feb. 14, 2008 and No. 61/058,235, Provisional 6-08: Improvements to renewable energy devices, filed Jun. 3, 2008. 
     
    
     FIELD AND BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to blade designs for shrouded turbines and how they differ from regular blade designs. 
         [0003]    A shrouded turbine, particularly with the use of airfoil shapes such as the C and Farb foils described in the author&#39;s PCT IL2007/000348. Flow Deflection Devices and Methods for Energy Capture Machines, results in acceleration of velocity near the tips of the blades. This unique velocity profile requires a different blade design to take advantage of it. There the author presented the C and Farb foils and the advantages of partial foils and the need to construct a blade in such a way as to adapt it to the unique velocity patterns of a shroud were generally discussed. This patent application gives specific criteria for such a design. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
           [0005]      FIG. 1  is a diagram of an aft and side view of a blade. 
           [0006]      FIG. 2  is a diagram of a perspective view of a blade. 
           [0007]      FIG. 3  is a diagram of blade cross-sections. 
           [0008]      FIG. 4  is a diagram of pitch. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0009]    The present invention is a new set of blade designs for shrouded turbines. 
         [0010]    Definitions: For convenience, here are some common abbreviations used in the claims and the science of blade design, whether for water or wind turbines. 
         [0011]    c Chord length 
         [0012]    C L  Lift coefficient, 
         [0000]    
       
         
           
             
               C 
               L 
             
             = 
             
               
                 L 
                 / 
                 
                   1 
                   2 
                 
               
                
               ρ 
                
               
                   
               
                
               
                 V 
                 R 
                 2 
               
                
               c 
             
           
         
       
     
         [0013]    C T  Thrust coefficient, 
         [0000]    
       
         
           
             
               C 
               T 
             
             = 
             
               
                 T 
                 / 
                 
                   1 
                   2 
                 
               
                
               ρ 
                
               
                   
               
                
               
                 V 
                 S 
                 2 
               
                
               π 
                
               
                   
               
                
               
                 R 
                 2 
               
             
           
         
       
     
         [0014]    C Pwr  Power coefficient, 
         [0000]    
       
         
           
             
               C 
               P 
             
             = 
             
               
                 
                   P 
                   D 
                 
                 / 
                 
                   1 
                   2 
                 
               
                
               ρ 
                
               
                   
               
                
               
                 V 
                 S 
                 3 
               
                
               π 
                
               
                   
               
                
               
                 R 
                 2 
               
             
           
         
       
     
         [0015]    C p  Pressure coefficient, 
         [0000]    
       
         
           
             
               
                 
                   C 
                   P 
                 
                 / 
                 
                   ( 
                   
                     p 
                     - 
                     
                       p 
                       ∞ 
                     
                   
                   ) 
                 
               
               / 
               
                 1 
                 2 
               
             
              
             ρ 
              
             
                 
             
              
             
               V 
               S 
               2 
             
           
         
       
     
         [0016]    D Diameter, D=2R 
         [0017]    f Section camber 
         [0018]    G Non-dimensional circulation, G=Γ/2πRV s    
         [0019]    h Section offset 
         [0020]    J S  Advance ratio, J S =V S /nD 
         [0021]    K T  Thrust coefficient, K T =T/ρn 2 D 4    
         [0022]    K Q  Torque coefficient, K Q =Q/ρn 2 D 5    
         [0023]    n Rotational speed, rev/s 
         [0024]    L Lift (per unit span) 
         [0025]    P Pitch 
         [0026]    P D  Delivered power 
         [0027]    P v  Vapor pressure 
         [0028]    P ∞  Ambient pressure 
         [0029]    r Radial coordinate or radius of the propeller 
         [0030]    R Propeller tip radius 
         [0031]    t Section thickness 
         [0032]    T Thrust 
         [0033]    Q Torque 
         [0034]    V R  Relative velocity 
         [0035]    V S  Free steam speed 
         [0036]    V T  Tangential velocity 
         [0037]    V x  Axial velocity 
         [0038]    x,y,z Cartesian coordinate system (x+downstream, y+starboard, z+up) 
         [0039]    φ Geometric pitch angle 
         [0040]    Γ Circulation 
         [0041]    β Fluid density 
         [0042]    σ Cavitation number, 
         [0000]    
       
         
           
             σ 
             = 
             
               
                 
                   ( 
                   
                     
                       p 
                       ∞ 
                     
                     - 
                     
                       p 
                       v 
                     
                   
                   ) 
                 
                 / 
                 
                   1 
                   2 
                 
               
                
               ρ 
                
               
                   
               
                
               
                 V 
                 S 
                 2 
               
             
           
         
       
     
         [0000]    RPM Revolutions per second, RPM=60n 
         [0043]    The principles and operation of a blade in a shrouded turbine according to the present invention may be better understood with reference to the drawings and the accompanying description. 
         [0044]    Referring now to the drawings,  FIG. 1  illustrates an aft and side view of a shroud ( 1 ) and a blade ( 2 ) built according to the principles to be explained. The specific type of shroud shown here is a “Farb foil”—defined in a previous patent.  FIG. 2  is a perspective view of the same structures, This section of the patent illustrates a 10-meter diameter blade system (Radius R of 5 meters) combined with a Farb foil of 1 meter chord length in water, but its can apply to many other configurations and fluids. One can see a little how the pitch at the periphery increases. 
         [0045]      FIG. 3  is a diagram of blade cross-sections from the blade discussed. 
         [0046]    As shown in  FIG. 4 , the pitch angle (Phi) (left vertical axis) of the shrouded rotor ( 4 ) relative to the open rotor ( 3 ) is about 2 degrees higher across much of the span and increases to about 13 degrees higher locally near the tip. The Phi of an open rotor ( 3 ) substantially increases throughout. This difference is mainly due to the increased axial flow, particularly near the tip, that is induced by the shroud. At the same time, the PO ratio is different for the shrouded ( 6 ) vs. open ( 5 ) rotor. Curve ( 4 ) reaches a minimum at approximately 82% of the distance to the periphery and then increases. In contrast, the Phi curve ( 3 ) of an open rotor always decreases. The P/D ratio of a shrouded rotor ( 6 ) in this case reaches a minimum at approximately 60% of the distance to the periphery, and increases to 1.1 at the tip. By contrast, an open rotor design ( 5 ) always has a lower P/D ratio at the tip than at the root. 
         [0047]    Blades were sized to keep the maximum lift coefficient less than 0.8 in the design condition. The turbine operating at 27 rpm in a 3 m/s (5.83 kt) stream was predicted to produce a shaft power of 648 kW (869 hp). This estimate does not include mechanical losses in the hub. 
         [0048]    This table reflects the design of the optimal blade for this situation. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 r/R 
                 c/D 
                 t/c 
                 f/c 
                 φ (deg) 
                 P/D 
                 c (m) 
                 t (m) 
                 f (m) 
               
               
                   
               
             
             
               
                 0.150 
                 0.10490 
                 0.18000 
                 −0.03137 
                 50.000 
                 0.56160 
                 1.049 
                 0.189 
                 −0.033 
               
               
                 0.200 
                 0.10450 
                 0.17412 
                 −0.04396 
                 40.987 
                 0.54593 
                 1.045 
                 0.182 
                 −0.046 
               
               
                 0.300 
                 0.10249 
                 0.16235 
                 −0.05424 
                 28.650 
                 0.51493 
                 1.025 
                 0.166 
                 −0.056 
               
               
                 0.400 
                 0.09908 
                 0.15059 
                 −0.05551 
                 21.077 
                 0.48431 
                 0.991 
                 0.149 
                 −0.055 
               
               
                 0.500 
                 0.09411 
                 0.13882 
                 −0.05370 
                 16.509 
                 0.46555 
                 0.941 
                 0.131 
                 −0.051 
               
               
                 0.600 
                 0.08724 
                 0.12706 
                 −0.05056 
                 13.862 
                 0.46514 
                 0.872 
                 0.111 
                 −0.044 
               
               
                 0.700 
                 0.07829 
                 0.11529 
                 −0.04743 
                 12.168 
                 0.47418 
                 0.783 
                 0.090 
                 −0.037 
               
               
                 0.800 
                 0.06764 
                 0.10353 
                 −0.04363 
                 11.211 
                 0.49814 
                 0.676 
                 0.070 
                 −0.030 
               
               
                 0.900 
                 0.05554 
                 0.09176 
                 −0.03989 
                 11.435 
                 0.57193 
                 0.555 
                 0.051 
                 −0.022 
               
               
                 0.925 
                 0.05230 
                 0.08882 
                 −0.03908 
                 11.813 
                 0.60780 
                 0.523 
                 0.046 
                 −0.020 
               
               
                 0.950 
                 0.04896 
                 0.08588 
                 −0.03858 
                 12.701 
                 0.67266 
                 0.490 
                 0.042 
                 −0.019 
               
               
                 0.975 
                 0.04553 
                 0.08294 
                 −0.03879 
                 14.637 
                 0.79998 
                 0.455 
                 0.038 
                 −0.018 
               
               
                 1.000 
                 0.04196 
                 0.08000 
                 −0.04002 
                 18.000 
                 1.02077 
                 0.420 
                 0.034 
                 −0.017 
               
               
                   
               
             
          
         
       
     
         [0049]    The following is a design for a smaller wind turbine surrounded by a partial foil. It shows the same principle of the Phi value increasing at the periphery. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 r/R 
                 c/R 
                 Phi 
               
               
                   
               
             
             
               
                 0.13820 
                 0.295890 
                 44.95916 
               
               
                 0.15596 
                 0.286650 
                 43.01705 
               
               
                 0.18667 
                 0.270180 
                 39.76573 
               
               
                 0.22496 
                 0.250070 
                 36.09830 
               
               
                 0.26726 
                 0.229480 
                 32.10272 
               
               
                 0.31156 
                 0.210200 
                 29.05061 
               
               
                 0.35670 
                 0.192960 
                 26.41902 
               
               
                 0.40198 
                 0.177880 
                 24.53083 
               
               
                 0.44693 
                 0.164780 
                 22.56773 
               
               
                 0.49122 
                 0.153390 
                 20.90665 
               
               
                 0.53458 
                 0.143480 
                 19.51586 
               
               
                 0.57680 
                 0.134850 
                 18.35955 
               
               
                 0.61770 
                 0.127330 
                 17.38834 
               
               
                 0.65711 
                 0.120770 
                 16.56282 
               
               
                 0.69490 
                 0.115050 
                 15.84945 
               
               
                 0.73092 
                 0.110060 
                 15.22573 
               
               
                 0.76507 
                 0.105690 
                 14.70786 
               
               
                 0.79723 
                 0.101840 
                 14.30656 
               
               
                 0.82731 
                 0.098452 
                 14.00050 
               
               
                 0.85520 
                 0.095469 
                 13.78477 
               
               
                 0.88082 
                 0.092852 
                 13.64459 
               
               
                 0.90411 
                 0.090573 
                 13.56008 
               
               
                 0.92498 
                 0.088608 
                 13.51560 
               
               
                 0.94338 
                 0.086932 
                 13.49927 
               
               
                 0.95925 
                 0.085530 
                 13.49872 
               
               
                 0.97254 
                 0.084386 
                 13.50525 
               
               
                 0.98322 
                 0.083488 
                 13.51270 
               
               
                 0.99126 
                 0.082824 
                 13.51756 
               
               
                 0.99664 
                 0.082387 
                 13.52092 
               
               
                 0.99933 
                 0.082169 
                 13.52319 
               
               
                   
               
             
          
         
       
     
         [0050]    The method of improving the percentage of power obtained from a shrouded turbine involves performing at least one and preferably two of the following operations to create a better match: changing the twist at the periphery and increasing the chord length at the periphery over what might have been done for an open blade. Designing the blades with characteristics obtained from the approximate midpoint of the normalized velocity curve enables one to take ideal advantage of the increased velocity without the risk of stalling. 
         [0051]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. 
       SUMMARY OF THE INVENTION 
       [0052]    The present invention successfully addresses the shortcomings of the presently known configurations by providing a set of criteria for improving the performance of blades in a shrouded turbine. 
         [0053]    It is now disclosed for the first time a substantially 10-meter diameter blade for use with a shrouded turbine with a shroud of substantially 1-meter chord length, in any proportional value, (J s  V s /nD), with comprising the maintenance of geometric similitude and the advance ratio the following parameters (r being the radial coordinate, R the radius, with 1.000 being the tip of the blade, c the chord length, D the diameter, t the section thickness, f the section camber, φ the geometric pitch angle, P the pitch), with a deviation of 10% of the value for any point, for the values in any individual column or for any combination of any group of two or more columns in relation to the r/R value, proportional to any size blade: 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 r/R 
                 c/D 
                 t/c 
                 f/c 
                 φ (deg) 
                 P/D 
                 c (m) 
                 t (m) 
                 f (m) 
               
               
                   
               
             
             
               
                 0.150 
                 0.10490 
                 0.18000 
                 −0.03137 
                 50.000 
                 0.56160 
                 1.049 
                 0.189 
                 −0.033 
               
               
                 0.200 
                 0.10450 
                 0.17412 
                 −0.04396 
                 40.987 
                 0.54593 
                 1.045 
                 0.182 
                 −0.046 
               
               
                 0.300 
                 0.10249 
                 0.16235 
                 −0.05424 
                 28.650 
                 0.51493 
                 1.025 
                 0.166 
                 −0.056 
               
               
                 0.400 
                 0.09908 
                 0.15059 
                 −0.05551 
                 21.077 
                 0.48431 
                 0.991 
                 0.149 
                 −0.055 
               
               
                 0.500 
                 0.09411 
                 0.13882 
                 −0.05370 
                 16.509 
                 0.46555 
                 0.941 
                 0.131 
                 −0.051 
               
               
                 0.600 
                 0.08724 
                 0.12706 
                 −0.05056 
                 13.862 
                 0.46514 
                 0.872 
                 0.111 
                 −0.044 
               
               
                 0.700 
                 0.07829 
                 0.11529 
                 −0.04743 
                 12.168 
                 0.47418 
                 0.783 
                 0.090 
                 −0.037 
               
               
                 0.800 
                 0.06764 
                 0.10353 
                 −0.04363 
                 11.211 
                 0.49814 
                 0.676 
                 0.070 
                 −0.030 
               
               
                 0.900 
                 0.05554 
                 0.09176 
                 −0.03989 
                 11.435 
                 0.57193 
                 0.555 
                 0.051 
                 −0.022 
               
               
                 0.925 
                 0.05230 
                 0.08882 
                 −0.03908 
                 11.813 
                 0.60780 
                 0.523 
                 0.046 
                 −0.020 
               
               
                 0.950 
                 0.04896 
                 0.08588 
                 −0.03858 
                 12.701 
                 0.67266 
                 0.490 
                 0.042 
                 −0.019 
               
               
                 0.975 
                 0.04553 
                 0.08294 
                 −0.03879 
                 14.637 
                 0.79998 
                 0.455 
                 0.038 
                 −0.018 
               
               
                 1.000 
                 0.04196 
                 0.08000 
                 −0.04002 
                 18.000 
                 1.02077 
                 0.420 
                 0.034 
                 −0.017 
               
               
                   
               
             
          
         
       
     
         [0054]    According to another embodiment, the blade is for use in a liquid. 
         [0055]    According to another embodiment, the blade is surrounded by a foil shape. 
         [0056]    According to another embodiment, the shroud is a Farb foil. 
         [0057]    According to another embodiment, the blade is part of a system of 3 blades. 
         [0058]    According to another embodiment, the rpm is adjusted to 25-30 in a 3-meter per second flow in a liquid. 
         [0059]    It is now disclosed for the first time a turbine comprising: 
         [0060]    a. at least one shrouded blade, wherein the ratio of rpm to diameter at a 3-meter per second flow in a liquid is 2.2 to 3.2. 
         [0061]    It is now disclosed for the first time a turbine, comprising: 
         [0000]    a. an NACA series blade,
 
b. a shroud.
 
Such a type of blade is particularly effective.
 
         [0062]    According to another embodiment, the shroud comprises a C foil, with a margin of 10% for any single point. 
         [0063]    According to another embodiment, the shroud comprises a Farb foil, with a margin of 10% for any single point. 
         [0064]    According to another embodiment, the shroud is a partial foil. 
         [0065]    According to another embodiment, the blade comprises an NACA 44 series foil. 
         [0066]    It is now disclosed for the first time a shrouded blade, wherein the tip does not have the lowest Phi value. 
         [0067]    According to another embodiment, the Phi value of the tip is at least 3 degrees higher than the section with the lowest Phi value. 
         [0068]    According to another embodiment, the Phi value increases by at least 5 degrees between an r/R ratio of 0.8 to 1.0. 
         [0069]    It is now disclosed for the first time a shrouded blade, wherein the P/D ratio at the tip is greater than 0.7. 
         [0070]    According to another embodiment, the ratio is greater than 1.0. 
         [0071]    It is now disclosed for the first time a shrouded blade, wherein the Phi value starts to increase at a point 60-90% of the length from the center to the periphery. 
         [0072]    It is now disclosed for the first time a shrouded blade, wherein the P/D ratio starts to steadily increase starting from any point within 40-90% of the distance from the center to the periphery. 
         [0073]    It is now disclosed for the first time a shrouded blade, with the following parameters, in any proportional value, with a deviation of 10% of the value for any point, for the values in any individual column or for any combination of any group of both columns in relation to the r/R value, proportional to any size blade: 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 r/R 
                 c/R 
                 Phi 
               
               
                   
               
             
             
               
                 0.13820 
                 0.295890 
                 44.95916 
               
               
                 0.15596 
                 0.286650 
                 43.01705 
               
               
                 0.18667 
                 0.270180 
                 39.76573 
               
               
                 0.22496 
                 0.250070 
                 36.09830 
               
               
                 0.26726 
                 0.229480 
                 32.10272 
               
               
                 0.31156 
                 0.210200 
                 29.05061 
               
               
                 0.35670 
                 0.192960 
                 26.41902 
               
               
                 0.40198 
                 0.177880 
                 24.53083 
               
               
                 0.44693 
                 0.164780 
                 22.56773 
               
               
                 0.49122 
                 0.153390 
                 20.90665 
               
               
                 0.53458 
                 0.143480 
                 19.51586 
               
               
                 0.57680 
                 0.134850 
                 18.35955 
               
               
                 0.61770 
                 0.127330 
                 17.38834 
               
               
                 0.65711 
                 0.120770 
                 16.56282 
               
               
                 0.69490 
                 0.115050 
                 15.84945 
               
               
                 0.73092 
                 0.110060 
                 15.22573 
               
               
                 0.76507 
                 0.105690 
                 14.70786 
               
               
                 0.79723 
                 0.101840 
                 14.30656 
               
               
                 0.82731 
                 0.098452 
                 14.00050 
               
               
                 0.85520 
                 0.095469 
                 13.78477 
               
               
                 0.88082 
                 0.092852 
                 13.64459 
               
               
                 0.90411 
                 0.090573 
                 13.56008 
               
               
                 0.92498 
                 0.088608 
                 13.51560 
               
               
                 0.94338 
                 0.086932 
                 13.49927 
               
               
                 0.95925 
                 0.085530 
                 13.49872 
               
               
                 0.97254 
                 0.084386 
                 13.50525 
               
               
                 0.98322 
                 0.083488 
                 13.51270 
               
               
                 0.99126 
                 0.082824 
                 13.51756 
               
               
                 0.99664 
                 0.082387 
                 13.52092 
               
               
                 0.99933 
                 0.082169 
                 13.52319 
               
               
                   
               
             
          
         
       
     
         [0074]    It is now disclosed for the first time a method of improving the percentage of power obtained from a shrouded turbine performing at least one and preferably two of the following operations: changing the twist at the periphery and increasing the chord length at the periphery over what might have been done for an open blade.