Patent Publication Number: US-2020291919-A1

Title: Vertical axis turbine blade, turbine and wind power generation device

Description:
TECHNICAL FIELD 
     The present disclosure relates to the technical field of wind power generation, more particularly to a vertical axis wind turbine blade, a turbine and a wind power generation device. 
     BACKGROUND ART 
     Wind power generators can be divided into horizontal axis wind power generators and vertical axis wind power generators according to different relative positional relations of rotating shafts, and the horizontal axis wind power generators are relatively common wind power generation devices at present, but in recent years, the vertical axis wind power generators are also rapidly developed and increasingly widely applied. The wind turbine blade is a key part of the vertical axis wind power generator, and the shape of the wind turbine blade directly affects the startup performance and the wind energy utilization efficiency of the vertical axis wind power generator. 
     SUMMARY 
     One of the objects of the present disclosure is to provide a vertical axis wind turbine blade having a high efficiency. 
     According to an embodiment of a vertical axis wind turbine blade of the present disclosure, an outer profile of a cross section of the vertical axis wind turbine blade is a part of a symmetrical airfoil profile with the cross section being perpendicular to a vertical axis, the outer profile has a first opening, and an inner profile of the cross section is curved inwards to form a wind scoop. 
     According to an embodiment of the vertical axis wind turbine blade of the present disclosure, the symmetric airfoil profile is a first symmetrical airfoil profile of NACA four digit series, with the symmetrical airfoil profile defined by the following equation: 
         y= 5 t/c[ 0.2969  √{square root over (x/c)}− 0.126( x/c )−0.3516( x/c ) 2 +0.2843( x/c ) 3 −0.1015( x/c ) 4 ]
 
     where t is a thickness of the first symmetrical airfoil profile of NACA four digit series, and c is a chord length. 
     According to an embodiment of the vertical axis wind turbine blade of the present disclosure, the inner profile is a part of a modified second symmetric airfoil profile of NACA four digit series, a part of the second symmetric airfoil profile of NACA four digit series has a second opening, and the modified second symmetrical airfoil profile of NACA four digit series is defined by the following equation: 
     
       
         
           
             
               
                 y 
                  
                 
                     
                 
                  
                 cos 
                  
                 
                     
                 
                  
                 β 
               
               - 
               
                 
                   
                     w 
                     1 
                   
                   
                     w 
                     2 
                   
                 
                  
                 x 
                  
                 
                     
                 
                  
                 sin 
                  
                 
                     
                 
                  
                 β 
               
             
             = 
             
               5 
                
               
                 
                   t 
                   ′ 
                 
                  
                 
                   ( 
                   
                     
                       0.2969 
                        
                       
                         m 
                         0.5 
                       
                     
                     - 
                     
                       0.126 
                        
                       m 
                     
                     - 
                     
                       0.3516 
                        
                       
                         m 
                         2 
                       
                     
                     + 
                     
                       0.2843 
                        
                       
                         m 
                         3 
                       
                     
                     - 
                     
                       0.1015 
                        
                       
                         m 
                         4 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
                 
             
              
             where 
           
         
       
       
         
           
             
                 
             
              
             
               
                 m 
                 = 
                 
                   
                     
                       
                         
                           w 
                           1 
                         
                          
                         
                             
                         
                          
                         cos 
                          
                         
                             
                         
                          
                         β 
                       
                       
                         
                           w 
                           2 
                         
                          
                         c 
                       
                     
                      
                     x 
                   
                   + 
                   
                     
                       
                         sin 
                          
                         
                             
                         
                          
                         β 
                       
                       c 
                     
                      
                     y 
                   
                   + 
                   1 
                 
               
               , 
               
                 β 
                 = 
                 
                   
                     tan 
                     
                       - 
                       1 
                     
                   
                    
                   
                     
                       
                         y 
                         3 
                       
                       - 
                       
                         0.0105 
                          
                         
                           t 
                           ′ 
                         
                       
                     
                     
                       c 
                       - 
                       
                         x 
                         3 
                       
                     
                   
                 
               
               , 
             
           
         
       
     
     (x 3 , y 3 ) is coordinates of terminus of the second opening, w 1  is a width of the first opening, w 2  is a width of the second opening, and t′ is thickness of the second symmetrical airfoil profile of NACA four digit series. 
     According to an embodiment of the vertical axis wind turbine blade of the present disclosure, the first opening has an arc length that is 10%˜90% of the length of an upper arc of the first symmetrical airfoil profile of NACA four digit series, and the second opening has an arc length that is 10%˜90% of the length of an upper arc of the second symmetrical airfoil profile of NACA four digit series. 
     According to an embodiment of the vertical axis wind turbine blade of the present disclosure, an inner cavity sandwich layer is formed between the outer profile and the inner profile, the inner cavity sandwich layer has a reinforcement structure, and the reinforcement structure is a grid-like reinforcement structure or a reinforcement structure composed of ribbed plates and ribs. 
     Another object of the present disclosure is to provide a vertical axis rotor. 
     According to an embodiment of the vertical axis rotor of the present disclosure, the vertical axis rotor includes a rotor shaft and two or more vertical axis wind turbine blades as described above which are provided evenly around an axis of the rotor shaft. 
     According to an embodiment of the vertical axis rotor of the present disclosure, the vertical axis rotor includes an upper end cap and a lower end cap which are connected with the rotor shaft, and three vertical axis wind turbine blades are provided, wherein upper ends of the vertical axis wind turbine blades are connected with the upper end cap, and lower ends of the vertical axis wind turbine blades are connected with the the lower end cap. 
     According to an embodiment of the vertical axis rotor of the present disclosure, an angle of 0˜120 degrees is included between a radial direction of the vertical axis rotor and a chord line of the outer profile of a cross section of each of the vertical axis wind turbine blades, with the cross section perpendicular to the vertical axis. 
     According to an embodiment of the vertical axis rotor of the present disclosure, when wind blows toward the vertical axis rotor, a wind scoop of a wind turbine blade on a windward side directly converts the coming airflow into kinetic energy, the rest of the airflow blows to the other two wind turbine blades, and the airflow acceleratedly flowing over cambered surfaces of the other two wind turbine blades forms negative pressure so as to increase a rotating speed and a torque of the wind turbine blades. 
     A further object of the present disclosure is to provide a vertical axis wind power generation device. 
     According to an embodiment of the vertical axis wind power generation device of the present disclosure, the vertical axis wind power generation device includes a power generator and the vertical axis rotor as described above, and a rotating shaft of the power generator is connected with the rotor shaft of the vertical axis rotor. 
     In the present disclosure, the outer profile of the vertical axis wind turbine blades adopt the symmetrical airfoil profile of NACA four digit series, wherein the inner profile is curved inwards to form the wind scoop, and when wind blows to the wind turbine blades, the wind scoop can directly convert airflow into kinetic energy, and airflow acceleratedly flowing over the cambered surfaces of the outer profiles of the wind turbine blades can produce negative pressure so as to increase the rotating speed and the torque of the wind turbine blades. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Below the present disclosure will be further described in combination with accompanying drawings and embodiments, and in the accompanying drawings: 
         FIG. 1  is a cross-sectional diagram of an embodiment of a vertical axis wind turbine blade of the present disclosure; 
         FIG. 2  is a perspective schematic diagram of an embodiment of a vertical axis rotor of the present disclosure; 
         FIG. 3  is a structural schematic diagram of the vertical axis rotor shown in  FIG. 2 ; 
         FIG. 4  is a schematic diagram of wind turbine blades of the vertical axis rotor shown in  FIG. 2 ; 
         FIG. 5  is a cross-sectional diagram of the vertical axis rotor shown in  FIG. 2 ; 
         FIG. 6  is a schematic diagram of an symmetrical airfoil profile of NACA four digit series; 
         FIG. 7  is a simulation schematic diagram of the vertical axis rotor shown in  FIG. 2  under wind action; and 
         FIG. 8  is a cross-sectional diagram of another embodiment of the vertical axis wind turbine blade of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     For the sake of clearer understanding of technical features, objects and effects of the present disclosure, specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. 
     Embodiments of a vertical axis wind turbine blade, a turbine and a wind power generation device of the present disclosure are described in detail below, and examples of these embodiments are shown in the accompanying drawings, in which same or similar signs represent same or similar elements or elements having same or similar functions throughout the accompanying drawings. 
     In the description of the vertical axis wind turbine blade, the turbine and the wind power generation device of the present disclosure, it should be understood that orientational or positional relations indicated by terms “front”, “rear”, “upper”, “lower”, “upper end”, “lower end”, “upper part”, “lower part” and so on are based on orientational or positional relations shown in the accompanying drawings, merely for facilitating the description of the present disclosure and simplifying the description, rather than indicating or implying that related devices or elements have to be in the specific orientation or configured and operated in a specific orientation, and therefore, they should not be construed as limitation on the present disclosure. Besides, terms “first”, “second” and so on are merely used for descriptive purpose, but should not be construed as indicating or implying relative importance. 
     The NACA airfoil profile described in the present disclosure is a series of airfoil profiles developed by National Advisory Committee for Aeronautics (NACA), USA. The code of each airfoil profile consists of four letters “NACA” and a series of digits, and a precise shape of the airfoil profile can be obtained just by substituting geometric parameters described by the series of digits into a specific equation. 
     As shown in  FIG. 1 , it is a cross-sectional diagram of an embodiment of a vertical axis wind turbine blade of the present disclosure, wherein this cross section is a cross section of the vertical axis wind turbine blade perpendicular to a vertical axis. The cross section of the vertical axis wind turbine blade  100  has an outer profile  110  and an inner profile  120 , wherein the outer profile  110  has a first opening  111 , the outer profile  110  is a part of a symmetrical airfoil profile of NACA four digit series, that is, the outer profile  110  is a part of the symmetrical airfoil profile among the airfoil profiles of NACA four-digit series, and the inner profile  120  is curved inwards to form a wind scoop  130 . The vertical axis wind turbine blade  100  of the present disclosure may be made of lightweight alloy materials or composite materials having relatively high strength, or made of from lightweight alloy materials and composite materials, such as aluminum alloys and other commonly used materials. In order to increase the strength of the vertical axis wind turbine blade  100 , a grid-like reinforcement structure  141  can be provided in an inner cavity sandwich layer  140  formed between the outer profile  110  and the inner profile  120 , so as to enhance the overall strength of the vertical axis wind turbine blade  100 . The grid-like reinforcement structure  141  is preferably a triangular grid, but is not limited to the triangular grid, and may also be a quadrilateral grid, a pentagonal grid or other polygonal grids or grids having other shapes. In the cross-sectional diagram of another embodiment of the vertical axis wind turbine blade as shown in  FIG. 8 , the reinforcement structure of the inner cavity sandwich layer  140  formed between the outer profile  110  and the inner profile  120  of the vertical axis wind turbine blade  100  is composed of ribbed plates  142  and ribs  143 , wherein each ribbed plate  142  has one side connected with the outer profile  110 , and the other side connected with the inner profile  120 , and the ribs  143  can be formed on an inner side of the outer profile  110  or on an inner side of the inner profile  120 . The presence of the ribbed plates  142  and the ribs  143  can enhance the strength of the entire vertical axis wind turbine blade  100 . 
     Referring to  FIG. 5 , in an embodiment of the vertical axis wind turbine blade of the present disclosure, the outer profile  110 , i.e. curve a in the figure, which is a part of the symmetrical airfoil profile among the airfoil profiles of NACA four digit series, and has a shape defined by the following equation: 
         y= 5 t/c[ 0.2969  √{square root over (x/c)}− 0.126( x/c )−0.3516( x/c ) 2 +0.2843( x/c ) 3 −0.1015( x/c ) 4 ]
 
     where t is a thickness of the symmetrical airfoil profile, and c is a chord length. 
     The curve a, i.e. the outer profile  110 , has a first opening p, and an arc length of the first opening p is 10%˜90% of the length of an upper arc of the symmetrical airfoil profile of NACA four digit series. Referring to  FIG. 6 , a schematic diagram of the symmetrical airfoil profile of NACA four digit series, the upper arc is a curve of an upper half of the symmetrical airfoil profile. 
     Referring to  FIG. 5 , in an embodiment of the vertical axis wind turbine blade of the present disclosure, the inner profile  120 , i.e. curve b in the figure, which is a part of a modified symmetrical airfoil profile of NACA four digit series, the modified symmetrical airfoil profile is obtained by modifying a curve b′ upon rotation and scaling so as to match openings w 1  and w 2 , such that two corresponding openings coincide end to end. The b′, a part of a unmodified symmetrical airfoil profile of NACA four digit series, which has a second opening p′, and the modified second symmetric airfoil profile of NACA four digit series, i.e. curve b, is defined by the following equation: 
     
       
         
           
             
               
                 y 
                  
                 
                     
                 
                  
                 cos 
                  
                 
                     
                 
                  
                 β 
               
               - 
               
                 
                   
                     w 
                     1 
                   
                   
                     w 
                     2 
                   
                 
                  
                 x 
                  
                 
                     
                 
                  
                 sin 
                  
                 
                     
                 
                  
                 β 
               
             
             = 
             
               5 
                
               
                 
                   t 
                   ′ 
                 
                  
                 
                   ( 
                   
                     
                       0.2969 
                        
                       
                         m 
                         0.5 
                       
                     
                     - 
                     
                       0.126 
                        
                       m 
                     
                     - 
                     
                       0.3516 
                        
                       
                         m 
                         2 
                       
                     
                     + 
                     
                       0.2843 
                        
                       
                         m 
                         3 
                       
                     
                     - 
                     
                       0.1015 
                        
                       
                         m 
                         4 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
                 
             
              
             where 
           
         
       
       
         
           
             
                 
             
              
             
               
                 m 
                 = 
                 
                   
                     
                       
                         
                           w 
                           1 
                         
                          
                         
                             
                         
                          
                         cos 
                          
                         
                             
                         
                          
                         β 
                       
                       
                         
                           w 
                           2 
                         
                          
                         c 
                       
                     
                      
                     x 
                   
                   + 
                   
                     
                       
                         sin 
                          
                         
                             
                         
                          
                         β 
                       
                       c 
                     
                      
                     y 
                   
                   + 
                   1 
                 
               
               , 
               
                 β 
                 = 
                 
                   
                     tan 
                     
                       - 
                       1 
                     
                   
                    
                   
                     
                       
                         y 
                         3 
                       
                       - 
                       
                         0.0105 
                          
                         
                           t 
                           ′ 
                         
                       
                     
                     
                       c 
                       - 
                       
                         x 
                         3 
                       
                     
                   
                 
               
               , 
             
           
         
       
     
     (x 3 , y 3 ) is coordinates of terminus of the second opening p′, w 1  is a width of the first opening p, w 2  is a width of the second opening p′, and t′ is the thickness of the symmetrical airfoil profile of NACA four digit series, i.e. thickness of the symmetrical airfoil profile of NACA four digit series corresponding to the curve b′. The second opening p′ has an arc length that is 10%˜90% of the length of the upper arc of the symmetrical airfoil profile of NACA four digit series. 
     It should be understood that the specific curve equations above are merely illustrative rather than restrictive, and that the curves of the outer profile and the inner profile of the vertical axis wind turbine blade of the present disclosure may be a part of other symmetrical airfoil profiles, and are not limited to the specific equations above, nor to the symmetrical airfoil profiles of NACA four digit series. 
     Referring to  FIG. 2  to  FIG. 5 , which are schematic diagrams of an embodiment of a vertical axis rotor of the present disclosure, the vertical axis rotor (or wind turbine)  200  includes rotor shafts (or wind turbine shafts)  210  and  220 , and three vertical axis wind turbine blades  100   a ,  100   b , and  100   c  provided evenly around axes of the rotor shafts  210  and  220 , the rotor shaft  210  is connected with an upper end cap  230 , upper ends of the vertical axis wind turbine blades  100   a ,  100   b , and  100   c  are connected with the upper end cap  230 , respectively, lower ends of the vertical axis wind turbine blades  100   a ,  100   b , and  100   c  are connected with a lower end cap  240 , respectively, and the lower end cap  240  is connected with the rotor shaft  220 . An angle of 0˜120 degrees is included between a radial direction of the vertical axis rotor  200  and a chord line of an outer profile of a cross section of each of the vertical axis wind turbine blades  100   a ,  100   b , and  100   c , with the cross section perpendicular to the vertical axes. 
     It should be understood that the number of wind turbine blades of the vertical axis rotor  200  of the present disclosure is not limited to three, and may be two or other numbers. 
     Referring to  FIG. 7 , when wind blows toward the vertical axis rotor  200 , a wind scoop of a wind turbine blade on a windward side directly converts the coming airflow into kinetic energy, and after passing over the first wind turbine blade, the airflow flows onto arcs of the second and the third wind turbine blades, then the airflow acceleratedly flowing over the second and third wind turbine blades provides a lift force which cooperates with a centripetal force of the wind turbine blades, thus a rotational torque and speed of the entire vertical axis rotor are increased, thereby improving the efficiency of the vertical axis wind turbine. 
     In addition to the vertical axis wind turbine blades and the vertical axis rotor described above, the present disclosure further provides a vertical axis wind power generation device, including a power generator and the vertical axis rotor as described above, wherein a rotating shaft of the power generator is connected with the rotor shafts of the vertical axis rotor. 
     The embodiments of the present disclosure are described above in conjunction with the accompanying drawings, but the present disclosure is not limited to the above specific embodiments. The above specific embodiments are merely illustrative, rather than restrictive, and those ordinarily skilled in the art still could obtain many forms in light of the present disclosure without departing from the essence of the present disclosure and, and these forms shall be covered by the scope of protection of the present disclosure.