Abstract:
According to one embodiment of the present invention, a rotating blade, having a collision face that collides with fluid and is rotated by the flow of said fluid, has at least one flow path that has been caved in from said colliding face; said flow path is located forward with respect to said rotation direction so that it is located in the rear with respect to the inlet wherein said flow is introduced and said rotation direction, and it has an outlet from which said fluid exits. Here, the cross-sectional area of said inlet may be greater than the cross-sectional area of said outlet. In addition, the cross-sectional area of said inlet may gradually decrease toward said outlet.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a rotating blade and an air foil, and more particularly, to a rotating blade and an air foil rotated or lifted by a flow of fluid. 
         [0003]    2. Background Art 
         [0004]    Wind energy has been used as a source of mechanical power for a long time. Wind power generated by a flow of wind is transmitted to a blade as wind collides with a collision face of the blade, and the wind energy is converted into a mechanical energy while the blade rotates by the wind power. Such a mechanical energy may be converted into an electric energy through a turbine, and in this instance, a conversion efficiency is crucial to the energy conversion. 
         [0005]    In order to obtain a great deal of electric energy from the same amount of mechanical energy, it is preferable that the blade has a high energy conversion efficiency. That is, when the initial wind energy is converted into a mechanical energy through the blade, the amount of the mechanical energy obtainable from wind energy of the same power varies according to shapes (or structures) of blades, and the energy conversion efficiency shall be determined according to the amount of obtainable energy. 
         [0006]    Meanwhile, when wind flows along the upper face and the lower face of an air foil, a lifting force substantially vertical to a wind flow direction, whereby the lifting force is applied on the air foil. The lifting force can lift the air foil up from the ground. That is, wind power is converted into lifting force, and as described above, in case of the high energy conversion efficiency, a great deal of lifting force can be obtained from wind power of the same power. 
       DISCLOSURE 
     Technical Problem 
       [0007]    Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide a rotating blade and an air foil, which can be moved by a flow of fluid. 
         [0008]    It is another object of the present invention to provide a rotating blade and an air foil, which can provide a high energy conversion efficiency. 
         [0009]    The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings. 
       Technical Solution 
       [0010]    To accomplish the above object, according to the present invention, there is provided a rotating blade, which has a collision face colliding with fluid and is rotated by a flow of the fluid, including at least one flow path that is caved from the colliding face, wherein the flow path includes an inlet located forward with respect to a rotation direction for inflow of the fluid and an outlet located backward with respect to the rotation direction for outflow of the fluid. 
         [0011]    Furthermore, the cross-sectional area of the inlet may be greater than the cross-sectional area of the outlet. Additionally, the cross-sectional area of the inlet gradually decreases toward the outlet. 
         [0012]    Moreover, a plurality of the flow paths are disposed, and the flow paths are arranged side by side ranging from an end of the rotating blade to the rotation center of the rotating blade. 
         [0013]    In addition, the flow paths are formed in an arc shape around the rotation center of the rotating blade. 
         [0014]    In another aspect of the present invention, there is provided an air foil, which has an upper face and a lower face where fluid flows, and, to which a lifting force is applied, including at least one flow path that is caved from the upper face, wherein the flow path includes an inlet located at the front end thereof for inflow of the fluid and an outlet located at the rear end thereof for outflow of the fluid. 
       Advantageous Effects 
       [0015]    The rotating blade according to the present invention has a high energy conversion efficiency. That is, the rotating blade has a high rotational frequency by the flow of fluid, which has a predetermined kinetic energy, such that the mechanical energy generated by the flow of the fluid is increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a view showing that a propeller is mounted inside a wind tunnel. 
           [0017]      FIG. 2  is a view of a propeller according to a preferred embodiment of the present invention. 
           [0018]      FIGS. 3 and 4  are sectional views of a blade of the propeller of  FIG. 2 . 
           [0019]      FIGS. 5 and 6  are graphs showing results of tests using the propeller of  FIG. 2 . 
           [0020]      FIG. 7  is a view of a blade according to another preferred embodiment of the present invention. 
           [0021]      FIG. 8  is a view of an air foil according to a further preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    Reference will be now made in detail to the preferred embodiments of the present invention with reference to the attached  FIGS. 1 to 6 . The embodiments of the present invention can be modified in various forms, and the scope of the present invention shall not be restricted to the embodiments, which will be described later. These embodiments are provided to describe this invention in more detail to those skilled in the art. Accordingly, shapes of components illustrated in the drawings can be exaggerated in order to provide more detailed descriptions of the components. 
         [0023]      FIG. 1  is a view showing that a propeller is mounted inside a wind tunnel. The wind tunnel  10  is disposed widthwise, and includes a fan mounted at a right side end and an exhaust outlet formed at a left side end. A fluid flow (V 1 ) provided through the fan passes (V) through a propeller  20 , and then, goes toward the exhaust outlet (V 2 ). 
         [0024]    The propeller  20  is rotatably mounted on a support member  30 . The propeller  20  is substantially perpendicular to the wind tunnel  10 , and rotates by the fluid flow (V) inside the wind tunnel  10 . 
         [0025]      FIG. 2  is a view of a propeller according to a preferred embodiment of the present invention, and  FIGS. 3 and 4  are sectional views of a blade of the propeller of  FIG. 2 . 
         [0026]    The propeller  20  includes first and second rotating blades  22  and  26 .  FIG. 2(   a ) illustrates a propeller  20  according to a prior art, and  FIG. 2(   b ) illustrates a propeller according to the preferred embodiment of the present invention. Differently from the propeller  20  according to the prior art, the first and second rotating blades  22  and  26  respectively have a plurality of flow paths  24  and  28 . As shown in  FIG. 2(   b ), the flow paths  24  and  28  are substantially perpendicular to a longitudinal direction of the rotating blades  22  and  26  and are arranged side by side with each other. The flow paths  24  and  28  are separated apart from each other ranging from ends of the rotating blades  22  and  26  to the rotation center of the rotating blades  22  and  26 . 
         [0027]    In this instance, as shown in  FIG. 3 , the flow path  24  has an inlet  24   i  and an outlet  24   o . The inlet  24   i  is located forward with respect to the rotation direction, and the outlet  24   o  is located backward with respect to the rotation direction. That is, referring to  FIG. 2(   b ), the propeller  20  is rotated in the counterclockwise direction, and the inlet  24   i  is formed at the lower portion of the flow path  24  and the outlet  24   o  is formed at the upper portion of the flow path  24 . 
         [0028]    Moreover, as shown in  FIGS. 3 and 4 , a width (di) of the inlet  24   i  is larger than a width (do) of the outlet  24   o . That is, the cross-sectional area of the inlet  24   i  is greater than that of the outlet  24   o . Furthermore, the cross-sectional area of the inlet  24   i  is gradually decreases toward the outlet  24   o.    
         [0029]    In the meantime, the flow path  28  formed in the second rotating blade  26  is in rotational symmetry relations at an angle of 180 degrees to the flow path  24  formed in the first rotating blade  22 . That is, when the first rotating blade  22  is rotated at an angle of 180 degrees on the rotation center, it has the same structure as the second rotating blade  26 . 
         [0030]    As described above, the fluid flow (V) is formed in the wind tunnel  10  by the fan, and the fluid flow (V) rotates the propeller  20  while colliding with the propeller  20 . In this instance, the fluid flow (V) is introduced into the flow path  24  through the inlet  24   i  and goes along the flow path  24 , and then, is separated from the flow path  24  via the outlet  24   o . In this instance, the cross-sectional area of the inlet  24   i  gradually decreases, and hence, a speed (Vo) of the fluid flow (V) measured at the outlet  24   o  is greater than a speed (Vi) of the fluid flow (V) measured at the inlet  24   i . That is, the fluid flow (V) is accelerated while moving from the inlet  24   i  toward the outlet  24   o.    
         [0031]      FIGS. 5 and 6  are graphs showing results of tests using the propeller of  FIG. 2 . First, conditions for tests will be described. The rotational frequency of the fan mounted inside the wind tunnel  10  was set to 1800 rpm and the rotation frequency was kept during the test. Additionally, a distance between the propeller  20  and the fan mounted inside the wind tunnel  10  was about 400 mm. 
         [0032]    First,  FIG. 5  is a graph showing changes in the rotational frequency of the propeller  20  according to the number of the flow paths  24  and  28  formed in the rotating blades  22  and  26 . As shown in  FIG. 2(   b ), the flow paths  24  and  28  are formed in order ranging from the ends of the rotating blades  22  and  26  to the rotation center of the rotating blades  22  and  26 , for instance, in the case that five flow paths  24  and  28  are formed, Number 1 to Number 5 flow paths  24  and  28  are formed but Number 6 to Number 9 flow paths  24  and  28  are not formed. 
         [0033]    Referring to  FIG. 5 , the rotational frequency is increased more in the case that the flow paths  24  and  28  are formed (N=1, 2, . . . , and 9) than in the case that the flow paths  24  and  28  are not formed (N=0). Especially, in the case that a plurality of the flow paths  24  and  28  are formed (N=2, 3, . . . , and 9), the rotational frequency is increased dramatically. ▪ in  FIG. 5  means an average value of the measured rotational frequency. 
         [0034]    That is, in the case that the flow paths  24  and  28  where the cross-sectional area of the inlet  24   i  is greater than the cross-sectional area of the outlet  24   o  is formed, the rotational efficiency of the propeller  20  increases. The reason is that power of a vector is additionally produced and it increases a rotational force because the speed of the fluid flow (V) on the flow paths  24  and  28  increases. 
         [0035]      FIG. 6  is a graph showing changes in the rotational efficiency of the propeller  20  according to the number of the flow paths  24  and  28  formed in the rotating blades  22  and  26 . In the same way, as shown in  FIG. 2(   b ), the flow paths  24  and  28  are formed in order ranging from the ends of the rotating blades  22  and  26  to the rotation center of the rotating blades  22  and  26 , for instance, in the case that five flow paths  24  and  28  are formed, Number 1 to Number 5 flow paths  24  and  28  are formed but Number 6 to Number 9 flow paths  24  and  28  are not formed. 
         [0036]    Referring to  FIG. 6 , the rotational efficiency is increased more in the case that the flow paths  24  and  28  are formed (N=1, 2, . . . , and 9) than in the case that the flow paths  24  and  28  are not formed (N=0). Especially, in the case that a plurality of the flow paths  24  and  28  are formed (N=2, 3, . . . , and 9), the rotational efficiency is increased five to eight times as much as the rotational efficiency in the case that one flow path  24  and  28  is formed. 
         [0037]    According to the above, the propeller  20  may have a high energy conversion efficiency. That is, because the predetermined fluid flow (V) is accelerated on the flow path  24  and the rotating blades  22  and  26  have greater rotation speed, a predetermined energy may be converted into greater mechanical energy, and it show the high energy conversion efficiency. 
         [0038]    While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention. The fluid in the present invention includes gas and liquid. 
         [0039]    Meanwhile, in this embodiment, the flow paths  24  and  28  are described with sizes of the cross-sectional areas of the inlet  24   i  and the outlet  24   o  as the central figure, but in order to prevent entrance and exit loss (loss due to separation of flow or loss of head) occurring when the fluid flow (V) is introduced into the flow paths  24  and  28 , shapes and widths (di and do) of the inlet  24   i  and the outlet  24   o  may be changed. Especially, if the inlet  24   i  and the outlet  24   o  are formed in a streamlined shape, it may minimize a drag force generated relative to the fluid flow (V), and can control the widths (di and do) of the inlet  24   i  and the outlet  24   o  as the speed of the fluid flow (V) increases. Such contents may be applied to the propeller  20 , which are previously described, propellers  20 , which will be described later, and an air foil  40 , which will be described later. 
       MODE FOR INVENTION 
       [0040]      FIG. 7  is a view of a propeller according to another preferred embodiment of the present invention. Differently from the propeller of  FIG. 2(   b ), flow paths  24  and  28  may be formed in an arc shape around the rotation center of the propeller  20 . 
         [0041]    As described above, the rotational efficiency is increased by the flow paths  24  and  28 , and especially, the speed of the fluid flow (V) gradually increases while fluid flows from the inlet  24   i , which is wide, to the outlet  24   o , which is narrow, and hence, it increases the rotational efficiency. 
         [0042]      FIG. 8  is a view of an air foil  40  according to a further preferred embodiment of the present invention. As shown in  FIG. 8 , the air foil  40  has a front end  42  located on the upstream side relative to the fluid flow (V) and a rear end  44  located on the downstream side relative to the fluid flow (V). The fluid flow (V) goes along an upper face  46  and a lower face of the air foil  40  through the front end  42  of the air foil  40 , and then, gets out of the air foil  40  through the rear end  44  of the air foil  40 . 
         [0043]    The air foil  40  includes at least one flow path  48  caved from the upper face  46  thereof, and the flow path  48  has an inlet  48   i  and an outlet  480 . The inlet  48   i  is located at the front end  42  of the air foil  40 , and the outlet  48   o  is located at the rear end  44  of the air foil  40 . 
         [0044]    Furthermore, as shown in  FIG. 8 , the inlet  48   i  is wider than the outlet  480 . That is, the cross-sectional area of the inlet  48   i  is greater than the cross-sectional area of the outlet  480 . Additionally, the cross-sectional area of the inlet  48   i  gradually decreases toward the outlet  480 . 
         [0045]    As described above, the fluid flow (V) going along the upper face  46  of the air foil  40  is introduced into the flow path  48  through the inlet  48   i  and goes along the flow path  48 , and then, is separated from the flow path  48  through the outlet  480 . In this instance, because the cross-sectional area of the inlet  48   i  gradually decreases, the speed of the fluid flow (V) measured at the outlet  48   o  is greater than the speed of the fluid flow (V) measured at the inlet  48   i . That is, the fluid flow (V) is accelerated from the inlet  48   i  to the outlet  480 . 
         [0046]    Accordingly, a difference between the speed of the fluid flow (V) going along the upper face  46  of the air foil  40  and the speed of the fluid flow (V) going along the lower face of the air foil  40  grows. Therefore, lifting force (L) applied to the air foil  40  increases. 
         [0047]    Because the speed of the fluid speed (V) going along the upper face of the air foil  40  increases by the flow path  48  and speed and pressure are in an inverse relationship according to Bernoulli&#39;s equation, a pressure difference between the upper face  46  of the air foil  40  and the lower face of the air foil  40  grows, and the lifting force (L) applied to the air foil  40  increases. Accordingly, a size of the lifting force on the same fluid flow (V) is increased by the flow path  48 , and the energy conversion efficiency is also increased by the flow path  48 . 
       INDUSTRIAL APPLICABILITY 
       [0048]    The blade and the air foil according to the present invention may be used in various kinds of products.