Abstract:
A reactive turbine, each blade of which approximates a helical shape that is constructed with readily available conventional manufacturing techniques. The blades are constructed in discrete straight sections that, when joined, approximate a helix or any other efficient turbine shape. Each section is manufactured with the well known and readily available machine shop techniques of shaping, forming, and joining with welds or fasteners.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains to the field of unidirectional reaction turbines capable of operation under the influence of reversible fluid flows.  
       BACKGROUND OF THE INVENTION  
       [0002]     Wind and water-driven devices have been used for centuries for conversion of naturally occurring phenomena into useful power. Advances in aerodynamics and materials science have increased the efficiency and decreased the weight and friction of these devices, and concomitantly increased their usefulness. Turbine blades have progressed from primitive paddle wheels to space-age shapes with complex compound curves that require sophisticated manufacturing techniques such as numerically-controlled laser cutting, composite molding, casting, and powder metallurgy. Until demand drives production to very high levels, such manufacturing requirements make high-efficiency turbines prohibitively expensive, particularly in developing nations where wind and water could provide much-needed power sources.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention provides a means to economically utilize the advances in reactive turbine blade design. The present invention enables construction of turbine blades with complicated cross sections and non-planar configurations using conventional manufacturing techniques such as bending, shaping, forming, and welding. One embodiment of the present invention is a blade made of several discrete airfoil sections, fabricated from metal sheets, twisted and joined to form a complete blade the shape of which, as the number of discrete sections increases, approaches the helical blade design disclosed in U.S. Pat. No. 5,451,137 issued to Gorlov or the S-blade design of a troposkein disclosed in the U.S. Pat. No. 5,405,246 issued to Goldberg.  
         [0004]     The present invention satisfies a long-standing need for a method by which the high efficiencies of modern turbines, made possible by the utilization of complex aerodynamic blade designs, may be approximated with conventional manufacturing resources. Such approximations of modern blades can approach the efficiencies available to industrialized economies at a cost affordable in struggling economies such as those of third-world nations. In addition to initial affordability, the present invention&#39;s conception of blades made of discrete sections makes it possible to repair turbine blades at a cost much lower than would be required for replacement of expensive molded or cast blades. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is an isometric view of a first embodiment of the turbine of the present invention.  
         [0006]      FIG. 2   a  is an isometric view of a first embodiment of a filled turbine blade member of the present invention.  
         [0007]      FIG. 2   b  is an isometric view of a first embodiment of a turbine blade member comprised of separate members.  
         [0008]      FIG. 2   c  is an isometric view of a first embodiment of a turbine blade support member attached to a member that is in turn attached to a turbine axis of rotation shaft member.  
         [0009]      FIG. 2   d  is an isometric view of a first embodiment of a composite turbine blade attached to two turbine blade support members.  
         [0010]      FIG. 3   a  is an isometric view of a prior art continuous helical turbine blade.  
         [0011]      FIG. 3   b  is an isometric view of a first embodiment of two joined blade members of the present invention.  
         [0012]      FIG. 3   c  is a comparison of the prior art blade of  FIG. 3   a  (solid lines) with the present invention embodiment of  FIG. 3   b  (dashed lines), both designed to lie on a turbine of radius R about an axis of rotation  1 .  FIG. 3   c  also shows the overlaying cross sections of the prior art helical blade and the present invention blade at the ends of the individual present invention blade members.  
         [0013]      FIG. 4   a  shows a flat sheet that is the initial stage of an embodiment of the present invention.  
         [0014]      FIG. 4   b  shows the sheet of  FIG. 4   a  as it appears after an airfoil forming operation.  
         [0015]      FIG. 4   c  shows the airfoil as it is being twisted by a set of forming tools, prior to or after the trailing edges  32  of  FIG. 4   b  are joined.  
         [0016]      FIG. 4   d  shows two bent, twisted, and joined members  5  joined end-to-end to form part of a composite turbine blade of the present invention.  
         [0017]      FIG. 5   a  shows how to determine the angle of twist that is to be applied to a turbine blade member having a length M so that the composite turbine blade of the present invention will approximate a helical turbine blade of radius R.  
         [0018]      FIG. 5   b  shows the angle β that represents the symmetrical deviation from tangency allowed by the present invention.  
         [0019]      FIG. 6  shows one embodiment of the composite turbine blade of the present invention that discloses sections of varying cross section.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     A first embodiment  100  of the invention is shown in  FIG. 1 . Three turbine blades, each comprised of four blade members  5 , span the turbine longitudinal dimension L between three lower and three upper blade support members  3  of turbine  100  having an axis of rotation  1 , a diameter D, and a direction of rotation  2  in the direction of the blade members&#39; leading edges  4 .  
         [0021]     Construction details of one embodiment of one blade of the invention are shown in  FIGS. 2   a, b, c , and  d . The two blade support members  3  and four blade members  5  of a single turbine blade are shown in  FIG. 2   d  positioned on turbine axis of rotation  1 .  FIG. 2   a  shows a blade member filled with foam  6 .  FIG. 2   b  shows the upper and lower parts  7  and  8  and a spacer  9  of a blade member as it might be assembled from separate pieces of sheet metal.  FIG. 2   c  shows how a blade support member  3  might be constructed from two metal sheets  7  and  8 , a spacer  9 , and a connector block  10  that attaches blade support member  3  to a hub  11  or otherwise part of the turbine shaft that rotates about the turbine axis of rotation  1 .  
         [0022]      FIGS. 3   a, b , and  c  compare the present invention to a blade of the Gorlov turbine (the &#39;137 patent).  FIGS. 3   a  and  3   b  depict, respectively, the Gorlov helical blade and a twisted straight blade of the present invention.  FIG. 3   c  shows a Gorlov helical blade (solid lines) and a blade of the present invention (dashed lines) superimposed on the periphery of a turbine having a radius R.  FIG. 3   c  shows three imaginary parallel planes perpendicular to the turbine axis of rotation  1 , and the airfoil cross sections  20  at the locations where the three planes cut the blades.  
         [0023]      FIGS. 4   a, b, c , and  d  shows the progression of operations required to manufacture a turbine blade of the present invention.  FIGS. 4   a  and  4   b  show, respectively, a flat sheet in its original orientation and its symmetrical airfoil shape subsequent to a forming operation. The formed airfoil of  FIG. 4   b  shows a closed, curved leading edge  31  and an open, straight trailing edge  32 .  FIG. 4   c  shows the airfoil of  FIG. 4   b  inserted into two forms  33  and  34 . While one form, say  34 , is fixed, the other form  33  can be rotated to deform the airfoil to a desired twist. Depending on the airfoil material, it may retain its deformation with no post-twist treatment, or annealing may be required for permanent deformation fixation.  FIG. 4   d  shows two individual turbine blade members  5  joined end-to-end to form a part of one of the present invention&#39;s complete turbine blades.  
         [0024]      FIGS. 5   a  and  b  demonstrate how the angle of twist to be applied to a straight airfoil section is determined for practice of the present invention. First, any two different planes  40  and  41  containing the turbine axis of rotation  1  are defined as in  FIG. 5   a . Then points  42  and  43  are defined so that they lie, respectively, on planes  40  and  41 , separated by a distance equal to the desired length M of a turbine blade member  5  at a distance R from axis  1 . Points  42  and  43  are connected with a straight line  47  that becomes the locus of all the centers of pressure of the turbine blade member airfoil cross sections. For a helical blade approximation, locus line  47  will never lie in any plane containing the turbine axis of rotation  1 . Blade member airfoil cross sections intermediate to member endpoints  42  and  43  will all lie on the straight line  47 . For example, the airfoil cross section about point  48  will be tangent to the circular plane  46  that is defined by rotation about turbine rotation axis  1  of the line of length R from point  48  to axis  1 .  
         [0025]     The symmetrical airfoils for which points  42  and  43  are the centers of pressure are, respectively, tangent to circular planes  44  and  45  that are perpendicular to the rotation axis  1 . Alternatively, the airfoils may deviate an angle β equal to plus or minus six degrees from a tangential orientation as shown in  FIG. 5   b . The angle of twist in a turbine blade member of the present invention is therefore defined as the twist required to join all the airfoil cross sections between points  42  and  43  with straight lines between corresponding points on their respective profiles.  
         [0026]      FIG. 6  shows a feature of the present invention whereby turbine blade support members  3  that are closer to the turbine axis of rotation  1  than turbine blade members  5  can contribute more effectively to the overall turbine torque output. It is well known and established that airfoils of the same size produce greater torque with greater moment arm. The present invention provides for varying cross section size of a blade support member so that its cross section increases with its proximity to the rotation axis.  FIG. 6  shows that cross section  51  shared by blade member  5  and the mating end of blade support member  3  is smaller than cross section  52  of blade support member  3  close to the turbine shaft and hub  50 . For contributions to a trubine&#39;s overall torque, the larger size of cross section  52  helps compensate for its decreased moment arm over cross section  51 .  
         [0027]     Another embodiment of the present invention permits blade members constructed so that the cross sections are shapes other than symmetric airfoils. For example, the blade members could be formed such that their cross section shapes are any of the various asymmetrical airfoils or other shapes such as wedges.  
         [0028]     The turbine blade material of the present invention is not limited to metal. There are many engineered plastics susceptible to the forming, joining, and cutting operations required to construct the blades of the present invention.  
         [0029]     Another embodiment of the present invention calls for filling some or all of the blade members. Filling can enhance rigidity and flotation, and can be accomplished before or after individual blade members are joined. Filling techniques, such as those commonly used to fill and seal heat pipes, are commonly understood in industry.  
         [0030]     The order of application of the various blade production stages is immaterial. Blades of the present invention can be cut, bent, twisted, and closed in any order. Regardless of the order of the production stages, the end result is a plurality of discrete blade members, each having a predetermined length, two end angles, and an angle of twist so that when joined end-to-end into a composite blade, the composite blade is capable of approximating to a predetermined degree of acceptability the performance and efficiency of a continuous compound curvilinear turbine blade such as helical or tropskein blades.  
         [0031]     While the present invention has been described in terms of one preferred embodiment and a few variations thereof, it will be apparent to those skilled in the art that form and detail modifications may be made to those embodiments without departing from the spirit or scope of the invention.