Ring airfoil with parallel inner and outer surfaces

Abstract

A ring airfoil with a voluminous leading edge region, an intermediate region, a trailing edge region including a flap. The ringed structural leading edge region combined with a rigid trailing edge region having intermediate discrete support portions extending therebetween provides sufficient rigidity to support the flap on the trailing edge region while using a membrane intermediate surface to form a portion of the intermediate region of the airfoil.

We claim: 
     
         1 . An aerodynamically contoured ring airfoil comprising;
 a body extending circumferentially about a center axis having an aerodynamic structure formed by an outer surface and an inner surface, the outer and inner surfaces extend axially with respect to the center axis along a camber line, the body including a leading edge region, a trailing edge region, and an intermediate region extends between the leading edge region and the trailing edge region;   the leading edge region having a non-uniform cross-sectional thickness extending along the camber line defined by the outer surface and the inner surface of the body; and   the trailing edge region including a flap extending therefrom and orientated at an angle with respect to a chord line of the body to allow a fluid flow flowing along the inner surface to remain attached to the inner surface.   
     
     
         2 . The airfoil of  claim 1 , wherein the flap extends from the trailing edge region perpendicularly to the chord line. 
     
     
         3 . The airfoil of  claim 1 , wherein the length of the flap is about one-tenth to about one-third a length of the chord line. 
     
     
         4 . The airfoil of  claim 1 , wherein the flap includes at least one perforation to permit fluid flow through the flap. 
     
     
         5 . The airfoil of  claim 1 , wherein the flap extends from a trailing edge of the airfoil. 
     
     
         6 . The airfoil of  claim 1 , wherein the flap extends between a first ring structure and a second ring structure, the first and second ring structures providing a hoop strength to the flap. 
     
     
         7 . The airfoil of  claim 6 , wherein the first ring structure provides a hoop strength to the trailing edge region of the body. 
     
     
         8 . The airfoil of  claim 1 , wherein the intermediate region comprises at least one intermediate support portion extending between the leading edge region and the trailing edge region. 
     
     
         9 . The airfoil of  claim 8 , wherein the intermediate support portion is composed of a rigid material. 
     
     
         10 . The airfoil of  claim 8 , wherein the intermediate support portion has a uniform cross-sectional thickness extending along the mean camber line defined by the outer surface and the inner surface of the body. 
     
     
         11 . The airfoil of  claim 8 , wherein the intermediate region comprises at least one intermediate membrane portion extending between the leading edge region and the trailing edge region. 
     
     
         12 . The airfoil of  claim 11 , wherein the intermediate membrane portion has a uniform cross-sectional thickness extending along the mean camber line defined by the outer surface and the inner surface of the body. 
     
     
         13 . The airfoil of  claim 11 , wherein the intermediate region is composed of a non-rigid material. 
     
     
         14 . The airfoil of  claim 11 , wherein the intermediate support portions provides structural support to the intermediate membrane portion. 
     
     
         15 . An energy extracting shrouded fluid turbine comprising:
 an energy extracting assembly including a rotor disposed radially about a center axis; and   an airfoil having a body extending circumferentially about the center axis, the body having an aerodynamic structure formed by an outer surface and an inner surface, the outer and inner surfaces extend axially with respect to the center axis along a camber line, the body including a leading edge region, a trailing edge region, and an intermediate region extends between the leading edge region and the trailing edge region;   the leading edge region having a non-uniform cross-sectional thickness extending along the camber line defined by the outer surface and the inner surface of the body; and   the trailing edge region including a flap extending therefrom and orientated at an angle with respect to a chord line of the body to allow a fluid flow flowing along the inner surface to remain attached to the inner surface.   
     
     
         16 . The fluid turbine of  claim 15 , wherein the flap extends from the trailing edge region perpendicularly to the chord line. 
     
     
         17 . The fluid turbine of  claim 15 , wherein the length of the flap is about one-tenth to about one-third a length of the chord line. 
     
     
         18 . The fluid turbine of  claim 16 , wherein the flap includes at least one perforation to permit fluid flow through the flap. 
     
     
         19 . The fluid turbine of  claim 15 , wherein the flap extends from the trailing edge region of the airfoil, the flap extending between a first ring structure and a second ring structure, the first and second ring structures providing a hoop strength to the flap and the first ring structure providing a hoop strength to the trailing edge region of the body. 
     
     
         20 . The fluid turbine of  claim 15 , wherein the intermediate region including at least one intermediate support portion composed of a rigid material and at least one intermediate membrane portion composed of a non-rigid material, the intermediate support portion and the intermediate membrane portion extending between the leading edge region and the trailing edge region. 
     
     
         21 . The fluid turbine of  claim 20 , wherein at least one of the intermediate support portion or the intermediate membrane portion has a uniform cross-sectional thickness extending along the mean camber line defined by the outer surface and the inner surface of the body.