Airfoil for energy extracting shrouded fluid turbines

Abstract

Example embodiments described herein relate an integral and/or multi-piece airfoil and a shrouded fluid turbine having the same. The airfoil can have a generally circumferential body extending circumferentially about a central axis, and can be referred to herein as a “ringed airfoil.” The airfoil can have a front portion defining a leading edge of the airfoil and a rear portion defining a trailing edge of the air foil. A cross-sectional thickness of the front portion can be non-uniform and vary along a mean camber line of the airfoil from the leading edge to a transition area. A cross-sectional thickness of the rear portion can be uniform and constant along the mean camber line of the airfoil from the transition area to the trailing edge of the airfoil.

We claim: 
     
         1 . An airfoil for an energy extracting shrouded fluid turbine comprising:
 a front portion having a generally circumferential body extending circumferentially about a central axis and defining a leading edge of the airfoil, the front portion having a non-uniform cross-sectional thickness extending along a mean camber line to a transition area; and   a rear portion having a generally circumferential body extending circumferentially about the central axis and defining a trailing edge of the airfoil, the rear portion having a substantially uniform cross-sectional thickness extending along the mean camber line from the transition area to the trailing edge.   
     
     
         2 . The airfoil of  claim 1 , wherein the front portion and the rear portion are integrally formed. 
     
     
         3 . The airfoil of  claim 1 , wherein the front portion and the rear portion are separately formed and joined to form the airfoil. 
     
     
         4 . The airfoil of  claim 4 , wherein the rear portion is detachably coupled to the front portion. 
     
     
         5 . The airfoil of  claim 4 , wherein the front portion includes a first surface and a second surface extending between the leading edge and the transition area, the first and second surface being spaced apart from each other to form an interior area, and the rear portion includes a third surface and a fourth surface extending between the transition area and the trialing edge, the third and fourth surface substantially abutting each other over a length of the rear portion. 
     
     
         6 . The airfoil of  claim 5 , wherein the interior area of the front portion is at least one of hollow and filled with foam. 
     
     
         7 . The airfoil of  claim 5 , wherein the cross-sectional thickness of the rear portion is approximately a thickness of the third and fourth surfaces. 
     
     
         8 . The airfoil of  claim 5 , wherein the first and third surfaces are continuously formed and the second and fourth surfaces are continuously formed. 
     
     
         9 . The airfoil of  claim 1 , wherein the front portion and the rear portion are formed of different materials. 
     
     
         10 . The airfoil of  claim 1 , wherein the rear portion comprises a non-rigid material. 
     
     
         11 . The airfoil of  claim 1 , wherein a cross-sectional shape of the front portion generally tapers away from the leading edge and then tapers towards the mean camber line to the transition area along the mean camber line. 
     
     
         12 . An energy extracting shrouded fluid turbine comprising:
 an energy extracting assembly including a rotor; and   an airfoil having a generally circumferential body disposed radially about the rotor, the airfoil including a front portion extending between a leading edge of the air foil and a transition area of the airfoil and a rear portion extending between the transition area and a trailing edge of the airfoil, the front portion having a non-uniform cross-sectional thickness extending along a mean camber line of the airfoil and the rear portion having a substantially uniform cross-sectional thickness extending along the mean camber line.   
     
     
         13 . The turbine of  claim 12 , wherein the airfoil is an ejector shroud positioned downstream of the rotor. 
     
     
         14 . The turbine of  claim 13 , further comprising a turbine shroud having an inlet end positioned upstream of the rotor to form a fluid flow through the shroud and passed the rotor, and an exhaust end positioned downstream of the rotor and disposed within the ejector shroud, the exhaust end including a mixing lobe to manipulate the fluid flow. 
     
     
         15 . The turbine of  claim 12 , wherein the airfoil is a turbine shroud and the rear portion comprises mixing lobes to manipulate fluid flow through the turbine. 
     
     
         16 . The turbine of  claim 12 , wherein the front portion and the rear portion are formed of different materials. 
     
     
         17 . The turbine of  claim 12 , wherein a cross-sectional shape of the front portion varies and generally tapers away from the leading edge and then towards the mean camber line to the transition area along the mean camber line. 
     
     
         18 . The turbine of  claim 15 , wherein the rear portion is formed of a fabric. 
     
     
         19 . A airfoil for an energy extracting shrouded fluid turbine comprising
 a generally circumferential body extending circumferentially about a central axis and defining a leading edge and a trailing edge of the airfoil;   a mean camber line extending between the leading edge and the trailing edge, the mean camber line bisecting a cross-section of the airfoil;   a varied cross-sectional thickness along the mean camber line between the leading edge and a transition area, the varied cross-sectional thickness varying and generally decreases towards the transition area; and   a uniform cross-sectional thickness along the mean camber line between the transition area and the trailing edge, the uniform cross-sectional thickness being substantially constant.   
     
     
         20 . The airfoil of  claim 19 , wherein a front portion is defined between the leading edge and the transition area and a rear portion is defined between the transition area and the trailing edge, the front and rear portions being separate and distinct components that are attached to form the airfoil and are formed of different materials.