Fluid energy converter

Abstract

A fluid energy converter, such as windmill or a wind turbine, includes a rotor having a front rotatable hub and a back rotatable hub. In some embodiments, a plurality of blades extends from the front hub to the back hub. A suitable blade includes a front section, a tip, and a back section. In one embodiment, the chord of the tip cross section is at an angle relative to the tangent of the rotor radius. The tip chord can be perpendicular to the direction of movement of the fluid. In some cases, the profile of a blade front section, from its root to the tip, forms a concave curve. In one case, the profile of the blade tip, from a junction root to the tip, forms a convex curve. A front section, an apex, and a back section of a blade form a generally parabolic shape.

1 . A rotor for a fluid energy converter, the rotor comprising:
 a longitudinal axis;   a front rotatable hub coaxial with the longitudinal axis;   a back rotatable hub coaxial with the longitudinal axis;   a plurality of blades, each blade comprising a front section, a tip, and a back section;   wherein the blades are arranged angularly about the longitudinal axis;   wherein each blade is attached at a front root attachment to the front hub and attached at a back root attachment end to the back hub; and   wherein the front section comprises a pitch higher than a pitch of the back section.   
     
     
         2 . The rotor of  claim 1 , wherein the rotor produces a high pressure area at an exterior surface of the blade tips. 
     
     
         3 . The rotor of  claim 1 , wherein the low pressure area begins near the front section of the blades, and wherein the difference between the low pressure area and a surrounding pressure increases toward the back section of the blades. 
     
     
         4 . The rotor of  claim 1 , wherein pressure increases within the rotor as the distance from the longitudinal axis increases. 
     
     
         5 . The rotor of  claim 1 , wherein the front section causes the fluid to be deflected radially away from the longitudinal axis. 
     
     
         6 . A rotor for a fluid energy converter, the rotor comprising:
 a longitudinal axis;   a front rotatable hub coaxial with the longitudinal axis;   a back rotatable hub coaxial with the longitudinal axis;   at least nine blades, each blade attached at a front section to the front hub and attached at a back section to the back hub, the blades positioned radially around the longitudinal axis, wherein each of at least some of the blades comprises a front section, a tip, and a back section;   wherein the front section, tip, and back section use fluid foils; and   wherein the tip chord angle is between 4 and −15 degrees.   
     
     
         7 . A fluid energy converter, comprising:
 a longitudinal axis; and   a rotatable rotor coaxial about the longitudinal axis, wherein the rotatable rotor includes a plurality of blades, each blade comprises of a front section, a tip, and a back section; and   wherein the tip chord produces tangential lift.   
     
     
         8 . The fluid energy converter of  claim 7 , which is a wind turbine with at least nine blades and where fluid accelerates through the rotor. 
     
     
         9 . The fluid energy converter of  claim 7 , further comprising a front curve, and where the front curve transitions from a primarily axial direction along the longitudinal axis to a primarily radial direction perpendicular to the longitudinal axis. 
     
     
         10 . The fluid energy converter of  claim 9 , where the front curve is designed to deflect fluid radially away from the longitudinal axis. 
     
     
         11 . A rotor for a fluid energy converter, the rotor comprising:
 a longitudinal axis;   a front rotatable hub coaxial with the longitudinal axis;   a back rotatable hub coaxial with the longitudinal axis;   a plurality of blades, each blade comprising a front section, a tip, and a back section;   wherein the blades are arranged angularly about the longitudinal axis;   wherein each blade is attached at a front root attachment to the front hub and attached at a back root attachment end to the back hub; and   wherein the front section near the front rotatable hub has an angle of attack that is lower than the angle of attack at back section near the back rotatable hub.   
     
     
         12 . The fluid energy converter of  claim 11 , where the difference between the angle of attack of the front section and the back section is greater near the front and back rotatable hubs than at the tip.