Fluid Turbine With Turbine Shroud And Ejector Shroud Coupled With High Thrust-Coefficient Rotor

Abstract

The present disclosure includes a shrouded fluid turbine that generates large wake expansion to generate power coefficients greater than the Betz power coefficient of 16/27 based on maximum system area. The Virtual Diffuser Wind Turbine (VDWT) system operates differently with, and without power extraction. With power extraction the VDWT system includes a high rotor thrust coefficient combined with an annular shroud system that uses bypass flow to form an annular, high-energy bypass flow stream that flows outward at the exit plane of the VDWT generating an observable virtual diffuser downstream therefrom. This outward, high-energy flow reduces exit plane pressure generating large wake expansions. The large wake expansion increases the flow rate through the rotor. Without rotor power extraction, separation takes place which reduces some of aerodynamic loads on the VDWT at extreme winds.

1 . A fluid turbine system comprising:
 a plurality of blades mounted to a rotor assembly, the rotor assembly having an operating thrust coefficient sufficient to create a flow region downstream of the rotor assembly that has a significantly lower energy level than a primary fluid flow;   a first annular duct having an annular leading edge, an annular trailing edge, an inner surface extending between the leading edge and the trailing edge, an outer surface extending between the leading edge and the trailing edge and a central axis, the inner surface of the annular duct in fluid communication with the plurality of blades;   a second annular duct having a leading edge, a trailing edge, an inner surface extending between the leading edge and the trailing edge, an outer surface extending between the leading edge and the trailing edge, and a central axis, the inner surface of the second annular duct in fluid communication with the outer surface of the first annular duct;   a Coanda nozzle formed between the outer surface of the first annular duct in proximity to the leading edge of the second annular duct and the inner surface of the second annular duct in proximity to the leading edge of the second annular duct, the Coanda nozzle capable of forming a high-energy bypass fluid flow stream between the outer surface of the first annular duct and the inner surface of the second annular duct that flows along the inner surface of the second annular duct when power is extracted from the primary fluid flow by the rotor assembly, the high-energy bypass fluid flow stream flowing outwardly from the turbine system exit plane forming an observable aerodynamic virtual diffuser downstream of the exit plane of the second annular duct.   
     
     
         2 . The fluid turbine system of  claim 1 , wherein the high energy bypass flow lowers the turbine exit plane pressure allowing a wake region to expand downstream of the exit plane of the second annular shroud to a diameter greater than the outer diameter of the trailing edge of the second annular duct. 
     
     
         3 . The fluid turbine system of  claim 2 , wherein the wake region bounded by the observable aerodynamic virtual diffuser increases the volume flow rate of the primary fluid flow passing through a rotor plane of the rotor assembly. 
     
     
         4 . The fluid turbine system of  claim 3 , wherein the observable aerodynamic virtual diffuser and the volume flow rate of the primary fluid flow passing through the rotor plane increases the turbine power coefficient. 
     
     
         5 . The fluid turbine system of  claim 1 , wherein the fluid turbine system includes a first operational mode and a second operational mode. 
     
     
         6 . The fluid turbine system of  claim 5 , wherein the first operational mode occurs with power extraction when high-energy bypass flow attaches and follows the inner surface of the second duct to the exit plane and beyond during full power generation, and
 the second operational mode occurs when no power is extracted and any bypass flow is at the same energy level as the rotor flow resulting in boundary layer separation occurring from the inner surface of one or both of the annular ducts.   
     
     
         7 . The fluid turbine system of  claim 1 , wherein the Coanda nozzle extends circumferentially about the outer surface of the first annular surface. 
     
     
         8 . The fluid turbine system of  claim 1 , wherein an annular gap between the first annular duct and the second annular duct forms the Coanda nozzle. 
     
     
         9 . The fluid turbine system of  claim 1 , wherein the Coanda nozzle has a height of between 5% and 25% of a length of the second annular duct from the leading edge to the trailing edge along the central axis. 
     
     
         10 . The fluid turbine system of  claim 1 , wherein the rotor assembly provides a thrust coefficient of between 0.89 and 1.0 when operational. 
     
     
         11 . The fluid turbine system of  claim 1 , wherein the observable aerodynamic virtual diffuser expands a wake expansion area downstream of the exit plane of the second annular duct to an area size greater than twice an exit area defined by an outer diameter of the second annular shroud. 
     
     
         12 . The fluid turbine system of  claim 2 , wherein the rotor assembly and the expanded wake area results in a power coefficient greater than 16/27 of kinetic energy of the flow region. 
     
     
         12 . The fluid turbine of  claim 1 , wherein the central axis of the first annular duct and the central axis of the second annular duct central axis are coaxial. 
     
     
         13 . The fluid turbine of  claim 1 , wherein the inner surface on the second annular duct turns outwardly at an angle between 20 and 60 degrees with respect to the central axis. 
     
     
         14 . The fluid turbine of  claim 1 , wherein the first annular duct has a length that is 30% to 70% shorter than the second ejector annular duct. 
     
     
         15 . The fluid turbine of  claim 1 , wherein the first and second annular ducts are formed of movable faceted segments positionable to reduce diffusion. 
     
     
         16 . The fluid turbine of  claim 15 , wherein the first and second annular ducts are formed of movable faceted segments positionable to reduce aerodynamic load on the fluid turbine. 
     
     
         17 . The fluid turbine of  claim 1 , wherein the second annular duct is formed of movable faceted circumferential segments that may be actuated perpendicular to the central axis to reduce duct diffusion. 
     
     
         18 . The fluid turbine of  claim 17 , wherein the second annular duct is formed of movable faceted circumferential segments that may be actuated perpendicular to the central axis to reduce wind drag on the fluid turbine. 
     
     
         19 . The fluid turbine of  claim 15 , wherein the movable faceted segments may be passively actuated or may be mechanically or pneumatically actuated. 
     
     
         20 . The fluid turbine of  claim 1 , wherein the high-energy bypass fluid flow stream flows outwardly from the second annular duct at an angle of between about 20° and about 60° relative to the central axis. 
     
     
         21 . A method of increasing energy extraction from a fluid stream, comprising:
 forming a high-energy bypass flow between an annular gap formed between an outer surface of a first annular duct and an inner surface of a second annular duct downstream of the first annular duct,   forming an observable aerodynamic virtual diffuser from the high-energy bypass flow downstream of an exit plane of the second annular duct,   forming with the low exit plane pressure provided from the high-energy bypass flow a wake area larger than an area defined by an exit plane of the second annular duct, and   extracting energy from the flow stream with a rotor assembly having a thrust coefficient of between 0.89 and 1.0.   
     
     
         22 . A ducted fluid turbine comprising:
 a first annular ducted shroud,   a second annular ducted shroud disposed downstream of the first annular ducted shroud,   an annular gap formed between a top trailing edge surface of the first annular shroud and a leading edge of the second annular shroud, the annular gap having a height sufficient to form a fluid jet along an inner surface of the second annular shroud to form an observable aerodynamic virtual diffuser downstream of an exit plane of the second annular shroud, and   a rotor assembly disposed in the first annular shroud having a thrust coefficient of between 0.89 and 1.0.   
     
     
         23 . The ducted fluid turbine of  claim 22 , wherein the high energy bypass flow lowers the turbine exit plane pressure allowing the wake to expand downstream of the exit plane of the second annular shroud to a diameter greater than the outer diameter of the trailing edge of the second annular duct. 
     
     
         24 . The ducted fluid turbine of  claim 23 , wherein the wake region bounded by an observable aerodynamic virtual diffuser increases the volume flow rate of the primary fluid flow passing through a rotor plane of the rotor assembly. 
     
     
         25 . The ducted fluid turbine of  claim 24 , wherein the observable aerodynamic virtual diffuser and the volume flow rate of the primary fluid flow passing through the rotor plane increases the turbine power coefficient. 
     
     
         26 . The ducted fluid turbine of  claim 22 , wherein the ducted fluid turbine includes a first operational mode and a second operational mode. 
     
     
         27 . The ducted fluid turbine of  claim 26 , wherein the first operational mode occurs with power extraction when high-energy bypass flow attaches and follows the inner surface of the second shroud to the exit plane and beyond during full power generation, and
 the second operational mode occurs when no power is extracted and any bypass flow is at the same energy level as the rotor flow resulting in boundary layer separation occurring from the inner surface of one or both of the annular ducts.   
     
     
         28 . The ducted fluid turbine of  claim 22 , wherein the annular gap forms a Coanda nozzle. 
     
     
         29 . The ducted fluid turbine of  claim 28 , wherein the Coanda nozzle has a height of between 5% and 25% of a length of the second shroud from the leading edge to the trailing edge along a central axis of the second shroud. 
     
     
         30 . The ducted fluid turbine of  claim 22 , wherein the rotor assembly and the expanded wake area results in a power coefficient greater than 16/27 of kinetic energy of fluid flowing through the first shroud. 
     
     
         31 . The ducted fluid turbine of  claim 22 , wherein a central axis of the first shroud and a central axis of the second shroud are coaxial. 
     
     
         32 . The ducted fluid turbine of  claim 22 , wherein an inner surface on the second shroud turns outwardly at an angle between 20 and 60 degrees with respect to a central axis. 
     
     
         33 . The ducted fluid turbine of  claim 22 , wherein the first shroud has a length that is 30% to 70% shorter than a length of the second shroud along a central axis. 
     
     
         34 . The ducted fluid turbine of  claim 22 , wherein the first and second shrouds are formed of movable faceted segments positionable to reduce diffusion. 
     
     
         35 . The ducted fluid turbine of  claim 34 , wherein the first and second shrouds are formed of movable faceted segments positionable to reduce aerodynamic load on the fluid turbine. 
     
     
         36 . The ducted fluid turbine of  claim 22 , wherein the second shroud is formed of movable faceted circumferential segments that may be actuated perpendicular to a central axis to reduce duct diffusion. 
     
     
         37 . The ducted fluid turbine of  claim 36 , wherein the second shroud is formed of movable faceted circumferential segments that may be actuated perpendicular to a central axis to reduce wind drag on the fluid turbine. 
     
     
         38 . The ducted fluid turbine of  claim 34 , wherein the movable faceted segments may be passively actuated or may be mechanically or pneumatically actuated. 
     
     
         39 . The ducted fluid turbine of  claim 22  further comprising,
 a third annular ducted shroud disposed downstream of the second annular ducted shroud. 
 
     
     
         40 . The ducted fluid turbine of  claim 39  further comprising,
 another annular gap formed between a top trailing edge surface of the second annular shroud and a leading edge of the third annular shroud, the annular gap having a height sufficient to form another fluid jet along an inner surface of the third annular shroud to form another observable aerodynamic virtual diffuser downstream of an exit plane of the third annular shroud.