CA2816723A1

CA2816723A1 - Fluid turbines

Info

Publication number: CA2816723A1
Application number: CA2816723A
Authority: CA
Inventors: Walter M. Presz, Jr.; Michael J. Werle; Thomas J. Kennedy, Iii; William Scott Keeley
Original assignee: FloDesign Wind Turbine Corp
Current assignee: FloDesign Wind Turbine Corp
Priority date: 2010-11-19
Filing date: 2011-11-18
Publication date: 2012-05-24
Also published as: WO2012068466A1; AU2011329750A1; WO2012068466A8; EP2640967A1; US20110250053A1; CN103282650A

Abstract

Shrouded fluid turbines of various configurations are disclosed. The shrouded fluid turbines may an impeller, a turbine shroud surrounding the impeller, and an ejector shroud around the turbine shroud. The ejector shroud may substantially or completely surround the turbine shroud. The turbine shroud may have a plurality of mixing lobes that form a crenellated trailing edge. Alternatively, the turbine shroud may have a plurality of open slots. Means for directing fluid flow into the plurality of open slots may include an ejector shroud that seals with the turbine shroud downstream of the open slots. A plurality of fluid ducts may also connect individually to each open slot. An external stator may be connected to an exterior surface of the ejector shroud.

Description

FLUID TURBINES
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/415,626, filed Nov. 19, 2010, and U.S. Patent Application Serial No.
13/078,382, filed Apr. 1, 2011. This application relates to U.S. Patent Application Ser. No. 12/054,050, filed Mar. 24, 2008, and U.S. Provisional Patent Application Ser. No. 60/919,588, filed Mar. 23, 2007. The disclosures of these applications are hereby fully incorporated by reference in their entirety.
FIELD OF INVENTION

[0002] The present disclosure relates to shrouded fluid turbines having various configurations.
BACKGROUND

[0003] Conventional horizontal axis wind turbines (HAWTs) used for power generation have two to five open blades arranged like a propeller, the blades being mounted to a horizontal shaft attached to a gear box which drives a power generator. HAWTs will not exceed the Betz limit of 59.3% efficiency in capturing the potential energy of the wind passing through it. HAWTs are also heavy, requiring substantial support and increasing transport costs of the components.
It would be desirable to increase the efficiency of a fluid turbine by collecting additional energy from the fluid.
BRIEF DESCRIPTION

[0004] The present disclosure relates to shrouded fluid turbines of various configurations. The fluid turbines include an impeller, a turbine shroud, and an ejector shroud in various configurations. In some configurations, a plurality of fluid ducts is used in lieu of an ejector shroud. In others, an external stator extends radially from the ejector shroud.

[0005] The fluid turbines may be used as, for example, wind turbines or water turbines.

[0006] Disclosed in embodiments is a fluid turbine comprising: an impeller; a turbine shroud surrounding the impeller, the turbine shroud comprising a leading edge and a plurality of mixing lobes that form a crenellated trailing edge;
and an ejector shroud completely surrounding the turbine shroud, the ejector shroud comprising a leading edge and a trailing edge.

[0007] In some embodiments, the leading edge of the turbine shroud is coplanar with the leading edge of the ejector shroud. In others, the leading edge of the turbine shroud is downstream of the leading edge of the ejector shroud.

[0008] In particular versions, the leading edge of the turbine shroud has a substantially circular shape. In others, the leading edge of the ejector shroud has a substantially circular shape. The ejector shroud may have a ring airfoil shape.

[0009] The fluid turbine may further comprise a nacelle body, the impeller surrounding the nacelle body, the nacelle body having a trailing edge, wherein the nacelle body, turbine shroud, and ejector shroud are coaxial to each other.
The trailing edge of the nacelle body can be upstream or downstream of the trailing edge of the ejector shroud.

[0010] The impeller may be a rotor/stator assembly.

[0011] Also disclosed is a fluid turbine comprising: an impeller; a turbine shroud surrounding the impeller, the turbine shroud comprising a plurality of open slots downstream of the impeller; and an exterior structure for directing fluid flow from outside the turbine shroud through the plurality of open slots.

[0012] In some embodiments, the exterior structure for directing fluid flow is an ejector shroud disposed about the turbine shroud, the turbine shroud and the ejector shroud being sealed to each other downstream of the plurality of open slots.

[0013] In other embodiments, the exterior structure for directing fluid flow is a plurality of fluid ducts located along an exterior surface of the turbine shroud, each fluid duct comprising an inlet and an outlet, the outlet being connected to one of the opens slot in the turbine shroud.

[0014] Each fluid duct may further comprise a fluid duct impeller.

[0015] The inlets of the plurality of fluid ducts are downstream of an inlet end of the turbine shroud and are parallel to the inlet end of the turbine shroud.

[0016] Also disclosed is a fluid turbine comprising: an impeller; a turbine shroud surrounding the impeller; an ejector shroud downstream of the turbine shroud, a trailing edge of the turbine shroud extending into an inlet end of the ejector shroud; and a stator connected to an exterior surface of the ejector shroud.

[0017] In embodiments, the turbine shroud comprises a substantially circular leading edge and a plurality of mixing lobes that form a crenellated trailing edge.

[0018] The stator may have a ring airfoil shape. The ejector shroud may have a ring airfoil shape.

[0019] These and other non-limiting features or characteristics of the present disclosure will be further described below.
BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following is a brief description of the drawings, which are presented for the purposes of illustrating the disclosure set forth herein and not for the purposes of limiting the same.

[0021] FIG. 1 is a front left perspective view of a shrouded fluid turbine.

[0022] FIG. 2 is a rear right perspective view of the shrouded fluid turbine of FIG. 1.

[0023] FIG. 3 is a front perspective view of a first exemplary shrouded fluid turbine.

[0024] FIG. 4 is a first right side perspective cross-sectional view of the fluid turbine of FIG. 3.

[0025] FIG. 5 is a second right side perspective cross-sectional view of the fluid turbine of FIG. 3.

[0026] FIG. 6 is a side cross-sectional view of the fluid turbine of FIG.
3.

[0027] FIG. 7 is a front perspective view of a second exemplary shrouded fluid turbine.

[0028] FIG. 8 is a right side perspective cross-sectional view of the fluid turbine of FIG. 7.

[0029] FIG. 9 is a side cross-sectional view of the fluid turbine of FIG.
7.

[0030] FIG. 10 is a left front perspective view of a third exemplary shrouded fluid turbine.

[0031] FIG. 11 is a front view of the shrouded fluid turbine of FIG. 10.

[0032] FIG. 12 is a left cross-sectional view of the shrouded fluid turbine of FIG. 10.

[0033] FIG. 13 is a left front perspective view of a third exemplary shrouded fluid turbine, having fluid ducts.

[0034] FIG. 14 is a front view of the shrouded fluid turbine of FIG. 13.

[0035] FIG. 15 is a left cross-sectional view of the shrouded fluid turbine of FIG. 13. The nacelle body is removed so that aspects of the turbine shroud are visible.

[0036] FIG. 16 is a left front perspective view of a third exemplary shrouded fluid turbine, having impellers in the fluid ducts.

[0037] FIG. 17 is a front view of the shrouded fluid turbine of FIG. 16.

[0038] FIG. 18 is a left cross-sectional view of the shrouded fluid turbine of FIG. 16. The nacelle body is removed so that aspects of the turbine shroud are visible.

[0039] FIG. 19 is a perspective view of a shrouded fluid turbine with an external stator [0040] FIG. 20 is a cross-sectional view of the shrouded fluid turbine of FIG.

[0041] FIG. 21 is a smaller view of FIG. 20 [0042] FIG. 21A and FIG. 21B are magnified views of the mixing lobes of the fluid turbine of FIG. 21.

[0043] FIG. 22 is a rear view of the shrouded fluid turbine of FIG. 2.
The impeller is removed from this figure so that other aspects of the fluid turbine can be more clearly seen and explained.
DETAILED DESCRIPTION

[0044] A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying figures. These figures are intended to demonstrate the present disclosure and are not intended to show relative sizes and dimensions or to limit the scope of the exemplary embodiments.

[0045] Although specific terms are used in the following description, these terms are intended to refer only to particular structures in the drawings and are not intended to limit the scope of the present disclosure. It is to be understood that like numeric designations refer to components of like function.

[0046] The term "about" when used with a quantity includes the stated value and also has the meaning dictated by the context. For example, it includes at least the degree of error associated with the measurement of the particular quantity. When used in the context of a range, the term "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the range "from about 2 to about 4" also discloses the range "from 2 to 4."

[0047] A Mixer-Ejector Power System (MEPS) provides an improved means of generating power from wind currents. A primary shroud contains an impeller which extracts power from a primary wind stream. A mixer-ejector pump is included that ingests flow from the primary wind stream and secondary flow, and promotes turbulent mixing. This enhances the power system by increasing the amount of air flow through the system, reducing back pressure on turbine blades, and reducing noise propagating from the system.

[0048] The term "impeller" is used herein to refer to any assembly in which blades are attached to a shaft and able to rotate, allowing for the generation of power or energy from fluid rotating the blades. Exemplary impellers include a propeller or a rotor/stator assembly. Any type of impeller may be enclosed within the turbine shroud in the fluid turbine of the present disclosure.

[0049] The end of the fluid turbine wherein fluid enters to rotate the impeller may be considered the front of the fluid turbine, and the end of the fluid turbine where fluid exits after passing through the impeller may be considered the rear of the fluid turbine. A first component of the fluid turbine located closer to the front of the turbine may be considered "upstream" of a second component located closer to the rear of the turbine. Put another way, the second component is "downstream" of the first component.

[0050] The present disclosure relates to different configurations of a shrouded fluid turbine. The fluid turbines may be used as a wind turbine or a water turbine. FIG. 1 and FIG. 2 initially present some details of the shrouded fluid turbine which will help in discussing various aspects of the different configurations.

[0051] The shrouded fluid turbine 100 comprises an aerodynamically contoured turbine shroud 110, an aerodynamically contoured nacelle body 150, an impeller 140, and an aerodynamically contoured ejector shroud 120. Support members 106 connect the turbine shroud 110 to the ejector shroud 120. The impeller 140 surrounds the nacelle body 150. The nacelle body 150 is connected to the turbine shroud 110 through the impeller 140, or by other means.

[0052] The turbine shroud has the cross-sectional shape of an airfoil with the suction side (i.e. low pressure side) on the interior of the shroud. The rear end 114 of the turbine shroud also has mixing lobes 116. The mixing lobes extend downstream beyond the rotor blades. Put another way, the trailing edge 118 of the turbine shroud is formed from a plurality of mixing lobes 116. The rear or downstream end of the turbine shroud is shaped to form two different sets of mixing lobes 116. High energy mixing lobes 117 extend inwardly towards the central axis 105 of the mixer shroud. Low energy mixing lobes 119 extend outwardly away from the central axis 105. These mixing lobes are more easily seen in FIG. 2.

[0053] A mixer-ejector pump (indicated by reference numeral 101) comprises an ejector shroud 120 surrounding the ring of mixing lobes 116 on the turbine shroud 110. The mixing lobes 116 extend downstream and into an inlet end 122 of the ejector shroud 120. This mixer/ejector pump provides the means for consistently exceeding the Betz limit for operational efficiency of the fluid turbine.

[0054] In additional embodiments of the present disclosure, the ejector shroud completely surrounds the turbine shroud. Generally, the turbine shroud is located between the leading and trailing edges of the ejector shroud.

[0055] FIGS. 3-6 are different views of one exemplary embodiment where the ejector shroud completely surrounds the turbine shroud. Here, the shrouded fluid turbine 300 comprises an impeller 340 which surrounds a nacelle body 350.
The impeller is depicted here as a rotor/stator assembly. The nacelle body 350 has a trailing edge 352, which in this embodiment appears to be a tapered point.
The impeller 340 is surrounded by turbine shroud 310. Ejector shroud 320 in turn completely surrounds the turbine shroud 310. The leading edge 314 of the turbine shroud 310 has a substantially circular shape. The leading edge 324 of the ejector shroud 320 also has a substantially circular shape. The nacelle body 350, impeller 340, turbine shroud 310, and ejector shroud 320 are coaxial with each other, i.e. share a common axis.

[0056] As seen in FIG. 4 and FIG. 5, a plurality of mixing lobes 316 is present on the rear end of the turbine shroud, resulting in a crenellated trailing edge 318.

[0057] As seen in FIG. 6, the turbine shroud has a leading edge 314 and a trailing edge 318. Similarly, the ejector shroud has a leading edge 324 and a trailing edge 328. The leading edge 314 of the turbine shroud is coplanar with the leading edge 324 of the ejector shroud. In addition, the trailing edge 328 of the ejector shroud is downstream of the trailing edge 318 of the turbine shroud.
The trailing edge 318 of the turbine shroud is downstream of the impeller 340.

The ejector shroud 320 has a ring airfoil shape, i.e. has the cross-sectional shape of an airfoil with the suction side (i.e. low pressure side) on the interior of the ejector shroud.

[0058]
FIGS. 7-9 are different views of a second exemplary embodiment where the ejector shroud completely surrounds the turbine shroud. Here, the shrouded fluid turbine 400 comprises an impeller 440 which surrounds a nacelle body 450. The impeller is depicted here as a rotor/stator assembly. The nacelle body 450 has a trailing edge 452, which in this embodiment appears to be a tapered point. The impeller 440 is surrounded by turbine shroud 410. Ejector shroud 420 in turn completely surrounds the turbine shroud 410. The leading edge 414 of the turbine shroud 410 has a substantially circular shape. The leading edge 424 of the ejector shroud 420 also has a substantially circular shape. The nacelle body 450, impeller 440, turbine shroud 410, and ejector shroud 420 are coaxial with each other, i.e. share a common axis.

[0059] As seen in FIG. 8, a plurality of mixing lobes 416 is present on the rear end of the turbine shroud, resulting in a crenellated trailing edge 418.

[0060] As seen in FIG. 9, the turbine shroud has a leading edge 414 and a trailing edge 418. Similarly, the ejector shroud has a leading edge 424 and a trailing edge 428. The leading edge 414 of the turbine shroud is downstream of the leading edge 424 of the ejector shroud. In addition, the trailing edge 428 of the ejector shroud is downstream of the trailing edge 418 of the turbine shroud.
The trailing edge 418 of the turbine shroud is downstream of the impeller 440.

The ejector shroud 420 has a ring airfoil shape, i.e. has the cross-sectional shape of an airfoil with the suction side (i.e. low pressure side) on the interior of the ejector shroud.

[0061] It should be noted that in FIG. 6, the trailing edge 352 of the nacelle body 350 is upstream of the trailing edge 328 of the ejector shroud 320. In FIG.
9, the trailing edge 452 of the nacelle body 450 is downstream of the trailing edge 428 of the ejector shroud 420. The location of the trailing edge of the nacelle body may vary [0062] In other additional embodiments of the present disclosure, the fluid turbine includes a turbine shroud that comprises a plurality of open slots downstream of the impeller. An "open slot" allows fluid flowing along an exterior surface of the turbine shroud to pass radially from the exterior to the interior of the turbine shroud. The fluid turbine also includes an exterior structure which directs fluid flow from outside the turbine shroud through the plurality of open slots.

[0063] FIGS. 10-12 show different views of one exemplary embodiment of such a fluid turbine. The shrouded fluid turbine 500 comprises an impeller 540 which surrounds a nacelle body 550. The impeller is depicted here as a rotor/stator assembly. The nacelle body 550 has a trailing edge 552, which in this embodiment appears to be a tapered point. The impeller 540 is surrounded by turbine shroud 510. In this embodiment, ejector shroud 520 acts as the exterior structure for directing fluid flow. The leading edge 514 of the turbine shroud 510 has a substantially circular shape. The leading edge 524 of the ejector shroud 520 also has a substantially circular shape. The nacelle body 550, impeller 540, turbine shroud 510, and ejector shroud 520 are coaxial with each other, i.e. share a common axis.

[0064] As seen in FIG. 12, the turbine shroud 510 has a ring airfoil shape, with the suction side on the interior of the turbine shroud. A plurality of open slots 560 are located downstream of impeller 540. The open slots here are located along a trailing edge 504 of the fluid turbine. The turbine shroud 510 and ejector shroud 520 are sealed to each other downstream of the open slots 560.
Put another way, the fluid turbine has only one trailing edge, rather than the turbine shroud and ejector shroud having separate trailing edges, as seen for example in the embodiment of FIG. 2. High energy fluid 568 flowing along an exterior surface 517 of the turbine shroud 510 is directed by the ejector shroud 520 through the open slots 560.

[0065] As drawn in FIG. 12, the leading edge 514 of the turbine shroud is coplanar with the leading edge 524 of the ejector shroud. The leading edge 524 of the ejector shroud may be upstream of the leading edge 514 of the turbine shroud (see FIG. 9) or downstream of the leading edge of the turbine shroud (see FIG. 1), as desired. Similarly, the open slots 560 are shown as being located along the trailing edge 504 of the fluid turbine. This aspect is not required. Rather, the open slots 560 must be located downstream of impeller 540.
[0066] FIGS. 13-15 show different views of another exemplary embodiment of a fluid turbine with open slots. The shrouded fluid turbine 600 comprises an impeller 640 which surrounds a nacelle body 650. The impeller is depicted here as a rotor/stator assembly. The impeller 640 is surrounded by turbine shroud 610. The leading edge 614 of the turbine shroud 610 has a substantially circular shape. The nacelle body 650, impeller 640, and turbine shroud 610 are coaxial with each other, i.e. share a common axis.

[0067] As seen in FIG. 15, the turbine shroud 610 has a ring airfoil shape, with the suction side on the interior of the turbine shroud. A plurality of open slots 660 are located downstream of impeller 640. In contrast with the embodiment of FIG. 12, the open slots 660 here are separated from the trailing edge 604 of the turbine shroud. The open slots are seen here as having an elliptical shape, although in principle any shape may be used.

[0068] A plurality of fluid ducts 670 is located along the exterior surface 617 of the turbine shroud. Each fluid duct 670 comprises an inlet 672 and an outlet 674. The outlet 674 of a fluid duct is connected to an open slot 660 in the turbine shroud. The inlet 672 is downstream of the inlet end 611 of the turbine shroud, and is parallel to the inlet end as well.

[0069] FIGS. 16-18 show different views of another exemplary embodiment of a fluid turbine similar to that of FIGS. 13-15. This embodiment differs in that each fluid duct 670 has a fluid duct impeller 675. The fluid duct impeller 675 is powered, so that fluid is forced into the exhaust stream of the turbine shroud through the open slots 660.

[0070] FIG. 19 shows another configuration of a fluid turbine 800 similar to that of FIG. 1, but having an external stator. The shrouded fluid turbine 800 comprises an impeller 840 which surrounds a nacelle body 850. The impeller is depicted here as a rotor/stator assembly. Stator vanes 844 and rotor blades are visible. The impeller 840 is surrounded by turbine shroud 810. The turbine shroud has a plurality of mixing lobes 816 that form a crenellated trailing edge 818. The leading edge 814 of the turbine shroud 810 has a substantially circular shape.

[0071] An ejector shroud 820 is downstream of the turbine shroud 810. The mixing lobes 816 of the turbine shroud extend downstream and into an inlet end 822 of the ejector shroud 820. The leading edge 824 of the ejector shroud 820 also has a substantially circular shape. The nacelle body 850, impeller 840, turbine shroud 810, and ejector shroud 820 are coaxial with each other, i.e.
share a common axis. The ejector shroud 820 has a ring airfoil shape, i.e. has the cross-sectional shape of an airfoil with the suction side (i.e. low pressure side) on the interior of the ejector shroud.

[0072] A stator 880 is connected to an exterior surface 827 of the ejector shroud. The stator may also have a ring airfoil shape.

[0073] The turbine shroud and the ejector shroud may be formed to be lightweight. For example, they can be formed by covering a rigid frame or skeleton with a skin. The shrouds may comprise the same or different materials.
The material for the shroud skins may include polymeric films. Exemplary polymeric films include high density polyethylene (HDPE); polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polytrimethylene terephthalate (PTT); and polyurethane films. Both aliphatic and aromatic polyurethane along with polyether and polyester polyols may be utilized. Peroxide cured unsaturated polyester polymers in a glass matrix may also be used. The glass may be E or S glass. A composite matrix may also contain epoxy systems to improve the strength of the composite.

[0074] Other exemplary materials include polyvinyl chloride (PVC), polyurethane, polyfluoropolymers, and multi-layer films of similar composition.
Stretchable fabrics, such as spandex-type fabrics or polyurethane-polyurea copolymer containing fabrics, may also be employed.

[0075] Polyurethane films are tough and have good weatherability. The polyester-type polyurethane films tend to be more sensitive to hydrophilic degradation than polyether-type polyurethane films. Aliphatic versions of these polyurethane films are generally ultraviolet resistant as well.

[0076] Exemplary polyfluoropolymers include polyvinyldidene fluoride (PVDF) and polyvinyl fluoride (PVF). Commercial versions are available under the trade names KYNAR® and TEDLAR®. Polyfluoropolymers generally have very low surface energy, which allow their surface to remain somewhat free of dirt and debris, as well as shed ice more readily as compared to materials having a higher surface energy.

[0077] The skin may be reinforced with a reinforcing material. Examples of reinforcing materials include but are not limited to highly crystalline polyethylene fibers, paramid fibers, and polyaramides.

[0078] The skin may independently be multi-layer, comprising one, two, three, or more layers. Multi-layer constructions may add strength, water resistance, UV stability, and other functionality. However, multi-layer constructions may also be more expensive and add weight to the overall fluid turbine.

[0079] Film/fabric composites are also contemplated along with a backing, such as foam.

[0080] FIGS. 1-2 and FIGS. 20-22 illustrate various additional aspects of the different configurations of the shrouded fluid turbines of the present disclosure.
Again, the shrouded fluid turbine 100 comprises an aerodynamically contoured turbine shroud 110, an aerodynamically contoured nacelle body 150, an impeller 140, and an aerodynamically contoured ejector shroud 120. The turbine shroud 110 includes a front end 112 and a rear end 114. The ejector shroud 120 includes an inlet end 122 and an exhaust end 124. Support members 106 connect the turbine shroud 110 to the ejector shroud 120.

[0081] The impeller 140 surrounds the nacelle body 150. Here, the impeller is a rotor/stator assembly comprising a stator 142 having stator vanes 144 and a rotor 146 having rotor blades 148. The rotor 146 is downstream and "in-line"

with the stator vanes 144. Put another way, the leading edges of the rotor blades are substantially aligned with the trailing edges of the stator vanes.
The rotor blades are held together by an inner ring and an outer ring (not visible), and the rotor 146 is mounted on the nacelle body 150. The nacelle body 150 is connected to the turbine shroud 110 through the stator 142, or by other means.

In some embodiments, a central passageway 152 may also extend through the nacelle body 150.

[0082] The turbine shroud's entrance area and exit area will be equal to or greater than that of the annulus occupied by the impeller. The internal flow path cross-sectional area formed by the annulus between the nacelle body and the interior surface of the turbine shroud is aerodynamically shaped to have a minimum cross-sectional area at the plane of the turbine and to otherwise vary smoothly from their respective entrance planes to their exit planes. The ejector shroud entrance area is greater than the exit plane area of the turbine shroud.

[0083] Several optional features may be included in the shrouded fluid turbine. A power take-off, in the form of a wheel-like structure, can be mechanically linked at an outer rim of the impeller to a power generator.
Sound absorbing material can affixed to the inner surface of the shrouds, and to absorb and prevent propagation of the relatively high frequency sound waves produced by the turbine. The fluid turbine can also contain blade containment structures for added safety. The shrouds will have an aerodynamic contour in order to enhance the amount of flow into and through the system. The inlet and outlet areas of the shrouds may be non-circular in cross section such that shroud installation is easily accommodated by aligning the two shrouds. A swivel joint may be included on a lower outer surface of the turbine for mounting on a vertical stand/pylon, allowing the turbine to be turned into the fluid in order to maximize power extraction. Vertical aerodynamic stabilizer vanes may be mounted on the exterior of the shrouds to assist in keeping the turbine pointed into the fluid.

[0084] The area ratio of the ejector pump, as defined by the ejector shroud 120 exit area over the turbine shroud 110 exit area, will be in the range of 1.5-3Ø The number of mixing lobes can be between 6 and 28. The height-to-width ratio of the lobe channels will be between 0.5 and 4.5. The mixing lobe penetration will be between 50% and 80%. The nacelle body 150 plug trailing edge angles will be thirty degrees or less. The length to diameter (L/D) of the overall fluid turbine will be between 0.5 and 1.25.

[0085] Referring now to FIG. 22, the turbine shroud 110 has a set of nine high energy mixing lobes 117 that extend inwards toward the central axis 105 of the turbine. The turbine shroud also has a set of nine low energy mixing lobes 119 that extend outwards away from the central axis. The high energy mixing lobes alternate with the low energy mixing lobes around the trailing edge 118 of the turbine shroud. The impeller 140, turbine shroud 110, and ejector shroud 120 are coaxial with each other, i.e. they share a common central axis 105.

[0086] As seen in FIG. 2, the leading edge 112 of the turbine shroud 110 has a substantially circular shape. As seen in FIG. 22, the trailing edge 118 of the turbine shroud 110 has a circular crenellated shape. The trailing edge can be described as including several inner circumferentially spaced arcuate portions 181 which each have the same radius of curvature. Those inner arcuate portions 181 are evenly spaced apart from each other. Between portions are several outer arcuate portions 183, which each have the same radius of curvature. The radius of curvature for the inner arcuate portions 181 is different from the radius of curvature for the outer arcuate portions 183, but the inner arcuate portions and outer arcuate portions have the same center (i.e. along the central axis).

The inner arcuate portions 181 and the outer arcuate portions 183 are then connected to each other by radially extending portions 185. This results in a circular crenellated shape. The term "crenellated" as used herein does not require the inner arcuate portions, outer arcuate portions, and radially extending portions to be straight lines, but instead refers to the general up-and-down or in-and-out shape of the trailing edge. This crenellated structure forms two sets of mixing lobes, high energy mixing lobes 117 and low energy mixing lobes 119.

[0087] The outer arcuate portions 183 are located in an outer plane, which is indicated here with reference numeral 190. The inner arcuate portions 181 are located in an inner plane indicated here with reference numeral 192. As seen from this perspective, the outer plane 190 and inner plane 192 are generally cylindrical, with their axis being the central axis 105. The outer plane 190 and inner plane 192 are also coaxial.

[0088] The leading edge of the turbine shroud, indicated here as dotted circle 194, has a front radius of curvature 199. The outer radius of curvature 195 of the outer arcuate portions is greater than the inner radius of curvature 197 for the inner arcuate portions. The front radius of curvature 199 of the leading edge of the turbine shroud can be greater than, substantially equal to, or less than the outer radius of curvature 195.

[0089] Referring now to FIG. 20, free stream fluid (indicated generally by arrow 160, which may be, for example, wind or water) passing through the stator 142 has its energy extracted by the rotor 146. High energy fluid indicated by arrow 162 bypasses the turbine shroud 110 and stator 142, flows over the exterior of the turbine shroud 110, and is directed inwardly by the high energy mixing lobes 117. The low energy mixing lobes 119 cause the low energy fluid exiting downstream from the rotor 146 to be mixed with the high energy fluid 162.

[0090] Referring now to FIG. 21A, a tangent line 171 is drawn along the interior trailing edge indicated generally at 172 of the high energy mixing lobe 117. A rear plane 173 of the turbine shroud 110 is present. A line 174 is formed normal to the rear plane 173 and tangent to the point 171 where a low energy mixing lobe 119 and a high energy mixing lobe 117 meet. An angle 02 is formed by the intersection of tangent line 171 and line 174. This angle 02 is between and 65 . Put another way, a high energy mixing lobe 117 forms an angle 02 between 5 and 65 relative to a longitudinal axis of the turbine shroud 110.
In particular embodiments, the angle 02 is from about 35 to about 50 .

[0091] In FIG. 21B, a tangent line 176 is drawn along the interior trailing edge indicated generally at 177 of the low energy mixing lobe 119. An angle 0 is formed by the intersection of tangent line 176 and line 174. This angle 0 is between 5 and 65 . Put another way, a low energy mixing lobe 119 forms an angle 0 between 5 and 65 relative to a longitudinal axis of the turbine shroud 110. In particular embodiments, the angle 0 is from about 35 to about 50 .

[0092] Mixing lobes are present on the turbine shroud. If desired, though, mixing lobes may also be formed on a trailing edge 128 of the ejector shroud.

[0093] The present disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A fluid turbine comprising:
an impeller;
a turbine shroud surrounding the impeller, the turbine shroud comprising a leading edge and one or more mixing lobes , the trailing edge haying a first diameter; and an ejector shroud coaxial with the turbine shroud, the ejector shroud comprising a leading edge and a trailing edge, the leading edge haying a second diameter.

2. The fluid turbine of claim 1, wherein the leading edge of the turbine shroud is coplanar with the leading edge of the ejector shroud.

3. The fluid turbine of claim 1, wherein the leading edge of the turbine shroud is downstream of the leading edge of the ejector shroud.

4. The fluid turbine of claim 1, wherein the leading edge of the turbine shroud has a substantially circular shape.

5. The fluid turbine of claim 1, wherein the leading edge of the ejector shroud has a substantially circular shape.

6. The fluid turbine of claim 1, wherein the ejector shroud has a ring airfoil shape.

7. The fluid turbine of claim 1, further comprising a nacelle body, the impeller surrounding the nacelle body, the nacelle body haying a trailing edge, wherein the nacelle body, turbine shroud, and ejector shroud are coaxial to each other.

8. The fluid turbine of claim 7, wherein the trailing edge of the nacelle body is upstream of the trailing edge of the ejector shroud.

9. The fluid turbine of claim 7, wherein the trailing edge of the nacelle body is downstream of the trailing edge of the ejector shroud.

10. The fluid turbine of claim 1, wherein the impeller is a rotor/stator assembly.

11. A fluid turbine comprising:
an impeller;
a turbine shroud surrounding the impeller, the turbine shroud comprising one or more open slots downstream of the impeller; and an exterior structure for directing fluid flow from outside the turbine shroud through the plurality of open slots.

12. The fluid turbine of claim 11, wherein the exterior structure for directing fluid flow is an ejector shroud disposed about the turbine shroud, the turbine shroud and the ejector shroud being sealed to each other downstream of the plurality of open slots.

13. The fluid turbine of claim 11, wherein the exterior structure for directing fluid flow is a plurality of fluid ducts located along an exterior surface of the turbine shroud, each fluid duct comprising an inlet and an outlet, the outlet being connected to one of the opens slot in the turbine shroud.

14. The fluid turbine of claim 13, wherein each fluid duct further comprises a fluid duct impeller.

15. The fluid turbine of claim 13, wherein the inlets of the plurality of fluid ducts are downstream of an inlet end of the turbine shroud and are parallel to the inlet end of the turbine shroud.

16. The fluid turbine of claim 11, wherein a leading edge of the turbine shroud has a substantially circular shape.

17. A fluid turbine comprising:
an impeller;
a turbine shroud surrounding the impeller;
an ejector shroud downstream of the turbine shroud, a trailing edge of the turbine shroud extending into an inlet end of the ejector shroud; and a stator connected to an exterior surface of the ejector shroud.

18. The fluid turbine of claim 17, wherein the turbine shroud comprises a substantially circular leading edge and a plurality of mixing lobes that form a crenellated trailing edge.

19. The fluid turbine of claim 17, wherein the stator has a ring airfoil shape.

20. The fluid turbine of claim 17, wherein the ejector shroud has a ring airfoil shape.

21. A fluid turbine comprising:
an impeller;
a turbine shroud surrounding the impeller, the turbine shroud comprising a leading edge and one or more mixing lobes; and an ejector shroud substantially surrounding the turbine shroud, the ejector shroud comprising a leading edge and a trailing edge.