U.S. patent application number 12/983066 was filed with the patent office on 2011-06-09 for fluid turbine with ejector shroud.
Invention is credited to Walter M. Presz, JR., Michael J. Werle.
Application Number | 20110135460 12/983066 |
Document ID | / |
Family ID | 44904095 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110135460 |
Kind Code |
A1 |
Presz, JR.; Walter M. ; et
al. |
June 9, 2011 |
FLUID TURBINE WITH EJECTOR SHROUD
Abstract
A fluid turbine comprises a turbine shroud and an ejector
shroud. The turbine shroud has an axial length L.sub.M. The ejector
shroud has an axial length L.sub.E. The ratio of L.sub.M to L.sub.E
is from 0.05 to 2.5. In particular embodiments, the ejector shroud
has an axial length L.sub.E, an outer diameter D.sub.I at the inlet
end, and an outer diameter D.sub.E at the exhaust end. The ratio of
L.sub.E to D.sub.I is from 0.05 to 3; and the ratio of L.sub.E to
D.sub.E is from 0.05 to 3. The resulting ejector shroud is 30%-50%
shorter than ejector shrouds of previous designs.
Inventors: |
Presz, JR.; Walter M.;
(Wilbraham, MA) ; Werle; Michael J.; (West
Hartford, CT) |
Family ID: |
44904095 |
Appl. No.: |
12/983066 |
Filed: |
December 31, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12054050 |
Mar 24, 2008 |
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12983066 |
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61332722 |
May 7, 2010 |
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61415592 |
Nov 19, 2010 |
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60919588 |
Mar 23, 2007 |
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Current U.S.
Class: |
415/208.2 |
Current CPC
Class: |
F03D 1/04 20130101; Y02E
10/72 20130101; F05B 2260/96 20130101; F05B 2240/13 20130101; F05B
2260/601 20130101; F05B 2240/133 20130101 |
Class at
Publication: |
415/208.2 |
International
Class: |
F04D 29/44 20060101
F04D029/44 |
Claims
1. A fluid turbine comprising a turbine shroud and an ejector
shroud; wherein the turbine shroud has a front end and a rear end;
wherein the ejector shroud has an inlet end and an exhaust end;
wherein the rear end of the turbine shroud comprises a plurality of
mixing lobes along a trailing edge, the mixing lobes extending into
the inlet end of the ejector shroud; wherein the turbine shroud has
an axial length L.sub.M; wherein the ejector shroud has an axial
length L.sub.E; and wherein the ratio of L.sub.M to L.sub.E is from
0.05 to 2.5.
2. The fluid turbine of claim 1, wherein the ratio of L.sub.M to
L.sub.E is from 0.16 to 2.1.
3. The fluid turbine of claim 1, wherein the ejector shroud has an
outer diameter D.sub.I at the inlet end, and the ratio of L.sub.E
to D.sub.I is from 0.05 to 3.0.
4. The fluid turbine of claim 1, wherein the ejector shroud has an
outer diameter D.sub.E at the exhaust end, and the ratio of L.sub.E
to D.sub.E is from 0.05 to 3.0.
5. The fluid turbine of claim 1, wherein the turbine shroud has an
outer diameter D.sub.F at the front end, and the ratio of L.sub.M
to D.sub.F is from 0.1 to 2.5.
6. The fluid turbine of claim 1, wherein the turbine shroud has an
outer diameter D.sub.RO at the rear end, and the ratio of L.sub.M
to D.sub.RO is from 0.1 to 1.25.
7. The fluid turbine of claim 1, wherein the turbine shroud has an
inner diameter D.sub.RI at the rear end, and the ratio of L.sub.M
to D.sub.RI is from 0.1 to 3.5.
8. The fluid turbine of claim 1, wherein the rear end of the
turbine shroud has an inner diameter D.sub.RI and an outer diameter
D.sub.RO, and the ratio of D.sub.RO to D.sub.RI is from 0.7 to
2.
9. The fluid turbine of claim 1, wherein the fluid turbine has a
total axial length L.sub.T, and the ratio of L.sub.M to L.sub.T is
from 0.05 to 1.0.
10. The fluid turbine of claim 1, wherein the fluid turbine has a
total axial length L.sub.T, and the ratio of L.sub.E to L.sub.T is
from 0.05 to 0.9.
11. The fluid turbine of claim 1, wherein the ejector shroud has a
ring airfoil shape and does not have mixing lobes.
12. The fluid turbine of claim 1, wherein the plurality of mixing
lobes includes a set of high energy mixing lobes and a set of low
energy mixing lobes, the high energy mixing lobes having an angle
of about 35.degree. to about 50.degree. relative to a longitudinal
axis of the turbine shroud.
13. A fluid turbine comprising a turbine shroud and an ejector
shroud; wherein the turbine shroud has a front end and a rear end;
wherein the ejector shroud has an inlet end and an exhaust end;
wherein the rear end of the turbine shroud comprises a plurality of
mixing lobes along a trailing edge, the mixing lobes extending into
the inlet end of the ejector shroud; wherein the turbine shroud has
an axial length L.sub.M; wherein the ejector shroud has an axial
length L.sub.E, an outer diameter D.sub.i at the inlet end, and an
outer diameter D.sub.E at the exhaust end; wherein the ratio of
L.sub.M to L.sub.E is from 0.05 to 2.5; wherein the ratio of
L.sub.E to D.sub.I is from 0.05 to 3; and wherein the ratio of
L.sub.E to D.sub.E is from 0.05 to 3.
Description
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/332,722, filed May 7, 2010 and to U.S.
Provisional Patent Application Ser. No. 61/415,592, filed Nov. 19,
2010. This application is also a continuation-in-part from U.S.
patent application Ser. No. 12/054,050, filed Mar. 24, 2008, which
claimed priority from 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.
BACKGROUND
[0002] The present disclosure relates to a shrouded fluid turbine
having a turbine shroud and an ejector shroud downstream of the
turbine shroud and surrounding the rear end of the turbine shroud.
It has been discovered that a shorter ejector shroud achieves
higher efficiency and lower weight compared to previous shrouded
wind turbines. The fluid turbines may be used to extract energy
from fluids such as air (i.e. wind) or water. The aerodynamic
principles of a mixer ejector wind turbine also apply to
hydrodynamic principles of a mixer ejector water turbine.
[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 that is
engaged with a power generator. HAWTs will not exceed 59.3%
efficiency in capturing the potential energy of the wind in the
blades swept area. 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 fluid turbines comprising
a turbine shroud and an ejector shroud. The turbine shroud has
mixing lobes along a trailing edge of the turbine shroud. The
turbine shroud has an axial length L.sub.M, the ejector shroud has
an axial length L.sub.E, and the ratio of L.sub.M to L.sub.E is
greater than in prior shrouded wind turbines.
[0005] Disclosed in some embodiments is a fluid turbine comprising
a turbine shroud and an ejector shroud. The turbine shroud has a
front end and a rear end. The ejector shroud has an inlet end and
an exhaust end. The rear end of the turbine shroud comprises a
plurality of mixing lobes along a trailing edge, the mixing lobes
extending into the inlet end of the ejector shroud. The turbine
shroud has an axial length L.sub.M. The ejector shroud has an axial
length L.sub.E. The ratio of L.sub.M to L.sub.E is from 0.05 to
2.5
( 0.05 .ltoreq. L M L E .ltoreq. 2.5 ) . ##EQU00001##
[0006] In more specific embodiments, the ratio of L.sub.M to
L.sub.E is from 0.16 to 2.1
( 0.16 .ltoreq. L M L E .ltoreq. 2.1 ) . ##EQU00002##
[0007] The ejector shroud has an outer diameter D.sub.I at the
inlet end, and the ratio of L.sub.E to D.sub.I may be from 0.05 to
3.0
( 0.05 .ltoreq. L E D i .ltoreq. 3.0 ) . ##EQU00003##
The ejector shroud has an outer diameter D.sub.E at the exhaust
end, and the ratio of L.sub.E to D.sub.E may be from 0.05 to
3.0
( 0.05 .ltoreq. L E D E .ltoreq. 3.0 ) . ##EQU00004##
[0008] The turbine shroud has an outer diameter D.sub.F at the
front end, and the ratio of L.sub.M to D.sub.F may be from 0.1 to
2.5
( 0.1 .ltoreq. L M D F .ltoreq. 2.5 ) . ##EQU00005##
The turbine shroud has an outer diameter D.sub.RO at the rear end,
and the ratio of L.sub.M to D.sub.RO may be from 0.1 to 1.25
( 0.1 .ltoreq. L M D RO .ltoreq. 1.25 ) . ##EQU00006##
The turbine shroud has an inner diameter D.sub.RI at the rear end,
and the ratio of L.sub.M to D.sub.RI may be from 0.1 to 3.5
( 0.1 .ltoreq. L M D RI .ltoreq. 3.5 ) . ##EQU00007##
The ratio of D.sub.RO to D.sub.RI may be from 0.7 to 2
( 0.7 .ltoreq. D RO D RI .ltoreq. 2 ) . ##EQU00008##
[0009] The wind turbine has a total axial length L.sub.T, and the
ratio of L.sub.M to L.sub.T may be from 0.05 to 1.0, including from
0.1 to 0.9
( 0.1 .ltoreq. L M L T .ltoreq. 0.9 ) . ##EQU00009##
The ratio of L.sub.E to L.sub.T may be from 0.05 to 0.9
( 0.05 .ltoreq. L E L T .ltoreq. 0.9 ) . ##EQU00010##
[0010] In some desired embodiments, the ejector shroud has a ring
airfoil shape and does not have mixing lobes. In other embodiments,
the ejector shroud has mixing lobes.
[0011] In embodiments, the plurality of mixing lobes on the turbine
shroud includes a set of high energy mixing lobes and a set of low
energy mixing lobes, the high energy mixing lobes having an angle
of about 10.degree. to about 50.degree. relative to a horizontal
axis that is parallel to the central axis of the turbine
shroud.
[0012] The fluid turbine may further comprise a nacelle body
located within the turbine shroud. The nacelle body, turbine
shroud, and ejector shroud are coaxial to each other. In some
embodiments, the nacelle body includes a central passageway.
[0013] Also disclosed is a fluid turbine comprising a turbine
shroud and an ejector shroud. The turbine shroud has a front end
and a rear end. The ejector shroud has an inlet end and an exhaust
end. The rear end of the turbine shroud comprises a plurality of
mixing lobes along a trailing edge, the mixing lobes extending into
the inlet end of the ejector shroud. The turbine shroud has an
axial length L.sub.M. The ejector shroud has an axial length
L.sub.E, an outer diameter D, at the inlet end, and an outer
diameter D.sub.E at the exhaust end. The ratio of L.sub.M to
L.sub.E is from 0.05 to 2.5; the ratio of L.sub.E to D.sub.i is
from 0.05 to 3; and the ratio of L.sub.E to D.sub.E is from 0.05 to
3
( 0.05 .ltoreq. L M L E .ltoreq. 2.5 ; 0.05 .ltoreq. L E D i
.ltoreq. 3 ; 0.05 .ltoreq. L E D E .ltoreq. 3 ) . ##EQU00011##
[0014] These and other non-limiting features or characteristics of
the present disclosure will be further described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] 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.
[0016] FIG. 1 is a cross-sectional view of a first exemplary
embodiment of a shrouded fluid turbine of the present disclosure,
marked with reference numerals.
[0017] FIG. 2 is a cross-sectional view of the shrouded fluid
turbine of FIG. 1, showing various lengths of the fluid
turbine.
[0018] FIG. 3 is a front left perspective view of the shrouded
fluid turbine of FIG. 1.
[0019] FIG. 4 is a rear right perspective view of the shrouded
fluid turbine of FIG. 1.
[0020] FIG. 5 is a front left perspective view of the shrouded
fluid turbine of FIG. 1 with the rotor and nacelle removed, so that
other aspects of the fluid turbine can be more clearly seen and
explained.
[0021] FIGS. 6A-6C are rear perspective cut-away views of the
shrouded fluid turbine of FIG. 1. The rotor and nacelle are removed
so that other aspects of the wind turbine can be more clearly seen
and explained. The cross-sectional area at the rotor of the turbine
shroud, the exit area of the turbine shroud, and the exit area of
the ejector shroud are illustrated here.
[0022] FIG. 7 is a rear view of the shrouded wind turbine of FIG.
1. The rotor and nacelle are removed from this figure so that other
aspects of the wind turbine can be more clearly seen and
explained.
[0023] FIG. 8 is a smaller view of the fluid turbine of FIG. 1.
[0024] FIG. 8A and FIG. 8B are magnified views of the mixing lobes
of the wind turbine of FIG. 8.
[0025] FIG. 9 is a cross-sectional view of a second exemplary
embodiment of a shrouded wind turbine of the present
disclosure.
[0026] FIG. 10 is a cross-sectional view of the shrouded fluid
turbine of FIG. 9, showing various lengths of the fluid
turbine.
[0027] FIG. 11 is a cross-sectional view comparing the first
exemplary embodiment of FIG. 1 with the second exemplary embodiment
of FIG. 9.
[0028] FIG. 12 is a chart showing the power output (kilowatts)
versus the wind velocity (mph), comparing a wind turbine with a
shorter ejector shroud (i.e. the turbine of FIG. 9) to a wind
turbine having a longer ejector shroud (i.e. the turbine of FIG.
1).
DETAILED DESCRIPTION
[0029] 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.
[0030] 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.
[0031] 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."
[0032] A Mixer-Ejector Fluid/Water Turbine (MEWT) provides an
improved means of generating power from fluid currents. A primary
shroud contains an impeller which extracts power from a primary
fluid stream. A mixer-ejector pump is included that ingests flow
from the primary fluid stream and secondary flow, and promotes
turbulent mixing of the two fluid streams. This enhances the power
system by increasing the amount of fluid flow through the system,
increasing the velocity at the rotor for more power availability,
and reducing back pressure on turbine blades. Additional benefits
include, among others, the reduction of noise propagating from the
system.
[0033] 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
(which may be part of a rotor/stator assembly). Any type of
impeller may be enclosed within the turbine shroud in the fluid
turbine of the present disclosure.
[0034] The leading edge of a turbine shroud may be considered the
front of the fluid turbine, and the trailing edge of an ejector
shroud 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.
[0035] The present disclosure relates to shrouded fluid turbines
having an ejector shroud downstream of a turbine shroud. The axial
length of the ejector shroud is much shorter than in prior
versions, which provides an unexpected increase in the efficiency
of the fluid turbine.
[0036] FIGS. 1-8 are various views of a first exemplary embodiment
of a shrouded fluid turbine of the present disclosure. Referring to
FIG. 1, the shrouded wind 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, also
known as an inlet end. The turbine shroud 110 also includes a rear
end 114, also known as an exhaust end. The ejector shroud 120
includes a front end or inlet end 122, and a rear end or exhaust
end 124. Support members 106 are shown connecting the turbine
shroud 110 to the ejector shroud 120.
[0037] The rotor 146 surrounds the nacelle body 150. Here, the
impeller 140 is a rotor/stator assembly comprising a stator 142 and
a rotor 146. The rotor 146 is downstream and co-axial with the
stator 142. The rotor 146 comprises a central hub 141 at the
proximal end of the rotor blades. The central hub 141 is
rotationally engaged with the nacelle body 150. The nacelle body
150 is connected to the turbine shroud 110 through the stator 142,
or by other aerodynamically neutral support structures. A central
passageway 152 extends through the nacelle body 150.
[0038] 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. The rear or
downstream end of the turbine shroud is shaped to form two
different sets of mixing lobes. 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. 4 and FIGS.
6A-6C.
[0039] A mixer-ejector pump (indicated by reference numeral 101,
FIG. 5) comprises an ejector shroud 120 surrounding the ring of
high energy mixing lobes 117 and low energy mixing lobes 119 on the
turbine shroud 110. The mixing lobes extend downstream and into an
inlet end 122 (see FIG. 1) of the ejector shroud 120. This
mixer-ejector pump provides the means for consistently exceeding
the operational efficiency of an open-bladed wind turbine of the
same rotor size.
[0040] Referring now to FIG. 1 and FIG. 2, the turbine shroud 110
has an axial length L.sub.M. The ejector shroud 120 has an axial
length L.sub.E. The entire turbine itself has an axial length
L.sub.T. The turbine shroud 110 has a throat diameter D.sub.F. This
throat diameter D.sub.F is measured as the smallest diameter of the
turbine shroud, and is generally located near the rotor 146. The
rear end 114 of the turbine shroud has an inner diameter D.sub.RI
and an outer diameter D.sub.RO. The inner diameter D.sub.RI is
measured as the diameter of a circle formed by the trailing edges
of the high energy mixing lobes 117. Similarly, the outer diameter
D.sub.RO is measured as the diameter of a circle formed by the
trailing edges of the low energy mixing lobes 119. It should be
recognized that generally D.sub.F>D.sub.RI,
D.sub.RO>D.sub.RI, and D.sub.RO>D.sub.F. These diameters are
also depicted in FIG. 7.
[0041] The ejector shroud 120 also has a throat diameter D.sub.I.
This throat diameter D.sub.I is measured as the smallest diameter
of the ejector shroud, and is generally located near the inlet end
122. The ejector shroud 120 also has an outer diameter D.sub.E at
the exhaust end 124. This outer diameter is measured as the
diameter of a circle formed by the trailing edge 128 of the ejector
shroud 120.
[0042] Due to the overlap of the turbine shroud and the ejector
shroud, L.sub.T>L.sub.M+L.sub.E. In embodiments, the ratio of
L.sub.M to L.sub.E is from 0.05 to 2.5, including from 0.16 to
2.1
( 0.05 .ltoreq. L M L E .ltoreq. 2.5 , including .16 .ltoreq. L M L
E .ltoreq. 2.1 ) . ##EQU00012##
The ratio of L.sub.M to L.sub.T may be from 0.1 to 1.0
( 0.1 .ltoreq. L M L T .ltoreq. 1.0 ) . ##EQU00013##
The ratio or L.sub.E to L.sub.T may be from 0.05 to 0.9
( 0.05 .ltoreq. L E L T .ltoreq. 0.9 ) . ##EQU00014##
The ratio of the ejector shroud length L.sub.E to throat diameter
D.sub.I may be from 0.05 to 3
( 0.05 .ltoreq. L E D i .ltoreq. 3 ) . ##EQU00015##
The ratio of the ejector shroud length L.sub.E to outer diameter
D.sub.E may be from 0.05 to 3
( 0.05 .ltoreq. L E D E .ltoreq. 3 ) . ##EQU00016##
[0043] The ratio of the turbine shroud length L.sub.M to throat
diameter D.sub.F may be from 0.1 to 2.5
( 0.1 .ltoreq. L M D F .ltoreq. 2.5 ) . ##EQU00017##
The ratio of the turbine shroud length L.sub.M to the rear end
outer diameter D.sub.RO may be from 0.1 to 1.25
( 0.1 .ltoreq. L M D RO .ltoreq. 1.25 . ) ##EQU00018##
The ratio of the turbine shroud length L.sub.M to the rear end
inner diameter D.sub.RI may be from 0.1 to 3.5
( 0.1 .ltoreq. L M D RI .ltoreq. 3.5 ) . ##EQU00019##
The ratio of D.sub.RO to D.sub.RI may be from 0.7 to 2
( 0.7 .ltoreq. D RO D RI .ltoreq. 2 ) . ##EQU00020##
The nacelle body 150 plug trailing edge included angle AN (FIG. 1)
will be thirty degrees or less. The length to diameter (L/D) of the
overall wind turbine, or in other words, the ratio of L.sub.T to
D.sub.E, will be from 0.05 to 3.0
( 0.05 .ltoreq. L T D E .ltoreq. 3.0 ) . ##EQU00021##
[0044] The turbine shroud's entrance area and exit area will be
equal to or greater than that of the annulus occupied by the rotor.
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.
[0045] Referring to FIG. 6A, the cross-sectional area of the throat
of the turbine shroud 110 is represented by the grid area 154.
Referring to FIG. 6B, the exit area of the turbine shroud at the
trailing edge 114 is represented by the grid area 156. Referring to
FIG. 6C, the exit area of the ejector shroud at the trailing edge
128 of the ejector shroud 120 is represented by grid area 158. The
area ratio of the ejector pump, as defined by the ejector shroud
exit area 158 over the turbine shroud exit area 156, will be in the
range of 1.25-3.0. The number of each type of mixing lobe (high
energy lobes or low energy lobes) can be between 6 and 28. The
height-to-width ratio of the lobe channels will be between 0.5 and
5.0. The mixing lobe penetration will be between 30% and 80%.
[0046] The turbine shroud 110 has a set of high energy mixing lobes
117 that extend inwards toward the central axis 105 of the turbine.
The turbine shroud also has a set of 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.
[0047] Referring to FIG. 7, 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 182 which each have the same radius of curvature.
Those inner arcuate portions 182 are evenly spaced apart from each
other. Between portions 182 are several outer arcuate portions 184,
which each have the same radius of curvature. The radius of
curvature for the inner arcuate portions 182 is different from the
radius of curvature for the outer arcuate portions 184, but the
inner arcuate portions and outer arcuate portions have the same
center (i.e. along the central axis 105). The inner arcuate
portions 182 and the outer arcuate portions 184 are then connected
to each other by radially extending portions 186. 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.
[0048] Referring now to FIG. 1, free stream fluid (indicated
generally by arrow 160, and which may be, for example, air 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 140 to be mixed with
the high energy fluid 162. The high energy fluid 162 enters the
ejector shroud 120. The ejector shroud camber creates a relatively
lower pressure on the inner surface of the ejector, in the
proximity of the leading edge 122, compared to the pressure on the
outside of the ejector shroud 120. The lower pressure on the
interior of the forward portion of the ejector shroud serves to
draw in additional fluid flow that is further mixed with the high
and low energy streams. An increase in pressure occurs on the
interior of the ejector shroud as the mixing flow moves from the
leading edge to the trailing edge of the ejector shroud. Put
another way, an increase in pressure occurs on the interior of the
ejector shroud as the flow moves from the upstream end of the
ejector shroud to the downstream end of the ejector shroud. Airflow
exiting the ejector shroud returns to ambient pressure. The ejector
shroud 120 has a ring airfoil shape and does not have mixing lobes.
In some embodiments, mixing lobes may also be formed on the
trailing edge 128 of the ejector shroud 120.
[0049] Referring now to FIG. 8A, a tangent line 171 is drawn along
the interior surface at the trailing edge of the high energy mixing
lobe 117. A rear plane 173 of the turbine shroud 110 is present.
The point where the tangent line 171 intersects the rear plane 173
is indicated here with reference numeral 172. A line 174 is formed
at point 172 parallel to the central axis 105. An angle O.sub.2 is
formed by the intersection of tangent line 171 and line 174. This
angle O.sub.2 is between 5 and 65 degrees. Put another way, a high
energy mixing lobe 117 forms an angle O.sub.2 between 5 and 65
degrees relative to a longitudinal axis that is parallel to the
central axis 105 of the turbine. In particular embodiments, the
angle O.sub.2 is from about 30.degree. to about 50.degree..
[0050] In FIG. 8B, a tangent line 176 is drawn along the interior
surface at the trailing edge of the low energy mixing lobe 119. The
point where the tangent line 176 intersects the rear plane 173 is
indicated here with reference numeral 179. A line 175 is formed at
point 179 parallel to the central axis 105. An angle O is formed by
the intersection of tangent line 176 and line 175. This angle O is
between 5 and 65 degrees. Put another way, a low energy mixing lobe
119 forms an angle O between 5 and 65 degrees relative to a
longitudinal axis that is parallel to the central axis 105 of the
turbine. In particular embodiments, the angle O is from about
20.degree. to about 45.degree..
[0051] Mixing lobes are present on the turbine shroud. As shown in
FIG. 3, the ejector shroud 120 has a ring airfoil shape and does
not have mixing lobes. If desired, though, mixing lobes may also be
formed on a trailing edge 128 of the ejector shroud.
[0052] Referring now to FIG. 9 and FIG. 10, cross-sectional views
of a second exemplary embodiment of the shrouded fluid turbine are
shown. Again, the wind turbine 200 comprises a turbine shroud 210
that has a front end 212 and a rear end 214. High energy mixing
lobes 217 and low energy mixing lobes 219 are present around the
rear end 214. The ejector shroud 220 has an inlet end 222 and an
exhaust end 224. Support members 206 connect the turbine shroud 210
to the ejector shroud 220. The turbine 200 further comprises,
similarly, an impeller 240, stator 242, rotor 246, and a nacelle
body 250. A central passageway 252 extends through the nacelle body
250.
[0053] The turbine shroud 210 has an axial length L.sub.M. The
ejector shroud 220 has an axial length L.sub.E2. The entire turbine
itself has an axial length L.sub.T2. The turbine shroud 210 has a
throat diameter D.sub.F. This throat diameter D.sub.F is measured
as the smallest diameter of the turbine shroud, and is generally
located near the rotor 246. The rear end 214 of the turbine shroud
has an inner diameter D.sub.RI and an outer diameter D.sub.RO. The
inner diameter D.sub.RI is measured as the diameter of a circle
formed by the high energy mixing lobes 217. Similarly, the outer
diameter D.sub.RO is measured as the diameter of a circle formed by
the low energy mixing lobes 219.
[0054] The ejector shroud 220 also has a throat diameter D.sub.I.
This throat diameter D.sub.I is measured as the smallest diameter
of the ejector shroud, and is generally located near the inlet end
222. The ejector shroud 220 also has an outer diameter D.sub.E at
the exhaust end 224. This outer diameter is measured as the
diameter of a circle formed by the trailing edge 228 of the ejector
shroud 220.
[0055] The notations L.sub.E2 and L.sub.T2 are used to indicate
that the lengths of the ejector shroud 220 and the overall turbine
200 differ from the lengths L.sub.E and L.sub.T shown in the
embodiment depicted in FIG. 1-5. The values for L.sub.M, D.sub.F,
D.sub.RI, D.sub.RO, D.sub.I, and D.sub.E are the same for both the
embodiments of FIG. 5 and FIG. 10. This notation relates to FIG. 11
and FIG. 12, as explained further below.
[0056] Comparative calculations were performed on the two
embodiments depicted in FIGS. 1-10. FIG. 11 and FIG. 12 show and
explain the results of the calculations.
[0057] FIG. 11 is a cross-sectional view comparing the first
exemplary embodiment of FIG. 1 with the second exemplary embodiment
of FIG. 9. The upper half is the embodiment shown in FIG. 1, and
the bottom half is the embodiment shown in FIG. 9. This is
indicated by the use of the different reference numerals to refer
to the turbine shroud (110, 220), the ejector shroud (120, 220),
and the nacelle body (150, 250).
[0058] For the comparative calculations, the throat diameter
D.sub.F was kept constant between both embodiments, as was the
ejector shroud outer diameter D.sub.E. The axial length L.sub.M was
also kept constant. In addition, the length of overlap between the
turbine shroud and the ejector shroud L.sub.ME was kept constant.
L.sub.E is greater than L.sub.E2.
[0059] FIG. 12 is a graph showing power output versus the wind
velocity for the two different turbines. The power output is
intended to show the relative amount of energy captured from the
wind stream passing through the turbine shroud. The relative values
in this graph were generated by data gathered in a wind tunnel. The
first set of values (squares) were generated from a wind turbine
having the relatively longer ejector shroud axial length L.sub.E.
The ratio of L.sub.E/D.sub.E was 0.32.
[0060] The second set of values (circles) were generated from a
wind turbine having the relatively shorter ejector shroud axial
length L.sub.E2. The ratio of L.sub.E2/D.sub.E was 0.12. As seen in
FIG. 12, a shorter ejector shroud generated more power at the same
wind velocity.
[0061] 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.
* * * * *