Note: Descriptions are shown in the official language in which they were submitted.
CA 02679562 2009-09-23
WIND TURBINE WITH MIXERS AND EJECTORS
RELATED APPLICATIONS
100011 This application is a second continuation-in-part application of a co-
pending
Utility Application, Serial Number 12/054,050, filed March 24, 2008
(hereinafter "Applicants'
Parent Application"), which claims priority from Applicants' U.S. Provisional
Patent
Application, Serial Number 60/919,588, filed March 23, 2007 (hereinafter
"Applicants'
Provisional Application"). Applicants hereby incorporate the disclosures of
Applicants' Parent
Application and Applicants' Provisional Application by reference in their
entireties.
FIELD OF INVENTION
[00021 The present invention deals generally with wind turbines. More
particuiarly, it
deals with apparatus for wind turbines.
BACKGROUND OF INVENTION
(0003] Wind turbines usually contain a propeller-like device, termed the
"rotor", which is
faced into a moving air stream. As the air hits the rotor, the air produces a
force on the rotor in
such a manner as to cause the rotor to rotate about its center. The rotor is
connected to either an
electricity generator or mechanical device through linkages such as gears,
belts, chains or other
means. Such turbines are used for generating electricity and powering
batteries. They are also
used to drive rotating pumps and/or moving machine parts. It is very coinmon
to find wind
turbines in large electricity generatinb "wind farms" containing multiple such
turbines in a
geometric pattern designed to allow maximum power extraction with minimal
impact of each
such turbine on one another and/or the surrounding environment.
100041 The ability of a--otor to convert tluid power to rotating power, when
placed in a
streain of very large width compared to its diameter, is limited by the well
documented
theoretical value of 59.3% of the oncoming streatn's power, known as the
"Betz" litnit as
docuniented by A. Betz in 1926. This productivity limit applies especially to
the traditionai
multi-bladed axial wind/water turbine presented in FIG. I A, labeled Prior
Art.
[00051 Attempts liave been made to try to increase wind turbine performance
potential
beyond the "Betz" limit. Shrouds or ducts surrounding the rotor liave been
used. See, e.g., U.S.
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CA 02679562 2009-09-23
Patent No. 7,218,011 to Hiel et al. (see FIG. IB); U.S. Patent No. 4,204,799
to de Geus (see FIG.
I C); U.S. Patent No. 4,075,500 to Oman et al. (see FIG. I D); and U.S. Patent
No, 6,887,031 to
Tocher. Properly designed shrouds cause the oncoming flow to speed up as it is
concentrated
into the center of the duct. In general, for a properly designed rotor, this
increased flow speed
causes more force on the rotor and subsequently higher levels of power
extraction. Often
though, the rotor blades break apart due to the shear and tensile forces
involved with higher
winds.
[0006] Values two times the Betz limit allegedly have been recorded but not
sustained.
See Igar, 0., Shrouds for Aerogenerators, AIAA Journal, October 1976, pp. 1481-
83; Igar &
Ozer, Research and Development for Shrouded Wind Turbines, Energy Cons. &
Management,
Vol. 21, pp. 13-48, 1981; and see the AIAA Technical Note, entitled "Ducted
Wind/Water
Turbines and Propellers Revisited", authored by Applicants ("Applicants' AIAA
Technical
Note"), and accepted for publication. Copies can be found in Applicants'
Information Disclosure
Statement. Such claims however have not been sustained in practice and
existing test results
have not confirmed the feasibility of such gains in real wind turbine
application.
100071 To achieve such increased power and efficiency, it is necessary to
closely
coordinate the aerodynamic designs of the shroud and rotor with the sometimes
highly variable
incoming fluid stream velocity levels. Such aerodynamic design considerations
also play a
significant role on the subsequent impact of flow turbines on their
surroundings, and the
productivity level of wind faiin designs.
100081 Ejectors are well known and documented fluid jet punips that draw flow
into a
system and thereby increase the flow rate through that system. Mixer/ejectors
are short compact
versions of such jet pumps that are relatively insensitive to incoming flow
conditions and have
been used extensively in high speed jet propulsion applications involvinb flow
velocities near or
above the speed of sound. See, for example, U.S. Patent No. 5,761,900 by Dr.
Walter M. Presz,
Jr, which also uses a mixer downstreain to increase thrust while reducing
noise from the
discharge, Dr, Presz is a co-inventor in the present application.
100091 Gas turbine technology has yet to be applied successfully to axial flow
wind
turbines. There are multiple reasons for this shoxtcotning. Existing wind
turbines commonly use
non-shrouded tui-bine blades to extract the wind energy. As a result, a
significant amount of the
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CA 02679562 2009-09-23
flow approaching the wind turbine blades flows around and not through the
blades. Also, the air
velocity decreases significantly as it approaches existing wind turbines. Both
of these effects
result in low flow through, turbine velocities. These low velocities minimize
the potential
benefits of gas turbine technology such as stator/rotor concepts. Previous
shrouded wind turbine
approaches have keyed on exit diffusers to increase turbine blade velocities.
Diffusers require
long lengths for good pertbnnance, and tend to be very sensitive to oncoming
flow variations.
Such long, flow sensitive difjusers are not practical in wind turbine
installations. Short diffusers
stall, and just do not work in real applications. Also, the downstream
diffusion needed inay not
be possible with the turbine energy extraction desired at the accelerated
velocities. These effects
have doomed all previous attempts at inore efficient wind turbines using gas
turbine technology.
100101 Accordingly, it is a primary object of the present invention to provide
an
iinproved apparatus that employs advanced tluid dynamic mixer/ejector pump
principles in a
wind turbine to consistently deliver sustainable levels of power well above
the Betz limit.
100111 It is another primary object to provide an improved method for an axial
flow wind
turbine that employs unique flow mixing (for wind turbines) to increase
productivity of and
minimize the impact of its attendant flow field on the surrounding environment
located in its
near vicinity, such as found in wind farms.
(0012) It is another primary object to provide an improved apparatus that
creates more
flow through an axial flow wind turbine's rotor and then rapidly mixes lower
energy exit flow
with higlier energy bypass wind flow before exiting the turbine.
100131 It is another primary object to provide an improved wind turbine that
employs
unique flow mixing (for wind turbines) and control devices to increase
productivity of and
minimize the impact of its attendant flow field on the surrounding environment
located in its
near vicinity, such as found in wind farms.
(0014) It is anotller primaiy object to provide an improved wind turbine that
pumps in
more air flow through the rotor and then rapidly mixes the low energy turbine
exit flow with
high energy bypass wind flow before exiting the system.
100151 It is a more specific object, cominensurate with the above-listed
objects, to
provide a method and apparatus which are relatively quiet and safe to use in
populated areas.
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CA 02679562 2009-09-23
SUMMARY OF INVENTION
100161 A method and apparatus are disclosed for improving the sustainable
efficiency of
wind turbines beyond the Betz limit. Both the method and apparatus use fluid
dynamic
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CA 02679562 2009-09-23
ejector concepts and advanced flow mixing to increase the operational
efficiency, wliile lowering
the noise level, of Applicant's unique wind turbine cotnpared to existing wind
turbines.
100171 Applicant's preferred apparatus is a mixer/ejector wind turbine
(nicknamed
"MEWT"). In the preferred "apparatus" embodiment, the MEWT is an axial flow
turbine
comprising, in order going downstream: a turbine shroud having a flared inlet;
a ring of stators
witllin the shroud; an impeller having a ring of impeller blades "in line"
with the stators; a mixer,
attached to the turbine shroud, having a ring of mixing lobes extending
downstream beyond the
impeller blades; and an ejector comprising the ring of mixing lobes (e.g.,
like that shown in U.S.
Patent No. 5,761,900) and a mixing shroud extending downstream beyond the
mixing lobes. The
turbine shroud, mixer and ejector are designed and ai-ranged to draw the
maximum amount of
fluid through the turbine and to minimize impact to the environment (e.g.,
noise) and other
power turbines in its wake (e.g., structural or productivity losses). Unlike
the prior art, the
preferred MEWT contains a shroud witli advanced flow mixing and control
devices such as
lobed or slotted mixers and/or one or more ejector pumps. The mixer/ejector
pump presented is
inuch different than used in the aircraft industry since the high energy air
flows into the ejector
inlets, and outwardly surrounds, pumps and mixes with the low energy air
exiting the turbine
shroud.
100181 In this first preferred "apparatus" embodiment, the MEWT broadly
comprises: an
axial flow wind turbine surrounded by a turbine sln-oud, with a flared inlet,
incorporating mixing
devices in its tenninus region (i.e., an end portion of the turbine shroud)
and a separate ejector
duct overlapping but aft of said turbine shroud, which itself may incorporate
advanced mixing
devices in its terniinus region.
10019] In an alternate "apparatus" embodiment, the MEWT comprises: an axial
flow
wind turbine sutTounded by an aerodynamically contoured turbine shroud
incorporating mixing
devices in its terniinus region.
[0020] In a broad sense, the preferrecl inethod coniprises: generating a level
of power
over the Betz limit for a wind turbine (preferably an axial tlow wind
turbine), of the type having
a turbine shroud with a flared inlet and an impeller downstream having a ring
of impeller blades,
by receiving and directing a priniary air stream of ajnbient air into a
turbine shroud; rotating the
impeller inside the shroud by the primary air stream, wliereby the primary air
sti-eam transfers
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CA 02679562 2009-09-23
energy to the impeller; and, entraining and mixing a secondary air stream of
ambient air
exclusively with the primary air strcaln, which has passed the impeller, via a
mixer and an
ejector sequentially downstream of the impeller.
[0021] An alternate method comprises: generating a level of power over the
Betz limit
for a wind -nill, having a turbine shroud with a flared inlet and an propeller-
like rotor
downstream, by entraining and mixing ambient air exclusively with lower energy
air, which has
passed through the turbine shroud and rotor, via a mixer and an ejector
sequentia3ly downstream
of the rotor.
100221 First-principles-based theoretical analysis of the preferred method and
apparatus
indicates that the MEWT can produce three or Inore times the power of its tin-
shrouded
counterparts for the same frontal area, and increase the productivity of wind
fanns by a factor of
two or more.
10023] Applicants believe, based upon their theoretical analysis, that the
preferred
method and apparatus will generate three times the existinl; power of the same
size conventional
wind turbine.
10024] Other objects and advantages of the curretit invention will become -
nore readily
apparent when the following written description is read in conjunction with
the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
100251 FIGS. 1 A, 1 B, 1 C, and ID, labeled "Prior Art", illustrate examples
of prior
turbines;
[0026] FIG. 2 is an exploded view of Applicants' preferred MEWT embodiment,
constructed in accordance with the present invention;
100271 FIG. 3 is a front perspective view of the preferred MEWT attached to a
support
tower;
[0028] FIG. 4 is a front perspective view of a preferred MEWT with portions
broken
away to show interior structure, such as a power takeoff in the form of a
wheel-like sti-ucture
attached to the impeller;
[0029] FIG. 5 is a front perspective view of just the stator, impeller, power
takeoff, and
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CA 02679562 2009-09-23
support shaft from FIG. 4;
[00301 FIG. 6 is an alternate embodinzent of the preferred MEWT with a
mixer/ejector
pump having mixer lobes on the terminus regions (i.e., an end portion) of the
ejector shroud;
[00311 FIG. 7 is a side cross-sectional view of the MEWT of FIG. 6;
(0032) FIG. 8 is a close-up of a rotatable coupling (encircled in FIG. 7), for
rotatably
attaching the MEWT to a support tower, and a mechanical rotatable stator blade
variation;
[00331 FIG. 9 is a front perspective view of an MEWT with a propeller-like
rotor;
(0034) FIG. 10 is a rear perspective view of the MEWT of FIG. 9;
[0035) FIG. 11 shows a rear plan view of the MEWT of FIG. 9;
100361 FIG. 12 is a cross-sectional view taken along sight line 12-12 of FIG.
11;
100371 FIG. 13 is a front plan view of the MEWT of FIG. 9;
)0038) FIG. 14 is a side cross-sectional view, taken along sight line 14-14 of
FIG. 13,
showing two pivotable blockers for flow control;
100391 FIG. 15 is a close-up of an encircted blocker in FIG. 14;
[0040) FIG. 16 illustrates an alternate embodiment of an MEWT with two
optional
pivoting wing-tabs for wind alignment;
100411 FIG. 17 is a side cross-sectional view of the MEWT of FIG 16;
[0042) FIG. 18 is a front plan view of an alternate embodiinent of the MEWT
incorporating a two-stage ejector with mixing devices (here, a ring of slots)
in the terminus
regions of the turbine shroud (here, mixing lobes) and the ejector shroud;
[0043) FIG. 19 is a side cross-sectional view of the MEWT of FIG. 18;
f0044) FIG. 20 is a rear view of the MEWT of FIG. 18;
100451 FIG. 21 is a front perspective view of the MEWT of FIG. 18;
100461 FIG. 22 is a front perspective view of an alternate embodiment of the
MEWT
incorporating a two-stage ejector with mixing lobes in the terminus regions of
the turbine shroud
and the ejector shroud;
[0047] FIG. 23 is a rear perspective view of the MEWT of FIG. 22;
100481 FIG. 24 shows optional acoustic lining within the turbine shroud of
FIG. 22;
10049) FIG. 25 shows a MEWT with a noncircular shroud component; and
[0050) FIG. 26 shows an aiternate embodiment of the preferred MEWT with mixer
lobes
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CA 02679562 2009-09-23
on the tenninus region (i.e., an end poi#ion) of the turbine shroud.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
100511 Referring to the drawings in detail, FIGS. 2-25 show alteraate
embodiments of
Applicants' apparatus, "Wind Turbines with Mixers and Ejectors" ("MEWT").
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CA 02679562 2009-09-23
[0052] In the preferred "apparatus" embodiment (see FIGS. 2, 3, 4 and 5), the
MEWT
100 is an axial flow wind turbine comprising:
a. an acrodynamically contoured tut-bine shroud 102;
b. an aerodynamically contoured center body 103 within and attached to the
turbine shroud 102;
C. a turbine stage 104, surrounding the cetiter body 103, comprising a stator
ring 106 of stator vanes (e.g., 108a) and an impeller or rotor 110 having
impeller or rotor
blades (e.g., 1 I2a) downstream and "in-line" with the stator vanes (i.e.,
leading edges of
the impeller blades are substantially aligned with trailing edges of the
stator vanes), in
which:
i, the stator vanes (e.g., 108a) are mounted on the center body 103;
and
ii. the impeller blades (e.g., l 12a) are attached and held together by
inner and outer rings or hoops mounted on the center body 103;
d, a mixer 118 having a ring of mixer lobes (e.g., 120a) on a terminus region
(i.e., end portion) of the turbine shroud 102, wherein the mixer lobes (e.g.,
120a) extend
downstream beyond the impeller blades (e.g., I I 2a); and
e. an ejector 122 comprising a shroud 128, surrounding the ring of mixer
lobes (e.g., 120a) on the turbine shroud, with a profile similar to the
ejector lobes shown
in U.S. Patent No. 5,761,900, wherein the mixer lobes (e.g., 120a) extend
downstreani
and into an inlet 129 of the ejector shroud 128.
10053J The center body 103 of MEWT 100, as shown in FIG. 7, is preferably
connected
to the turbine slu=oud 102 through the stator ring 106 (or other means) to
eliminate the dainaging,
annoying and long distance propagating low-frequency sound produced by
traditional wind
turbines as the turbine's blade wakes strike the support tower. The
aerodynamic profiles of the
turbine shroud 102 and ejector shroud 128 preferably are aerodynainically
cambered to increase
tlow through the turbine rotor.
[00541 Applicants llave calculated, for optimum efficiency in the preferred
embodiinent
100, the area ratio of the ejector pump 122, as defined by the ejector shroud
128 exit area over
the turbine shroud 102 exit area will be between 1.5 and 3Ø "1'he number of
mixer lobes (e.g.,
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CA 02679562 2009-09-23
120a) would be between 6 and 14. Each lobe will have inner and outer trailing
edge angles
between 5 and 25 degrees. The primary lobe exit location will be at, or near,
the entrance
location or inlet 129 of the ejector shroud 128. The height-to-width ratio of
the lobe channels
will be between 0.5 and 4.5. The inixer penetration will be between 50% and
80%. The center
body 103 plug trailing edge angles will be thirty degrees or less. The lengtll
to diaineter (L/D) of
the overall MEWT 100 will be between 0.5 and 1.25.
100551 First-principles-based theoreticai analysis of the preferred MEWT 100,
performed
by Applicants, indicate: the MEWT can produce three or more times the power of
its un-
shrouded counterparts for the same frontal area; and the MEWT can increase the
productivity of
wind farms by a factor of two or more. See Applicants' AIAA Technical Note,
identified in the
Background above, for the methodology and formulae used in their theoretical
analysis.
100561 Based on their theoretical analysis, Applicants believe their preferred
MEWT
einbodiment 100 will generate between at least two to three titnes the
existing power of the same
size conventional wind turbine (showii in FIG. 1 A). Applicant's combined
mixer and ejector
draw into an associated turbine rotor two or three times the volume of air
drawn into the rotors of
traditional wind mills.
100571 Traditional wind mills (a.k.a. wind turbines), with propeller-like
rotors (see FIG.
1), convert wind into rotational and then electrical power. Such rotors can
only displace,
theoretically, a maximum of 59.3% of the oncoming stream's power. That 59.3%
efficiency is
known as the "Betz" limit, as described in the Background of this application.
[00581 Since their preferred method and apparatus increase the volunle of air
displaced
by traditional wind turbines, with comparable frontal areas, by at least a
factor of two or three,
Applicants believe their preferred method and apparatus can sustain an
operational efficiency
beyond the Betz limit by a similar amount. Applicants believe their other
embodiments also will
exceed the Betz limit consistently, depending of course on sufficient winds.
100591 In siinplistic terms, the preferred "apparatus" embodimcnt 100 of the
MEWT
comprises: an axial tlow turbine (e.g., stator vanes and impeller blades)
suirounded by an
aerodynamically contoured turbine shroud 102 (i.e., a shroud with a flared
inlet) incorporating
mixing devices in its terminus region (i.e., end portion); and a separate
ejector shroud (e.g., 128)
overlapping, but aft, of turbine shroud 102, which itself may incorporate
advanced mixing
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CA 02679562 2009-09-23
devices (e.g., mixer lobes) in its tenninus rcgion. Applicants' ring 118 of
mixer lobes (e.g.,
120a) coinbined with the ejector shroud 128 can be thought of as a
mixer/ejector pump. This
mixer/ejector pump provides the means for consistently exceeding the Betz
limit for operational
efficiency of the wind turbine.
100601 Applicants have also presented supplemental inforniation for the
preferred
embodiment 100 of MEWT shown in FIGS, 2 and 3. It comprises a turbine stage
104 (i.e., with
a stator ring 106 and an irnpeller 110) mounted on center body 103, surrounded
by turbine
shroud 102 with embedded mixer lobes (e.g,, 120a) having trailing edges
inserted slightly in the
entrance plane of ejector shroud 128. '1'he turbine stage 104 and ejector
shroud 128 are
structurally connected to the turbine shroud 102, which itself is the
principal load carrying
member.
100611 The length of the turbine shroud 102 is equal or less than the turbine
shroud's
outer maximrnn diameter. The length of the ejector shroud 128 is equal to or
less than the
ejector shroud's outer maximum diaineter. The exterior surface of the center
body 103 is
aerodynamically contoured to minimize the effects of flow separation
downstream of the MEWT
100. It nlay be longer or shorter than the turbine shroud 102 or the ejector
shroud 128, or their
cornbined lengths.
100621 The turbine shroud's entrance area and exit area will be equal to or
greater than
that of the annulus occupied by the turbine stage 104, but need not be
circular in shape so as to
allow better control of the flow source and iinpact of its wake. The internal
flow path cross-
sectional area formed by the annulus between the center body 103 and the
interior surface of the
turbine shroud 102 is aerodynainically shaped to have a niinimum area at the
plane of the turbine
and to otherwise vary smoothly from their respective entrance planes to their
exit planes. The
turbine and ejector shrouds' extei-nal surfaces are aerodynamically shaped to
assist guiding the
tlow into the turbine shroud inlet, eliminating Ilow separation from their
surfaces, and delivering
smooth flow into the ejector entrance 129. The ejector 128 eritrance area,
which may be
noncircular in shape (see, e.g., FIG. 25), is larger than the mixer 118 exit
planc area and the
ejector's exit area niay also be noncircular in shape.
100631 Optional features of the preferred embodiment 100 can include: a power
take-off
130 (see FIGS. 4 and 5), in the form of a wheel-like structure, which is
meclianically linked at an
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outer rim of the impeller 110 to a power benerator (not shown); a vertical
support shaff, 132 with
a rotatable coupling at 134 (see FIG. 5), for rotatably supporting the MEWT
100, which is
located forward of the center-of-pressure location on the MEWT for self-
aligning the MEWT;
and a self-moving vertical stabilizer or "wing-tab" 136 (see FIG. 4), affixed
to upper and lower
surfaces of ejector shroud 128, to stabilize aligiment directions with
different wind streams.
10064J MEWT 100, when used near residences, can have sound absorbing material
affixed to the inner surface of its shrouds 102, 128 (see FIG. 24) to absorb
and thus virtually
eliminate the relatively high frequency sound waves produced by the
interaction of the stator 106
wakes with the impeller I 10. The METW can also contain safety blade
contairunent structure
(not shown).
10065J FIGS, 14 and 15 show optional flow blockage doors 140a, 140b. They can
be
rotated via linkage (not shown) into the flow stream to reduce or stop flow
through the turbine
100 when damage, to the generator or other components, due to high flow
velocity is possible.
100661 FIG. 8 presents another optional variation of Applicants` preferred
MEWT 100.
The stator vanes' exit-angle incidence is mechanically varied in situ (i.e.,
the vanes are pivoted)
to accommodate variations in the fluid streain velocity so as to assure
miniinum residual swirl in
the flow exiting the rotor.
[00671 Note that Applicants' alternate MEWT embodimeilts, sliown in FIGS. 9-23
and
26, each use a propeller-like rotor (e.g., 142 in FIG. 9) rather than a
turbine rotor with a ring of
impeller blades. While perhaps not as efficient, these embodiments may be more
acceptable to
the public.
1006$1 Applicants' alternate "apparatus" embodiments are variations 200, 300,
400, 500
containing zero (see, e.g., FIG. 26), one- and two-stage ejectors with mixers
embedded in the
terminus regions (i.e., end por-tions) of the ejector shrouds, if any. See,
e.g., FIGS. 18, 20 and 22
for mixers (e.g., nozzles or slots) embedded in the terminus regions of the
ejector shrouds.
Tertiary air streams (of ambient air), which have ilot entered previously
cither the turbine
shrouds or the ejectors, enter the mixers of the second-stage ejectors to mix
with, and transfer
energy to, the vortices of priniary and secondary air streams exiting the
terminus regions.
Analysis indicates such MEWT embodiments will inore quickly eliminate the
inherent velocity
defect occurring in the wake of existing wind turbines and thus reduce the
separation distance
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CA 02679562 2009-09-23
required in a wind farm to avoid structural damage and/or loss of
productivity.
[0069] FIG. 6 shows a"two-stage" ejector variation 600 of the pictured
embodiment 100
liaving a mixer at the terminus region of the ejector shroud.
[00701 The alternate "apparatus" embodiments 200, 300, 400, 500 in FIGS. 9-25
can be
thought of broadly as comprising:
a. a wind mill, or wind turbine, having a shroud with a flared inlet;
b, a propeller-like rotor dowtlstream of the inlet;
c. a mixer having a ring of mixer lobes which extend adjacent to and
dowiistream of the rotor; and
d. an ejector surrounding trailing edges of the mixer lobes and extending
downstreatn from the mixer lobes.
100711 Each of Applicant's illustrated wind turbine shrouds is adapted in size
and sliape
to produce a series of low loss mixing vortices, due to substantial non-
unifonnity of at least the
turbine shroud, downstream of the impeller (a.k.a. rotor), wheti the wind
turbine is exposed to a
wind moving in the downstream direction.
(0072] Each turbine shroud has a wall which varies substantially in thickness
along an
axis of rotation of the impeller. So do the ejectors.
(0073] Applicants believe that even without an ejector (e.g., see FIG. 26), a
mixer would
still increase the volume of air entering into and displaced by Applicants'
rotors, and hence
increase the efficiency over prior wind turbines (whether slirouded or not)
having comparable
frontal areas. The inci-ease, Ilowever, would be smaller than with asz
ejector.
100741 Each etnbodiment of Applicant's wind turbine has an "upstreain"
direction and a
"downstream" direction. By those tenns, Applicant is referring to the position
of each structural
part relative to the direction of the incoming wind, when the turbine inlet is
turtied substantially
into the wind.
100751 Applicant's invention can be thought of in tenns of inethods. In a
broad sense, the
preferred method comprises:
a. generating a level of power over the Betz limit for a wind turbine
(preferably an axial flow wind turbine), of the type having a turbine shroud
with a flared
inlet and an impeller downstrearn having a ring of impeller blades, by:
- 13 -
CA 02679562 2009-09-23
i. receiving and directing a primary air stream of ambient air into a
turbine shroud;
ii. rotating the impeller inside the shroud by the primary air stream,
whereby the primary air stream transfers energy to the impeller; and
iii. entraining and mixing a secondary air stream of ambient air
exclusively with the primary air stream, which has passed the impeller, via a
mixer and an ejector sequentially downstream of the impeller.
100761 An alternate method comprises:
a. generating a level of power over the Betz limit for a wind mill, having a
turbine shroud with a flared inlet and an propeller-like rotor downstream, by:
i. receiving and directing a primary air stream of ambient air into the
flared inlet and through the turbine shroud;
ii, rotating the impeller inside the shroud by the primary air stream,
whereby the primary air stream transfers energy to the rotor and becomes a
lower
energy air stream; and
iii. entraining and mixing a secondary stream of ambient air with the
lower energy air stream via a mixer and an ejector sequentially downstream of
the
rotor.
100771 Mixing the secondary air stream with the (lower energy) pritnary air
stream inside
the ejector; produces a series of niixing vortices due to substantial non-
uniformity of at least the
turbine sllroud downstream of the impeller; and creates a transfer of etlergy
from the secondary
air stream to the primary stream.
100781 Applicants' methods can also comprise:
a. directing the primary air stream, after rotating the impeller in the
turbine
shroud, away from a rotationaI axis of the impeller; and
b. directing the secondary air stream, after entering the ejector shroud,
towards the impeller rotational axis.
100791 While the preferTed rotational axis of the impeller is illustrated as
being coaxial
with a central longitudinal axis of the shroud, the impeller's rotational axis
need not be so for
purposes of this method.
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CA 02679562 2009-09-23
100801 Unlike gas turbine mixers and ejectors which also mix with hot core
exhaust
gases, Applicants' preferred method(s) entrain and mix a secondary stream of
ambient air (i.e.,
wind) exclaisivelv with lower energy air (i.e., a partially spent primary
stream of ambient air)
which has passed through a turbine shroud and rotor.
100811 Applicants believe that their preferred MEWT emboditnents 100, 200,
300, 400
and 600, and Applicants' preferred and alternate methods described directly
above, can
consistently sustain, witli sufticietit winds, operational efficiencies beyond
the Betz limit for
days, weeks and years without any significant damage to the tui-bine.
[0082) In other words, Applicants believe their preferred MEWT embodiments
100, 200,
300, 400, anci 600, and Applicants' prefe;red and alternate methods described
directly above, can
harness the power of the primary air stream to produce mechanical etlergy
while exceeding the
13etz limit for operational efficiency over a non-anomalous period.
[00831 Yet another broader, alternative method comprises:
a, increasing the volutne of air flowing through a wind mill, of the type
having a rotor, by:
i. entraining and mixing ambient air exclusively with lower energy
air, which has passed through the rotor, via a mixer adjacent to and
downstream
of the impeller.
[0084) This broader method can further include the steps of: increasing the
volume of
ambient air tlowing through the wind mill, while minimizing the noise level of
the discharge
flow froni the wind mill, by an ejector downstream of the mixer.
[00851 It should be understood by those skilled in the art that obvious
modifications can
be made without departing fi=om the spirit or scope of the invention. For
example, slots could be
used instead of the mixer lobes or the ejector lobes. In addition, no blocker
arm is needed to
meet or exceed the Betz limit. Accordingly, reference should be inade
primarily to the appended
claims rather than the foregoing description.
[0086] WE CLAIM:
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