DIFFUSER-AUGMENTED WIND TURBINE

EOLIENNE A ACCROISSEMENT DE DIFFUSION

English Abstract

A diffuser-augmented wind-turbine assembly in which the diffuser has a
cylindrical central section rotatably supporting a rotor drum which in turn
supports turbine blades without requiring a central support shaft. Wind energy
drives the turbine blades and rotor drum, which in turn drive a generator of
electrical power.

French Abstract

La présente invention a trait à un ensemble d'éolienne à accroissement de diffusion dans lequel le diffuseur présente une section centrale de forme cylindrique de support rotatif d'un tambour de rotor qui à son tour assure le support des aubes d'éolienne sans nécessiter un arbre central de support. L'énergie éolienne entraîne les aubes d'éolienne et le tambour de rotor, qui à leur tour entraînent un générateur d'énergie électrique.

Claims

WHAT IS CLAIMED IS:
1. A diffuser-augmented wind-turbine assembly, the assembly having an diffuser
outer-housing shell with a cylindrical portion rotatably supporting a rotor
drum having an
inner surface rigidly supporting a plurality of turbine blades, the rotor drum
being in driving
engagement with a rotatable electrical generator.
2. The assembly of claim 1, wherein the rotor-drum inner surface is flush with
adjoining inner surfaces of the diffuser shell.
3. The assembly of claim 1, wherein the rotor drum and turbine blades are
integrally formed.
4. The assembly of claim 1, wherein the electrical generator comprises a
cylindrical magnet assembly secured to an outer surface of the rotor drum to
rotate therewith,
and a cylindrical stator-coil assembly secured to an inner surface of the
diffuser shell, and
extending around and slightly spaced from the magnet assembly.
5. The assembly of claim 1, and further comprising space-apart ring bearings
adjacent opposite ends of the rotor drum for rotatably supporting the drum
within the diffuser
shell.
6. The assembly of claim 1, and further comprising a plurality of inlet guide
vanes secured within an inlet end of the diffuser shell upstream of the
turbine blades.
7. The assembly of claim 1, wherein the electrical generator is drum shaped,
and
secured to the diffuser shell radially outwardly of the rotor drum, and
further comprising a
flexible belt engaged with the drum and generator.
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Description

CA 02590918 2007-06-15
WO 2006/065248 PCT/US2004/042620
1 DIFFUSER-AUGMENTED WIND TURBINE
BACKGROUND OF THE INVENTION
Wind turbines are in widespread use for the generation of electrical energy.
In a
typical form, a multi-blade turbine is rotatably mounted on a support such as
a pole or tower
to be driven by surface winds, the turbine in turn driving an electrical
generator coupled, for
example, to electrical utility lines. The turbine can be rotated about a
vertical axis of the pole
or tower to compensate for shifts in wind direction.
The use of diffusers with wind turbines is also known, the objective being to
increase
the efficiency of converting wind energy to electrical energy. Such known
diffusers are
typically mounted on the support tower, and a shaft-mounted turbine rotates
within the
diffuser. Such an arrangement is disclosed in U.S. Patent 4,075,500, which,
for brevity, is
incorporated herein by reference.
The improvement of this invention relates to integration of the turbine blades
with a
surrounding hollow cylindrical-shell rotor drum, the drum in turn being
rotatably supported
within a central part of the surrounding diffuser. A central hub and
supporting shaft for the
turbine blades is eliminated, and blade stiffness is significantly increased.
The blades and
rotor drum can be cast, or injection molded in a single manufacturing step.
SUMMARY OF THE INVENTION
A diffuser-augmented wind turbine for generating electrical power, and having
a
diffuser outer-housing shell with a cylindrical portion rotatably supporting a
rotor drum
having an inner surface rigidly supporting a plurality of turbine blades, the
rotor drum being
in driving engagement with a rotatable electrical generator. The device can
also be operated
in reverse as a wind-generating fan by supplying electrical energy to the
generator to act as a
motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a pole-mounted wind-turbine assembly according
to
the invention;
FIG. 2 is a front view of a blade and rotor-drum assembly;
FIG. 3 is a sectional side elevation of the turbine assembly;
FIG. 4 is an exploded perspective view of the turbine assembly shown in FIG.
3;
FIG. 5 is a view similar to FIG. 3, but showing a side-mounted belt-driven
electrical
generator; and
FIG. 6 is a perspective view of an embodiment using inlet guide vanes.
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CA 02590918 2007-06-15
WO 2006/065248 PCT/US2004/042620
1
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a diffuser-augmented wind-turbine assembly 10 according to the
invention, and rotatably mounted on a conventional support pole 11 so it can
be moved by a
fin 12 to compensate for shifting wind directions. The assembly has an outer
diffuser shell
15, within which can be seen a blade and rotor-drum assembly 16 as described
in greater
detail below.
FIG. 2 shows assembly 16 in greater detail, and as having an outer cylindrical
rotor
drum 18, with turbine blades 19 extending radially therein, and preferably
integrally formed
with the rotor drum. The assembly can be cast or of welded construction if
made of metal
(e.g., aluminum), or integrally injected molded if made from a composite
material
strengthened by glass, carbon, or similar reinforcing fibers. Though six
blades are shown, the
number of blades can be selected by the designer. Multiple blades, such as
five or six, are
preferred as they improve turbine efficiency, as well as increasing the
rigidity of assembly 16.
Turbine-blade strength and stiffness is significantly increased by the fixed
support of
the blades on the drum. The assembly is stable and balanced, and can be safely
operated at
high wind speeds encountered in storm conditions. For smaller wind-turbine
assemblies
which typically operate at high rotation speeds, centrifugal force
compressively loads the
blades, making them less prone to fatigue failure.
FIG. 3 is a sectional side elevation of one embodiment of assembly 10, and
shows
assembly 16 as rotatably mounted within diffuser shell 15. The diffuser shell
is preferably
molded from a strong composite material, and has an outwardly divergent
section 21 which
merges with outwardly stepped ring-shaped inner and outer cylindrical support
sections 22
and 23. An end portion 24 of the diffuser shell is separately formed, and is
rigidly secured to
a more forward part of the diffuser shell after the blade and rotor drum is
fitted therein. The
outlet end of the diffuser shell may be made more divergent to optimize
aerodynamic
conditions.
A pair of spaced-apart ring-shaped bearings 26 have outer races secured to the
inner
surface of support section 22, and inner races secured to the outer surface of
the rotor drum,
thereby rotatably mounting assembly 16 within the diffuser shell. The absence
of any
clearance between the blade tips and the rotor drum (which forms a cylindrical
part of the
diffuser) is another feature eliminating tip losses, and producing high
turbine efficiency.
Magnetic bearings can also be used to augment bearings 26 for lower friction
at high
rotational speeds
The embodiment shown in FIG. 3, and the exploded view of FIG. 4, positions the
components of an electrical generator assembly 28 cylindrically around the
rotor drum.
These components include a cylindrical assembly 29 of permanent magnets
secured to the
outer surface of the rotor drum to rotate therewith. Slightly outwardly spaced
from the
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CA 02590918 2007-06-15
WO 2006/065248 PCT/US2004/042620
1 magnet assembly is a cylindrical assembly 30 of stator coils secured to a
support ring 31
which is in turn rigidly secured to the inner surface of support section 23.
FIG. 5 shows an alternative embodiment using a conventional drum-shaped
electrical
generator 33 secured at one side of support section 23. Generator 33 is driven
by a flexible
timing belt 34 engaged with a toothed wheel on the generator, and extending
around a
cylindrically toothed section of the rotor drum.
FIG. 6 shows another alternative embodiment using an assembly 35 of stator
vanes or
inlet guide vanes secured within the inner end of outwardly divergent section
21 of the
diffuser shell. The use of such vanes is a known technique enabling use of
fixed-pitch
turbine blades, but with the advantages of more complex variable-pitch blades.
The diffuser
shell can also be lined with a sound-absorbing material for noise reduction
during turbine
operation.
Other applications on the wind-turbine assembly include "reverse" operation as
a
wind-generating fan, by applying electrical energy to the generator which then
acts as a
motor to rotate the blades. Another application involves adding blades to the
outside of the
rotor drum which is appropriately sealed to act as a wind-driven water pump,
air compressor,
or fan.
There has been described a wind-turbine assembly featuring a diffuser-
supported
assembly of turbine blades. The described designs are useful in both small and
large wind
turbines, are economical to manufacture, and operate at high efficiency.
30
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Representative Drawing