U.S. patent application number 15/558922 was filed with the patent office on 2018-03-15 for a rotor for an electricity generator.
This patent application is currently assigned to MAKO TURBINES PTY. LTD.. The applicant listed for this patent is MAKO TURBINES PTY. LTD.. Invention is credited to Peter John MURDOCH.
Application Number | 20180073367 15/558922 |
Document ID | / |
Family ID | 56918161 |
Filed Date | 2018-03-15 |
United States Patent
Application |
20180073367 |
Kind Code |
A1 |
MURDOCH; Peter John |
March 15, 2018 |
A ROTOR FOR AN ELECTRICITY GENERATOR
Abstract
A rotor (10) for a hydro-powered electricity generator. The
rotor (10) includes a hub (12) and a plurality of blades (16). The
hub (12) has a circular cross sectional shape and a longitudinal
rotational axis (14). The plurality of blades (16) each have a
proximal root (16a) and a distal tip (16b). Each of the blade roots
(16a) are mounted to the hub (12) at the widest part thereof (D1).
The ratio between the diameter of the tips (16b) of the blades to
the diameter of the widest part (D1) of the hub (12) is less than
about 2:1.
Inventors: |
MURDOCH; Peter John; (Duffys
Forest, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAKO TURBINES PTY. LTD. |
Alexandria |
|
AU |
|
|
Assignee: |
MAKO TURBINES PTY. LTD.
Alexandria
AU
|
Family ID: |
56918161 |
Appl. No.: |
15/558922 |
Filed: |
March 16, 2016 |
PCT Filed: |
March 16, 2016 |
PCT NO: |
PCT/AU2016/000091 |
371 Date: |
September 15, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05B 2250/00 20130101;
F01D 5/02 20130101; F03B 3/04 20130101; F03B 13/264 20130101; Y02E
10/30 20130101; Y02E 10/20 20130101; F05B 2220/32 20130101; F01D
5/147 20130101; F03B 13/10 20130101; F03B 17/061 20130101 |
International
Class: |
F01D 5/14 20060101
F01D005/14; F01D 5/02 20060101 F01D005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2015 |
AU |
2015900950 |
Claims
1. A rotor for a hydro-powered electricity generator, the rotor
including: a hub with a circular cross sectional shape and a
longitudinal rotational axis, a plurality of blades, each having a
proximal root and a distal tip, each of the blade roots being
mounted to the hub at the widest part thereof, wherein the ratio
between the diameter of the tips of the blades to the diameter of
the widest part of the hub is less than about 2:1.
2. The rotor as claimed in claim 1, wherein the ratio between the
diameter of the tips of the blades to the diameter of the widest
part of the hub is between about 1.2:1 and 2:1.
3. The rotor as claimed in claim 1, wherein the ratio between the
diameter of the tips of the blades to the diameter of the widest
part of the hub is about 1.5:1 or about 1.6:1.
4. The rotor as claimed in claim 1, wherein the diameter of the
tips of the blades is between 3.6 and 4.8 metres and the diameter
of the widest part of the hub is 2.4 metres.
5. The rotor as claimed in claim 1, wherein the diameter of the
tips of the blades is between 30 and 32 metres and the diameter of
the widest part of the hub is 20 metres.
6. The rotor as claimed in claim 1, wherein the profile radius of
the hub surface, in the region where each of the blade roots are
mounted to the hub, is between 1/6th of and equal to the radius of
the widest part of the hub.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a rotor for an electricity
generator.
[0002] The invention has been primarily developed for use in a
rotor for a hydro-powered electricity generator. Such generators
are used to convert kinetic energy from flowing fluids, such as
water and wind, to electrical power.
BACKGROUND OF THE INVENTION
[0003] Kinetic energy in flowing fluids, such as water and wind, is
a known alternative to energy sources such as bio-fuels and fossil
fuels for generating power. Unlike, for example, bio- and fossil
fuels which, when used in electrical power generation, go
hand-in-hand with emission of harmful combustion gasses into the
atmosphere, generation of power by using flowing fluids has no or
very little adverse effects on the atmosphere.
[0004] Known installations for harvesting wind power generally have
low running costs, however they tend to be expensive to install and
have relatively low generation capacity. Known installations for
harvesting hydropower, for example tidal power, on the other hand,
have relatively higher generation capacity.
[0005] Known hydro-powered electricity generators typically have a
rotor comprising a central hub to which is attached two or more
outwardly extending blades. The rotor is connected by a drive shaft
to a rotary work to electrical power converter (i.e. a generator).
Fluid flowing past the rotor blades causes it to rotate which in
turn causes the rotation in the converter and the generation of
electrical power.
[0006] Known rotors have a relatively small diameter hub and
relatively long and slender blades. The blades also have a
relatively high aspect ratio (being the ratio of the blade length
to the blade width). Such blades are prone to high operating loads
and subject to extreme bending moments in turbulent fluid flow.
This typically results in broken blades.
OBJECT OF THE INVENTION
[0007] It is an object of the present invention to substantially
overcome, or at least ameliorate, the above disadvantage.
SUMMARY OF THE INVENTION
[0008] In a first aspect, the present invention provides a rotor
for a hydro-powered electricity generator, the rotor including:
[0009] a hub with a circular cross sectional shape and a
longitudinal rotational axis, [0010] a plurality of blades, each
having a proximal root and a distal tip, each of the blade roots
being mounted to the hub at the widest part thereof, [0011] wherein
the ratio between the diameter of the tips of the blades to the
diameter of the widest part of the hub is less than about 2:1.
[0012] Preferably, the ratio between the diameter of the tips of
the blades to the diameter of the widest part of the hub is between
about 1.2:1 and 2:1.
[0013] Preferably, the ratio between the diameter of the tips of
the blades to the diameter of the widest part of the hub is about
1.5:1 or 1.6:1.
[0014] In one embodiment, the diameter of the tips of the blades is
between 3.6 and 4.8 metres and the diameter of the widest part of
the hub is 2.4 metres.
[0015] In another embodiment, the diameter of the tips of the
blades is between 30 and 32 metres and the diameter of the widest
part of the hub is 20 metres.
[0016] The profile radius of the hub surface, in the region where
each of the blade roots are mounted to the hub, is preferably
between 1/6th of and equal to the radius of the widest part of the
hub.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Preferred embodiments of the invention will now be
described, by way of examples only, with reference to the
accompanying drawings in which:
[0018] FIG. 1 is a front view of a first embodiment of a rotor;
[0019] FIG. 2 is a perspective view of the rotor shown in FIG. 1
with stream lines; and
[0020] FIG. 3 is cross sectional side view of a hydro-powered
electricity generator with a second embodiment of a rotor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] FIGS. 1 and 2 show a rotor 10 for a hydro-powered
electricity generator suitable for installation in a tidal flow
environment. The rotor 10 includes a hub 12 with a circular cross
sectional shape and a longitudinal rotational axis 14. The rotor 10
also includes 7 equiangularly spaced apart blades 16. The hub 10 is
formed from glass reinfornced plastic (GRP) or metal skins and the
blades 16 are formed from carbon fibre metal composites.
[0022] Each of the blades 16 has a proximal root 16a and distal tip
16b. Each of the blades 16 are mounted to the hub 14, at their
roots 16a, at the widest part of the hub 14. The diameter of the
widest part of the hub 14 is shown as diameter D1. The diameter of
the tips 16b of the blades 16 is shown as diameter D2. In the
embodiment shown, the ratio between diameters D2:D1 is about
1.4:1.
[0023] FIG. 2 shows the rotor 10 relative to fluid flow stream
lines 18 which demonstrate that as the fluid flows around the hub
12 its velocity increases. As the fluid accelerates and the local
velocity increases, the local pressure decreases. This pressure
reduction causes the fluid to remain concentrated around the hub
12. As a result, the energy in a free stream of the fluid is
concentrated in the region of the blades 16.
[0024] Another way of describing the above D2:D1 ratio is that the
diameter of the hub 12 is relatively large compared to the length
of the blades 16. The relatively large hub diameter D1
advantageously serves the dual function of: 1. concentrating the
energy in the passing water stream; and 2 supporting a relatively
greater number of smaller and stronger blades 16, which each have a
lower aspect ratio.
[0025] In relation to the latter issue, the bending moment at the
root is a function of the aspect ratio of the blade. For example, a
blade with an aspect ratio of 8:1 will have a stress value in the
root that is 16 times higher than the same blade with an aspect
ratio of 4:1. In a known 3-blade rotor with a relatively small
diameter hub, the blades can only have a limited chord length at
the root due to the diameter restriction of the hub. This
restriction of chord length means that the blade root thickness
must be increased, to provide sufficient strength, over that
otherwise required for an ideal foil section.
[0026] A relatively longer blade mounted to a relatively smaller
hub also results in a lower apparent velocity for a given RPM and a
lower torque radius.
[0027] A thicker root, especially in the lower 1/3.sup.rd of the
blade, combined with the lower apparent velocity and the lower
torque radius, results in a lowered contribution to the total power
of such a (known) 3-blade rotor. This is due to the fact that the
outer 1/3.sup.rd of the blade in the smaller hub/larger 3-blade
configuration does 63% of the work. This is a combination of the
swept area of the outer 30% of the blade, which constitutes 56% of
the total surface area, and the inner 30% of the blade producing
negligible power.
[0028] In contrast, the configuration of the rotor 10 (i.e.
relatively larger hub 14, relatively shorter blades 16, relatively
large number of blades 16) redirects and concentrates the fluid
flow in the inner 2/3 region and accelerates it through the outer
1/3.sup.rd region where 100% of the power can be extracted. This
advantageously means that the blades 16 are operating at maximum
capacity, while also experiencing a lower stress loading.
[0029] Put another way, the D2:D1 ratio of the rotor 10 places the
blades 16 in a zone of acceleration around the hub 12 with an ideal
blade length for the blades 16 to operate in that zone. If the
blades are too long relative to the hub diameter then the blades
tips instead operate in a region with no fluid acceleration and
therefore do not contribute positive torque.
[0030] FIG. 3 shows a hydro-powered electricity generator 30 with a
second embodiment of rotor 32. The rotor 32 has a hub 34 and ten
blades 36. FIG. 3 also shows blade root mounting beams 38, a blade
mounting hub 40, a fixed main spindle 42, a drive shaft 44, a gear
box 46, a support beam 48, a water seal 50, bearings 52 and a
rotary electrical generator 54. The beam 48 is used to connect the
generator 30 to a floating deployment rig (not shown).
[0031] Also shown on FIG. 3 is radius R, being the profile radius
hub 34 in the region where the hub 34 and the blades 36 are
connected. In the preferred configuration shown, the radius R is
1/6 the radius of the hub 34. This particular ratio maximises flow
acceleration while avoiding turbulence.
[0032] One preferred form of the generator 30 has the following
specifications:
[0033] Hub diameter D1: 2.4 meters
[0034] Blade tip diameter D2: 4.8 to 3.6 meters
[0035] Power generation range: 50 to 300 kWs
[0036] Flow velocity range: 1.2 to 4.2 m/sec
[0037] Blade tip diameter to hub diameter ratio: 2:1 to 1.5:1
[0038] Another preferred form of the generator 30 has the following
specifications:
[0039] Hub diameter D1: 20 meters
[0040] Blade tip diameter D2: 32 to 30 meters
[0041] Power generation range: 0.5 to 5 MWs
[0042] Flow velocity range: 1.2 to 4.0 m/sec
[0043] Blade tip diameter to hub diameter ratio: 1.6:1 to 1.5:1
[0044] There are several advantages for hydro-powered generators
due to the (relatively larger) diameter hub to (relatively smaller)
diameter blade ratios described above.
[0045] Firstly, the energy in the fluid stream is concentrated and
accelerated across a set of small blades, which improves the
efficiency of the rotor.
[0046] Secondly, the total volume of the multiple (e.g. 7) smaller
blades is less than the volume of a small number of (e.g. 3) large
blades, which lowers manufacturing cost.
[0047] Thirdly, the smaller blades have a lower aspect ratio, which
equates to a lower bending moment in the blade root, and a lower
probability of blade breakage.
[0048] Fourthly, the incident velocity and the incident angle of
the flow onto the smaller blades is closer to a uniform value
across the span of the blades. This equates to near zero twist in
the blade across its span, and allows the blades to be articulated
in pitch control without any performance losses induced by blade
twist. Further, the ability to adjust the pitch during operation
means the rotor can be run at a constant rpm independent of the
flow stream velocity. This allows the generator to be run at a
constant rpm connected directly to the electrical grid thereby
negating the cost of an electrical frequency inverter drive
system.
[0049] Fifthly, rotors operating in fast flowing tidal flows are
subject to high levels of turbulence in the stream. The action of
the flow acceleration of the water around the larger hub reduces
the level of turbulence into the blade region. This improves the
survivability of the blades in highly turbulence environments.
[0050] Although the invention has been described with reference to
preferred embodiments, it will be appreciated by person skilled in
the art that the invention may be embodied in other forms.
* * * * *