Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HYDRAULIC TURBINE WITH INCREASED POWER CAPACITIES
FIELD OF THE INVENTION
The present invention relates to hydroelectric turbine
installations, and more particularly to a hydraulic turbine
with increased power capacities and a method of refurbishing
an existent hydraulic turbine to increase its power
capacities while being fish friendly.
BACKGROUND
Many existing hydroelectric installations are based on
Francis turbines, as illustrated in Figure 1. In these
classical installations, the runner wheel 2 turns in the
center of a spiral case 4. A stayring 6 with stay vanes 8 at
the outlet of the spiral case 4 guides the water to the
runner wheel 2. A radial distributor with wicket gates 10
behind the stay vanes 8 controls the water flow and
distributes the water evenly around the runner wheel 2. The
water passes through the runner wheel 2 and follows its
course in a draft tube 12.
Such types of installations are often not very fish
friendly due to the reduced dimensions of the water passage
through the turbine, the speed of the water flow, the water
pressure variations across the turbine, the shear in the
water flow, etc. The many parts of the turbine which stand in
the way, like the stay vanes, the wicket gates, possible
axial or radial distributors, and the runner wheel, form as
many hazards for the fish.
Existing methods of increasing the power of hydraulic
turbines generally consist of increasing the size of the
various parts of the installations, which requires more
space. Unless spare space is readily available, the power of
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the existing installations cannot be increased easily in this
way.
US patents Nos. 1,942,995 (BIGGS); 3,132,839 (HAEKAL);
3,305,215 (SWIECICKI et al.); 3,398,696 (SPROULE); 4,120,602
(MEGNINT); 4,146,351 (KOELLER); 4,242,289 (BLUM); 4,575,307
(SHINOHARA); 4,780,051 (FISHER, JR.); 4,867,636 (SAURON et
al.); 5,082,425 (REIL et al.); 5,261,787 (MORGUNOV);
5,441,384 (GOKHMAN); 5,471,965 (KAPICH); 5,823,740 (CYBULARZ
et al.); 5,879,130 (BEYER et al.); 5,924,842 (BEYER et al.);
5,924,844 (CYBULARZ et al.); 5,941,682 (CYBULARZ et al.);
5,997,242 (HECKER et al.); 6,036,434 (RAY et al.); 6,095,749
(BEYER et al.); 6,114,773 (KOURIS); 6,152,684 (FERME et al.);
6,155,783 (BEYER); 6,227,798 (DEMERS et al.); and 6,247,893
(BEYER et al.) provide examples of various other hydraulic
turbines and hydroelectric installations of the prior art.
SUMMARY
An object of the present invention is to provide a
hydraulic turbine with increased power capacities, which can
be used when refurbishing existing hydraulic turbines or in
ZO new hydroelectric installations.
Another object of the present invention is to provide
such a hydraulic turbine which retrofit in many existing
hydroelectric installations.
Another object of the present invention is to provide
such a hydraulic turbine which has a reduced =number of
blades, vanes and similar parts in the water passage in
comparison with classical turbines, and which is fish
friendly at least in this respect.
According to the present invention, there is provided a hydraulic turbine with
30 increased power capacities, comprising:
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an axial runner wheel having a rotation axis;
a runner ring peripherally extending around the runner wheel;
a draft tube extending on a downstream side of the runner ring;
a water supply port extending around the rotation axis of the runner wheel on
an upstream side of the runner ring, and adapted to produce a substantially
centripetal water flow swirling around the rotation axis of the runner wheel;
a turning passageway extending between the water supply port and the
runner ring, and adapted to guide and redirect the centripetal water flow in a
substantially axial direction of the runner wheel;
an axial distributor extending between the turning passageway and the
runner wheels; and
a bottom pit liner peripherally extending around the axial distributor and the
runner ring;
and wherein the water supply port comprises a stay ring next to the turning
passageway and a conical support ring attaching a lower part of the water
supply
port to the stay ring and to the bottom pit liner.
According to the present invention, there is also provided a method of
refurbishing an existent hydraulic turbine while increasing power capacities
thereof,
comprising:
removing any original radial distributor of the existent hydraulic turbine to
recover axial space under a water supply port of the hydraulic turbine;
replacing any original stay vanes and wicket gates of the existent hydraulic
turbine by new stay vanes having a greater height with respect to the original
stay
vanes, combined to a reshaping of the water supply port to accommodate the new
stay vanes;
using the recovered axial space to replace an original runner wheel with a
larger diameter axial runner wheel combined to a reshaping of a runner ring
peripherally extending around the axial runner wheel, the axial runner wheel
and
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the runner ring being moved downstream with respect to a level of the original
runner wheel;
inserting an axial distributor upstream of the axial runner wheel;
reshaping a head cover of the existent hydraulic turbine to form a turning
passageway between the water supply port and the axial runner wheel, adapted
to
redirect a centripetal water flow swirling in the water supply port around a
rotation
axis of the axial runner wheel in a substantially axial direction of the axial
runner
wheel; and
reshaping a draft tube on a downstream side of the runner wheel so that the
draft tube has an enlarged elbow section with respect to a narrower original
elbow
section.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of preferred embodiments will be
given herein below with reference to the following drawings,
in which like numbers refer to like elements:
Figure 1 is a cross-section view of a typical Francis
turbine installation.
Figure 2 is a cross-section view of a Kaplan turbine
installation according to the present invention.
Figure 3 is an enlarged cross-section view of a Kaplan
turbine according to the present invention.
Figure 4 is a cross-section view of a propeller turbine
installation according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 2, there is shown a hydraulic
turbine with increased power capacities according to the
present invention. The new turbine is intended to be used in
installations typically but not restrictively operating under
5 to 60 meters waterfalls with an optimum application zone of
around 30 meters.
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The replacement of a classical turbine by a turbine
according to the present invention will likely increase the
generated power from 50 to more than 100 % while retrofitting
in the former structure, thus reducing the required
installation works. In the case of a new electric power
plant, the turbine according to the present invention reduces
the required axial space (or inter-axial space of the groups
when several turbines are used).
In comparison with a classical turbine as shown in
Figure 1, the turbine according to the present invention
allows to increase the diameter of the runner wheel 2' while
keeping the same spiral case 4 and the same occupation space
in the hydroelectric installation. This increase of the
runner wheel's diameter can be achieved as a result of the
elimination of the radial distributor 10. Usually, as a
result, the rotation speed of the wheel 2' is reduced.
The main direction of the water flow through the turbine
is depicted by arrows.
In short, the hydraulic turbine according to the present
invention has an axial runner wheel 2' having a rotation axis
14. A runner ring 34 peripherally extends around the runner
wheel 2'. A draft tube 12' extends on a downstream side of
the runner ring 34. A water supply port 42 extends around the
rotation axis 14 of the runner wheel 2' on an upstream side
of the runner ring 34. The water supply port 42 is arranged
to produce a generally centripetal water flow swirling around
the rotation axis 14 of the runner wheel 2'. A turning
passageway 16 extends between the water supply port 42 and
the runner ring 34 to guide and redirect the centripetal
water flow in a substantially axial direction of the runner
wheel 2'. An axial distributor 18 extends between the turning
passageway 16 and the runner ring 34.
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The water supply port 42 can be conveniently provided
with a stayring 6' next to the turning passageway 16, and
extending above the axial distributor 18, contrary to the
stayring 6 in a typical Francis turbine as shown in Figure 1.
The stayring 6' typically has a number of stay vanes 8'
distributed around the rotation axis 14 of the runner wheel
2', near the turning passageway 16. The number of stay vanes
8' should be chosen according to the mechanical and hydraulic
requirements as explained hereinafter, and may be reduced to
zero in certain cases. As these requirements will often be
lower in the new turbine compared to classical turbine, the
number of stay vanes 8' will also often be reduced
accordingly, e.g. from 24 to 12.
Stay vanes 8' having a greater height than usual are
preferred in the new turbine, e.g. a height close to a
smallest diameter (or height) of the water supply port 42.
Referring to Figure 3, water is supplied through a
penstock (not shown in the Figures) communicating with the
spiral case 4. The spiral case 4 and the stay vanes 8' at the
water supply port 42 of the spiral case 4 cause the water
flow to swirl around the rotation axis 14 of the turbine and
to generate a centripetal vortex. The spiral case 4 could be
replaced by a water chamber (not shown in the Figures) or any
other suitable water supply structure if desired. The
swirling water produces a kinetic momentum. In the meridian
plane, the water flow is radial as depicted by the arrows
passing through the stayring 6', as shown in Figure 2. The
stay vanes 8' have mechanical and hydraulic functions. The
vanes 8' are subjected to the mechanical stress of the spiral
case 4, the surrounding concrete and the other mechanical
components which press against them. They are also used to
correct the direction of the water flow to make it uniform.
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However, the number of stay vanes 8' can be reduced to zero
in certain configurations.
The water flow follows its course by turning in the
meridian plane and exiting from the axial distributor 18 with
a direction almost parallel to the rotation axis 14 of the
runner wheel 2. The turning of the water flow before reaching
the axial distributor 18 is a particular feature of the new
turbine.
The axial distributor 18 can be made of a number of
adjustable guide vanes, for example 12 to 24, projecting
around the rotation axis 14 of the runner wheel 2'. Their
function is to control the flow between stopped and full load
operation states with a minimum of losses. It operates in a
different way from axial guide vanes of classical turbines by
the fact that a very significant kinetic momentum is already
initiated by the upstream components before the turn. The
axial guide vanes of classical turbines have a major
contribution in the generation of a vortex, which is not the
case here. The profile of the guide vanes is thus different
in the new turbine. The pitch of the guide vanes can be
horizontal or slightly slanted, ranging for example between 0
to 20 degrees or more with respect to a rotation plane 46 of
the runner wheel. In the illustrated case, they extend at an
angle of 10 degrees with respect to the horizontal.
The runner wheel 2 is the motor element of the hydraulic
turbine. Its purpose is to transform the power contained in
the kinetic momentum of the water flow into a torque for a
turbine shaft 20 coupled to an alternator 22 (as shown in
Figure 2). The turbine can be of a Kaplan type as illustrated
in the Figure, thus with adjustable (tilting) runner blades
24 extending in a radial plane 46 of the runner wheel 2' (or
slightly inclined with respect to the radial plane 46 if
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desired), or of a fixed blade type, e.g. a propeller type of
turbine as shown in Figure 4.
The new turbine can operate in a vertical axis as
illustrated, or in a horizontal or slanted axis.
Referring to Figures 1 and 3, the steps for refurbishing
an existent hydraulic turbine while increasing its power
capacities according to the present invention are as follows.
Any increasing of the diameter of the runner wheel 2 in
the existent turbine is limited by the wicket gates 10. These
wicket gates 10 or any radial distributor are eliminated in
the new turbine as shown in Figure 3, to recover axial space
under the water supply port 42.
The stayring 6 with the stay vanes 8 is replaced by a
new stayring 6' with stay vanes 8' having a greater height
for a greater water flow. The radial space thereby gained is
used to increase the diameter of the runner wheel 2 of the
new turbine. The water supply port 42 is reshaped to
accommodate the new stay vanes 8'.
In the illustrated case, a larger Kaplan runner wheel 2'
is used in replacement to the original runner wheel 2, which
allows to move the runner wheel downstream for the insertion
of the axial distributor 18 upstream to the runner wheel 2'.
The runner ring 34 is also reshaped accordingly.
The upper wall of the turning passageway 16 can be
conveniently formed by the bottom wall of the turbine head
cover 48 which is reshaped accordingly.
From a mechanical standpoint, the mechanisms 26 for
controlling the guide vanes 18 require space limited by the
bottom pit liner 28 under the spiral case 4. On the other
hand, the mechanical loads transmitted to the stayring 6'
should be transferred to the surrounding concrete. For this
purpose, a conical support ring 30 can be used to attach a
lower lining portion of the spiral case 4 to the stayring 6'
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and to the bottom pit liner 28, thereby allowing a transfer
of the loads to the concrete by the bottom pit liner 28 and
by the stack formed of the axial distributor's ring 32, the
runner ring 34 and the enlarging discharge ring 36. The axial
distributor's ring 36 may narrow towards the runner wheel 2'
to a diameter similar to a diameter of the runner wheel 21,
as shown in Figures 2, 3 and 4. The runner ring 34 may
likewise narrow as shown in Figures 2 and 3 or not, as shown
in Figure 4. The runner wheel 2 is preferably positioned as
close as possible with respect to a guide bearing 38 axially
guiding the shaft 20. To this effect, and due to the
importance of the hydraulic patterns, the axis of the guide
vanes 18 is slightly slanted as depicted by the dashed lines
40. The upper portion of the draft tube 12' is also reshaped.
The draft tube 12' is preferably further reshaped with a
larger elbow section generally aligned with the rotation axis
14 of the runner wheel 2', followed by a narrower passage
communicating with the sloped and enlarging section
downstream.
The axial distributor 18 may conveniently project around
the guide bearing 38.
The increased dimensions of the passages in the new
turbine reduce the speeds, the pressure variations and the
shearing effects in the water flow, which reduces stress on
the fish. Also, the reduction in the number of blades and
vanes in the stayring 6', the distributor 18 and the wheel 2'
combined to a reduction in the rotation speed reduce the
chances of collisions between the fish and the turbine.
While embodiments of this invention have been
illustrated in the accompanying drawings and described above,
it will be evident to those skilled in the art that changes
and modifications may be made therein without departing from
the essence of this invention.
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