Note: Descriptions are shown in the official language in which they were submitted.
81783667
Hydromotive Machine
[001]
Field of the Invention
[002] The present invention relates to hydroelectric generating apparatus and
water pumping
apparatus and the method of constructing the same. More specifically this
invention relates to
retrofitting hydroelectric generating apparatus and to pre-existing gated
water control structures
originally constructed at navigation locks and dams and at water storage
reservoirs where
hydropower facilities were not originally installed and to fitting pump
apparatus (especially for
high volume storm water pumping) into limited space such as may be available
in an urban
area. The disclosed improvements in hydromotive machine shut-off and axial
flow turbine
runners have diverse applications for fluid conveyance and power generation, a
few of many
possible application examples being described herein.
Description of the Related Art
[003] Hydromotive machines, in particular hydroturbines, have been used in
arrays in order to
achieve a prescribed flow capacity within a limited upstream/downstream
dimension and with
minimum apparatus weight and dimensions. Example related
1
Date Recue/Date Received 2020-05-28
CA 02873584 2014-11-13
1
= patents include US 4,755,690 to Obermeyer, US 4,804,855 to Obermeyer, US
5,825,094 to Hess, US 6,146,096 to Winkler, and US 6,281,597 B1 to Obermeyer
et al.
[004] Flow control to hydroturbines within an array of hydroturbines has been
by various
methods. US 4,755,690 to Obermeyer discloses flow control by means of
butterfly
valves within the draft tubes. Such valves require relatively large actuators
while the
valve causes backpressure on the draft tube and a reduction in power
generation.
Such butterfly valves must be rigid enough and built with sufficient precision
to maintain
tight contact at seals when closed.
[005] US 4,804,855 Obermeyer describes the use of multi-aperture ring follower
valves.
US 5,825,094 to Hess also incorporates in its description multi-aperture ring
follower
valves with the aforementioned operational limitations. US 6,281,597 B1 to
Obermeyer
et al describes the use of slide gates at the ends of the draft tubes as well
and includes
in its description the use of ring follower valves. Multi-aperture ring
follower valves have
the shortcoming that they require that multiple machines be started and
stopped
simultaneously. This results in having to shut down one or more operable
machines
even if only one of the machines associated with a multi-aperture ring
follower valve
must be shut down due to a mechanical or electrical fault condition. It is not
possible
with vertical ring follower gates to start the lowest rows first at low flows,
followed by
starting up upper rows after the tailwater is higher (as a result of higher
flows). Starting
the lower rows first is desirable, if not necessary, at many sites because the
natural
tailwater elevation is a function of river flow rate, the tailwater elevation
being lower at
2
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= lower flow rates. The flow associated with the lowest row of turbines may
need to be
flowing into the tailrace in order for the tailwater to rise sufficiently to
cover the next
higher row of draft tubes. Discharge of water from the draft tube at or below
tailwater
level is generally required in order to convert most of the energy in the
water to useful
electric power. A tailwater elevation may or may not be required in order to
prevent stall
of the draft tube, other factors being residual swirl conditions in the draft
tube, Froude
number of the draft tube discharge, and the use of any special guiding means
near the
draft tube exit. At low river flow rates the shortcoming of vertical multi-
aperture ring
follower valves may be overcome by the use of independently operable single
aperture
ring follower valves or by the use of horizontally actuated multi-aperture
ring follower
valves. Within the high power density assemblies required to economically
develop the
power potential at existing gated structures there is generally not space
enough
available for installation of the independently operated ring follower valves
that would be
required for turning on and off individual machines. Ring Follower valves also
cause
undesirable vibration of the rotating assembly during start up and shut down
and are ill
¨suited to sluicing water (discharging water at partial openings with the
generator off, as
is required at many facilities after a load rejection). Even though ring
follower valves are
much smaller than a draft tube gate located at the end of a draft tube,
significant force is
required for closure.
[006] Slide gates at the ends of draft tubes are heavy, expensive and require
large
actuators and hydraulic supplies. Additionally, the guide slots result in head
losses at
3
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= the draft tube exits due to losses across the slots themselves as well as
losses due to
the narrowing of the draft tubes that is required to accommodate the slide
gate slots.
[007] Hydromotive machine arrays with ring follower gates require space at one
side of
each such an assembly for stowing the following ring, and at the other side of
each such
an assembly for stowing the shutoff gate. Multi-aperture gate leaves minimize
assembly size but reduce flexibility of operation because all of the machines
controlled
by a single multi-aperture ring follower gate must be turned on and off
together as a
group. If a single machine has an electrical or mechanical fault, all of the
machines
controlled by the common ring follower valve must be shut down. In the case of
a
strictly run-of-river hydroelectric plant, if there is not enough water to run
all of the
machines, and if a continuum of reservoir inflow rates must be precisely
duplicated by
the hydropower plant discharge, all of the machines (on a common ring follower
gate)
may need to remain shut down even if there were enough water to run all but
one of
them. Flexibility of operation is required to accommodate varying flow rates
and to
maximize overall system availability.
[008] Pre-existing downstream gates may be used to control arrays of
hydromotive
machines, however, their use, as in the case of multi-aperture ring follower
valves
results in reduced flexibility of operation and reduced power generation for
run-of-river
operations. Pre-existing downstream gates have been used to control tailwater
for
turbines located in existing stop log slots.
[009] The prior art includes generator placed in draft tubes. A first example
being small
submersible Leroy Summer turbine generator sets marketed in the early 1980's.
These
4
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1 =
. machines had no guide vanes. Water entered the runner directly. Residual
tangential
kinetic energy leaving the runner was partially recovered by a draft tube
comprised of
concentric cones, the inner one being the housing for a speed increaser and
generator.
No attempt was made to recover the profile loss of the generator housing which
ended
abruptly at the end of the draft tube. A second example would be reversible
turbines
used at tidal plants and for filling and emptying locks. In general such
installations have
rather poor efficiency when the flow goes through the runner first then over
the
generator.
[0010] US Patent 3,854,848 to Laing discloses a submersible pump with integral
back-
flow prevention.
[0011] Adjustable pitch hydroturbine runners, also known as Kaplan runners are
well
known in the prior art and universally utilize blades adjustable about radial
axes. Small
inexpensive machines have been built with simple cylindrical discharge rings.
Large
vertical machines often have a cylindrical upper half of the discharge ring in
combination
with a spherical lower half. Large bulb turbines are generally provided with a
discharge
ring that is spherical both upstream and downstream of the runner centerline.
Such
discharge rings must be split in order to remove the runner for service. A
split discharge
ring is expensive. Provision of a block-out in the powerhouse structure that
surrounds
the split spherical discharge ring is also expensive. A disadvantage of the
downstream
portion of a spherical discharge ring is that low pressure occurs in the
vicinity of the
transition to the draft tube. These low pressures, when superimposed on low
pressures
associated with the turbine blades can cause cavitation and may in some cases
CA 02873584 2014-11-13
s = determine the turbine cavitation and power limits. Additionally the same
change in
. direction that causes the aforementioned low pressures also diminishes
draft tube
efficiency due to misalignment of flow entering the draft tube. The Deriaz
turbines
incorporate adjustable mixed flow runners for lower specific speed turbines
required for
lower plant cavitation coefficients that result from higher heads and higher
settings.
Deriaz runner blades are canted downstream (downward in the case of a vertical
machine). Adjustable water turbine blades canted upstream are unknown in the
prior
art.
[0012] Vertical slide or roller gates, for example, at the downstream ends of
draft tubes
may be used to control flow through vertical sets of turbines in one or more
rows.
Except in the case of a single row of turbines, such an arrangement typically
requires
that the lower turbine be opened first, followed by the next one up, and so
forth, with the
result that a fault calling for shutdown of the lowermost turbine generator
set requires
that all of the turbine generator sets controlled by the same draft tube gate
be shut
down. A further disadvantage of such an arrangement is that the net downstream
force
on each gate is high. This dictates the use of expensive friction reducing
means such
as wheels or rollers, or the use of powerful gate actuators. In the case of
hydraulic
actuators, this means that large, expensive, and heavy hydraulic accumulators
are likely
required.
[0013] Semi-Kaplan (with fixed guide vanes and adjustable runners) axial flow
hydroturbines are generally much less costly than fully regulated turbines
while
6
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= providing nearly identical peak efficiency and output and also providing
acceptable
. efficiency over a wide range of flows. In conjunction with semi-Kaplan
axial flow
hydroturbines, a valve, gate, or other shut-off means must be provided. Head
gates
may be used for this purpose, however a partially open head gate upstream of
an axial
flow turbine can cause severe vibration during start up and shut down. Water
flowing
under such a gate may drive the lower portion of the runner as a turbine,
while the
upper portion of the runner rotating in the wake of the partially shut head
gate acts as a
pump (toward downstream). This situation results in asymmetric forces on the
runner
and may damage bearings or seals or cause sufficient shaft deflection to cause
blade
contact to the discharge ring.
[0014] Draft tube gates for controlling semi-Kaplan machines fall into several
categories,
each with certain disadvantages. Ring follower gates for large runners require
significant space for stowing on one side the ring portion of the gate leaf
and for stowing
on the other side the solid portion of the gate leaf. Draft tube gates at the
end of the
draft tube result in relatively low hydraulic losses but are very large and
expensive and
difficult to close quickly in the case of load rejection. Draft tube gates
located closer to
the runner result in head losses from the required openings and guides.
[0015] Semi-Kaplan hydroturbines have been built with blades configured to
seal to one
another when in the fully closed position. This is an inexpensive solution but
requires
compromises in blade design and turbine efficiency and also results in
incomplete shut
off due to blade tip leakage. Catastrophic failure may occur if the blade
servo
7
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=
= mechanism fails to close the blades after load rejection, blade servo
mechanisms being
. generally less robust than draft tube gates, for example, which may be
designed to
close under the force of gravity alone.
[0016] In the case of the prior art of flow and back-flow control to axial
flow pumps, slide
gates as well as flap type check valves have been used, each imparting
unnecessary
head losses to the flow and requiring larger more powerful pumps than would
otherwise
(in accordance with the present invention) be required. The use of cylinder
gates
conformed to the outside of their associated submersible electric motors in
unknown in
the prior art. The use of a conical gate in conjunction with a submersible
pump for the
purpose of backf low prevention, which seals between the diffuser or
"straightening
vane" shroud and the motor housing is unknown in the art, as is the use of
such gates in
conjunction with arrays of pumps.
[0017] In the case of bulb and pit type axial flow hydraulic turbines with
adjustable
runners, efficiency is enhanced and cavitation damage minimized by the
provision of a
spherical discharge ring around the runner. Installation and removal-for-
service of the
runner requires that the discharge ring be split and also requires that at
least the upper
half of the discharge ring be removable. This requires a heavier and more
expensive
discharge ring than would be required if the discharge ring were embedded in
concrete.
A split also requires extra reinforcing steel in the powerhouse in order to
carry structural
loads around the required access pit. For vertical Kaplan turbines in
particular the
discharge ring spherical surface has been commonly omitted above the runner
8
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1 =
= centerline at the expense of turbine efficiency, risk of cavitation
damage, and increased
. fish mortality in order to facilitate runner installation and removal
from above.
[0018] Cylinder gates were commonly used on Francis type turbines in the early
1900's
for load and speed control as well as for shut off. These cylinder gates were
located
between a set of fixed guide vanes and a Francis type (radial inflow) runner.
An electric
generator, if used, was located outside of the water passageway and was often
driven
by a system of pulleys and belts to facilitate use of a higher speed and less
expensive
generator.
[0019] More recently cylinder gates have been used in conjunction with semi-
Kaplan
and propeller hydroturbines in conjunction with radial inflow guide vanes. In
at least one
instance, a cylinder gate is located outside of the radial inflow guide vanes.
In at least
another instance, the cylinder gate is located immediately inside the radial
inflow guide
vanes. In these cases power is carried by a vertical shaft to a generator
located outside
of the water passageway.
[0020] Cylinder gates significantly larger than the generator OD and extending
above
headwater level have been used as shutoff devices for vertical axial flow
turbines with
integrated submersible generators. Such cylinder gates, when open are
withdrawn
entirely away from the flow path to the hydroturbine.
9
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f
' [0021] In conjunction with either individual submersible axial flow turbines
or pumps (as
. a group herein defined as "Hydromotive Machines"), or arrays of the
same, the use of
cylinder gates configured to seal between the downstream end of the outside of
the
motor or generator housing and the inside of a conical distributor or diffuser
shroud, or
an extension thereof, is unknown in the art. Likewise, the use of cylinder
gates that
closely conform to a generator or motor housing when in the open position is
unknown
in the art.
[0022] It is generally uneconomical to provide adjustable guide vanes or
adjustable
runners in conjunction with the small turbines used in arrays. Such machines
are
predominantly provided with fixed guide vanes and with fixed runners which are
less
expensive and more robust, allowing for the use of coarser trash screens. For
their
design synchronous speed (in the case of synchronous generators) or near
synchronous speed (in the case of induction generators) such machines
discharge a
fixed amount of water at any given available head. For hydroelectric plants
required for
environmental reasons to operate in run-of-river mode, this characteristic
results in step
changes in flow as machines are turned on or turned off. The use of speed
adjustment
of the operating machines as a group for flow adjustment compensating for
turning
individual machines on or off is unknown in the prior art. The use of speed
adjustment
to control residual draft tube swirl to prevent flow separation from the top
of the draft
tube under low tailwater conditions is also unknown in the art.
CA 02873584 2014-11-13
, .
' [0023] Large bulb turbines installed individually or side-by-side in
accordance with prior
. art have several shortcomings in addition to those mentioned above. A
large diameter
horizontal axis runner, 8 meters in diameter, for example, has a significantly
lower plant
cavitation coefficient at the top of the runner compared to at the bottom of
the runner.
Accordingly, the output nearer the bottom of the runner is limited by the
cavitation limit
at the top of the runner. A large diameter horizontal runner is most efficient
in
conjunction with a horizontal draft tube, the top of which must be below
minimum
operating tailwater elevation. This requirement results in an otherwise
unnecessarily
deep setting of the powerhouse, extra excavation work, and extra concrete
work.
Summary of the Invention
[0024] According to one aspect of this invention, a compact and integrated
shut-off
means is provided to hydromotive machines such as pumps, turbines, or pump-
turbines
having submersible motors, generators or motor-generators. In a preferred
embodiment in conjunction with hydroturbine, a cylinder gate is provided, that
when
open, is stowed around the outside of the generator housing or an extension
thereof.
Said cylinder gate is preferably configured to conform to the exterior of the
generator
housing so as to offer minimal resistance to flow going past the outside of
the cylinder
gate toward the turbine inlet, guide vanes and runner. In accordance with a
further
aspect of this invention, a small 6 mm (measured radially), for example,
annular gap
may be provided between the cylinder gate and the generator housing to allow
for water
cooling of the generator. In accordance with a further aspect of this
invention, bearing
elements on attached to the cylinder gate and to the generator housing serve
to guide
11
CA 02873584 2014-11-13
= the cylinder gate between its open and closed positions. In accordance
with a further
. aspect of this invention, said bearing elements may also serve to
wipe any accumulated
and adhered scum off of the generator housing outside diameter and cylinder
gate
inside diameter, respectively. In accordance with a further aspect of this
invention,
holes, slots, or other flow allowing means in the said bearing elements may be
provided
to allow water flow between the generator housing and the stator outside
diameter.
[0025] This invention also applies to axial and mixed flow pumps for which a
cylinder
gate, nearly identical to that herein described for use with axial flow
turbines, can
provide positive controlled shut off at low cost and in a small space. It the
case of a
pump, flow is typically opposite to that in a turbine, i.e., from the diffuser
vanes (guide
vanes in the case of a turbine) then along the motor (generator in the case of
a turbine).
In accordance with a further aspect of this invention, pumps may be equipped
with a
conical gate, the upstream end of which seals against the motor housing in a
manner
similar to the sealing of a cylinder gate to a generator housing as described
elsewhere
in this specification. Such a conical gate is usefully subject to pressure
imbalance and
in accordance with a further aspect of this invention, may be configured to
shift position
in response to the direction of flow, automatically closing upon reverse flow.
In
accordance with a further aspect of this invention, springs may be used to
augment
closure, especially if the conical gate must move upward or up an incline to
close. In
accordance with a further aspect of this invention, such a conical gate may be
preferably configured to open to a position causing almost zero head loss when
the
pump is running. In accordance with this embodiment of the invention, when the
pump
12
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. .
. is shut down, back-flow causes the conical valve to shift toward the
impeller and
- diffuser, until it seats and seals against the diffuser shroud while also
sealing to the
motor housing. In accordance with this embodiment of the invention, the
conical gate
itself may be configured for flow passage through the gate when open or both
through
and around the gate when open, as illustrated in the drawings and described in
the
detailed description of the preferred embodiments of this specification. In
accordance
with a further aspect of the present invention, a submersible axial flow pump
is provided
that incorporates a cylindrical or conical shut off valve, that when closed,
seals between
the diffuser shroud, or extension thereof, and the impeller end of the motor
housing. In
accordance with an embodiment of this invention, a cylindrical shut off valve
provides
balanced hydraulic forces and requires one or more nominally sized
actuator(s). Such a
cylindrical valve, or "cylinder gate", is preferably stowed around the outside
of the motor
housing or extension thereof. In accordance with an embodiment of this
invention, such
a conical valve is acted upon by imbalanced hydraulic forces that tend to shut
the valve
against back flow. Such a configuration requires no separate actuator(s). The
conical
valve, in accordance with a further aspect of this invention, is most
advantageously
positioned, when open, at a prescribed standoff distance from the motor
housing
opposite the impeller end of the motor housing. In this prescribed position,
said conical
valve acts as an axisymmetric guide vane that serves to minimize flow
separation from
the downstream end of the motor housing, while also being aligned with the
flow to
which it therefore impedes only minimally.
13
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= [0026] In accordance with a further aspect of this invention, parallel
pumps are
= provided, one or more of which are fitted with a back flow prevention
valve as described
above and elsewhere in this specification.
[0027] In accordance with a further aspect of this invention, two or more
axial flow
submersible pumps fitted with cylindrical or conical valves as above described
may be
located side-by-side or one-atop-the-other.
[0028] In accordance with a further aspect of this invention two or more axial
flow
submersible pumps fitted with cylindrical or conical valves as above described
may be
arranged in an array of at least two pumps high and at least two pumps wide in
order to
provide high pumping capacity in a compact form factor, especially within a
limited
overall length (as measured in the general direction of flow).
[0029] The compact integrated shut-off means afforded by the cylinder gate of
this
invention, especially in conjunction with the adjustable runner able to be
removed
through the draft tube, facilitates the construction of compact hydropower
facilities using
arrays of turbines (one above another as well as side-by side). For a given
turbine
geometry, the weight is proportional to the cube of the runner diameter, while
the power
output is proportional to the square of the runner diameter. For a given
turbine
geometry, the weight per kilowatt of power is thus proportional to runner
diameter. In
accordance with this invention, it becomes more economical and more practical
to, for
example, manufacture and install 8 turbines each of 3 meters runner diameter
instead
14
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, .
' of 2 turbines each of 6 meters runner diameter. If the turbines are stacked
2 high, the
_ power house width remains unchanged and the length is decreased by
roughly 50%,
based on homologous water passageway shapes. The weight of the geometrically
identical manufactured metal components (such as runner blades) is reduced by
50%.
In addition to the cost savings associated with the size and weight
reductions, there are
transportation and equipment procurement advantages. Smaller assemblies also
allow
assembly work to be efficiently and reliably performed in factories or other
assembly
areas not subject to the hazards and expensive logistics of working in a river
or other
watercourse. In the case of a sufficiently small upstream/downstream length,
rail or
road shipment of completed assemblies may be enabled.
[0030] According to a preferred embodiment of this invention, a cylinder gate
is fitted
around a submersible generator in a manner that allows it to be moved
downstream to a
fully closed position and moved upstream to a fully open position. In the
downstream
position it preferably seats against a compliant sealing element such as a
water
passageway conforming rubber ring. The rubber ring, in an example embodiment,
may
be secured between the flange of a turbine distributor shroud and an inlet
fairing. The
inlet fairing may span between the inlets of a plurality of individual turbine-
generator or
other hydromotive machine sets. The cylinder gate preferably has a rounded
downstream edge such that it forms a smooth water passageway transition from
the
cylinder gate outside diameter to the distributor hub, which is likewise
shaped to create
a smooth water passageway surface. The cylinder gate may be actuated by
hydraulic
cylinders, for example. In the case of actuation by two diagonally opposite
hydraulic
CA 02873584 2014-11-13
= cylinders used for the purpose of actuating the cylinder gate, the two
cylinders may
- advantageously be placed at top dead center and bottom dead center
downstream of
the upstream generator support column, if used. In this manner the hydraulic
cylinders
are located in flow already disturbed by the generator support column. The
cylinders
may be attached to the generator support column. The upstream generator
support
column may be used to house power cables, control cables, lubrication lines,
pressurization lines, water drainage lines, ventilation ducts, ladders, and
the like. 2 or
more hydraulic cylinders used to actuate a cylinder gate may be synchronized
hydraulically, for example in order to maintain alignment of the cylinder gate
throughout
its length of travel and in spite of waterborne debris such as sticks of wood
that might
otherwise cause the cylinder gate to become misaligned and jam. It is
advantageous in
some cases to provide stay vanes for support of the generator. The stay vanes
are
preferably upstream extensions of the guide vanes and are bounded at their
upstream
edge by the path of cylinder gate closure defined by a roughly triangular
shaped area
bounded by a guide vane, the distributor hub and a line at the cylinder gate
parallel to
the direction of cylinder gate movement. The downstream boundary of each stay
vane
is the guide vane to which it is integrated. The inner edge of each stay vane
is
preferably provided in conjunction with compatibly designed (non-interfering)
guide
vanes and runner to provide a turbine generator set with integral shut-off
means.
[0031] In accordance with a further aspect of this invention, not all guide
vanes need be
connected to stay vanes. For example 8 guide vanes might be used, 4 of which
are
extended upstream as stay vanes. Alternatively, 12 guide vanes might be used,
4 of
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CA 02873584 2014-11-13
' which extend upstream to form stay vanes. In cases of non-axi-symmetric
inlet
= conditions, due for example to horizontal and vertical machine spacing
being different,
the use of no more than 4 stay vanes, preferably located at or near the 12
o'clock, 3
o'clock, 6 o'clock and 9 o'clock positions may be preferably so as not to
impede (with
stay vanes) circumferential adjustment of streamlines as they approach the
guide vane
inlets.
[0032] In accordance with a further aspect of this invention, each guide vane
may be
extended as a stay vane and made to closely fit the cylinder gate, which may
also be
configured with a hard and sharpend downstream edge. In such a configuration
the
clinder gate can wipe any lodged debris off off the leading edge of the stay
vanes and
then cut it off wit the sharp edge of the cylinder gate as the cylinder gate
seals to a
resilient seat between the distributor shroiud and the inlet fairing.
[0033] In accordance with a further aspect of this invention, they stay vanes
may be
closely fitted to the cylinder gate so as to guide the cylinder gate as it is
being opened
and closed.
[0034] In accordance with a further aspect of this invention, slide beasrings
may be
positioned between the cylinder gate and each of any cylinder-gate-guiding
stay vanes.
[0035] In accordance with one aspect of this invention, hydraulic cylinder
gate actuators
may be hydraulically synchronized in order to prevent cocking of the cylinder
gate
17
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- during opening or closure. Such synchronization may be by means of cylinders
operated in series, by means of piston-type flow dividers, by means of
position
measurement in conjunction with electronic valve control means, or by means of
gear
pump type flow dividers, for example.
[0036] In accordance with a further aspect of the invention, the cylinder gate
may be
provided with extra length such that the distance between its upstream and
downstream
guiding contact with the generator housing is never less than approx. .1/4 of
the cylinder
gate diameter.
[0037] According to a further aspect of this invention, a cylinder gate fitted
around a
submersible generator may be provided in conjunction with compatibly designed
(non-
interfering) guide vanes and a Francis type (radial inflow) runner.
[0038] According to a further aspect of this invention, a cylinder gate fitted
around a
submersible generator may be provided in conjunction with compatibly designed
stay
vanes and guide vanes and a modified Francis type (radial inflow) runner. The
inlet
guide vanes are preferably optimized to direct flow from its generally axial
approach
direction toward the runner inlet. The modifications of such a runner being
arrived at
using computational fluid mechanics software to take into account the
constraints of
axial flow around the generator, in combination with stay vanes delimited by
the travel of
the cylinder gate, and runner discharge into a straight draft tube.
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CA 02873584 2014-11-13
= [0039] In accordance with a preferred embodiment of this invention, a
cylinder gate is
. provided for control of flow through one or more hydroturbines in an
array of
hydroturbines. The cylinder gate is preferably stowed against and supported by
the
outside of the generator housing when it is in its open position. In this
configuration it
causes minimum head loss to the hydroturbine even in configurations where
incoming
flow is parallel to the hydromotive machine axis and of high velocity. The
cylinder gate
preferably seals at its downstream end to a sealing surface that blends from a
hydraulic
flow standpoint with the distributor shroud. Said sealing surface is
preferably composed
of a compliant yet wear and corrosion resistant material such as an elastomer
or
polymer. The cylinder gate is preferably actuated by synchronized actuators
such as
synchronized hydraulic cylinders. In order to minimize head losses, two
cylinders, for
example, may be located at top dead center and bottom dead center. In this
manner,
the cylinders may be attached to required turbine support columns and may
thereby
located in the flow shadow of the support columns, resulting in less-than-
additive head
losses for the support column ¨ gate actuator combination. The two
synchronized
actuators provide alignment in one axis. Alignment in the second and third
axis may be
by means of guide means, also at top dead center and bottom dead center.
Prevention
of rotation along axis 1 and axis 2 allows the cylinder gate to shut tightly
even in the
presence of debris which it may be designed to cut off. Alignment of the
cylinder gate
may also be maintained by allowing the downstream inner diameter to slide
along the
upstream edges of at least some of the inlet guide vanes in the case of a
turbine, or
along the outlet edge of the diffuser vanes in the case of a pump.
Notwithstanding the
hydraulically desirable close fit of the cylinder gate to the generator,
cooling channels or
19
CA 02873584 2014-11-13
. '
' a cooling annulus may be provided allow water cooling of the generator
housing, which
. might otherwise be impeded by the cylinder gate.
[0040] Because the net hydraulic force on the cylinder gate over its full
range of position
is near zero, the cylinder gate actuators and associated attachment points may
be much
smaller than the actuators and attachment points associated with a slide gate.
The
required hydraulic pumps, control valves, and accumulator may likewise be much
smaller than those required for actuation of slide gates. The amount of
hydraulic fluid at
risk of leakage into a watercourse is likewise reduced.
[0041] The use of cylinder gates in accordance with the present invention
eliminates the
need for draft tube gates and their associated guides and sealing surfaces at
the
discharge end of the draft tube. The draft tubes may thus be terminated
adjacent to one
another,adjacent to the downstream concrete sill, and adjacent to piers or
abutments, if
any. This draft tube configuration results in lower draft tube exit velocities
and the
elimination of head loss caused by sudden changes in water passageway cross
section
at the location of the otherwise required draft tube gate guides. It should be
noted that
there are other alternatives to controlling flow through a hydromotive
machine. These
include: upstream slide gates, draft tube butterfly valves, and slide gates
within the
length of the draft tube. The advantages of the present invention apply
equally, if not
more, to each of these. Compared to upstream slide gates, the cylinder gate of
the
present invention is more readily moved out of the path of incoming flow when
open, is
much lighter in weight and of lower cost, and does not cause vibration
inducing
CA 02873584 2014-11-13
. .
= asymmetric flows as it is being opened or closed. Compared to a draft
tube butterfly
. valve the cylinder gate of the present invention is lighter weight and
lower cost and does
not contribute to draft tube (hydraulic) losses. Compared to slide gates
within the length
of the draft tube, the present invention is lighter weight and less expensive,
does not
prevent the installation of immediately adjacent rows of additional machines,
and does
not interfere with the hydraulic efficiency of the draft tube.
[0042] In accordance with a further aspect of this invention, a hydroturbine
is provided
wherein the generator is within a draft tube and downstream of the runner. The
generator is preferably radially supported on its upstream end by shaft
extending
upstream of the runner into a guide bearing supported by the distributor hub.
The guide
bearing may be water lubricated, for example. The generator housing is
preferably
supported on its downstream end by a plurality of struts, which may be
streamlined
vanes, that secure the generator with respect to four degrees of freedom,
namely
against downstream thrust, against the torque about the turbine axis of
rotation, and
against translation in the plane normal to the turbine axis of rotation
(vertically and
horizontally in the case of a horizontally oriented hydroturbine generator
set).
Preferably said struts provide exact constraint of the generator, i.e., they
do not over-
constrain the generator. Over-constraint can result in unpredictable states of
tension
and compression in said streamlined vanes resulting in unpredictable resonant
frequencies. Residual stress from welding, bolt tightening, or from external
structural
loads, for example, can shift a strut resonant frequency to correspond with an
inherent
excitation frequency such as rotational speed, blade passing frequency, etc.,
resulting in
21
CA 02873584 2014-11-13
= resonance and failure. Said struts may be asymmetrically configured so as
to also
= serve as diffusers and thereby convert residual tangential velocity to
incremental energy
recovering pressure gradient across the runner. Tie rods immediately
downstream of
the runner as used in conjunction with prior art hydroturbines to secure a
generator
within a draft tube are omitted in order to accommodate the cylinder gate and
to
maximize hydraulic efficiency. The cross section drag of the generator in the
draft tube
may be minimized by deliberate optimization and coordination of other aspects
of the
water passageway. Counter-intuitively, the profile (energy) loss associated
with the
generator in the water passageway may be minimized so as to be roughly equal
to or
even less than the profile (energy) loss of a conventional runner hub fairing
used in the
most common axial flow hydroturbine configuration wherein flow exits the
runner and
passes over a runner hub fairing and then into the draft tube. Although the
profile area
of the generator is much larger than the profile area of the runner fairing,
the lower
velocities passing over the generator result in a lower profile (energy) loss.
Conservation of angular momentum causes fluid with even a small angular
velocity
component exiting the turbine blades nearest the runner hub to attain a much
higher
angular velocity as the runner fairing reduces in diameter further downstream.
The
result is that a long runner hub fairing terminating at less than
approximately .2 D
(where D=rubber diameter) or even in a sharp point provides little or zero net
gain in
turbine efficiency.
[0043] By transitioning within the draft tube from the runner hub diameter at
the blade
exit to the diameter of the generator housing, the tangential velocity
components of flow
22
CA 02873584 2014-11-13
exiting the runner are usefully reduced in a manner that imparts incremental
suction to
. the runner. Any remaining tangential velocity component may be recovered
further
downstream by the use of diffuser vanes at a position in the water passageway
with low
velocities where the loss resulting from such diffuser vanes is minimal. In
accordance
with an aspect of this invention, such diffuser vanes may be located
downstream of the
open position of a cylinder gate located around the periphery of a generator.
Such an
arrangement can be configured with an overall length of the draft tube of
approximately
40, which falls within the range of conventional axial flow hydroturbine draft
tubes, in
conjunction with which the generator is located elsewhere. The omission of
both the
generator and the flow shut off gate as contributors to overall assembly
length greatly
facilitates the installation of hydroturbines in accordance with this
embodiment of the
invention into restricted spaces such as into stop log slots at pre-existing
water control
structures and into radial gate assemblies, for example. By dividing the
available
vertical (from operating tailwater elevation to gate invert, for example) and
horizontal
dimensions (distance between piers, for example) of the available water
passageway
into discrete rows and columns of turbines, a runner diameter may be selected
to attain
the desired (and presumably constrained) dimension parallel to the direction
of flow.
This embodiment provides a favorable runner-diameter-to-overall-length ratio
while
eliminating runner hub fairing profile losses, the efficiency penalty of a
drag inducing
submerged rotor of a rim generator of (favorable runner-diameter-to-overall-
length ratio
prior art) and the efficiency penalty of the shutoff gate required for prior
art hydroturbine
generators including those of rim generator type.
23
CA 02873584 2014-11-13
[0044] In accordance with a further aspect of this invention, a hydroturbine
with an
= adjustable runner is provided having a plurality of blades, 3, 4, or 5,
for example, each
rotatable about an axis angularly equally spaced from the axis of each
adjacent blade,
with the axes as a group lying on a common cone with its apex downstream and
with
the blades extending slightly (5 degrees, for example) upstream and radially
outward
therefrom. The spherical discharge ring surface required for minimization of
blade tip
gaps is extended upstream while being truncated downstream, preferably at a
station
where it becomes tangent to a coaxial cylinder equal in diameter to the
spherical
discharge ring. The slight velocity increase upstream of the runner entrance
is tolerable
from a cavitation standpoint because the water has not yet gone through the
runner and
the pressure is still relatively high at this location. This velocity increase
may be
minimized by narrowing or necking down the distributor hub upstream of the
runner in
order to accommodate a greater proportion of the total flow nearer to machine
axis.
Such an arrangement is advantageous compared to the prior art adjustable axial
hydroturbine runners for the following reasons:
1) The runner may be installed or removed from the turbine through the draft
tube
and without the need for the discharge ring being disassembled. This allows
use
of a less expensive discharge ring that need be neither split nor removable
and
which in turn allows construction of a less expensive powerhouse.
2) Because the runner does not need to be removed upwardly from its operating
position, machines may be stacked one upon the other while maintaining access
to all runners. Accordingly, a hydropower installation comprised of small
machines can have the same output as a powerhouse comprised of larger
24
CA 02873584 2014-11-13
. =
. machines while also having a substantially reduced footprint, i.e.,
projected area
on a horizontal plane. This results, for example, in being able to substitute
four
machines (two machines high x two machines wide, for example) of half the
runner diameter to achieve the same hydraulic capacity and output with a lower
cost powerhouse of half the length and half the footprint (projected area on a
horizontal plane).
3) Because the water passageway cross sectional area is increased at the
runner
exit, and because the water is not caused to flow over the relatively severe
transition between spherical discharge ring and tapered draft tube, runner
cavitation limits and therefore, power output limits are improved.
4) Because of better alignment of flow exiting the runner with the interior of
the draft
tube, draft tube efficiency, and therefore turbine efficiency as well, is
improved.
The net result is an axial flow turbine that is less expensive to manufacture,
less
expensive for which to build the required concrete structure, i.e.,
powerhouse, and has
greater power output compared to the prior art.
[0045] In accordance with yet another embodiment of this invention,
hydroturbine
generators or pumps as described herein may be operated at speeds independent
of
the lines frequency. In the case of an installation comprised of a plurality
of
hydromotive machines of fixed geometry, the flow rate through each machine may
be
varied by varying its speed even though its geometry is not varied. By so
adjusting the
flow rate of (preferably all) machines in operation, the number of machines
running may
be increased or decreased without creating step changes in flow rate. The
speed may
CA 02873584 2014-11-13
=
also be usefully optimized at any point in time to attain certain objectives,
for example,
to maximize plant efficiency, to maximize plant output, to prevent cavitation,
to maintain
uniform flow rates, and to prevent separation from the top of the draft tube
in the case of
low tailwater, for example. Furthermore, operating speeds at any instant in
time may be
adjusted to attain the instantaneous best combination of the above objectives.
Machines in different rows, i.e., at different elevations, may be operated at
different
speeds in accordance with differing cavitation limits resulting from different
settings
relative to tailwater.
[0046] In accordance with a further aspect of the invention, power from
hydroturbines
with induction generators may first flow to one or more "active front end"
portions of a
regenerative inverter located at the (typically submerged) turbine assembly
and thence
along a common DC bus, and thence to the line frequency interface portion of
the
inverter system. This arrangement results in simplified movable electrical
power
transmission means between the movable assembly of multiple turbine generator
sets
and the fixed power transmission line. For example, instead of a 3 phase
alternating
current cable from each of many turbine generator sets to a fixed switchgear
system, 2
shared direct current conductors may be used in the form of a single 2
conductor cable
or 2 conductor movable or disconnectable bus bar, for example.
[0047] In accordance with a further aspect of the invention, power for
operation of
auxiliary devices such as hydraulic pumps and control devices may be generated
within
one or more turbine-generator sets, by use of an auxiliary winding, for
example.
26
CA 02873584 2014-11-13
'
. [0048] In accordance with a further aspect of the invention, a fiber
optic line
communications cable may be incorporated into the power cable for control and
monitoring signal.
[0049] In accordance with a further aspect of the invention, the fiber optic
line may be
installed in a sheath within the power cable assembly in a manner that allows
the fiber
optic line to be readily replaced without replacing the power cable assembly
as a whole.
[0050] In accordance with a further aspect of this invention, an array of
hydroturbines is
rotatably mounted in a water passageway such that water from either direction,
relative
to the fixed structure, may be allowed to flow through the array of turbines
in the same
direction, relative to the turbines. In this manner, high turbine efficiency,
90 %, for
example, may be attained with either direction, relative to the fixed
structure in which
the turbines are installed.
[0051] In accordance with a preferred embodiment, such physically reversible
arrays of
turbines may also be operated at variable speed in conjunction with an
inverter system,
for example. With such a combination, high efficiency may be maintained over a
wide
range of head and with flows in either direction. Such bi-directional
operation at varying
head is desirable and advantageous for recovering energy from water used to
fill and
empty navigation lock chambers, and in conjunction with tidal energy plants,
for
example.
27
CA 02873584 2014-11-13
= [0052] In accordance with a further aspect of this invention, hydromotive
machines
, installed one above another may be operated at differing specific power
levels in
accordance with instantaneous plant cavitation coefficients, the lower
hydromotive
machines being operated at higher specific power levels, by adjusting the
speed of the
turbine generator sets, for example.[0047] In accordance with a further aspect
of this
invention, hydroturbines installed one above the other may be operated in a
sequence
such that the lower machines are started first and shut down last so as to be
able to
efficiently operate the plant with tailwater levels lower than the tops of the
draft tubes of
the upper row hydroturbines. After flows are established by flow through all
of the lower
hydroturbines, tailwater may rise sufficiently to begin operating the next
higher row of
machines.
[0053] In accordance with a further aspect of this invention, horizontal axial
flow pumps,
installed one above the other, may be sequenced such that the lowest row
operates first
with intake levels sufficient for vortex entrainment free operation of the
lowest row. As
intake levels continue to rise with the lowest row operating, the next higher
row may be
started as a group or individually once the intake levels are high enough to
prevent
vortex entrainment with respect to said next higher row. Such sequencing
serves also
to suppress cavitation.
[0054] In accordance with a further aspect of the invention, an installation
of generally
horizontal axial flow hydromotive machines, at least some installed one above
the other,
may be installed in generally horizontal rows of varying width, the smaller
rows being at
28
81783667
the bottom. In this manner, the hydromotive machine installation intake shape
may be made
to more closely align with trapezoidal flow channels at the installation
inlet, outlet or both.
[0055] In accordance with a further aspect of the invention, one or more
hydromotive
machines may be movably installed upstream of pre-existing water control
gates, wherein the
tailwater conduit between said one or more hydromotive machines and said pre-
existing
water control gates may be sealed off from atmospheric pressure and in
conjunction with
which the pressure above the top of the opening of at least one of the pre-
existing water
control gates may be maintained at a pressure lower than atmospheric pressure,
by means
of hydraulically driven air entrainment and removal or with a vacuum pump, for
example.
Such an arrangement may be used to lower the effective tailwater elevation to
an elevation
below the physical elevation of all or a portion of affected draft tube
outlets. Such an
arrangement may be particularly beneficial in the case of hydroturbines
stacked one above
the other, as may be require in order to meet output objectives within a water
passageway of
limited size.
[0055a] According to an aspect of the present invention, there is provided a
submersible
hydroturbine-generator set comprising: a hydroturbine, the hydroturbine
comprising a runner
with adjustable runner blades having pivot axes that are canted such that an
intersection of
each blade pivot axis at a discharge ring is further upstream than an
intersection of each
blade pivot axis at a closest point of the pivot axis to a main shaft
centerline; a generator
operatively coupled to the hydroturbine; and a cylinder gate surrounding a
housing of the
generator, the cylinder gate being axially movable between an open position in
which the
cylinder gate allows water flow past the hydroturbine and a closed position in
which the
cylinder gate blocks water flow past the hydroturbine.
29
Date Recue/Date Received 2020-12-16
CA 02873584 2014-11-13
. =
=
= Brief Description of the Drawings
Figure 1 shows a prior art hydroturbine installation with a prior art cylinder
gate.
Figure 2 shows a prior art cylinder gate as used in a Francis turbine.
Figure 3 shows a prior art bulb turbine powerhouse.
Figures 4a and 4b show a submersible turbine generator set with the the
cylinder gate
open and with the cylinder gate closed, respectively.
Figures 5a, 5b, 5c, 5d, and 5e show a submersible turbine generator set with
cylinder
gate in various views.
Figure 6 shows a submersible turbine generator set with a mixed flow runner
and a
cylinder gate.
Figure 7a shows a sectional elevation of a powerhouse with cylinder gate
controlled
high specific speed turbines stacked two high.
Figure 7b shows a plan view of the powerhouse of 7a.
Figure 8 shows a sectional elevation drawing of an assembly of cylinder gate
controlled
submersible turbine generator sets installed as a replacement for a
submergible radial
gate.
Figures 9a, 9b, and 9c show views of an example runner hub mechanism suitable
for
operation of the high specific runner in accordance with this invention.
Figure 10 shows a pump with cone valve.
Figure 11 shows a pump with cone valve.
CA 02873584 2014-11-13
' Figure 12 shows a sectional elevation of a water turbine with a cylinder
gate and
. generator in the draft tube.
Figure 13 shows a submersible hydroturbine with a cylinder gate and generator
in the
draft tube in conjunction with a Francis runner.
Figure 14a shows a plan view of an array of hydroturbines that utilize flows
in either
direction by being rotated 180 degrees about a vertical axis.
Figure 14b is a view of the inlet end of the array of turbines of Figure 14a.
Figures 15a, 15b, and 15c are exit end view, sectional elevation view, and
entry end
view, respectively of a hydroturbine with an adjustable runner with canted
blade pivot
axes, generator in the draft tube, and a cylinder gate shown in the open
position.
Figures 16a, 16b, and 16c are the same views as Figures 15a, 15b, and 15c,
except
with the cylinder gate shut.
Figure 17 is a sectional elevation of a hydropower plant with two staggered
rows of
turbines, one above the other.
Figure 18 is a sectional elevation of an array of hydroturbines installed in a
gate service
stop log slot, in conjunction with which air is evacuated from the water
passageway
between the turbine array and a downstream control gate.
Figure 19 illustrates the use of multiple air gap axial flux permanent magnet
generators
in conjunction with cylinder gates and mixed flow runners.
Figures 20a, 20b, 20c and 20d illustrate a hydroturbine with the generator and
cylinder
gate in the draft tube in conjunction with a fixed pitch runner.
Figure 21 illustrates the use of an external rotor permanent magnet generator
in
conjunction with hydroturbine in accordance with the present invention.
31
CA 02873584 2014-11-13
=
= Figure 22 shows a cut-away view of a turbine with a cylinder gate stowed
when open
, around a generator located within the draft tube.
Figures 23a, 23b, and 23c show inlet end, cut-away, and exit end views of the
turbine of
Figure 22.
Figure 23d shows velocity triangles at stations 1,2,3,4,and 5 for the turbine
of Figures
23a, 23b, and 23c.
Figure 24 shows cross sections of the turbine of Figures 22 and 23a, 23b, and
23c.
Figure 25 shows approximate water passageway area as a function of axial
position
through the water turbine of Figures 22, 23a ,23b, and 23c.
Figure 26 shows the water turbine of Figures 22, 23a,23b, and23c with the
cylinder gate
open.
Figure 27 shows the water turbine of Figures 22, 23a,23b, and23c with the
cylinder gate
closed.
Figure 28 shows the inlet end of an array comprised water turbines similar to
the one
shown in Figures 22, 23a, 23b, and 23c.
Figure 29 shows the outlet end of an array comprised water turbines similar to
the one
shown in Figures 22, 23a, 23b, and 23c.
Description of the Preferred Embodiments of the Invention
[0056] Referring to Figure 1, a prior art turbine installation utilizing
cylinder gates is
shown. The illustrated prior art cylinder gates 1 are sized sufficiently large
to allow
complete removal of a hydroturbine-generator set through a closed cylinder
gate 1. The
large space between the cylinder gate 1 and the generator 2 housing outside
diameter
32
CA 02873584 2014-11-13
limits the use of such a cylinder gate 1 to vertical installations wherein the
cylinder gate
= 1 extends above water level in its closed position. Furthermore, the
configuration of the
vertical guides 26 requires that they be positioned radially distant from the
distributor
inlet 27 in order to not cause unacceptable disturbance to the turbine inlet
flow. The
illustrated generator 2 housing outside diameter is too small for an
economically
designed direct drive generator, a gear speed increaser 28 thus being required
The
gear speed increaser 28 generally results in a shorter turbine generator life
with lower
reliability compared to a direct drive alternative.
[0057] Figure 2 shows a prior art cylinder gate 1 as used around year 1900 on
cylinder
gate controlled Francis turbines. Such a cylinder gate configuration is not
suitable for
use with a submersible axial flow turbine-generator set because support of the
runner
29 and shaft 30 through the guide vanes 31 is limited by the long load path
from the
draft tube 12 to the nearest point where connection may be made to a shaft-
supporting
bearing 31 while clearing the cylinder gate 1 and its travel path. It should
be noted that
in this prior art example a bearing 32 is required in the draft tube 12 in
order to
adequately support the turbine shaft 30. Such a bearing 32 and associated
support
structure 33 would not be hydraulically acceptable in conjunction with a high
specific
power axial flow hydroturbine, the control of which is enabled by the present
invention.
[0058] Figure 3 shows a prior art large bulb turbine installation in cross
section. Access
for installation, repair and maintenance to such a machine dictates that,
although such
machines may be situated side-by-side, they may not be stacked one atop the
other or
33
CA 02873584 2014-11-13
= in rows one atop the other. The component weight per kilowatt of such a
prior art
. design and the overall length of such a prior art design is a multiple of
that associated
with designs in accordance with the present invention.
[0059] Referring to Figure 4a, cylinder gate 1, operated by hydraulic
cylinders 14 is
shown open. Cylinder gate 1 conforms to generator housing 2 when open.
Cylinder
gate 1 seals at its upstream edge to generator housing 2 when closed as shown
in
Figure 4b. Clearance of 6 mm, for example, may be provided between the
cylinder gate
and the generator for the flow of cooling water. Stay vane 3b lies generally
parallel to
the incoming flow and transitions into guide vane 3a at the location where the
flow
becomes contained between the distributor hub 15 and the distributor shroud
17.
Compliant cylinder gate seat 34 provides a tight seal to the downstream end of
the
cylinder gate 1 when closed as shown in Figure 4b.
[0060] Referring now to Figures 5a and 5c, cylinder gate 1 is shown in the
full open
position. Stay vane portion 3b and guide vane portion 3a of stator vane 3 may
be seen
through the cylinder gate opening. Hydraulic cylinder 14 is shown in its fully
retracted
position.
[0061] Referring now to Figure 5b, 5d and 5e, Cylinder gate 1 is shown in its
fully closed
position while hydraulic cylinder 14 is shown in its fully extended position.
Runner
blades 4 and runner hub 5 are visible in Figure 5e.
34
CA 02873584 2014-11-13
= [0062] Referring now to Figure 6, a submersible turbine generator set
with a high
specific speed Francis runner 18, comprised of hub 5, blades 4 and band 35 is
shown in
conjunction with cylinder gate 1 (shown closed). Because stator vanes 3 are
not
movable as in the case of a conventional prior art Francis turbine guide
vanes, they may
be skewed so as to guide flow radially (as well as tangentially) in order to
control the
radial distribution of velocity entering the runner 18. Draft tube 12 is also
shown.
[0063] Figures 7a and 7b show a powerhouse that incorporates adjustable blade
runners with the blades canted upstream in accordance with an embodiment of
the
present invention and with cylinder gates for shut off. Note that the runner
may be
removed through the draft tube without disassembly or removal of the discharge
rings
11. The draft tubes 12 may be dewatered by means of semi-cylindrical draft
tube
bulkhead 19. The semi-cylindrical form of the bulkhead 19 minimizes bending
moments
on the bulkhead 19 imparted by hydrostatic loads. The open top of bulkhead 19
allows
removal and replacement of runner including blades4 and hub 5 with bulkhead 19
in
place.
[0064] Figure 8 shows turbine generator sets with cylinder gates 1 and
generators 2 in
conjunction with a hydroturbine assembly 37 configured to replace a
submergible radial
gate. Other hydroturbines configured to replace a submergible radial gates are
disclosed in my US application number 11/986,584.
Figures 9a, 9b, and 9c show a high specific speed runner with blades 4, runner
hub 5,
blade levers 6, connecting links 8, spherical joints 7a and 7b, guide pins 10,
and piston
rod 21.
CA 02873584 2014-11-13
' [0065] Referring now to Figure 10 an axial flow pump is shown with impeller
22, diffuser
. vanes 23, motor housing 24, conical gate 25 shown open on the top
half of the drawing
and closed on the bottom half of the drawing.
[0066] Referring now to Figure 11, another pump is shown with conical gate 25,
impeller
22 and diffuser vanes 23. Conical gate 25 is shown open on the top half of the
drawing
and closed on the bottom half of the drawing.
[0067] Referring now to Figure 12, runner hub 5 holding canted blades 4 is
located in
spherical discharge ring 11. Shaft extension 39 is positioned by water
lubricated guide
bearing 38. The main shaft is positioned by upstream guide bearing 40,
downstream
guide bearing 41 and thrust bearing 42. Lifting extension 43 may be
substituted for
shaft extension 39 during machine assembly and disassembly.
[0068] Referring now to Figure 13, a submersible hydroturbine with a cylinder
gate 1
and generator 2 in the draft tube 12 in conjunction with a Francis runner 44.
Such a
machine is useful, for example, for developing power at existing gated
structures where
one or more such machines or an array of such machines may be installed in
series
with the pre-existing water control gates.
[0069] Referring now to Figure 14a, an array of hydroturbines that utilize
flows in either
direction by being rotated 180 degrees about a vertical axis are shown in
cutaway plan
view. The size and weight of such an array of hydroturbines are much less than
the
36
CA 02873584 2014-11-13
. .
= size and weight of a single hydroturbine of equivalent capacity. Making
the facility
. reversible is thus facilitated. Keeping the same optimized geometry for
each direction of
flow provides maximum efficiency in each direction. The use of permanent
magnet
generators operated at variable speed provides high efficiency over a wide
range of
available head, such as may be available in conjunction with a tidal energy
plant.
Figure 14b shows a view of the inlet end of the array of turbines of Figure
14a.
[0070] Referring now to Figures 15a, 15b, and 15c of a hydroturbine with an
adjustable
runner 4,5 with canted blade pivot axes, generator 2 in the draft tube 12, and
a cylinder
gate 1 is shown in the open position shown in exit end view, sectional
elevation view,
and entry end view, respectively. The generator 2 is positioned in the draft
tube 12 by
stay vanes 45. Figures 16a, 16b, and 16c are the same views as Figures 15a,
15b, and
15c, except with the cylinder gate 1 shut.
[0071] Referring now to Figure 17, a hydropower plant is shown with two
staggered
rows of turbines, one above the other. Such an arrangement provides
independent and
direct crane lifting access to both upper and lower machines. The more deeply
submerged machines in the lower row may use higher specific discharge runners
which
benefit from the longer draft tube available to the lower row machines.
[0072] Referring now to Figure 18, an array of hydroturbines installed in a
gate service
stop log slot is shown in conjunction with which air is evacuated from the
water
passageway 48 between the turbine array 47and a downstream control gate 46.
This
37
CA 02873584 2014-11-13
'
= allows operation of the upper row 50 with draft tube submergence, but
with the same
. head as lower row 51. Air evacuation may be by means of naturally
occuring air
entrainment in conjunction with prevention of air leakage, especially at the
seals of gate
46. Alternatively, a vacuum pump 49 such as a liquid ring pump with water as
the
working fluid may be used to evacuate the air from water passageway 48.
[0073] Referring now to Figure 19, the use of multiple air gap axial flux
permanent
magnet generators 50 in conjunction with cylinder gates 1 and mixed flow
runners 44 is
illustrated.
[0074] Referring now to Figures 20a, 20b, 20c and 20d a hydroturbine with the
generator and cylinder gate 1 in the draft tube 12 in conjunction with a fixed
pitch runner
52 is illustrated. The overall length of this configuration is less than for a
machine with
the generator located upstream. The overall length is critical to installing
such
machines into existing structures with limited upstream/downstream space.
[0070] Referring now to Figure 21, the use of an external rotor permanent
magnet
generator in conjunction with hydroturbine in accordance with the present
invention is
illustrated. Permanent magnet rotors 53 are provide for more secure attachment
of
permanent magnets to the rotor than for a similar machine with an internal
rotor. This is
particularly important for over-speed conditions that normally follow a load
rejection.
Cooling of the stator 55 may be readily provided by a heat pipe and stator hub
54 with
wicked surfaces 56 adjacent to the stators 55. Alternatively, water may be
allowed to
circulate within the stator hub 54.
38
CA 02873584 2014-11-13
= [0075] Referring now to Figures 22, 23a, 23b, 23c, 24, 26a, 26b, 26c,
26d, 26e, 27a,
27b, 27c, 27d, and 27e a turbine with a cylinder gate 1 stowed when open
around a
generator 2 located within the draft tube 12 is shown in various views. The
illustrated
machine has a short overall length by virtue of the generator being located
within the
draft tube. The efficiency of the machine is enhanced because the profile loss
at the
end of the runner hub fairing is absent. In lieu of using a runner hub
fairing, the draft
tube 12 works in conjunction with diffuser hub 24 to recover both axial and
tangential
kinetic energy from the water leaving the runner 52. The proportions of the
draft tube
12 and diffuser hub 24 are carefully coordinated to provide a steady and
gradual
change in discharge area from the runner to the draft tube exit in accordance
with
Figure 25, in a manner similar to that provided by an optimized straight
conical draft
tube but with an improved ability to recover residual tangential kinetic
energy from the
runner discharge nearest the runner hub. Highest axial flow turbine
efficiencies
generally occur with at least some residual forward (in the direction of
runner rotation)
swirl. This is because the energy loss on the runner due to drag is
proportional to the
velocity relative to the runner cubed. Designing for a small amount of forward
swirl
results in a net efficiency benefit, even though a portion of the tangential
velocity is not
recovered in a conventional draft tube. Because of conservation of angular
momentum, forward swirl in water leaving the blade tips is largely recovered
because of
the increase in draft tube diameter over its length. The water entering the
draft tube
near the outer wall of the draft tube reaches the end of the draft tube at a
greater radius
than that at which it entered. Its tangential velocity naturally decreases as
it progresses
to a greater radius. Conversely, flow leaving the runner blades nearest the
runner hub
39
CA 02873584 2014-11-13
tries to follow the runner fairing to an ever smaller radius. Any tangential
velocity
= present in the water as it left the blades is multiplied as it tries to
fill the void in the wake
of the runner hub fairing. The energy lost in the resulting vortex results in
runner hub
fairings being truncated to reach the best overall efficiency. Figures 23a,
23b, and 23c
show inlet end, cut-away, and exit end views of the turbine of Figure 22.
Figure 23d
shows velocity triangles at stations 1,2,3,4,and 5 for the turbine of Figures
23a, 23b,
and 23c. Aside from the overall length advantage of the illustrated
hydroturbine
configuration, an efficiency advantage is available as well. Representative
velocity
triangle are illustrated for various station along the length of the machine.
Both hub and
tip tangential velocities are reduced by the diffuser comprised of the draft
tube 12 and
the diffuser hub 24. Diffuser vanes 23 are located in a zone of sufficiently
low velocity
so as to not themselves contribute significant losses to the machine. They
provide an
efficiency benefit be straightening the flow so that as the flow follows the
generator
fairing 56 there is no more tangential component that would result in a
tangential
acceleration and loss of energy. Figure 24 shows cross sections of the turbine
of
Figures 22 and 23a, 23b, and 23c. Coordination of dimensions between the
difusser
fairing, the conical portion of draft tube 12, the round-to-square portion of
draft tube 12,
the generator fairing 56 and the diffuser vanes 23 results in an increase in
area gradual
enough to prevent flow separation within the draft tube. Optionally, vortex
generating
vanes or texture may be used just upstream of the generator fairing 56 in
order to re-
energize the boundary layer at this location. Figure 25 shows approximate
water
passageway area as a function of axial position through the water turbine of
Figures 22,
23a ,23b, and 23c. Figure 26 shows the water turbine of Figures 22, 23a,23b,
and23c
CA 02873584 2014-11-13
. =
= with the cylinder gate open. Figure 27 shows the water turbine of Figures
22, 23a,23b,
and23c with the cylinder gate closed. Figure 28 shows the inlet end of an
array
comprised water turbines similar to the one shown in Figures 22, 23a, 23b, and
23c.
Figure 29 shows the outlet end of an array comprised water turbines similar to
the one
shown in Figures 22, 23a, 23b, and 23c.
41
