Note: Descriptions are shown in the official language in which they were submitted.
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HYDRAULIC MACHINE HAVING AN INTAKE MANIFOLD LOCATED AT THE TOP
The invention relates to a hydraulic machine, especially a pump turbine
according
to the preamble of claim 1 or 2. The invention further relates to a method for
filling or discharging such a machine according to claims 6 or 7 and its
preferred
use according to claim 9.
Pump turbine systems used in hydroelectric power plants have two operating
modes, namely a turbine mode and a pump mode. In the latter, the pump pumps
water from a lower basin into an upper basin and is driven for this purpose by
an
electrical machine which is in drive communication with the pump. The
electrical
machine is fed from a public power supply grid, i.e. it is supplied with
electrical
power. In turbine mode on the other hand, the water flowing from the upper
basin through the turbine into the lower basin drives the turbine which
transmits a
corresponding power to the electrical machine. The electrical machine converts
the drive power into electrical power and feeds this into the power supply
grid.
The electrical machine thus operates on one occasion as a generator and on
another occasion as a motor. It is therefore also designated as a motor-
generator.
In contrast to the aforesaid generic pump turbine systems, reversible pump
turbine systems have also become known in which the turbine and pump are
formed by a common blade wheel so that in turbine mode the common blade
wheel is acted upon with water from the upper basin to generate electrical
power
and in pump mode it is driven by the electrical machine.
Since such pump storage power plants are used to compensate for load peaks in
the power supply grid, the pump turbine must be put into a position to deliver
turbine power as rapidly as possible in order to support the power supply grid
or
to rapidly receive pump power in order to be used for primary grid regulation.
It is
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therefore desirable that the pump turbine of a pump storage power plant can be
put into pump mode as rapidly as possible and conversely.
In the transition from the operating mode of phase shifting to the operating
mode
of pump or turbine operation, it is necessary to fill the drained blade wheel.
The
draft tube bend is usually located at the bottom, so that the water level can
be
lifted until complete discharging by purposeful ventilation. If the draft tube
bend is
situated above the pump on the other hand, its rapid filling would lead to
uncontrolled filling of the blade wheel however.
It is now advantageous for a smooth filling process if the rotating blade
wheel is
filled to the highest possible extent by the headwater pressure from the high-
pressure side. This is usually no problem in the case of a conventional
arrangement of the draft tube bend because the air in the draft tube bend
would
not escape. In the case of a draft tube bend situated at the top however, the
entire air would escape immediately during opening of the closing valve on the
tailwater side, so that controlled filling would no longer be possible. The
opening
of a closing valve on the high-pressure side such as a guide apparatus, a ring
gate, a rotary valve or the like would lead to a considerable safety risk if
the
closing valve on the tailwater side was simultaneously kept closed. This would
lead
to the likelihood that the entire draft tube bend would be subjected to the
high
headwater pressure if load shedding occurred for example during the filling
process in which the tailwater closing valve was still closed.
On the other hand, it is necessary during the transition from the operating
mode
of pump operation to the operating mode of phase shifting to discharge the
filled
blade wheel. The draft tube bend is usually situated at the bottom, so that
the
water level can be lowered in a controlled fashion by means of purposeful
aeration. This was not possible until now by a draft tube bend situated above
the
pump.
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It is the object of the present invention to solve the problems as mentioned
above
and to provide a pump turbine system which permits a controlled, rapid and
reliable filling of the blade wheel from the high-pressure side with a draft
bend
tube arranged above the blade wheel without giving rise to the likelihood that
the
draft tube bend is subjected to the high headwater pressure. At the same time,
this solution shall be easy to implement and to be realized at low cost.
This object is achieved by a pump turbine according to the characterizing
features
of claim 1 and claim 5.
It is a relevant feature of the system in accordance with the invention that
the
draft bend tube is arranged above the blade wheel and at least one bypass pipe
is
provided for bypassing the guide and/or closure apparatus, which bypass pipe
connects the inlet spiral directly to the blade wheel when a bypass valve
arranged
in the run of said bypass pipe is opened. The blade wheel can be filled in a
purposeful way by these bypass pipes by bypassing the closed guide and/or
closure apparatus. It is thus possible by providing the system with a ring
gate for
example to keep the inlet spiral continuously subject to the headwater
pressure,
which considerable increases the operational lifespan and further minimizes
the
times required for operational transitions, since the spiral need not be
filled or
discharged. There can be one or several of the bypass pipes, which after the
closing valves is opened directly into the machine before or after the guide
apparatus, preferably into the lateral space of the blade wheel, so that the
flow
channel is not disturbed by installed parts or openings. A bypass pipe ideally
opens into an upper and/or lower turbine or pump cover. The bypass pipes can
also be arranged in the annular space between the ring gate and the guide
apparatus. In this case, the guide apparatus can be closed for
discharging/aerating or filling/ventilating, or it can be larger in an
intermediate
position than in the closed position.
The bypass pipe can directly be connected to the inlet spiral via a valve.
Preferably, the cross-section of the bypass pipe is chosen smaller than the
cross-
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section of the ventilation pipe in the draft bend tube, so that in the case of
load
shedding for example during the filling process no impermissible pressure
increase
can occur in the draft bend tube. The valve in the bypass pipe must be locked
in
such a way that it can only be opened after the opening of the ventilation
valve in
the draft bend tube and is already closed before the closing of the
ventilation
valve.
The pump blade wheel can be filled via the bypass pipe during the operation of
the machine as is possible by the headwater pressure. The small remainder can
be
filled from the suction side.
It is a further relevant item of the system in accordance with the invention
that
the draft bend tube is arranged above the blade wheel and at least one
discharge
pipe is provided for discharging the blade wheel, which connects the blade
wheel
directly to a pump sump when a discharge valve arranged in the course of this
discharge pipe is opened. The blade wheel can thus be drained when the closing
valves on the tailwater side and the headwater side are closed.
The arrangement in the lateral space of the blade wheel prevents the
positioning
of installed parts or openings in the flow channel. There also may be several
discharge pipes, ideally on the bottom, upper or both turbine or pump covers.
Preferably, they have a smaller cross-section than the aeration pipes, so that
no
negative pressure is produced in the blade wheel space which would counteract
continuous discharging.
Discharge pipes lead to the pump sump. As a result of the arrangement of the
discharge pipes in the lateral space of the blade wheel, it is further
possible to
utilize the full pump pressure for discharging, so that discharging periods
can be
minimized. As a result of the arrangement in the lateral space of the blade
wheel,
a ring gate can simultaneously be used for example to separate the blade wheel
space from the spiral so that the inlet spiral does not require discharging.
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The system in accordance with the invention is not principally limited to the
sole
attachment of one type of pipe, but may comprise any desired number and
combination of both bypass pipes and discharge pipes as required.
5
The present invention will be explained below in closer detail by reference to
an
embodiment shown in the enclosed drawings. The same or similarly acting parts
are provided the same reference numerals. The drawings show as follows:
Fig. 1 shows a side view of a pump turbine of Francis configuration in
accordance
with the invention, comprising a blade wheel which is rotatably held about a
rotational axis, and an inlet spiral which surrounds said blade wheel in a
ring-like
manner, and a draft bend tube situated above the blade wheel, and
Fig. 2 shows an intersected side view of a part of the pump turbine in
accordance
with the invention according to Fig. 1 in order to illustrate the position of
the
bypass pipes and the discharge pipes.
Fig. 1 shows a side view of a pump turbine 10 of Francis configuration in
accordance with the invention, comprising a blade wheel 20 (not shown) which
is
rotatably mounted about a rotational axis R, and an inlet spiral 30 which
surrounds said blade wheel 20 in a ring-like manner, and a draft tube bend 50
which is situated above the blade wheel 20. In such a pump turbine 10, the
water
flows into the blade wheel 20 radially to the rotational axis R from an outlet
opening present on the inner circumference of the inlet spiral 30. In the
blade
wheel 20, the water is deflected upwardly under the release of energy in the
direction of the rotational axis R, while the blade wheel 20 is made to
rotate. The
water is then supplied via the draft bend tube 52 to a draft tube connected
thereto (not shown).
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It is now necessary to fill the discharged blade wheel in the transition from
the
operating mode of phase shifting to the operating mode of pump turbine
operation. The draft tube bend is usually situated at the bottom, so that the
water
level can be lifted until complete discharging by purposeful ventilation. If
the draft
tube bend is situated above the pump on the other hand, its rapid filling
would
lead to uncontrolled filling of the blade wheel however.
On the other hand, it is necessary during the transition from the operating
mode
of pump operation to the operating mode of phase shifting to discharge the
filled
blade wheel. The draft tube bend is usually situated at the bottom, so that
the
water level can be lowered in a controlled fashion by means of purposeful
aeration. This was not possible until now by a draft tube bend situated above
the
pump.
Fig. 2 shows an intersected side view of a part of the pump turbine 10 in
accordance with the invention according to Fig. 1 in order to illustrate the
position
of the bypass pipes 60.1, 60.2 and the discharge pipes 70.1, 70.2. The bypass
pipes 60.1, 60.2 bypass a guide and closure apparatus 40 and open into a
bottom
and upper turbine or pump cover. The guide and closure apparatus 40 can
consist
of guide blades 40.1 and a ring gate 40.2. In the case of a closed ring gate
40.2
for example, the blade wheel 20 can thus be filled in a virtually rapid and
continuous manner from the high-pressure side, wherein the air is discharged
via
a ventilation pipe (not shown). The cross-sections of the bypass pipes 60.1,
60.2
are preferably smaller than those of the discharge pipes in order to prevent
overpressure in the blade wheel space.
Conversely, the blade wheel 20 can be discharged via the discharge pipes 70.1,
70.2 in the case of closing valves which are closed on the high-pressure and
low-
pressure side, wherein an aeration pipe (not shown) is opened. The cross-
sections
of the discharge pipes 70.1, 70.2 are also preferably smaller than those of
the
aeration pipes in order to prevent negative pressure in the blade wheel space.
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Both the bypass pipes 60.1, 60.2 as well as the discharge pipes 70.1, 70.2 are
equipped with valves which enable reliable opening and closing. Both types of
pipes can be implemented easily from a constructional standpoint and can
therefore be realized at low cost. The valves can consequently be triggered
depending on other closing valves on the high-pressure and low-pressure side,
e.g. by means of computer-implemented or numerical controls in order to
perform
filling the blade wheel 20 with water or discharging the same. The spiral 30
need
not be relieved and is drained in any of the two cases, which represents a
considerable reduction in the time used for changing over between phase
shifting
and pump or turbine operation. At the same time, the operational lifespan of
the
pump turbines will increase considerably.
Although the present invention was described with reference to a pump turbine,
it
can principally also be realized only in a pump or only in a turbine if rapid
filling or
drainage is required. The advantages in accordance with the invention can also
be
observed therein. Adaptations to the cross-section and the number and
combination of bypass pipes and discharge pipes required in the special case
are
included in the knowledge and expertise of the person skilled in the art.
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List of reference numerals
Pump turbine
5 20 Blade wheel
30 Inlet spiral
40 Guide and/or closure apparatus
40.1 Guide blades
40.2 Ring gate
10 50 Draft tube bend
60.1, 60.2 Bypass pipe
70.1, 70.2 Discharge pipe
Rotational axis
