Patent Application
20140301823
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 claim 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 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.
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-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.
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.
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:
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.
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 113 442.9 | Sep 2011 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/002677 | 6/26/2012 | WO | 00 | 6/30/2014 |
