Hydraulic machinery and its control method

Abstract

To provide a hydraulic machine capable of suppressing vibration or noise during activation, and a control method therefor.SOLUTION: A hydraulic machine comprises: a flowmeter that measures a flow rate of water flowing into a runner; and a control device that determines, based on the flow rate, whether to open or close an air supply valve that supplies or cuts off air to an air supply pipe that supplies air to a suction pipe provided downstream of the runner. The control device controls the air supply valve to open when it determines that the flow rate is equal to or larger than a first reference value during transient operation from operation stop to normal operation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a hydraulic machine and a control method thereof.

Background Art

[0002] Hydraulic machines such as general Francis turbines change the flow area by controlling the opening degree of guide vanes provided on the upstream side of the runner, and adjust the flow rate of water flowing from the upper pond side to the runner. When operating the hydraulic machine at a partial load, the guide vanes are set to an opening degree smaller than that during rated operation. Therefore, water may flow backward from the downstream side of the draft tube toward the runner due to the rotation of the runner, and vibration and noise may occur. In order to prevent such vibration and noise, air may be supplied from an air supply pipe into the draft tube to generate a cavity at the axial center part of the runner outlet, thereby suppressing cavitation and backflow.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] While turbine runners are designed to match the flow rate during normal operation, including rated and partial load operation, the water flow rate through the turbine is extremely low during startup, transitioning from shutdown to normal operation. This means that during startup, a small water flow rate, too low to match the runner's design, is more likely to occur, leading to increased cavitation and backflow due to runner rotation, potentially causing more vibration and noise than during normal operation. Vibration and noise caused by cavitation and backflow can put a load on the runner, potentially leading to runner failure. Furthermore, the water flow rate changes significantly during turbine startup, and fluctuations in water levels in the upper and lower reservoirs also greatly affect the water flow rate, making it difficult to supply air to the draft pipe at the appropriate time during startup.

[0005] The problem that this invention aims to solve is to provide a hydraulic machine and a control method therefor that can suppress vibration and noise during startup. [Means for solving the problem]

[0006] To solve the above problems, the hydraulic machine of the embodiment includes a flow meter for measuring the flow rate of water flowing into a runner, and a control device for determining, based on the flow rate, whether to open or close an air supply valve that supplies or shuts off air to an air supply pipe that supplies air to a suction pipe located downstream of the runner. The control device controls the air supply valve to open when it determines that the flow rate is equal to or greater than a first reference value during transient operation from shutdown to normal operation. [Brief explanation of the drawing]

[0007] [Figure 1] A cross-sectional view showing the configuration of a hydraulic machine according to the first embodiment. [Figure 2] A flowchart illustrating an example of the process of starting up a hydraulic machine according to the first embodiment from shutdown to rated operation. [Modes for carrying out the invention]

[0008] (First Embodiment) The first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a meridional cross-sectional view of the hydraulic machine according to this embodiment. Here, a Francis turbine will be described as an example of a hydraulic machine. The Francis turbine 1 comprises an iron pipe 10, a casing 12, stay vanes 14, guide vanes 16, a runner 18, a main shaft 20, a generator 22, a draft pipe 24, an air supply pipe 26, an air supply valve 28, a flow meter 30, and a control device 32. The Francis turbine 1 is electrically connected to a power system (not shown). This electrical connection is opened and closed by a circuit breaker (not shown) installed between the Francis turbine 1 and the power system. In the following description, the generator 22 side will be considered as the direction upward of the rotation axis C, and the draft pipe 24 side will be considered as the direction downward of the rotation axis C.

[0009] The iron pipe 10 is a water channel through which water flows, connecting the upper reservoir (not shown) and the casing 12, which will be described later. The iron pipe 10 is equipped with an inlet valve (not shown) that, when closed, stops the flow of water between the upper reservoir and the casing 12, and a flow meter 30, which will be described later.

[0010] The casing 12 is arranged in a spiral shape on the outer circumference of the runner 18, which will be described later, and supplies water, which is the working fluid that flows in from the upper reservoir through the iron pipe 10, to the runner 18 via the stay vanes 14 and guide vanes 16 (both described later). The casing 12 is usually formed so that its cross-sectional diameter gradually decreases from the beginning of the winding (upper reservoir side) to the end of the winding (runner 18 side).

[0011] Multiple stay vanes 14 are arranged on the inner circumference side of the casing 12 and at predetermined intervals in the circumferential direction (hereinafter referred to as the circumferential direction) with respect to the rotation axis C of the main shaft 20, which will be described later. A water flow channel is formed between adjacent stay vanes 14.

[0012] Multiple guide vanes 16 are arranged on the inner circumference of the stay vane 14 and the outer circumference of the runner 18 at predetermined intervals in the circumferential direction. Each guide vane 16 is rotatable, and by controlling its opening degree, the flow area of ​​the flow channel formed between adjacent guide vanes 16 can be changed. Therefore, by controlling the opening degree of the guide vanes 16, the flow rate of water flowing into the runner 18, as described later, can be adjusted.

[0013] The runner 18 is positioned on the inner circumference of the guide vane 16, rotatably arranged around the rotation axis C, and is connected to the generator 22 via the main shaft 20. The main shaft 20 is the rotation axis of the runner 18, and the generator 22 is connected to it. During turbine operation, the rotational energy of the runner 18 is transmitted to the generator 22 via the main shaft 20, causing the generator 22 to generate electricity.

[0014] Furthermore, the generator 22 may also function as an electric motor and be configured to rotate the runner 18 when power is supplied. In this case, water from the lower pond (not shown) can be drawn up via the suction pipe 24 (described later) and discharged into the upper pond, making it possible to operate the Francis turbine 1 as a pump turbine.

[0015] The suction pipe 24 is located downstream of the runner 18 (downward along the rotation axis C) and supplies water flowing in from the runner 18 to the lower reservoir (not shown).

[0016] The air supply pipe 26 is a passage for supplying air to the suction pipe 24, and is equipped with an air supply valve 28 that, when closed, shuts off the supply of air from the air supply pipe 26 to the suction pipe 24. The air supplied by the air supply pipe 26 to the suction pipe 24 may be atmospheric pressure air or high-pressure air pressurized by a compressor or the like.

[0017] The flow meter 30 is installed in the iron pipe 10 and measures the flow rate of water flowing from the iron pipe 10 to the casing 12. The flow meter 30 only needs to be able to measure the flow rate of water flowing into the runner 18, and its installation location is not limited to the iron pipe 10; for example, it could be installed in the casing 12 or another location.

[0018] The control device 32 is connected to the guide vane 16, the air supply valve 28, and the flow meter 30. The control device 32 receives a flow rate measurement signal related to the water flow rate from the flow meter 30. When controlling the guide vane 16 and the air supply valve 28, it transmits a control signal to a drive device (not shown), and the drive device opens and closes the guide vane 16 and the air supply valve 28 according to the signal. The control device 32 is also connected to an opening degree detection device (not shown) provided on the guide vane 16 and the air supply valve 28 to detect their opening and closing. Based on the opening degree detection signal sent from this opening degree detection device, the control device 32 can determine the open / closed state of the guide vane 16 and the air supply valve 28. The control device 32 may be connected to the guide vane 16, the air supply valve 28, and the flow meter 30 by wire using cables, etc., or by wireless connection using communication, etc.

[0019] The following describes the water flow in a Francis turbine 1 during normal operation. At this time, the guide vanes 16 are open and the air intake valve 28 is fully closed. First, water from the upper reservoir is supplied to the runner 18 by sequentially passing through the iron pipe 10, inlet valve, casing 12, stay vanes 14, and guide vanes 16. When the runner 18 rotates due to the work done by this water, its rotational energy is transmitted to the generator 22 via the main shaft 20 to generate electricity. After the work has been done by the runner 18, the water flows through the suction pipe 24 and is supplied to the lower reservoir (not shown).

[0020] In the following description of this embodiment, the operating state of the Francis turbine 1 will be described by classifying it based on the rotational speed of the runner 18. Specifically, the operating state with a rotational speed of zero is called the stopped operation, the operating state with a rotational speed less than the reference rotational speed is called the transient operation, and the operating state with a rotational speed greater than or equal to the reference rotational speed is called the normal operation. In particular, among the normal operations, the state of operating at the rated rotational speed, which is the rotational speed of the runner 18 set to the maximum output of the Francis turbine 1, is called the rated operation. In the stopped operation and the transient operation, the Francis turbine 1 and the power system are electrically disconnected. On the other hand, in the normal operation, the Francis turbine 1 and the power system are electrically connected, and the generated power is supplied from the Francis turbine 1 to the power system as described above.

[0021] Note that depending on the operating states before and after, there may be a case where the rotational speed of the runner 18 is not zero but the runner 18 is idling during the stopped operation.

[0022] Note that since the rotational speed of the runner 18 depends on, for example, the flow rate of the water flowing into the runner 18, the operating state of the Francis turbine 1 can be controlled by adjusting the opening degree of the guide vane 16.

[0023] Note that the operating state of the Francis turbine 1 may be classified based on, for example, the flow rate of water.

[0024] Next, a control example when starting the Francis turbine 1 from the stopped operation to the rated operation will be described with reference to FIG. 2. Here, when a command to start the Francis turbine 1 is input, the guide vane 16 and the air supply valve 28 are in a fully closed state.

[0025] First, the administrator inputs a rated operation command to the control device 32 of the Francis turbine 1 that is in the stopped operation (S100).

[0026] Next, the control device 32 transmits a control signal to open the guide vanes 16, and the guide vanes 16 begin to open (step S102). When the guide vanes 16 begin to open, the water that has passed through the guide vanes 16 flows into the runner 18, and the runner 18 begins to rotate, entering a transient operation state.

[0027] Next, the control device 32 receives the flow rate of water flowing into the runner 18 from the flow meter 30 and determines whether the flow rate is equal to or greater than a first reference value (step S104). The first reference value is the flow rate at which the Francis turbine 1 will enter transient operation, and steps S104 and S106 are performed during transient operation when the Francis turbine 1 is not connected to the power grid.

[0028] If the control device 32 determines that the flow rate is equal to or greater than the first reference value (YES in step S104), the control device 32 outputs a control signal to the drive unit to fully open the air intake valve 28 and open the air intake valve 28 (step S106). On the other hand, if the control device 32 determines that the flow rate is less than the first reference value (NO in step S104), the control device 32 continues to determine the flow rate until the flow rate becomes equal to or greater than the first reference value.

[0029] After step S106, the control device 32 receives the flow rate of water flowing into the runner 18 from the flow meter 30 and determines whether the flow rate is equal to or greater than the second reference value (step S108). The second reference value is the flow rate at which the Francis turbine 1 operates normally, and steps S108 and S110 are performed during normal operation when the Francis turbine 1 is connected to the power grid.

[0030] If the control device 32 determines that the flow rate is equal to or greater than the second reference value (YES in step S108), the control device 32 outputs a control signal to the drive unit to completely close the air supply valve 28, closing the air supply valve 28 and transitioning to rated operation (step S110). On the other hand, if the control device 32 determines that the flow rate is less than the second reference value (NO in step S108), the control device 32 continues to determine the flow rate until the flow rate becomes equal to or greater than the second reference value.

[0031] Furthermore, the guide vane 16 may continue opening from step S102 to S110, or, for example, while controlling the air supply valve 28 in steps S106 and S110, it may stop opening and maintain a constant opening until the control is completed.

[0032] Furthermore, the second standard value in step S108 should be set to a flow rate that is sufficient to keep vibration and noise within acceptable limits even when the air supply is stopped, and is not limited to whether or not it corresponds to rated operation.

[0033] During transient operation when the water flow rate is low at the start of the turbine, vibrations and noise may occur due to cavitation and backflow associated with the rotation of the runner 18, which do not occur during normal operation. Therefore, as described above, when the water flow rate exceeds the first standard value, the air supply valve 28 is opened to supply air and suppress vibrations and noise to prevent failure of the runner 18. On the other hand, during normal operation when the water flow rate is sufficiently large, such vibrations and noise are unlikely to occur, so the air supply valve 28 is closed to stop air supply when the water flow rate exceeds the second standard value.

[0034] In this way, by controlling the Francis turbine 1 to prevent cavitation and backflow associated with the rotation of the runner 18 during startup, vibration and noise can be suppressed not only during normal operation but also during transient operation at startup, further reducing the possibility of runner 18 failure. In particular, runner 18, which is designed based on the flow rate during normal operation, is more likely to generate vibration and noise during transient operation when the water flow rate is lower than during normal operation. Suppressing vibration and noise during transient operation further reduces the possibility of runner 18 failure. In addition, during transient operation, the flow rate changes over time, and the flow rate may differ even with the same guide vane 16 opening due to changes in the head between the upper and lower reservoirs, and this fluctuation is larger than during normal operation. Therefore, by using the flow rate measured by the flow meter 30 as a reference, the air supply valve 28 can be controlled at the appropriate timing, and vibration and noise can be suppressed more effectively.

[0035] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0036] 1...Francis turbine, 10...Iron pipe, 12...Casing, 14...Stay vane, 16...Guide vane, 18...Runner, 20...Main shaft, 22...Generator, 24...Draw-out tube, 26...Air intake pipe, 28...Air intake valve, 30...Flow meter, 32...Control device.

Claims

1. A flow meter that measures the flow rate of water flowing into the runner, The system includes a control device that determines, based on the flow rate, whether to open or close an air supply valve that supplies or shuts off air to an air supply pipe that supplies air to an air supply pipe located downstream of the runner, The control device controls the hydraulic machine to open the air supply valve when it determines that the flow rate is equal to or greater than a first reference value during transient operation from shutdown to normal operation.

2. The hydraulic machine according to claim 1, wherein the control device controls the opening of a guide vane provided on the upstream side of the runner when starting up from the stop of operation.

3. The hydraulic machine according to claim 1, wherein the control device controls the air supply valve to close when it determines that the flow rate is greater than or equal to a second reference value, which is greater than the first reference value, during normal operation.

4. A step of measuring the flow rate of water flowing into the runner, A control method for a hydraulic machine, comprising the step of starting to supply air to a suction pipe provided downstream of the runner when it is determined that the flow rate is equal to or greater than a first reference value during transient operation from shutdown to normal operation.

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