JP4169656B2 - Drainage station and its operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drainage station for transferring water from a small and medium river to a large river and a method for operating the drainage station, and more particularly to a drainage station capable of preventing the occurrence of vibration due to a water channel resonance phenomenon during operation of the drainage station and the method thereof. It relates to the driving method.
[0002]
[Prior art]
When the amount of precipitation increases during a typhoon, the water level of rivers, especially small and medium rivers, increases and sometimes the rivers overflow. As a facility for preventing such flooding of a river, a drainage station for transferring water flowing through the river to a large river is known. This type of drainage station is usually constructed near a river, and structures such as waterways, pedestals for installing pumps and prime movers, and building foundations for accommodating prime movers are generally made of reinforced concrete.
[0003]
An example of the overall configuration of a conventional drainage station is shown in FIG. The drainage station drives the structure 1 made of reinforced concrete, the suction channel 2 and the discharge channel 3 formed in the structure 1, the pump 4 for transferring water from the suction channel 2 to the discharge channel 3, and the pump 4 A prime mover 5 and a building 6 that houses the prime mover 5 and the like are provided. The suction port of the pump 4 is connected to the suction water channel 2, and the discharge port of the pump 4 is connected to the discharge water channel 3.
[0004]
The suction channel 2 communicates with a river (medium and small rivers) through a water conduit or the like, and the river water is introduced into the suction channel 2 by operating the sluice 21. On the other hand, the discharge water channel 3 communicates with a large river through a drainage channel or the like. Then, by driving the pump 4, the river water is sucked in through the suction water channel 2, and the water is transferred to the large river through the discharge water channel 3. In the suction water channel 2, a closed water channel 7 is formed in the vicinity of the pump, and in the discharge water channel 3, a closed water channel 8 is formed in the vicinity of the pump. In the present invention, the closed water channel means a water channel in which the periphery of the flow channel is sealed.
[0005]
In such a drainage station, an excitation force is generated by the operation of the pump 4, and the water in the water channel is excited by the excitation force. For this reason, when the excitation frequency of the excitation force matches the natural frequency of water in the water channel, a resonance phenomenon occurs in the water channel, which greatly vibrates the ground and causes vibration of the drainage field. Furthermore, there is a problem that the vibration of the ground propagates to the surroundings and vibrates neighboring private houses. Particularly in recent years, due to the increase in population, many houses have been built around the drainage station, and such vibration caused by the resonance phenomenon has become a big problem. In the present invention, the natural frequency of water in the water channel means the resonance natural frequency of water existing in the water channel on the suction port side or the discharge port side of the pump.
[0006]
In order to solve such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-329099, the coincidence between the excitation frequency (excitation frequency) and the natural frequency of water in the water channel is avoided. In addition, a method for designing a drainage station and a method for reducing the excitation force generated in the drainage station by installing a pump at a position that becomes a node of the fluctuating pressure mode of water in the water channel have been proposed.
[0007]
In the above method, when designing the drainage station, first, the number of impellers of the pump and the rotational speed of the pump are determined in consideration of the pump efficiency, etc., and the shape and length of the water channel are considered in consideration of fluid dynamics. decide. Next, the excitation frequency of the pump is calculated based on the number of impellers of the pump and the rotational speed of the pump, and the natural frequency of water in the water channel is calculated from the shape and length of the water channel using the finite element method, etc. Use to calculate. Then, compare the calculated excitation frequency with the natural frequency, and if the two values are far enough to avoid the coincidence between the excitation frequency and the natural frequency, design the drainage station. Terminate.
[0008]
On the other hand, if the excitation frequency and natural frequency are relatively close and it is determined that there is a risk of resonance, change the pump design or water channel design and recalculate the excitation frequency and natural frequency. Then, design changes and calculations are performed until the two values are sufficiently separated. If the above two values cannot be sufficiently separated due to various circumstances, a pump is installed at a position that becomes a node of the fluctuating pressure mode of the water in the channel. The above-described vibration problem has been solved by designing the drainage station using such a method.
[0009]
However, in reality, the equivalent sound velocity in water in the waterway varies greatly depending on the water temperature, the bubble content in the water, the earth and sand content in the water, etc., so the natural vibration of the water in the waterway even during operation of the drainage station. The number changes. The excitation force generated by the pump operation is also due to fluid elements such as separation vortices generated on the blade surfaces inside the pump. Therefore, the excitation frequency of the excitation force depends on the number of blades and rotation of the impeller. In addition to the speed, it varies depending on the pump operating conditions such as the amount of discharged water. For this reason, even if the drainage station is manufactured as designed, under the operating conditions that were not predicted at the time of design, the channel resonance may be excited and vibration problems may occur. Actually, there are many cases where such a problem occurs in the conventional drainage station. When a vibration problem occurs in the drainage station, it is necessary to investigate the cause of the vibration and work on countermeasures according to the structure of the drainage station. For this reason, there has been a strong demand for a drainage station that can respond to actual operating conditions and avoid resonance.
[0010]
[Patent Document 1]
JP-A-9-329099 [0011]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described conventional problems, and even when the drainage station is in an operating state exceeding the prediction at the time of design, it is possible to prevent the occurrence of vibrations that cause various problems. The purpose is to provide a drainage station.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides a water channel connected to a suction port or a discharge port of a pump, a gas chamber disposed in a closed water channel of the water channel, and a volume for changing the volume of the gas chamber. Measuring means for controlling the volume changing means based on the natural frequency of water in the water channel, vibration means for vibrating the water in the water channel, and measuring the pressure of water in the water channel Pressure measuring means for measuring the pressure pulsation of water in the water channel vibrated by the vibrating means, and the control means based on the measured value of the pressure measuring means The drainage station is configured to obtain a natural frequency of water in the water channel .
[0013]
Before SL pressure measuring means, it is preferable to measure the pressure pulsation of the water in said water passage at the time the pump is stopped.
In a preferred aspect of the present invention, the control means determines that resonance has occurred when the magnitude of the pressure pulsation of water in the water channel is greater than a predetermined threshold, and It is configured to change the volume of the gas chamber. In this case, the control means determines that resonance has occurred when the magnitude of the pressure pulsation of the water in the water channel is greater than a predetermined threshold during pump operation. It is preferable to change the volume of the gas chamber.
[0014]
In general, the presence of a gas mass, for example, an elastic body such as a rubber balloon filled with gas inside, is constantly present in the water in the closed water channel, and the volume of the water in the closed water channel is changed. The frequency can be changed. Further, in the drainage station, the vicinity of the suction port and the discharge port of the pump is usually configured as a closed water channel. From this viewpoint, the present invention includes a gas chamber disposed in the water of a closed channel as a configuration corresponding to the gas mass.
[0015]
According to the present invention, the natural frequency of water in the water channel can be changed by changing the volume of the gas chamber. Therefore, the natural frequency of water in the water channel can be separated from the excitation frequency of the excitation force generated by the pump operation, thereby avoiding the occurrence of a water channel resonance phenomenon. Furthermore, according to the present invention, since the natural frequency of water in the water channel can be changed arbitrarily and at any time, the excitation frequency and the natural frequency of water in the water channel itself changed during the operation of the drainage station. Even in this case, the occurrence of resonance in the water channel can be prevented.
[0016]
That is, it is not a method of avoiding resonance by predicting the excitation frequency of the pump and the natural frequency of water in the waterway as in the past, and avoiding resonance, but the state of the drainage station during operation of the drainage station The drainage station is configured so that the natural frequency of the water in the waterway can be moved away from the excitation frequency as much as necessary. Thereby, generation | occurrence | production of the resonance in a water channel can be prevented and the vibration of a drainage station can be prevented. In addition, the closed water channel as used in the field of this invention means the water channel by which the circumference | surroundings were sealed among the flow paths of water.
[0017]
Another aspect of the present invention is a method of operating a drainage station including a water channel connected to a suction port or a discharge port of a pump, wherein water in the water channel is vibrated to generate pressure from the pressure pulsation of the water channel. The natural frequency of the water in the water is obtained, the natural frequency is compared with the predicted excitation frequency of the pump, and when the natural frequency matches the excitation frequency, the water channel is closed. The pump is started after the volume of the gas chamber arranged in the water channel is changed to move the natural frequency away from the excitation frequency.
[0018]
According to the present invention, since the coincidence between the excitation frequency of the excitation force and the natural frequency of water in the water channel can be avoided, the pump can be started without causing a water channel resonance phenomenon. In the present invention, the coincidence between the excitation frequency and the natural frequency means not only the case where both values are completely coincident but also the case where both values are close enough to cause a resonance phenomenon.
[0019]
In another preferred aspect of the present invention, when the pulsation of water occurs during the operation of the pump and the pulsation of the natural frequency is generated by the operation of the pump, the volume of the gas chamber is changed to change the volume of the gas chamber. Pulsation is reduced by changing the natural frequency and avoiding resonance.
According to the present invention, the operation of the pump (drainage station) can be continued without causing waterway resonance.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of a drainage station that is an embodiment of the present invention.
As shown in FIG. 1, the drainage station has a structure 1 made of reinforced concrete, a suction channel 2 and a discharge channel 3 formed in the structure 1, and a pump 4 that transfers water from the suction channel 2 to the discharge channel 3. And a prime mover 5 that drives the pump 4 and a building 6 that houses the prime mover 5 and the like. The suction port 4 a of the pump 4 is connected to the suction water channel 2, and the discharge port 4 b of the pump 4 is connected to the discharge water channel 3.
[0021]
The suction water channel 2 communicates with a river (medium and small rivers) through a water conduit or the like, and the water of the river is introduced into the suction water channel 2 by operating the sluice 21. On the other hand, the discharge water channel 3 communicates with a large river through a drainage channel or the like. When the pump 4 is driven by the prime mover 5, river water is sucked into the pump 4 through the suction channel 2, and water is transferred to the major river through the discharge channel 3. In the suction water channel 2, a closed water channel portion 7 is formed in the vicinity of the pump 4, and in the discharge water channel 3, a closed water channel portion 8 is formed in the vicinity of the pump 4. That is, the suction port 4 a of the pump 4 communicates with the closed water channel portion 7, and the discharge port 4 b of the pump 4 communicates with the closed water channel portion 8. In the present invention, the closed water channel means a water channel in which the periphery of the flow channel is sealed.
[0022]
In FIG. 1, in the closed water channel portion 7 of the suction water channel 2, an underwater speaker (vibration means) 11 for exciting the water in the suction water channel 2 to a position where the water is always submerged during steady operation, and the suction water channel 2. A pressure sensor (pressure measuring means) 12 for measuring the pressure of water is arranged. These underwater speaker 11 and pressure sensor 12 are connected to a computer (control means) 17. When the pump 4 is stopped, the pressure of the water in the suction channel 2 vibrated by the underwater speaker 11 is measured by the pressure sensor 12, and the measured value is transmitted as a signal from the pressure sensor 12 to the computer 17. In the computer 17, the natural frequency of water in the suction channel 2 is obtained based on the signal transmitted from the pressure sensor 12.
[0023]
In the vicinity of the suction port 4 a of the pump 4, an air tank (gas tank) 13 disposed in the closed water channel portion 7 is provided. The air tank 13 communicates with the closed water channel portion 7, and water in the closed water channel portion 7 flows into the air tank 13. An air chamber (gas chamber) 20 is formed in the upper portion of the air tank 13, and the air chamber 20 is filled with a gas such as air. A water level sensor 14 is disposed in the air tank 13, and the water level in the air tank 13 is measured by the water level sensor 14. The water level sensor 14 is connected to the computer 17, and the water level in the air tank 13 is transmitted from the water level sensor 14 to the computer 17 as a signal.
[0024]
The drainage station of this embodiment introduces air into the air tank 13 to increase the pressure in the air tank 13 and release the air in the air tank 13 and the air pump 16 for lowering the water level in the air tank 13. Is provided with an air relief valve 15 for lowering the pressure in the air tank 13 and raising the water level in the air tank 13. These air pump 16 and air relief valve 15 are connected to a computer 17. Then, the computer 17 comprehensively determines signals transmitted from the pressure sensor 12 and the water level sensor 14 and adjusts the water level in the air tank 13 to an appropriate position so that the air pump 16 and the air relief valve 15 are adjusted. To control. Thus, by operating the air relief valve 15 and the air pump 16, the water level in the air tank 13 can be changed and the volume of the air chamber 20 can be changed. The air relief valve 15 and the air pump 16 are configured as volume changing means.
[0025]
The suction water channel 2 is provided with a suction water level sensor 9 for measuring the water level in the suction water channel 2. The suction water level sensor 9 is provided to give operation permission to the pump 4 when the water in the suction water channel 2 is at a certain level or higher. The drainage station shown in FIG. 1 is a configuration example in which the air tank 13 is arranged in the closed water channel portion 7 of the suction water channel 2, but the air tank can be similarly arranged in the closed water channel portion 8 of the discharge water channel.
[0026]
Next, a method for starting the drainage station configured as described above will be described.
First, before starting the pump 4 of the drainage station, the air relief valve 15 of the air tank 13 is opened by a command from the computer 17. Thereby, the air tank 13 is completely filled with water, and the water level in the air tank 13 is raised to the highest position. Next, the computer 17 transmits sound waves from the underwater speaker 11 and causes the pressure sensor 12 to measure the pressure pulsation of water in the suction channel 2. And the computer 17 calculates and calculates | requires the natural frequency (resonance natural frequency) of the water in the suction channel 2 by comparing the measured value with the data currently hold | maintained.
[0027]
On the other hand, the excitation frequency of the excitation force generated by the operation of the pump 4 is predicted based on the number of blades of the impeller of the pump 4, the rotational speed, and the like, and is input to the computer 17 in advance as a predictable value. The natural frequency obtained by the above calculation is compared with the excitation frequency by the computer 17. When the natural frequency matches the excitation frequency within a predetermined ratio range, the computer 17 adjusts the water level in the air tank 13 based on data input to the computer 17 in advance, and The volume of the air chamber 20 is controlled such that the natural frequency is separated from the excitation frequency by a predetermined ratio or more.
[0028]
That is, the computer 17 issues a command to the air pump 16 to increase the pressure of the air chamber 20 in the air tank 13 and operates the air pump 16 to lower the water level of the air tank 13. Next, the computer 17 again transmits sound waves from the underwater speaker 11 at the water level of the air tank 13 newly set as a result of the above operation, and the natural frequency of water in the suction channel 2 is determined by the same method as described above. Calculate. And if this natural frequency is separated from the excitation frequency of the pump 4 predicted to be above or below a predetermined ratio, the adjustment of the water level in the air tank 13 is completed, and the pump 4 can be started.
[0029]
On the other hand, if the natural frequency and the excitation frequency coincide with each other within a predetermined ratio range, the computer 17 issues a command to the air relief valve 15 or the air pump 16 to adjust the water level of the air tank 13. That is, the air level in the air tank 13 is raised by opening the air relief valve 15 to release the air in the air tank 13, or the pressure in the air tank 13 is raised by driving the air pump 16. Lower the water level. Thereafter, the computer 17 transmits sound waves from the underwater speaker 11 again, calculates the natural frequency of water in the suction channel 2 by the same method as described above, and compares this natural frequency with the excitation frequency. In this way, the computer 17 repeats this operation until the natural frequency deviates from a predicted excitation frequency to a predetermined ratio or more.
[0030]
The change direction of the water level in the air tank 13, that is, the ascending direction or the descending direction and the amount of the change are determined by the computer 17 based on data input to the computer 17 in advance. The water level adjustment in the air tank 13 before the start of the pump 4 is completed when the natural frequency of water in the suction channel 2 and the predicted excitation frequency are separated from the predetermined ratio to or below a predetermined ratio.
[0031]
The ratio between the excitation frequency and the natural frequency can be obtained from the following equation.
Ratio = (Excitation frequency) / (Natural frequency)
As described above, the water level in the air tank 13 is adjusted before the pump 4 is started, and then the pump 4 is started. Thereby, since the vibration frequency of the pump 4 and the natural frequency of the water channel do not match, the pump 4 can be started without causing water channel resonance.
[0032]
After starting the pump 4 according to the above-described procedure, the pressure sensor 12 constantly measures the frequency and magnitude of the pressure pulsation, and these measured values are transmitted from the pressure sensor 12 to the computer 17. If the measured frequency of the pressure pulsation includes a frequency component having a magnitude exceeding a predetermined threshold, the computer 17 determines that a water channel resonance phenomenon has occurred at that frequency. In this case, the computer 17 opens the air relief valve 15 and raises the water level in the air tank 13 to lower the natural frequency, or drives the air pump 16 to lower the water level in the air tank 13. Increase the natural frequency. As a result, the ratio between the excitation frequency and the natural frequency can be reset to a value that does not cause a water channel resonance phenomenon. Therefore, by appropriately setting the threshold value, it is possible to avoid the operation accompanied by the water channel resonance phenomenon, and it is possible to prevent the occurrence of problems such as vibration to the neighboring private house in the drainage station. As described above, when the pulsation of the water and the pulsation of the natural frequency are generated by the operation of the pump 4 during the operation of the pump 4, the volume of the air tank (gas chamber) 13 is changed to change the natural vibration. By changing the number and avoiding resonance, the pulsation can be reduced.
[0033]
The determination of whether to raise or lower the water level in the air tank 13 and the determination of the amount of change in the water level are the relationship between the upper and lower limits of the water level adjustable range in the air tank 13 and the current water level, and The computer 17 performs the processing based on data input in advance to the computer 17. Moreover, the range of the frequency of the pressure pulsation constantly measured by the pressure sensor 12 during operation of the pump 4 is usually 0 Hz or more and 90 Hz or less. This is due to the fact that the human body is generally sensitive to vibrations below 90 Hz. In addition, in the above, although the embodiment of the drainage machine station provided with one air tank (air chamber) has been described, two or more air tanks (air chambers) may be provided.
[0034]
【The invention's effect】
As described above, according to the present invention, by changing the volume of the gas chamber, the natural frequency of water in the water channel can be sufficiently separated from the predicted excitation frequency of the pump, as necessary. It is possible to avoid problems such as vibrations caused by water channel resonance when the pump is started. Furthermore, during pump operation, the frequency and magnitude of the pressure pulsation are always detected, and if the pressure pulsation magnitude exceeds a predetermined threshold, the natural frequency is quickly determined from the excitation frequency. Can only be separated enough. Therefore, by setting the threshold value to an appropriate value, it is possible to prevent the occurrence of a waterway resonance phenomenon even if the excitation frequency or the natural frequency itself changes during operation of the drainage station. It is possible to avoid problems such as vibration caused by From a practical point of view, the drainage station and its operation method capable of quickly responding to any operation state and avoiding the generation of waterway resonance as in the present invention are extremely useful in practice.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a drainage station according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing the overall configuration of a conventional drainage station.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Structure 2 Suction water channel 3 Discharge water channel 4 Pump 5 Engine 6 Building 7 Closed water channel part 8 Suction water channel Closed water channel part 9 Suction water level sensor 11 Underwater speaker 12 Pressure sensor 13 Air tank 14 Water level sensor 15 Air relief valve 16 Air pump 17 Computer 20 Air chamber 21 Sluice

Claims (4)

A water channel connected to the suction or discharge port of the pump;
A gas chamber disposed in a closed channel portion of the water channel;
Volume changing means for changing the volume of the gas chamber;
Control means for controlling the volume changing means based on the natural frequency of water in the water channel ;
Vibration means for exciting water in the water channel;
Pressure measuring means for measuring the pressure of water in the water channel,
The pressure measuring means measures the pressure pulsation of the water in the water channel vibrated by the vibration means, and the control means is a natural vibration of the water in the water channel based on the measurement value of the pressure measuring means. Drainage station characterized by being configured to determine the number . The control means determines that resonance has occurred when the magnitude of the pressure pulsation of water in the water channel is greater than a predetermined threshold, and changes the volume of the gas chamber via the volume changing means. pumping stations according to claim 1, characterized in that it is configured to. A method for operating a drainage station having a water channel connected to a suction port or a discharge port of a pump,
The natural frequency of water in the water channel is determined from the pressure pulsation of the water by vibrating the water in the water channel,
Comparing the natural frequency with the predicted excitation frequency of the pump;
When the natural frequency matches the excitation frequency, change the volume of the gas chamber disposed in the closed water channel in the water channel,
The drainage pump station operating method, wherein the pump is started after the natural frequency is separated from the excitation frequency. If the pulsation of the natural frequency is generated by the operation of the pump during the operation of the pump, the natural frequency is changed by changing the volume of the gas chamber, and resonance is performed. The operation method of the drainage station according to claim 3 , wherein the pulsation is reduced by avoiding the pulsation.

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