A design method for preventing wave resonance in the pump house flow channel

Abstract

The present invention relates to a design method for preventing wave resonance in the flow channel of a pump house, including: collecting data; calculating the incident wavelength; calculating the wave resonance length of the suction chamber; judging the wave resonance condition; and preventive measures. The present invention gives the definition of the wave resonance length S of the suction chamber of the flow channel: when the incident wave propagates to the vertical breast wall of the suction chamber and is reflected, when the reflected wave encounters the breast wall in the flow channel and is reflected again, the total length of the "closed loop" formed by the wave propagation is the wave resonance length S of the suction chamber. A criterion for wave resonance in the suction chamber of the flow channel is proposed: when the designed wavelength L is equal to or close to the wave resonance length S of the suction chamber, that is, when L / S≈1.0, wave resonance occurs in the suction chamber and the wave height appears at a maximum value. The establishment of this criterion provides a basis for predicting the rationality of the design of the plane geometric scale of the pump house flow channel and the scientific design of measures for preventing wave resonance in the suction chamber of the flow channel.

Description

Technical Field

[0001] The present invention relates to a design method for preventing wave resonance in the flow channel of a pump house, which is a design method for hydraulic structures of the flow channel of a pump house and an engineering design method for preventing wave resonance in the flow channel of a circulating water pump house in a thermal or nuclear power plant. Background Art

[0002] A circulating water pump house in a coastal power plant is affected by offshore waves, and certain water level fluctuations will occur in the forebay and the flow channel. The amplitude of the water level fluctuation is one of the important control indicators for the design and safe operation of a coastal power plant. On the one hand, when the water level fluctuation caused by waves propagates to the filter screen in the pump house, there may be a large water level difference before and after the filter screen, triggering false alarms of the water level monitoring equipment and affecting the stability of the unit operation. On the other hand, the relatively large water level fluctuation propagating into the pump house may cause the water level in the suction chamber of the circulating water pump to decrease, and then generate adverse water flow patterns such as vortices and air intake vortices, resulting in vibrations and abnormal noises of the circulating pump, affecting the water intake safety of the power plant. To prevent relatively large water level fluctuations, the usual measure is to build marine anti-wave measures at the water intake, which not only increases the project land occupation but also increases the investment in the marine engineering of the power plant.

[0003] When waves enter a semi-closed building, complex propagation processes such as reflection, refraction, and breaking will occur. Due to the superposition of incident and reflected waves, when the incident wavelength and the plane geometric scale of the building satisfy a certain relationship, the wave height in the building will reach a maximum value, forming the so-called wave resonance phenomenon. The flow channel of the circulating water pump house in a power plant is a typical semi-closed structure. According to the different forms of the selected rotary filter screen, the layout of its flow channel is also different. Typical ones are the flow channel layout type of the plate-frame filter screen (the plate-frame filter screen is of the type of "water inlet outside the net and water outlet inside the net") and the flow channel layout type of the drum filter screen (the drum filter screen is of the type of "water inlet inside the net and water outlet outside the net"). When the offshore incident waves and the plane geometric scale of the flow channel satisfy the resonance condition, relatively large water level fluctuations will inevitably occur in the flow channel, having an adverse impact on the safe and stable operation of the power plant. Summary of the Invention

[0004] In order to overcome the problems of the prior art, the present invention proposes a design method for preventing wave resonance in the flow channel of a pump house. Based on the test results of a large number of wave physical model tests on the flow channel of the pump house, the method proposes the coupling resonance condition between the incident wave length and the plane geometric scale of the flow channel of the pump house, and gives a design method for preventing wave resonance in the flow channel of the pump house, thus solving the problem of wave resonance in the flow channel of the pump house.

[0005] The object of the present invention is achieved as follows: A design method for preventing wave resonance in the flow channel of a pump house, and the steps of the method are as follows:

[0006] Step 1, data collection: Collect the hydrological and incident wave data of the forebay of the pump house flow channel, including the data of the designed incident wave height H and the designed wave period T corresponding to different design tidal levels or water depths d;

[0007] Step 2, calculate the incident wave length: According to the water depth d and the designed wave period T, calculate the wave length L of the designed wave:

[0008] Calculate the wave angular frequency ω:

[0009] ω = 2π / T

[0010] Calculate the dimensionless water depth kd:

[0011]

[0012] In the formula: y = ω 2 √(dg), C1 = 0.6666666666, C2 = 0.3555555555, C3 = 0.1608465608, C4 = 0.0632098765, C5 = 0.0217540484, C6 = 0.0065407983;

[0013] Calculate the wave length L of the designed wave:

[0014] L = 2π / k;

[0015] Step 3, calculate the wave resonance length of the suction chamber: The wave resonance length S of the suction chamber includes: the length l1 between the inlet of the flow channel and the breast wall of the suction chamber plus the length l2 of the reflected wave of the breast wall of the suction chamber:

[0016] S = l1 + l2;

[0017] Step 4, judge the wave resonance condition: Compare the designed wave length L with the wave resonance length S of the suction chamber. When L is equal to or close to S, that is, L / S ≈ 1.0, wave resonance occurs in the suction chamber and the wave height appears as a maximum value;

[0018] Step 5, preventive measures: When the designed wave length L is equal to or close to the wave resonance length S of the suction chamber, change the resonance length of the flow channel or increase the anti-resonance structures.

[0019] Furthermore, the calculated wave resonance length of the suction chamber is for the layout form of the drum-type rotary screen flow channel, and the calculation of the wave resonance length of the suction chamber is as follows:

[0020] The length l 11 between the breast wall at the inlet of the flow channel and the breast wall of the suction chamber: The length a of the inlet flow channel plus the length b between the drums minus the length c of the breast wall at the inlet between the drums:

[0021] l 11 = a + b - c;

[0022] Length l of the reflected wave of the breast wall in the water absorption chamber 21 Length: the length b between the drum nets minus the length c of the inlet breast wall between the drum nets:

[0023] l 21 = b - c.

[0024] Furthermore, the calculated water absorption chamber wave resonance length calculates the flow channel layout form of the plate - frame filter screen. The calculation of the water absorption chamber wave resonance length is as follows:

[0025] Length l between the inlet of the flow channel and the breast wall of the water absorption chamber 12 Length: the length e of the inlet flow channel plus the length f of the flow channel between the filter screens:

[0026] l 12 = e + f;

[0027] Length l of the reflected wave of the breast wall in the water absorption chamber 22 Length: the length f of the flow channel between the filter screens:

[0028] l 22 = f.

[0029] Furthermore, the anti - resonance structure is arranged in the inlet trench pipe of the flow channel.

[0030] The advantages and beneficial effects of the present invention are as follows: The present invention gives the definition of the wave resonance length S of the flow channel water absorption chamber: When the incident wave propagates to the vertical breast wall of the water absorption chamber and is reflected, when the reflected wave encounters the breast wall in the flow channel and is reflected again, the total length of the "closed loop" formed by the wave propagation is the wave resonance length S of the water absorption chamber. A criterion for wave resonance in the flow channel water absorption chamber is proposed: When the designed wavelength L is equal to or close to the wave resonance length S of the water absorption chamber, that is, L / S≈1.0, wave resonance occurs in the water absorption chamber and the wave height appears at a maximum value. The establishment of this criterion provides a basis for predicting the rationality of the design of the plane geometric scale of the pump house flow channel and the scientific design of measures to prevent wave resonance in the flow channel water absorption chamber. Brief Description of the Drawings

[0031] The present invention will be further described below in conjunction with the drawings and embodiments.

[0032] Figure 1 is the flow chart of the calculation method described in Embodiment 1 of the present invention;

[0033] Figure 2 is the schematic structural diagram of the water absorption chamber of the drum - type rotary filter screen flow channel layout form described in Embodiment 2 of the present invention;

[0034] Figure 3 is the schematic structural diagram of the water absorption chamber of the plate - frame filter screen flow channel layout form described in Embodiment 3 of the present invention. Detailed implementation manners

[0035] Embodiment 1:

[0036] This embodiment is a design method for preventing wave resonance in the pump house flow channel. The pump house flow channel system involved in the design method generally includes: an intake channel, a screen room, a suction chamber, and a circulating water pump. According to the different shapes of the screens, it can be divided into a drum-shaped rotary screen and a plate-frame rotary screen. The structures of the intake channel and the screen room corresponding to the two different-shaped screens are also different. The calculation for preventing wave resonance in the pump house flow channel should be carried out according to the different structures of the intake channel and the screen room.

[0037] The steps of the method are as follows, and the process is as Figure 1 shown:

[0038] Step 1, collect data: Collect the hydrological and incident wave data of the forebay of the pump house flow channel, including the data of the designed incident wave height H and the designed wave period T corresponding to different design tide levels or water depths d.

[0039] Conduct a survey on the environment of the planned pump house or the already built pump house, and collect the local hydrological data.

[0040] Step 2, calculate the incident wave length: According to the water depth d and the designed wave period T, calculate the wave length L of the designed wave:

[0041] Calculate the wave angular frequency ω:

[0042] ω = 2π / T

[0043] Calculate the dimensionless water depth kd:

[0044]

[0045] In the formula: y = ω 2 √(dg), C1 = 0.6666666666, C2 = 0.3555555555, C3 = 0.1608465608,

[0046] C4 = 0.0632098765, C5 = 0.0217540484, C6 = 0.0065407983;

[0047] Calculate the wave length L of the designed wave:

[0048] L = 2π / k.

[0049] Step 3, calculate the wave resonance length of the suction chamber: The wave resonance length S of the suction chamber includes: the length of the distance l1 between the inlet of the flow channel and the breast wall of the suction chamber plus the length of the reflected wave of the breast wall of the suction chamber l2:

[0050] S = l1 + l2;

[0051] Step 4, judging the wave resonance condition: Compare the designed wavelength L with the wave resonance length S of the water absorption chamber. When L is equal to or close to S, that is, L / S≈1.0, wave resonance occurs in the water absorption chamber, and the wave height appears as a maximum value.

[0052] The wave resonance length S of the water absorption chamber is defined as follows: When the incident wave propagates to the vertical breast wall of the water absorption chamber and is reflected, and when the reflected wave encounters the breast wall in the flow channel and is reflected again, the wave propagation path forms a "closed loop", and the total length of this "closed loop" is the wave resonance length S of the water absorption chamber.

[0053] Step 5, preventive measures: When the designed wavelength L is equal to or close to the wave resonance length S of the water absorption chamber, change the length of the inlet flow channel or add anti-resonance structures. The purpose of changing the length of the inlet flow channel or adding anti-resonance structures is to change the wave resonance length S of the water absorption chamber, so that L / S deviates from 1.0, thereby avoiding large water level fluctuations caused by wave resonance in the water absorption chamber. When the water absorption chamber is in the design stage, the length of the inlet flow channel can be changed to avoid resonance. For an already built water absorption chamber, the resonance problem can be solved by adding anti-resonance structures. The anti-resonance structure can be to add a certain length of ditch at the inlet of the inlet flow channel, which is equivalent to increasing the length of the inlet flow channel, thereby avoiding resonance.

[0054] Embodiment 2:

[0055] This embodiment is an improvement of Embodiment 1 and is a refinement of the calculation of the wave resonance length of the water absorption chamber regarding the flow channel layout form of the drum-type rotary filter in the above embodiment. The structure of the drum-type rotary filter flow channel described in this embodiment is as Figure 2 shown, including two left and right inlet flow channels 1, a drum net space 2 sandwiched between the two inlet flow channels, a water absorption chamber 3 and a circulating water pump 4 connected to the drum net space. At the inlet of the inlet flow channel, there is a flow channel inlet breast wall ①, and there are multiple breast walls in the inlet water flow to set coarse grids, fine grids and steel gates. At the intersection of the inlet flow channel and the drum net space, there is a drum net space breast wall ②, and at the intersection of the drum net space and the water absorption chamber, there is a water absorption chamber breast wall ③, as Figure 2 shown.

[0056] The calculation of the wave resonance length of the water absorption chamber is as follows:

[0057] The distance l between the flow channel inlet breast wall and the water absorption chamber breast wall 11 Length: The length a of the inlet flow channel plus the length b of the drum net space, minus the length c of the drum net space inlet breast wall:

[0058] l 11 = a + b - c;

[0059] The length l of the reflected wave of the water absorption chamber breast wall 21Length: the length b between the drum screens minus the length c of the inlet breast wall between the drum screens:

[0060] l 21 = b - c.

[0061] The calculation of the wave resonance length S of the water absorption chamber of the drum filter screen channel is as follows Figure 2 , the incident waves propagate from both sides of the channel, converge to the space between the drum filters (between the drum screens), and are reflected after encountering the vertical breast wall of the water absorption chamber. Some of the reflected waves are reflected again after encountering the breast walls on both sides of the drum screen, so that part of the wave energy is confined in the narrow space between the drum screens, forming a wave resonance phenomenon with an increased wave height. The wave resonance length S of the water absorption chamber is the length of wave propagation, that is, the total length from "① inlet breast wall of the channel → ② breast wall between the drum screens → ③ breast wall of the water absorption chamber → ② breast wall between the drum screens".

[0062] For the test of an existing water supply facility, the height H of the incident waves ranges from a few tenths of a meter to several meters. The incident wavelength L at different wave periods T under different water depths d is calculated according to the aforementioned formula. When the incident wavelength L is close to the wave resonance length S (36 m) of the water absorption chamber, that is, L / S ≈ 1.0, a maximum wave height appears in the water absorption chamber. During design, the coupling between the wave resonance length S of the water absorption chamber and the incident wavelength L can be avoided by changing the length of the channel or setting a trench of a certain length at the inlet of the channel.

[0063] Example 3:

[0064] This example is an improvement of Example 1 and is a refinement of the calculation of the wave resonance length of the water absorption chamber regarding the layout form of the plate-frame filter screen channel in Example 1. The structure of the plate-frame filter screen channel described in this example is as Figure 3 shown,

[0065] The calculation of the wave resonance length of the water absorption chamber described in this example calculates the layout form of the plate-frame filter screen channel, including two left and right inlet channels 5, two filter screen spaces 6 are respectively set in the two channels, and the two channels are merged together after passing through the filter screen spaces to reach the breast wall of the water absorption chamber, as well as the water absorption chamber and the circulation pump. There is a channel inlet breast wall ① at the inlet of the inlet channel, and multiple breast walls are provided during the water inlet flow to set coarse grids, fine grids and steel gates. There is a filter screen space breast wall ② at the junction of the inlet channel and the filter screen space channel, and there is a water absorption chamber breast wall ③ between the filter screen space channel and the water absorption chamber, as Figure 3 shown.

[0066] The calculation of the wave resonance length of the water absorption chamber is as follows:

[0067] The distance l between the inlet of the channel and the breast wall of the water absorption chamber 12 Length: the length e of the inlet channel plus the length f of the filter screen space channel:

[0068] l 12 = e + f;

[0069] The length l of the reflected wave of the breast wall in the water absorption chamber 22 Length: The length f of the flow channel between the filter meshes:

[0070] l 22 = f.

[0071] The calculation of the wave resonance length of the plate - frame filter mesh flow channel water absorption chamber is as Figure 3 shown. The incident wave propagates and converges from the breast wall at the inlet of the flow channel to the water absorption chamber. After encountering the vertical breast wall of the water absorption chamber, it is reflected. Part of the reflected wave is reflected again after encountering the breast wall in front of the filter mesh, so that part of the wave energy is restricted in the narrow space of the flow channel, forming a wave resonance phenomenon with an increasing wave height. The wave resonance length S of the water absorption chamber is the length of wave propagation, that is, the total length from "① breast wall at the inlet of the flow channel → ② breast wall between the filter meshes → ③ breast wall of the water absorption chamber → ② breast wall between the filter meshes".

[0072] The height H of the incident wave outside the flow channel of a certain under - construction project ranges from a few tenths of a meter to several meters. The incident wavelength L at different wave periods T under different water depths d is calculated according to the aforementioned formula. When the incident wavelength L is close to the wave resonance length S (50 m) of the water absorption chamber, that is, L / S≈1.0, a maximum wave height appears in the water absorption chamber. During design, the coupling of the wave resonance length S of the water absorption chamber and the incident wavelength L can be avoided by changing the length of the flow channel or setting a certain - length trench at the inlet of the flow channel.

[0073] Example 4:

[0074] This example is an improvement of the above - mentioned example and is a refinement of the above - mentioned example regarding the anti - resonance structure. The anti - resonance structure described in this example is a trench pipe (12 m) provided at the inlet of the flow channel.

[0075] The trench pipe can be a square culvert or a circular pipe, and is usually used in the water absorption chamber structure that has been built.

[0076] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred layout scheme, those of ordinary skill in the art should understand that the technical solution of the present invention (such as the form of the water absorption chamber, the application of various formulas, the sequence of steps, etc.) can be modified or equivalently replaced without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A design method for preventing wave resonance in the pump house flow channel, characterized in that The steps of the method are as follows: Step 1, collect data: Collect the hydrological and incident wave data of the forebay of the pump house flow channel, including the data of the designed incident wave height H and the designed wave period T corresponding to different design tide levels or water depths d; Step 2, calculate the incident wave length: According to the water depth d and the designed wave period T, calculate the wave length L of the designed wave: Calculate the wave angular frequency ω: ω = 2π / T Calculate the dimensionless water depth kd: where: y = ω 2 d / g, C1 = 0.6666666666, C2 = 0.3555555555, C3 = 0.1608465608, C4 = 0.0632098765, C5 = 0.0217540484, C6 = 0.0065407983; Calculate the wave length L of the designed wave: L = 2π / k; Step 3, calculate the wave resonance length of the suction chamber: The wave resonance length S of the suction chamber includes: the length l1 between the inlet of the flow channel and the breast wall of the suction chamber plus the length l2 of the reflected wave of the breast wall of the suction chamber: S＝l1+l2； Step 4, judge the wave resonance condition: Compare the designed wave length L with the wave resonance length S of the suction chamber. When L is equal to or close to S, that is, L / S≈1.0, wave resonance occurs in the suction chamber and the wave height appears at a maximum value; Step 5, preventive measures: When the designed wave length L is equal to or close to the wave resonance length S of the suction chamber, change the resonance length of the flow channel or add anti-resonance structures.

2. The design method according to claim 1, characterized in that The calculation of the wave resonance length of the suction chamber calculates the layout form of the drum-shaped rotary filter flow channel, and the calculation of the wave resonance length of the suction chamber is as follows: The distance l between the breast wall at the runner inlet and the breast wall at the suction chamber 11 Length: the length a of the inlet runner plus the length b between the drum screens, minus the length c of the breast wall at the inlet between the drum screens l 11 = a + b - c; Length l of the reflected wave of the breast wall in the water absorption chamber 21 Length: length b between the drum nets minus length c of the inlet breast wall between the drum nets: l 21 = b - c.

3. The design method according to claim 1, wherein The calculation of the wave resonance length of the suction chamber calculates the layout form of the plate-frame filter flow channel, and the calculation of the wave resonance length of the suction chamber is as follows: The distance l between the runner inlet and the breast wall of the suction chamber 12 Length: the length e of the inlet water passage plus the length f of the passage between the strainers l 12 = e + f; Length l of the reflected wave of the breast wall in the water absorption chamber 22 Length: length f of the flow channel between the filter meshes: l 22 ＝f。 4. The design method according to claim 2 or 3, characterized in that The anti-resonance structure is arranged in the inlet conduit of the flow channel.

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