Aerated drop-flow vertical shaft flood discharge system

Abstract

The invention discloses an aeration type drop-flow vertical shaft flood discharge system in the field of hydraulic engineering, and the aeration type drop-flow vertical shaft flood discharge system comprises a vertical shaft, a water-gas mixing energy dissipation chamber, a water-gas separation chamber and a water recession tunnel, the middle part and the lower half part of the inner wall of the vertical shaft are respectively provided with a first annular aeration groove and a second annular aeration groove; the first annular aeration groove is communicated with the top of the water-gas separation chamber through a circulating ventilation hole, and the second annular aeration groove is communicated with the atmosphere outside the cavity through an air supply hole. A large amount of air can be brought in by discharged water flow when the discharged water flow passes through the two-stage aeration tank, an air cushion buffer layer is formed at the bottom of the water-air mixing energy dissipation chamber, the impact force on a bottom plate is greatly reduced, meanwhile, violent friction and impact occur in a water-air mixture, a large amount of energy is consumed, and the energy dissipation effect is achieved. The mixed gas overflows from the water-gas separation chamber and enters the first annular gas mixing groove through the circulating ventilation hole, clear water flow enters the water recession tunnel, and the whole system has the advantages of being high in energy dissipation rate, safe in structure, good in water flow state and the like.

Description

Technical Field

[0001] The invention relates to the field of water conservancy projects, and in particular to an aerated drop flow shaft flood discharge system. Background Art

[0002] Vertical shaft spillway tunnels are widely used in hydropower stations as a flood discharge measure that can adapt to various complex terrain and geological conditions. The upstream water flow energy is dissipated inside the building, with good energy dissipation effect and little impact on the downstream. It is economical and reliable. With the large-scale development of pumped storage power stations, more and more vertical shaft spillway tunnels are being used. Traditional vertical shaft spillway tunnels, such as the structure disclosed in the patent document with publication number CN221218734U, are generally composed of an annular overflow weir, a vertical shaft section, a stilling well section, a slope pressure section, and a water withdrawal tunnel section. This flood discharge method dissipates the upstream water flow energy inside the building, with good energy dissipation effect and little impact on the downstream. However, due to the high head, the water flow speed in the vertical shaft section surges, which is unfavorable to the well wall structure. When the water flow falls into the stilling well, due to the incompressibility of the water body, the high flow rate will cause a huge impact on the bottom plate of the stilling well, posing a hidden danger to the structural safety. When water flows into the slope-pressing section, it will be mixed with air, and the flow pattern of the slope-pressing section is complex. The design effect of the slope-pressing section is difficult to ensure, and it will cause the water flow to accelerate again, reducing the energy dissipation effect. In addition, a large amount of gas is mixed into the water body through the shaft. After entering the water withdrawal tunnel, most of the energy has been consumed in the shaft, and the flow rate in the tunnel is significantly reduced. The gas mixed into the water body quickly escapes from the water surface along the way. When the downstream water level is high, it will cause backflow problems, affecting the flood discharge effect. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the existing vertical shaft spillway, the technical problem to be solved by the present invention is: to provide an aerated drop flow vertical shaft spillway system which achieves the function of energy dissipation and erosion reduction and reduces the impact of water flow on the bottom plate by a large amount of aeration, and adopts a water-gas separation method to obtain a clear water flow with low flow velocity and good flow state.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] An aerated drop flow shaft flood discharge system comprises a shaft and a water retreat tunnel connected to the bottom of the shaft, a water-gas mixing energy dissipation chamber is provided at the bottom of the shaft, a water-gas separation chamber is provided between the side of the water-gas mixing energy dissipation chamber and the water retreat tunnel, the cross section of the water-gas mixing energy dissipation chamber is larger than the cross section of the shaft, the cross section of the water-gas separation chamber is larger than the cross section of the water retreat tunnel, and the top of the water-gas separation chamber is higher than the top of the water retreat tunnel, a first annular aeration groove and a second annular aeration groove are respectively provided at the middle and lower half of the inner wall of the shaft, the first annular aeration groove is connected to the top of the water-gas separation chamber through a circulating ventilation hole, and the second annular aeration groove is connected to the atmosphere outside the cavern through an air supply hole.

[0006] Furthermore, a conical transition section is provided between the lower end of the vertical shaft and the top of the water-gas mixing energy dissipation chamber.

[0007] Furthermore, the water-gas mixing energy dissipation chamber, the water-gas separation chamber and the bottom of the water withdrawal tunnel are located on the same horizontal plane.

[0008] Furthermore, the first annular aeration groove is located at a position of 1 / 2 of the height of the vertical shaft, and the second annular aeration groove is located at a position of 1 / 4 of the height of the vertical shaft.

[0009] Furthermore, the depth of the first annular aeration groove and the second annular aeration groove is 1 / 4-1 / 5 of the thickness of the shaft lining, and the height is 1 / 2-3 / 4 of the inner diameter of the shaft.

[0010] Furthermore, the circulating ventilation hole and the air supplement hole are both provided with a horizontal section at one end connected to the vertical shaft.

[0011] Furthermore, the inner diameters of the circulating ventilation hole and the air replenishing hole are respectively the same as the heights of the first annular aeration groove and the second annular aeration groove.

[0012] Furthermore, the inner diameter of the water-gas mixing energy dissipation chamber is 2-3 times the inner diameter of the vertical shaft, and the cone angle of the conical transition section at the lower end of the vertical shaft is 60-90°.

[0013] Furthermore, the top opening of the shaft is a trumpet-shaped opening, and an annular overflow weir is provided outside the opening.

[0014] Furthermore, a maintenance passage communicating with the water-gas separation chamber is provided on the side thereof, and a maintenance door is provided at the connection position between the two.

[0015] The beneficial effect of the present invention is that by setting up two-stage annular aeration grooves in the middle and lower half of the shaft, a large amount of air is forced into the water flow during the downflow process of the high-speed water flow, which can greatly reduce the cavitation erosion phenomenon caused by the high-speed water flow on the shaft wall. When the downflow water flows through the two-stage annular aeration grooves, it carries a large amount of gas into the water-gas mixing energy dissipation chamber, and forms an air cushion buffer layer at the bottom of the energy dissipation chamber, which greatly reduces the impact force of the water flow on the bottom plate. In addition, after entering the mixing energy dissipation chamber, the water body and the gas will be further fully mixed to form a water-gas mixture, and violent friction and collision will occur inside the water flow, consuming a large amount of energy to achieve the effect of energy dissipation. It is not necessary to set up the energy dissipation well and the pressure slope section, which simplifies the engineering structure. After the water-gas mixing and energy dissipation, the water flow enters the water-gas separation chamber. At this time, the water flow velocity drops sharply after energy dissipation, and the mixed gas overflows from the water flow to form a water-gas separation state. The lower part is a clean water flow, and the upper part is a gas cavity. The upper gas enters the first annular aeration groove through the circulating ventilation hole for re-aeration, and the lower clean water flow enters the water retreat tunnel. In addition, since the water entering the water retreat tunnel is a clean water flow with low velocity without aeration, the size of the tunnel can be appropriately reduced compared to other flood discharge tunnels, and the problem of backflow caused by high downstream water level and affecting the discharge capacity is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural cross-sectional view of the present invention;

[0017] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention;

[0018] Figure 3 is an enlarged view of the two-stage aeration tank of the present invention;

[0019] Figure 4 It is a schematic diagram of the flood discharge process of the present invention.

[0020] Marked in the figure are, 1-vertical shaft, 2-water-gas mixing energy dissipation chamber, 3-water-gas separation chamber, 4-water withdrawal tunnel, 5-circulation ventilation tunnel, 6-air supply tunnel, 7-conical transition section, 8-maintenance channel, 11-first annular aeration trough, 12-second annular aeration trough, 13-annular overflow weir. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings.

[0022] It should be noted that if there are directional indication terms in the present invention, such as up, down, left, right, front, and back directions and orientation terms, they are for the purpose of facilitating the description of the relative position relationship between components, and are not specific to the absolute position of the related components or the position relationship between components. They are only used to explain the relative position relationship and movement of the components in a certain posture. If the specific posture changes, the directional indication will also change accordingly. If there are terms related to quantity in the present invention, such as "multiple", "multiple", "several", etc., they specifically refer to two or more.

[0023] like Figure 1-3 As shown, an aerated drop flow shaft flood discharge system provided by the present invention comprises a shaft 1 and a water retreat tunnel 4 connected to the bottom of the shaft 1, a water-gas mixing energy dissipation chamber 2 is provided at the bottom of the shaft 1, a water-gas separation chamber 3 is provided between the side of the water-gas mixing energy dissipation chamber 2 and the water retreat tunnel 4, the cross section of the water-gas mixing energy dissipation chamber 2 is larger than the cross section of the shaft 1, the cross section of the water-gas separation chamber 3 is larger than the cross section of the water retreat tunnel 4, and the top of the water-gas separation chamber 3 is higher than the top of the water retreat tunnel 4, a first annular aeration groove 11 and a second annular aeration groove 12 are respectively provided at the middle and lower half of the inner wall of the shaft 1, the first annular aeration groove 11 is connected to the top of the water-gas separation chamber 3 through a circulating ventilation hole 5, and the second annular aeration groove 12 is connected to the atmosphere outside the cavern through an air supply hole 6.

[0024] The present invention is mainly used for flood discharge of pumped storage reservoirs, and adopts a drop flow type shaft. Generally, the discharge flow is not large, and the water flows directly through the shaft 1 in the vertical direction. Unlike the swirl shaft, the water needs to spiral down along the inner wall of the shaft. Therefore, the structure of the first annular aeration groove 11 and the second annular aeration groove 12 of the present invention is relatively simple. Figure 3 As shown, a circle of annular grooves is provided on the inner wall of the shaft 1. The bottom of the water-gas mixing energy dissipation chamber 2 can provide an air cushion buffer layer, thereby buffering the water-gas mixture. In addition, it provides a space for the water-gas mixture to fully frictionally and impact energy dissipation. Its height and volume are designed according to the downstream flow rate. The larger the flow rate, the larger the volume of the water-gas mixing energy dissipation chamber 2. The water-gas separation chamber 3 is used to separate water and gas to prevent gas from entering the water withdrawal tunnel 4. Therefore, the cross-section and height of the water-gas separation chamber 3 should be larger than the water withdrawal tunnel 4 to allow gas to overflow.

[0025] The working process of the present invention is: Figure 4As shown, after the water flows into the shaft 1, it first passes through the first annular aeration groove 11, and a large amount of air is forced to be mixed into the water flow under the turbulence of the high-speed water flow, and the water flow is aerated for the first time to form a compressible water-air mixture. As the water flow continues to fall, the flow rate further increases, and it reaches the second annular aeration groove 12 for the second aeration to ensure that the water flow is fully aerated to form a water-air mixture that fills the interior of the shaft; the fully aerated water flow enters the water-air mixing energy dissipation chamber 2, and a large amount of gas is mixed in the water flow. After reaching the water-air mixing energy dissipation chamber 2, a compressed buffer layer is formed at the bottom thereof. Due to the compressibility of the gas, the impact of the water flow on the bottom plate is greatly reduced. Impact, at the same time, the aerated water flow will carry out systematic energy dissipation in the water-gas mixing energy dissipation chamber 2, and its energy dissipation mainly consists of the following parts. The first is the water flow collision. After entering the water-gas mixing energy dissipation chamber 2, the water flow is reflected from the buffer layer, moves upward along the side wall of the water-gas mixing energy dissipation chamber 2, and collides with the falling water flow, consuming a lot of energy; the second is the water-gas mixing energy dissipation. The water flow generates friction energy dissipation with the air during the violent turbulence. At the same time, a large number of bubbles in the water flow will burst, and then be re-aerated and mixed. This process also consumes part of the energy; the third is the friction between the water flow and the side wall of the water-gas mixing energy dissipation chamber 2. Friction energy dissipation is generated during the movement of the water flow along the side wall. After sufficient energy dissipation, the water flow mixed with part of the gas enters the water-gas separation chamber 3, the flow velocity of the water flow decreases rapidly, and the mixed gas overflows from the water flow to form a typical water-gas separation state, the lower part is a clean water flow, and the upper part is a gas cavity, wherein the upper gas enters the first annular aeration groove 11 through the circulating ventilation hole 5 to be re-aerated, and the lower clean water flow enters the water retreat tunnel 4, thus forming a flood discharge system with high energy dissipation rate, safe structure and good water flow state. The velocity of the water flow after energy dissipation is greatly reduced when passing through the water-gas separation chamber 3. At the same time, since the drainage volume of the water retreat tunnel 4 is usually equivalent to the water intake volume of the shaft 1, and the cross-section of the water-gas separation chamber 3 is larger than the cross-section of the water retreat tunnel 4, the top of the water-gas separation chamber 3 is higher than the top of the water retreat tunnel 4. Therefore, during the normal drainage process of the water retreat tunnel 4, a certain space will be left on the top of the water-gas separation chamber 3. Therefore, when the water flows through the water-gas separation chamber 3, the mixed gas will overflow from the water flow to form a water-gas separation state, and the upper gas will enter the first annular aeration groove 11 through the circulating ventilation hole 5 for re-aeration, while the lower clean water flow enters the water retreat tunnel 4. Since there is no gas in the water flow, the problem of backflow caused by the high downstream water level and affecting the discharge capacity can be avoided.

[0026] The reason why the circulation ventilation hole 5 is connected to the first annular aeration groove 11 is that the water flow first passes through the first annular aeration groove 11, which can first ensure that the gas in the water-gas separation chamber 3 is discharged, so that a negative pressure is formed inside the chamber, thereby improving the water-gas separation effect. The air replenishment hole 6 is mainly used to further replenish gas, so that the water flow that was dispersed at the first annular aeration groove 11 is dispersed again, achieving an energy dissipation effect.

[0027] During the specific construction, the present invention also provides the following preferred solutions:

[0028] In order to allow the water-gas mixture to smoothly enter the water-gas mixing energy dissipation chamber 2 , a conical transition section 7 may be provided between the lower end of the shaft 1 and the top of the water-gas mixing energy dissipation chamber 2 .

[0029] Since the present invention does not provide an energy dissipation well, there is no need for a slope section, and the water-gas mixing energy dissipation chamber 2 is directly connected to the water-gas separation chamber 3. In order to avoid scouring due to an uneven bottom, the bottoms of the water-gas mixing energy dissipation chamber 2, the water-gas separation chamber 3 and the water withdrawal tunnel 4 are arranged on the same horizontal plane, which can ensure that the water flow flows smoothly and will not accelerate the water flow again, affecting the energy dissipation effect.

[0030] Regarding the design parameters of the two-stage aeration tanks, the preferred solution of the present invention is that the first annular aeration tank 11 is located at 1 / 2 of the height of the shaft 1, and the second annular aeration tank 12 is located at 1 / 4 of the height of the shaft 1. The depth of the first annular aeration tank 11 and the second annular aeration tank 12 is 1 / 4-1 / 5 of the lining thickness of the shaft 1, and the height is 1 / 2-3 / 4 of the inner diameter of the shaft 1. The inner diameters of the circulating ventilation hole 5 and the air supply hole 6 are the same as the heights of the first annular aeration tank 11 and the second annular aeration tank 12, respectively. Of course, during actual construction, the position and size do not need to be absolutely precise, and they can be within a certain range. This application mainly provides a rough reference position and size. In order to prevent water from flowing back into the circulating ventilation hole 5 and the air supply hole 6, a horizontal section can be set at the end of the circulating ventilation hole 5 and the air supply hole 6 connected to the shaft 1. In addition, in order to better gather the water flow to the middle of the shaft 1 and reduce the scouring of the shaft wall, the top opening of the shaft 1 can be set as a trumpet-shaped opening, and a circle of annular overflow weir 13 can be set outside the opening so that the water flow can evenly overflow the annular overflow weir 13 and evenly enter the shaft 1.

[0031] The specific parameters need to be designed according to the discharge capacity, which can be done by following the steps below:

[0032] The annular overflow weir 13 is the key to controlling the discharge capacity of the spillway tunnel. The discharge capacity calculation formula is as follows:

[0033]

[0034] Where: Q-flow rate (m 3 / s);

[0035] D1-weir diameter (m);

[0036] H-water head at the top of the annular overflow weir (m);

[0037] g-gravitational acceleration (m / s2);

[0038] m- annular overflow weir flow coefficient. When the annular overflow weir adopts an elliptical curve, the flow coefficient m can be expressed as follows:

[0039] m=0.56(2H / D1) 0.15

[0040] In addition, according to the model test and numerical analysis of specific projects, it was found that there were vortices in the water flow at the inlet of the annular overflow weir, and vortex-eliminating piers could be arranged to improve the flow state of the water.

[0041] The vertical shaft is the main part that converts water flow from potential energy to kinetic energy. Its inner diameter can be determined by the following formula:

[0042]

[0043] Where: D2-shaft inner diameter (m);

[0044] Q m -Maximum discharge flow (m 3 / s);

[0045] g-gravitational acceleration (m / s 2 );

[0046] Shaft 1 is lined with reinforced concrete, and the lining thickness is generally 1.0m or 1.5m.

[0047] As for the parameters of the water-gas mixing energy dissipation chamber 2, the preferred solution of the present invention is that the inner diameter of the water-gas mixing energy dissipation chamber 2 is 2-3 times the inner diameter of the shaft 1, and the cone angle of the conical transition section 7 at the lower end of the shaft 1 is 60-90°. This is more conducive to the diffusion and mixing of water vapor.

[0048] During the flood discharge process, the surface water usually enters the shaft 1 first, so it will bring in more floating objects. After long-term use, a large amount of floating objects will occupy the top space of the water-gas separation chamber 3, affecting the water-gas separation effect. Therefore, a maintenance passage 8 connected to the water-gas separation chamber 3 is provided on the side of the water-gas separation chamber 3, and a maintenance door is provided at the connection position of the two. The maintenance passage 8 is transformed from the construction branch hole of the tunnel. Construction personnel can enter the water-gas separation chamber 3 through the maintenance passage 8 during the dry season to clean up the floating objects and ensure the stable operation of the entire shaft flood discharge tunnel.

Claims

1. An aerated drop shaft flood discharge system, comprising a shaft (1) and a water withdrawal tunnel (4) connected to the bottom of the shaft (1), characterized in that: A water-gas mixing energy dissipation chamber (2) is provided at the bottom of the vertical shaft (1), and a water-gas separation chamber (3) is provided between the side of the water-gas mixing energy dissipation chamber (2) and the water withdrawal tunnel (4); the cross section of the water-gas mixing energy dissipation chamber (2) is larger than the cross section of the vertical shaft (1), the cross section of the water-gas separation chamber (3) is larger than the cross section of the water withdrawal tunnel (4), and the top of the water-gas separation chamber (3) is higher than the top of the water withdrawal tunnel (4); a first annular aeration groove (11) and a second annular aeration groove (12) are provided in the middle and lower parts of the inner wall of the vertical shaft (1), respectively; the first annular aeration groove (11) is connected to the top of the water-gas separation chamber (3) through a circulating ventilation hole (5), and the second annular aeration groove (12) is connected to the atmosphere outside the cavern through an air supply hole (6).

2. The aerated drop shaft flood discharge system according to claim 1, characterized in that: A conical transition section (7) is provided between the lower end of the vertical shaft (1) and the top of the water-gas mixing energy dissipation chamber (2).

3. The aerated drop shaft flood discharge system according to claim 2, characterized in that: The bottoms of the water-gas mixing energy dissipation chamber (2), the water-gas separation chamber (3) and the water withdrawal tunnel (4) are located on the same horizontal plane.

4. The aerated drop shaft flood discharge system according to claim 1, characterized in that: The first annular aeration groove (11) is located at a 1 / 2 height position of the vertical shaft (1), and the second annular aeration groove (12) is located at a 1 / 4 height position of the vertical shaft (1).

5. The aerated drop shaft flood discharge system according to claim 4, characterized in that: The depth of the first annular aeration groove (11) and the second annular aeration groove (12) is 1 / 4-1 / 5 of the lining thickness of the shaft (1), and the height is 1 / 2-3 / 4 of the inner diameter of the shaft (1).

6. The aerated drop shaft flood discharge system according to claim 1, characterized in that: The circulating ventilation hole (5) and the air replenishing hole (6) are both provided with a horizontal section at one end connected to the vertical shaft (1).

7. The aerated drop shaft flood discharge system according to claim 5, characterized in that: The inner diameters of the circulating ventilation hole (5) and the air replenishing hole (6) are respectively the same as the heights of the first annular aeration groove (11) and the second annular aeration groove (12).

8. The aerated drop shaft flood discharge system according to claim 2, characterized in that: The inner diameter of the water-gas mixing energy dissipation chamber (2) is 2-3 times the inner diameter of the vertical shaft (1), and the cone angle of the conical transition section (7) at the lower end of the vertical shaft (1) is 60-90 degrees.

9. The aerated drop shaft flood discharge system according to claim 1, characterized in that: The top opening of the vertical shaft (1) is a trumpet-shaped opening, and an annular overflow weir (13) is provided outside the opening.

10. The aerated drop shaft flood discharge system according to claim 1, characterized in that: The side of the water-gas separation chamber (3) is provided with an inspection passage (8) communicating therewith, and an inspection door is provided at the connection position between the two.

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