Sudden expansion transition section stilling pool structure suitable for high water head and large unit width discharge

Abstract

The sudden expansion transition section stilling pool structure comprises an equal-width rectangular discharge chute, a transition section and a stilling pool which are sequentially communicated, a first energy dissipation part is arranged at the joint of the equal-width rectangular discharge chute and the transition section, and a second energy dissipation part is arranged at the joint of the transition section and the stilling pool. The first energy dissipation part is additionally arranged at the head end of the transition section, so that the aeration effect is remarkably improved, the length of the transition section is shortened, the excavation engineering amount is reduced, the engineering investment is saved, and meanwhile, the second energy dissipation part is arranged at the tail end of the transition section to achieve the purposes of controlling the water flow direction and reducing the near-bottom flow velocity. Compared with a conventional stilling pool, the depth of the stilling pool can be effectively reduced, the excavation volume is further effectively reduced, and the engineering investment is saved.

Description

Technical Field

[0001] The utility model relates to the technical field of water conservancy and hydropower engineering, in particular to a sudden expansion and gradual change section stilling pool structure suitable for high water head and large single width discharge. Background Art

[0002] In water conservancy and hydropower projects, spillways are flood control structures of water conservancy buildings such as reservoirs, which are used to discharge floods of a certain standard. When bottom flow energy dissipation is adopted at the end of the spillway, a stilling pool is usually required. The stilling pool is a commonly used energy dissipation project. Generally speaking, the width of the stilling pool is much larger than the width of the spillway chute. Therefore, a gradient section is required between the spillway and the stilling pool for connection. The diffusion angle of the gradient section can be determined according to an empirical formula. The diffusion angle is generally smaller at high flow rates. Therefore, a longer gradient section is required, which results in a larger engineering workload. If the two abrupt changes in the side walls of the stilling pool are suddenly expanded and the upstream side of the stilling pool is suddenly dropped, the stilling pool will not be able to withstand the impact of the water flow. The type cannot ensure the formation of a low-flooding stable water jump in the stilling pool. Harmful backflow is inevitably generated on both sides of the stilling pool and cavitation vortexes are generated at the sudden expansion, which greatly reduces the impact and wear resistance and energy dissipation efficiency of the stilling pool side walls. The use of a trapezoidal cross-section stilling pool will also expand the width of the stilling pool and increase the excavation and support engineering volume of the slopes on both sides. The use of a sudden expansion gradient section connected to the rectangular stilling pool can effectively reduce the length of the gradient section, ensure the formation of a low-flooding stable water area in the stilling pool, avoid backflow on both sides, and reduce the size of the chute gradient section and the stilling pool structure. It has important theoretical value and engineering significance. Utility Model Content

[0003] The purpose of the utility model is to provide a sudden expansion gradient section stilling pool structure suitable for high head and large single width discharge. By adding a first energy dissipation part at the head end of the gradient section, the aeration effect is significantly increased, thereby shortening the length of the gradient section, reducing the excavation amount, and saving project investment. At the same time, a second energy dissipation part is set at the end of the gradient section to achieve the purpose of controlling the water flow direction and reducing the bottom flow velocity. Compared with conventional stilling pools, the depth of the stilling pool can be effectively reduced, further effectively reducing the excavation amount and saving project investment.

[0004] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions:

[0005] A sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge, comprising a rectangular discharge chute of equal width, a gradual change section and a stilling pool connected in sequence;

[0006] Wherein, a first energy dissipation portion is provided at the connection between the equal-width rectangular chute and the gradient section, and a second energy dissipation portion is provided at the connection between the gradient section and the stilling pool.

[0007] The biggest feature and advantage of this scheme compared with the general chute gradient section connected to the stilling pool is that by setting the first energy dissipation part at the head end of the gradient section, the aeration effect is significantly increased, thereby shortening the length of the gradient section; by setting the second energy dissipation part at the end of the gradient section, the direction of water flow is controlled and the bottom flow velocity is reduced, which significantly improves the water flow form and ensures that the water flow energy is fully dissipated.

[0008] As a further technical solution to the energy dissipation pool structure, the first energy dissipation portion includes a sudden expansion, which extends toward both sides of the equal-width rectangular chute, which can significantly increase the aeration effect of the gradient section, increase the diffusion angle α, and thus significantly reduce the length of the gradient section.

[0009] As a further technical solution to the stilling basin structure, in order to further increase the aeration effect of the gradient section, the width of the sudden expansion is set to B1, and the width B1 is the same horizontal elevation distance between the end of the equal-width chute and the gradient section diffusion side wall of the gradient section.

[0010] As a further technical solution of the stilling basin structure, in order to further increase the aeration effect of the gradient section, the width B1 is in the range of 0.5 to 1.0 m.

[0011] As a further technical solution to the energy dissipation pool structure, the diffusion side walls of the gradient section are located on both sides of the gradient section, the diffusion side walls of the gradient section are respectively connected to the sudden expansion, and the diffusion side walls of the gradient section are all inclined toward the outside of the sudden expansion to form a diffusion angle α. By appropriately increasing the value of α, the length L of the gradient section can be shortened, the excavation volume can be reduced, and the project investment can be saved.

[0012] As a further technical solution of the stilling basin structure, the diffusion angle α is determined by calculating the average Froude number of the first and last sections of the transition section according to an empirical formula.

[0013] As a further technical solution to the stilling pool structure, the second energy dissipation part includes a drop-down ramp, and the two sides of the drop-down ramp are connected to the lower part of the side wall of the stilling pool, so that the gradient section and the stilling pool form a vertical drop in the longitudinal direction, thereby forming a bottom flow jump in the stilling pool that meets the energy dissipation needs and dissipates a large amount of energy.

[0014] As a further technical solution to the stilling pool structure, in order to further improve the energy dissipation effect, the vertical distance H1 of the drop is not less than 3m. The drop height H1 is related to the low flow velocity and should not be too small. However, if it is too large, it will cause increased investment. During construction, it is advisable to control the low flow velocity to no more than 20m / s.

[0015] As a further technical solution to the stilling pool structure, the second energy dissipation part also includes a horizontal sill, which connects the gradient section and the drop sill respectively. The horizontal sill effectively controls the direction of water flow, improves the water flow shape, and reduces the bottom flow velocity.

[0016] As a further technical solution to the stilling pool structure, the horizontal cantilever is in the shape of a circular arc, the upstream side of the horizontal cantilever is tangent to the equal-width rectangular chute, and the downstream side of the horizontal cantilever is tangent to the horizontal direction and connected to the drop cantilever, thereby further achieving the purpose of controlling the direction of water flow and reducing the bottom flow velocity.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] 1. The utility model is provided with a double energy dissipation structure, which can significantly increase the aeration effect of the gradient section, increase the diffusion angle α, and thus greatly reduce the length of the gradient section.

[0019] 2. The overall size of the utility model is smaller than that of the conventional stilling pool, forming a bottom flow jump that meets the energy dissipation needs, eliminating a large amount of energy, and being at a certain distance from the structural surface, avoiding erosion and vibration pulse damage to the flow surface.

[0020] 3. The downstream water of the utility model flows through the horizontal cantilever and the vertical drop sill at the bottom into the energy dissipation pool, which can effectively control the direction of water flow, improve the water flow shape, reduce the bottom flow velocity, reduce the depth of the energy dissipation pool compared with the conventional energy dissipation pool, and reduce the width of the energy dissipation pool compared with the sudden drop sill energy dissipation pool. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0022] Figure 1 It is a schematic diagram of the planar structure of the gradient section and the stilling basin of the utility model.

[0023] Figure 2 It is a schematic diagram of the longitudinal section structure of the gradient section and the stilling basin of the present invention.

[0024] Markings and corresponding parts names in the accompanying drawings:

[0025] 1-sudden expansion, 2-gradual section diffusion side wall, 3-gradual section, 4-horizontal cantilever, 5-stilling basin, 6-drop cantilever. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The schematic implementation methods of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example

[0028] This embodiment provides a sudden expansion and gradual change stilling pool structure suitable for high head and large single width discharge, such as Figure 1-Figure 2 As shown, it includes an equal-width rectangular chute, a gradient section 3 and an energy dissipation pool 5 that are connected in sequence. A first energy dissipation part is provided at the connection between the equal-width rectangular chute and the gradient section 3, and a second energy dissipation part is provided at the connection between the gradient section 3 and the energy dissipation pool 5.

[0029] Among them, Figure 1 As shown, the first energy dissipation portion includes a sudden expansion 1, which extends toward both sides of the equal-width rectangular trough and is symmetrically arranged about the equal-width rectangular trough, and the width of the sudden expansion 1 is set to B1. The width B1 is the same horizontal elevation distance between the end of the equal-width trough and the gradient section diffusion side wall 2 of the gradient section 3. The width B1 is in the range of 0.5 to 1.0 m. During construction, the width B1 can be selected according to the flow velocity at the head end of the gradient section, and the smaller value is taken when the flow velocity is greater than 20 m / s.

[0030] In this embodiment, please refer to Figure 1 As shown, the above-mentioned gradient section diffusion side walls 2 are located on both sides of the gradient section 3, and the gradient section diffusion side walls 2 are respectively connected to the sudden expansion 1, and the gradient section diffusion side walls 2 are inclined to the outside of the sudden expansion to form a diffusion angle α. According to the formula Determine the maximum diffusion angle of the conventional gradient section, where Fr is the average Froude number at the beginning and end of the diffusion section, and k is an empirical coefficient, which can be taken as k = 3.0. Since the sudden expansion 1 significantly increases the aeration effect, the diffusion angle α can be increased by 1° to 3° compared with the calculated value. Therefore, by appropriately increasing the value of α, the length L of the gradient section can be shortened.

[0031] Among them, see Figure 2 As shown, the second energy dissipation part includes a drop sill 6, and the two sides of the drop sill 6 are connected to the lower part of the side wall of the energy dissipation pool 5, so that the gradient section 3 and the energy dissipation pool 5 form a vertical drop in the longitudinal direction, thereby forming a bottom flow jump in the energy dissipation pool that meets the energy dissipation needs and dissipates a large amount of energy. In this embodiment, the vertical drop height is H1, and H1 is not less than 3m. Specifically, when the height of the drop sill 6 is 3m, the width B1 of the sudden expansion 1 is 0.5m, the diffusion angle 2 is calculated according to the empirical formula to be 2.34°. Combined with the terrain conditions, the actual value is α=3.86°, and the gradient section length L determined thereby is 74m.

[0032] In some embodiments, the second energy dissipation part also includes a horizontal ridge 4, which connects the gradient section 3 and the drop ridge 6 respectively. The horizontal ridge 4 effectively controls the direction of water flow, improves the water flow shape, and reduces the bottom flow velocity. Specifically, the horizontal ridge 4 is an arc line shape, and the upstream side of the horizontal ridge 4 is tangent to the equal-width rectangular chute, and the downstream side of the horizontal ridge 4 is tangent to the horizontal direction and connected to the drop ridge 6. The arc radius R is usually 50m.

[0033] The following are specific construction examples:

[0034] The depth of the stilling pool 5 is H2, which meets the water surface depth requirement for project operation. B2 is the width of the upstream equal-width chute. The width B3 of the stilling pool is determined according to the conventional design method of the equal-width rectangular section stilling pool. The discharge flow under the design flood standard is 583m3 / s, the spillway width is 9m, the stilling pool width is 20m, and the total head from the design flood level of the reservoir to the elevation of the sill at the end of the gradient section is 107m. The diffusion angle of the gradient section is calculated according to the empirical formula to be 2.34°. In this embodiment, the diffusion angle α is taken as 3.86° based on the actual terrain conditions. The single-width flow rate q entering the pool is 29.15m3 / s. The maximum bottom flow velocity is 10m / s and 15m / s, corresponding to the drop sill heights of 4.68m and 1.78m respectively. Taking into account the terrain and geological conditions, the final drop sill height is taken as 3.0m. Among them, Umax is the maximum bottom flow velocity, q is the flow rate per unit width in the stilling pool, and H is the elevation difference between the upstream water level and the bottom plate of the stilling pool. At this time, the maximum bottom flow velocity is 11.99m / s, which meets the anti-abrasion requirements. j =6.9*(H2-H1), the calculated result is 84.7m. Due to the terrain conditions, it is finally taken as 84m.

[0035] Model tests show that with the use of a sudden expansion gradient section and an appropriate diffusion angle α, the water flow in the gradient section is in good condition and diffuses evenly, forming a complete side cavity. After the diffused water hits the side wall downstream of the side cavity, part of it is raised along the side wall to form a water wing, but the amplitude of the water wing is small. The high-speed water flow is adjusted by the horizontal sill and then enters the stilling pool through the vertical drop sill. The high flow velocity area is close to the bottom in the front part of the stilling pool, with a bottom flow velocity of 12.81m / s, which reduces the bottom flow velocity to a certain extent. The flow velocity in the retreat channel after leaving the pool is relatively small. The use of a sudden expansion gradient section effectively shortens the length of the gradient section and saves engineering investment. The use of a stilling pool with a horizontal sill and a vertical drop sill effectively reduces the bottom flow velocity, thereby effectively reducing the depth of the stilling pool. This structure effectively reduces the length of the gradient section and the depth of the stilling pool, thereby reducing the engineering workload and saving engineering investment.

[0036] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above description is only a specific implementation method of the utility model and is not intended to limit the scope of protection of the utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the utility model should be included in the scope of protection of the utility model.

Claims

1. A sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge, characterized in that: It includes a rectangular chute of equal width, a gradient section (3) and a stilling pool (5) connected in sequence; Wherein, a first energy dissipation portion is provided at the connection between the equal-width rectangular chute and the gradient section (3), and a second energy dissipation portion is provided at the connection between the gradient section (3) and the stilling pool (5).

2. According to claim 1, a sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge, characterized in that: The first energy dissipation portion comprises a sudden expansion (1), and the sudden expansion (1) extends towards two side edges of the equal-width rectangular chute.

3. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 2 is characterized in that: The width of the sudden expansion (1) is set to B1, and the width B1 is the same horizontal elevation distance between the end of the equal-width discharge chute and the gradient section diffusion side wall (2) of the gradient section (3).

4. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 3 is characterized in that: The width B1 is in the range of 0.5 to 1.0 m.

5. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 3 is characterized in that: The gradient section diffusion side walls (2) are located on both sides of the gradient section (3), the gradient section diffusion side walls (2) are respectively connected to the sudden expansion (1), and the gradient section diffusion side walls (2) are inclined toward the outside of the sudden expansion (1) to form a diffusion angle α.

6. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 5 is characterized in that: The diffusion angle α has a value range of 1° to 3° greater than the value obtained by calculating the average Froude number of the first and last sections of the gradient section (3) according to an empirical formula.

7. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 1 is characterized in that: The second energy dissipation portion comprises a drop ledge (6), both sides of which are connected to the lower portion of the side wall of the stilling pool (5), so that a vertical drop is formed in the longitudinal direction between the gradient section (3) and the stilling pool (5).

8. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 7 is characterized in that: The vertical distance H1 of the step (6) is not less than 3m.

9. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 7 is characterized in that: The second energy dissipation portion further comprises a horizontal ridge (4), wherein the horizontal ridge (4) respectively connects the gradual change section (3) and the drop ridge (6).

10. The sudden expansion and gradual change section stilling pool structure suitable for high head and large single width discharge according to claim 9 is characterized in that: The horizontal sill (4) is in the shape of an arc line, the upstream side of the horizontal sill (4) is tangent to the equal-width rectangular chute, and the downstream side of the horizontal sill (4) is tangent to the horizontal direction and connected to the drop sill (6).

Images