Improved outlet design method for shaft outflow and inlet and outlet structure based on it

Abstract

The present invention discloses an outlet design method for improving shaft outflow and an inlet and outlet structure based thereon, belonging to the technical field of water conservancy engineering. The inlet and outlet structure comprises a water flow channel, the water flow channel has a vertical section, the upper end of the vertical section is the inlet and outlet, diversion components are evenly distributed around the inlet and outlet, and is characterized in that: the upper part of the diversion component is arranged on a cylindrical retaining wall forming a stop structure around the upper part of the inlet and outlet, and the upper edge height of the cylindrical retaining wall is higher than the dead water level of the reservoir area of ​​the pumped storage power station. The shaft-type inlet and outlet structure significantly improves the uniformity of water flow, flow distribution and flow velocity distribution of trash racks by introducing buffer water and optimizing the design, completely eliminating the problem of reverse flow velocity, and improving the safety of power station operation, equipment life and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to an outlet design method for improving shaft outflow and an inlet and outlet structure based thereon. Background Art

[0002] A pumped storage power station is a power system that optimizes the load on the power grid by storing and regulating electricity. It uses electricity to pump water from the lower reservoir to the upper reservoir for storage during the period of low electricity demand; when the peak of electricity demand comes, the water stored in the upper reservoir flows through the turbine to generate electricity, thereby providing additional electricity to the power grid. This process not only helps balance the load of the power grid, but also improves the reliability and stability of the power system. Pumped storage power stations can effectively regulate the supply of electricity, support the access of renewable energy, and promote the sustainable use of energy. In recent years, the construction of pumped storage power stations in my country has developed rapidly. The vertical shaft inlet and outlet has been widely used in pumped storage power stations due to its flexible layout, relatively low requirements for terrain and geological conditions, small amount of excavation and concrete structure, and simple structural stress.

[0003] The structure of the existing vertical shaft water inlet and outlet is as follows Figure 3 , mainly including water flow channel, cover plate 8, guide cone 9 and guide cone 5. The water flow channel is further subdivided into four parts: vertical diffusion section 1, straight pipe section 2, bend section 3 and gradient section 4. The bend section forms a 90° channel phase change, that is, the horizontal transport is transformed into vertical transport, and at the inlet and outlet, the water flow is deformed to horizontal again.

[0004] Although the vertical shaft inlet and outlet is a common design in pumped storage power plants, it has some significant disadvantages and shortcomings in practical applications:

[0005] Since the shaft-type inlet and outlet design needs to achieve two-way flow of water (water flows from horizontal to vertical, and then from vertical to horizontal), the water flow undergoes two 90° flow direction changes in a short distance. This design causes the flow direction of the water to change dramatically, resulting in very complex hydraulic conditions. Under the conditions of inflow (power generation conditions) and outflow (pumping conditions), the water flow needs to change its flow direction under the obstruction of the guide cone and cover plate, which is prone to produce vortices and unstable flow patterns, all of which have an adverse effect on the efficiency and safety of the system.

[0006] Trash racks are fence-like structures formed between diversion piers. Under pumping (outflow) conditions, there is a reverse flow velocity at the bottom of the trash rack section that is difficult to eliminate. The existence of reverse flow velocity may cause damage to the trash rack structure and affect its normal function. The structural limitations of the trash rack and the complex flow pattern of the water flow make it difficult to eliminate these reverse flow velocities, which not only affects the long-term stability of the equipment, but also increases the difficulty of maintenance.

[0007] At the exit of the shaft inlet and outlet, the cover plate and guide cone have a significant obstructive effect. These structural components cause the water flow to face additional resistance when it turns from vertical to horizontal, resulting in energy loss and uneven water flow. Although the guide cone is designed to optimize the entry of water flow, the resistance it creates during the turning process often causes a reduction in flow rate and efficiency loss.

[0008] At present, although many researchers have conducted a lot of numerical analysis and model tests on traditional cover shaft inlets and outlets, the problems of reverse flow velocity and flow instability cannot be completely solved. Although these studies are helpful for understanding and improving the design of shaft inlets and outlets, in actual engineering applications, fluid dynamics problems are still significant, affecting the reliability and performance of the system. Summary of the invention

[0009] In response to the problems existing in the prior art, the present invention provides an outlet design method for improving shaft outflow and an inlet and outlet structure based thereon, which aims to solve the problems of drastic water flow turning, reverse flow velocity and structural obstructions in the traditional shaft-type inlet and outlet design, which affect the operating efficiency and safety of the equipment.

[0010] The present invention is implemented as follows: a method for improving the outlet design of shaft outflow, comprising the following steps:

[0011] S1. Set the reservoir water level before the shaft outflow as the dead water level.

[0012] S2. A cylindrical drainage space extending upward is provided above the trash rack of the vertical shaft type water inlet and outlet, and the cylindrical drainage space meets the following design conditions: the maximum water capacity level of the cylindrical drainage space is higher than the dead water level; the water pressure of the cylindrical drainage space in a filled state is greater than the outflow water pressure of the outlet.

[0013] The second purpose of the present invention is to propose an inlet and outlet structure based on the above-mentioned improved outlet design of the vertical shaft inlet and outlet, including a water flow channel, the water flow channel has a vertical section, the upper end of the vertical section is the inlet and outlet, and diversion components are evenly distributed around the inlet and outlet. It is characterized in that: the upper part of the diversion component is arranged on a cylindrical retaining wall forming a stop structure around the top of the inlet and outlet, and the upper edge height of the cylindrical retaining wall is higher than the dead water level of the reservoir area of ​​the pumped-storage power station.

[0014] In the above technical solution, preferably, the vertical shaft type water inlet and outlet structure includes an annular cover plate, which is arranged between the diverter component and the cylindrical retaining wall, and the annular cover plate forms an annular component with an opening and supported by the diverter component, and the cylindrical retaining wall is arranged on the annular cover plate.

[0015] In the above technical solution, preferably, the opening diameter of the annular cover plate is larger than 2 / 3 of the diameter of the circumscribed circle of the annular cover plate.

[0016] In the above technical solution, preferably, the water flow channel is composed of a vertical diffusion section, a straight pipe section, a bend section and a gradient section in sequence from the water inlet and outlet, and the water inlet and outlet are arranged at the upper end of the vertical diffusion section.

[0017] In the above technical solution, preferably, the diverter member is a diverter pier that is evenly spaced around the water inlet and outlet in an annular direction.

[0018] In the above technical solution, preferably, the opening diameter of the annular cover plate is smaller than the inner diameter of the cylindrical retaining wall, and the water flowing upward from the water outlet forms a lateral backflow after passing through the opening of the annular cover plate.

[0019] The water inlet and outlet designed by the outlet design method for improving the shaft outflow proposed by the present invention has multiple advantages and significant effects:

[0020] 1. The vertical shaft inlet and outlet structure has been optimized, and the hydraulic indicators under both pumping (outflow) and power generation (inflow) conditions meet the requirements of relevant design specifications. This ensures the hydraulic stability of the power station under different operating modes, allowing the power station to operate safely and efficiently under various conditions.

[0021] 2. This structure introduces a buffer water body through structural innovation design, which is significantly different from the traditional physical buffer diversion structure. The buffer water body is formed at the upper end of the inlet and outlet. As a "natural water cushion", it has unique advantages: the buffer water body absorbs the kinetic energy and turbulence of the water flow, reduces the impact force when the water flow enters the shaft, and makes the water flow more stable. Compared with the traditional rigid structure, the soft regulation effect of the buffer water body significantly reduces the turbulence and turbulence of the water flow and improves the uniformity of the water flow. Due to the rigid physical obstruction, the traditional buffer structure is prone to produce eddy currents at the inlet and outlet, while the buffer water body can effectively dissipate the eddy currents and reduce the hydrodynamic disturbance through the natural flow characteristics of water, making the entire hydraulic system more stable. The buffer water body can dynamically adjust the water flow speed and pressure, reduce energy loss, and make the water flow smoother, thereby improving the efficiency of the water flow through the shaft. This effect is unmatched by traditional physical buffer devices.

[0022] 3. Due to the existence of buffer water and optimized hydraulic design, the outflow of the vertical shaft inlet and outlet is more uniform. Especially under pumping conditions, the distribution of water flow is smoother, avoiding the situation of excessive or insufficient local water flow, and ensuring the stability of the entire water flow system.

[0023] 4. The optimized structure makes the flow distribution of each orifice more balanced, which is crucial to ensure the flow consistency of water in different orifices. Uniform flow distribution helps to reduce hydraulic fluctuations and prevent hydraulic pressure imbalance caused by excessive or low local flow.

[0024] 5. The traditional trash rack design is prone to uneven flow, especially at the bottom of the section, which easily accumulates reverse flow. By optimizing the water flow path and introducing buffer water, the flow velocity distribution of the trash rack section is significantly improved, the water flow is more uniform at the trash rack, and turbulence and unstable flow are reduced.

[0025] 6. The present invention specifically solves the long-standing problem of reverse flow velocity at the bottom of the trash rack section. In the traditional shaft-type water inlet and outlet design, the reverse flow velocity has a significant impact on the trash rack structure, causing it to be easily damaged. However, this optimized design completely eliminates the occurrence of reverse flow velocity through the regulation of the buffer water body and the improved water flow path, thereby avoiding the damage of the reverse flow velocity to the trash rack.

[0026] 7. Due to the elimination of reverse flow velocity, the trash rack structure is no longer subject to frequent impact and wear, which greatly extends its service life. The frequency of inspection and replacement of the trash rack is significantly reduced, reducing the maintenance cost during operation. This advantage directly improves the economic benefits of the power station and reduces the cost of daily operation.

[0027] 8. By optimizing the distribution of water flow, uniform outflow and effectively solving the problem of reverse flow rate, the overall hydraulic conditions of the shaft inlet and outlet are greatly improved, and the operation of the power station under different working conditions is more stable and safe. Especially under high-load conditions, this design effectively reduces the risk of accidents caused by hydraulic anomalies and improves the reliability of the power station.

[0028] 9. By reducing equipment maintenance and replacement costs and extending equipment life, the overall operating cost of the power station has been greatly reduced. At the same time, the improvement of water flow efficiency has directly increased the power generation efficiency and pumping efficiency of the power station, further improving the economic benefits of the power station. Taking these factors into consideration, this optimized design has brought significant economic advantages to the long-term operation of the power station.

[0029] The technical solution proposed by the present invention has comprehensively improved the hydrodynamic performance and structural stability of the shaft-type water inlet and outlet by introducing a buffer water body and optimizing the design. It not only solves the reverse flow velocity problem in the traditional design, but also significantly improves the uniformity of the water flow, the orifice flow distribution and the operating conditions of the trash rack, ensuring the safe operation of the power station and improving the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the present invention;

[0031] Figure 2 is a top view of the water inlet and outlet of the present invention;

[0032] Figure 3 It is a structural schematic diagram of the existing water inlet and outlet. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] In order to solve the problems of violent water flow turning, reverse flow velocity and structural obstruction in the design of traditional shaft-type water inlet and outlet, the present invention provides an outlet design method for improving shaft outflow and a water inlet and outlet structure based thereon. The shaft-type water inlet and outlet structure significantly improves the uniformity of water flow, flow distribution and trash rack flow velocity distribution through optimized design, completely eliminates the reverse flow velocity problem, improves the safety of power station operation, equipment life and economic benefits, and has wide promotion and application value. In order to further illustrate the structure of the present invention, the detailed description is as follows in conjunction with the attached drawings:

[0035] Embodiment 1

[0036] A method for improving the outlet design of shaft outflow, characterized in that it comprises the following steps:

[0037] S1. Set the reservoir water level before the shaft outflow as the dead water level.

[0038] Dead water level refers to the lowest water level allowed in a reservoir. Setting the water level before the shaft outflow as the dead water level means that when the system is in operation, the water flow in the shaft will be designed and operated based on the minimum water level condition. This is to ensure that during the operation of the power station, even if the reservoir water level drops to the minimum level, the shaft can still be normally outflowed to maintain hydropower generation.

[0039] S2. A cylindrical drainage space extending upward is provided above the trash rack of the vertical shaft inlet and outlet, and the cylindrical drainage space meets the following design conditions:

[0040] The maximum water level of the cylindrical water-retaining space is higher than the dead water level;

[0041] The water pressure of the cylindrical water space in a filled state is greater than the outflow water pressure of the water outlet.

[0042] Trash racks are used to prevent large particles or floating objects from entering the shaft and protect the outlet from being blocked. Here, a cylindrical water space is installed above the trash rack. The cylindrical water space is an additional space for storing water. Its design purpose is to regulate the water pressure and water level in the shaft and play a buffering role.

[0043] The water pressure of the cylindrical water space when filled is greater than the outflow water pressure at the outlet: This design ensures that the water in the cylindrical water space, when filled, can form sufficient pressure to exceed the water pressure at the outlet, thereby pushing the water flow through the trash rack of the diversion pier smoothly. This design helps to slow down the turbulence of the water outflow from the shaft and reduce possible energy losses.

[0044] Embodiment 2

[0045] See also Figure 1 and Figure 2 A vertical shaft water inlet and outlet structure of a pumped storage power station includes a water flow channel, the water flow channel has a vertical section, the upper end of the vertical section is the water inlet and outlet, and diversion components are evenly distributed around the water inlet and outlet.

[0046] The water flow channel is composed of the vertical diffusion section 1, the straight pipe section 2, the bend section 3 and the gradient section 4 from the water inlet and outlet inward, and the water inlet and outlet are arranged at the upper end of the vertical diffusion section. The vertical diffusion section is a vertical part in the shaft, and the cross-sectional area gradually increases. Its main function is to slow down the water flow speed and prevent the adverse effects caused by excessive water flow. The straight pipe section is a vertical straight pipe through which the water flows, which is used to maintain the stability of the water flow and ensure that the water flows in or out evenly. The bend section is the curved part in the water flow channel, which is used to change the direction of the water flow in order to adapt to the terrain or the needs of the layout of the water conservancy project. The gradient section is a part of the pipe where the cross-section gradually changes, which is used to adjust the speed and pressure of the water flow and reduce the energy loss in the flow.

[0047] The diversion component is a diversion pier 5 which is evenly spaced around the water inlet and outlet. The diversion pier is an existing component. The diversion pier is arranged at the upper end of the vertical diffusion section of the shaft-type water inlet and outlet, and is located at a key position where the water flow enters or discharges the shaft. Through reasonable geometric design, the water flow is guided and dispersed, so that the water flow is more uniform when entering the shaft, and the eddy current and water flow instability are reduced. The setting of the diversion pier helps to improve the efficiency of the water flow and ensure that even when the reservoir water level is close to the minimum, the water flow can still smoothly enter or discharge the water inlet and outlet to maintain the normal operation of the power station.

[0048] The upper part of the diversion pier is provided with a cylindrical retaining wall 6 forming a stop structure around the inlet and outlet, and the upper edge height of the cylindrical retaining wall is higher than the dead water level of the reservoir area of ​​the pumped storage power station. The dead water level of the reservoir area of ​​the pumped storage power station refers to the water level line that is still retained when the water level in the reservoir drops to the lowest.

[0049] The annular cover plate 7 is provided between the diverter member and the cylindrical retaining wall. The annular cover plate forms an annular member having an opening and supported on the diverter member. The cylindrical retaining wall is provided on the annular cover plate. The opening diameter of the annular cover plate is greater than 2 / 3 of the diameter of the circumscribed circle of the annular cover plate. In this embodiment, the diverter pier, the annular cover plate and the cylindrical member are integrally cast concrete parts, or three prefabricated components can be fastened and connected at the engineering site.

[0050] The working principle of the present invention is:

[0051] By adopting the water inlet and outlet structure proposed in the present invention, when the pumping storage power station is in pumping operation, the water flow channel and the inner space of the cylindrical retaining wall extending upward are filled with water, and the water flows upward from the straight pipe section and mixes with the water in the cylindrical retaining wall, thereby avoiding the drastic turning of the water flow caused by the obstruction of the cover plate set in the traditional structure, effectively slowing down the water flow velocity, thereby improving the flow velocity distribution of the trash rack cross section and eliminating the reverse flow velocity at the bottom of the trash rack cross section.

[0052] Since the operating conditions of each actual project are different, the specific height of the cylindrical retaining wall needs to be further determined according to the actual situation. In this embodiment, the cylindrical retaining wall should be at least 5m higher than the dead water level of the reservoir. At the dead water level, in the outflow condition, part of the water flow from the vertical diffusion section flows into the cylindrical wall from the center of the annular cover plate, diffuses to the surroundings in the cylindrical wall, and produces water surface fluctuations. The average water surface in the cylindrical wall is slightly higher than the water level (dead water level) of the reservoir area (about 0.5m); the other part of the water flow interacts with the backflow in the cylindrical wall, and changes from vertical diffusion to horizontal diffusion by 90°. The water flow in the vertical diffusion section diffuses more fully, flows out evenly after being diverted by the diversion pier, and the flow velocity distribution between each orifice is relatively uniform; the mainstream of the trash rack section is close to the middle and upper part of the orifice, there is no reverse flow velocity on the bottom plate of the orifice, and the water surface of the reservoir area outside the inlet and outlet is relatively stable. Under the inflow condition, water flows mainly from the reservoir area through various orifices into the inlet and outlet relatively evenly and smoothly, and the flow pattern is good; the water in the cylinder wall flows around the edge of the cover plate into the inlet and outlet, and the water level is lower than that of the reservoir area (dead water level) (about 0.25m).

[0053] The top of the cylindrical retaining wall is higher than the dead water level of the reservoir, which can prevent the water inside the cylindrical retaining wall and the water in the reservoir from flowing mutually from the top when the water level is low. The water level difference ensures that the water flows out from the diversion pier, avoiding the water flowing out from the upper end of the cylindrical retaining wall during outflow, thereby avoiding water surface fluctuations caused by overflow from the upper end.

[0054] In power generation conditions, water flows from the reservoir area into the water inlet and outlet. The cylindrical retaining wall can prevent the water from flowing from the reservoir area into the top of the cylindrical retaining wall to form harmful vortices or carry debris in the reservoir into the unit to affect the safe operation of the power station.

[0055] Compared with the traditional shaft-type water inlet and outlet, the existing cover plate and guide cone are replaced by a cylindrical retaining wall and an annular cover plate. The annular cover plate is used to assist in fixing the orifice trash rack, and when the flow is discharged, the obstruction of the annular cover plate forming the opening is small. The water flows upward from the straight pipe section and mixes with the water in the cylindrical retaining wall on the top of the annular cover plate, avoiding the drastic turning caused by the cover plate blocking the water flow, effectively slowing down the water flow velocity, thereby improving the flow velocity distribution of the trash rack section and eliminating the reverse flow velocity at the bottom of the trash rack section.

[0056] Taking a pumped storage power station project as an example, further explanation is given in conjunction with the attached drawings:

[0057] The normal water level of a pumped storage power station project reservoir is 606m, and the dead water level is 571m. The inlet and outlet structure proposed in the present invention is adopted. The inner diameter of the cylindrical retaining wall in this structure is 18.5m, and the top elevation is 580m, which is 9m higher than the dead water level of the reservoir area. The annular cover plate has an inner diameter of 15m and an outer diameter of 20m.

[0058] The model test results show that, with the water inlet and outlet structure proposed by the present invention, under the pumping (outflow) condition, the head loss of the shaft-type water inlet and outlet is small, the orifice flow distribution is more uniform, the flow velocity distribution of the trash rack section is more uniform, there is no reverse flow velocity at the bottom of the trash rack section, the water surface fluctuation in the reservoir is small at low water level (dead water level), and the water surface is calm at high water level. Under the power generation condition, the head loss is small, the orifice flow distribution is uniform, the flow velocity distribution of the trash rack section is uniform, and the water surface in the reservoir is calm.

[0059] According to the model test results, the hydraulic indicators of the shaft-type water inlet and outlet meet the design and specification requirements by applying the water inlet and outlet structure proposed in the present invention. In particular, under pumping conditions, the flow distribution of each orifice is more uniform, the flow velocity distribution of the trash rack section is more uniform, and the reverse flow velocity at the bottom of the trash rack section is eliminated. The water inlet and outlet structure proposed in the present invention effectively solves the problem that the reverse flow velocity at the bottom of the trash rack section of the outflow of the shaft-type water inlet and outlet has been difficult to eliminate for many years. The effect is obvious, which is conducive to reducing the safety risk of power station operation and can be widely promoted and applied in pumped storage power station projects.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the outlet design of shaft outflow, characterized in that: The following steps are involved: S1. Set the reservoir water level before the shaft outflow as the dead water level; S2. A cylindrical drainage space extending upward is provided above the trash rack of the vertical shaft inlet and outlet, and the cylindrical drainage space meets the following design conditions: The maximum water level of the cylindrical water-retaining space is higher than the dead water level; The water pressure of the cylindrical water space in a filled state is greater than the outflow water pressure of the water outlet.

2. A vertical shaft water inlet and outlet structure based on the outlet design method for improving vertical shaft outflow according to claim 1, comprising a water flow channel, the water flow channel having a vertical section, the upper end of the vertical section being a water inlet and outlet, and diversion components being evenly distributed around the water inlet and outlet, characterized in that: The upper part of the diversion component is arranged on a cylindrical retaining wall around the water inlet and outlet to form a stop structure, and the upper edge height of the cylindrical retaining wall is higher than the dead water level of the reservoir area of ​​the pumped storage power station.

3. The water inlet and outlet structure according to claim 2, characterized in that: The vertical shaft water inlet and outlet structure includes an annular cover plate, which is arranged between the diverter member and the cylindrical retaining wall. The annular cover plate forms an annular member with an opening and supported by the diverter member. The cylindrical retaining wall is arranged on the annular cover plate.

4. The water inlet and outlet structure according to claim 3, characterized in that: The opening diameter of the annular cover plate is greater than 2 / 3 of the diameter of the circumscribed circle of the annular cover plate.

5. The water inlet and outlet structure according to claim 2, characterized in that: The water flow channel is composed of a vertical diffusion section, a straight pipe section, a bend section and a gradual section in sequence from the water inlet and outlet. The water inlet and outlet are arranged at the upper end of the vertical diffusion section.

6. The water inlet and outlet structure according to claim 2, characterized in that: The diverter components are diverter piers that are evenly spaced around the water inlet and outlet in an annular direction.

7. The water inlet and outlet structure according to claim 3, characterized in that: The opening diameter of the annular cover plate is smaller than the inner diameter of the cylindrical retaining wall, and the water flowing upward from the water outlet forms a lateral backflow after passing through the opening of the annular cover plate.

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