Generally speaking, the inlet channel shall meet the following requirements:
① Small hydraulic loss;
(2) The flow is smooth, no vortex belt is generated in the runner under various working conditions, and the vortex belt is not allowed to enter the water pump;
(3) simple line type and convenient construction;
(4) The size is reasonable, meeting the requirements of the civil engineering and structural design of the pump house, and reducing the width of the runner and the excavation depth as much as possible to reduce the project investment.
Taking the project of Donghai Shangzha Station in Shunde District, Foshan City as an example, this paper briefly discusses some experiences in the selection and design of the inlet channel of the pumping station.
2. Project overview
The East China Sea Shangzha Station project is located in the northwest of Xingtan Town, Shunde District, Foshan City, and belongs to the seven-star William, which is connected to the East China Sea River in the interior and Ganzhuxi in the outside. Scientific papers, selection and design. This project is located at the intersection of Donghai River and Ganzhuxi River, with the pile number of 5 1+776, and is located in Seven Townships of William. The main task of this project is to improve the flood control and drainage capacity of Qixing William in Shunde District. The project scale is medium, which is the key project of drainage planning in Shunde District. Scientific papers, selection and design. Scientific papers, selection and design.
This project includes a drainage pumping station and a sluice, in which the designed drainage flow of the drainage pumping station is 30m3/s. According to the design drainage flow of pumping station and the requirements of various lift parameters, through the comparison of unit selection, it is determined to choose 5 1400ZLB-3.9 vertical axial flow pumps, with a single design flow of 6m3/s; Equipped with five TL560- 16/ 1430 high-voltage (10KV) synchronous motors, the single machine power is 560kw, and the total installed capacity of the electric platoon station is n = 5× 560 = 2800 kW. Scientific papers, selection and design.
3. Comparison of the selection schemes of the inlet channel of the pump house
According to the pump type selected by the drainage pumping station and the layout of the pump house, this project can adopt elbow-shaped, bell-shaped or dustpan-shaped intake channels.
Basic dimensions and characteristics of inlet channel form: elbow-shaped bell-shaped dustpan shape.
1, height HW/do1.5 ~ 2.241.0 ~1.41.6 ~1.75.
2. Wide bottom of inlet channel B/DO2.0 ~ 2.52.5 ~ 2.82.5
3. The distance from the water inlet to the center line of the water pump L/DO3.5 ~ 4.03.5 ~ 4.03.0.
4. The distance from the rear wall to the center line of the water pump XT/Do0.54 1.3 1.0.
5. There are simple, complex and simple runner lines.
6. Characteristic bend is the most commonly used channel in the construction of large and medium-sized pumping stations at home and abroad, and it is also a kind of inlet channel recommended by the current pumping station specification. The elbow inlet is widely used and the design method is mature, which is characterized by simple line type and convenient construction. However, the height of the runner is large, so it is necessary to dig deep into the foundation pit of the pump house. The efficiency of bell-shaped channel is not much different from that of elbow-shaped channel. Its remarkable feature is that the height of the runner is small, which can improve the elevation of the pump house floor and avoid the foundation excavation being too low. Moreover, the amount of concrete to be filled between runner and runner is small, which can save engineering investment. However, the bell-shaped runner is wider than the elbow-shaped runner, and its shape is more complicated. The dustpan-shaped flow channel was first used in some pumping stations in Holland. At present, there is no domestic standard to follow, and domestic pumping stations are rarely used. The height Hw/Do of the inlet bottom plate is similar to that of the elbow, but larger than the bell mouth, and the channel width is slightly larger than that of the elbow. Because the bottom plate is dustpan-shaped, the direction of water flow entering the inlet of the pump is not as good as that of elbow-shaped channel, which is easy to produce vortex, so the middle partition plate must be used to prevent vortex, which leads to great hydraulic loss. Its advantages are incomparable to elbow bells.
Note: Do in the table is the diameter of the pump impeller.
Through the comparison of inlet channel schemes, although the bell channel can improve the elevation of pump house bottom plate and reduce the excavation amount of pump house foundation, its channel width is wider than that of elbow channel, and the unit spacing and the total length of pump house are larger than that of elbow channel. The corresponding increase also includes the net width of intake chamber and intake forebay and the project area (land acquisition), and there is little difference in engineering quantity and investment between them. However, the shape of bell-shaped runner is more complicated, its application is less than that of elbow-shaped runner, and its design method is not as mature as elbow-shaped runner. Therefore, the bend channel is still recommended for the intake channel of this project.
4. Structural arrangement of water inlet channel
The water inlet channel of this project adopts single machine and single pipe water inlet arrangement. The inlet of the channel is 2.74 meters high and 3.0 meters wide, and it is connected with the inlet of the pump in a square to circular shape. Under the design condition, the flow velocity in the inlet section is 0.73m/s, which meets the requirements of the specification. The water inlet channel adopts reinforced concrete structure, which is integrated with the bottom plate of the pump house and becomes the block foundation of the pump house. A water inlet chamber is arranged in front of the water inlet channel, and a safety fence and an access door are arranged at the entrance of the water inlet chamber, and the safety fence and the access door are arranged in different slots. The elevation of the bottom plate of the inlet channel and inlet chamber is -3.840m, and the thickness of the bottom plate is 0.9m m.
Whether the selection and design of water inlet channel is reasonable or not affects the velocity distribution and pressure distribution at the inlet of pump impeller, and affects the actual operation performance of pump. The improper shape and size of the inlet channel may produce vortex bands in the channel and reduce the efficiency of the pump; Vortex belt entering the water pump may also cause vibration of the unit. Scientific papers, selection and design. Inlet channel is a part of hydraulic structure, and its shape and size directly affect the investment and construction difficulty of pumping station. Therefore, the reasonable selection and design of flow passage is of great significance to the operation of pump and engineering investment.
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