We have previously introduced that the hydraulic turbine is divided into an impact turbine and an impact turbine. The classification and applicable head heights of impact turbines were also introduced before. Impact turbines can be divided into: bucket turbines, oblique impact turbines and double-click turbines, which will be introduced below.
The runner of the impingement turbine is always in the atmosphere, and the high-pressure water flow from the penstock has been transformed into a high-speed free jet before entering the turbine. changes, so that most of its kinetic energy is transferred to the vanes, driving the runner to rotate. During the entire process of the jet impinging on the impeller, the pressure in the jet remains basically unchanged, which is approximately atmospheric pressure.
Bucket turbine: also known as shearing turbine, as shown in the figure. The high-speed free jet from the nozzle strikes the vanes vertically along the tangential direction of the runner circumference. This type of turbine is suitable for hydropower stations with high head and small flow, especially when the head exceeds 400m, due to the limitations of structural strength and cavitation, the Francis turbine is not suitable, and the bucket type turbine is often used. The applied water head of the large-scale bucket turbine is about 300-1700m, and the applied water head of the small bucket-type turbine is about 40-250m. At present, the maximum head of the bucket turbine has been used at 1767m (Austria Lesek Power Station), and the design head of the bucket turbine of the Tianhu Hydropower Station in my country is 1022.4m.
Inclined type turbine
The free jet from the nozzle enters the vane from one side of the runner and exits the vane from the other side in a direction at an angle to the plane of rotation of the runner. Compared with the bucket type, its overflow is larger, but the efficiency is lower, so this type of turbine is generally used in small and medium-sized hydropower stations, and the applicable head is generally 20-300m.
The jet from the nozzle impinges on the runner blades twice successively. This kind of turbine is simple in structure and easy to manufacture, but has low efficiency and poor runner blade strength. It is only suitable for small hydropower stations with a single output of no more than 1000kW, and its applicable water head is generally 5-100m.
These are the classifications of impact turbines. Compared to impact turbines, there are fewer subclasses of impact turbines. However, in areas with high water difference, impact turbines are more effective, such as the Yarlung Zangbo River in my country, where the drop reaches more than 2,000 meters, and it is unrealistic to build dams at the same time. Therefore, the impact turbine has become the best choice.
Post time: Jul-28-2022