There are many types of hydroelectric generators. Today, I will introduce the axial flow hydroelectric generators in detail. The application of axial flow turbine generators in recent years is mainly the development of high head and large size. Domestic axial-flow turbines are developing rapidly. The two axial-flow paddle-type turbines installed at the Gezhouba Hydropower Station have been built. One of them has a diameter of 11.3 meters, which is currently the largest of its kind in the world. . Here are the advantages and disadvantages of axial flow turbines.
Advantages of axial flow turbine
Compared with Francis turbines, axial flow turbines have the following main advantages:
1. High specific speed and good energy characteristics. Therefore, its unit speed and unit flow are higher than that of a Francis turbine. Under the same water head and output conditions, it can greatly reduce the size of the turbine generator unit, reduce the weight of the unit, and save material consumption, so it is economical. high.
2. The surface shape and surface roughness of the runner blade of the axial flow turbine can easily meet the requirements in the manufacturing. Because the blades of the axial-flow rotary-paddle turbine can rotate, the average efficiency is higher than that of the mixed-flow turbine. When the load and water head change, the efficiency does not change much.
3. The runner blades of the axial-flow paddle turbine can be disassembled, which is convenient for manufacturing and transportation.
Therefore, the axial flow turbine can maintain stability in a larger operating range, with less vibration, and higher efficiency and output. In the low-head range, it has almost replaced the Francis turbine. In recent decades, both in terms of single unit capacity and use of water head, there has been a great development, and its application is also very wide.
Disadvantages of axial flow turbine
However, the axial flow turbine also has shortcomings and limits its scope of application. The main shortcomings are:
1. The number of blades is small, and it is cantilever, so the strength is poor, and it cannot be used in medium and high head hydropower stations.
2. Due to the large unit flow rate and high unit speed, it has a smaller suction height than a Francis turbine under the same head condition, resulting in a large excavation depth for the foundation of the power station and a relatively high investment.
According to the above-mentioned shortcomings of axial flow turbines, high-strength anti-cavitation new materials are used in turbine manufacturing and the force of blades is improved in the design, so that the application head of axial flow turbines is continuously improved. At present, the application head of the axial-flow paddle turbine is 3 to 90 m, and it has entered the area of the Francis turbine. For example, the maximum single-unit output of foreign axial-flow paddle turbines is 181,700 kW, the maximum water head is 88m, and the runner diameter is 10.3m. The maximum single-machine output of the axial-flow paddle turbine produced in my country is 175,000 kW, the maximum water head is 78m, and the maximum runner diameter is 11.3m. The axial-flow fixed-propeller turbine has fixed blades and simple structure, but it cannot adapt to hydropower stations with large changes in water head and load. It has stable water head and serves as a base load or multi-unit large-scale power station. When the seasonal power is abundant, economic comparison is also possible. It can be considered. Its applicable head range is 3-50m. Axial-flow paddle turbines generally use vertical devices. Its working process is basically the same as that of Francis turbines. The difference is that when the load changes, it not only regulates the rotation of the guide vanes. , While also adjusting the rotation of the runner blades to maintain high efficiency.
Before, we also introduced Francis turbines. Among the turbine generators, there is still a big difference between Francis turbines and axial flow turbines. For example, the structure of their runners is different. The blades of Francis turbines are almost parallel to the main shaft, while the axial flow turbines are almost perpendicular to the main shaft.
Post time: Nov-11-2021
