There are many kinds of hydro generators. Today, let’s introduce the axial-flow hydro generator in detail. The application of axial-flow hydro generator in recent years is mainly the development of high water head and large size. The development of domestic axial-flow turbines is also fast. There are two kinds of axial-flow paddle turbines installed in the built Gezhouba hydropower station, one of which has a runner diameter of 11.3m, which is the runner diameter of similar turbines in the world. Here are the advantages and disadvantages of intermediate axial flow turbine.
Advantages of axial flow turbine
Compared with Francis turbine, axial-flow turbine has the following main advantages:
1. High specific speed and good energy characteristics. Therefore, its unit speed and unit flow are higher than that of Francis turbine. Under the same head and output conditions, it can greatly reduce the size of hydraulic turbine generator unit, reduce the weight of unit and save material consumption, so it has high economic benefits.
2. The surface shape and surface roughness of runner blades of axial-flow turbine are easy to meet the requirements in manufacturing. Because the blades of axial flow propeller turbine can rotate, the average efficiency is higher than that of Francis turbine. When the load and head change, the efficiency changes little.
3. The runner blades of axial flow paddle turbine can be disassembled to facilitate manufacturing and transportation.
Therefore, the axial-flow turbine keeps stable in a large operation range, has less vibration, and has high efficiency and output. In the range of low water head, it almost replaces the Francis turbine. In recent decades, it has made great development and wide application in terms of single unit capacity and water head.
3、 Disadvantages of axial flow turbine
However, the axial-flow turbine also has disadvantages and limits its scope of application. Its main disadvantages are:
1. The number of blades is small and cantilever, so the strength is poor and can not be applied to medium and high head hydropower stations.
2. Due to the large unit flow and high unit speed, it has a smaller suction height than Francis turbine under the same water head, resulting in large excavation depth and relatively high investment of power station foundation.
According to the above shortcomings of axial-flow turbine, the application head of axial-flow turbine is continuously improved by adopting new materials with high strength and cavitation resistance in turbine manufacturing and improving the stress condition of blades in design. At present, the application head range of axial flow propeller turbine is 3-90 m, which has entered the area of Francis turbine. For example, the output of * * * single machine of foreign axial flow propeller turbine is 181700 kW, the * * * head is 88m, and the runner diameter is 10.3M. The single output of axial flow propeller turbine produced in China is 175000 kW, the * * * head is 78m, and the diameter of * * * runner is 11.3m. Axial flow fixed propeller turbine has fixed blades and simple structure, but it can not adapt to hydropower stations with large changes in water head and load. For large hydropower stations with stable water head and serving as base load or multiple units, it can also be considered after economic comparison when seasonal electric energy is abundant. Its applicable water head range is 3-50m. Axial flow propeller turbine generally adopts vertical device, and its working process is basically the same as that of Francis turbine, The difference is that when the load changes, it not only regulates the rotation of the guide vane, but also regulates the rotation of the runner blade to maintain high efficiency.
We also introduced the Francis turbine before. Among the hydro generators, the Francis turbine is very different from the axial-flow turbine. For example, the structural forms of their runner are different. The blades of Francis turbine are almost parallel to the main shaft, while those of axial flow turbine are almost perpendicular to the main shaft.
Post time: Apr-19-2022
