In 1912, the Czech leader Puland proposed an axial flow turbine with an outer rim and fixed blades. After years of gradual improvement, it developed into a modern axial flow turbine, also known as Kaplan Turbine. Axial-flow propeller turbine was invented by the Austrian engineer Kaplan in 1920, so it is also called Kaplan turbine. The runner blade is generally operated by an oil pressure relay installed in the runner body, which can be rotated according to the change in water head and load to maintain the optimal cooperation between the movable guide blade angle and the blade angle, thereby improving the average efficiency. The highest efficiency of hydraulic turbines has exceeded 94%. However, this type of water turbine requires a mechanism for operating the blade to rotate, so the structure is more complicated and the cost is higher. It is generally used in large and medium-sized hydropower stations with large changes in head and output.
Axial flow turbine means that the water flow enters the runner from the axial direction and flows out from the axial direction along its blades. The impact turbine inlet that converts the water flow energy into mechanical energy is divided into axial flow paddle type according to whether its runner blade can rotate and axial flow fixed paddle type. Axial flow turbine means that the water flow enters the runner from the axial direction and flows out from the axial direction along its blades. The impact turbine inlet that converts the water flow energy into mechanical energy is divided into axial flow paddle type according to whether its runner blade can rotate. And axial flow fixed paddle type. The axial head of the axial flow turbine is generally 3-80m. An axial-flow turbine runner consists of a runner body, blades, and a drain cone. The number of blades is less than that of a mixed-flow type. The blade axis is perpendicular to the turbine axis. It is suitable for low-medium head and large-flow hydropower stations. At the same head, its specific speed is higher than that of mixed-flow turbines. Application head is about 3 to 80m. The water flow changes from radial flow to axial flow between the guide vanes and the runner, while in the runner area, the water flow maintains axial flow.
In recent years, the application of axial flow turbines has continued to develop towards high heads and large sizes. At present, the use of water head has reached more than 80 m, the single machine capacity and the size of the runner tend to increase. At present, the world's largest large-scale axial-flow propeller-type turbine is the Nembia Hydropower Station in Italy. The maximum head is 88m; the largest single-machine output is the Shulbin Hydropower Station in the Soviet Union; the rated output is 230 MW; the largest axial-flow fixed-paddle turbine is installed at the Keinzi Power Station in Nigeria.
The design and manufacturing technology of axial flow turbines in China has also developed rapidly. The two types of axial flow paddle turbines installed in the completed Gezhouba Hydropower Station (see Gezhouba Hydropower Project) have a maximum head of 27m and rated output of 175 and 129 MW. The diameters of the runners are 11.3m and 10.7m, respectively. The former is the largest runner diameter of similar turbines in the world. The axial flow paddle turbine installed at Shuikou Hydropower Station has a maximum head of 58m, a single unit rated output of 204MW, and a runner diameter of 8m.
The above is the development of the mixed flow turbine introduced by Hydraulic Turbine Generator Supplier.