Shenyang Getai Hydropower Equipment Co., Ltd.

What Is The Structure Of The Francis Turbine?

Nov. 09, 2019

The Francis Turbine is a type of turbine that was invented by American engineer Francis in 1849. The Francis turbine is a type of counter-turbine that has a wide range of applications and can be used from 20 to 700 m. The utility model has the advantages of simple structure, convenient manufacture and installation, reliable operation, high efficiency and low cavitation coefficient.

Francis Turbine

Francis Turbine

The Kaplan Turbine Design Factory now introduces this turbine structure. The water inlet component of the turbine is a volute with a steel plate lining. The seat ring struts are also called fixed guide vanes. The guide vanes are arranged around the runner. The seat ring struts have a strong upper ring a and a lower ring b. The shell and the upper and lower rings are welded together. The guide vane bushing (steel or nylon material) is supported on the bottom ring and the sleeve fixed to the top cover. The bottom ring is fixed to the lower ring of the seat ring. The top cover is connected to the upper ring of the seat ring by screws. The water guiding transmission mechanism is composed of a rotating arm, a connecting rod and a control ring which are disposed on the journal of the water guiding blade. The change in the opening degree 0a of the vane (the shortest distance from the outlet end of the vane to the back of the adjacent vane) is achieved by the two servos of the water guiding mechanism and the push-pull rod transmission control loop connected to the control loop.

Since the application head of the Francis turbine is higher and the vane is subjected to a large bending load, the relative height 0b of the vane is made shorter than that of the axial flow turbine to reduce the span. In addition, as the head increases, the overcurrent of the turbine at the same power is reduced, which makes it possible to reduce the overcurrent surface of the runner. 0b generally decreases as the head increases. The gap between the vane and the bottom ring of the turbine top cover and the joint surface of the adjacent vane at the time of shutdown may leak. Seals made of rubber or metal are generally used to minimize the amount of water leakage when the water guiding mechanism is closed. In high-head turbines, special tubular seals are sometimes used, which are filled with compressed air during shutdown to completely seal the end faces.

The runner is the core component of the turbine that converts water flow energy into mechanical energy. The water flows through the water guiding mechanism into the runner. The runner consists of an upper crown, a lower ring and blades. Generally, Francis turbines have 14 to 19 blades. The blade, upper crown and lower ring form a solid overall steel structure. The crown of the runner is connected to the lower flange of the spindle. The drain cone is connected to the upper crown to eliminate the water flow whirlpool.

The runner seal is a multi-groove ring placed on the crown and lower ring of the runner. When the turbine is working, the water flow before and after the runner is high pressure and low pressure, and a vacuum is often formed after the runner. Therefore, part of the water flow during the operation of the turbine is unnecessarily leaked through the gap between the rotating and non-rotating components, thereby reducing the efficiency of the turbine. The seal ring is designed to reduce flow leakage. As the water passes through the space of the seal ring, it is subjected to a partial hydraulic block that is suddenly enlarged and contracted, resulting in a hydraulic loss, thereby reducing the flow rate and reducing the flow rate through the slit.

The pressure reducing hole communicates with the upper chamber of the rotating wheel and the low pressure region below the rotating wheel, thereby reducing the axial thrust received by the thrust bearing. When there is a pressure reducing hole, the upper crown of the rotating wheel must be provided with a sealing device.

The above is the description of the structure of the Francis turbine, hoping to help everyone. In addition, if you are interested in Francis turbines, you can contact us, we can provide you, and we have Kaplan Turbine For Sale. Welcome everyone to buy.

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