page_title: Francis turbine
section_title: Application
hierarchical_section_title: Francis turbine / Application
caption_attribution_description: The water turbine. Taken in the plant that manufactures the water turbines, Zurich, Switzerland.
context_page_description: The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts.
  Francis turbines are the most common water turbine in use today. They operate in a water head from 40 to 600 m and are used primarily for electrical power production. The electric generators that most often use this type of turbine have a power output that generally ranges from just a few kilowatts up to 800 MW, though mini-hydro installations may be lower. Penstock diameters are between 3 and 33 ft. The speed range of the turbine is from 75 to 1000 rpm. A wicket gate around the outside of the turbine's rotating runner controls the rate of water flow through the turbine for different power production rates. Francis turbines are almost always mounted with the shaft vertical so as to isolate water from the generator. This also facilitates installation and maintenance.
context_section_description: Francis turbines may be designed for a wide range of heads and flows. This versatility, along with their high efficiency, has made them the most widely used turbine in the world. Francis type units cover a head range from 40 to 600 m (130 to 2,000 ft), and their connected generator output power varies from just a few kilowatts up to 800 MW. Large Francis turbines are individually designed for each site to operate with the given water supply and water head at the highest possible efficiency, typically over 90%.
  In contrast to the Pelton turbine, the Francis turbine operates at its best completely filled with water at all times. The turbine and the outlet channel may be placed lower than the lake or sea level outside, reducing the tendency for cavitation.
  In addition to electrical production, they may also be used for pumped storage, where a reservoir is filled by the turbine (acting as a pump) driven by the generator acting as a large electrical motor during periods of low power demand, and then reversed and used to generate power during peak demand. These pump storage reservoirs act as large energy storage sources to store "excess" electrical energy in the form of water in elevated reservoirs. This is one of a few methods that allow temporary excess electrical capacity to be stored for later utilization.
caption: Small Swiss-made Francis turbine
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