A Francis turbine is a type of hydropower reaction turbine that contains a runner that has water passages through it formed by curved vanes or blades. The runner blades, typically 9 to 19 in number, cannot be adjusted. As the water passes through the runner and over the curved surfaces, it causes rotation of the runner. The rotational motion is transmitted by a shaft to a generator.
The Francis turbine has a wide range of applications and can be used for fall heights of 2–800 meters. The largest Francis turbines have an output of 750 MW. Compare with Kaplan turbine and Pelton turbine.