The Francis turbine is a reaction turbine that was invented in 1848 by James B. Francis, an English engineer living in America. This is a reaction turbine because it exploits the pressure differential between the runner inlet and outlet.
It is a ‘centripetal’ turbine: the water reaches the wheel via a snail-shaped conduit, which feeds all the blades on the distributor, which it turn direct the flow towards the blades on the wheel.
The flow is regulated by varying the opening of the distributor blades, the various runner ones instead are fixed. For this reason the Francis turbines are less “elastic” than Pelton or Kaplan ones regarding the flow change, but on the other hand have the highest maximum efficiency (also higher than 92%).
A diffuser is located at the outlet of the runner to allow the recovery of a part of the kinetic energy and to carry the fluid to the outlet channel.
Our Francis turbines can be installed on pressure heads of between 20 and 300 meters, and can be horizontal or vertical axis.
http://www.ghiggia.it/en/products/francis-turbines#sigProGalleriac4a63b609c
