A Francis turbine is a type of water turbine used for generating electricity in hydroelectric power plants. It operates by converting the energy of flowing water into mechanical energy. The design features a spiral casing that directs water to the turbine runner, which has curved blades that help maximize efficiency. These turbines are particularly effective for medium to high water heads and can operate in a wide range of flow conditions. Francis turbines are named after their inventor, James B. Francis, who developed this design in the 19th century, making it one of the most widely used turbine types in the world today.