Application of Francis Turbines
Large Francis turbines are individually designed for each site to operate at the highest possible efficiency, typically over 90%. Francis type units cover a wide head range, from 20 meters to 700 meters, and their output power varies from just a few kilowatts up to 1 GW. Francis turbines may be designed for a wide range of heads and flows.
Some Terminology Related with Turbine Speed
The specific speed of a turbine characterizes the turbine's shape in a way that is not related to its size. This allows a new turbine design to be scaled from an existing design of known performance. The specific speed is also the main criteria for matching a specific hydro site with the correct turbine type. The specific speed is the speed of the turbine for a unit head when it produces unit power.
The runaway speed of a water turbine is its speed at full flow, and no shaft load. The turbine will be designed to survive the mechanical forces of this speed. The manufacturer will supply the runaway speed rating.