F1-32 FRANCIS TURBINE
This demonstration turbine provides a simple low-cost introduction to the Francis inward flow reaction turbine showing its construction, operation and performance.
A tapering, spiral-shaped volute conveys water to the runner via a ring of guide vanes that are adjustable in angle to vary the flow through the turbine. Water enters the runner tangentially at the periphery, flows radially inward through the blades toward the hub then exits axially via a draft tube.
Power generated by the turbine is absorbed by a Prony friction brake consisting of a pair of spring balances attached to a brake belt that is wrapped around a pulley wheel driven by the runner. The load on the turbine is varied by tensioning both spring balances, which increases the friction on the pulley wheel. Brake force is determined from the difference in the readings on the two spring balances and the torque calculated from the product of this force and the pulley radius.
The head of water entering the turbine is indicated on a Bourdon gauge and the speed of rotation is measured using a non-contacting tachometer (not supplied).
Speed range: 0-4000 rpm
Diameter of Francis runner: 60mm
Number of blades on runner: 12
Number of guide vanes: 6, adjustable from fully open to fully closed
Range of spring balances: 0-50N x 0.5N
Range of Bourdon gauge: 0-2 bar
Requires Hydraulics Bench Service unit F1-10
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Determining the operating characteristics, ie power, efficiency and torque, of a Francis Turbine at various speeds and guide vane openings