2. Francis Turbine
Francis Turbine
Francis Turbine
• A Francis turbine is a mixed flow turbine in which the water enters at the
circumference of the runner and travels towards the axis of the runner. Finally,
it comes out axially along the shaft.
• It operates under medium heads and requires medium quantity of flow.
• The water through the guide vanes and then through runner vanes,
transferring its energy to the runner.
• Finally, the water is discharged into the tailrace
through a draft tube.
4. Main Components
Main Components
Main Components
Penstock
scroll casing
guide mechanism
runner & runner vanes
draft tube
A francis Turbine has the following main Components
5. PENSTOCK - It is the waterway used to carry the water
from the reservoir to the turbine
SCROLL CASING - It is the casing around the turbine wheel and it
evenly distributes the water around the circumference of the wheel.
GUIDE MECHANISM- This reaction is connected to the turbine
component spiral casing. Material for the guide vanes is usually cast
steel.
RUNNER AND RUNNER VANES- It is a circular wheel on which a series
of curved blades are fixed.Made of iron or stainless steel
6. In operation, water from the reservoir (dam) flows through
the penstock and enters the spiral casing.
As the water flows through the tapped spiral casing a part of its
potential energy is converted into kinetic energy.
Water flows through the guide blades, gets deflected and then
flows radially inwards to the outer diameter of the runner.
The water then moves over the moving blades in the radial direction and
is finally discharged to the tailrace axially from the centre of runner
through a draft tube.
7. During its flow over the runner blades, the blade passages acts as
nozzle ,and the remaining parts of potential energy is converted into
kinetic energy.
Here, the jet of water does not have an effect on the runner ,they
are leaving the runner at high velocity.
Since the water leaves the blades at high velocity, there is a
reaction force on the runner. This force sets the runner into
rotatory motion.
Hence the shaft connected to the runner also rotates there by
doing useful work.The shaft in turn drives the generator to
produce electricity.
