# Francis Turbine Working Principle - Ishwaranand

## Francis Turbine

 Image Source ~ Crafted With ©Ishwaranand - 2020 ~ Image by ©Ishwaranand

### Main parts of a Francis Turbine are

• Penstock: That is a large size conduit which conveys water of the upstream of the dam/reservoir before the turbine runner.
• Spiral/scroll casing: This constitutes a closed passage whose cross-sectional space gradually decreases along each flow direction; some area is maximum at the inlet including nearly zero at any exit.
• Guide vanes/wicket gates: Certain vanes direct the water above the runner at an angle appropriate so the design. Each motion to them is given by means regarding a handwheel either automatically with a governor.
• Governing mechanism: This changes the position of one guide blades/vanes to affect a variation in water flow rate during the load conditions next to the turbine change.
• Runner and runner blades: Special driving force on the runner is both due to impulse further reaction effects. A unique number of runner blades usually ranges between 16 to 24.
• Draft tube: That is a gradually expanding tube which discharges water, passing within the runner, into the tailrace.

#### Velocity Diagram also Work Done like Francis Turbine

 Image Source ~ Crafted With ©Ishwaranand - 2020 ~ Image by ©Ishwaranand
Some work done per second at the runner with water is
=pav1[Vw1u1+-Vw2u2]
pQ[Vw1u1+-Vw2u2]
(As av1 = Q)
Where,
Vw1= Velocity of whirl at the inlet
Vw2 = Velocity of whirl at an outlet
u1 = Tangential velocity at inlet
= Ï€D1N/60,
Where,
D1 = Outer diameter of the runner
u2 = Tangential velocity at outlet
= Ï€D2N/60,
Where,
D2 = Inner diameter of a runner,
N = Speed of turbine in RPM
The work is done per second per unit weight of water per second
(pQ[Vw1u1+-Vw2u2]) / pQg
=(1/g)[Vw1u1+-Vw2u2]
+ve sign acts taken if angle Î² exists an acute angle.
If Î² is an obtuse angle then –ve sign is taken.
If Î² = 90o, then and work done per second per unit weight of water per second is
=(1/g)[Vw1u1]