General about types of turbine

1. PELTON TURBINE
It is a tangential flow turbine.
Leston A pelton an American engineer during 1880.

2. It consists the following main parts;
1. Spear and nozzle
2. Runner with buckets
3. Brake nozzle
4. Outer casing
5. Governing mechanism
1. Spear and nozzle:
In the downstream end of the penstock, with efficient nozzle
which converts the whole hydraulic energy into kinetic energy.
The nozzle will delivered high speed of water. To regulate the
water of flow there is a spear arrangement.
The spear can move forward or backward to increase or
decrease the nozzle flow passage.

3. 2.Runner with buckets:
It consists of circular disc with number of buckets spaced
around the periphery.
The runner is mounted on horizontal shaft with small thrust
bearings.
The buckets have a shape of the double semi-elliptical
ridge(Splitter).
The buckets have angle at outlet varies from 10o to 20o and the
water deflected from 180o to 190o .
The splitter which divides the jet into two equal portions. After
the smooth inner surface of the bucket , water leaves as its
outer edge.

4. 3.Outer casing:
 It made of cast iron or fabricated steel plates.
 There is no hydraulic function to perform.
 It is used to prevent the splashing of water and discharge to tailrace.
It also act as a safeguard against accidents.
4.Brake nozzle:
 When a nozzle is closed by the moving spear in forward direction,
the water striking on buckets gets zero.
 But the runner will revolve due to inertia. So to stop the runner there
is a small nozzle(brake nozzle).
 It will produce a jet of water at the back of the buckets. This jet of
water is called breaking jet.
5.Governing mechanism:
 It is used to regulate the water into the turbine at a constant level, so
speed of turbine gets constant.
 It automatically regulates the quantity of water flowing through the
runner with any variation of load.

5. FRANCIS TURBINE
It is an inward flow reaction turbine.
It is developed by American engineer James B.Francis
In this the water enters the runner at its outer periphery and it
leaves axially at its centre.

6. 1.Penstock:
It is large sized conduit which conveys water from dam or
anything to the runner.
It has greater size than the pelton wheel.
2.Scroll or Spiral casing:
The water from the penstock enters a scroll casing which
completely surrounds the runner.
The C/S area of scroll casing is maximum at inlet and almost
zero at outlet.
It will helps to maintain the constant velocity in the runner.
The casing is made of cast steel, plate steel or concrete
depending on the pressure to which it is subjected.
3.Speed ring or Stay ring:
From scroll casing, the water passes through a speed ring or
stay ring.

7. It consists of upper and lower rings held together by series of
fixed vanes called stay vanes.
The stay vanes are taken as half the number of guide vanes. Its
function is to direct the water from a scroll casing to the guide
vanes & also resists the load imposed on it.
It may be made of cast iron or cast steel.
4.Guide vanes or wicket gates:
From the speed ring, the water passes through a series of guide
vanes. The gates are provided all around the periphery of
turbine runner.
It is used to regulate the water to the runner as per design.
It is like a airfoil shape and may be made of cast steel or plate
steel.

8. 5.Runner and runner blades:
Runner is a circular wheel on which a series of radially curved
vanes are fixed.
This shape is used to enter the water at the outer periphery and
it leaves axially at inner periphery.
The runner made up of cast iron or stainless steel and they are
keyed to shaft.
The number of runner blades usually varies from 16 to 24.
6.Draft tube:
The water after passing through the runner is discharged to the
tailrace through a gradually expanding tube , i.e, draft tube.