Turbines are defined as the hydraulic machines which
convert hydraulic energy into mechanical energy.
This mechanical energy is used in running an electric
generator which is directly coupled to the shaft of
Thus the mechanical energy is converted into
Classification of hydraulic turbines
According to type of energy at inlet
1. Impulse turbine
2. Reaction turbine
According to direction of flow of water
1. Tangential Flow turbines
2. Axial flow turbines
3. Radial flow turbines
- Inward radial flow turbine and Outward radial flow
4. Mixed flow turbines
According to water head and quantity of water available
1. High head & small quantity of flow of water
2. Medium head & medium flow rate
3. Low head and large flow rate
According to the specific speed of the turbine
1. Low specific speed turbine ( <60 )
ex. Pelton wheel
2. Medium specific speed turbine ( 60 to 400 )
ex. Francis turbine
3. High specific speed turbine ( above 400 )
• IMPULSE TURBINE
If at the inlet of the turbine, the energy available is only kinetic
energy, the turbine is known impulse turbine.
Example: Pelton wheel turbine
• REACTION TURBINE
If at the inlet of the turbine , the water possesses kinetic energy
as well as pressure energy, the turbine is known as reaction
turbine. Example: Francis turbine , Kaplan turbine
• RADIAL FLOW TURBINE
If the water flow in the radial direction through the runner, the
turbine is called radial flow turbine
• INWARD RADIAL FLOW TURBINE
If the water flows from outward to inward radially , the turbine is
known as inward radial flow turbine.
•OUTWARD RADIAL FLOW TURBINE
If the water flow radially from inward to outwards, the turbine is
known as outward radial flow turbine.
•AXIAL FLOW TURBINE:
If the water flow through the runner along the direction parallel to the
axis of rotation of the runner, the turbine is called axial flow turbine.
•MIXED FLOW TURBINE:
If the water flows through the runner in the radial direction but leaves
in the direction parallel to axis of rotation of the runner, the turbine
is called mixed flow turbine.
• TANGENTIAL FLOW TURBINE:
If the water flows along the tangent of the runner, the turbine is
known as tangential flow turbine.
•Impulse turbine & Reaction turbine
1. Impulse turbine
a. Water from penstock to
turbine via one or more
b. Pressure energy
converted into kinetic
c. Rotation of wheel due to
tangential force created
by impact of jet.
a. Both kinetic and pressure
b. Feeding of water through
fixed blades in casing.
c. Static pressure at inlet is
greater than outlet of
d. Rotation due to impulse
reaction and due to
reduction in pressure so it is
called Reaction turbine.
IMPULSE TURBINE REACTION TURBINE
• All the potential energy
is converted into
kinetic energy by
nozzle before entering
to turbine runner.
• Flow regulations is
possible without loss.
• Unit is installed above
• Blades are only in
action when theyare in
front of nozzle.
• Only a portion of the
fluid energy istransferred
into kinetic energy
before thefluid enters the
• Flow regulation is
possible with loss.
• Unit is kept entirely
• Blades are in action at all
Designed and developed by American engineer James B.
Francis in 1848.
Head engineer in textile factory city of Lowell Massachusetts
Improved on these designs to create a turbine with 90% efficiency.
• Designed and developed by American engineer Janes B. Francis in184
• Inward reaction flow turbine
• Water head : 10 to 650 meters
• Power output range : 10 MW to 750 MW
• Speed range : 83 to 1000 rpm
• In Old Francis radial discharge at outlet
• In Modern Francis, Water enters radially from outlet periphery and
leaves the runner in the axial direction
• Main components of turbine
1. Spiral Casing 2. Guide vanes 3. Runner
4, Governing mechanism 5. Draft tube
• This is the most common turbine type in hydroelectric stations
1. Penstock :
Large diameter tube through water from dam comes to turbine inlet.
It is made from steel.
2. Spiral Casing :
a. It is a closed passage whose diameter gradually decreases along
flow of direction. Area is maximum at inlet and nearly zero at exit.
b. To maintain constant flow rate, numerous openings (wicket gates)
c. The purpose of casing to distribute water over guide vanes
and prevent formation of eddies.
d. made of cast steel, plats steel or concrete depends on head.
3. Guide vanes :
a. It is aerofoil shaped vanes fixed between two rings.
b. It convert a part of pressure energy into kinetic energy.
c. Each guide vane can rotate about it pivot centre hence it also
serves to direct the flow at design angles to the blade runners.
4. Governing mechanism :
It can change the position of guide vanes to vary the flow on
5. Runner :
a. Profile is designed so that water enter inwards in radial direction
and leave it in the axial direction.
b. Runner rotate due to impulse and reaction effects.
c. It is classified according to fast , medium & slow.
d. Made of cast iron(small unit) , stainless steel (large unit), bronze
e. It is keyed to shaft of turbine.
6. Draft tube :
a. It is gradually expanding tube which discharge water passing
through the runner to tail race.
b. Generally with increasing diameter in flow direction.
•The Pelton wheel is a water tangential flow impulse
• It was invented by Lester Allan Pelton an American
engineer in the 1870s.
• This turbine is used for high heads.
• The main components of Pelton wheel or turbine.
1. Nozzle & spear
2. Runner and Bucket
4. Breaking jet
• Nozzle & spear
a. Amount of water striking the bucket of water controlled by
spear in the nozzle.
b. Spear is conical needle which operated either by hand
wheel over automatically axially depends on size of unit.
a. It consists of circular disk on periphary of which number of
buckets evenly spaced are fixed
b. Shape of bucket is of a double hemi-spherical cup.
Each bucket is divided by spiltter which divide the jet into
c. Made of Cast iron or cast steel bronze or stainless steel
depends on head.
a. Prevent spalashing of water.
b. Act as a safe guard
c. Made of cast iron, fabricated steel
•Jet of water used to
stop runner in short
•It strikes at the back