Turbines can be either impulse or reaction turbines. Impulse turbines use nozzles to direct steam onto curved blades with a bucket-like shape, extracting energy from the steam's kinetic energy. Reaction turbines have fixed and moving blades, with the fixed blades acting as nozzles to increase the steam's velocity before it passes over the moving blades. Common impulse turbines include Pelton wheels, while common reaction turbines are Francis and Kaplan turbines. Turbines are highly efficient machines that convert the energy in fluids like steam or water into useful rotational work, and they are widely used in applications like power generation, ships, aircraft, and pumps.

1. ANKIT GUPTA,
4JC13ME007
ROLL NO: 07

2. Turbines
• A turbine is a rotary engine that exerts energy from a
fluid flow and converts it into useful work.

3.  There are two basic types of turbines according to
the mode of steam.
1. Impulse turbine
2. Reaction turbine

4. Impulse turbine
Working principle
 It runs by impulse of steam.
 Nozzle directs the steam on the curved blades, which
causes them to rotate.
 The blades are in the shape of buckets.

5.  The energy to rotate an impulse turbine is derived
from the kinetic energy of the steam flowing through
the nozzle.
 The potential energy is converted into kinetic energy
when it passes through the nozzle.
 The velocity of steam is reduced when it passes over
the blades.

6.  In an Impulse turbine, the whole of the available energy of the
fluid is converted to Kinetic Energy before the water acts on the
moving parts of the turbine.
 Pelton Wheel is an example of Impulse turbine.
Pelton Wheel (Impulse Turbine)

7. Pelton Wheels in a hydroplant Components in a Pelton Wheel
Water is blasted at these cups by one or more jets mounted in the
surrounding casing. Momentum is transferred from water to cups,
and a torque is created, causing the wheel to rotate.
This type of turbine is highly efficient.

8. Reaction turbine
Working principle
 It has no nozzle.
 Two rows of moveable blades are separated by one row of
fixed blades.
 Fixed blades are attached to the casing & act as nozzles.
 Blades are like the wings of a plane.

9.  Velocity of steam is increased when it passes through
the fixed blades.
 The enthalpy drop in moving blades is called degree of
reaction.
 A common arrangement can have 50% of enthalpy
drop in moving blades, it is said to have 50% reaction.
 If all enthalpy drops in moving blades then it is said to
be 100% reaction.

10.  There are two main types of Reaction Turbine – Francis and
Kaplan Turbines.
Sectional and Top View of a Francis Reaction Turbine

11. Francis Turbine

12. A Francis turbine runner, rated at nearly one million hp
(750 MW), being installed at the Grand Coulee Dam,
United States.

13. Sectional View of a Kaplan Reaction Turbine

15. Various types of water turbine runners.
From left to right: Pelton Wheel, two types
of Francis Turbine and Kaplan Turbine

16.  Pressure velocity graph of impulse and reaction
turbines.

17. Difference between impulse and
reaction turbine
S.NO Impulse turbine Reaction turbine
1.
The steam flows through the
nozzle and impinges on the
moving blades.
The steam first flows through the
guide mechanism and then through
the moving blades.
2.
The steam impinges on the
buckets with kinetic energy.
The steam glides over the moving
vanes with pressure and kinetic
energy.
3.
The steam may or may not be
admitted over the whole
circumference.
The steam pressure is reduced
during its flow through the moving
blades.
4. The blades are symmetrical The blades are not symmetrical

18. Euler Head and Efficiencies of Hydraulic Turbines
 Efficiency of turbines is a function of the available head.
 Euler's Head: It is defined as energy transfer per unit weight.
 Hydraulic Efficiency - It is the ratio of power developed by the
runner to the head of water (or energy) actually supplied to the
turbine i.e.
 Mechanical Efficiency - It is the ratio of actual work available
at the turbine shaft to energy imparted to the wheel.
 Overall Efficiency – The overall efficiency is based on the
useful work output divided by the water power input.

19. Efficiency
 To maximize the efficiency of steam turbine the steam
is expanded, generating work in a number of stages.
 Multiple stages turbines are highly efficient.
 Most steam turbines use a mixture of both impulse
and reaction design.
 Higher pressure sections are impulse type and lower
pressure sections are reaction type.

20. Advantages of steam turbine
 It can develop higher speeds.
 The steam consumption is less.
 All the parts are enclosed in a casing so it is safe.
 It requires less space and lighter foundations.
 There is very less friction in the turbine due to few
sliding parts.

21. Uses
 Turbines are used in force draft blowers, pumps and
main propulsion turbines.
 Used in the jet engines and air crafts.
 They are also used in power plants , ships and
submarines.

22.  The working principle of a gas turbine also known as
‘ Internal Combustion Turbine ’ is similar to a steam
turbine, but its working fluid is the products of
combustion of fuel with air instead of steam.
 A simple gas turbine consists of an air compressor
combustion chamber and a turbine. The function of
the air compressor is to compress the air required for
combustion.
 The fuel is burnt in the combustion chamber and the
combustion products flow through the turbine. The
function of the turbine is to convert the heat energy
into mechanical work.
GAS TURBINES AND ITS TYPES:

23.  In this type of turbine, the compressed air from an air
compressor C admitted into the combustion chamber A
through the valve U.
 When the valve U is closed, the fuel admitted into the
chamber is ignited by means of a spark plugs.
 The combustion takes place at CONSTANT VOLUME with
increase of pressure.
 The valve V opens and the hot burning gases flow to the
turbine T and finally they are discharged into the
atmosphere.
 The energy of hot gases is thereby converted into
mechanical work. These operations are repeated for
running the Turbine.
CONSTANT VOLUME GAS TURBINE :

25.  The compressor C is coupled with a turbine shaft and
it is driven by the turbine T. Air taken from the
atmosphere is compressed by the compressor to a high
pressure.
 The compressed air then flows into the combustion
chamber M where the fuel is injected y means of a
pump P..
 The fuel burns at CONSTANT PRESSURE and the hot
gases flow through the turbine and finally discharged
into the atmosphere.
CONSTANT PRESSURE GAS TURBINE:

26. CONSTANT PRESSURE GAS TURBINE :

27.  It is suitable where the supply of water is a difficult
problem.
 Water required for a steam turbine imposes a serious
problems,when it is used as a portable engine.Even in
ships, when it is floating over a vast amount of water it
produces much difficulty as sea water is not suitable
for the engine.
 A steam turbine requires a boiler for supply of steam
and it therefore requires additional space than what is
required by a gas turbine.
THE ADVANTAGES OF GAS TURBINES OVER
STEAM TURBINES:

28. THANK YOU…..!