3. A Steam Turbine is a device that extracts
Thermal Energy from pressurized Steam
and uses it to do Mechanical Energy on a
rotating output shaft. Steam Turbine is
device where Kinetic Energy (Heat)
converted into Mechanical Energy (in shape
of rotation). The Power in a steam turbine is
obtained by the rate of change in
momentum of a high velocity jet of steam
impinging on a curved blade which is free to
rotate. -The basic cycle for the steam
turbine power plant is the Rankine cycle.
The modern Power plant uses the rankine
cycle modified to include superheating,
regenerative feed water heating & reheating.
4. A. ON THE BASIS OF PRINCIPLE OF
OPERATION
B. ON BASIS OF DIRECTION OF FLOW
C. ON BASIS OF MEANS OF SUPPLY
D. ON BASIS OF NO. OF CYLINDER
5. • 1. Impulse Turbine -Pressure energy of Steam is
converted into Kinetic Energy. Impulse action of high
velocity jet of steam, due to change in its direction is
used to rotate the turbine shaft.
• 2. Reaction Turbine -Reaction force due to expansion
of high pressure steam when it passes through a set of
moving and fixed blades is used to rotate the turbine
shaft. Due to expansion of steam, pressure drop occurs
continuously over both fixed and moving blades. This
pressure difference exerts a thrust on the blades. The
resulting reaction force imparts rotary motion.
6. • Radial Flow: A turbine may also be constructed so that the
steam flow is in a radial direction, either toward or away from
the axis. In radial flow, auxiliary turbine such as may be used
as a pump drive. The radial turbine is not normally the
preferred choice for electricity generation and is usually only
employed for small output applications
• Axial Flow: The great majority of turbines, especially those of
high power, are axial flow. In such turbines the steam flows in
a direction or directions parallel to the axis of the wheel or
rotor. The axial flow type of turbine is the most preferred for
electricity generation as several cylinders can be easily
coupled together to achieve a turbine with a greater output. .
• Tangential flow: In this turbine steam flows in tangential
direction.
7. • 1.Single Pressure- There is single source of supply
• 2.Mixed or dual pressure- There are 2 sources of
steam usually used in l.p or h.p stages
• 3. Reheated turbine- During its passage through
turbine system may be taken out to be reheated in a
reheater incorporated in a boiler and returned at
high temperature to be expanded.
8. 1.SINGLE CYLINDER- When all stages of turbine
are housed in one casing it is called single cylinder
2.MULTI CYLINDER- In large output turbine, the
number of stages needed comes so high that
bearings are required to support the shaft. Under this
circumstances multicylinder are used.
9. • PARTS-
• 1. Casing
• 2. Nozzle- Pressure energy of Steam is
converted into Kinetic Energy
• 3.Turbine Blade – Convert kinetic energy into
mechanical work.
• 4.Rotor
• 5.Shaft
• PRINCIPLE
• In this type, the drop in pressure takes
place in fixed nozzles as well as moving
blades. The pressure drops suffered by
steam while passing through the moving
blades causes a further generation of
kinetic energy within these blades, giving
rise to reaction and add to the propelling
force, which is applied through the rotor to
the turbine shaft. The blade passage cross-
sectional area is not varied.
10. • The velocity of Rotor is too high for practical
purpose
• The velocity of steam leaving the turbine is
considerably high and hence there is a loss in
Kinetic Energy
• These problems can be overcome by expanding
the steam in different stages. This is known as
Compounding.
11. PARTS-
1.Casing.
2.Fixed Blades-Performs the function of Nozzle in
Impulse turbine. It directs steam to
adjacent moving blade.
3.Moving Blades
4.Shaft
5.Rotor
PRINCIPLE- High pressure steam directly
supplied to turbine blades with out nozzles. Steam
expands (diameter increases) as it flows through
fixed and moving blades Continuous drop of
pressure. Produces reaction on blades Reaction
causes rotor to rotate. Propulsive force causing
rotation of turbine is the reaction force. Hence
called reaction turbine. Eg: Parson’s Turbine
12. • The extreme high speed of Impulse
Turbine of the order of 30,000rpm,
cannot be directly used for practical
purpose.
• To reduce the speed more than one set
of blades are used. This is called
compounding.
• There are three types of compounding
1.Velocity Compounding
2. Pressure Compounding
3.Pressure – Velocity Compounding
13. • PRESSURE COMPOUNDING
• Pressure energy of steam
absorbed in stages. Expansion of
steam takes place in more than
one set of nozzles. Nozzles
followed by set of moving blades
Pressure energy of steam
converted into kinetic energy in
nozzles
• Kinetic energy transformed to
mechanical work in moving
blades. No change in pressure in
blades
14. • Velocity Compounding
• Velocity of steam absorbed in
stages Moving and fixed blades
placed alternatively. Entire pressure
drop takes place in nozzle. Kinetic
energy of steam converted into
mechanical work
• Velocity reduced to intermediate
velocity in the 1st row of moving
blades Fixed blade direct steam to
2nd set of moving blades. Velocity
further reduced in 2nd set of moving
blades
15. • Pressure Velocity Compounding
• Combination of pressure compounding
and velocity compounding. In a 2 stage
pressure velocity compounded turbine –
total drop in steam pressure carried out
in 2 stages. Velocity obtained in each
stage is compounded.
• Pressure Velocity Compounding 1st
stage and 2nd stage taken separately
are identical to velocity compounded
turbine. Combines advantages of
pressure and velocity compounding.
16. Applications of the principles generally called, reaction and impulse
often appear in the same turbine, and either is adopted without
hesitation as may best suit a particular design, size of unit, or place
in a unit. Impulse turbines of low output are less costly and more
efficient than reaction turbines, but with increase of size these
differentials disappear, and in the large sizes there is little to choose
as to efficiency or as to cost for equal efficiency. High efficiency is
expensive in either type, but it cannot be said that either has any
absolute superiority
17. • 01) Thermal Efficiency of a
Steam Turbine is much higher
than that of a steam engine.
• 02) The Steam Turbine
develops power at a uniform
rate and hence does not
required Flywheel.
• 03) If the Steam Turbine is
properly designed and
constructed then it is the most
durable Prime Mover.
• 04) In a steam turbine there is
no loss due to initial
condensation of steam.
• 05) In Steam Turbine no
friction losses are there.
18. • 1)High efficiency is ordinarily
obtained only at high speed.
• 2)Gas turbine locomotives
had similar problems,
together with a range of other
difficulties.
• 3) These devices are heavy
and cumbersome.
• 4) Turbines can rotate in only
one direction.
