Steam turbines use the pressure energy of steam to power rotation of a shaft. There are two main types: impulse turbines, where steam jet kinetic energy changes the turbine blades' momentum; and reaction turbines, where continuous steam pressure drop over fixed and moving blades provides rotational force. Compounding involves using multiple stages to reduce turbine speed for practical use, through either velocity compounding by absorbing steam kinetic energy in stages, pressure compounding by expanding steam pressure in nozzles, or a combination of both approaches in pressure-velocity compounding turbines.

1. STEAM TURBINES
Prepared by,
M.S.Steve,
Assistant Professor,
Amal Jyothi College of Engineering, Kanjirapally.
Email: msstevesimon@gmail.com

2. Steam Turbines
“Steam Turbine is a prime-mover in which
Pressure energy of steam is transformed
into Kinetic energy, and later in its turn is
transformed into the mechanical energy
of rotation of turbine shaft”
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3. Classification based on
Principle of Action
1.Impulse Turbine
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
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
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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.
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Impulse Turbine
1.
2.
3.
4.
5.
Casing
Nozzle – Pressure
energy of Steam is
converted into Kinetic
Energy
Turbine Blade –
Convert kinetic
energy into
mechanical work.
Rotor
Shaft

5. Impulse turbine - Working







High pressure steam from boiler is
supplied to fixed nozzles.
Nozzle – Pressure falls from boiler
pressure to condenser pressure
Reduction in pressure increases velocity.
High velocity steam impinges on moving
curved vanes
Causes change in momentum
Impulsive
force on blades.
Pressure remains constant when steam
flows through blades.
Eg: De Lavel Turbine
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6. msstevesimon@gmail.com
Impulse Turbine

7. Disadvantages of Impulse Turbine

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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.
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8. Reaction Turbine
1.
2.
•
•
3.
4.
5.
Casing
Fixed Blades
Performs the
function of Nozzle
in Impulse
turbine.
It directs steam
to adjacent
moving blade.
Moving Blades
Shaft
Rotor
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Working




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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

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Reaction Turbine

11. Compounding of Impulse Turbine


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
Velocity Compounding
Pressure Compounding
Pressure – Velocity Compounding
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12. Velocity
Compounding .. 1
1.
2.
3.
4.
5.
Nozzle
Moving Blades
Fixed Blades
Rotor
Shaft
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13. Velocity
Compounding .. 2
•
•
•
•
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 in 2 stages in
figure
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14. Velocity
Compounding .. 3
•
•
•
•
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
Eg: Curtis Turbine
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15. Velocity
Compounding .. 4
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16. Pressure
Compounding ..1
1.
2.
3.
4.
5.
Nozzle
Moving Blades
Casing
Rotor
Shaft
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17. Pressure
Compounding ..2
•
•
•
•
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
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18. Pressure
Compounding ..3
•
•
Kinetic energy
transformed to
mechanical work in
moving blades.
No change in
pressure in blades.
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19. Pressure
Compounding ..4

20. Pressure Velocity
Compounding..1
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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.
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21. Pressure Velocity Compounding..2

22. Pressure Velocity
Compounding..3
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1st stage and 2nd stage taken separately are
identical to velocity compounded turbine.
Combines advantages of pressure and
velocity compounding.
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23. Pressure Velocity
Compounding..4

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27. Thank you…!