Turbines used in industry.

3. Principle
It changes thermal energy to mechanical energy.
 Heat (thermal energy) produces steam pressure, and the
steam pressure is converted to steam velocity by the nozzle.
After steam strikes the buckets, steam velocity decrease.
 The rotor turns and produces mechanical work. Means
Rotation of rotor.

4. Operation principle
 The flow of steam into the steam chest is controlled by the
governor valve. By controlling the amount of steam, the
governor valve controls the output of mechanical energy.
 For the steam to flow into the casing through the nozzle, the
steam pressure in the casing must be lower than the steam
pressure in the steam chest..
 The high – velocity steam directed toward the buckets is an
impelling force (impulse) which causes the rotor to turn.
The buckets are mounted on a wheel
rather than directly on the shaft and
the nozzle or nozzles are located in
the wall of the steam chest.

5. Classification of Steam turbines:
Based on exhaust condition:
CONDENSING
BACK- PRESSURE
EXTRACTION
INDUCTION
Based on stage design:
Impulse
Reaction
Based on steam flow:
Axial flow
Radial flow
Mixed flow
Based on stages:
Single stage
Multi stage

6. Condensing Turbines
 condenser at the exhaust
 low pressure at the exhaust by
heat removal
 Utilize all of the available
thermal energy present in the
steam.
 Since large pressure drops are
common in condensing
turbines, the steam pressure is
usually reduced in steps.
Condensing turbines are
usually multi-stage turbine.

7. BACK- PRESSURE TURBINE
# Back pressure turbine is operated in back
pressure which is higher pressure than
atmospheric pressure.
# The exhaust steam can be used effectively
in any other machine and finally steam
converted to condensed water which returns
to boiler.

8. Extraction and Induction
Extraction:
Steam removed from a stage
can be used for processes that
need steam at pressures and
temperature above the
pressure and temperature of
the exhaust.
Removing steam at intermediate
stage is Extraction.
Induction:
Some times excess steam is
available in the plant, at the
pressure of a turbines
intermediate stage.
This steam can be induced into the
turbine at that stage.
Some steam may be removed from
or added to a stage before it reaches
the exhaust.

9. Impulse
The high – velocity steam
directed toward the buckets
is an impelling
(impulse) force
which causes the rotor to turn.
1. All the steam expansion
occurs through a stationary
nozzle.
2. Steam dose not expand to
a great extent in the bucket.

10. Reaction turbines
Reaction turbine:
The steam expands as it
flows
through the bucket.
1. All expansion occurs
in the
buckets mounted on
the rotor.
2. Require more stages
than impulse turbine

11. Single-stage
Single stage
1. One wheel.
2. Pressure is reduced
in one stage

12. Multi -stage
Multi stage
1. More than one wheel.
2. Pressure is reduced
in stages
(Turbine having large
pressure drops
between inlet and
exhaust are usually
multi-stage turbines)

13. Look at the drawing:
 All the wheels are mounted
on one shaft.
 Each stage is isolated by a
diaphragm which holds the
nozzles.
 Instead of one large nozzle,
a row of smaller nozzles
can be used.
There is row of nozzles per
stage.

14. Governors
The governor valve:
1. Regulates the amount of steam AS REQUIRED into the
turbine.
2. It is used to control turbine speed.
LET US SEE---- HOW

15. First … What is the governor?
It is a mechanism which opens and closes the governor valve.
For example, fly ball governor.
The drawing shows a fly ball governor:
 As the governor turns, the centrifugal force moves the fly
balls further apart.
 At low speed, the force of the spring keeps the fly balls
together.
 At higher speeds, the fly balls move further apart. The
faster the governor turns, the fly balls moves further away
from the center.

16. Second … Operation of the governor
valve
1- When the turbine is not
operating, the spring holds
the fly balls close to the
shaft. Before the turbine is
started, the governor
valve is wide open.

17. 2- As the shaft approaches
operating speed, spring
tension is overcome by the
centrifugal force,
and the balls move away from
each other, the governor valve is
Pushed to closed.
When the turbine reaches
operating speed, the governor
valve allows less steam in than
at startup, and turbine stops
accelerating.

18. 3- If the turbine speed is
too fast, the governor
valve will be closed.

19. Over speeds Trip
 If all loads are suddenly removed from a fully-loaded
turbine, the turbine may over speed.
 Some times the governor reacts too slowly or fails to respond at
all.
 If the steam is not shut off promptly, the turbine over speeds
until it flies apart.
A trip pin in the turbine shaft is used to shut off the steam flow in
the shaft.

20. 1. At normal speeds the
trip pin remains inside
the shaft by a spring.
2. If the turbine over
speeds, the pin is
ejected from the shaft
by centrifugal force.
The drawing shows a trip pin in the
shaft.

21. Look at the drawing
1. When the turbine over speeds, the extended pin strikes
the over speed trip.
2. The trigger releases a latch holding the trip lever, which
is then pulled down by a spring. The force of the spring
closes the trip valve which closes and cuts off the steam
flow to the steam chest.
3. The turbine stops.

22. Main Parts of steam turbine
Rotor
Steam chest
Casing
Over speed trip system
Governor system