Steam Turbine Introduction and Familiarization.ppt

Steam turbine familiarization

1. Steam Turbine

3. PrinciplePrinciple
It changes thermal energy to mechanical energyIt 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 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.velocity decrease.
The rotor turns and produces mechanical work. Means Rotation of rotor.The rotor turns and produces mechanical work. Means Rotation of rotor.

4. Operation principleOperation principle
The flow of steam into the steam chest is controlled by the The flow of steam into the steam chest is controlled by the
governor valve. By controlling the amount of steam, the governor valve. By controlling the amount of steam, the
governor valve controls the output of mechanical energy.governor valve controls the output of mechanical energy.
For the steam to flow into the casing through the nozzle, the For the steam to flow into the casing through the nozzle, the
steam pressure in the casing must be lower than the steam steam pressure in the casing must be lower than the steam
pressure in the steam chest..pressure in the steam chest..
The high – velocity steam directed toward the buckets is an The high – velocity steam directed toward the buckets is an
impelling force (impulse) which causes the rotor to turn. impelling force (impulse) which causes the rotor to turn.
The buckets are mounted on a wheel The buckets are mounted on a wheel
rather than directly on the shaft and rather than directly on the shaft and
the nozzle or nozzles are located in the nozzle or nozzles are located in
the wall of the steam chestthe 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 TurbinesCondensing Turbines
condenser at the exhaust condenser at the exhaust
low pressure at the exhaust by low pressure at the exhaust by
heat removal heat removal
Utilize all of the available Utilize all of the available
thermal energy present in the thermal energy present in the
steam.steam.
Since large pressure drops are Since large pressure drops are
common in condensing common in condensing
turbines, the steam pressure is turbines, the steam pressure is
usually reduced in steps. usually reduced in steps.
Condensing turbines are Condensing turbines are
usually multi-stage turbine.usually multi-stage turbine.

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

8. Extraction and InductionExtraction and Induction
Extraction:Extraction:
Steam removed from a stageSteam removed from a stage
can be used for processes thatcan be used for processes that
need steam at pressures andneed steam at pressures and
temperature above thetemperature above the
pressure and temperature ofpressure and temperature of
the exhaust.the exhaust.
Removing steam at intermediateRemoving steam at intermediate
stage is stage is ExtractionExtraction..
Induction:Induction:
Some times excess steam isSome times excess steam is
available in the plant, at theavailable in the plant, at the
pressure of a turbinespressure of a turbines
intermediate stage.intermediate stage.
This steam can be induced into theThis steam can be induced into the
turbine at that stage.turbine at that stage.
Some steam may be removed fromSome steam may be removed from
or added to a stage before it reachesor added to a stage before it reaches
the exhaustthe exhaust..

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

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

11. Single-stageSingle-stage
Single stageSingle stage
1.1.One wheel.One wheel.
2.2.Pressure is reduced Pressure is reduced
in one stagein one stage

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

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

14. GovernorsGovernors
The governor valve:The governor valve:
1.1.Regulates the amount of steam AS REQUIRED into the Regulates the amount of steam AS REQUIRED into the
turbine. turbine.
2.2.It is used to control turbine speed.It is used to control turbine speed.
LET US SEE---- LET US SEE----

HOWHOW

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

16. SecondSecond … … Operation of the governor Operation of the governor
valvevalve
1- 1- When the turbine is notWhen the turbine is not
operating, the spring holdsoperating, the spring holds
the fly balls close to thethe fly balls close to the
shaft. Before the turbine isshaft. Before the turbine is
started, the governorstarted, the governor
valve is wide open. valve is wide open.

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

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

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

20. 1.1.At normal speeds the At normal speeds the
trip pin remains inside trip pin remains inside
the shaft by a spring.the shaft by a spring.
2.2.If the turbine over If the turbine over
speeds, the pin is speeds, the pin is
ejected from the shaft ejected from the shaft
by centrifugal force.by centrifugal force.
The drawing shows a trip pin in the shaft.The drawing shows a trip pin in the shaft.

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

22. Main Parts of steam turbineMain Parts of steam turbine
RotorRotor
Steam chestSteam chest
CasingCasing
Over speed trip systemOver speed trip system
Governor systemGovernor system