1. Steam turbine

2. summary
 What is the turbine?
 What is the principle of steam
turbine?
 Types of steam turbine.
 Component of steam turbine.
 Problems in steam turbine.

3. What exactly is the turbine?
Turbine is an engine
that converts energy of
fluid into mechanical
energy
The steam turbine is
steam driven rotary
engine.

4. Principle of steam turbine:
The steam energy is converted mechanical work
by expansion through the turbine.
 Expansion takes place through a series of fixed
blades(nozzles) and moving blades.
 In each row fixed blade and moving blade are
called stage.


5. Steam turbine:
Steam Turbine System:
•
Widely used in CHP(combined heat and power)
applications.
•
Oldest prime mover technology
•
Capacities: 50 kW to hundreds of MWs
•
Thermodynamic cycle is the “Rankin cycle” that uses a
boiler
•
Most common types
• Back pressure steam turbine
• Extraction condensing steam turbine
5

6. Steam turbine:
Back Pressure Steam Turbine
•
Steam exits the turbine at a higher pressure that the
atmospheric
HP Steam
Boiler
Advantages:
-Simple configuration
-Low capital cost
-Low need of cooling water
-High total efficiency
Turbine
Fuel
Condensate
Process
LP
Steam
Disadvantages:
-Larger steam turbine
Figure: Back pressure steam turbine
6

7. Steam turbine:
Extraction Condensing Steam
Turbine
HP Steam
• Steam obtained by
extraction from an
intermediate stage
• Remaining steam is
exhausted
• Relatively high
capital cost, lower
total efficiency
Boiler
Turbine
Fuel
LP Steam
Condensate
Process
Condenser
Figure: Extraction condensing steam turbine
7

8. steam turbine and blades

9. Types of steam turbine:
There are two main types
1. Impulse steam turbine
2. Reaction steam turbine


10. Impulse steam turbine:
The basic idea of an impulse turbine is that
a jet of steam from a fixed nozzle pushes
against the rotor blades and impels them
forward.
 The velocity of steam is twice as fast as the
velocity of blade.
 Pressure drops take place in the fixed blade
(nozzle).


11. The single stage impulse turbine:
The turbine consists of a single rotor to
which impulse blades are attached.
 The steam is fed through one or several
convergent nozzles.
 If high velocity of steam is allowed to flow
through one row of moving blades.
 It produces a rotor speed of about 30000
rpm which is too high for practical use.


12. Velocity diagram:

13. Cross section view:

14. Component of impulse steam turbine:
 Main components are
1. Casing
2. Rotor
3. Blades
4. Stop and control valve
5. Oil befell, steam befell
6. governor
7. Bearing(general and thrust bearing)
8. Gear box(epicyclic gear box)
9. Oil pumps

15. Construction of steam turbines
1 – steam pipeline
2 – inlet control valve
3 – nozzle chamber
4 – nozzle-box
5 – outlet
6 – stator
7 – blade carrier
8 – casing
9 – rotor disc
10 – rotor
11 – journal bearing
13 – thrust bearing
14 – generator rotor
15 – coupling
16 – labyrinth packing
19 – steam bleeding (extraction)
21 – bearing pedestal
22 – safety governor
23 – main oil pump
24 – centrifugal governor
25 – turning gear
29 – control stage impulse blading

16. Reaction steam turbine:
A reaction turbine utilizes a jet of
steam that flows from a nozzle on the
rotor.
 Actually, the steam is directed into the
moving blades by fixed blades
designed to expand the steam.
 The result is a small increase in
velocity over that of the moving
blades.


17. Schematic diagram:

18. Problems in steam turbine:
Stress corrosion carking
 Corrosion fatigue
 Pitting
 Oil lubrication
 imbalance of the rotor can lead to
vibration
 misalignment
 Thermal fatigue


19. BLADE FAILURES:
Unknown 26%
 Stress-Corrosion Cracking 22%
 High-Cycle Fatigue 20%
 Corrosion-Fatigue Cracking 7%
 Temperature Creep Rupture 6%
 Low-Cycle Fatigue 5%
 Corrosion 4%
 Other causes 10%


20. Corrosion:
Resultant damage:
 Extensive pitting of
airfoils, shrouds, covers, blade root
surfaces.
 Causes of failure:
 Chemical attack from corrosive
elements in the steam provided to the
turbine.


21. Creep:
Resultant damage:
 Airfoils, shrouds, covers permanently
deformed.
 Causes of failure:
 Deformed parts subjected to steam
temperatures in excess of design
limits.


22. Fatigue:
Resultant damage:
 Cracks in airfoils, shrouds, covers,
blade roots.
 Causes of failure:
 Loosing of parts (cover, tie wire, etc.)
 Exceeded part fatigue life design limit


23. Stress Corrosion Cracking:
Resultant damage:
 Cracks in highly stressed areas of the
blading.
 Causes of failure:
 caused by the combined presence of
corrosive elements and high stresses
in highly loaded locations.


25. Thank you