Steam turbines work by converting the energy of expanding steam into rotational motion. They have several key components and come in two main types: impulse and reaction. Impulse turbines use nozzles to direct high velocity steam onto turbine blades for impulse, while reaction turbines utilize both fixed and moving blades to expand steam. Common problems in steam turbines include stress corrosion cracking, corrosion fatigue, thermal fatigue, and pitting due to chemical attack from corrosive elements in the steam. Proper lubrication and preventing blade deterioration are important for optimizing steam turbine performance and lifespan.

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
Advantages:
-Simple configuration
-Low capital cost
Boiler Turbine -Low need of cooling water
-High total efficiency
Fuel
Disadvantages:
Condensate LP
Process Steam
-Larger steam turbine
Figure: Back pressure steam turbine
6

7. Steam turbine:
Extraction Condensing Steam
Turbine HP Steam
• Steam obtained by
extraction from an Boiler Turbine
intermediate stage Fuel
• Remaining steam is Condensate
LP Steam
Process
exhausted
• Relatively high
capital cost, lower Condenser
total efficiency
Figure: Extraction condensing steam turbine
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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 9 – rotor disc 21 – bearing pedestal
2 – inlet control valve 10 – rotor 22 – safety governor
3 – nozzle chamber 11 – journal bearing 23 – main oil pump
4 – nozzle-box 13 – thrust bearing 24 – centrifugal governor
5 – outlet 14 – generator rotor 25 – turning gear
6 – stator 15 – coupling 29 – control stage impulse blading
7 – blade carrier 16 – labyrinth packing
8 – casing 19 – steam bleeding (extraction)

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.

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