1. Analysis of Large Turbines
P M V Subbarao
Professor
Mechanical Engineering Department
Generalization of Sir Parsons Concept……

2. Parsons Steam Turbines : Multistage Reaction Turbines

3. General Rules for Design of Large Impulse-Reaction turbine
The shape of the blade must be viable .
The height of blade must vary at a uniform rate, thus contributing to more economic designs.
As a result of enthalpy drop occurring in the moving blades, there is a considerable amount of pressure is exerted on the rotor.
This is transmitted to thrust bearing.
To void large axial thrust it is usual to allow:
Low degree of reaction in high pressure stages.
In large steam turbines (>300 MW), it is now usual to allow 60 – 70% of degree of reaction in low pressure stages.

4. Generalization of Degree of ReactionU
Vr1
Va1
Vr2
Va2 b1 a1 a2 b2
The reaction effect is an addition to impulse effect.
Define the degree of reaction p va vr
A Physical Linkage between Momentum and Energy transactions

5. First Law Analysis of Reversible Reaction Stage
First law for fixed blades:
First law for relative flow through moving blades: 2 1

6. DoR of Reversible General Reaction Blading
True Power lost by steam in a stage = Power gained by rotor blade 2 1

7. Relative Acceleration of Steam

8. Capacity of A General Reaction Stage
The driving force on wheel
Power Output of the blade :
Diagram Efficiency or Blade efficiency:

11. Stage Sizing
Steam Path

12. Linearization of Reaction Stage Equations

13. Blade velcoity factor, f

14. For a given shape of the blade, the efficiency is a strong function of U/Vfitc.
For maximum efficiency:

15. Performance of Degree of Reaction
Specific Power output

17. Selection of Degree of Reaction
hstage
L increasing L1 L2 L3 L4
An Isentropic Analysis only !!!
Still All the Steam Power Cannot be Converted into Mechanical Power ?

18. Stage Sizing
Steam Path

19. Large Power Plants : Selection of Speed
Swallowing Capacity :
Loading Capacity :
Power Capacity :

20. Mechanical Arrangements of Steam Turbines
Solutions to Turbo-machinery Issues.
Tandem Reheat Steam Turbine
Cross Compound Steam Turbine

21. Tandem Reheat Steam Turbine

22. Cross Compound Reheat Steam Turbine

23. Tandem-compound four-flow steam turbine

24. Large-Capacity Steam Turbines for Fossil Thermal Power Plant