1. Steam Turbines
Expansion Phase

2. References Required Recommended
Introduction to Naval Engineering (Ch. 8)
Recommended
Principles of Naval Engineering (pp )

3. Objectives
A. Comprehend the basic design of steam turbines. B. Comprehend the energy conversions present in steam turbines and represent those conversions on a pressure velocity diagram. C. Know the various uses of steam turbines used onboard ships.

4. Introduction Turbines are energy conversion devices Turbines used for:
Propulsion
Electricity generation
Prime mover for various pumps
MSW Pumps
MFP
Fire pumps
Lube Oil Pumps

5. Turbine Components Casing - containment vessel
Nozzle(s)- energy conversion devices that converts the thermal energy of the steam to kinetic energy
Blades- energy conversion devices that convert kinetic energy to rotational mechanical energy
Rotor- supports the blades and transfers rotational mechanical energy out of the turbine

6. Nozzles Definition: mechanical device which:
uses a reduction in surface area to convert thermal energy to kinetic energy (enthalpy to kinetic energy)
directs fluid flow onto turbine blading
Components: inlet, throat (smallest diameter), and mouth (outlet)

7. Nozzles As Pressure drops velocity KE(=mv2/2) Types:
Converging-Diverging
Converging

8. Blades
Steam exiting nozzles hits blades on rotor and pushes them through a distance
KE Work
Two types of blades:
Impulse
Reaction

9. Blades Impulse Reaction
Steam hits high velocity, moves blade by a “direct push” and exits at low velocity
Reaction
“Fixed vane” nozzles increase velocity, and “moving vane” blades move by a reaction force or “kickback”

10. Blades Reaction Turbines are moved by three main forces:
Reactive force produced on the moving blades as the steam expands between the blades.
Reactive force produced on the moving blades when the steam changes direction.
Push or impulse of the steam impinging on the blading.

11. Classification of Turbines
Staging (groups of blades)
Compounding (groups of stages)
Direction of Steam Flow
Division of Steam Flow

12. Staging Rateau Stage One set of nozzles and moving impulse blades
Only one pressure drop V P

13. Staging
Curtis Stage
1 nozzle, 2 sets of moving blades, one set of fixed blades
Two velocity drops V P

14. Staging Reaction Stage (called Parsons stage)
One set of fixed vane nozzles and moving nozzle-shaped blades
Two pressure drops

15. Compounding
Building turbine with multiple stages to extract maximum energy
Velocity Compounding
Only one pressure drop with multiple velocity drops using multiple stages
Pressure Compounding
Multiple pressure drops using multiple stages

16. Compounding - Impulse Turbines
Velocity-Compounded Impulse Turbine
One nozzle, row of moving blades, row of fixed blades, & second row of moving blades (called Curtis stage)
Adv: Good if initial high pressure

17. Compounding - Impulse Turbines
Pressure-Compounded Impulse Turbine
Two or more impulse/Rateau stages
Adv: increases efficiency by using lower pressures

18. Compounding - Impulse Turbines
Velocity-Pressure Compounded Impulse Turbine
One Curtis stage followed by single or series of Rateau stages
Common for many propulsion turbines (allows for lower blade speed)

19. Compounding - Reaction Turbines
Pressure-Compounded Reaction Turbine
Called Parsons turbine because uses Parsons stages
Adv: efficient at low pressure/low velocity
Disadv: long stage and impractical
Used in some auxiliary applications

20. USS Narwhal (SSN-671)

21. Direction of Steam Flow
Axial Flow
Steam flow parallel to turbine shaft axis (used a lot, particularly for propulsion)
Radial Flow
Steam flow perpendicular to turbine shaft axis (used some for auxiliary turbines)

22. Division of Steam Flow Single Flow Double Flow
Steam enters at inlet and flows in one direction to the exhaust
Double Flow
Steam flow split & flows in two directions
Allows turbine size to be reduced
Axial thrust on shaft avoided (axial flows cancel)

23. Turbine Components

24. Questions?