Steam Turbines Flashcards
What is the primary function of a steam turbine in naval ships?
To convert thermal energy of steam into mechanical work for propulsion (main engine) or electrical generation (ship service turbine generator).
Explain the two-step energy conversion process in steam turbines.
Step 1: Thermal energy to kinetic energy (KE) via nozzles.
Step 2: Kinetic energy to mechanical work via turbine blading.
Describe the purpose of a converging-diverging nozzle.
To control the expansion and reduce turbulence by gradually increasing the cross-sectional area beyond the throat.
What are the components of a nozzle in a steam turbine?
Throat (inlet) and mouth (outlet).
What happens to the velocity and kinetic energy of steam as it passes through a nozzle?
The pressure drops, velocity increases, and kinetic energy increases.
Differentiate between impulse and reaction blades.
Impulse blades: Steam hits the blade directly at high velocity, pushing it.
Reaction blades: Steam increases velocity through fixed vanes, then blades move by reaction force.
How does steam move a blade in an impulse turbine?
Steam hits the blade at high velocity and moves it by a direct push, exiting at low velocity.
How does steam move a blade in a reaction turbine?
team passes through fixed vanes, increasing its velocity and then pushes the moving blades by reaction force.
What is a turbine stage?
A set of nozzles and blades.
Describe the difference between an impulse stage and a reaction stage.
Impulse stage (Rateau stage): One set of nozzles and moving impulse blades with one pressure drop.
Reaction stage (Parsons stage): One set of fixed vanes and moving nozzle-shaped blades with two pressure drops.
Explain the concept of velocity compounding in turbines.
Using multiple stages with one pressure drop and multiple velocity drops to maximize energy extraction.
What is pressure compounding in impulse turbines?
Using multiple impulse/Rateau stages to increase efficiency with multiple pressure drops.
Describe the characteristics of an axial flow turbine.
Steam flows parallel to the turbine shaft axis, commonly used in propulsion.
What is the main advantage of a double flow turbine?
It allows the turbine size to be reduced and cancels axial thrust by splitting steam flow in two directions.
List the main components of a steam turbine.
Casing, rotor, bearings, throttles, shaft glands, gland seal/exhaust.
