Steam Turbines Flashcards
What is the most important characteristic of energy?
it can neither be created nor destroyed; it can only change its form.
What is Stored Energy?
Stored energy is energy that is actually contained in, or stored in, an object
What are the two types of Stored Energy?
Potential Energy and Kinetic Energy
What is Potential Energy?
Potential energy is energy within an object waiting to be released
Stored energy in steam is called what?
ENTHALPY
What is ENTHALPY usually expressed in?
British Thermal Units (BTU)
What is Kinetic Energy?
kinetic energy is energy that has been released
Kinetic energy exists because….
of the relative velocities of two or more objects
Explain “Work”
Work is simply moving an object through a resisting force
What is the unit of measure for work?
Foot-Pound (ft-lb)
Explain “Power”
Power is an amount of work done over a period of time
What is the most common unit of power?
Horsepower
One horsepower is equivalent to how much
ft-lb per second?
550 ft-lb
Explain the Impulse Principle
The pressure of the water stream drops from hose pressure to atmospheric pressure, and the resulting increase in velocity of the stream is equal to the decrease in pressure. A greater pressure differential, therefore, will cause a greater velocity increase.
Explain the impulse turbine
The steam in an impulse turbine (1) passes through stationary nozzles,which (2) converts some of the thermal energy contained in the steam (indicated by its pressure and temperature) into kinetic energy (velocity), and (3) directs the steam flow into the blades of the turbine wheel. The blades and moving wheel (4) then convert the kinetic energy of the steam into mechanical energy in the form of the actual movement of the turbine wheel and shaft or rotor.
Explain reaction turbine
In a reaction turbine, steam passes through a row of FIXED BLADES which act as nozzles and EXPAND the steam (decrease pressure). This increases the steam’s VELOCITY and directs it into the MOVING BLADES, which are almost identical in shape to the fixed blades
What is the purpose of the nozzles in an impulse and reaction turbine?
To convert the stored thermal energy of the steam into kinetic energy or velocity
What acts as nozzles in a reaction turbine?
Fixed and moving blades
What is an IMPULSE turbine STAGE?
one set of nozzles and the succeeding row or rows of either fixed or moving blades.
Fixed blades in an impulse turbine do what?
Redirect the steam flow from one row of moving blades to the next
A simple impulse stage (one set of nozzles and one row of moving blades) is commonly referred to as what?
A RATEAU stage
What is a REACTION turbine STAGE?
one row of fixed blades and a succeeding row of moving blades
What’s the difference between an impulse stage and a reaction stage?
An impulse stage has only one pressure drop, since a pressure drop will occur only in a nozzle; whereas, a reaction stage has two pressure drops
What is COMPOUNDING?
The use of blading and nozzles in a turbine that will cause more than one pressure drop and/or more than one velocity drop as the steam passes through it
