Lecture 20 Flashcards
What is thrust measured in?*
Pounds (lbs.)
What three things is thrust determined by?*
Change in momentum experienced by air flowing through the engine
The momentum of the fuel
The force caused by the difference in pressure across the exhaust nozzle multiplied by the area of the nozzle
What are the two types of thrust?*
Net thrust
Gross thrust
What is net thrust?*
Thrust produced by the engine while in flight
What is gross thrust?*
Thrust produced by the engine while engine is static and not moving
Only found on an engine test stand
In a turbofan engine, how do you calculate thrust?*
Which part creates the most thrust?*
Total thrust = core engine thrust + fan thrust
The fan creates the most thrust
The core is only responsible for 20-30%
How do we measure thrust on a small turbine engine?*
Compressor speed in % RPM
(full open is 100% RPM)
RPM is proportional to the thrust being produced
How do we measure thrust on a large turbine engine?*
Engine Pressure Ratio (EPR)
What is EPR?*
The difference between the inlet pressure and the exhaust pressure
What is a duct heater?
Similar to an afterburner
Fuel is added to the fan-discharge air and burned
Increases thrust*
How do afterburners increase thrust?*
Fuel is sprayed into the hot exhaust gases and spontaneously ignite
Additional heat further accelerates the air to create 50% increase in thrust
Threefold increase in fuel consumption
