NIFE Engines 3-1-1 Flashcards
Describe a gas generator:
Produces the high-energy airflow necessary for creating thrust. All gas turbine engines at a
minimum will include a compressor, combustion chamber (burner), and a turbine.
Describe engine thrust
Result of many pressure, temperature and velocity changes as airflow passes through an engine.
Describe how airflow properties change through each section of a gas turbine engine:
Inlet: Temperate and Pressure increase, Velocity decrease
Compressor: Relatively constant
Combustion Chamber: Increase in temperate, decrease in pressure, increase in velocity
Turbine: Decrease in temperature, decrease in pressure, increase in velocity
Exhaust: Decrease in temperature, Decrease in Pressure, Increase in Velocity
Describe the behavior of airflow in a diffuser
A diffuser always increases pressure and decreases velocity
Describe the behavior of airflow in a nozzle
A nozzle always increases velocity and decreases pressure
Describe the Brayton Cycle:
An operating cycle that consists of four events occurring simultaneously: intake, compression, combustion, and exhaust. Used in gas turbines.
Describe the cockpit thrust measuring devices
Pressure indication (EPR)
- Pressure ratio between inlet and exhaust airflow.
- Used by turbojets and turbofans.
Torquemeter
- Shaft HP available. Used by propeller or rotors.
Tachometer
- Indication of engine speed by gauging energy produced by engine, shown in percentage of rpm.
Describe the effects of airflow properties on thrust in a gas turbine engine
- Air density: If the density of the airflow increases, air mass entering the turbine will increase, causing thrust to increase
- Air temperature: As temp increases > air molecules move apart > air becomes less dense > Less thrust
- Air pressure: As pressure increases > molecules get closer together > density increases > thrust increases
Describe the Otto Cycle:
Operating cycle where intake, compression, combustion, and exhaust occur sequentially and usually with a piston. Used in reciprocating engines.
EXPLAIN Bernoulli’s Equation, given dynamic pressure, static pressure, and total pressure:
States that as any incompressible fluid (subsonic airflow) passes through a convergent opening its velocity increases and pressure decreases, and vice versa. Supersonic airflow is compressible and behaves opposite to subsonic flow.
Explain RAM effect in a gas turbine engine:
Normally thrust decreases with an increase in airspeed. However, more and more air is being rammed into the inlet as airspeed increases, thus offsetting the decrease in acceleration and resulting in a neutral or increase thrust at subsonic airspeeds.
At supersonic airspeeds, there is a significant increase in overall thrust due to ram effect.
Pressure Indication Gauges:
Tachometer
Torquemeter
EPR
Tachometer
Most commonly used to determine engine performance. Provides the crew with an indication of engine speed as a percentage of full power.
Torquemeter
Propeller or rotor driven aircraft use a torquemeter gauge to indicate power available. Indicates shaft horsepower available to drive the propeller or rotor.
Describe the relationship between pressure and velocity in a closed system.
They have an inverse relationship.
Pressure + Velocity = Total Pressure
