Engines 1: Principles of Gas Turbine/Reciprocating Engines Flashcards
What is the relationship between pressure and velocity in a closed system?
They have an inverse relationship and together they make up total pressure
Pressure = static pressure
Velocity = dynamic pressure
What happens to subsonic airflow as it goes through a convergent opening?
Pressure decreases
Velocity increases
What happens to subsonic airflow as it goes through a divergent opening?
Pressure increases
Velocity decreases
What happens to supersonic airflow as it goes through a convergent opening?
Pressure increases
Velocity decreases
What happens to supersonic airflow as it goes through a divergent opening?
Pressure decreases
Velocity increases
What does a nozzle do? (Relating to pressure and velocity)
A nozzle increases velocity
What does a diffuser do? (Relating to pressure and velocity)
A diffuser increases pressure
What are the three sections of a gas turbine engine?
Compressor
Combustion chamber/burner
Turbine
What cycle is used in a gas turbine engine?
The Brayton cycle
What cycle is used in a reciprocating engine?
The Otto cycle
What are the steps to the Otto cycle?
Intake
Compression
Combustion
Exhaust
What are the differences between the Brayton and the Otto cycle?
The Otto cycle happens sequentially and in a single piston whereas the Brayton cycle happens all at the same time in a single gas turbine engine/
Gross thrust
Thrust measured at exhaust at standard day conditions (29.92in-hg and 15 °C)
Only produced by stationary engines
Net thrust
Thrust measured under normal flight conditions
Accounts for inlet airflow velocity
What are the factors that affect thrust?
Temperature
Altitude
Pressure
Engine RPMs
Ram Effect
What is the relationship between thrust and air temperature?
Inversely related; as air temperature increases, thrust decreases
As it gets warmer, air molecules tend to move apart
What is the relationship between thrust and air pressure?
Directly related; as air pressure increases, thrust increases
Higher air pressure means that air molecules tend to move closer together
What is the relationship between thrust and altitude?
Inverse Relationship; thrust decreases as altitude increases
The thrust decrease (from the pressure decrease) outweighs the thrust increase (from the temperature decrease) as altitude increases
What is the optimal cruise level?
36,000 ft
How does ram effect change thrust at subsonic speeds?
At subsonic speeds, an increase in airspeed leads to a small increase in thrust
How does ram effect change thrust at supersonic speeds?
At supersonic speeds, an increase in airspeed leads to a significant increase in thrust
What is the relationship between engine RPMs and thrust?
Directly related; as engine RPMs increase, thrust increases
Engine Pressure Ratio
Indicates the pressure ratio between the inlet and exhaust airflow
Torquemeter
Indicates amount of power available
Shows shaft horsepower available to drive a propeller
Tachometer
Indicates engine performance
Shows amount of energy produced by engine in %RPMs
What is the relationship between thrust and RAM effect?
Direct relationship; as Ram Effect increases, thrust increases
