NIFE ENGINES ALL POSSIBLE QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTION
What is Bernoulli's theorem
Any incompressible fluid that passes through a convergent opening, velocity
increase, pressure decreases
What is Bernoulli's Equation
Pt=Ps+Pk
Which type of air is compressible?
Supersonic air
What happens to Velocity and Pressure in a nozzle
Pressure decreases, velocity increases
What happens to Velocity and Pressure in a diffuser?
Pressure increases, velocity decreases
Draw the tootsie roll method
Left side are diffusers, right side are nozzles
What does an increase in pressure at the inlet do for the engine?
It packs more oxygen tighter together so the engine runs more efficiently
What is the shape of the inlet?
Convergent-divergent
What is the shape of an incompressible air diffuser?
Divergent
What are the events/components of the Otto and the Brayton Cycle?
Intake, Compression, Combustion, Exhaust
Explain what happens at each of the events in the Otto cycle
Intake: Air is entering the valve while the piston is at the bottom
Compression: The pressure is increased as the piston moves up
Combustion: Spark ignites the air and sends the piston down
Exhaust: the valve opens to release the air and start the cycle over
What is the difference between the Otto and Brayton cycle?
All events happen simultaneously in the Brayton cycle, while they happen in order in
the Otto cycle
What three parts does a gas turbine engine have at a minimum? What else can
also be included?
Compressor, Combustion Chamber/Burner, Turbine
Inlet, Compressor, Diffuser, Combustion chamber/burner, Turbine, exhaust
(I cant do complex turbine equations)
What happens to temperature, pressure, and velocity at all 6 different parts of
the gas turbine engine?
What is gross thrust?
Thrust solely from the velocity of the exhaust gases (ignores inlet) at standard day
conditions (29.92 in/Hg and 15C)
What is net thrust and its equation?
Thrust that corrects for the inlet air.
Net Thrust=m*(Vf-Vi)/t
What is the thrust equation?
, T=m*a
Explain what temperature, altitude, pressure, engine RPM, RAM Effect, and
density do to thrust. (TAPERD)
Explain the RAM effect in a gas turbine engine
As the aircraft goes faster, more and more air is being rammed into the inlet. This
increases the mass and pressure of the inlet air causing better engine performance.
What are the cockpit thrust measuring devices?
EPR (Engine Pressure Ratio) gauge, Torquemeter, and Tachometer
What is a EPR?
Engine pressure ratio. It measures the pressure ratio between the inlet and exhaust
airflow
What is a torquemeter and what type of aircraft use it?
Indicated shaft horsepower available to drive the rotor or prop. Aircrafts that have
rotors or props.
What is a Tachometer? What is it measured in?
Gauge used to measure engine performance/ speed. Measured in percent RPM
What is the purpose of an inlet duct? What is it designed to act like (nozzle or
diffuser)?
Provides the proper amount of high pressure, turbulence free air that is steady and
uniform to the first stage of the compressor. Diffuser.
What shape is the inlet of a subsonic aircraft?
Diverging shape
What shape is the inlet of a supersonic aircraft?
Converging-diverging
What is a variable geometry inlet duct and how does it work?
An inlet duct that uses mechanical devices such as ramps, wedges, or cones that
change the shape of the inlet duct as speed goes between subsonic and supersonic.
What is the purpose of a compressor?
To supply enough air to satisfy the requirements of the combustion section.
What makes up one stage of a compressor?
Stator blades and rotor blades
What are the three types of compressors?
Centrifugal, axial, axial-centrifugal
What is the advantage of a centrifugal flow compressor?
Pressure increases at every stage, low cost, rugged, good power output over large
RPM ranges
What does an impeller do and what does it do to velocity and pressure?
Accelerates air outward toward the diffuser. Velocity and pressure are increased.
What does a diffuser do?
Converts high velocity airflow to high pressure
What is the disadvantage for Centrifugal flow compressors?
Large frontal area means increased drag. Impractical for multiple stages.
What does a manifold do?
Routes air to the combustion chamber
What is the biggest advantages for axial flow compressors?
Greatest overall compression ratios, large pressure increase for engine size
What is the disadvantage for axial flow compressors?
Not suitable for supersonic airflow.
What happens to a rotor driven turbine at high RPM?
Increases velocity, pressure, and total pressure.
ANSWERS WITH COMPLETE SOLUTION
What is Bernoulli's theorem
Any incompressible fluid that passes through a convergent opening, velocity
increase, pressure decreases
What is Bernoulli's Equation
Pt=Ps+Pk
Which type of air is compressible?
Supersonic air
What happens to Velocity and Pressure in a nozzle
Pressure decreases, velocity increases
What happens to Velocity and Pressure in a diffuser?
Pressure increases, velocity decreases
Draw the tootsie roll method
Left side are diffusers, right side are nozzles
What does an increase in pressure at the inlet do for the engine?
It packs more oxygen tighter together so the engine runs more efficiently
What is the shape of the inlet?
Convergent-divergent
What is the shape of an incompressible air diffuser?
Divergent
What are the events/components of the Otto and the Brayton Cycle?
Intake, Compression, Combustion, Exhaust
Explain what happens at each of the events in the Otto cycle
Intake: Air is entering the valve while the piston is at the bottom
Compression: The pressure is increased as the piston moves up
Combustion: Spark ignites the air and sends the piston down
Exhaust: the valve opens to release the air and start the cycle over
What is the difference between the Otto and Brayton cycle?
All events happen simultaneously in the Brayton cycle, while they happen in order in
the Otto cycle
What three parts does a gas turbine engine have at a minimum? What else can
also be included?
Compressor, Combustion Chamber/Burner, Turbine
Inlet, Compressor, Diffuser, Combustion chamber/burner, Turbine, exhaust
(I cant do complex turbine equations)
What happens to temperature, pressure, and velocity at all 6 different parts of
the gas turbine engine?
What is gross thrust?
Thrust solely from the velocity of the exhaust gases (ignores inlet) at standard day
conditions (29.92 in/Hg and 15C)
What is net thrust and its equation?
Thrust that corrects for the inlet air.
Net Thrust=m*(Vf-Vi)/t
What is the thrust equation?
, T=m*a
Explain what temperature, altitude, pressure, engine RPM, RAM Effect, and
density do to thrust. (TAPERD)
Explain the RAM effect in a gas turbine engine
As the aircraft goes faster, more and more air is being rammed into the inlet. This
increases the mass and pressure of the inlet air causing better engine performance.
What are the cockpit thrust measuring devices?
EPR (Engine Pressure Ratio) gauge, Torquemeter, and Tachometer
What is a EPR?
Engine pressure ratio. It measures the pressure ratio between the inlet and exhaust
airflow
What is a torquemeter and what type of aircraft use it?
Indicated shaft horsepower available to drive the rotor or prop. Aircrafts that have
rotors or props.
What is a Tachometer? What is it measured in?
Gauge used to measure engine performance/ speed. Measured in percent RPM
What is the purpose of an inlet duct? What is it designed to act like (nozzle or
diffuser)?
Provides the proper amount of high pressure, turbulence free air that is steady and
uniform to the first stage of the compressor. Diffuser.
What shape is the inlet of a subsonic aircraft?
Diverging shape
What shape is the inlet of a supersonic aircraft?
Converging-diverging
What is a variable geometry inlet duct and how does it work?
An inlet duct that uses mechanical devices such as ramps, wedges, or cones that
change the shape of the inlet duct as speed goes between subsonic and supersonic.
What is the purpose of a compressor?
To supply enough air to satisfy the requirements of the combustion section.
What makes up one stage of a compressor?
Stator blades and rotor blades
What are the three types of compressors?
Centrifugal, axial, axial-centrifugal
What is the advantage of a centrifugal flow compressor?
Pressure increases at every stage, low cost, rugged, good power output over large
RPM ranges
What does an impeller do and what does it do to velocity and pressure?
Accelerates air outward toward the diffuser. Velocity and pressure are increased.
What does a diffuser do?
Converts high velocity airflow to high pressure
What is the disadvantage for Centrifugal flow compressors?
Large frontal area means increased drag. Impractical for multiple stages.
What does a manifold do?
Routes air to the combustion chamber
What is the biggest advantages for axial flow compressors?
Greatest overall compression ratios, large pressure increase for engine size
What is the disadvantage for axial flow compressors?
Not suitable for supersonic airflow.
What happens to a rotor driven turbine at high RPM?
Increases velocity, pressure, and total pressure.
