15.3 Inlet Flashcards
What do engines use to straighten the airflow and direct it into the first stages of the compressor?
Inlet guide vanes
What airflow is required to avoid compressor stall?
A uniform and steady airflow
What happens at convergent ducts?
Velocity increases, pressure decreases and temperature decreases
What happens at divergent ducts?
Velocity decreases, pressure increases, temperature increases
Which engine consumes more airflow?
Gas turbine consumes more air than a reciprocating engine
What can inefficiencies of the inlet duct result in?
Performance losses through other components of the engine
Where are divided entrance ducts found?
High speed single or twin military aircraft
Why can’t you use a single entrance duct on military aircraft?
Pilot sits low in the fuselage and close to the nose
What can the divided duct inlet be?
Either a wing root inlet or scoop inlet
Why are the side scoops usually placed as far forward as possible?
To permit a gradual bend towards the compressor inlet
What’s a disadvantage of divided entrance duct?
Some sudden flight manoeuvres can cause an imbalance in ram air pressure
What is the main function of an inlet duct?
To provide the correct amount of air to the engine inlet
Turbojet or low bypass turbofan, what is the max airflow requirements such as Mach number?
Less then Mach 1
In all flight conditions airflow as it enters air inlet must be reduced through the duct before the airflow enters the compressor, how do you achieve this?
Inlet ducts are designed to function as diffusers, decreasing velocity, increasing static pressure
What are the three ways to diffuse the inlet air and slow air down?
1: is to vary the area, or geometry, of the inlet duct either by introducing a movable restriction, such as a ramp or wedge, inside the duct
2: use a variable airflow bypass arrangement, which extracts part of the inlet airflow from the duct ahead of the engine.
3: is the use of a shock wave in the airstream. A shock wave is a thin region of discontinuity in a flow of air or gas, during which the speed, pressure, density, and temperature of the air or gas undergo a sudden change
What are compressor inlet screens used for?
To prevent engine from readily ingesting any items that can be drawn in the intake
Are inlet screens susceptible to icing?
Yes
Do inlet screens cause a loss in inlet duct pressure?
Yes