15.3 Inlet Flashcards
(33 cards)
What do engines use to straighten airflow in to the compressor inlet?
Inlet/ inlet guide vanes
What kind of part is the air inlet duct?
Airframe part not a part of the engine
What type of engines consume more airflow and so what is more critical?
Gas turbine engines
Air entrance passage is more critical especially at high speeds
What aircraft usually have screens to cover the inlet for prevention of FOD?
turboprop and turboshaft engines
How is pressure recovered when thrust decreases as the aircraft speed increases?
- ram recovery
- the inlet compresses free airstream molecules to recover pressure
What is air pressure drop in the engine inlet caused by?
- friction of air along both sides of the duct
- by bends in the duct system
What’s accomplished by turning the airflow on engines with low flow rates?
Engine nacelle can be smaller
Less drag
What must the duct in turbofan engines have?
Straight section for smooth airflow during high airflows
How is the configuration of the entrance duct decided?
- location of the engine on the aircraft
- airspeed, altitude and attitude It’s designed to operate at
What are the two types of divided duct?
Wing- root inlet or a scoop at either side
Which engine has a bigger entrance passage, GTE or reciprocating engines?
GTE
What does smooth airflow in an inlet duct depend on?
Keeping the turbulence to a minimum as the air enters the duct
What must the duct have on turbofan engines for smooth airflow?
A sufficiently straight section
What’s the main function of an inlet duct?
Provide the correct amount of air to the engine inlet
What’s the maximum airflow requirements on aircraft using a turbojet or low bypass turbofan engine?
Mach number of airflow directly ahead of the face of the engine is less than Mach 1
Airflow through the engine must be less than Mach 1
How is the velocity of airflow decreased as it enters the air inlet duct?
Inlet ducts are designed to act as diffusers
What’s a variable geometry inlet duct?
When the inside area of the duct is changed by a mechanical device as the speed of the aircraft increases or decreases
What are the three methods to slow inlet airflow at supersonic speeds?
1) moveable restriction such as a ramp or wedge inside the duct
2) variable airflow bypass arrangement, extracts part of the inlet airflow from the duct ahead of the engine
3) shockwave
What is the thrust stand on a bell mouth compressor made up from?
One moving and one non moving component
The moving component can push against a load cell and measure thrust during the testing of the engine
What’s the duct loss for Bellmouth compressor inlets?
Zero
How is the inlet for turboprops usually anti iced?
Electrical elements in the lip opening of the intake
What provides anti icing on the inlet on a turbofan?
Warm bleed air is drawn from the engine and circulated on the inside of the inlet
The fan hub is heated by warm air
When can ice form in the inlet?
5 C in dry air
7 C in moist air
How do high mass airflow engines anti ice?
Bleed air from HP compressor
Through the anti ice valves
To inlet guide vanes, the spinner and the lip
