15.3 Inlet Flashcards
What is the primary function of engine inlet ducts in turbine engines?
To provide a relatively distortion-free airflow to the inlet of the compressor in the required quantity.
What are Inlet Guide Vanes (IGV) used for in turbine engines?
To straighten the airflow and direct it into the first stages of the compressor.
Why is a uniform and steady airflow important in turbine engines?
To avoid compressor stall and excessive internal engine temperatures in the turbine section.
Is the air-inlet duct considered a part of the engine?
No, it is considered an airframe part.
What effect do inlet duct inefficiencies have on engine performance?
They can result in performance losses through other components of the engine.
How does the airflow requirement differ between gas turbine engines and reciprocating engines?
Gas turbine engines consume considerably more airflow than reciprocating engines.
What is the significance of air intake size on the Rolls Royce XWB engine?
It is critical in determining engine and aircraft performance, especially at high airspeeds.
What is the purpose of screens on turboprop and turboshaft engines’ inlets?
To prevent Foreign Object Damage (FOD).
What phenomenon compensates for thrust losses as aircraft speed increases?
Ram recovery.
Fill in the blank: The inlet must recover as much of the total pressure of the free airstream as possible, which is known as _______.
ram recovery
What must the engine inlet duct do to minimize drag effect on the aircraft?
Keep the drag effect on the aircraft to a minimum.
What causes an air pressure drop in the engine inlet?
Friction of air along both sides of the duct and bends in the duct system.
How does airflow management affect the size of the engine nacelle in low flow rate engines?
Turning the airflow allows the nacelle to be smaller and have less drag.
What is required in the duct of turbofan engines to ensure smooth airflow?
A sufficiently straight section.
What factors dictate the choice of configuration for the entrance of the duct?
Location of the engine, airspeed, altitude, and attitude at which the aircraft is designed to operate.
What are the different types of inlets discussed?
Divided-entrance duct, variable-geometry duct, compressor inlet screens, bellmouth compressor inlets, turboprop and turboshaft compressor inlets, turbofan engine inlet sections.
What is a divided-entrance duct?
A duct that takes air from either side of the fuselage, widely used in high-speed military aircraft.
What are the main problems faced by a divided duct?
Difficulty in obtaining sufficient air scoop area without causing large amounts of drag and designing an entrance duct of reasonable length with minimal bends.
What is one major drawback of a divided-entrance duct?
Imbalance in ram air pressure between the two ducts during sudden flight maneuvers.
True or False: The airflow through an engine must always be less than Mach 1.
True.
What is the function of a variable-geometry duct?
To provide the correct amount of air to the engine inlet, adjusting for different flight speeds.
Fill in the blank: The aft section of a supersonic inlet duct ________ in area.
increases
What are the three methods to diffuse inlet air at supersonic speeds?
- Vary the area of the inlet duct
- Use a variable airflow bypass arrangement
- Utilize a shock wave in the airstream
What is the purpose of a compressor inlet screen?
To prevent the engine from ingesting items that can cause internal damage.
