15.03 - Inlets.

Question 1

Compressor inlet ducts

Answer 1

Supply distortion free air into the compressor.
Steady airflow to prevent compressor stall.
Divergent duct to create more pressure.
Part of the airframe not the engine.
Turboprop and turbo shaft have inlet screens to prevent FOD

Question 2

Divided entrance ducts.

Answer 2

Military a/c.
Turning vanes are sometime used to smooth the airflow around curves and prevent turbulence.
Flight manoeuvres can cause imbalances in ram air pressure between the two ducts.

Question 3

Variable geometry duct

Answer 3

Often used to reduce the speed of the airflow to subsonic using shock waves.
Inlets act as diffusers, decreases velocity and increase static pressure.
Used by supersonic a/c to create a shockwave or two.

Question 4

Compressor inlet screens

Answer 4

Protect from FOD.
Susceptible to icing
Cause a loss in duct pressure.

Question 5

Bellmouth compressor inlets.

Answer 5

Installed on engines undergoing testing in a test cell.
Designed to obtain very high aerodynamic efficiency.
Duct loss is considered to be zero.

Question 6

Turboprop and turbo shaft inlets

Answer 6

Conical spinner prevents ice build up.
Anti iced by electrical heating.

Question 7

Turbofan inlets

Answer 7

Anti-iced by bleed air.
Divergent.

Question 8

Ice protection.

Answer 8

Turboprops use warm oil from the engine for anti-icing.
Conical spinner and warm air used.
Ice disturbs airflow and can cause damage
Ice can form at 5 c in dry air and at 7 c in moist air.
Bleed air from HP compresser is used to heat the spinner and intake lip.

Question 9

Anti ice bleed air regulator valve.

Answer 9

Solenoid controlled.
Manua over-ride, can be locked open or closed.

Question 10

Anti ice electronic engine control.

Answer 10

Controlled by EEC.