15.2 COMPRESSOR INLET DUCTS👌🏼 Flashcards
What are Inlet guide vanes (IGV) used for?
- straighten airflow and direct it to first stages of the compressor
The air-inlet duct is considered what part
- airframe part
What do turboprop/turboshaft engines have to prevent FOD
- screens to cover inlet
Simply explain where the air is taken from in a divided-entrance duct
- takes air from either side of fuselage
What is sometimes placed in the side scoop inlet to assist in straightening the incoming airflow and prevent turbulence in a divided entrance duct
Series of turning vanes
When a aircraft duct length is shortened in a divided entrance duct what is the disadvantages
Sudden flight manoeuvres cause imbalance in ram air pressure between the 2 ducts
Explain inlet ducts (which function as diffusers) in terms of velocity and pressure
- decreasing velocity and increasing static pressure of air passing through
Airflow through the engine must always be less than
Mach 1 (supersonic)
What 3 methods diffuse the inlet air and slow the inlet airflow at supersonic speeds
- Vary area, or geometry, moveable restriction such as a ramp/wedge inside the duct
- variable airflow bypass arrangement
- use of a shockwave
Explain compressor inlet screens
- prevent engine from ingesting FOD
- screens cause a loss in inlet duct pressure
- susceptible to icing
Explain Bellmouth compressor inlets
- installed on engine undergoing testing
- for very high aerodynamic efficiency
- duct loss is considered 0
What are inlets of turboprops anti-iced by
- electrical elements (lip opening of intake)
What are deflector doors used for
- deflect ice or dirt away from intake
Explain conical spinner
- does not allow ice build up on surface
What does the fan prevent
- damage from ingested foreign material
Explain inlet lip anti-icing
- warm bleed air circulated
What effect does ice have on the engine inlet
- disturbed air flow that reduces performance of engine leading to compressor stall
- engine sucks in ice pieces
How do turboprops provide anti-icing
- uses warm oil from engine oil reservoir to provide anti-icing
Ice can form in the inlet in dry air at what temp
5*c
Ice can form in the inlet in moist conditions at what temperature
- 7*c
Explain anti-icing with electronic engine control
- once anti-icing is turned on.
- EEC controls the flow of hot air
Do all thermal anti-ice valves have a manual override function
- yes
What engines have electric heat strip systems
Smaller turboprop and turboshaft
What should you ensure when using electric heat strip systems
Operate only when engine is running
What is the main function of an inlet duct
Provide correct amount of airflow to engine inlet
What are inlet ducts designed to function as
Diffusers
For very high speed aircraft, inside area configuration of duct is changed by a mechanical device as the speed of the aircraft increases or decreases. What is this type of duct known as ?
‘Variable geometry’ inlet duct
