Cold Section ❄️ Flashcards
(24 cards)
What does the cold section consist of
Inlet duct
Compressor
Diffuser
What does the inlet duct do
Slows air to subsonic speed
Converts kinetic to pressure energy
Smoothes air
Divergent shape
Another name for single entrance duct is
Pitot duct
Methods of FOD prevention
shrouded intakes
Vortex separator units
What is the compressor used for
Compresses air for combustion
Cooling other components from its bleed air
Pneumatic components
Cabin and hydraulic system pressurisation
Inlet anti icing
Two types of compressors
Centrifugal
Axial flow
In a turboprop and turbo shaft, both centrifugal and axial flow compressors are often used. In which order are they placed
Axial first then centrifugal (alphabetical order)
What is compression ratio affected by and what does a low compression ratio mean
Compressors type
Number of compressor stages
Means less fuel usage
Axial flow compressor ratio
1.2:1
Centrifugal compression ratio
7:1
Parts of a centrifugal compressor
Impeller
Diffuser
Manifold
One stage of a centrifugal compressor
Impeller - diffuser - manifold combination
In a centrifugal compressors what does an impeller do
Diverges air from the impeller eye via vanes forming divergent passages
What does a diffuser do in a centrifugal compressor
Converts kinetic to pressure energy, also has divergent passages further slowing air and increasing pressure
In a centrifugal compressor what does the manifold do
Straightens the compressed air and sends it to the next compressor stage or combustor
WhTs the most amount of stages you can have in a centrifugal compressor
2
What is a stage in an axial flow compressor
Pairing of a rotor and a stator
What do stators do
Slow and straighten air
What do rotors do in a axial flow compressor
Accelerate air rearwards and increase pressure
Pros cons of centrifugal compressor
PRO
cheap
FOD resistant
High pressure rise per stage
CONS
large frontal area-drag
Only two stages limit
Poor acceleration
Pros cons of axial flow compressors
PRO
small frontal area-less drag
Higher compression ratio due to more stages
Quick acceleration
CON
expensive
FOD vulnerable
What is compressor surge
Occurring at the surge point a Reversal of air and repulsion out the intake (overfilling a water balloon)
Symptoms of compressor surge
Flashes/flame from inlet or exhaust
Vibration
Bangs
Rpm and fuel flow fluctuation
Rising engine temp
Loss of thrust
Yaw towards surged engine
Cause of a surge or stall
A Disruption to the airflow over the compressor rotors
