15.04 Flashcards
What material is the fan rotor disc made from
Titanium alloy
Which type of compressor axial or centrifugal is more efficient
Axial
Where would you most likely find a centrifugal flow compressor
Small gas turbine engine e.g APU
Why does a cone have a spiral or white markings
To scare birds away
Which type of compressor axial or centrifugal has a good efficiency over a wide speed range
Centrifugal
What is the first part of a compressor stage
The rotor
What unit can the moment weigh of a blade be given in
Gram/inches
cmg
Oz inches
What type of fan blade attachment is used on most engines
Dovetail fitting
What makes up the compressor stage
Rotor & stator
What two ways can you compress air in engines
Decrease the volume by a piston
Make use of Bernoulli Principal
What happens when the impeller rotates
Air is sucked horizontally near the centre of the impeller
What is the spinner cone also known as
Compressor inlet cone or nose cone
What is the forward part and aft part of a dual spool engine called
LP compressor N1 and HP compressor N2
When can a compressor stall
Speed of engine is too far BELOW the design speed
What pressure ratio can the centrifugal flow compressor give
About 5:1
What is the rear drum of a rotor assembly bolted to
Rear hub
What is the advantage of wide chord fan blade than to conventional blades
More efficient
How are the stator vanes installed on a split stator case
Two stator halves bolted together afterward
What axis does airflow in an axial flow compressor flow along
Horizontal axis
Can fan blades be manufactured to have the same moment weights
NO!!
What would you do if one blade is damage
Change the pair instead of one blade
What is the fan blade containment made of
Honeycomb construction covered by Kevlar
How are the stator vanes fitted on a closed stator case
Fitted to the shrouds between the rotor stages
Which compressor axial or centrifugal has a very high pressure rise per stage
Centrifugal
Which compressor axial or centrifugal is cheaper to manufacture
Centrifugal
Which compressor axial or centrifugal needs less power for engine start and weight less
Centrifugal
How many compressor stages does a modern engine have
9 up to 14
What is the best method to change the engine fan blade
Replace the fan blade with a new blade with the moment weight as close to the old blade
What are the main components of a centrifugal flame w compressor
Diffuser
Impeller
Compressor manifold
What is another name for a low pressure compressor rotor
Booster rotor
What is the pressure ratio of each stage of an axial flow compressor
1:3:1
How many stages of pressure increase can you have in a centrifugal flow compressor
2 As pressure decrease when airflow goes from first stage to second stage
What two main components does a compressor have
Compressor rotor
Compressor stator
What is a double faced compressor
Two impeller mounted face to face
If the moment is larger than specific by manufacturer what can be used
Balance weights
How can you identify fan blade one
Index mark or offset hole
How is the labyrinth seal made
By knife edges on the rotor drum and the opposing shrouds of the stator assembly
How can you get a smooth airflow on an axial compressor
Make sure angle of attack on rotor blade is small
What do the compressor inlet/outlet cases support
Give support for the compressor rotor bearings
Which compressor axial or centrifugal causes less drag on engines
Axial as it has a smaller frontal area
What do the OGV improve
The airflow into the fan nozzle
What are the three methods used to prevent compressor stall and surge
- Use compressor bleed valve
- Use dual or triple spool rotors instead of single
- Use variable compressor stator vanes (most modern)
What are the two types of compressor
The axial flow compressor
The centrifugal flow compressor
Compressor with high compression ratios will have what
VSV In the first stages
What are the bells held in place by
Blade retainers
What do IGV improve
The airflow into the first compressor stage
Where is bleed air supplied through in a compressor
Supplied through hollow stator vanes or through holes in the outer platform of the stator vane
What does a labyrinth seal do
Prevents reverse air flow
What is a severe form of compressor stall
Compressor surge
What happens when the air passes through the diffuser
Velocity decreases and pressure increases
What three ways can you fit blades onto a HP compressor
Blade retainers
Locking lug
Bolts
