15.4 COMPRESSORS Flashcards
what are the 2 main components of a compressor
rotor, stator
what are the 2 functions of the compressor
supply air to combustion chamber, supply bleed air
whats the combination of a rotor and stator called
compressor stage
whats the first part of the compressor stage
rotor
if there are stator vanes infront of a compressor stage what are they called
inlet guide vanes
what are the stator vanes in the fan duct called
outlet guide vanes
what do outlet guide vanes do
improve airflow into fan nozzle
what are the 2 compressors currently used in turbine engines
centrifugal flow compressor, axial flow compressor
what is the pressure rise ratio in centrifugal compressors
8:1
what does a centrifugal compressor consist of
impellar, diffuser
where are axial flow compressors usually found
turbofans
explain the axial flow compressors airflow
original direction but just compressed
whats an advantage of centrifugal compressors
can work at higher rotational speeds
what is a stage
rotor, stator pair
on fan blades what 3 parameters affect the centrifugal forces
rotor speed, blade mass, distance of blade from centre of rotation
on blades what numbers are written on them
part number, serial number, moment weight
what is the moment weight the product of
blade mass, and distance from centre of gravity
how do you replace a fan blade
with another blade which weight is as close to the old one as possible
what one thing axial and centrifugal flow have in common
they are very sensitive to airflow changes
the airflow into the rotor is smooth as long as
the angle of attack to the rotor blades is small
if you increase rotor speed does angle of attack get bigger or smaller
bigger
how does compressor stall occur
angle of attack increases while inlet air velocity decreases
what is compressor surge
severe form of compressor stall
what happens to airflow in compressor surge
reverses
where can compressor surge occur
fwd or aft compressor stages
what are some reasons for compressor stall or surge
dents, damaged parts, dirty blades, broken combustor components
operational reasons for stall or surge
engine speed far below design speed, incorrect acceleration/deceleration
what are methods to avoid stall and surge
compressor bleed valves, dual or triple spools, compressor stator vanes
explain bleed valves in preventing stall or surge
open at low engine speed so excess air can leave
explain variable inlet vanes in preventing stall or surge
optimum angle of attack for every engine speed
what is the rough engine compressor ratio
1.3:1
does the compressor pressure increase or decrease through each stage
increase slightly
why are many stages needed in the compressor
to raise the pressure ready for efficient combustion
an annular combustion chamber has design for small engines and APUs, whats this called
reverse flow combustion
where and how many igniter plugs are on an engine
lower half, 2
what does the dome do
connects inner and outer liner
