15.4 compressor Flashcards
what is the primary function of the compressor
to supply a sufficient quantity of air to satisfy the requirements of the combustion chamber
what are the two main components of the compressor
compressor rotor
compressor stator
what is mounted in each rotor
rotor blades
what component of the compressor is stationary
the stator
what component is always the first part of the compressor stage
the rotor
what are inlet guide vanes
a set of stator vanes in front of a compressor stage
what are the stator vanes in the fan duct usually called
outlet guide vanes
what are the two types of compressors being currently used
centrifugal flow compressor
axial flow compressor
what does the centrifugal-flow compressor consist of
an impeller, a diffuser, and a compressor manifold
how many stage are there in a centrifugal-flow compressor
only 2 stages
what is the function of the impeller
to pick up and accelerate the air outwardly to the diffuser
where are axial flow compressors normally found
on turbofan engines
where are centrifugal flow compressors usually found
on turboshaft and turboprop
what does a single-spool axial flow compressor consist of
a single drum and multiple stators
in an axial flow compressor how is the total number of stages determined
it is based on the desired pressure increase
what are the three parameters that the centrifugal forces depend on
- rotor speed
- blade mass
- the distance of the centre of gravity of the blade from the rotational axis
where can the blade moment weight usually be seen
on the blade root
why is the moment weight sometimes crossed out and another number is shown
the moment weight has changed because of blending
what are the two methods proposed to change a single fan blade
- replacing the blade with a new that has a moment weight as close as possible to the old one
- always change a pair of blades with similar moment weight
what do axial floe and centrifugal flow have in common
they are very sensitive to change in the airflow which passes through the compressor
what is need for smooth airflow into the rotor
the correct relationship between the inlet velocity and the rotor speed is required
the airflow in the axial compressor is smooth as long as what
the angle on the rotor blades and stator vanes is small
what is compressor surge
a very severe form of compressor stall
what are compressor stall and surge caused by
problems in engine operations or damaged engine components
aircraft engines have three different design methods to prevent compressor stall and surge what are they
- compressor bleed valves
- dual or triple spool rotors
- variable compressor stator vanes
when are bleed valves opened
at low engine speeds
what is the most effect method of preventing compressor
variable stator vanes
what is the advantage of variable stator vanes
an optimum angle of attack on the following rotor blades can be reached for every engine speed
each stage of an axial flow compressor has a ratio of about …
1.3:1
what does the compression ratio varies with
RPM
