Gas Turbine Compressor Flashcards
The less work the turbine has to do to drive the compressor, the more energy is
left to generate blank
Thrust
Modern designs achieve up to X:1. compression ratio in an axial compressor
35:1
Axial flow compressor; Air flows parallel to the blank
Axial flow compressor; Air flows parallel to the axis of the engine
What happens to pressure in a divergent duct.
Increases.
What happens to tempurature in a divergent duct.
Increases
What happens to velocity in a divergent duct.
Increases
What happens to velocity in a divergent duct in a centrifugal compressor?
Increases
What happens to pressure in a centrifugal diffuser?
Increases
What happens to tempurature in a centrifugal diffuser?
Increases
What happens to velocity in a centrifugal diffuser?
Decreaser
What compressor cannot aero dynamically stall?
Centrifugal
Generally, a maximum compression ratio of X:1 per stage can be achieved in centrifugal compressor
4.5
To achieve a greater mass flow the impeller can be blank: a double entry
impeller in a centrifugal compressor.
Double sided.
To achieve a greater blank the impeller can be double-sided: a double entry
impeller in a centrifugal compressor
Mass flow
All large commercial designs use blank compressor
Axial flow
A rotor + a stator = blank
A stage
Rotor adds blank to the airflow.
Energy
The pressure rise across a single stage is usually only about blank%
10-20
The partial breakdown of airflow through an engine is also known as what?
A stall
a complete reversal of the airflow through the compressor is know as a what?
Deep surge
Gas turbine engines have a very narrow operating band, limited by the air mass
flow and the overall pressure ratio. Beyond this operating band the compressor
becomes blank.
Unstable
What happens to the pressure ratio at high rpms?
Increases
What rpm would you have a higher margin of safety?
High
A stall results in reduced blank through the compressor and thus reduced thrust
Air mass flow
If fuel flow isn’t reduced the combustion temperature will quickly rise. The principal
symptoms of compressor stall is a high blank
EGT
In an extreme case flames may be seen exiting the intake:
• This is blank and is often accompanied by a loud bang
Deep surge
Over-fueling can cause a surge by creating excessive blank in the combustor:
• Over-fueling surge has been mostly eliminated by modern electronic fuel control units.
Pressure
What is a variable inlet guide vane used for?
Prevent stall/surge
What is a variable inlet guide vane?
They change aoa to prevent stall
Why are multiple stool compressors used?
To prevent stall
(Handling bleeds) Inter-stage bleed valves vent pressure during the start to improve the axial flow
across the blank
Compressor
Generally, the valves are blank (under spring pressure) with the engine switched
off and gradually close, to become fully blank at ground idle speed
Open - closed
If a compressor stall occurs, quickly establish straight flight and blank the blank blank
Close the thrust leavers
What would you find on a Lp compressor fan blade?
Snubber
The tips of the stators are often joined by a blank to avoid energy losses and
reduce vibration
Shorid
What does a shroud do?
Reduce energy loss and vibration
What spins the compressor?
Turbinw
Is a centrifugal or axial compressor cheaper?
Centrifugal
Does a centrifugal or axial compressor have a higher compression ratio?
Axial (35:1)
Is a centrifugal or axial compressor more efficient?
Axial compressor
At what P does the highest pressure occur?
P3
The Compressor will deliver high pressure (compressed) air into the mid-frame
diffuser (Px)
P3
The diffuser also allows a separation of airflow into dilution air(cooling) (Xx%) and
combustion air (keeps fire alight) (Xx%);
80% 20%
What do you need to check is increasing when you press the engine anti ice?
EGT
Bleed Air is taken from several compressor stages to be used for various internal
engine tasks and externally to supply hot or high pressure air to aircraft systems
• But this blanks mass flow and increases temperature, hence:
• blanks power thrust
• blanks specific fuel consumption
Reduces mass flow reduces thrust increases fuel consumption
X pressure air is used to ‘cool’ the turbine nozzle guide vanes, the turbine blades and the turbine discs
XP air is used to cool the accessories
High - low
