Turbine Engines Flashcards
Explain the main difference and advantage of turbo fan over turbo jet engines.
A turbo fan uses a fan to bypass air around the engine core and provide thrust.
This provides additional thrust without increasing fuel flow.
Name the major components in a gas turbine engine:
Air inlet.
Compressor section
Combustion section.
Turban section.
Exhaust section.
Gearbox and accessory section.
What determines the amount of air flow through a turbine engine?
The forward speed of the aircraft.
Compressor speed.
Air density.
Name the two types of compressors commonly used in turbine engines
Axial and centrifugal flow compressors.
Name two different methods for attaching turbine engine rotor blades to the rotor discs:
Dovetail type root.
Bulb type root.
Fir tree type root.
What is a split compressor system?
Split/dual/twin sport compressors are connected to the turbine section with two rotor shafts, one inside the other.
What are the different types of combustion chambers used in turbine engines?
Can.
Annular.
Can annular.
Reverse flow annular.
What prevents the combustion chambers from burning?
Cooling air along the inside of the liner.
What is the purpose of the interconnecting tubes attached between can type combustion chambers?
For flame propagation during start up.
What function do axial flow turbine nozzles perform?
They direct the mass airflow to drive the turbine rotor at a specific angle.
How is thermal stress relieved on a turbine disc?
By directing bleed air onto the face of the disc, or by grooves being cut in the disc.
What are carbon seals used for in turbine engines?
They are used as oil seals for the rotor shaft bearings.
What is shaft horsepower?
It is an indication of the torque developed by a turbo prop or turbo shaft engine.
Name the main components of a typical APU:
1) A small power turbine for power and bleed air.
2) An electrical generator.
When is the greatest demand placed on an APU?
When supplying bleed air.
How is an APU generally started?
With its own electrical starter and battery power.
Where does an APU get its fuel supply?
From one of the aircraft’s main fuel tanks.
At what speed does a gas turbine APU operate and how is the speed maintained?
At or near it’s rated speed.
The APU fuel control automatically adjusts fuel flow.
What is used to prevent a heavily loaded APU from exceeding its maximum EGT?
A load control valve modulates the pneumatic load to maintain EGT’s within limits.
How is an APU shut down and why is this procedure used?
The APU is unloaded by closing the bleed air valve, then run for a specified amount of time to allow the EGT to cool and stabilize. Typically three minutes.
An abrupt shut down could lead to thermal shock
What powers the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?
Fuel pressure
What is fan blade shingling?
The overlapping of the mid span shrouds of the fan blade.
When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?
Any rubbing sound, or other unusual noises from the engine.
