chapter 3 turbone Flashcards
(23 cards)
What is the main difference between turbofan and turbojet engines?
A turbofan engine uses a fan to bypass some air around the engine core to provide thrust, offering additional thrust without increasing fuel flow.
This is a key advantage of turbofan engines over turbojets.
Name the major components in a gas turbine engine.
Air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox, and accessory section.
These components are essential for the operation of a gas turbine engine.
What determines the amount of airflow through a turbine engine?
The forward speed of the aircraft, compressor speed, and air density.
These factors directly influence engine performance.
Name the two types of compressors commonly used in turbine engines.
Axial and centrifugal flow compressors.
These compressors are crucial for increasing air pressure before combustion.
Name two different methods for attaching turbine engine rotor blades to the rotor disks.
Dovetail-type root, Bulb-type root, Fir tree-type root.
These attachment methods affect the durability and performance of the rotor blades.
What is a split compressor system?
Also called dual or twin spool compressors, they are connected to the turbine section with two rotor shafts, one inside the other.
This design improves efficiency in engine operation.
What are the different types of combustion chambers used in turbine engines?
Can, annular, can-annular, and reverse flow annular.
Each type has unique characteristics that affect engine performance.
What prevents the combustion chambers from burning?
Cooling air along the inside of the liner.
This cooling mechanism is vital for maintaining engine integrity.
What is the purpose of the interconnecting tubes attached between can-type combustion chambers?
For flame propagation during start.
This ensures reliable ignition in multi-chamber designs.
What functions do axial flow turbine nozzles perform?
They direct the mass airflow to drive the turbine rotor at a specific angle.
Proper nozzle function is essential for effective turbine operation.
How is thermal stress relieved on a turbine disc?
By directing bleed air onto the face of the disk, or by grooves being cut in the disk.
These methods help maintain material integrity under high temperatures.
What are carbon seals used for in turbine engines?
They are used as oil seals for the rotor shaft bearings.
Effective sealing is critical for preventing oil leaks and ensuring engine performance.
What is shaft horsepower?
It is an indication of the torque developed by a turboprop or turboshaft engine.
This measurement is important for assessing engine performance.
Name the main components of a typical APU.
A small power turbine for power and bleed air, and an electrical generator.
The APU provides auxiliary power and support for aircraft systems.
When is the greatest demand placed on an APU?
When supplying bleed air.
This is crucial during engine start and other ground operations.
How is an APU generally started?
With its own electrical starter and battery power.
Reference: JSPT 3-35
Where does the APU get its fuel supply?
From one of the aircraft’s main fuel tanks.
Reference: JSPT 3-35
At what speed does a gas turbine APU operate and how is this speed maintained?
At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the rated speed.
Reference: JSPT 3-35
What is used to prevent a heavily loaded APU from exceeding its maximum EGT?
A load control valve modulates the pneumatic load to maintain EGTs within limits.
Reference: JSPT 3-35
How is an APU shut down and why is this procedure used?
After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period is typically three minutes.
Abrupt shutdown without cooling can cause thermal shock damage. Reference: JSPT 3-35
What powers the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?
Fuel pressure.
Reference: JSPT 3-35
What is fan blade shingling?
It is the overlapping of the midspan shrouds of the fan blade.
Reference: JSPT 3-15
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.
Reference: JSPT 3-15
