Gas Turbine Engine Flashcards
Can an engine start by itself?
No
Is it safe to cut holes in a turbine blade to improve cooling?
No
Purpose of shroud at the tip of the turbine blades?
Help to minimise tip losses as well as provide a damper to prevent vibrations
Annular combustors suffer from?
Low rigidity
How to prevent engine stall due to choked flow?
Extract bleed air from the compressor stage after the stalled section.
Centrifugal Compressors have the following advantages compared to axial compressors? (5)
- Simpler
- More rugged
- Cheaper to manufacture
- Greater design flexibility
- Less severe stall characteristics
Considerations for the design of Air Inlets include:? (5)
- Noise attenuation
- Radar attenuation (stealth)
- Nozzle secondary airflow
- Dust / Sand Particle Separation
- Airflow bypass to assist in engine starting
Does an aircraft’s velocity affect the thrust produced by its engines?
Yes.
What is the purpose of flame holder?
To contains the flame of combustion and prevents flame out.
Is ice formation desirable?
Undesirable
Air starting of an engine involves the use of? (3)
an APU, a GPU or a Cartridge.
What is required for afterburner?
A variable-area exhaust nozzle
Turboshaft engines contains a?
Free turbine
[INFO]
Fnet = (Mass Flow Rate)(Vexit - Vinlet) + Aexit(Pexit - Pin) + …
Thus, you can accelerate a large mass through a small increase in velocity or a small mass through a large increase in velocity.
What is Mach number?
The ratio of the speed of a body to the speed of sound in the surrounding medium.
What is Brayton Cycle?
an idealised cycle with no energy losses to the surroundings. In actual cycles, the amount of energy lost is accounted for through process efficiency.
What is the purpose of the exhaust nozzle?
To regulate back pressure on the turbine, accelerate exhaust gases to achieve desired jet velocity and deflect/reverse thrust.
The exhaust nozzle is “used/not used” to increase backpressure?
not used
Cooling methods in the turbine include? (4)
- Convection
- Impingement
- Film
- Transpiration
Low Cycle Fatigue
failure typically occurs <100,000 cycles and is due to engine start/stop or throttle cycle.
High Cycle Fatigue
failure typically occurs >100,000 cycles and is normally caused by vibratory stress.
The Health & Usage Monitoring System (HUMS) is used for?
monitoring the health of the engine, which involves usage monitoring and flight data acquisition. It does not retrieve weather data or monitor air conditioning.
Magnetic chip detectors are used for?
To catch ferrous particles in the oil system.
High viscosity oil is used in turbo-propeller engines due to?
high mechanical loads involved.
The Variable Divergent/Convergent Nozzle of the F100 engine is designed to?
significantly reduce the actuation forces necessary to reposition the nozzle.
In the Axial Compressor, stator or rotor comes first?
stators come before rotors to direct air into the rotor.
Air inlet ducts are generally rated by?
Their duct-pressure efficiency ratio and ram recovery point.
Common Thermodynamic Processes (3)
- Isobaric - Constantly Pressure
- Isochoric - Constant Volume
- Isentropic - Constant Entropy & Temperature
Thermal Barrier Coating (TBC) is applied to stationary components in the combustion chamber to?
Reduce wall temperatures and gradients by reflecting gas radiation or providing a layer of insulation between hot gases and the wall.
The disadvantage of using an airblast atomiser is?
at low air velocities, such as during start-up, the fuel droplets tend to be large, limiting the efficiency of the engine.
