Gas Turbine Principles Flashcards
What is the thrust equation?
Thrust = mass air flow x (velocity of exhaust - true air speed) + cross sectional area of exhaust x ( jet static pressure - ambient pressure)
What is the air that goes around the outside of a turbine called.
Bypass air
Total thrust = fan thrust + blank thrust
Core
Pressure thrust (Pf) can be considered when the exhaust nozzle becomes ‘blanked’
Chocked
1 horse power is how much thrust?
2.5 pounds
What are the 4 parts of the brayton cycle on a gas turbine?
Intake - compression - combustion - exhaust
Whats the difference between the otto cycle and the brayton cycle?
Brayton happens all at once, continuously.
Combustion takes place at constant blank, in a gas turbine.
Pressure
Where does the highest temperature occur within the gas turbine?
Primary zone within the combustion chamber
What is the highest thrust that the engine produces?
Static thrust
What is a flat rated engine?
limited at temperature below 15 degrees
Bleed air blanks the mass flow and thus reduces thrust.
Reduces.
Intake heating systems blank the air density and so blank mass flow
Reduce
What is thermal efficiency?
Fuel energy to kinetic energy.
What does EPR stand for in a turbine engine!
Engine pressure ratio
What is propulsive energy?
Kinetic energy translated into propulsive force.
How do the gas parameters change within the stator of a compressor stage? The temperature increases, the…Pressure blanks and the speed blanks
Pressure increases and the speed decreases.
Which of these statements about an impulse turbine are correct or incorrect?
I. The pressure drops across the nozzle guide vanes
II. The pressure drops across the rotor blades
Correct - incorrect
In subsonic airflows, the convergent exhaust unit is designed to convert… pressure into blank
Speed
The maximum temperature in a gas turbine engine is limited by the… temperature at the blank
Turbine.
Both gas turbine and piston engines use a cycle made up of induction, compression, combustion and exhaust phases. Which of these statements about a gas turbine are correct?
- The process in a gas turbine engine is continuous
- Theoretically the combustion occurs at constant volume
Correct - incorrect
Jet engine total efficiency indicates the efficiency at which… blank power is transformed into blank power
Chemical to propulsive
The bypass ratio:
I. is the ratio of bypass air mass flow to HP compressor mass flow
II. can be determined from the inlet air mass flow and the HP compressor mass flow
Both correct
One of the advantages of multiple-spool jet engine designs is that…a smaller air starter driving only a single blank can be used.
Spool
One advantage of having three instead of two spools in some high-bypass turbofan engine is that…fewer variable stator vanes and variable inlet guide vanes are required to prevent blank stall at high/low rotor speeds.
Compressor at low
To ensure efficient combustion in a gas turbine engine…it must be capable of creating the optimal blank blank blank blank.
Mixture of air and fuel
The primary reason for a limitation being imposed on the temperature of gas flow in a gas turbine is to…ensure that the maximum acceptable temperature at the blank blank is not exceeded.
Turbine blades
Compressor stall in a gas turbine engine is due to… an excessively high blank of the rotor blades.
an excessively high angle of attack of the rotor blades.
Which of these statements is correct with regards to stator vanes within axial flow compressors? Pressure increases/decreases due to the air’s blank energy being converted into pressure energy.
Increases kinetic energy
IMPULSE:
* Guide Vanes –> Pressure blanks
* Rotor Blades –> Pressure is Constant
REACTION
* Guide Vanes –> Pressure blank
* Rotor Blades –> Pressure Drops
IMPULSE:
* Guide Vanes –> Pressure Drops
* Rotor Blades –> Pressure is Constant
REACTION
* Guide Vanes –> Pressure is Constant
* Rotor Blades –> Pressure Drops
IMPULSE:
* Guide Vanes –> Pressure Drops
* Rotor Blades –> Pressure blank
REACTION
* Guide Vanes –> Pressure is Constant
* Rotor Blades –> Pressure blank
IMPULSE:
* Guide Vanes –> Pressure Drops
* Rotor Blades –> Pressure is Constant
REACTION
* Guide Vanes –> Pressure is Constant
* Rotor Blades –> Pressure Drops
What is the purpose of an exhaust nozzle?
Exhaust gasses have a higher velocity
Which of these statements about an impulse turbine are correct or incorrect?
I. The pressure rises across the nozzle guide vanes
II. The pressure remains constant across the rotor blades
Incorrect - correct
The bypass air in a turbo fan engine has the effect of a lower specific fuel consumption by causing an overall…increase/decrease in average exhaust gas flow velocity and a higher/lower mass flow.
Decrease higher
Which of these statements about compressor stall in a gas turbine engine are correct or incorrect?
I. A compressor stall is most likely to occur in a compressor designed for a high pressure ratio operating at high RPM
II. A compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor
Incorrect - correct
The purpose of variable by-pass valves in a high bypass turbofan engine between the LP compressor and the HP compressor (HPC) is to…prevent fan blank and LP compressor stall during engine start and blank rotor speeds.
Stall low
With regard to a jet aeroplane, specific range is the… blank flown per unit fuel of mass
Nautical airmiles
What is the main purpose of a diffuser? To reduce the blank of the gas entering the combustion chamber.
Velocity
The function of a vibrator (trembler mechanism) in gas turbine ignition systems is to provide…
Dc to transformer
When does a hung start occur?
Too low pneumatic
When does a hot start occur?
Tail wind or early cutout
