Theory for Multiple Choice Questions Flashcards
When calculating the torque of an axial flow turbomachine, which is the correct air velocity to use?
A. Absolute velocity
B. Relative velocity
C. Tangential velocity
D. Axial velocity
C
After landing a large civil airliner the pilot will likely deploy…
A. The hot thrust reversers
B. The cold thrust reversers
C. Both sets of thrust reversers
D. No thrust reversers
B
A common cause of compressor surge is thought to be which of the following?
A. High temperature in the compressor
B. The flame in the combustion chamber being extinguished
C. Aerodynamic stalling of the compressor blades
D. Axial velocity in the compressor being high
C
The quantity √𝑅𝑇 (where R is gas constant and T is temperature) has the same dimensions as?
A. Pressure
B. Velocity
C. Density
D. Energy
B
Which of the following processes will not change the speed of sound of a gas?
A. Expansion
B. Compression
C. Combustion
D. None, i.e. they all change the speed of sound
D
In a modern large turbofan engine, the melting point of the material used for the nozzle guide vane of the high-pressure turbine is most likely to be…
A. Lower than the temperature of the gas exiting the combustion chamber
B. Higher than the temperature of the gas exiting the combustion chamber
C. Similar to the temperature of the gas exiting the high-pressure compressor
D. Higher than any gas temperature in the whole engine
A
Which of the following processes does not involve energy being transferred into or out of the gas?
A. High speed gas flow through a compressor
B. High speed gas flow through a turbine
C. High speed gas flow through a nozzle
D. Combustion
C
Across which part of an axial compressor stage is there likely to be a higher pressure rise?
A. The rotor
B. The stator
C. Neither, it’s always split evenly
D. Could be either, it depends entirely on the individual engine desig
A
Considering the exit of a turbine in an aeroengine: which of the following statements is true?
A. The real (actual) temperature will be higher than the ideal (isentropic)
temperature
B. The real (actual) temperature will be lower than the ideal (isentropic)
temperature
C. The real (actual) temperature will be equal to the ideal (isentropic)
temperature
D. It depends on the design of the turbine
A
In an aeroengine the term “overall pressure ratio” refers to which of the following?
A. The pressure ratio across the whole engine
B. The pressure ratio across the fan
C. The pressure ratio across the main compressor
D. The pressure ratio across the whole compression system
D
Which one of the following is a primary way of improving the thermal efficiency of an aeroengine?
A. Lowering the jet velocity
B. Decreasing the overall pressure ratio
C. Increasing the turbine entry temperature
D. Using a larger diameter fan
C
In a real aeroengine the pressure from entry to the exit of the combustion chamber will…
A. Increase
B. Decrease
C. Stay the same
D. Increase or decrease depending on the flight condition
B
Which of the following non-dimensional numbers will be the least important for a turbo machinery designer?
A. Pressure ratio
B. Flow Mach number
C. Rotational Mach number
D. Reynolds number
D
Which single parameter will enable you to calculate the Mach number of an object?
A. Mach cone angle
B. Velocity of the object
C. Speed of sound of the surrounding gas
D. The sound level of the noise the object creates
A
If you have a shockwave in a convergent-divergent nozzle at a given exit pressure, what will happen to the shockwave if you reduce the exit pressure by a modest
amount?
A. The shockwave will move closer to the nozzle throat
B. The shockwave will move closer to the nozzle inlet
C. The shockwave will move closer to the nozzle exit
D. The shockwave will stay at the same location
C
