15.1 MCQ Flashcards
In the dual axial-flow or twin spool compressor system, the first stage turbine drives the
a) N1 compressor
b) N1 and N2 compressors
c) N2 compressor
c) N2 compressor
A by-pass engine LP compressor
a) supplies only the required quantity of combustion
b) supplies less air than is required for combustion
c) supplies more air than is required for combustion
c) supplies more air than is required for combustion
A bypass ratio of 5:1 indicates that the bypass flow is
a) equal to 1/5 of the hot stream
b) five times the cold stream
c) five times the hot stream
c) five times the hot stream
A free turbine is usually found on a
a) Turbo-jet
b) Turbo- fan
c) Turbo prop
c) Turbo prop
A high bypass engine results in
a) lower propulsive efficiency
b) overall faster airflow
c) overall slower airflow and greater propulsive efficiency
c) overall slower airflow and greater propulsive efficiency
A jet engine derives its thrust by
a) drawing air into the compressor
b) impingement of the propelling gases on the outside air
c) reaction of the propelling gases
c) reaction of the propelling gases
A method of comparing engine efficiencies is by comparing
a) thrust to weight ratio
b) fuel consumption
c) specific fuel consumption
c) specific fuel consumption
A nozzle is ‘choked’ when the gas flow or air flow at the throat is
a) subsonic
b) Transonic to supersonic/sonic
c) hypersonic
b) Transonic to supersonic/sonic
A powerplant consists of
a) a basic engine plus E.C.U
b) the complete engine as it would be found on aircraft including all connections, controls, cowlings, intake etc
c) a basic engine plus thrust reverser, exhaust system and gear box with accessories
b) the complete engine as it would be found on aircraft including all connections, controls, cowlings, intake etc
A turbo jet engine gives
a) small acceleration to a large mass of air
b) large acceleration to a small mass of air
c) large acceleration to a large weight of air
b) large acceleration to a small mass of air
A turbo-shaft engine has
a) a mechanical connection between compressor and turbine
b) none of the above
c) the power shaft is not connected to the compressor
a) a mechanical connection between compressor and turbine
An advantage of a centrifugal compressor is
a) it is unaffected by turbulence
b) it is dynamically balanced
c) it is robust and can stand some shock from ‘icing up
c) it is robust and can stand some shock from ‘icing up
As subsonic air flows through a convergent nozzle the velocity
a) increases
b) decreases
c) remains constant
a) increases
Bernoulli’s Theorem states that at any point in a flow of gas
a) the static pressure is less than the dynamic pressure
b) the static pressure and dynamic pressure are equal
c) the total energy remains constant
c) the total energy remains constant
Engine thrust varies with temperature
a) low temperature gives greater mass flow and therefore greater thrust
b) low temperatures give low thrust
c) increase in temperature gives greater thrust because of low friction in compressors
a) low temperature gives greater mass flow and therefore greater thrust
In a choked nozzle velocity has increased to max and
a) density decreases
b) pressure decreases
c) pressure has increase
c) pressure has increase
In a free turbine
a) there is a direct drive with a free-wheel unit
b) there is no mechanical connection with the components
c) there is a clutch between compressor and power output shaft
b) there is no mechanical connection with the components
In a turbo jet engine, combustion occurs at
a) constant velocity
b) constant volume
c) constant pressure
c) constant pressure
Increasing ram effect with increased speed
a) reduces thrust due to reduced turbine temperature
b) increases thrust due to increased maximum airflow
c) reduces thrust due to reduced compressor efficiency
b) increases thrust due to increased maximum airflow
On an axial flow, dual compressor forward fan engine, the fan turns the same speed as the
a) high pressure compressor
b) low pressure turbine
c) forward turbine wheel
b) low pressure turbine
Ram effect” due to aircraft forward speed will cause the efficiency of the engine to
a) remain constant
b) increase
c) decrease
b) increase
The efficiency of a gas turbine engine at high altitude
a) decreases (note: engine aircraft combination as in our system)
b) increases (engine theory only)
c) remains constant
a) decreases (note: engine aircraft combination as in our system)
The forces driving most turbines around are due to
a) reaction only
b) impulse only
c) impulse and reaction
c) impulse and reaction
The stator vanes in an axial-flow compressor
a) convert velocity energy into pressure energy
b) convert pressure energy onto velocity energy
c) direct air into the first stage rotor vanes at the proper angle
a) convert velocity energy into pressure energy
The symbol for designating the speed of a single compressor engine is
a) N.G (gas generator Nf free turbine)
b) N
c) N1
c) N1
The working fluid of a gas turbine engine is
a) air
b) gasoline
c) kerosene
a) air
Thrust
a) increases with high temperature
b) decreases with low temperature
c) increases with low temperature
c) increases with low temperature
What purpose do the diffuser vanes of a centrifugal compressor serve?
a) To convert kinetic energy into pressure energy
b) To increase the air velocity.
c) To convert pressure energy into kinetic energy.
a) To convert kinetic energy into pressure energy
When a volume of air is compressed
a) no heat is lost or gained
b) heat is lost
c) heat is gained
c) heat is gained
