WorksheetsCombustion and turbine
Total questions: 15
Worksheet time: 8mins
A cannular combustion system is:
a set of flame tubes, each of which is mounted in a separate air casing
a set of flame tubes enclosed in a common air casing
one common flame tube enclosed in a common air casing
superior to the annular system because it only requires one igniter
One advantage of an annular combustion chamber system is that:
the diameter of the engine is reduced
there is unrestricted airflow at maximum rpm
there are no flame propagation problems
the air casing area is greater
Swirl vanes in the combustion chamber:
increase the velocity of the airflow
reduce the velocity of the airflow
prevent compressor stall
help to stabilize combustion
Shrouding of stator blade tips is designed to:
prevent tip turbulence
ensure adequate cooling
minimize vibration
prevent tip losses
The purpose of the tertiary airflow created in the combustion chamber is to:
reduce the gas temperature and cool the flame tube
form a toroidal vortex, which anchors and stabilizes the flame
reduce the gas temperature and cool the burner head
ensure complete combustion of the fuel
The air entering the combustion chamber is divided; a small percentage is used in combustion, the rest:
is syphoned off for airframe anti-icing purposes
is used only for cooling the gases before they exit the combustion chamber
is used to cool both the gases exiting the chamber and the walls of the air casing
is used to reduce the oil temperature and cool the turbine blades
What percentage of air entering the internal combustor is used for combustion?
50-60%
65-80%
25-40%
55-70%
When would you select ‘continuous’ ignition?
When volcanic ash clouds have been forecast in the area
Take-off, landing and when encountering significant turbulence or precipitation
Starting and shutting down
When using reverse thrust
Nozzle guide vanes are fitted before the turbine:
to increase the velocity of the airflow.
to decrease the velocity of the gas flow therefore increasing its pressure.
to increase the velocity of the gas flow therefore reducing its pressure.
to increase the temperature of the gas flow.
Over temp in a turbine engine is most critical where?
First stage of turbine assembly
Second stage of turbine assembly
Third stage of turbine assembly
Fourth stage of turbine assembly
The mixture of impulse and reaction blade shape in the average turbine blade is such that:
the inner half is impulse and the outer half is reaction.
the inner half is reaction and the outer half is impulse.
the leading edge is reaction and the trailing edge is impulse.
the trailing edge is reaction and the leading edge is impulse.
The impulse-reaction blade is twisted along its length so that:
there is a greater angle at the base than at the tip.
the gas flow is accelerated through the turbine.
the gas does equal work along the whole of its length.
the gas flow is decelerated through the nozzle guide vanes.
The diameter of the exhaust nozzle is very important. What would be the result of too large a diameter?
expansion is decreased, thrust decreased
expansion is decreased, thrust increased
expansion is increased, thrust decreased
expansion is increased, thrust increased
The main contributory factors which cause creep in turbine blades are:
high temperature and tensile loading.
high rpm and torque loading.
high rpm and high gas speeds.
high temperature and high gas speeds.
Blade creep is:
movement of the turbine blades around the turbine disc.
permanent elongation due to heat and centrifugal force.
temporary expansion due to temperature change.
temporary elongation due to centrifugal forces.
