WorksheetsInlet systems, compressors
Total questions: 39
Worksheet time: 20mins
An Ideal intake duct would do what?
Provide constant pressure airflow to the compressor under all flight conditions.
Decrease the engine's initial power output to avoid compressor stall.
Disrupt the airflow to the compressor to increase turbulence.
Increase the temperature of the air entering the engine.
What is the purpose of an intake?
Reduce drag and increase pressure
Increase drag and decrease pressure
Reduce pressure and deliver airflow to the fan/compressor face at an even pressure spread
Increase pressure and redirect airflow onto the high pressure compressor
What does the air intake for a typical high bypass turbo fan do to the pressure and velocity of the air entering the compressor, is the duct convergent or divergent?
Divergent, decreases velocity and increases pressure.
Convergent, decreases velocity and increases pressure.
Convergent, increases velocity and decreases pressure.
Divergent, increases velocity and decreases pressure.
During a climb to altitude drag on the compressor blades:
Increases giving good efficiency.
Increases giving poor efficiency.
Reduces giving good efficiency.
Reduces giving poor efficiency.
The compressor idling speed of an uncompensated gas turbine engine will increase:
at higher ambient temperature
with higher than sea level density
at altitudes lower than sea level
at lower ambient temperature
What happens to airflow pressure and velocity through both rotors and stators in an axial flow compressor?
Velocity decreases through rotors and decreases through stators and increases in pressure through both.
Velocity decreases through rotors and increases through stators and decreases in pressure through both.
Velocity increases through rotors and decreases through stators and increases in pressure through both.
Velocity decreases through rotors and increases through stators and increases in pressure through both.
One stage of an axial flow compressor consists of:
One rotor assembly and one row of stator vanes
One stator assembly and one row of guide vanes
One rotor and one impeller assembly
One impeller and one diffuser assembly
As air passes through an axial flow compressor, a pressure rise takes place in:
the impeller and the diffuser
the rotor blades only
both the rotor blades and the stator vanes
the stator vanes only
The pressure rise across a centrifugal compressor:
occurs in the impeller only
occurs in the diffuser only
is shared almost equally by the impeller and the diffuser
is always greater in the diffuser than in the impeller
A centrifugal compressor turbine compared to an axil flow has the following advantage:
Less frontal area
Lower weight
Less increase per stage
Efficient over a range of mass flow and pressure ratio combinations
The major disadvantage of a centrifugal compressor is that:
it cannot cope with a large mass flow of air
it cannot be used for a turbo jet engine
a larger turbine must be used
it is more prone to damage than the axial flow compressor
An advantage of a centrifugal compressor is that it is:
dynamically balanced
more robust and is easier to manufacture
unaffected by turbulence
able to handle a larger mass of air than an axial flow compressor
The pressure rise across each stage of an axial flow compressor is:
greater than that of a centrifugal compressor
between 1.1 and 1.2 to one
between 3 and 5 to one
twice the inlet pressure
To gain a greater pressure ratio than 4:1:
two centrifugal compressors can be placed in parallel
two centrifugal compressors can be placed in series with each other
the compressor diameter must be reduced
the cascade vanes must be convergent
The compression ratio is:
The ratio between inlet pressure and compressor discharge pressure
The ratio between the compressor inlet pressure and the exhaust outlet pressure
Equal to the number of compressor stages
Is not a real thing
What is the definition of the bypass ratio of a turbofan engine?
The ratio of the mass of the air bypassing the engine core, to the mass of the air passing through the engine core.
It is a key factor in determining the noise level of the engine, as a higher bypass ratio typically results in higher noise emissions.
Is a measure of the efficiency of the engine in terms of how much thrust is generated for a given amount of fuel consumption.
The ratio of the mass of the fuel injected into the engine core, to the mass of the air passing through the engine core.
The ratio of the mass of the oil used for lubrication, to the mass of the air passing through the engine core.
The Bypass Ratio of an engine is the ratio of:
Primary air to tertiary air.
Cold stream air to that flowing through the hot core of the engine.
Exhaust gas pressure to air intake pressure.
Primary air to secondary air.
What are variable inlet guide vanes?
The low pressure compressor
The low pressure turbine
The first stage vanes after the engine inlet
The last stage vanes
The ring of blades which sometimes precede the first rotor stage of an axial flow compressor are called:
the first stage stator blades
variable inlet guides vanes
first stage diffuser blades
nozzle guide vanes
Variable inlet guide vanes:
deflect air past the compressor
adjust the relative airflow position
deflect air past the turbine
induce air into a centrifugal compressor
Compressor blades are twisted from root to tip:
to decrease the pressure
to maintain a correct angle of attack
to reduce the relative airflow
to give added rigidity to the blade structure
What do stators in the compressor do?
Decrease velocity and increase pressure
Increase velocity and increase pressure
Decreases both velocity and pressure
Increases both velocity and pressure
What is the purpose of variable stator vanes?
To control and regulate airflow through a compressor.
To direct airflow onto next compressor blades, used in high compression ratio engines.
To adjust the fuel flow rate in a jet engine.
To provide extra lift during take-off and landing of an aircraft.
The purpose of the diffuser vanes in a centrifugal compressor is to:
increase the charge temperature
convert kinetic energy into pressure energy
convert pressure energy into kinetic energy
increase the air velocity
What happens to airflow through a diffuser?
Pressure and temperature increase and velocity decreases
Pressure and velocity increase and temperature decreases
Temperature increases and velocity and pressure decrease
Pressure and temperature decrease and velocity increases
As air flows through the turbine section energy is removed, what design feature of the turbine section is evidence of this?
Turbine A/A reduces
Turbine diameter increases as air flows through
Turbine casing thickness increases
Turbine stage count increases
Cascade vanes are fitted in which part of the centrifugal compressor?
the air inlet
the outlet elbow
the impeller
the diffuser
The cross-sectional area of the air annulus is reduced as it approaches the combustion chamber:
to maintain the axial velocity of the air toward the combustion chamber
to maintain the volume of the air under rising pressure
to prevent an increase of the velocity of the air under rising pressure
to allow longer blades to be used towards the latter stages of the compressor
Bleed air for engine anti-icing is provided by:
the bleed valves
the turbine stages
the compressor
the combustion chambers
A compressor blade will stall when:
the air axial velocity and rotational speed relationship is disturbed
the mass airflow and speed relationship is constant
the speed of the gas flow through the turbine falls below Mach 0.4
the compression ratio exceeds 10 to 1
Compressor surge will occur when:
all stages are at maximum efficiency
all stages have stalled
all stages are at maximum rpm
there is a partial breakdown of airflow through the compressor
A compressor stall causes:
the vibration level to increase with a decrease in the turbine gas temperature
an increase in the turbine gas temperature and the vibration level
the rotation of the engine to stop suddenly
the airflow through the engine to stop suddenly
From a Pilots perspective, where i a compressor stall most likely to occur?
Bird Strike
Max crosswind landing
High speed cruise at max certified altitude
Lowering flap
What effect will severe icing in the intake have on a high bypass engine?
The axial velocity of the air will decrease with an increase in the angle that the resultant airflow forms with the compressor blades chord line and a possible stall.
The axial velocity of the air will increase with a reduction in the angle of attack of the airflow with the compressor blades and a possible stall.
The axial velocity of the air will decrease with a reduction in the angle of attack of the airflow with the compressor blades and a possible stall.
The axial velocity of the air will increase with an increase in the angle of attack of the airflow with the compressor blades and a possible stall.
In the event of a surge occurring the correct action to be taken is:
to close the throttle quickly
to close the throttle slowly
to open the throttle fully
to close the LP fuel valve
Fuel is regulated on rapid engine acceleration:
to prevent inducing a compressor stall and surge
to prevent detonation in the combustion chambers
because the rapid response of the compressor might cause a flame out
because the cooling effect of too much fuel would cause a drop in pressure in the combustion chamber
What is the first indication of large compressor stall?
Loud Bang
Condensation builds up
Decreasing turbine temperatures
Buffeting wings
What are the indications of a compressor stall?
Popping surging noise, high EGT, fluctuating RPM
A sudden increase in fuel efficiency, low EGT
Smoke emanating from the compressor inlet, fluctuating RPM
The nose pitches down and the aircraft sinks
Bleed valves are automatically opened:
at low engine rpm to prevent the compressor stalling
at maximum rpm to prevent compressor stall
at low rpm to prevent the turbine stalling
during engine acceleration to prevent turbine surge
