What is the configuration/description of a centrifugal compressor?
Short in length, spoke-like design, easy to manufacture, with high compression per stage.
Long in length, spoke-like design, easy to manufacture, with moderate compression per stage.
Long in length, spoke-like design, easy to manufacture, with high compression per stage.
Short in length, spoke-like design, easy to manufacture, with moderate compression per stage.
What are the advantages of a centrifugal compressor over an axial flow compressor?
Cheaper and easier to manufacture, more robust, better handling of FOD ingestion, less prone to stalling and surging, relatively lower in weight.
Cheaper and easier to manufacture, more robust, better handling of FOD ingestion, less prone to stalling and surging, relatively higher in weight.
Cheaper and easier to manufacture, more robust, better handling of FOD ingestion, more prone to stalling and surging, relatively lower in weight.
Cheaper and harder to manufacture, more robust, better handling of FOD ingestion, less prone to stalling and surging, relatively lower in weight.
What is an impellor?
The internal rotating component of a centrifugal compressor, which takes inlet/intake air at its centre and compresses it by centrifugal force. Sometimes known as the rotor.
The internal rotating component of a axial compressor, which takes inlet/intake air at its centre and compresses it by centrifugal force. Sometimes known as the rotor.
The internal rotating component of a axial compressor, which takes inlet/intake air and compresses it by centrifugal force. Sometimes known as the rotor.
The internal rotating component of a centrifugal compressor, which takes inlet/intake air and compresses it by centrifugal force. Sometimes known as the rotor.
What is the purpose of the diffuser?
To decrease the airs velocity and increase its pressure
To decrease the airs velocity and decrease its pressure
To increase the airs velocity and increase its pressure
To increase the airs velocity and decrease its pressure
Where does the air pressure increase as it passes through centrifugal compressor?
Air pressure increases progressively through the impeller and increases rapidly through the diffuser
Air pressure decreases progressively through the impeller and increases rapidly through the diffuser
Air pressure increases rapidly through the impeller and increases progressively through the diffuser
Air pressure increases rapidly through the impeller and increases rapidly through the diffuser
How does the velocity and pressure vary through a centrifugal compressor?
Velocity and pressure both increase through the impeller, however through the diffuser the velocity decreases and pressure increases
Velocity and pressure both decrease through the impeller, however through the diffuser the velocity decreases and pressure increases
Velocity and pressure both decrease through the impeller, however through the diffuser the velocity increases and pressure increases
Velocity and pressure both increase through the impeller, however through the diffuser the velocity increases and pressure increases
What is the configuration/description of an axial flow compressor?
Multiple stages of rotating aerofoil blades and fixed vanes (stators), with a large mass flow capacity and high efficiency.
Multiple stages of rotating aerofoil blades and fixed vanes (stators), with a large mass flow capacity and high thrust
Multiple stages of rotating aerofoil blades and moving vanes (stators), with a large mass flow capacity and high thrust
Multiple stages of rotating aerofoil blades and moving vanes (stators), with a large mass flow capacity and high efficiency.
What are the advantages of an axial flow compressor over a centrifugal compressor of the same frontal diameter?
Higher compressor pressure ratios and greater mass airflow
Higher compressor airflow ratios and greater mass airflow
Higher compressor speeds and greater mass airflow
Higher compressor speeds and greater fuel capacity
What are the advantages of an axial flow compressor over a centrifugal compressor?
A lower frontal area for a given mass airflow, which allows for a smaller diameter engine, achieves higher compression ratios more efficiently, lower pressure rise per stage, a much lower airflow exit velocity compared to its inlet velocity
A higher frontal area for a given mass airflow, which allows for a smaller diameter engine, achieves higher compression ratios more efficiently, lower pressure rise per stage, a much lower airflow exit velocity compared to its inlet velocity
A higher frontal area for a given mass airflow, which allows for a smaller diameter engine, achieves higher compression ratios more efficiently, higher pressure rise per stage, a much lower airflow exit velocity compared to its inlet velocity
A lower frontal area for a given mass airflow, which allows for a smaller diameter engine, achieves higher compression ratios more efficiently, higher pressure rise per stage, a much lower airflow exit velocity compared to its inlet velocity
What is the definition of the compressor pressure ratio?
The ratio of the compressor outlet pressure to the compressor inlet pressure
The ratio of the compressor outlet pressure to the compressor inlet temperature
The ratio of the compressor outlet velocity to the compressor inlet velocity
The ratio of the compressor outlet velocity to the compressor inlet temperature
What is the typical total compressor ratio of a single stage centrifugal compressor?
Up to about 7.5:1
Up to about 15:1
Up to about 20:1
Up to about 30:1
What is the typical total compressor ratio of a double stage centrifugal compressor?
Up to about 3:1
What is the typical total pressure ratio of a modern axial flow compressor?
20:1, but up to 30:1 in come cases
10:1, but up to 20:1 in come cases
10:1, but up to 30:1 in come cases
15:1, but up to 20:1 in come cases
How does the temperature, pressure and velocity of the air change as it passes through each stage of an axial flow compressor?
Temperature and pressure progressively increase and the axial velocity increases across the rotors and decreases across the stators, but overall velocity decreases considering the effect of the diffuser
Temperature and pressure progressively increase and the axial velocity decreases across the rotors and decreases across the stators, but overall velocity decreases considering the effect of the diffuser
Temperature and pressure progressively increase and the axial velocity decreases across the rotors and increases across the stators, but overall velocity decreases considering the effect of the diffuser
Temperature and pressure progressively increase and the axial velocity increases across the rotors and increases across the stators, but overall velocity decreases considering the effect of the diffuser
What is the function of inlet guide vanes?
The inlet guide vanes are designed to direct the airflow onto the first stage rotors at an appropriate angle of attack.
The inlet guide vanes are designed to direct the airflow onto the last stage rotors at an appropriate angle of attack.
The inlet guide vanes are designed to direct the airflow onto the last stage rotors at an high angle of attack.
The inlet guide vanes are designed to direct the airflow onto the first stage rotors at an high angle of attack.
What is the function of the variable inlet guide vanes?
To change angle depending on flow characteristics, directing the airflow onto the first stage rotors at the optimal angle of attack, thereby reducing the chance of a compressor stall during operation off design (at low) rpm.
To change angle depending on pressure characteristics, directing the airflow onto the first stage rotors at the optimal angle of attack, thereby reducing the chance of a compressor stall during operation off design (at low) rpm.
To change angle depending on pressure characteristics, directing the airflow onto the first stage rotors at the optimal angle of attack, thereby reducing the chance of a compressor stall during operation off design (at high) rpm.
To change angle depending on flow characteristics, directing the airflow onto the first stage rotors at the optimal angle of attack, thereby reducing the chance of a compressor stall during operation off design (at high) rpm.
What is the function of the variable stators in an axial flow compressor?
The variable stators are designed to direct the airflow onto the subsequent stage of rotors at the optimum angle of attack, thereby increasing the compressor pressure ratio.
The variable stators are designed to direct the airflow onto the first stage of rotors at the optimum angle of attack, thereby increasing the compressor pressure ratio.
The variable stators are designed to direct the airflow onto the first stage of rotors at the optimum angle of attack, thereby increasing the overall thrust
The variable stators are designed to direct the airflow onto the subsequent stage of rotors at the optimum angle of attack, thereby increasing the overall thrust
What is the primary function of each row of stator blades?
To convert the kinetic energy of the airflow into pressure energy
To convert the kinetic energy of the airflow into dynamic energy
To convert the dynamic energy of the airflow into kinetic energy
To convert the dynamic energy of the airflow into pressure energy
What is the secondary function of the stator blades?
To stop swirl in the air thereby maintaining axial flow as it passes through the compressor
To stop swirl in the air thereby maintaining centrifugal flow as it passes through the compressor
To allow swirl in the air thereby maintaining centrifugal flow as it passes through the compressor
To allow swirl in the air thereby maintaining axial flow as it passes through the compressor
What are the function of the rotors and stators in an axial flow compressor?
The rotors accelerate the airflow and the stators decelerate the flow to increase the airs pressure
The rotors decelerate the airflow and the stators decelerate the flow to increase the airs pressure
The rotors dedcelerate the airflow and the stators accelerate the flow to increase the airs pressure
The rotors accelerate the airflow and the stators accelerate the flow to increase the airs pressure
What shape does an axial flow compressor form towards the combustion chamber?
A converging duct
A diverging duct
A straight duct
Why does the air annulus area decrease towards the high pressure end of an axial flow compressor?
To allow for the reduction in the volume of air as its pressure progressively increases and to maintain the axial velocity of the air constant as the density increases
To allow for the increase in the volume of air as its pressure progressively increases and to maintain the axial velocity of the air constant as the density decreases
To allow for the increase in the volume of air as its pressure progressively increases and to maintain the axial velocity of the air constant as the density increases
To allow for the reduction in the volume of air as its pressure progressively increases and to maintain the axial velocity of the air constant as the density decreases
Why is there only a small pressure increase across each stage of an axial flow compressor?
Because the aerofoil blades are, by necessity, quite small and consequently only produce a small amount of lift at each stage
Because the aerofoil blades are, by necessity, quite large and consequently only produce a small amount of lift at each stage
Because the aerofoil blades are, by necessity, quite large and consequently only produce a small amount of thrust at each stage
Because the aerofoil blades are, by necessity, quite small and consequently only produce a small amount of thrust at each stage
What is a likely result from unstable airflow through a compressor?
A compressor stall.
A turbine stall.
An engine mafunction
A partial loss of power
What determines the angle of attack of a compressor blade at a given blade angle at any given time?
The RPM of the compressor an the TAS of the airflow
The angle of the airflow from the previous location
The smoothness of the air entering
The RPM of the turbine and the TAS of the airflow
What is the condition that leads to compressor stalls?
The axial velocity of the airflow is too low relative to the RPM.
The axial pressure of the airflow is too low relative to the RPM.
The axial temperature of the airflow is too low relative to the RPM.
The axial density of the airflow is too low relative to the RPM.
What is the principle effect/purpose of the bleed valves/bands in the compressor?
To offload the compressor (LP and HP) and increase the mass airflow through the early stages of the compressor, during acceleration from low engine speed thereby reducing the possibility of compressor stall and surge at low rpm.
To offload the compressor (LP and HP) and reduce the mass airflow through the early stages of the compressor, during acceleration from low engine speed thereby reducing the possibility of compressor stall and surge at low rpm.
To offload the compressor (LP and HP) and reduce the mass airflow through the early stages of the compressor, during acceleration from low engine speed thereby negating the possibility of compressor stall and surge at low rpm.
To offload the compressor (LP and HP) and increase the mass airflow through the early stages of the compressor, during acceleration from low engine speed thereby negating the possibility of compressor stall and surge at low rpm.
What positions are the surge/stall bleed valves or bleed bands during engine acceleration?
Open at low and increasing rpm, progressively closing as rpm increases to design rpm
Closed at low and increasing rpm, progressively opening as rpm increases to design rpm
Closed at high and increasing rpm, progressively opening as rpm increases to design rpm
Open at high and increasing rpm, progressively closing as rpm increases to design rpm
Do turbine engines use the same compressor bleed outlets for surge/stall protections as they do for environmental control systems?
No
Yes
What is the normal source of bleed air at high and moderate (climb and cruise) power settings?
The low pressure compressor
The high pressure compressor
The intermediate pressure compressor
Both the low and high pressure compressors in a two spool engine,, and all three of the low, intermediate and high pressure compressors in a three spool engine.
What is the normal source of bleed air at low (descent) power settings?
What are the effects of bleeding air off the compressor for systems such as anti-icing?
Gas temperature increases, thrust reduces and SFC increases.
Gas temperature reduces, thrust reduces and SFC increases.
Gas temperature reduces, thrust reduces and SFC reduces.
Gas temperature increases, thrust reduces and SFC reduces.
