15.4 Compressors (Level 1, 4 Questions) Flashcards
(105 cards)
1
Q
What is the primary function of the first stage in a gas turbine cycle?
A) To cool the turbine blades
B) To ignite the fuel-air mixture
C) To supply air at correct pressure to the combustion chamber
A
C) To supply air at correct pressure to the combustion chamber
2
Q
What is the secondary function of the first stage in a gas turbine cycle?
A) To power the exhaust system
B) To provide bleed air from specific compressor stages for other systems
C) To reduce engine noise
A
B) To provide bleed air from specific compressor stages for other systems
3
Q
What does the first stage of a gas turbine cycle involve?
A) Fuel injection and ignition
B) Air intake and compression for combustion
C) Exhaust and cooling
A
B) Air intake and compression for combustion
4
Q
What is the method of air compression that decreases volume in a cylinder?
A) Bernoulli’s Principle
B) Turbine expansion
C) Piston Compression
A
C) Piston Compression
5
Q
Which principle is used in gas turbine compressors to compress air?
A) Pascal’s Law
B) Bernoulli’s Principle
C) Newton’s Third Law
A
B) Bernoulli’s Principle
6
Q
What is the first part of each compressor stage?
A) Stator
B) Rotor
C) Inlet Guide Vanes
A
B) Rotor
7
Q
Which component is stationary and directs airflow in a compressor?
A) Rotor
B) Turbine
C) Stator
A
C) Stator
8
Q
What is the function of Inlet Guide Vanes (IGVs)?
A) Compress fuel for combustion
B) Direct exhaust gases
C) Improve airflow into the first stage
A
C) Improve airflow into the first stage
9
Q
What is true about Inlet Guide Vanes (IGVs)?
A) They rotate with the compressor
B) They may be fixed or variable
C) They are part of the turbine section
A
B) They may be fixed or variable
10
Q
Which of the following is a type of gas turbine compressor?
A) Reciprocating Compressor
B) Centrifugal Flow Compressor
C) Rotary Vane Compressor
A
B) Centrifugal Flow Compressor
11
Q
Which type of compressor is used in gas turbines?
A) Axial Flow Compressor
B) Diaphragm Compressor
C) Scroll Compressor
A
A) Axial Flow Compressor
12
Q
What are the two types of gas turbine compressors?
A) Axial Flow Compressor and Reciprocating Compressor
B) Centrifugal Flow Compressor and Scroll Compressor
C) Centrifugal Flow Compressor and Axial Flow Compressor
A
C) Centrifugal Flow Compressor and Axial Flow Compressor
13
Q
What are the main parts of a centrifugal compressor?
A) Rotor, Stator, and Combustion Chamber
B) Impeller, Diffuser, and Compressor Manifold
C) Nozzle, Turbine, and Exhaust Duct
A
B) Impeller, Diffuser, and Compressor Manifold
14
Q
What is a feature of a single-entry impeller in a centrifugal compressor?
A) Higher speed
B) Smaller diameter
C) Easier ducting
A
C) Easier ducting
15
Q
What is an advantage of a double-entry impeller?
A) Easier maintenance
B) Higher speed and smaller diameter
C) Lower material cost
A
B) Higher speed and smaller diameter
16
Q
What material is typically used for centrifugal compressor impellers?
A) Cast iron
B) Stainless steel
C) Forged aluminium alloy
A
C) Forged aluminium alloy
17
Q
What happens to air as it passes through the impeller in a centrifugal compressor?
A) It is cooled and condensed
B) It is accelerated outward and diffused to raise pressure
C) It is mixed with fuel
A
B) It is accelerated outward and diffused to raise pressure
18
Q
What is the typical pressure rise per stage in a centrifugal compressor?
A) Up to 2:1
B) Up to 5:1
C) Up to 8:1
A
C) Up to 8:1
19
Q
Why are centrifugal compressors typically limited to 2 stages?
A) Noise reduction
B) Efficiency reasons
C) Material constraints
A
B) Efficiency reasons
20
Q
In which types of engines are centrifugal compressors commonly found?
A) Turbojet and Ramjet
B) Turboprop and Turboshaft
C) Afterburner and Pulsejet
A
B) Turboprop and Turboshaft
21
Q
What components make up each stage of an axial flow compressor?
A) One rotor and two stators
B) One stator and one nozzle
C) One rotor and one stator
A
C) One rotor and one stator
22
Q
Why does the diameter of an axial flow compressor reduce from front to back?
A) To increase temperature
B) To maintain steady axial velocity
C) To reduce engine weight
A
B) To maintain steady axial velocity
23
Q
What type of airflow occurs in an axial flow compressor?
A) Spiral path
B) Turning flow
C) Straight path
A
C) Straight path
24
Q
What is the compression ratio per stage in an axial flow compressor?
A) 1:5 to 1:6
B) 1:1 to 1:2
C) 2:1 to 3:1
A
B) 1:1 to 1:2
25
How is high overall compression achieved in an axial flow compressor?
A) Using a single large rotor
B) By combining centrifugal and axial stages
C) By using many rotor-stator stages
C) By using many rotor-stator stages
26
What helps improve efficiency and avoid stall in axial flow compressors?
A) Increasing fan size
B) Cooling the airflow
C) Careful stage design
C) Careful stage design
27
Which type of engine commonly uses axial flow compressors?
A) Turboprop
B) Turbofan
C) Ramjet
B) Turbofan
28
What is a common feature found at the front of modern axial flow compressors?
A) Afterburner
B) Exhaust nozzle
C) Fan
C) Fan
29
What type of spool configurations can axial flow compressors have?
A) Single or dual only
B) Single, dual, or triple
C) Triple only
B) Single, dual, or triple
30
What is an advantage of a centrifugal compressor?
A) High starting power needs
B) Large frontal area
C) High pressure rise per stage
C) High pressure rise per stage
31
Why is a centrifugal compressor considered cost-effective?
A) Complex multi-stage design
B) Simple, low-cost construction
C) Expensive materials
B) Simple, low-cost construction
32
What is a disadvantage of a centrifugal compressor?
A) Lightweight design
B) Large frontal area
C) High efficiency in stage turns
B) Large frontal area
33
How does a centrifugal compressor perform across different rotational speeds?
A) Poorly at high speeds
B) Efficient across a wide range
C) Only efficient at constant speed
B) Efficient across a wide range
34
Which of the following is a disadvantage of centrifugal compressors?
A) Low starting power needs
B) Efficiency loss in turns between stages
C) Compact frontal area
B) Efficiency loss in turns between stages
35
What is an advantage of an axial compressor?
A) High peak efficiency
B) Large frontal area
C) Low pressure rise per stage
A) High peak efficiency
36
Why is an axial compressor considered compact?
A) It has a small frontal area for given airflow
B) It uses fewer materials
C) It has a single stage
A) It has a small frontal area for given airflow
37
How can pressure be increased in an axial compressor?
A) By increasing rotor speed only
B) By adding more stages with minimal losses
C) By using a larger impeller
B) By adding more stages with minimal losses
38
What is a disadvantage of an axial compressor?
A) Efficient over a wide speed range
B) Requires low starting power
C) Complex and expensive to manufacture
C) Complex and expensive to manufacture
39
What limits the efficiency of an axial compressor?
A) Efficiency only over a narrow speed range
B) Large size
C) Simple construction
A) Efficiency only over a narrow speed range
40
What design helps mitigate the high starting power required by axial compressors?
A) Using split or multi-spool compressors
B) Using centrifugal compressors instead
C) Reducing the number of stages
A) Using split or multi-spool compressors
41
What are the main components of a centrifugal compressor?
A) Rotor, combustion chamber, and exhaust
B) Impeller, diffuser, and compressor manifold
C) Fan, nozzle, and turbine
B) Impeller, diffuser, and compressor manifold
42
What is the typical pressure rise per stage in a centrifugal compressor?
A) About 2:1
B) About 8:1
C) About 12:1
B) About 8:1
43
Why are centrifugal compressors typically limited to two stages?
A) Due to weight concerns
B) Due to efficiency concerns
C) Due to cost constraints
B) Due to efficiency concerns
44
What material is the impeller in a centrifugal compressor usually made from?
A) Cast iron
B) Forged aluminium alloy
C) Titanium
B) Forged aluminium alloy
45
What is a characteristic of a single-entry impeller?
A) Smaller diameter, higher speed
B) Easier ducting
C) Higher pressure ratio
B) Easier ducting
46
What advantage does a double-entry impeller have over a single-entry impeller?
A) Easier maintenance
B) Smaller diameter and higher speed operation
C) Lower cost
B) Smaller diameter and higher speed operation
47
In which types of engines are centrifugal compressors commonly used?
A) Turboprop and turboshaft engines
B) Turbojet and ramjet engines
C) Turbofan engines only
A) Turboprop and turboshaft engines
48
What components make up the stages of an axial flow compressor?
A) Rotors with aerofoil blades and stators (stationary vanes)
B) Impellers and diffusers
C) Fans and nozzles
A) Rotors with aerofoil blades and stators (stationary vanes)
49
How does air flow through an axial flow compressor?
A) It flows straight through with no directional turns
B) It spirals through the compressor
C) It reverses direction before exiting
A) It flows straight through with no directional turns
50
Why does the diameter of an axial flow compressor decrease from front to back?
A) To increase temperature
B) To maintain steady axial velocity
C) To reduce weight
B) To maintain steady axial velocity
51
What spool configurations can axial flow compressors have?
A) Single-spool only
B) Single-spool or multi-spool (dual/triple)
C) Multi-spool only
B) Single-spool or multi-spool (dual/triple)
52
What component is often included at the front of axial flow compressors?
A) Afterburner
B) Fan
C) Diffuser
B) Fan
53
In which type of engines are axial flow compressors widely used?
A) Turbofan engines
B) Reciprocating engines
C) Rocket engines
A) Turbofan engines
54
What role do rotors play in compressor operation?
A) Diffuse the airflow
B) Accelerate the air
C) Correct the airflow angle
B) Accelerate the air
55
What is the typical compression ratio per stage in a compressor?
A) 1:1 to 1:2
B) 2:1 to 3:1
C) 4:1 to 5:1
A) 1:1 to 1:2
56
Why are many stages required in a compressor?
A) To increase airflow speed
B) To achieve high overall compression
C) To reduce weight
B) To achieve high overall compression
57
What function do stators serve in a compressor?
A) Accelerate the air
B) Provide fuel to the combustion chamber
C) Correct airflow angle to prevent stall
C) Correct airflow angle to prevent stall
58
What is the role of fans in multi-spool engines?
A) Provide high-pressure compression
B) Provide low-pressure compression and handle bypass flow
C) Reduce engine noise
B) Provide low-pressure compression and handle bypass flow
59
What is an advantage of centrifugal compressors?
A) High starting power requirement
B) Large frontal area
C) High pressure rise per stage
C) High pressure rise per stage
60
Which of the following is a disadvantage of centrifugal compressors?
A) Low starting power requirement
B) Losses in airflow turns between stages
C) Small frontal area
B) Losses in airflow turns between stages
61
What is an advantage of axial compressors?
A) High peak efficiency
B) Simple, low-cost construction
C) Efficient over wide speed range
A) High peak efficiency
62
What limits the efficiency of axial compressors?
A) Efficiency only in narrow speed range
B) Low peak efficiency
C) Large frontal area
A) Efficiency only in narrow speed range
63
Which compressor type typically has a small frontal area?
A) Centrifugal compressor
B) Axial compressor
C) Reciprocating compressor
B) Axial compressor
64
What is a disadvantage of axial compressors?
A) Low manufacturing cost
B) High starting power requirement
C) Simple design
B) High starting power requirement
65
Which rotating assembly components can be balanced without engine disassembly?
A) Compressor blades
B) Fan blades
C) Turbine blades
B) Fan blades
66
Why do high-bypass fans need special attention during balancing?
A) Because of their complex shape
B) Due to large diameter and high rotational forces
C) Because they rotate slower than other parts
B) Due to large diameter and high rotational forces
67
What can even minor damage to rotating assemblies cause?
A) Increased fuel efficiency
B) Imbalance affecting rotating assembly and bearings
C) Reduced noise levels
B) Imbalance affecting rotating assembly and bearings
68
What is required for all rotating assemblies in turbine engines?
A) Regular lubrication
B) Balancing
C) Cooling
B) Balancing
69
When does a rotor run vibration-free according to fan blade balance principles?
A) When all blades have the same color
B) When opposite fan blades create identical centrifugal forces
C) When the rotor speed is constant
B) When opposite fan blades create identical centrifugal forces
70
Which factors affect the centrifugal force on a fan blade?
A) Blade color and material
B) Rotor speed, blade mass, and distance of blade’s center of gravity from rotation axis
C) Blade length and width only
B) Rotor speed, blade mass, and distance of blade’s center of gravity from rotation axis
71
How is moment weight calculated in fan blade balance?
A) Blade mass divided by rotor speed
B) Blade mass multiplied by distance of CG from rotational axis
C) Rotor speed multiplied by blade length
B) Blade mass multiplied by distance of CG from rotational axis
72
What causes moment weight to vary between fan blades?
A) Manufacturing tolerances affecting center of gravity position
B) Different blade colors
C) Variation in rotor speed
A) Manufacturing tolerances affecting center of gravity position
73
What units can moment weight be measured in?
A) Gram-inches, cm.g, or ounce-inches
B) Pounds only
C) Newtons and meters
A) Gram-inches, cm.g, or ounce-inches
74
Where is the moment weight marked on a fan blade?
A) On the blade tip
B) On the fan blade root alongside part and serial numbers
C) On the compressor casing
B) On the fan blade root alongside part and serial numbers
75
What happens if a fan blade is blended or modified?
A) It is discarded
B) Original moment weight is crossed out and new weight is marked
C) No changes are made to the moment weight
B) Original moment weight is crossed out and new weight is marked
76
How are fan blades matched for optimal balance in computerized fan blade distribution?
A) By weight only
B) By color coding
C) Each blade’s moment weight is matched by computer
C) Each blade’s moment weight is matched by computer
77
How are fan blades numbered and identified on the disc?
A) Randomly
B) Usually in direction of rotation with index marks or offset holes
C) By blade length only
B) Usually in direction of rotation with index marks or offset holes
78
What is done when replacing a single fan blade with a moment weight close to the original?
A) The entire fan disc must be balanced
B) No further balancing is needed
C) Replace the opposite blade as well
B) No further balancing is needed
79
What action is required if the moment weight difference is large during single blade replacement?
A) Add balance weights on the fan disc or spinner cone
B) Replace all blades
C) No action needed
A) Add balance weights on the fan disc or spinner cone
80
What is the paired blade replacement method?
A) Replace any two random blades
B) Replace damaged blade and the blade opposite it together
C) Replace the largest and smallest blades
B) Replace damaged blade and the blade opposite it together
81
What is the purpose of balance weights in fan blade replacement?
A) To increase rotor speed
B) To compensate for moment weight differences
C) To reduce blade size
B) To compensate for moment weight differences
82
Where are balance weights positioned?
A) On the engine casing
B) On the fan disc or spinner cone
C) On the compressor blades
B) On the fan disc or spinner cone
83
What happens when the angle of attack on compressor rotor blades increases due to a decrease in inlet air velocity?
A) Airflow accelerates smoothly
B) Airflow separates from the compressor aerofoils causing a turbulent vortex
C) Compressor blades rotate faster
B) Airflow separates from the compressor aerofoils causing a turbulent vortex
84
What is compressor surge?
A) A mild form of compressor stall
B) A rapid decrease in rotor speed without airflow changes
C) A very severe form of compressor stall causing airflow to stop and reverse
C) A very severe form of compressor stall causing airflow to stop and reverse
85
Which component damage can cause compressor stall?
A) Dents or ice on engine inlet
B) Damaged rotor blades or stator vanes
C) Both A and B
C) Both A and B
86
Why are axial and centrifugal compressors sensitive to airflow changes?
A) They have multiple optimum operating conditions
B) They have only one optimum operating condition for a given pressure ratio, speed, and airflow
C) They operate only at low speeds
B) They have only one optimum operating condition for a given pressure ratio, speed, and airflow
87
Which condition can cause compressor stall during engine operation?
A) Engine speed too far below design speed
B) Incorrect acceleration or deceleration
C) Both A and B
C) Both A and B
88
What role do the stator vanes play in axial compressors?
A) Accelerate the airflow and increase velocity
B) Decelerate the airflow and guide it to the next rotor stage
C) Reverse the airflow direction
B) Decelerate the airflow and guide it to the next rotor stage
89
Surge in the aft compressor stages is more dangerous because:
A) The blades are larger and slower
B) It develops rapidly over a large part of the compressor with high pressure and short blades
C) It affects only a small number of blades
B) It develops rapidly over a large part of the compressor with high pressure and short blades
90
What happens to airflow during compressor stall?
A) Airflow remains steady and smooth
B) Airflow slows down, stops, or reverses direction
C) Airflow speeds up through the compressor
B) Airflow slows down, stops, or reverses direction
91
Which of the following is NOT a method to prevent compressor stall and surge?
A) Compressor bleed valves
B) Dual or triple-spool rotors
C) Fixed compressor stator vanes
C) Fixed compressor stator vanes
92
Where are compressor bleed valves typically located?
A) At the front of the engine only
B) Mid-section and sometimes aft section of the compressor
C) Only in the high-pressure turbine
B) Mid-section and sometimes aft section of the compressor
93
When are compressor bleed valves usually open?
A) At high engine speeds
B) At low engine speeds
C) During engine shutdown
B) At low engine speeds
94
What is the main benefit of splitting the compressor rotor into dual or triple spools?
A) Simplifies the compressor design
B) Allows each rotor to be driven by a separate turbine
C) Reduces engine weight significantly
B) Allows each rotor to be driven by a separate turbine
95
Where are variable stator vanes typically located?
A) In the aft stages of the low-pressure compressor
B) In the forward stages of the high-pressure compressor
C) Only in centrifugal compressors
B) In the forward stages of the high-pressure compressor
96
What is the main advantage of variable stator vanes?
A) Reduce engine noise
B) Achieve optimum angle of attack on rotor blades for every engine speed
C) Lower manufacturing cost
B) Achieve optimum angle of attack on rotor blades for every engine speed
97
What is a disadvantage of variable stator vanes?
A) They are heavy
B) They require a complicated control mechanism
C) They reduce airflow efficiency
B) They require a complicated control mechanism
98
Most modern engines use how many stall prevention methods?
A) One
B) Two or three combined
C) None
B) Two or three combined
99
What does the compression ratio of an internal combustion engine represent?
A) The ratio of fuel to air in the mixture
B) The ratio of the volume of its combustion chamber from largest to smallest capacity
C) The engine’s maximum RPM
B) The ratio of the volume of its combustion chamber from largest to smallest capacity
100
At what condition does a turbine engine compressor produce its given compression ratio?
A) At any random speed and mass flow
B) At the set of conditions where all compressor components operate at optimum effect
C) Only at maximum RPM
B) At the set of conditions where all compressor components operate at optimum effect
101
How does axial velocity of gas change through the compressor?
A) It increases from front to rear
B) It decreases from front to rear
C) It remains constant from front to rear
C) It remains constant from front to rear
102
Why is the compression ratio not proportional to RPM?
A) Because blade angles are fixed and only correct at a certain point
B) Because pressure is constant at all RPMs
C) Because airflow speed is not related to RPM
A) Because blade angles are fixed and only correct at a certain point
103
What is the approximate pressure ratio of each stage in an axial flow compressor?
A) 1.3:1
B) 2:1
C) 5:1
A) 1.3:1
104
If the input pressure to the first stage is 10 psi, what is the output pressure after the second stage with a 1.3:1 ratio per stage?
A) 13 psi
B) 16.9 psi
C) 20 psi
B) 16.9 psi
105
Why are many stages required in an axial flow compressor?
A) Because the pressure increase per stage is very small
B) To reduce engine weight
C) To increase airflow speed only
A) Because the pressure increase per stage is very small
