Turbine 2 - Week 4 - Engine Air (Exam Profile - 6 Questions)
In engine operation, how is the airflow divided?
Primary and tertiary airflow
Primary and secondary airflow
Core and bypass airflow
Thrust and cooling airflow
Which engine type has all air flowing through the core engine?
Turbojet engines
Turbofan engines
Turboprop engines
Turboshaft engines
In turbojet engines, how is the airflow divided?
Divided into Primary and secondary airflow at the combustion chamber
Single airflow throughout the engine
Multiple airflow streams at the exhaust
No division of airflow
What is the primary airflow and secondary airflow used for in turbojet engines?
Primary is used for combustion & secondary is used for cooling
Primary is used for cooling & secondary is used for thrust production
Primary is used for exhaust & secondary is used for cooling
Primary is used for RPM reduction & secondary is used for combustion
What is the primary airflow in a turbofan engine used for?
Primary airflow is the core engine airflow, used for thrust and cooling
Primary airflow is the core engine airflow, provides nacelle cooling
Primary airflow is the bypass airflow, generates most of the engine thrust
Primary airflow is the bypass airflow, provides more equally distributed combustion
What is the secondary air in a turbofan engine primarily used for?
Secondary air is the bypass air used for the production of most of the engine thrust and provides nacelle cooling
Secondary air is the core engine airflow used for the production of most of the engine thrust and provides nacelle cooling
Secondary is the core engine airflow, used for thrust and cooling
Secondary air is the core engine airflow used for increasing fuel efficiency
What percentage of mass airflow through the engine is approximately used for cooling?
25%
50%
75%
100%
Which of the following are areas of the engine that require cooling?
Exterior and interior components of the combustion section, in many cases engine generator is also cooled
Exterior components of the compressor only, in many cases engine generator is also cooled
Exterior and interior components of the compressor, combustion & turbine sections, in many cases the engine generator is also cooled
Interior components of the turbine section only, in many cases engine generator is also cooled
What is the term used to describe exterior (engine case) cooling?
Nacelle cooling
Inlet cooling
Generator cooling
Ram air cooling
What type of air is directed between the engine case and the nacelle to provide cooling and ventilation?
Compressor air, inlet air is also used for generator cooling
Exhaust air, inlet air is also used for generator cooling
Cabin air, inlet air is also used for generator cooling
Ram air (turbojet) or fan air (turbofan), inlet air is also used for generator cooling
The engine compartment is typically divided into two or more sections. These sections are referred to as..?
Zones
Stations
Engine Compartments
Exhaust Systems
What do the seals in exterior engine cooling systems do?
Seals separate the zones (sections) to form barriers, clearing out combustible vapors form areas of high heat and venting them overboard
Seals decrease RPM, reduce potential fire or explosion hazards, increase fuel efficiency and prevent overheating
Seals only reduce potential for leakage
Increase engine power
Hot section internal cooling is NOT provided to which of the following?
Combustion chamber
Turbine NGVs, stators & blades
Turbine discs
Insulation Blankets
What is the primary source of cooling in the combustion chamber?
Secondary compressor discharge airflow
Core airflow
Fuel injection
Exhaust gas
Core airflow used for cooling is down to about how much % on newer combustion chamber designs?
25%
35%
45%
55%
Interior Engine Cooling: How is cooling for turbine NGVs, stators, and blades accomplished?
Various stages of compressor bleed air
Through the use of liquid coolant
By directing exhaust gases to cool the components.
By using external fans to blow air over the components
How is the cooling air directed in Convection (film) cooling?
Directed through the base of hollow blades and exits through the tips, as well as trailing & leading edges
Directed through the leading edges and exits through the trailing edges
Directed through the tips and exits through the base of hollow blades, as well as trailing & leading edges
Directed through the trailing edges and exits through the leading edges
Which of the following is a characteristic of the nozzle vanes used in transpiration cooling?
Nozzle vanes are made of impermeable and low-temp metal, air enters through it
Nozzle vanes are made of a porous and high-temp material, air exits through the material itself
They are made of solid metal and they completely block the airflow
They are made of solid metal and they are made of a low-temp material
Which component in interior engine cooling uses compressor bleed air to cool its front and aft faces?
Turbine discs
Compressor blades
Exhaust nozzle
Combustor
What is the purpose of cooling air in regards to turbine discs?
To maximize temperature imbalances and to increase the heating of the disc rims
To correct temperature imbalances caused by hot gases heating up the disc rims during operation
To provide additional power to the engine
To cool down the interior of the engine compartment
In Active Clearance Control system, what is used to control compressor and turbine blade-to-case clearances to provide optimal airflow during engine operation?
The fuel-to-air ratio
Fan and compressor bleed air
The engine speed
Temperature of the exhaust gases
What does the FADEC operate to control the active clearance control systems?
Valves
Fuel flow
Engine temperature
Electric current
Which of the following is NOT an active clearance control system that FADEC operates?
Rotor active clearance control (RACC)
Low pressure turbine active clearance control (LPTACC or LPTCC)
High pressure turbine active clearance control (HPTACC or HPTCC)
Intermediate pressure turbine active clearance control (IPTACC or IPTCC)
Which of the following statements accurately describes RACC?
Compressor bleed air is routed into the compressor rotor bore to control the clearance between the blade tips and the compressor casing
Active clearance control eliminates the need for compressor bleed air in regulating the clearance between the blade tips and the compressor casing
Compressor bleed air is used to increase the clearance between the blade tips and the compressor casing
Active clearance control is a technique used to enhance the efficiency of the compressor by adjusting the blade angles
Which of the following statements accurately describes LPTACC?
Fan air is directed to a manifold (tubing) that encircles the low pressure turbine case, controlling the LP turbine blades and case clearance
Uses compressor discharge air to maintain proper clearance between the high pressure turbine blades and casing
Compressor bleed air is routed into the compressor rotor bore to control the clearance between the blade tips and the compressor casing
Active clearance control eliminates the need for compressor bleed air in regulating the clearance between the blade tips and the compressor casing
Which of the following statements best describes the purpose of HPTACC?
Uses compressor discharge air to maintain proper clearance between the high pressure turbine blades and casing
Employs compressor discharge air to increase the fuel combustion rate
Utilizes compressor discharge air to cool down the high-pressure turbine blades
Utilizes compressor discharge air for reducing the engine's overall noise level
How does Bearing Compartment Pressurization operate?
Uses compressor bleed air to pressurize engine bearing compartments along the length of the shaft(s)
Injects a specific gas mixture into the compartments, which creates the necessary pressure for the engine bearings
Implements a complex network of fans that blow air into the compartments, maintaining the required pressure
Uses tiny air bubbles to fill up the compartments, creating an air cushion for the engine bearings
What is the primary purpose of bearing compartment pressurization?
To prevent oil leakage past the bearing compartment seals
To ensure proper lubrication of the bearings
To minimize vibration and noise in the bearing compartment
To regulate the temperature within the bearing compartment
Which of the following statements describes one of the purposes of bearing compartment pressurization in relation to pressure balance seals?
It helps to maintain optimal lubrication conditions for the bearings
It prevents the ingress of contaminants into the bearing compartment
It regulates the air temperature inside the bearings
It offsets the aerodynamic axial loads imposed on the bearings, through the use of pressure balance seals
What are bearing compartments more commonly known as?
Bearing cavities or sump
De-oiler or Vent
Drain or scavenge pump
Labyrinth air seal or labyrinth oil seal
What is the purpose of compressor bleed control system?
To minimize the risk of compressor stall and surge
To maximize engine efficiency
To regulate fuel flow
To increase air intake pressure
Which two systems are used to operate the compressor bleed control system?
Compressor bleed valves and variable inlet guide vanes (IGVs) & stators
Compressor bleed valves and variable speed drivetrains
Variable inlet guide vanes (IGVs) & stators and fuel injectors
Compressor bleed valves and ignition systems
How do the compressor bleed control systems operate?
They manually adjust the airflow to ensure ideal engine operating conditions
They function automatically to maintain the ideal airflow for all engine operating conditions (speeds)
They enable the engine to operate at speeds faster than ideal operating conditions
They have no effect on the airflow and engine operating conditions
During start and low power engine conditions, the bleed valves and IGV/stators are in what condition?
Low flow condition (valves open and IGV/stators closed)
Turbulent flow condition (valves constantly opening and closing with IGV/stators partially closed)
Normal flow condition (valves closed and IGV/stators closed)
High flow condition (valves closed and IGV/stators open)
As engine power increases, the bleed valves and IGV/stators are in what condition?
The valves move towards the closed position and the IGV/stators move towards the open position to allow more airflow through the engine
The valves move towards the open position, and the IGV/stators move towards the closed position
Both the valves and the IGV/stators move towards the open position
Both the valves and the IGV/stators move towards the closed position
What is the purpose of the PT6 valve in relation to the compressor bleed control?
To bleed of P2.5 (inter-stage) compressor discharge air at low power settings and progressively close as power is increased
To allow more inter-stage compressor discharge air at high power settings and progressively open as power is increased
To increase the P2.5 compressor discharge air at low power settings
To completely stop the inter-stage compressor discharge air at high power settings
Which type of air in compressor bleed control system is used as the muscle pressure to progressively close the valve as power is increased?
Px air, which is P3 air modified through a metering orifice
Pa air, which is p 2.5 air modified through a metering orifice
Px air, which is a special type of helium gas infused with unicorn essence and sprinkled with fairy dust, modified through a metering orifice
P3 air, which is actually a secret blend of oxygen and nitrogen extracted from Mount Everest, modified through a metering orifice
In the lower power range of the compressor bleed control system, what does the P2.5 air do?
P2.5 air forces the valve open, while increasing Px pressure moves the valve towards the closed position as power is increased
P2.5 air forces the valve closed, while increasing Px pressure moves the valve towards the open position as power is increased
P2.5 air has no effect on the valve position, while increasing Px pressure moves the valve towards the closed position as power is increased
P2.5 air forces the valve open, while increasing Px pressure has no effect on the valve position as power is increased
Which of the following correctly describes the primary function of engine (compressor) bleed air?
To pressurize the engine during operation
To pressurize the cabin for passengers' comfort
To service engine and airframe systems
To generate electrical power for onboard systems
Which of the following is NOT an engine system that uses engine compressor bleed air?
Thrust reversers
Engine anti-ice
Engine x-bleed (pneumatic) starting
Thrust vectoring
Which of the following is NOT an airframe system that uses engine compressor bleed air?
Hydraulic reservoir pressurization & air-driven hydraulic pumps
Environmental control system & cabin pressurization
Aircraft anti-ice & windshield heat
Landing gear extension/retraction system
Why is external air used to ventilate the core engine zone?
Aids in the production of thrust
It provides a barrier between the engine case and cowlings for noise suppression
Provides breather air for the oil system
To remove heat & vapors that could potentially ignite
Which type of turbine cooling system consists of porous blades that “breathe” to provide an exit for cooling air?
Convection cooling
Transpiration cooling
Heat-sink transfer cooling
Inverse bio-directional cooling
What is a common term for a bearing chamber?
Sump
Bearing pump assembly
Internal gearbox
Reciprocating chamber
What ATA chapter is Engine Air?
75
77
76
74
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