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30 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Explain the main difference and advantage of turbofan over turbojet engines. |
A turbofan engine uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides additional thrust without increasing fuel flow. |
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Name the major components in a gas turbine engine. |
Air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox and accessory section. |
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What determines the amount of airflow through a turbine engine? |
The forward speed of the aircraft, compressor speed, and air density. |
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Name the two types of compressors commonly used in turbine engines. |
Axial and centrifugal flow compressors. |
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Name two different methods for attaching turbine engine rotor blades to the rotor disks. |
Dovetail type root, Bulb type root, Fir tree type root. |
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What is a split compressor system? |
Also called dual or twin spool compressors, these are connected to the turbine section with two rotor shafts, one inside the other. |
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What are the different types of combustion chambers used in turbine engines? |
Can, annular, can-annular, and reverse flow angular |
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What prevents the combustion chambers from burning? |
Louvers are provided along the axial length of the liners to direct a cooling layer of air along the inside of the liner. |
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What is the purpose of the interconnecting tubes attached between can-type combustion chambers? |
For flame propagation during start. To spread the flame to the combustion chambers that are not equipped with igniter plugs during engine start. |
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What functions do Axial flow turbine nozzles perform? |
They direct the combustion mass airflow to drive the turbine rotor at a specific angle. First they change a portion of the heat and pressure energy to velocity energy. The fixed vanes are shaped and set at such an angle that they form a number small nozzles that discharge the gases at extremely high speeds. The second purpose of the turbine nozzle is to deflect the gases so they strike the turbine at the most efficient angle for maximum turbine rotation. |
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How is thermal stress relieved on a Turbine disc? |
By directing a bleed air onto the face of the disk, or by grooves being cut in the disk. |
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What are carbon seals use for in turbine engines? |
They are used as oil seals for the rotor shaft bearings. |
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What is shaft horsepower? |
It is an indication of the torque developed by a turbo prop or turbo shaft engine. |
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What is the purpose of an APU? |
They provide ground electrical and pneumatic power for aircraft systems when the engines are not running. Pneumatic power can be used for engine starting, ground heating or air conditioning, and anti-icing. Many APU’s may also be used as an emergency source of in-flight electrical power. |
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Name the main components of a typical APU. |
A small power turbine for power and bleed air, and an electrical generator. |
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When is the greatest demand place on an APU? |
When supplying bleed air. |
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How is an APU generally started? |
With its own electrical starter and battery power. |
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Where does the APU get his fuel supply? |
From one of the Aircraft’s main fuel tanks. |
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At what speed does a gas turbine APU operate and how is this speed maintained? |
At or near it’s rated speed regardless of electrical or pneumatic loads imposted. The APU fuel control automatically adjust the fuel flow to maintain the rated speed. |
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What is used to prevent a heavily loaded APU from exceeding its maximum EGT? |
A load control valve modulates the pneumatic load to maintain EGT’s within limits. |
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How is an APU shut down and why is this procedure used? |
After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period Is typically three minutes. If a heavily loaded APU is abruptly shut down without any cooling down period, damage could occur as a result of thermal shock. |
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What powers the variable and inlet guide vanes used on some APU’s to regulate compressor intake airflow? |
Fuel pressure. |
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What is the location and function of the diffuser section in a turbine engine? |
The diffuser is the divergent section of the engine located between the compressor section and burner cans. It’s function is to change the high velocity compressor discharge air to static pressure. |
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Where are stressed rupture cracks most likely to occur on turbine blades? |
They usually appear as small hairline cracks on or across the leading or trailing edge of the blade. The cracks appear at right angles to the edge length. |
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How are compressor blades attached to a disk type rotor? |
The compressor blades I fitted into the disks by either Bulb-type, fir-tree or dove tail type roots. The blades are then locked by means of screws, peening, locking wires, pins, or keys. |
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What is the major difference between turbo prop and turbo jet engines? |
Turbo prop engine usually has more turbine stages then the turbo jet engine. In addition to operating the compressor and accessories, the turbo prop turbine must also drive a propeller. |
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What is the effect of air density on the thrust of a turbine engine? |
Air density determines the mass of air that is used by a jet engine. The factors that affect density are the temperature and pressure of the air. If density increases, thrust increases, and vice versa. An increase in air temperature entering an engine will cause a decrease in air density and thrust. An increase in air pressure entering the engine will cause an increase in air density and thrust. With the given throttle setting, engine thrust will vary if the temperature or pressure of the air entering the engine changes. |
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What are the two most common types of thrust reverse? |
They are mechanical blockage type and aerodynamic blockage type. |
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What is a free turbine? |
A turbine wheel that, rather than driving the compressor rotor, drives a propeller or helicopter transmission. |
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What is the main purpose of thrust reverser’s? |
For slowing the Aircraft down to effective braking speed’s. |
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