GT

Question 1

Describe Primary air

Answer 1

• 15% of the total air
• It is the air used for intial combustion and helps atomise the fuel

Question 2

Describe Secondary air

Answer 2

• 10% of the total airflow
• It ensures that all fuel has been burnt
• and provides a layer of air between the fuel and flame tube ,preventing flame impingement

Question 3

Describe Tertiary air

Answer 3

• The remaining 75% of air
• heated up by thecombustion process and is the working fluid in the GT

Question 4

Describe GT fuel injector (Burner)

Answer 4

Injects atomised fuel into the combustion chamber in a fine mist meaning the fuel more efficiently mixes with the air

Question 5

Describe GT ingniter

Answer 5

• Produces 2000V spark that ignites atomised fuel, starting the engine
• De-energises once engine is running

Question 6

Describe LP Compressor (GT)

Answer 6

• The first part air goes through in the GT
• Rotating blades compress the air as it is drawn through the rotating blades
• It is an axial flow pump

Question 7

Describe HP Compressor (GT)

Answer 7

• Rotating blades slow down the air to increase it’s pressure again by a ratio of 19:1

Question 8

Describe Combustion Chamber

Answer 8

• Where the atomised fuel and compressed air. is ingnited
• Most air entering the combstion chamber is used to cool the chamber,then is burnt further down once flame has been established.
• Designed to give maximum power in the smallest space with minimum losses

Question 9

Describe LP & HP Turbines

Answer 9

• Hot gases leave the combustion chamber and drive the turbines
• The turbines in turn drive the compressors, making the engine self sustaining
• Turbines are connected to the compressors by a shaft within a shaft
• 1/3 of the energy from combustion is lost at this stage

Question 10

GT operate on what principle?

Answer 10

• Brayton cycle ( thermodynamics)
• It describes the operation of engines that have air or gas as thier working fluid

Question 11

Describe Power turbine

Answer 11

The power turbine drives the input shaft of the gearbox,which drives the propeller shaft

Question 12

Describe GT Lubrication system

Answer 12

• Oil is sent to the turbine & comp shaft by a gear wheel pump
• It is called a scavenge system
• It incorperates mag chips that collect ferrous metal from the GT
• Checked every 24hrs for debris

Question 13

What is flame impingment?

Answer 13

when a flame actually touches or engulfs the tubes causing hot spots

Question 14

What is an axial flow pump?

Answer 14

common type of pump consists of a propeller (an axial impeller) in a pipe

Question 15

Why does air heat when compressed?

Answer 15

When in a big open space, they don’t hit each other very often. Up in the higher atmosphere, where the air is thin, they barely do, so it’s very cold. But when you compress air, the molecules are forced into closer quarters. They colide and interact with each other more and more, increasing the heat

Question 16

What is axial thrust?

Answer 16

A propelling force applied along the axis (imaginary straight line through the center of something that is spinning)

Question 17

What does working fluid mean?

Answer 17

A gas or liquid that primarily transfers force, motion, or mechanical energy.

Question 18

Why does a GT need the combustion process to work?

Answer 18

• The hot gases turn the turbines ,which turn the compressers drawing more air in to continue process
• Needs the energy from the gases to overcome friction on the turbines

Question 19

What is the engine intake flare?

Answer 19

Seals the engine intake from the module its in

Question 20

GT safety devices

Answer 20

• Hand trip-shuts off fuel
• Power turbine entry temp-Governor monitors the temp & controls the amount of fuel,will trip if the engine temps exceed safe
• Partial overspeed-If engine overspeeds this device will reduce fuel supplied
• Vibration monitor

Question 21

BTM & BCF Module drenching system

Answer 21

• Fire alarms in the module sound an alarm in the SCC.
• From the SCC you can extinguish fire using chemical BCF or BTM sprayed into module
• Vent flaps must be closed