Gas Turbine - Principles

Question 1

Turbo Fan purpose

Answer 1

Accelerate very large mass of air rearward at a slow speed

Question 2

Flat Rating

Answer 2

Limiting the thrust via fuel flow at colder temperatures below ISA

Question 3

Factors impacting thrust

Answer 3

Altitude - reduces with height
Speed - increases with ram effect
Ambient temp - high temp reduces
Engine bleed - reduces mass flow and thrust

Intake heating - reduce air density and mass flow

Question 4

Pressure Thrust Formula

Answer 4

Area of propelling nozzle x (exhaust static p - inlet static p)

Question 5

Propulsive Efficiency at low speed

Answer 5

Propeller and fans more efficient at low speed as less wasted energy

Question 6

Auxiliary gearbox

Answer 6

Driven by HP compressor via internal gearbox to an external gearbox

Question 7

Secondary (supplementary) gearbox is driven by

Answer 7

LP compressor shaft operating a lower speed to share load of the accessory units

Question 8

Brayton Cycle

Answer 8

Compression/Combustion/Expansion and exhaust
Happens continuous

Question 9

Specific Fuel Consumption Varies with

Answer 9

Temperature - if temperature increase SFC increases

Question 10

Why do large engines need a spool up time

Answer 10

Over rich mixture might cause flameout

Question 11

Start Sequence of gas turbine

Answer 11

Starter
Rotation
Ignition On
Fuel On
Light up
Self sustaining speed
Starter off
Acceleration to idle