15.15 - Power Augmentation Flashcards
What are the two methods of thrust augmentation?
Afterburning system
Water/methanol injection system
What is fitted to an afterburner jet pipe to reduce thermal and vibratory stresses?
An internal shield (screech liner)
What happens to a variable area final nozzle when afterburning takes place?
It becomes larger to prevent back pressure
What are the three ways of igniting the fuel in the exit nozzle?
Spark ignition (similar to normal combustion) Hot shot ignition (split system, fuel sprayed into combustion chamber and split off to exhaust) Catalytic ignition (flash point is lowered due to platinum/rhodium element) and ignited
When will afterburning be available?
When the throttles are advanced enough forward (passed the ‘dry’ position)
What is the purpose of water injection?
Injected into the inlet, it cools the inlet air and increase its density. The water also cools the turbine components.
This is used in adverse conditions (hot/high)
How much can take-off thrust be increased by water injection?
10-30% increase
What is the purpose of adding methanol to the water injection?
Anti-freeze properties
Only fuel that will mix completely with water
Where should a water/methanol system be injected in an axial flow engine?
The combustion chamber inlet so a more even distribution can be obtained and satisfactory coolant
What is the typical mixture percentage of methyl/ethyl and water?
35-50%
Where should the water methanol be injected in a axial flow compressor engine?
The compressor inlet or burner section
