15.5 - Combustion Section. Flashcards
(11 cards)
What are the 2 ,Ain components of the combustion section.
The flame tube and the combustion chamber casing.
Why is fuel vapouriest
So it mixes with the airflow.
What is the correct air to fuel ratio
15:1
What are the 2 parts that airflow is split into.
Primary is used for the combustion process - 20-30% of flow.
Secondary is used for cooling in mixture and dilution zone.
Can-type combustion chamber.
Found on old gas turbine engines that had centrifugal compressors.
Simple in design, very good structural strength, can be replaced individually.
Difficult ignition from one chamber to the next.
Heavy and needs lots of space.
Complicated air supply ducts.
Can-annular type combustion chamber.
Smaller and lighter than can type.
Aerodynamic losses are quite high.
All flame tubes have a common outer and inner casing.
Ignition is difficult from one can to the next.
Annular type combustion chamber.
Used on modern gas turbine.
Has only one annular flame.
3 major parts: dome, inner liner , outer liner.
Special design for small gas turbine and APU engines - called a reverse flow chamber.
Smaller and lighter.
Better efficiency.
Expensive to manufacture.
Time consuming to remove.
How many igniters are installed on the combustion case.
2 igniters
Normally found on lower half.
What does the dome section of combustion chamber do.
Connects the inner and outer liner, houses the swillers.
Flame tube cooling
Film cooling.
- Uses secondary airflow over liner segments.
Transpiration cooling
- requires less air.
- goes through liner segments.
Methods to reduce emissions
Pollutants are mainly : unburnt fuel; hydrocarbons; carbon monoxide; nitrogen oxides
Excessive fuel supports the build up of carbon monoxide.
Lean mixture can lead to flame out.
Low combustion temps increase carbon monoxide strongly.
High temps decrease CO and hydrocarbons but increases nitrogen oxides
Dual dome chambers = shorter = better = less nitrogen oxides build up.
