COMBUSTION Flashcards
What is the function of a combustion chamber?
Produce a hot stream of gas for turbines and the jet nozzle.
(Continuous combustion of fuel/air mixture)
Why should the combustion have minimum pressure loss?
Increase engine efficiency.
What are the 2 main components of a combustion chamber?
- Chamber casing (protects engine parts from hot combustion gases
- Flame tube (controls and guides the flame)
What 2 conditions are essential for correct and safe combustion?
Correct air/fuel mix
Air velocity must be slow enough to make sure combustion is completed inside the chamber.
What ratio of air/kerosene is required for complete combustion?
15 parts of air for 1 part of fuel.
What % of airflow from the compressor goes to the combustion chamber?
20-30%
Primary airflow
What does the secondary airflow from the compressor do?
Bypasses the primary combustion zone and mates with the hot gas in the dilution zone.
(Mainly used for cooling)
What happens in the primary zone?
The flame stabilises.
(Some of secondary air is used to keep the flame away from the flame tube walls)
(Centre of flame can reach 2000 Celsius)
Where can can-type combustion chambers be found?
Old gas turbine engines with centrifugal compressors.
Single or multiple can
What do interconnector tubes do in a can-type combustion chamber?
Permit the ignition from one chamber to another.
Equalise pressure in all combustion chambers.
What is an advantage of can-type combustible chamber?
Simple in design, good structural strength and can be individually removed and replaced.
What is an disadvantage of can-type combustion chamber?
Heavy and need a lot of space.
The ducts lead to high aerodynamic losses.
Difficult ignition from one chamber to another.
What is a can-annular combustion chamber?
Set of flame tubes installed around the combustion section.
What are advantages of a can-annular combustion chamber?
- Structural strength
- Simple air supply
- Smaller and lighter
What are disadvantages of can-annular combustion chamber?
High aerodynamic losses
Ignition from one flame tube to another is difficult.