15.5* Flashcards
What components comprise the combustion section?
The casing and the flame tube
How is the flame tube protected from the extreme temperatures of combustion?
By using the secondary air flow
What will hotspots on the flame tube indicate?
The cooling airflow is not correct or the ceramic lining is damaged?
What percentage of air from compressor is used for combustion?
20-30%
What percentage of air from compressor is used for cooling?
70-80%
How are the zones in the combustion chambers identified?
The primary zone and the secondary (dilution) zone
What cooling methods are employed on combustion liners?
Film cooling and transpiration cooling
What is the required fuel/air ratio for optimal combustion?
1:15
What are the advantages of an annular combustion chamber?
Better thermal load distribution, better flame propagation, more complete combustion, more efficient, smaller and lighter
Why is a flame tube only secured at one end?
Thermal expansion
What is the purpose of the diffuser?
It reduces the velocity of airflow coming from the compressor
What two conditions must be met for efficient combustion?
The fuel/air ratio must be correct and the velocity of the air must be slow enough to ensure combustion takes place in the combustion chamber
What is the purpose of the combustion case?
They are part of the load carrying structure of the engine, it protects engine parts from excess heat and provides mounts for combustion chamber components
