M15.5 Combustion Section Flashcards
Combustion chamber main components
- combustion chamber casing
- Flame tube
Functions of combustion for safe flight
- Safe ignition (Ground and air)
- Stable ops
- Complete combustion
When are the igniter plugs switched off
After ignition
Kerosine-air mixture ratio
1:15 (K to A)
How much of the compressor air is used for primary combustion
20-30%
What is secondary air used for
- Cooling
- Flame control
How does secondary air enter the dilution zone
Dilution air holes
Low or high velocity for combustion
Low
What should the air velocity be for combustion or kerosine-air mixtures
2-15 m/s
Types of combustion chamber
- Can
- Can-annular
- Annular
What combustion chamber is used on engines with centrifugal compressors
Can type
How is ignition transferred in can type combustion chambers
Interconnector tubes
What do the interconnector tubes do
- Transfer ignition
- Equalise pressurisation
Advantages of can type
- Simple
- Good strength
- Replaced individually
Disadvantage of can type combustion
Heavy and need space
What is the common part in a can annular combustion chamber
Common outer ring and inner casing
Advantage of can-annular combustion
- Smaller than multiple can type
- Good strength
Disadvantage of can-annular combustion
- High aerodynamic losses
- Ignition can be hard to pass
Advantages of annular chambers
- Small but light
- Better efficiency
- Better thermal distribution
- Smokeless
Disadvantage of annular chambers
Expensive and difficult to remove
An increase in combustion temp will do what to carbon monoxide and nitrogen oxide emissions
- Decrease carbon monoxide
- Increase Nitrogen Oxide
Apart from fuel mixture how can emissions be lowered
Dual zone combustion chambers
What is in front of the inner wall flange
Seal surface of the CDP (Compressor Discharge Seal)
What is film cooling
Secondary airflow is used to cool the inner surface of the liners
What type of flame tube cooling is used on modern engines
Machined cooling rings
What type of flame tube cooling is used on older engines
- Corrugated Strip Cooling
- Splash cooling strip
What is the most sophisticated type of flame tube cooling
Transpiration cooling method
