M15.5 Combustion Section Flashcards
What 3 requirements must a combustion chamber fulfil?
Permit safe ignition of the fuel air mixture on both ground and flight
Give stable combustion in all operating conditions of the engine
Combustion must also be complete. No unburnt fuel should leave chamber
Each combustion chamber has what two main components?
The combustion chamber casing
The flame tube found inside the casing
The combustion chamber casing can be split into what?
Inner and outer casing
What does the combustion casing provide?
Takes air pressure loads
Protects the internal and external engine parts from hot combustion gases.
What does the flame tube do?
Controls and guides the flame.
Made up of many segments with a lot of holes and slots
How is fuel-air mixture ignited?
Electrically ignited by igniter plug
After ignition what happens to ignition?
Ignition will be switched off
What two conditions must be met for safe combustion?
The ratio of air and fuel must be correct.
The air velocity must be slow enough to make sure that the combustion is completed inside the combustion chamber.
For correct combustion of kerosine-air mixture what ratio must be used?
15 part air to one part fuel
Three types of combustion chambers?
Can type
Can annular
Annular
Advantage of can type combustion chambers?
simple in design, they have very good structural strength and they can be removed and replaced individually.
Disadvantage of can type combustion chamber?
heavy and need a lot of space, they also need complicated air supply ducts from the compressor.
A typical annular combustion chamber has what three components?
Combustion case
Flame tube
External components fitted to wall
Three components of combustion case?
Inner wall
Outer wall
Diffuser
The rear flange of the inner wall is used to attach what to what?
the nozzle guide vanes to the high-pressure turbine and support the flame tube.
What is in front of the inner wall flange?
sealing surface of the Compressor Discharge Pressure (CDP) seal.
What are the stator vanes known as at the rear of the high pressure compressor?
Exit guide vanes
What are the openings used for on the outer wall?
Bleed air from high pressure compressor is fed to the aircraft’s pneumatic system
What is found on the outer wall of combustion chamber?
Openings
Fuel nozzle pads
Igniter bosses
Three components of flame tube?
Outer and inner liner
Outer and inner cowl
Dome
What is the dome section used for?
Connects inner liner with outer liner
Houses swirlers with swirl vanes
Why would a flame tube be fixed at the front end of combustion case?
Leaves it free to expand at the rear
The dome is centred in the combustion chamber by what?
Mounting pins
What can the secondary airflow form?
A cooling film on inner surface of the liners
Air fuel mixture burns best at what ratio?
15:1
What is a rich mixture?
Too much fuel for the primary air. Some fuel can’t be burnt and is released to the exhaust
A lean mixture causes what?
Less pollution
But flame can go out
Low combustion temperatures increase what?
Carbon monoxide emissions
