M15.5 Combustion Section Flashcards
What is the primary function of the combustion section in an engine?
To raise the temperature of the air passing through the engine and release energy from the air/fuel mixture
What are the key requirements for the combustion chamber?
- Safe ignition of the fuel-air mixture
- Stable combustion in all operating conditions
- Complete combustion
- Equal temperature distribution at outlet
- Minimum pressure loss
- Small and light design
- Dependable cooling system
- High operating lifetime
What are the two main components of a combustion chamber?
- Combustion chamber casing
- Flame tube
What is the role of the combustion chamber casing?
To take air pressure loads and protect engine parts from hot combustion gases
How does the flame tube function in the combustion chamber?
It controls and guides the flame and is made up of many segments with holes and slots
What is the process of combustion in the chamber?
Compressed air enters, fuel is injected, vaporizes, mixes with air, and is ignited by an igniter plug
What are the two primary airflows in the combustion process?
- Primary airflow
- Secondary airflow
What is the typical air-to-fuel ratio required for complete combustion of kerosene?
15 parts of air for 1 part of fuel
What are the three types of combustion chambers used in gas turbine engines?
- Can-type combustion chamber
- Can-annular combustion chamber
- Annular combustion chamber
What is a key advantage of can-type combustion chambers?
They are simple in design and can be removed and replaced individually
What is a disadvantage of can-type combustion chambers?
They are heavy and need complicated air supply ducts
What is a key advantage of can-annular combustion chambers?
They are smaller and lighter than multiple-can combustion chambers
What is a disadvantage of can-annular combustion chambers?
They experience high aerodynamic losses and difficult ignition between flame tubes
What is unique about annular combustion chambers?
They have one annular flame tube supported by inner and outer casings
What are the three major parts of an annular combustion chamber?
- Dome
- Inner liner
- Outer liner
What is the purpose of the dome in an annular combustion chamber?
To connect the inner liner with the outer liner and house the swirl vanes
What is film cooling in the context of flame tube cooling?
A method where secondary airflow forms a cooling film on the inner surface of the liners
What is transpiration cooling?
A more sophisticated cooling method requiring less air where inner surfaces are covered with detachable tiles
What are the main pollutants in exhaust gas from gas turbine engines?
- Unburned fuel
- Hydrocarbons
- Carbon monoxide
- Nitrogen oxides
What happens if the air-fuel mixture is too rich?
Some fuel cannot be burned and is released into the exhaust, increasing carbon monoxide emissions
What is the effect of increasing combustion temperature on emissions?
Decreases carbon monoxide and hydrocarbon emissions but increases nitrogen oxide emissions
What is a dual dome combustion chamber?
A shorter combustion chamber that reduces the time exhaust gas is in the hot area, decreasing nitrogen oxides
