What is the main function of a jet engine combustion chamber?
To raise the temperature of compressed air by burning fuel, releasing energy to drive the turbine.
Key design requirements of a combustion chamber?
Safe ignition, stable and complete combustion, even temperature distribution, minimal pressure loss, lightweight, effective cooling, long service life.
What is the combustion chamber casing?
The outer structure that supports the flame tube, fuel nozzles, igniters, and withstands pressure and heat.
What is the flame tube?
A segmented inner structure that guides the flame and supports stable combustion.
What happens to air and fuel during combustion?
Compressed air enters, fuel is injected and vaporised, ignited, and combustion continues with continuous air and fuel supply.
Typical air-fuel ratio for jet engine combustion?
Approximately 15:1.
How is airflow divided in the combustion chamber?
Primary airflow (20–30%) for combustion and secondary airflow for cooling and mixing.
Purpose of primary airflow?
Supports and sustains combustion.
Purpose of secondary airflow?
Cools hot gases and mixes to reduce temperature before turbine.
What is a can-type combustion chamber?
Individual combustion chambers, each with its own fuel nozzle and flame tube.
Advantages of can-type chambers?
Simple, strong, and individually replaceable.
Disadvantages of can-type chambers?
Heavy, bulky, complex ducting, difficult cross-chamber ignition.
What is a can-annular combustion chamber?
Multiple flame tubes housed in a common casing.
Advantages of can-annular chambers?
Lighter and smaller than can-type.
Disadvantages of can-annular chambers?
Aerodynamic losses and difficult ignition between tubes.
What is an annular combustion chamber?
A single continuous annular flame tube used in modern engines.
Advantages of annular chambers?
Compact, efficient, complete combustion, even flame spread.
Disadvantages of annular chambers?
Expensive and difficult to remove or maintain.
What is a reverse-flow annular combustion chamber?
A chamber where airflow in the flame tube is opposite to engine airflow, used in small engines/APUs.
Main parts of the combustion case?
Inner and outer walls, diffuser, flame tube supports, fuel nozzle pads, igniter bosses.
Main parts of the flame tube?
Dome, inner and outer liners, cowls, swirlers.
How is cooling achieved in combustion chambers?
Secondary airflow creates a film cooling layer along the liner.
What is transpiration cooling?
Advanced cooling using liner tiles that allow air to pass through small holes.
Main combustion chamber pollutants?
Unburned fuel, hydrocarbons, carbon monoxide (CO), nitrogen oxides (NOx).
