Combustion Chambers Flashcards
What is the general operation of a combustion chamber?
The compressor supplies an extensive volume of air The Spray nozzle supplies fuel Igniters for starting and relighting Burns large quantities of fuel A continuous flame exist Extreme heat is released Gas is expanded and accelerated.
What is the purpose of swirl vanes?
Provide a whirl to the airflow in the opposite to the fuel spray cone to enhance mixing
Explain the primary combustion zone?
A small proportion of the total airflow (20%) enters at the snout to mix with the atomized fuel which is introduced at the burner nozzle. Of this 20% half passes through the swirl vanes to give the air fuel mixture its desired motion and the remaining 10% passed through the perforated flare to stabilize the flame.
What are air shrouds?
Guide the airflow around the nozzle and swirl chamber
What do liners do?
The area where the flame is held and supported by secondary airflow
What do interconnectors do?
Connect individual combustion chambers to propagate the flame on starting.
What does the discharge orifice do?
Accelerates and Directs airflow to the nozzle guide vanes and turbines.
What happens aft of the primary zone?
Aft of the primary zone is a further 10% of air is introduced to mix with the flame to form the main burning area in the secondary zone.
What happens in the dilution zone and what is the remaining air also used for?
The dilution zone is used to introduce the remaining 70% of air, which does not only continues the burning process but also cools the burnt gases to a. temperature acceptable for turbine entry.
What are the three common types of combustion chambers?
Multiple Chamber
Cannular chamber
Annular Chamber
Explain the Multi can/Multiple chamber, combustion chamber?
Consists of individual chambers fixed radially around the engine. These chambers are fed by individual ducts from the compressor and their exhaust must be merged prior to turbine entry.
Advantage: Ease of maintenance (Individual components)
Disadvantages: Poor use of radial space and often gives uneven air loads to the turbine.
Explain the Cannular Chamber?
Individual flame tubes surrounded by a common air casing. Provides better interconnection between tubes than the multiple systems. Allows for far more even mixing of combustion gases prior to turbine entry.
Found on many large turbojet/turbofan aircraft.
Explain the Annular Chamber?
Use of the whole annulus between the compressor and turbine to form a single combustion chamber. This is more space-efficient and for that reason can handle a larger mass for a given engine space. Thus can be lighter for a given thrust requirement. Suffers less pressure loss and requires less cooling. Still use 2 igniters for starting and a combustion chamber drain valve for after shutdown fuel draining.
What is a disadvantage of an annular chamber?
For maintenance, the engine must normally be removed from the aircraft.
What is a reverse annular flow chamber?
It flows over the liner and enters from the rear, with combustion gas flow being in the opposite direction to the normal airflow. Once combustion takes place gases flow into a deflector which turns them 180degrees to the turbine.
