15.5 Combustion section - 5q Flashcards
Combustion section consists of?
- Outer casing
- Inner perforated liner
- fuel injection system
- starting ignition system
Types of combustion chambers?
- Multiple can
- Can annular
- Annular through flow
- Annular reverse flow
Primary air?
Combustion only
Secondary air?
Combustion and cooling
Tertiary air?
Cooling only
How much of the airflow from the compressor is used for combustion?
Approx. 20%-30%
How much of the air bypasses the primary air zone and mixes with the hot gas inside the dilution zone?
Approx. 70%-80%
Fuel to air ratio?
15 parts air for every 1 part of fuel
(don’t get the ratio the wrong way round, fuel to air 1:15, air to fuel 15:1)
Toroidal vortex?
the air which stabilises and anchors the flame
What air does the toroidal vortex consist of?
Primary and secondary
Theoretically, combustion in the gas turbine engine occurs?
occurs at a constant pressure. achieved partly because of the brayton cycle and because the combustion chamber is an enclosed space
Multiple can advantages and disadvantages
Advantages
* Simple in design
* good structural strenth
* can be replaced individually
Disadvantages
* Large and heavy
* requires lots of space
* complex compressor ducting (aerodynamic losses)
* Ignition difficulties from one chamber to another
Can annular advantages and disadvantages
Advantages
* smaller and lighter than multiple can
* no complex air supply ducting
* good strucutal strength
Disadvantages
* High aerodynamic losses
* Ignition difficulties from one chamber to another
Annular advantages and disadvantages
Advantages
* smaller and lighter
* large combustion area
* complete combustion and smokeless
* flame can spread easy
* better thermal lead distribution for turbine
* less cooling air needed
Disadvantages
* Expensive
* Removal is difficult and time consuming
