Combustion Section Flashcards
2 layers of the combustion section and purpose
Air casing - cool and dilute the air in the flame tube
Flame tube - burns fuel supplied by the compressor - must be done with min loss of pressure and max release of heat
Hottest part of the combustion section
Primary zone - were combustion takes place
Multiple can combustion system
Cans are arranged around the turbine shaft
Multiple flame tubes with interconnecting tubes
Each can is surrounded by an outer casing
Mutliple can system adv and disadv
Makes for easier servicing
Does not prevent gas stream to all areas of the turbine
Tubo annular system
Cans arranged closer together
Whole assembly surrounded with an inner and outer air casing
Adv and disadv of a tubo annular system
Servicing is more difficult
Presents the gas stream to a greater area of the turbine
Annular chamber system
One single annular flame tube with inner and outer air casing
Adv and disadv of annular system
Shorter combustion section
Easier flame propagation
Presents the gas stream to all areas of the turbine
Shaping of the flame is more difficult
Combuster chamber flow break up
20% into primary zone
80% is used for cooling and dilution where 20% goes into the primary cooling, 40% into the cooling of the dilution zone and 20% dilution in the dilution zone
Purpose of the diffuser
AVTUR is less volatile - if you allow air straight from the compressor - it will blow it away
Diffuser is a divergent duct - slows the air down
Air from the compressor = 500ft/sec AVTUR = 2-3fps
Purpose of swirl vanes and perforated flare
Induce a vortex to mix the fuel and air
% pressure drop in the combustion section
5%
Air to fuel ratio in the combustion section
15:1
However due to the remaining 60% going into the dilution zone the overall air fuel ratio can be as high as 60:1
Purpose of a pressuring valve
Allows you to maintain pressure with a little amount of fuel
Purpose of fuel drains
Spring loaded valve - drain unburned fuel in the combustion section
Held closed by the pressure of combustion - anything over 0.5psi will close the valves