The document discusses ignition and fuel supply in gas turbines. It describes how ignition occurs during start up when an igniter plug lights the fuel injected into the combustion chamber. Some gas turbines can burn mixtures of gas and liquid fuels. It also describes the different types of fuel nozzles used, including vaporizer, atomizer, swirl, simplex, duple, duplex, spill, and rotary nozzles. The fuel nozzles inject and atomize fuel into the combustion chamber for combustion.

1. Ignition &
Fuel Supply

2. Ignition occurs during the start
cycle
FUEL is injected at the
upstream end of the burner.
*** Some gas turbines are “bi-fuel”. They
may burn a mixture of gas and liquid fuel.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

3. The igniter plug(s) is (are)
located
in the combustion liner
adjacent
to the start fuel nozzle.
The flame lights off the can closest the igniter
and cross tubesa typical number flame
rapidly conduct the
TW is
O
to the other combustion cans.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

4. On engine shutdown,
or, if start failure occurs,
the combustion chamber drain
pressure-actuated valve
automatically DRAINS any
raw fuel from the
combustion chamber
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

5. Fuel Nozzles
Fuel must be atomised or
vaporised
Function: inject the fuel into the
combustion chamber
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

6. Common Types
• Vaporiser
• Atomiser
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

7. VAPORISER TYPE
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

8. ATOMISING TYPE

9. Swirl Atomiser
• consists of a small cylindrical or conical
cavity into which a number of streams of
fuel enter through tangential holes.
• The direction of fuel entry into the cavity
creates a vortex and the swirling fuel
leaves in atomised form from a single
orifice.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

10. SIMPLEX

11. provides good atomisation
at HIGH fuel pressures
• unsatisfactory at LOW fuel
pressures and at LOW engine
rpm,
especially at high altitudes.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

12. DUPLE & DUPLEX

13. • two sets of atomisers, one for low flows
and both combined for high flows
• two manifolds, the primary and the main,
supply fuel to the nozzles
• each nozzle has two swirl chambers, one for
the primary flow and the other for the main
flow
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

14. Spill Type
• supply fuel to the swirl chamber at a
high pressure all the time
• ADVANTAGE: satisfactory swirl
providing constant and efficient fuel
atomisation (even at the extremely low
fuel flows that occur at high altitude)
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

15. Rotary Atomizer
• feeds fuel into the centre of the main
shaft
• fuel is atomised by the
CENTRIFUGAL action of the shaft.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

16. Spray Nozzle
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424

17. • Primary air is introduced with the
injected fuel. Aerating the spray in this
manner achieves greater burning
efficiency, therefore reducing both
carbon formation and exhaust smoke.
The comparatively low pressures
required for atomisation also makes it
possible to use the lighter gear-type
pump.
Intro
Process
Fuel supply
Types
COMBUSTIONMaterials
CHAMBER
AE 424