FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesMedium
A technician inspects the combustor liner of a turbine engine and notes rows of small holes and slots along the liner wall. What is the primary purpose of these holes?
- ATo meter bleed air to the anti-ice system
- BTo allow fuel to be injected directly into the primary combustion zone
- CTo admit compressor discharge air that forms a cooling air film along the liner wall
- DTo allow igniter plugs to be inserted into the combustion chamber
Show answer & explanationAnswer & explanation
Correct answer: C. To admit compressor discharge air that forms a cooling air film along the liner wall
Combustor liners use film/effusion cooling holes that admit compressor discharge air, which flows along the inner wall as a protective film, insulating the liner from the extreme radiant and convective heat of combustion gases.
Why the other options are wrong
- A. Anti-ice bleed is tapped elsewhere, not through liner cooling holes.
- B. Fuel is introduced through nozzles, not liner cooling holes.
- D. Igniter plugs are installed through dedicated bosses, not cooling holes.
Combustor Liner Cooling
Small holes/slots in the combustor liner admit compressor discharge air to form an insulating film that protects the liner from combustion heat.
- Uses compressor discharge (P3) air
- Forms a boundary-layer cooling film
- Protects liner from radiant/convective heat
- Also dilutes gases before turbine entry
Memory trick: Film holes = a fire blanket of air