What is the purpose of the air shroud on an atomizer-type duplex fuel spray nozzle in the combustion chamber of a gas turbine engine?

• A. To reduce carbon deposits around the nozzle tip and nozzle
• B. To increase fuel flow
• C. To cool the nozzle
• D. To improve atomization

Answer: (A)

The air shroud around an atomizer-type duplex fuel spray nozzle is there to prevent carbon buildup on and around the nozzle tip. By surrounding the spray with a curtain of air, it washes away fuel vapors and dilutes fuel-rich regions that would otherwise contact the hot nozzle surface and carbonize, forming coke. This keeps the nozzle clean, preserves the intended spray pattern, and helps maintain stable combustion. The shroud’s effect on atomization is secondary, and it’s not primarily designed to increase fuel flow or cool the nozzle, though the moving air can have a minor cooling effect.