What replaces the geared propeller in turbofan engines?

• A. Jet engine nozzle
• B. Enclosed axial flow fan replaces the geared propeller
• C. Turbine blade
• D. Direct thrust nozzle

Answer: (B)

In turbofan engines, thrust is mainly produced by a large-diameter axial-flow fan at the front of the engine, housed in the nacelle. This enclosed fan replaces the external geared propeller used in turboprops, delivering a high mass flow of air with modest speed increase. The bypass air around the core provides most of the thrust and is exhausted through a nozzle, while the core handles compression and combustion.

This front fan is integral to the engine and is driven as part of the engine’s low-pressure section, rather than being a separate propeller with a reduction gear. The other options refer to components involved in the exhaust or core, not the primary front-stage propulsion device.