What is the primary function of the fan in a turbofan engine?

In a turbofan engine, the primary function of the fan is to suck air into the engine and produce bypass thrust. This is a crucial aspect of its design and operation. The fan draws in a large volume of air and directs a substantial portion of this air around the engine core, which is referred to as bypass air. This bypass air contributes significantly to the overall thrust produced by the engine, making turbofan engines particularly efficient for commercial aviation use, as they provide a high thrust-to-noise ratio and lower specific fuel consumption compared to other types of jet engines.

This bypass thrust is generated because the fan is large and operates in a manner that accelerates the airflow significantly, resulting in increased thrust without the need for as much fuel combustion as seen in pure jet engines. The efficiency of bypass thrust is a key factor in how turbofan engines perform, making them ideal for long-distance flights where fuel efficiency and low noise levels are prioritized.