What is the function of the bypass fan in a gas turbine engine?

The function of the bypass fan in a gas turbine engine is to provide additional thrust. In a typical turbofan engine configuration, which includes both a core engine and a fan at the front, the bypass fan moves a large volume of air around the engine core, contributing significantly to the overall thrust produced by the engine. This design allows for more efficient operation, as the fan can generate thrust with comparatively less fuel consumption than solely relying on the combustion process in the engine core.

By increasing the amount of air moved without necessarily using additional fuel, the bypass fan enhances the engine's efficiency, particularly at subsonic speeds, which is essential for commercial aviation. This is why the bypass fan is a critical component in modern jet engines, focusing on thrust generation by leveraging the principles of aerodynamics to maximize performance.