Because the fuel flow rate for the core is changed only a small amount by the addition of the fan, a turbofan generates more thrust for nearly the same amount of fuel used by the core. This means that a turbofan is very fuel efficient. ... Low bypass ratio turbofans are still more fuel efficient than basic turbojets.

Are turbojet engines efficient?

A turbojet engine with a convergent nozzle is operating at 100% power at M 0 = 0.9 and an altitude of 11 km. The engine characteristics are such that the compressor, burner, and turbine efficiencies may be taken as 0.85, 0.96, and 0.90, respectively.

How is turbojet different from turbofan?

Unlike a turbojet that sucks in all the air inside the engine, a turbofan engine sports a large fan at the front which sucks in most of the airflow around the outside of the engine. This makes the engine quieter and more thrust at low speeds. A majority of all the airliners are powered by this engine.