turbofanengine

A turbofan engine is a type of jet engine that uses a large fan at the air intake to produce thrust from bypass air, while the core produces additional thrust through combustion. By moving a large mass of air at moderate speed, turbofans achieve higher propulsive efficiency and quieter operation than pure turbojets, especially at subsonic speeds.

The basic layout includes an inlet, a multi-stage compressor, a combustor, and turbines that drive the compressor and the fan. The air drawn by the fan splits; most bypasses the core in a dedicated duct, while a smaller stream enters the core for combustion. The combined exhaust provides propulsion, and many engines include thrust reversers for landing. Some military variants use afterburners or geared fans to optimize performance.

Bypass ratio, the ratio of bypass air to core air, is a key design parameter. High-bypass turbofans dominate commercial airliners and offer better fuel efficiency and lower noise; low-bypass designs are used in some military aircraft that require higher exhaust speeds. Geared turbofan architectures slow the fan relative to the core to improve efficiency across operating ranges.

Development began in the mid-20th century, with rapid adoption in the 1960s–1980s. Today, turbofans are the standard propulsion for most airliners and many other aircraft, with ongoing advances in materials, aerodynamics, and acoustics.