Exhaust mixer

In aviation, an exhaust mixer / flow mixer is a feature of many turbofan engines, where slower, colder bypass air is mixed with faster, hotter core exhaust gases, before exhausting to atmospheric pressure through a common (mixed flow) propelling nozzle.

Additionally, the temperature of the exhaust is reduced, contributing to the overall reduction of the thermal signature of the aircraft.

A mixer helps reduce the fastest exhaust velocities from the core of the engine, while making the average exhaust velocity faster, producing more thrust with the same energy.

Mixers are extremely common on military turbofans, since long coaxial exhaust pipes (i.e. hot and cold) are avoided.

Some high bypass ratio (e.g. civil) turbofans now feature a mixer, the advantage being a small thrust gain, which improves specific fuel consumption.