The hot core flow of a turbofan engine is mixed with the cooler fan flow in a lobed mixer nozzle. The mixing and cooling of the exhaust is important for several reasons. First, it can significantly reduce engine noise levels. By mixing the fan and core flow, the air stream exiting the engine has a reduced velocity and consequently generates less noise. Another benefit of mixing the hot and cold air is that the thermal signature of the exhaust is reduced. This is especially important in the design of military engine applications as designers attempt to enhance the survivability of the aircraft.

FLUENT can be used to study the effectiveness of a lobed mixer nozzle for a turbofan engine exhaust system. Results indicate that the exhaust gases can be efficiently mixed so that the temperature of the exhaust stream from the nozzle is well below that of the exhaust from the engine. The lowering of the exhaust temperature in this manner helps prevent the overheating of the exhaust system components, reduce engine noise, and alter the signature of the aircraft for military applications.

Temperature in the mixing zone and on the nozzle components