Using Microjets as an Efficient Technique for Jet Noise Reduction in High Bypass Turbofan Engines

Nowadays, noise has turned into one of the most important among the environmental factors on which industry sets down a big part of its efforts and concerns. The quality of life of many people living under approach or departure flight paths can be affected by aircraft noise. These effects arise from the effect of noise on concentration or sleep and from feelings of anger, frustration and powerlessness to control the noise. Aircraft noise arises from both engines and the movement of turbulent air over the physical structure (airframe) of an aircraft. To date, noise reduction has focused mainly on reducing engine noise. Microinjection system, impacting the main jet, has shown the ability to suppress jet noise through velocity profile modifications. In this paper, the mechanism of microinjection system and the main applications, in both subsonic and supersonic flight condition, in turbofan engines are presented.