A trial application of acoustic excitation for jet noise reduction

Abstract

Jet noise, one of the dominant noise components from an aircraft jet engine is known as the result of developed vortices produced during jet mixing process. In last couple of years, a method for jet noise reduction which acoustically controls the jet mixing layer using a sound excitation is proposed and investigated under the collaboration between The University of Tokyo and JAXA. In this paper, the main idea, experimental apparatus, experimental condition and experimental results will be explained. The experiment was conducted under an unheated and subsonic jet condition. The results show that low frequency sound excitation results in an increase in low frequency noise and a decrease in high frequency noise. The low frequency sound excitation is considered to excite the instability of jet flow and collapse the jet plume. On the other hand, the high frequency sound excitation resulted in a slight increase of high frequency noise and a slight decrease of low frequency noise (0.5 dB reduction in maximum) si...