Sound Diffraction by the Splitter of a Turbofan Engine

摘要

The diffraction of noise by a splitter that separates the bypass flow from the211u001eflow into the core engine of a turbofan engine is analyzed. By using the Wiener-211u001eHopf technique a closed form solution is found. This solution is then analyzed 211u001enumerically and results on single modes are discussed. It is demonstrated that 211u001eacoustic modes of high radial order undergo more effect of diffraction than low 211u001eorder radial modes. Also the low order radial modes originating from the inner 211u001estator row (Engine Sector Stator; ESS) seems to be more affected by diffraction 211u001ethat those coming from the outer stator row (Outlet Guide Vanes; OGV). Due to 211u001ediffraction a small part of the noise is reflected or deflected from ESS to OGV 211u001e(or from OGV to ESS). However, the largest part of the noise propagates towards 211u001ethe fan. The major effect of diffraction is a redistribution of the noise over 211u001eradial acoustic modes.