Technique to Analyze Characteristics of Turbomachinery Broadband Noise Sources

Abstract

In this paper an experimental technique for the decomposition of broadband ducted sound fields into their mode constituents is applied to two laboratory scale experimental setups. The broadband mode analysis technique is based on spectral coherences. In both cases, incoherent broadband sound fields were excited by means of a loudspeaker array. The results derived from the basic setup S1 were validated successfully with analytical findings. The second setup S2 mimics the fundamental arrangement in an aero-engine exhaust, consisting of a broadband sound source (an annular combustor ring) and a turbomachinery stage (the LP turbine). In between, microphone arrays are arranged to acquire the broadband sound fields. Sample results of setup S2 are presented analyzed by means of the new technique. The experimental outcome proves the usefulness of the analysis technique to help interpreting and understanding broadband sound propagation in turbomachinery flow ducts.