11th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The noise emission of a V2500 engine during ground operation was investigated with the A320 research aircraft ATRA of the German aerospace center DLR. Acoustic measurements with a microphone array parallel to the engine shaft axis were performed with the engines running at different speeds between idle and maximum continuous thrust. The main measurements took place in a noise-protection hangar, because optical measurents with laser devices were performed in parallel. In order to assess the impact of the room acoustics on the sound field, reference measurements were performed under free-field conditions, using the same microphone array set up on the ground. The array data were analysed using classical spectral methods and the SODIX (source directivity modelling in the cross-spectral matrix) method. SODIX fits equivalent source distributions, for different frequency bands and emission directions, to the measured cross-spectral matrices. The results show sources at the engine inlet, nozzle and along the jet. When the spectra and source distributions from the main measurements in the hangar are compared to the free-field data, the deviations are acceptable. This confirms that this type of noise protection hangar is a suitable environment to perform acoustic measurements of aircraft engines.