Quantification of core noise using coherent output method: experiment and result on turbofan demonstrator

New turbofan architectures have increasing bypass ratios which makes the core noise an more important source. An identification of its contribution in the total noise has been performed on a DGEN380 turbofan demonstrator using pressure measurement: The remote pressure probes with piezo-electric pressure sensors are installed at 14 locations in the nozzle. The far field noise was caught using 25 microphones array parallel to the engine axis. A coherent output power analysis based on multiple reference channels was applied to identify the active part of the combustion noise and in a reciprocal way the acoustic component in the duct propagated in the test room. The processing allows to calculate the far field contribution and directivity of the core noise. K-type thermocouples were implemented to quantify temperature fluctuations in the engine nozzle. The thermocouples were manufactured with two different wire diameters (from 25 to 80µm) which give different frequency responses. An in-situ compensation method was developed to correct the signal and increase the useful frequency range of the temperature measure. This allows to cover the whole core noise frequency range. This project has received funding from the Clean Sky 2 Joint Undertaking (JU) under grant agreement No. 886554.