Advanced Measurement and Analysis Techniques for Aircraft Core Noise: Application on the BEARCAT Turboshaft Research Test Bench

Combustion noise becomes an increasing acoustic source on new turbofan architectures. Experimental characterization of core noise is made complicated by the difficulty to integrate sensors inside the engine, especially in the hot parts. This paper presents a test campaign performed on the BEARCAT research turboshaft engine, which allows sensor insertion inside the hot parts (combustion chamber, turbine inter-stages). Remote microphone probes as well as a thermocouple have been installed at different locations in order to measure pressure and temperature fluctuations. Coherence based methods have been applied to the test data and allowed to detect combustion noise. Acoustic coherence with downstream pressure sensors is present for both direct and indirect combustion noise. Temperature-pressure coherence made it also possible to highlight indirect core noise.