EXPERIMENTAL RESEARCH ON LPT-TONE NOISE BY IN-DUCT MEASUREMENT TECHNIQUES

The reduction of the noise emissions of civil aircraft engines is a key-objective for the international scientific research. Through the development of new engine architectures (high by-pass ratio) noise from the fan and jet has been reduced significantly and the contribution from low pressure turbine (LPT) has become relevant. At S. Stecco Energy Department in Florence a dedicated wind tunnel has been developed with the aim of investigating aeroacoustic noise generation mechanisms in LPTs. The rig simulates a realistic turbine stage and provides a swirling mean flow in an annular test section. To perform the necessary in-duct noise measurements two rakes with miniaturized dynamic pressure sensors have been studied and realized and their dynamic response has been investigated in a dedicated test facility against a reference microphone. The present paper describes the wind tunnel and the measurement methods developed. Moreover, the results of the dynamic calibration of the sensor rakes are presented and results from the experimental investigation of tonal noise by means of in-duct measurements inside the test rig are reported.