EXPERIMENTAL INVESTIGATION OF LOW PRESSURE TURBINE NOISE: RADIAL MODE ANALYSIS FOR SWIRLING FLOWS

12th International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines The well known Radial Mode Analysis (RMA) technique, developed to derive the modal content of an in-duct measured acoustic pressure field, has been applied to the experimental investigation of tone noise generation and transmission mechanisms within low pressure turbine stages. To improve the accuracy of the modal decomposition when dealing with highly 3D flows, such as intermediate LPT rows and turbine off-design operating conditions, the classical RMA technique for uniform axial flows has been extended to account for flow swirl. This paper describes the RMA method implemented at University of Florence and presents the first experimental results from the LPT tone noise investigation carried out at Avio acoustic cold flow, for which the RMA has been developed.