Experimental Investigation of Rotor Shielding Effects on Axial Flow Fan Using Interstage Array

An experimental investigation is performed on a smallscale axial flow fan in a ducted configuration to observe rotor shielding effects.The study focuses on spinning azimuthal modes incident on a rotor-stator layout in the presence of flow.The sources considered are a ring of loudspeakers generating a particular spinning mode.Along with the reflection and modified transmission, several phenomena like mode scattering and mode trapping are expected.An array of 64 microphones is employed in the interstage, i.e. between the rotor and stator rows.The microphones are arranged in two rings and two spirals on the duct surface using a remote probe configuration and its axial extent is 40mm.The interstage array helps in providing a detailed understanding of the noise propagation between the rotor-stator rows.The modal decomposition is based on a Bayesian inversion method.Both the frequency dependence and the spin direction are examined at various engine operating points.