DEPENDENCE OF FAN TONE NOISE ON AXIAL GAP BETWEEN FAN ROTOR AND STATOR IN ROW-TO-ROW ACOUSTIC INTERACTION

摘要

This paper describes the investigation of dependence of fan tone noise on axial gap between fan rotor and stator in row-to-row acoustic interaction. In this work, a three-dimensional lifting surface theory for a fan stage model composed of a rotor and a stator is used to calculate the sound field under acoustic interaction between rotor and stator. In the parametric study with the fan rotor-stator axial gap varied as an independent variable, the predicted acoustic power level of rotor wakes-stator interaction noise shows no monotonous variation with the axial gap, but sharp and round peaks at certain axial gaps. The investigation of the relevance of axial wave lengths of acoustic duct modes to the gaps between the rotor and the stator indicates that the peaks might be caused by a resonance mechanism similar to the acoustic response in a resonator.