Effects of Radially Variable Sweep Vanes on Rotor-Stator Interaction Noise

This paper presents a three-dimensional semi-analytic cascade model for the prediction of rotor-stator interaction noise, which includes the effects of radially variable sweep angle and chord length to better account for the latest trends in the fanstage stator design of turbofan aero-engines. The theoretical modelling and solution method are first introduced, with special attention paid to the singularity problem brought by the non-uniformity of the stator vanes in the radial direction. The tonal rotor-stator interaction noise for stators with a radially varying sweep angle or a radially varying chord length are then calculated and analyzed. It is discovered that the phase variation in unsteady pressure loading near the stator leading edge greatly affects the resulting tonal interaction noise, while the sweep of a stator trailing edge shows less influence on the rotor-stator interaction. The duct mode characteristic of the cut-on modes is proved to be an important factor for the design of a swept stator. In addition, the soft vane design can further reduce the tonal interaction noise on a swept stator cascade.