Abstract
Modern civil turbofan aero-engines are faced with the challenge of noise control in a shorter nacelle and a larger bypass ratio fan design. Accordingly, the concept of soft vanes, in which fan outlet guide vanes (OGV) are implemented with permeable surfaces, is proposed to further reduce the rotor-stator interaction noise in future aero-engines. A three-dimensional cascade model is used to study the noise reduction of perforations on OGVs under practical situations as an application of soft vanes. The effects of spanwise coupling of the unsteady loading are studied and comparisons are made between a fully coupled model and a decoupled situation. The noise reduction effects of a perforated-plate based soft vane design under practical background mean flow at different operating conditions are then estimated using an in-house impedance model that accounts for the tangential mean flow and other practical factors.
