Structural Integrity of Serrated Leading Edge Guide Vane Blades for Noise Reduction

Abstract

One of the major noise sources of high bypass ratios modern turbofan engines arises from the interaction between the turbulent rotor wake, the tip-leakage and the leading edge of the downstream outlet guide vanes. Recent research has confirmed that leading edge serrations are an effective passive control for reducing noise. However, for transferring serrated leading edges to modern, environmentally friendly aero engines, the bypass outlet guide vanes must fulfil both aerodynamic and structural requirements. The current study aims at characterizing the structural behaviour when adding serrations to the leading edge of bypass outlet guide vanes designed for a configuration without classical struts. It was found that the structural performances deteriorate with increasing number of serrations, directly related to the serrations wavelength, and with their amplitude. The buckling loading factor decreases and the total deformation increases constantly with the increase of both parameters. The presence of the troughs of the serrations introduce stress concentrators. For large enough values of either the wave length or amplitude of the serrations, the maximum von Mises stress increases significantly, and can as much as double in value. At the same time, the location of the maximum stress on the vane moves from its original position, on the leading edge of the casing fillet, to the troughs of the serrations.