A Contra-Rotating Open Rotor Noise Reduction Methodology by Using Anhedral Blade Tip

Abstract

In this article, a novel contra-rotating open rotor (CROR) noise reduction methodology based on the anhedral blade tip applied to the front blade is developed. Results indicate that anhedral blade tip can provide noise reduction over 60 deg. polar angle range in both upstream and downstream areas at takeoff condition. The noise reduction becomes more significant as the lean angle of anhedral blade tip increases, and the maximum noise reduction is over 4 dB. Further analysis shows that anhedral blade tip decreases the strength and size of blade tip vortex shed from the front blade and reduces its interaction with the rear rotor, which decreases the fluctuation of loading acting on the rear rotor and its loading noise. Furthermore, the anhedral blade tip does not have a significant effect on the aerodynamic performance of CROR at cruise.