Influence of model parameters and the vane response method on a low-order prediction of fan broadband noise

Abstract

The influence of modeling choices on a low-order method for predicting broadband interaction noise downstream of a fan stage in a turbofan engine is explored. The general method relies on experimentally or computationally obtained rotor-wake turbulence parameters as input. These parameters are used together with the Liepmann spectrum to define the inflow into the exit guide vane. Strip-theory allows the full 3D vane response to be constructed using a gust response model for a 2D vane. The sound power in the duct downstream of the exit guide vanes is calculated using the Green’s method for an annular duct. Comparison is made between the predictions obtained with a 2D flat-plate cascade gust response and a 2D flat-plate airfoil gust response. In addition, the effect of the inclusion of real vane geometry via an asymptotic gust response method is investigated. It is shown that for the current modeling method, a cascade response must be used and that the asymptotic method does not extend to high enough camber and angle of attack to be representative of modern vane geometries. It is concluded that the simpler flat-plate-based model is sufficient.