Extension of a Fan Tonal Noise Cascade Model for Camber Effects

Abstract

To account for vane camber effects in fan/outlet-guide-vane interaction noise prediction, a two stagger-angle method is proposed that extends a flat-plate cascade analytical model. This method is applied to fan tonal noise for which camber effects are known to be significant. First, this camber model is successfully compared to numerical predictions for a two-dimensional cascade/gust interaction test case. The two-stagger-angle method is then applied to an actual axial compressor stage, for which an unsteady flow simulation provides the acoustic sources on the vanes that are radiated with an acoustic analogy and serve as reference data. A clear improvement is obtained in the analytical prediction of modal acoustic power radiated within the duct with the camber method, relatively to the original flat-plate cascade model. Indeed, the gaps with the numerical results are below 1 dB for most of the tones. Moreover, the unsteady loadings are investigated and show that, even if the interaction sources are dominant in the vane leading-edge region, their distribution on the rest of the chord has a major influence on the acoustic prediction.