Optimization of Fan Flow Deflection for Supersonic Turbofan Engines

This study involves the application of fan flow deflectors for suppression of jet noise from low-bypass turbofan engines for next-generation supersonic aircraft. Experiments using canonical vane deflectors seek to establish correlations between aerodynamics, distortion of the mean velocity field in the jet plume, and noise reduction. The maximum radial velocity gradient, as a function of axial distance and azimuth angle, is used to quantify distortions of the plume. Vanes mounted at low azimuth angles (with respect to the downward vertical) reduce gradients in the downward direction, while vanes mounted at high azimuth angles reduce gradients in the sideline reduction. There is a significant correlation between gradient reduction and noise suppression in the azimuthal direction of the gradient. In addition, it is found that vanes with cambered airfoils perform better than vanes with symmetric airfoils. The trends obtained were used in the successful design of deflector configurations consisting of two pairs of vanes which resulted in cumulative peak overall sound pressure level (OASPL) and effective perceived noise level (EPNL) reductions of 8.8 dB and 6.7 dB respectively.