Aerodynamics of Fan Flow Deflectors for Jet Noise Suppression

We present a three-dimensional Reynolds-averaged Navier–Stokes investigation of the impact on nozzle aerodynamic performance of deflector vanes used for noise suppression in separate-flow turbofan engines. The vanes are installed in the bypass duct and deflect the bypass plume downward relative to the core plume. This study considers a single pair of vanes, with a NACA 0012 airfoil section, installed in a realistically shaped nozzle operating at static conditions. The vane airfoils are subjected to an externally imposed favorable pressure gradient which delays separation and distorts the pressure distribution around the airfoils. The axial and transverse forces of the system comprising the nozzle walls and the vanes are computed for various vane angles of attack. It is shown that the thrust loss of the bypass stream ranges from 0.04%with the vanes at zero angle of attack to 0.10% for vanes at 8 deg angle of attack. For an entire engine with bypass ratio of 5, the corresponding losses are approximately 0.03 and 0.08%. The vanes have an impact of less than 0.025% on the nozzle flow coefficient.