Fan Flow Deflection for Supersonic Turbofan Engines

Abstract

We present an initial parametric investigation of fan flow deflectors for suppressing noise from supersonic turbofan engines. Realistic exhaust geometry and flow conditions for bypass ratio 2.7 were simulated in a subscale experiment. The study encompassed acoustic measurement and mean velocity surveys. The deflectors comprised internal vanes with both symmetric and cambered airfoil sections and deployable external flaps. Superior acoustic results were achieved using a combination of cambered vanes and perforated flaps, yielding cumulative (downward plus sideline) EPNL and OASPL reductions of 7.7 dB and 9.2 dB respectively. A fair correlation is established between the suppression of peak OASPL and the reduction of the radial velocity gradient on the underside of the jet.