Computational and Experimental Investigation of Fan Flow Deflection for Supersonic Turbofan Engines

We present a combined experimental and computational study of the dual-stream exhaust of a supersonic turbofan engine with noise-suppressing deflectors installed in the fan stream. The focus is on validating the computational code, extracting turbulent kinetic energy (TKE) trends, and connecting those trends to the measured noise reduction. We consider two operating conditions, a “cold” condition at which mean flow surveys were conducted and against which the code was validated; and a “hot” condition that corresponds to the takeoff engine cycle and at which acoustic measurements were conducted. A threedimensional Reynolds-Averaged Navier Stokes code is used to simulate the flow for a number of nozzle configurations using vane type flow deflectors to create asymmetric jet plumes, which have demonstrated experimentally the potential for significant noise reduction. The code successfully replicates the mean velocity, radial velocity gradient and inflectional layer fields of the experimental flows. Comparison of “cold” and “hot” condition shows a reasonable collapse of the velocity profiles when the axial distance is normalized by the potential core length. For both conditions, the vane deflectors reduce the TKE on the underside of the jet and increase it on the topside of the jet. There is a significant correlation between the decrease of the TKE near the end of the potential core and the reduction in overall sound pressure level in the direction of peak emission. This study will provide a basis for the further use of CFD in the investigation of noise reduction and performance of fan flow deflected supersonic turbofan engines.