High Bypass Separate Flow Exhaust System Improved Thrust Efficiency By Modifying the Aft Centerbody

Scale model data indicated a performance dip in nozzle thrust efficiency at the cruise design conditions for a high bypass separate flow derivative exhaust system. A performance improvement program was implemented to determine the cause of the reduction in thrust efficiency and to identify viable redesigns. Data analysis indicated the performance loss to be a result of high Mach number fan and core exhaust interactions adversely affecting the pressure force on the exhaust system centerbody. Scale model testing confirmed the cause of performance loss and demonstrated that modifying the aft centerbody to reduce the plume Mach number recovers the loss in exhaust system thrust efficiency.