Book Description

Several noise suppressors consisting of combinations of mixing nozzles and ejectors were tested on two full-scale turbojet engines. Maximum sound pressure level reductions of 12 decibels and sound power level reductions of 8 decibels were obtained. The ejectors provided 3 to 5 decibels of the sound power reduction. The effects of ejector dimensions on noise suppression and engine performance were investigated. Ejector lengths of approximately 2.0 standard nozzle diameters and ejector diameters larger than 1.6 standard nozzle diameters provided the greatest additional noise reduction to that obtained with the mixing nozzles alone. The ejector can restore the static thrust loss caused by use of the mixing nozzle or can provide static-thrust augmentation.