Scale model testing of the jet noise characteristics of the JT8D refan engine nozzle system

The results are presented of static scale model acoustic tests of the nozzle system for the JT8D-9 baseline engine and candidate nozzle systems for JT8D-109, JT8D-115, and JT8D-117 refan engines. The objective of these tests was to determine the jet noise benefit of the three refan engine cycles relative to the baseline JT8D-9, and to provide acoustic information toward selection of the optimum primary-secondary area match and centerbody contour for the refan engine cycles. One of the nozzle configurations was tested with and without simulated turbine exit swirl to determine what effect, if any, swirl has no jet noise. The JT8D-109 cycle was found to afford approximately 9 db (0ASPL) jet noise reduction relative to the JT8D-9 when compared on an equal static thrust basis. The JT8D-115 and JT8D-117 afford an 8 db and 6 db reduction, respectively, relative to the JT8D-9, at equal static thrust. Turbine exit swirl was found to have no significant effect on the jet noise of the JT8D-109 nozzle system.