A system of nozzles and pylons that redistributes jet exhaust noise sources upstream to reduce jet noise has been developed. Certain aircraft configurations install the propulsion engines above the wing or tail surfaces, or above the fuselage, or in some cases above the structure that is a blend of the wing and body or hybrid wing body aircraft. In these aircraft configurations, reducing noise propagation to the community below is possible by using the aircraft as an acoustic shield for the sources associated with the engine. The more difficult engine noises to be shielded are from the jet exhaust because they are typically distributed downstream, the equivalent of several engine nozzle diameters. This innovation redistributes jet exhaust upstream to reduce noise.
The first embodiment of this invention adds an external pylon structure that's common on engine-under-the-wing installations to the nozzle, which also structurally holds the engine to the airframe. The second embodiment uses the configuration of the first embodiment, but adds nozzle chevrons on the fan nozzle, on the core nozzle, or both.
The chevrons can be of either circumferentially uniform design or azimuthally varying design, with the chevrons of greater size and flow immersion on the side of the nozzle adjacent to the pylon. The third embodiment has two pylon structures 180 degrees apart from each other. One pylon structurally connects the engine to the airframe (the keel position) and is of a design that produces a weak acoustic pylon effect. The pylon on the opposite side of the air-frame (the crown position) structure produces a strong acoustic pylon effect. There can be several variations of this embodiment with round nozzles, circumferentially uniform chevron nozzles, or azimuthally varying chevrons with the chevrons of greater size and flow immersion adjacent to the pylon that produces the strong acoustic effect.