Image Number 5 for United States Patent #4909346.
A noise suppression system for use with a jet aircraft engine having a plug support cylinder affixed to the engine, a tubular ejector shroud affixed to the engine and encompassing the plug support, the shroud having a reduced internal diameter adjacent the aft end and a plurality of spaced apart blow-in openings formed circumferentially about the shroud forward end providing passageways for the entrance of ambient air from the exterior to the interior of the shroud. A blow-in door is secured to the shroud for opening and closing each of the blow-in openings. A translating plug is supported on the plug support cylinder and is positionable between a forward position and an aft position and forms an annular exhaust nozzle between the exterior of the plug and the interior of the aft end of the shroud. A daisy mixing nozzle is positioned within the shroud aft of the blow-in doors, the nozzle being configured of a plurality of lobes providing undulating interior and exterior surfaces. When the plug is in the forward position the blow-in doors are open permitting ambient air to mix with exhaust gas from the jet engine and the nozzle area is enlarged producing lower gas velocities and lower sound intensities. When the plug is in the aft position, the blow-in doors are closed and the nozzle area is reduced providing higher gas velocities for increased thrust with some increase in sound intensity.