GB874512A - Jet propulsion engine noise suppression nozzle - Google Patents

Abstract

874,512. Jet propulsion nozzles. BOEING AIRPLANE CO. March 13, 1959, No. 8833/59. Class 110 (3). A silenced jet-propulsion nozzle comprising a rearwardly directed gas discharge duct having wall portions defining an axially extending interruption in the duct causing total or partial separation of the gas streams and forming a passage for rearward movement of atmospheric air, has bleed ports in the duct upstream of the discharge arranged to discharge engine exhaust gases into the passage to increase the airflow through it. The propulsion nozzle, Fig. 1, comprises an outer shell 18, and a central island 19 and tail cone or plug 22 between which are arranged wedge-shaped flow dividers 26 so as to form branch streams of exhaust gases which are materially separated. Each divider comprises sides 26a, 26b which form a passage for atmospheric air leading from an opening 30 in the shell 18. The air flow in each divider is separated by a plate 32 into two streams, one of which is discharged from the rear edges of the sides 26a, 26b and the other is discharged into the interior of the tubular member 20 through openings 34. Increased air flow through the spaces separating the air streams is obtained by bleed ports 36 which allow some of the exhaust gases to pass into these spaces in a downstream direction. If desired, bleed ports may be provided to increase the flow into member 20. A sound insulating or absorbing shroud 38 surrounds the discharge end of the nozzle shell 18. The shroud 38 is preferably of hollow construction and is packed with a glass fibre bat 46 and its inside wall is provided with perforations 48. A flange 44, and vortex generators or deflectors 49 create turbulence and improve the mixing of the exhaust gases with the atmospheric air. A ring-like spray tube 51 may be provided to inject water into the gas stream. In a modification, Fig. 4, the nozzle shell 50 is of a special corrugated form comprising circumferentially spaced deep and wide corrugations 50a separated by groups of narrower and shallower corrugations 50b. The depth of these corrugations is a maximum at the nozzle exit and progressively decrease towards the nozzle inlet. Air ejector bleed ports 52 are provided, especially in the corrugations 50a to increase the air flow through the corrugations. A sound absorption ejector shroud ring 54 similar to the shroud 38 is also provided. Specification 831,152 is referred to.