GB906792A - Jet propulsion engine noise suppression nozzle with multiple settings - Google Patents

Abstract

906,792. Jet propulsion nozzles. BOEING AIRPLANE CO. Aug. 30, 1960 [Oct. 30, 1959], No. 29930/60. Class 110 (3). A jet propulsion noise suppression nozzle comprises a nozzle duct having a plurality of elongated trough-like elements extending longitudinally thereof at spaced locations about the duct periphery to produce a corrugated nozzle effect at the rearwardly discharging end of the duct, means to increase the noise reduction including a plurality of elongated auxiliary ducts normally housed in the troughs and pivotally mounted therein to swing outwardly into an extended position disposed generally transversely to the direction of discharge with their discharge apertures facing aft and means operable to decrease the nozzle opening by an amount approximately equal to the increase due to the auxiliary ducts and thereby maintain the effective nozzle opening approximately constant. The nozzle comprises a duct 10 formed between a tail pipe 12 and a central tail cone or plug 15. The tail pipe 12 has a rearward extension 12a having longitudinal troughs 14 located at regular intervals about its periphery. Auxiliary nozzle ducts 20 normally lie in the respective troughs 14. The ducts 20 may be moved from the position shown in Fig. 1, in which their outer walls 20b form an extension of the tapered cowl 16 to the position shown in Fig. 6 in which their inner walls 20a are approximately perpendicular to the engine axis A. Each of the walls 20a have rearwardly facing apertures and vanes 20c which are slanted outwardly so that exhaust gases from the duct 10 which are led into the ducts 20 by curved walls 20e are discharged in a rearward and outward direction. To compensate for the additional nozzle area of the apertures in the wall 20a, apertured doors 30 are hinged to the rear edges of the troughs. Preferably tabs 36 hinged with the door sections partially close the nozzle orifice area between the base circle of the troughs and the island member 34 when the doors are closed. Pneumatic or hydraulic actuators 40 operate the ducts 20 through links 44. Cranks 50 and links 52 are provided to co-ordinate the movement of the ducts 20 and doors 30. In a modification, Fig. 7 (not shown), the auxiliary ducts are pivoted to the downstream end of the nozzle. Openings in the duct through which the gases flow to the auxiliary ducts are normally closed by a flap valve. When the ducts are in operation, the flaps are moved into a position in which they reduce the nozzle area.