GB1204691A - Variable geometry nozzle capable of producing a silencing effect - Google Patents

Abstract

1,204,691. Jet propulsion nozzles. SOC . NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Sept.19, 1967 [Oct. 7, 1966], No. 42716/67. Heading F1J. The invention relates to a variable area jet propulsion nozzle comprising two series of flaps pivotally mounted at the end of the jet pipe, the arrangement being such that the flaps may assume a smooth internal contour for normal thrust or a corrugated shape for noise suppression operation. The nozzle assembly comprises a jet pipe 14 and an outer casing 3 which together define an annular duct 4 for flow of ambient air, ports 5 being formed in the casing 3 for inflow of further ambient air. A series of pivot pins 10 and 12 are disposed at the downstream end of the jet pipe, the pivots being disposed in the form of a polygon. A series of plain flaps 30 Fig. 4 are mounted on the pivots 12 and a series of hollow flaps 15 are mounted on the pivots 10 so that the flaps 30, 15 are disposed alternately around the nozzle. The flaps 30 are adjustable by means of an actuator 22 acting through an axially movable ring member 24 and linkage. The flaps 15 are adjustable by means of an actuator 11 acting through an axially movable ring member 13 and linkage. The flaps 15 are of rectangular cross-section and are curved in longitudinal section. Flange members 20 and 36 are secured at the side faces of the hollow flaps 15 (see Fig. 8) and the edges of the adjacent plain flaps 30 engage therebetween, the flanges diverging in the downstream direction. Assuming the actuators 22 are actuated to position the plain flaps 30, the actuators 11 are not actuated so that the flaps 15 are free to pivot outwardly about the pivotal axes 10 under the influence of the gaspressure within the nozzle so that the side flanges 36 abut against the ends of the flaps 30 which are in a fixed position. This is the position assumed for normal operation, the internal contour of the nozzle being smooth. Now if the actuators 11 are actuated to position the hollow flaps 15, the actuators 22 are not actuated so that the flaps 30 are free to pivot outwardly about the pivotal axes 12 under the influence of the gas-pressure within the nozzle so that the flaps 30 engage against the side flanges 20 of the hollow flaps 15 which are in a fixed position. The internal configuration of the nozzle is thus of corrugated form this being the position assumed for silenced operation of the nozzle. The hollow flaps 15 permit the inflow of ambient air. A thrust reverser assembly is indicated in Fig.1. In a further embodiment the hollow vanes are not curved in longitudinal section.