Patent GB-1197104-A (GB)
Title: A Silencer Device for an Ejector Type Jet Propulsion Nozzle
Inventor: RANVIER GASTON JEAN LOUIS
IPC: F02K1/50
Filed: 1968-06-25
Abstract: 1,197,104. Jet propulsion nozzles - silencing. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. June 25, 1968 [July 7, 1967; March 27, 1968], No.30234/68. Heading F1J. The invention relates to a jet propulsion nozzle in which scoops or baffles are provided to effect noise reduction, the scoops or baffles being movable between a projected operative position and a retracted non-operative position. The nozzle is of the ejector type comprising a main nozzle and a fairing of larger diameter than the nozzle disposed around the nozzle and extending downstream of the nozzle outlet. A series of scoops or baffles are disposed around the internal periphery of the fairing, the scoops or baffles being movable between an operative position in which they project into the jet stream and an inoperative position in which they are retracted into the fairing. The assembly shown in Figs. 1 and 2 comprises a main nozzle 2 and a fairing or shroud 3 disposed around the nozzle 2 and extending downstream thereof, the internal wall of the shroud being of convergentdivergent form 5, 7 with a throat 6. A series of openings is formed in the divergent surface 7 and a series of scoops or baffles 12 are associated with the openings, each baffle comprising a cranked lever 14 pivotally mounted at 15 on a fixed bracket 16 and carrying a plate member 13. Each lever is movable by means of an actuator 19 between a retracted position shown in full lines and an operative position 13a indicated in chain-dotted lines in which the plate 13 projects into the jet stream 11 discharging from the main nozzle. The plate deflects a portion of the jet stream outwardly where it interacts with the secondary air-flow being induced as indicated by arrow F, the resulting turbulent mixing of gas and air being effective to reduce noise. The operative position of the flaps is selected for aircraft take-off and landing while the retracted position is selected for normal flight. The downstream portion 8 of the shroud 3 comprises flaps pivotally mounted at the point 9. In Fig. 3 the plate member 23 of each baffle is of angle formation with a sharp leading edge portion 24 such that in the operative portion a shock wave is established at the leading edge. The inner wall 25 of the fairing is perforated and the space between the inner and outer walls of the fairing is packed with acoustic material such as steel wool. In Fig.6 each baffle 111 is supported by means of a pair of links 126, 127 pivotally mounted at points 118, 119 on the baffle and at points 124, 125 on a bracket secured to the fairing 3, the link 127 having an extended portion to which is connected an actuator 112. The baffle moves radially outwardly and axially downstream from the operative to the retracted position as indicated in Fig. 9. The baffle comprises a flat base portion 113 with two side walls 114 and a central rib portion 116 which is recessed at 117. The links 126, 127 engage with the pivot pins 118, 119 within the recess. The base portion is formed with a sharp leading edge 115 and the rib portion 116 is like-wise formed with a sharp leading edge. The baffle is formed with side walls 114 to prevent the gas stream deflected by the baffle from spilling laterally as it passes radially outwardly towards the air flow F. In a similar embodiment Fig. 17 (not shown), the base portion of the baffle is shaped to define a sharp leading edge 142 and a trailing edge surface 143 which in the operative position of the baffle is disposed parallel to the inner surface of the divergent portion 7 of the fairing so as to assist the gas flow. Means are provided whereby in the event of failure of a pivot point such as 118 Fig. 9, the baffle is automatically disconnected from the pivot point 119 so that the baffle is jettisoned to prevent it from blocking the jet stream. The link 127 is connected to the sides of the central web 116 by means of a pivot pin 129 the ends 129a, 129b of which are secured to the sides of the web 116 by pins 133. The central portion 135 of the pivot pin 129 is of arcuate form, see Fig. 13. An auxiliary pin 130 extends between the sides of the web 116 below the main pin 129 at a distance R therefrom. Assuming the forward pivot point 118 to have failed, the baffle 111 will rotate about the pivot pin 129 as indicated by the arrow m until the auxiliary pin 130 comes into contact with a recess 140 formed at the lower end of the link 127, Fig. 15 (not shown). The arcuate centre portion 135 of the pivot pin 129 will now be aligned with a corresponding arcuate opening 137 formed at the lower end of the link 127 so that the baffle will now rotate about the point 138 and the pivot pin 129 will disengage from the link 127, the baffle finally being jettisoned.