GB1438677A - Variable-geometry nozzle with a muffler or silencer effect for a jet engine - Google Patents

Abstract

1438677 Jet propulsion nozzles - variable geometry SOC NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION 9 July 1973 32632/73 Heading F1J The invention relates to a variable-geometry nozzle for a jet engine, the nozzle comprising a fixed structure, flaps adjustable in position with reference to the fixed structure, and control means for adjusting the position of the flaps. In a first embodiment the nozzle comprises a fixed structure 2 defining a jet pipe through which streams of gases F1 and air F2 flow. A series of brackets 6 are secured to the structure 2 and four C-shaped members 101, 102, 103, 104 are pivotally mounted on the brackets, the upper member 101 for example being pivotally mounted on brackets 6 about a horizontal axis A1-A1 and a side member 102 being pivotally mounted about a vertical axis A2-A2. The members are pivotally movable by means of actuators V1, V2, V3, V4. A main flap member 201a, 202a, 203a, 204a is rigidly secured to the centre portion of each member 101, 102, 103, 104 by means of bolts 8, and side flaps such as 201b, 201c are pivotally mounted at each side of each of the main flaps such as 201a, the adjacent side flaps such as 201b, 204c engaging in overlapping manner. The flaps may be moved so that the outlet area is either of horizontal rectangular form, of vertical rectangular form, of small area square form or of large area square form. When the actuator V 1 for example is actuated the top main flap 201a is swung about the pivotal axis A1-A1 to the position shown in Fig. 2 thus forming a tertiary air inlet 11 for air-flow F3, this being the position of the flaps 201a, 203a in the horizontal rectangular nozzle form and in the small area square nozzle form. The flaps 201a, 203a are in the Fig. 1 position for the vertical rectangular and large area square nozzle forms. In Fig. 7 (not shown) each main flap such as 201a is not flat as in the first embodiment, but is of flattened V-section so that the nozzle approaches more closely a circular form; also the pivotal axes such as B1, C4 of adjacent side flaps 201b, 204c are inclined at an angle less than 90 degrees; the axes meet at the same point 0 as that in which the Axes A 1 -A 1 and A 4 -A 4 meet. In Fig. 8 (not shown), there are six C-shaped members such as 101 and six main flaps such as 201a and of course six pivotal axes such as A 1 -A 1 ; thus the nozzle is of polygonal form. In a further embodiment Figs. 13-16 (not shown) the nozzle comprises only two C-shaped members 51, 52 which are pivotally mounted on parallel axes C 1 -C 1 and C 2 -C 2 . Two flap members 61, 62 and 63, 64 are pivotally mounted on each C-shaped member and four actuating jacks are provided whereby the nozzle may be adjusted to any of the four positions described with reference to the first embodiment.