GB849502A - Improvements in or relating to jet propulsion nozzles - Google Patents

Abstract

849,502. Jet propulsion nozzles. ROLLS-ROYCE Ltd. March 12, 1957 [March 1, 1957], No. 6988/57. Class 110 (3). A jet propulsion nozzle comprises a series of flaps pivoted at their upstream ends to swing towards and away from the nozzle axis and cooperate with stationary structure, adjacent flaps being adapted to swing in opposite senses to define in a first angular setting of the flaps a silenced nozzle having a corrugated contour or having a series of angularly spaced outlet apertures and to define in a second setting of the flaps a substantially frusto-conical nozzle or a nozzle having a corrugated contour whereof the radical depth of the corrugations is small compared with the depth in the first setting. A jet propulsion nozzle, Fig. 1, has six pairs of hollow members 11 fixed to the outlet end of the jet pipe to form a series of twelve spaces 12, 13. Two series of six flaps 14, 15, respectively are pivoted to the jet pipe. Each flap 14 has a circumferentially extending wall 14a and a pair of radially projecting side walls 14b which increase in depth in the downstream direction and co-operate in a gas sealing manner with the walls 11a of the members 11. The flaps 15 are arcuate plates with their edges in gas sealing engagement with the walls 11a. The flaps 14, 15 swing from a first setting shown to a second setting in which the walls 14a and plates 15 form a frusto-conical nozzle having a circular outlet. The flaps are caused to swing by a series of rams 17, Fig. 3, connected to a ring 18. The ring 18 carries a series of rollers 19, 20 which cooperate respectively with the walls 14a of the flaps 14 and the ramps 21 secured to the outside of the flaps 15. In this construction, the total outlet area of the nozzle in the silenced setting, Fig. 1, is greater than the area in the second setting. In a modification, Figs. 4 to 7 (not shown), all of the flaps are of similar construction to the flaps 14 already described. In this arrangement the flaps are moved from a position in which the depth of the corrugations is large to a position in which the corrugations are shallow. The areas of the nozzle in the two settings are substantially equal. The flaps are operated by rams connected to a ring which is connected by links to pins running in slots in the side walls of the flaps and in the wedge members. In another modification, Fig. 8, a tubular outer casing 35 has a series of inwardly projecting walls 36 each of which carries a pair of sealing elements 37, 38. Two sets of six pivoted flaps 39, 40 are also provided. The flaps are arranged to move from the first or silenced setting shown to a second setting in which the flaps abut the sealing elements 37, 38 and form a substantially plain convergent nozzle. In a further modification, Fig. 10 (not shown) the nozzle is convergent-divergent in the normal low thrust setting. In this arrangement the flaps are of different axial length and wedge shaped in the axial direction. The outer walls of the flaps form a continuation of the fairing enclosing the nozzle. By selecting the inward and outward movement of adjacent flaps to be of a differential nature, the relationship of the outlet areas of the nozzle in the first and second settings may be selected as desired.