Patent GB-849333-A (GB)
Title: Improvements in or relating to variable-area jet nozzles for jet propulsion purposes
Inventor: KEEN JOHN MICHAEL STORER
IPC: F02K1/12
Filed: 1956-03-16
Abstract: 849,333. Jet-propulsion nozzles. ROLLSROYCE Ltd. March 12, 1957 [March 16, 1956], No. 8389/56. Class 110 (3). A jet - propulsion nozzle comprises a tubular wall member defining a gas passage and having an outlet at one end and at least one flap member which is adjustable by a mechanical linkage between a first position in which it projects into the gas passage upstream of the outlet to define a first effective area of the nozzle less than the area of the outlet of the tubular wall member and a second position in which it is retracted and the nozzle has a second effective area greater than the first, the total peripheral extent of the flap members being a minor proportion of the total peripheral extent of the nozzle outlet, and structure associated with the flap member or members to restrict the substantial flow of gas around the sides thereof. The variable area jet propulsion nozzle, Fig. 2, comprises a frusto-conical wall 10, a pair of flap members 11, one only of which is shown, and power means to move the members 11. The wall 10 has cut-outs 12, which accommodate the members 11 when they are in the retracted position, covered by a blister formed by sheetmetal pieces 13a, 13b, 15. The flap members 11 are formed in two parts. The first part comprises a sheet-metal plate 17 secured to a central girder member 16 pivoted on a bracket 22 secured to the wall 13a of the blister. A flanged member forms the walls 18a, 18b, 18c round the plate 17. The second part is U-shaped in plan and comprises top and bottom skins 24a, 24b, side walls 24c and forward and rear walls 24e, 24d. This part is also pivoted on the bracket 22. The flap members 11 are actuated by hydraulic rams mounted on the front wall of the blister. Each ram comprises a cylinder 30 housing a piston 31 connected through a piston-rod 32 and cross-head 34 to links 35, 37 connected at their opposite ends to the two parts of the flap members. The arrangement is such that movement of the piston 31 from one stop 40 to a second stop 42 moves the first part of the flap-member 11 through a greater angle than the second part so that in the retracted position the second part is contained in the well formed by the flanges 18a, 18b, 18c. In the extended position shown the walls 24a, 24c of the second part form extensions of the walls 18a, 18b of the first part. Forming the flap in two parts reduces the size of the blister. In a modification, Figs. 6, 7 and 8 (not shown), the second part is actuated by a link pivoted to the links connecting the first part to the crosshead. In another modification, Fig. 9, the tubular member 90 has six closed structures 91 forming a series of angularly-spaced channels 92. To vary the outlet area, a pair of diametrically-opposite channels 92 are provided with flap members 94 of the type already described. In a further modification the side walls 18a, 24c are replaced by parallel triangular walls attached to the tubular member 10 along the side edges of the cut-out 12. In a modification of this arrangement the side walls 18a are retained and provided with sealing-members which slide over the parallel walls. In yet another modification the parallel side walls are attached to the plate 17. The flap members may be pressure-balanced by allowing gas to pass through small clearances around their edges or seals may be provided around their edges in which case the blisters 13a, 13b, 15 would not be required. An arrangement having six flapmembers is also described. Specifications 768,553 and 849,334 are referred to.