GB913057A - Improvements in or relating to variable area jet propulsion nozzles - Google Patents

Abstract

913,057. Jet propulsion nozzles. ROLLSROYCE Ltd. June 9, 1959 [July 14, 1958], No. 22561/58. Addition to 849,333. Class 110 (3). The invention comprises improvements in or modifications of jet propulsion nozzles as described and claimed in the parent Specification in which a tubular wall member defines a gas passage having an outlet at one end and has at least one flap member which is adjustable by mechanical linkage between a first position in which it projects into the gas stream upstream of the outlet to define a first effective area of the nozzle less than the area of the outlet of the tubular 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 restricts a substantial flow of gas round their sides. In one modification, the tubular wall has a series of angularly-spaced axially extending structures which over at least the peripheral portion of the gas passage define a number of gas flow channels and the or each flap member extends between a pair of structures and in the first position the lateral edges of the flap members co-operate with adjacent circumferentially-facing webs of the pair of structures to reduce the outlet area of the channel between them, parts of the axially extending structure forming the gas sealing structure. In another modification, the or each flap member is pivoted by its upstream end to the tubular wall member and has pivoted to its downstream end one end of a secondary flap member the other end of which is connected to power means by which movement of the flap is effected, the secondary flap member facing in the first position a downstream facing wall extending outwardly from the downstream end. The nozzle comprises a tubular wall 10 having a series of angularly-spaced hollow axiallyextending structures 11 which divide the peripheral portion of the gas passage into a series of channels 12. The structures 11 are of such a shape that the cross-section of the gas passage decreases in the direction of gas flow. To reduce the outlet area of the nozzle a pair of flap arrangements 13 are provided in a diametrically opposite pair of channels 12. Each flap arrangement comprises a main flap 14 pivoted to the tubular wall member 10 to the downstream end of which is pivoted a secondary flap 17 the other end of which carries a pair of rollers 20 which engage axial tracks 21 formed on the surface of a member 22 secured to a box structure 23. The rollers 20 are mounted on a pin 19 which is connected by a link 24 to a main piston 25. The link 24 is provided with a hooked lug 30 which engages a channel 31 to prevent inward movement of the flaps when the gas pressure in the tubular wall 10 is low or zero. The box structure 23 has a slot 32 which connects the interior of the box on the downstream side of the flap to the atmosphere. When the flap 14 is in the nozzle-restricting position gas can flow as shown at 33 into the structure 23 on the upstream side of the flap 17 and so tend to maintain it in position. If the pressure-fluid supply to the ram 25 should fail, the gas load acting to the left on the piston 25 due to the gas pressure in the box structure 23 on the upstream side of the flaps 17 holds the parts in the full-line position.