GB851224A - Adjustable propulsion nozzles - Google Patents

Abstract

851,224. Jet propulsion nozzles. DE HAVILLAND ENGINE CO. Ltd. July 7, 1958 [July 17, 1957], No. 22693/57. Class 110 (3). A jet propulsion nozzle comprising a fixed tubular nozzle portion and a series of circumferentially spaced adjustable petals arranged to be moved so as to vary the effective cross-section of the nozzle has at least two of the petals independently supported and positioned solely by a control element rigidly secured to each petal and lying on its outer side, each control element being guided by operating apparatus positioned outside the gas stream passing through the nozzle. A jet propulsion nozzle comprises a fixed tubular nozzle portion 10 of cylindrical or frusto-conical form, a series of circumferentially spaced adjustable petals 11 downstream thereof and a fixed rearwardly extending portion 12 leading to an exhaust orifice 13. Each petal 11 is connected to a pair of webs 14 the opposite edges 15, 16 of which are engaged by guide rollers 20, 21 rotatably supported by the casing 12. The petals 11 may be moved from a position parallel to the wall 12 to a position in which the petal forms a substantial angle with the wall by a screw jack 22. The jacks may be synchronised by gearing. The jacks may be of the pneumatic or hydraulic type. Resilient strips 14 bear against the webs 14 to prevent the escape of hot gas. A series of holes 25 on a layer of mica or asbestos may be proved in the webs to reduce the heat conduction. Two cooling gas ducts 27, 28 are also provided. The duct 27 is arranged to supply cooling gas to the passages 32 in the petals when they are in the open position. When the petals are in the closed position, the gases which are bled from the turbine, pass into the exhaust nozzles through spaces 36. Cooling air from the compressor or from a forward facing air intake passes through the duct 28 and maintains the chamber 19 containing the nozzle operating mechanism cool. A layer 37 of heat resisting material may also be provided. In a modification, Fig. 5 (not shown) there is no internal cooling of the petals and the webs 14 are of opposite hand. The webs 14 may be guided by rollers which engage the surfaces of longitudinal slots formed in the webs. The holes 25 may be replaced by a layer of heat insulating material such as mica or asbestos. Specification 851,225 is referred to.