GB750307A - Improvements relating to variable nozzles for gas-turbine jet propulsion engines - Google Patents

Abstract

750,307. Jet-propulsion plant. ROLLS-ROYCE, Ltd. Feb. 11, 1954 [Feb. 16, 1953], No. 4332/53. Class 110(3) A gas-turbine jet-propulsion engine having a jet pipe 11 with a convergent portion 17 at its downstream end, and a casing 34 surrounding the jet pipe in spaced relation thereto, is combined with a nozzle arrangement comprising a plurality of nozzle elements 14 which are pivoted adjacent the downstream end of the jet pipe and are adapted to be movable between a first position in which they define the minimum area of the nozzle and a second position in which, together with the convergent portion 17, they define a convergent/divergent nozzle of which the throat lies substantially in a plane upstream of the downstream ends of the nozzle elements, and a plurality of flaps 36 which are spaced externally of the nozzle elements and are connected to the latter to move therewith, the flaps being so arranged as to maintain a substantial continuity of surface with the casing 34. As shown, each nozzle element consists of a curved portion 14a, a contiguous curved portion 14b of greater diameter overlying the portion 14a of the adjacent element, and an edge flange 14c provided with a sealing strip 14d which rubs against the portion 14a of the adjacent element. Each element is pivoted by a pin 26 to a circular bracket 27 fixed to the end of the convergent portion 17. Rams 30, mounted on the casing 34, have piston rods 30a connected to a ring 31 slidable on the brackets 27, the ring being connected by respective links 32 to arms 33 extending from the elements, whereby the latter may be moved from the convergent position for subsonic flight, to the divergent position for supersonic flight under conditions of re-heat combustion in the jet pipe. The flaps 36, which overlap in the same manner as the elements 14, and are connected to the latter by links 37, are pivoted to the downstream end of the casing 34. In a modification the nozzle arrangement comprises a pair of fixed and spaced side walls, and a pair of adjustable elements extending between the side walls and forming therewith a substantially rectangular outlet. The upstream ends of the elements are pivoted to the downstream end of the convergent portion of the jet pipe, and the downstream ends of the elements are pivoted to fairing flaps, the upstream ends of which are slidably connected to the casing surrounding the jet pipe. In a further modification the pair of elements defining the rectangular outlet are formed as double-skinned structures, the outer walls of which constitute the fairing flaps. It is stated that means may be provided for varying the throat area at which sonic velocity is reached in conditions of supersonic flight, and said means may consist either of a conical bullet arranged to be movable axially relative to the jet pipe, or means adapted to vary the diameter of the pitch circle of the pivots of the nozzle elements, for which latter purpose the nozzle elements may be pivoted at their upstream ends to the downstream ends of axially-extending elements which are in turn pivoted at their upstream ends to fixed structure.