GB884587A - Improvements in jet propulsion nozzles - Google Patents

Abstract

884,587. Jet propulsion plant. GENERAL ELECTRIC CO. April 18, 1958, No. 12452/58. Class 110 (3). A convergent-divergent nozzle for the jet pipe of a jet propulsion engine comprises a variable area convergent nozzle for subsonic gas flow combined with an air wall provided by means of an exterior passage surrounding the convergent nozzle and itself terminating in another variable area nozzle, the air wall defining an adjustable divergent passage for supersonic flow. The convergent portion of the nozzle is defined by adjustable nozzle flaps 11 hinged at 16 to the rear end of the tail pipe 17, while the boundary of the divergent portion is formed by secondary air flowing through an annular passage 15 between the tail pipe and an outer casing and emerging between the flaps 11 and the adjustable shroud flaps 12 which are hinged at 18 to a tubular shroud 19 which is itself axially slidable within the outer casing 21. Hydraulic actuators 22, 31 vary the angularity of the nozzle flaps 11 and the shroud flaps 12 respectively while an hydraulic actuator 39 varies the axial position of the shroud 19 in the outer casing 15. A control 46 combines measurements of rotor speed, throttle setting, compressor inlet temperature and pressure and turbine discharge temperature and pressure and controls the actuators accordingly. The flow of secondary air created by the ejector action of the nozzle may be used to cool engine accessories placed in the passage 15. In another embodiment (Fig. 4, not shown) a single shroud displacing actuator is used, the nozzle flaps and the shroud flaps being linked mechanically to each other and the outer casing 21 so as to move angularly as the axial position of the shroud 19 in the outer casing is varied. In a further embodiment lacking the axial adjustment the shroud flaps are hinged directly to the outer easing and are mechanically linked to the nozzle flaps, a single controller varying the angularity of the flaps.