GB896484A - Improvements in "adjustable converging-diverging jet propulsion nozzle" - Google Patents

Abstract

896,484. Jet propulsion nozzles. GENERAL ELECTRIC CO. Dec, 16, 1960, No. 43361/60. Class 110 (3). In a jet propulsion nozzle comprising a primary section for receiving the working fluid from the engine and formed successively in a downstream direction with a convergent portion, a throat and a divergent portion terminating in a primary discharge orifice and a fixed secondary nozzle section circumferentially spaced about the primary nozzle section to form a passage for the introduction of secondary air into the nozzle, the primary nozzle section is adjustable to vary the throat area and discharge orifice thereof between a position in which the working fluid is exhausted to atmosphere directly from the primary discharge orifice to a position in which the working fluid is exhausted to atmosphere through the secondary nozzle section from the primary nozzle orifice, the primary nozzle section and the secondary nozzle section co-operating in the range of positions to vary automatically the effective area for the flow of working fluid from the exhaust nozzle, in accordance with the ratio of working fluid pressure to atmospheric pressure. The jet propulsion nozzle, Fig. 1, comprises an adjustable primary nozzle section 1 and a fixed secondary nozzle section 2, which define a passage for the flow of working fluid from a jet propulsion engine as shown by the black arrows. The exhaust nozzle structure is supported by the exhaust collector 3 by a plurality of brackets 4. A cylindrical duct 5 carries brackets 6 which are connected by fastenings 9 passing through openings 8 and elliptical openings 7 in the brackets 4, 6. The secondary nozzle section 2 is formed as a convergent-divergent nozzle with a throat 12 and co-operates with the outer surfaces of the primary nozzle section 1 to form an adjustable ejector nozzle passage 18 which is supplied with secondary air, designated by white arrows, from any suitable source such as the intake end of the associated jet propulsion engine. The primary nozzle section is formed of an annularly disposed set of flaps 20, 21, Fig. 3, each of which are formed with a convergent portion, a throat and a divergent portion. Each flap also carries a track element 28, 55 which co-operate with rollers 70, 80 carried by the duct 5 by the brackets 75, 85. The flaps are connected to a driving ring 90 which is moved axially by a number of driving motors (not shown). The driving ring 90 slides on elements 112 attached to the engine casing 125 and exhaust collector 3. The flaps 20 are rigid and are reinforced by a stiffening-plate 31 formed with ribs 33. The inner flaps 21 are made flexible so that the gas pressure forms a positive sealing action between adjacent flaps. The flaps 21 are held in relation to the flaps 20 by tongues 54. A seal 130 prevents leakage of working fluid around the exhaust collector 3. As can be seen from Fig. 10, movement of the primary nozzle section varies the area of the annular passage 18 which determines the point of breakaway of the flow in the divergent section of the nozzle and thus the effective outlet area.