GB788359A - Discharge nozzles for propulsive jets - Google Patents

Abstract

788,359. Jet propulsion plant. POWER JETS (RESEARCH & DEVELOPMENT), Ltd. Nov. 17, 1955 [Nov. 26, 1954], No. 34423/54. Class 110 (3). A jet propulsion discharge nozzle comprises at least one wall portion pivotable about an axis extending transversely to the direction of fluid flow at a region upstream of the downstream end of the wall portion to vary the nozzle configuration, the pivot attachment being movable transversely to the fluid stream independently of pivotal movement of the wall portion to vary the flow area of the nozzle. The jet nozzle shown in Figs. 1 and 2 comprises two movable wall portions 5 shaped as shown to provide a convergent-divergent nozzle and pivotally mounted between side walls 3 by means of trunnions 8 which are situated in the region of the throat 7 of the nozzle. The wall portions 5 are pivotable in unison to vary the divergency and the discharge area by means of hydraulic jacks 18, each jack having a. pin 19 which engages the slots of intersecting slotted levers 16 fixed to the adjacent trunnions 8. The trunnions 8 are journalled in eccentric bushes 9 which are geared together by means of integral gear wheels 10 so as to be rotatable in opposite directions to displace the trunnions laterally, thereby varying the cross-sectional area of the throat 7. Rotation of the bushes 9 is effected by an hydraulic jack 15 which acts upon a crossbar 12 joining a pair of cranks 11 integral with the upper gear wheels 10. Leakage between each wall portion 5 and the preceding duct 1 is prevented by flexible fingers 22 which bear upon a part-spherical pad 20, and flexible fingers 24 which bear upon the upstream edge of the wall portion. Each finger 22 has an extension 23, Fig. 5, to overlap an adjacent finger; similar overlapping extensions 25 are provided on the fingers 24. Sealing between the wall portions 5 and the side walls 3 is provided by longitudinal flanges 6, but longitudinal channels each accommodating a sealing pad could be provided. In the alternative construction shown in Figs. 6 and 7 each wall portion 5 is pivotable about a spindle 30 by means of paired pistons 44, at each side of the wall portion, operating in a common cylinder 45 which also houses the correspondirg paired pistons 44 of the other wall portion. The pistons 44 act through conecting rods 43 and a block 42 which is pivoted on a trunnion 41 attached to the wall portion 5. The wall portions 5 co-operate with the preceding duct 1 to form, in one position, a convergent-divergent flow path. The spindles 30 are journalled in eccentric bushes 32 which can be rotated to move the wall portions 5 towards or away from one another. An actuating lever 40 is connected to the upper bushes 32 by pulleys and uncrossed belts 38 and to the lower bushes 32 by pulleys and crossed belts 39. In both embodiments the operation of the pivoting means may be controlled to increase the nozzle divergency in accordance with increase in the ratio between the pressure in duct 1 and the ambient pressure, or the ambient Mach number relative to the aircraft. Operation of the hydraulic jack 15 or the lever 40 may be related to fuel supply to a reheat burner upstream of the nozzle so that the nozzle area increases as the fuel supply increases.