GB874496A - Jet propulsion nozzle noise suppression means and thrust reverser - Google Patents

Abstract

874,496. Reversing thrust on jet propelled aircraft. WESTLEY, R. Aug.. 27, 1958 [Aug. 30, 1957], No. 27544/58. Class 4. [Also in Group XXVI] A jet propulsion nozzle is provided with means for reducing noise created by the gas stream issuing therethrough, the nozzle being provided with a number of elements which are pivotable to vary the peripheral configuration of the nozzle, without substantial change in effective nozzle outlet area, from a noise reducing position in which the gas stream immediately downstream of the nozzle has a corrugated crosssectional periphery, to a less-effective noise reducing position. The propulsion nozzle shown in Fig. 1 is of generally frusto-conical form and is provided with a plurality of pairs of parallel,. substantially radially-extending walls 21, 21 and 22, 22, the walls 22 having greater radial extent than the walls 21. Flap members 25, 26 are disposed between the pairs of walls 21, 21 and 22, 22 respectively, the flap members being pivotally mounted at their upstream ends 23, 24, the flaps 25 swinging between stops 27, 29 on the walls 21 and the flaps 26 swinging between stops 28, 30 on the walls 22. The nozzle is shown in the normal flight position, the outlet ends of the flap members 25, 26 being disposed. at substantially equal radii. In the noise reduction position, the flaps 25 are swung inwardly to abut against the stops 29 and the flaps 26 are swung outwardly to abut against the stops 28, the jet stream then issuing from the nozzle with a corrugated periphery, the change in shape of the nozzle outlet producing no substantial change in the cross-sectional area thereof. The propulsion nozzle shown in Fig. 3 is adapted for both noise reduction and for thrust reversal. The nozzle is of cylindrical form being formed with corrugations 42 around the periphery thereof, and is divided longitudinally at 43 to provide two halves 44, 45 which are pivotally mounted at 47 on supporting arms 46. The nozzle is also divided transversely at 48 through the pivots 47 to provide two clamshell like members 49, 50. The clam-shell members 49, 50 are operable by linkage F, G, J to pivot about point 47 so that the edges 58, 57 thereof move to the positions 51, 52, this being the noise reduction position. For thrust reversal, the two half nozzles 44, 45 including the clamshells 50, 49 are moved by the linkages H, I, K and F. G, J until the edges 57, 58 thereof abut on the axis at 59, the leading edges 61, 60 of the half nozzles then being at the positions indicated by broken lines so that gases discharging from the nozzle at 62 are diverted forwardly as indicated by arrows 63, 64. The apparatus shown in Fig. 1 may be adapted also for use as a thrust reversal nozzle, the pairs of side walls 21, 21 and 22, 22 being hingedly connected at their forward ends to fixed nozzle structure and a central bullet member being provided. In the thrust reversal position the pairs of side walls are swung about their pivots until they abut against the bullet member. The pivoted flap members 25, 26 are then disconnected from the pivots at their forward ends and are connected to pivots on the side walls 21, 21 and 22, 22 at their rearward ends, the flaps then being swung outwardly about their rearward pivots whereby a portion of the jet stream issuing through the nozzle impinges against the flaps and is diverted forwardly. A mechanism suitable for this purpose is indicated in Fig. 8A, one of the radially-extending side walls being shown at 71 and the flap associated therewith at 73. The flap 73 is connected at its upstream end to a shaft T which is supported in half bearings U. A fork member H is slidably mounted on the flap in brackets G<SP>1</SP>, H<SP>1</SP>, the ends of the fork engaging with brackets M. The opposite end of the fork H is of T-shape, the outer ends of the T passing through slots F<SP>1</SP> in the side walls 71. A pivot R is disposed at the lower edge of the slot F<SP>1</SP> which is engaged by the outer end of the T-piece. A rod K is connected to the shaft T and a link P is connected between the rod K and the fork H. A return spring Q is connected to the rod K. Movement of the operating rod L to the right depresses the flap 73 and causes the fork H to slide out of engagement with the brackets M and the T- shaped end of the fork engages with the pivot R. The flap 73 is now free at its upstream end to pivot about R and to be placed by further movement of the operating rod L into the thrust reversing position. In another embodiment, Figs. 12 and 13, the nose of the internal bullet 140 is provided with a series of wedge-shaped segmental pieces 141 pivotally mounted at 142 at their upstream ends, the pieces 141 being separated by fixed pieces. The wedge pieces 141 are swung outwardly as shown in Fig. 13 to the noise reduction position. In place of wedge members, retractable vanes may be provided, the vanes deflecting the gas stream alternately towards and away from the axis. The outer wall of the nozzle in Fig. 12 is provided with pivoted flaps 146, 147 which are separated by fixed members 150. The flaps 146 swing outwardly and the flaps 147 swing inwardly so as to afford a corrugated periphery at the nozzle outlet. The nozzle shown in Figs. 12 and 13 may be adapted to produce thrust reversal, the bullet in this case projecting beyond the end of the nozzle 145, and thrust reversal retractable flaps being mounted on the bullet 140 upstream of and between the wedge shaped segments 141.