Patent GB-766986-A (GB)
Title: Noise suppressing nozzles for aircraft jet propulsion engines
IPC: F02K1/46
Filed: 1952-07-25
Abstract: 766,986. Exhaust-silencers. LILLEY, G. M., WESTLEY, R. and YOUNG, A. D. July 21, 1953 [July 25, 1952], No. 19123/55. Divided out of 766,985. Class 7 (2). [Also in Group XXVI] are positioned on the upstream side of the ring (c) two diametrically opposite projections 4, Fig. 14, which extend inwardly toward the axis of the jet are arranged on the variable area nozzle 1, and " eyelid " shutters 26 pivoted in bearings 28 are provided with inwardly inclined projections 27, (d), Fig. 15 (not shown), a device for attaching to a jet pipe comprises a split ring having projections, some of which are inwardly inclined. In another modification, Fig. 17, a number of projections 30 are pivoted about their mid-points on a ring 31 supported independently of the jet nozzle 1, and alternate projections are connected to controlling mechanisms 33, 34 movable to the right or left as seen in the figure so that the respective projections 30 are caused to become inclined towards or away from the axis of the jet ; alternatively, all the projections have their downstream ends inclined inwardly towards the axis of the jet. In other modifications, (a) Fig. 18 (not shown), a number of apertures around the perimeter of the convergent part of the nozzle allow the boundary layer of the jet to escape and mix with the atmosphere, a variable exit area being achieved by slidable closing elements preferably mounted on the inside wall of a nacelle surrounding the jet pipe, (b), Fig. 19 (not shown), the boundary layer of the jet passes outwardly through a finely perforated or gauze wall over which slides an obturator element. In still further modifications, (a), Fig. 20 (not shown), a supersonic nozzle of convergentdivergent construction has an exit equipped with projections of the kind shown in Fig. 1, (b), Fig. 21 (not shown), the convergent portion of a nozzle protrudes into a divergent extension piece, a gap being left between the perimeter of the nozzle exit and the wall of the extension piece and in the plane of the exit, and (c), the extension piece 45, Fig. 22, has a 'double wall, the inner wall 48 being perforated and the space between the walls being filled with sound-insulating material; projections 4 are provided at the edge 47 of the piece 45 or the nozzle exit 3, or both. The silencing means may be applied to aircraft rocket, ramjet or gas turbine engines, propulsive jets for vehicles or ships, and steam and air jets. According to the Provisional Specification, the projections may be angularly adjustable or retractable, or both, and used as a device for altering the jet exit area. Also, the projections may have combined axial and angular movement under the control of electric, hydraulic or pneumatic actuators. A noise suppressing nozzle for the gas stream of an aircraft jet-propulsion engine is of fixed configuration, shaped at the upstream end 2 thereof in the same manner as the jet pipe 1, and peripherally corrugated. The corrugations continuously deepen in the downstream direction and up to the plane of the nozzle exit. As shown, there are six complete corrugations, the crests 3 and troughs 4 of which are respectively inclined away from and towards the axis of the nozzle ; the total depth of a single corrugation at the downstream end of the nozzle is of the same order as the radius of the jet pipe, and of the upstream end of the nozzle. The nozzle may be fabricated integrally with the jet pipe.