Patent GB-823949-A (GB)
Title: Improvements in or relating to jet nozzles for reaction-propulsion purposes
Inventor: KEEN JOHN MICHAEL STORER
IPC: F02K1/48
Filed: 1956-02-27
Abstract: 823,949. Jet-propulsion nozzles. ROLLSROYCE Ltd. Feb. 19, 1957 [Feb. 27, 1956], No. 6088/56. Class 110 (3). A jet - propulsion nozzle comprises a tubular casing 10cmber having on its inner surface a series of inwardly - projecting axially extending portions forming a series of circumferentially spaced channels for the propulsive gas extending from adjacent an inlet to the nozzle at least to the nozzle throat, the inwardly projecting portions being formed by a series of separate structures attached to the inner surface of the tubular easing member. A convergent nozzle, Fig. 1, comprises a sheet metal cylindrical casing 10 and a series of box-like sheet metal pieces 11 which form with the casing a series of trough-like channels 12 having a decreasing total cross-sectional area in the direction of flow to form a throat at the outlet of the jet nozzle. Each box-like piece 11, Fig. 4, comprises a pair of triangular side walls 13 and a from adjacent an inlet to the nozzle at least to the nozzle throat, the inwardly projecting portions being formed by a series of separate structures attached to the inner surface of the tubular casing member. A convergent nozzle, Fig. 1, comprises a sheet metal cylindrical casing 10 and a series of box-like sheet metal pieces 11 which form with the casing a series of trough-like channels 12 having a decreasing total cross-sectional area in the direction of flow to form a throat at the outlet of the jet nozzle. Each box-like piece 11, Fig. 4, comprises a pair of triangular side walls 13 and a inwardly facing wall 14 which are welded by flanges 15, 16 to the casing 10. The walls 13, 14 project beyond the lip 10a of the nozzle and each of the box-like pieces 11 is closed at its downstream end by an end wall 17. The angle subtended at the nozzle axis between the side walls 13 of each piece 11 is substantially equal to that between adjacent side walls of adjacent pieces 11. The cross-sectional area of the box-pieces 11 increases in the direction of gas flow so that the area of gas flow correspondingly decreases. The number of troughs determine the frequency range in which maximum noise-level reduction is obtained and is preferably about six. To reduce the aerodynamic drag of the nozzle elbow pipes 19 leading from ports in the casing 10 to ports in the end wall 17 are provided through which air is drawn into the wakes of the pieces 11 by the flow of gas through the nozzle. To adjust the outlet area of the nozzle, wedge-shaped trimmer member 21 may be attached to the side walls 13. Key-hole slots on the trimmer members engage buttons 23 on each side wall 13 and retained thereon by studs 26 screwed into bushes on the end wall 17. To discharge fuel from the engine drain sump an ejector body 28, Fig. 3, is mounted on an internal stiffening wall 29 of one of the pieces 11 and has connected to it three tubes. One tube 30 supplies gas from the nozzle to the ejector 28 which discharges through a second tube 31. A third tube 32 is connected to the fuel collector sump. Metal bellows 36 seal the hole 37 in the wall of the pipe 19 through which the tube 31 passes. Drain holes may be provided in each box-like piece 11 at its lowest point to drain away any fuel collecting in them. Holes 38 are provided in the walls 14 to balance the gas pressures on each side of the wall. The invention may be applied to a convergentdivergent nozzle. The side walls of the pieces 11 may be curved instead of straight as shown. The outlet area of the nozzle may also be trimmed by blockage pieces formed of strip material retained along their axial edges in flanges attached to the peripheral wall 10. Reference has been directed by the Comptroller to Specification 768,553.