GB844249A - Improvements in or relating to jet propulsion nozzles - Google Patents

Abstract

844,249. Jet propulsion nozzles. ROLLSROYCE Ltd. Oct. 17, 1957 [Oct. 18, 1956], No. 31792/56. Class 110 (3). A jet propulsion nozzle comprising a cylindrical or frusto-conical outer surface and an inner surface defining for the flow of hot gas through the nozzle a duct having a series of circumferentially spaced axially extending gas paths leading from adjacent the inlet to the nozzle outlet, the gas paths being separated by inwardly projecting structures having at least side walls bounding the gas paths, the number of paths being selected to give a silencing effect in operation as compared with a tubular nozzle, is provided with a fairing structure affording an axially unobstructed path for the hot gas flowing from the nozzle and in axial alignment with the inwardly projecting structures, axially-extending outwardly facing channels which curve inwardly from their upstream ends to their downstream ends, the upstream ends being at such a radius from the nozzle axis as to receive air flowing rearwards outside the nozzle. This arrangement is said to reduce the drag of the nozzle. The jet propulsion nozzle, Fig. 1, comprises a frusto-conical outer wall 10 to which are attached a series of structures 11 of tetrahedron form which define a series of circumferentially spaced axially extending inwardly facing trough-like paths 12. A fairing structure, provided beyond the nozzle outlet 10b, comprises a series of sectors shaped structures 13, one aligned with each of the structures 11. Each structure 13 comprises a pair of radial walls 13a, a base wall 13b and an outer wall 13c. The wall 13c, which joins the radial walls 13a, has its upstream end radially level with the downstream end of the wall 10 and curves smoothly inwards to a point on the nozzle axis. The radial walls 13a project beyond the wall 13c to form an outwardly facing channel which conducts air flowing rearwardly outside the nozzle to the nozzle axis as indicated by the arrows 14. The radial walls 13a are extended upstream at 13d to facilitate attachment of the fairing structure to the nozzle. In a modification, Fig. 3 (not shown), the inwardly projecting structures do not extend to the nozzle axis and the fairing structure is formed integral with the nozzles. The radial walls of the fairing structure are formed by extending the side walls of the inwardly projecting structures. The invention may be applied to silenced convergent-divergent nozzles, silenced nozzles of by-pass engines and silenced nozzles provided with means for obtaining a reversed thrust for braking. Specifications 802,123, 811,455 and 823,949 are referred to.