GB844179A - Improvements in or relating to nozzles for jet propulsion purposes - Google Patents

Abstract

844,179. Jet propulsion nozzles. ROLLSROYCE Ltd. Oct. 8, 1958 [Oct. 16, 1957], No. 32391/57. Class 110 (3). In a jet propulsion nozzle comprising a plurality of passage-defining means each effectively forming a gas path of rectangular crosssection leading to an outlet which is effectively of rectangular section in a plane at right angles to the direction of gas flow through the nozzle, the shorter dimension of each outlet is small compared with the longer dimension, the longer dimensions of the outlets are parallel, the outlets are spaced apart in the direction of the shorter dimensions of the outlets to permit the flow of air between them and fairings, which merge smoothly into a pipe portion at the upstream end of the nozzle and converge in the downstream direction, are provided to separate the passage defining means. The nozzle, Fig. 3, is formed by four passage defining means 16, 17, 18, 19 fed with exhaust gases by a jet pipe 14. Each passage has a pair of main walls 20 which converge in the direction of gas flow and top and bottom walls 21 which diverge in the direction of gas flow and have at the outlet dimensions transverse to this direction substantially smaller than the corresponding dimensions of the main walls 20. The cross-sections of the passages have their shorter dimensions extending in the direction in which the passagedefining means are spaced and their longer dimensions parallel. The thickness ratio of the nozzle i.e. the ratio of the diameter of the largest circle inscribable in the outlet from any one passage to the outlet diameter of a plain conical nozzle of equivalent effective area, is of the order of a fifth or less. Fairings 22 between the passages 16, 17, 18, 19 converge rearwardly to form air flow channels of gradually increasing depth. To avoid structural and resonance difficulties, the portions of the walls 20 adjacent the outlet may be formed with a series of shallow scallops. The walls are supported by ties 24 which may extend upstream from the outlet as shown or throughout the length of the passage. The area ratio, i.e. the square of the ratio of the diameter of the escribed circle Dm, Fig. 4, is the diameter Dj of a conical nozzle of the same outlet area should be as high as possible. In a modification, the passage defining means are formed by layers of contacting imperforate tubes which terminate in a rectangular or circular outlet of reduced area as compared with the cross-section area of the tube. Each passage is formed by a layer of tubes. In another modification is formed by two layers of tubes.