method for reducing a noise generated in the atmosphere visible vents and device for performing this process

摘要

868,072. Jet propulsion plant. LILLEY, G. M. May 12, 1958 [May 13, 1957], No. 15173/57. Class 110 (3). Apparatus for suppressing part of the noise emitted by a main jet issuing into the atmosphere comprises a main jet pipe and a number of auxiliary jet nozzles arranged around the periphery of the main jet, the longitudinal axes of the auxiliary nozzles being inclined to the axis of the main jet pipe and having also a component of motion substantially tangential to the outer periphery of the main jet and at rightangles to the axis of the main jet so that the auxiliary jets continue to penetrate the main jet up to a region substantially five diameters of the jet pipe downstream of the main jet pipe nozzle ending. Fig. 1 shows a jet pipe with coaxial outer and inner walls 1, 1A defining an annular duct 2 connected to a supply pipe 4. The downstream wall of the duct has a series of convergent nozzles 3 from which issue auxiliary jets 5 which penetrate the envelope 5 of the main jet. The ratio of the diameter of the main jet pipe ending to the diameter of each auxiliary nozzle ending may be 25: 1. The radially inward inclination and the tangential component of the auxiliary jets need not be the same for each jet. The auxiliary jets may be supplied with fluid tapped from the supply to the main jet or may be supplied from a separate container charged with a low-density gas such as helium. In the former case a compressor 9 may be incorporated between the tapping-point which, as shown in Fig. 4 may be the compressor 8 of an aircraft engine. Alternatively the exhaust of the turbine of an aircraft engine may be tapped. The auxiliary jets penetrate the main jet up to the point 5A. The auxiliary jets may be of convergent-divergent form and may incorporate swirl vanes 11 as in Fig. 6. Shutters 12 for cutting off the fluid supply may also be provided. According to the Provisional Specification, the noise suppressing apparatus could be applied to aircraft engines also equipped for thrust deflection or reversing. Specifications 766,985 and 766,986 are referred to.